1 
 
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WILSON'S Photographics. 
 
 (Ask for CHAUTAUQUA EDITION.) 
 
 The best photographic lesson-book, by Edward L. Wilson, editor of Wilson's 
 Photographic Magazine, Photographic Mosaics, etc. The author believes it to 
 be the best ellbrt he has ever made, and bogs leave to call attention to a few 
 of its peculiar advantages as, a standard work for all workers in photography . 
 
 A. Treatment of the Subject; B. The Needful Apparatus; C. The Objec- 
 tive Or Lens ; D. The Dark-room ; E. Preparation of the Glass ; F. Chemicals 
 and Solutions; G. The Manipulations: H. Manipulatory Miseries; I. Re- 
 touching the Negative ; J. The Glass Studio ; K. Accessories and Light : L. 
 Managing the Model ; M. Printing on Albumen Paper; N. Printing on Plain 
 Paper; O. General Remarks on Printing; P. Printing on Various Surfaces ; 
 Q. Printing Perplexities ; R. Art in Printing; S. Mounting and Finishing; 
 T. Photography Outside; U. Bromo-gelatine Emulsion Work; V. Vogers 
 Collodion Emulsion ; W. Enlargements and Lantern Slides; X. Phototypes, 
 Platinotypes, and Collodion Transfers ; Y. Wastes and their Worth ; Z. Met- 
 rical Measuring ; &. Concluding Confab ; Index (six pages). 
 
 It is believed that this is the most valuable work ever offered to the work- 
 ing photographer. It contains 352 pages. More than 100 illustrations. Com- 
 panion to Quarter Century, 
 
 $4.00 POST-PAID $4.00. 
 
 It is printed on fine white paper made especially for it. The author has 
 received a thousand testimonials. For the beginner, for the amateur, for the 
 photographic worker, it is believed to be the most complete. 
 
 EDWARD L. WILSON, 853 Broadway, New York. 
 
 Wl LSOIM'S 
 
 QUARTER CENTURY IN PHOTOGRAPHY 
 
 Contents: — 1. The History of Photography ; 2. The Theory of Photography ; 
 3. Light ; 4. The Camera ; 5. About Lenses ; 6. The Diaphragm, or Stop ; 7. 
 Glass-house Construction ; 8. Under the Skylight ; 9. The Application of Art 
 Principles ; 10. Outdoor Operations ; 11. Exposure, "or the Question of Time ; 
 12. Concerning Chemicals ; 13. Dark-room Contrivances ; 14. Negative Making, 
 Wet ; 15. Negative Making, Dry ; 16. Negative Making, Paper and Film ; 17. 
 Retouching and Doctoring the Negative ; 18. Printing on Albumenized Paper ; 
 19. Printing Drawbacks and Defects— Causes and Remedies ; 20. Printing-room 
 Particulars ; 21. Peculiar Printing Processes ; 22. Color-sensitive Photography 
 — Isochromatic— Orthochromatic ; 23. Photo-engraving and Pictorial Illus- 
 trations ; 24. Lantern Slides and Transparencies. 
 
 For the modern student this is the best book. The thorough student needs 
 both. Except for special departments of work, no other books are needed. 
 
 Price, $4.00 Post-paid. 
 
 The arrangement of Quarter Century is exceptional in one respect that greatly 
 increases its value for general work : The main text is supplemented by fo;>t 
 notes in smaller type, comprising quotations from all our leading writers, and 
 in many cases containing original methods not yet generally known to 
 photographers. Its readers will be more than repaid by a close comparison of 
 the methods presented.— Ir on. 
 
 The great test of such a book comes not with the reading, but with the use. 
 The clear style, the straightforward directness of every line, the exactness of 
 all dimensions given, and the fulness of all treatments, give assurance that 
 this work is for use. We do not see how any photographer, or any learner of 
 this wonderful art, can attain the most complete and perfect mastery of the 
 subject without this work. It is a complete thesaurus, and one not soon to be 
 supplanted by a better.— Dean Wright, in the Boston Academy. 
 
 EDWARD L. WILSON, 853 Broadway, New York. 
 
 (O 
 
THE BEST REAPERS IN THE FIELD OF ART HAVE LEFT FOR US 
 THE WINNOWED GRAIN, IN 
 
 JOHN BURNET'S "ART ESSAYS." 
 
 COMPOSITION, LIGHT AND SHADE, 
 EDUCATION OF THE EYE. 
 
 Fac-simile Photo-lithographic Reproduction of Three Works in One 
 from the (1822-1827) Originals. 
 
 This work should be in the hands of every one who would understand the prin- 
 ciples of art. It teaches every one, from the rudiments to the highest forms of 
 composition. Photographer and painter alike will find it invaluable. One 
 hundred and forty fine illustrations and etchings (some of them full page) are 
 given from the most exemplary works of Cuyp ; Potter ; Ostade ; Burnet ; 
 Claude ; Rubens ; De Laer ; Terburg ; Metzu ; Rembrandt ; Corregio ; Raphael ; 
 Guido ; West ; Domenichino ; Wilkie ; and others. 
 
 For twenty years it has been my personal Art Text-book. It is invaluable, 
 and I give it the highest commendation. Edward L. Wilson. 
 
 If photographers really cared for art, which I sometimes doubt, and knew 
 the value of these books, you would sell a large edition. H. P. Robinson. 
 
 The " Practical Essays of Art" form the safest guide to all students of pic- 
 torial arrangement and composition. It is not a book to be placed on the 
 library shelves to be consulted from time to time, but rather one to be studied 
 daily until all the principles it advances have become a part of one's definite 
 knowledge. Delight in possession of this sort no money can express. 
 
 J. Wells Champney. 
 
 You certainly deserve great credit for resurrecting this valuable and much 
 needed Avork, and success is sure to come. Enoch Root. 
 
 Mr. Wilson has rendered a service to artists, amateurs, and students, by the 
 republication of these essays of the late John Burnet, which have been long 
 out of print, and difficult to procure in their original form. He has availed 
 himself of the new art of reproduction by photography, and by its aid has 
 put the original book before us in fac-simile— type and illustrations alike, and 
 in the same form in which it was published — a convenient small quarto, with 
 a well-opened page and ample margins : a form, it may be added, much 
 affected in the first quarter of the century. — The Studio. 
 
 From " Iron." 
 
 The publication of these reproductions will be hailed with great pleasure 
 by all students of art, and particularly by artistic photographers. 
 
 From the 66 London Camera." 
 Dr. Wilson has hit upon the very happy idea of reproducing these three 
 valuable works bound into one volume— with all the original illustrations. 
 The book, indeed, is a fac simile reproduction of the originals, both pictures 
 and text being copied by the aid of photo-lithography. 
 
 From the " St. Louis Photographer." 
 While all parts are of great value to the student, we think the part on 
 " Education of the Eye " will be found of most practical value to the photog- 
 rapher, as that organ is very deficient, and much in need of education. 
 
 Photographers and all other artists owe you a debt of gratitude for giving 
 them the opportunity of becoming possessors of such a work. 
 
 Prof. C. H. Bothamley. 
 
 It is handsomely bound. $100 cannot purchase a copy of the original work. 
 Price, POST-PAID, $4.00, to any country. 
 
 E. L. WILSON, Photo. Pub., 853 Broadway, N. Y. 
 
A NEW BOOK. 
 
 ALL SECRETS OPENED, 
 
 PHOTO-ENGRAVING, PHOTO-ETCHING, 
 and PHOTO-LITHOGRAPHY. 
 
 C" OMPLETE instructions and formulae by an expert in England (W. T. 
 Wilkinson), with my own contributions and translations from the French 
 and German. The whole of the Processes made known. 
 CONTENTS. 
 PART I— PHOTO-ENGRAVING IN LINE. 
 Chapter I— Appliances for Making Photographic Negatives. II— The Wet 
 Collodion Process. Ill— Photographic Manipulations. IV— Apparatus for 
 Printing Upon Zinc. V — Printing on Zinc in Albumen. VI— Printing on 
 Zinc in Bitumen. VII— Direct Transfers to Zinc. VIII— Etching Line 
 Transfers. 
 
 PART II— PHOTO-ENGRAVING IN HALF-TONE. 
 Chapter I— Retrospective. II — Making Grained Negatives. Ill— Etching 
 in Half-tone. IV — Printing from the Block. V— The Transfer of the 
 Drawing and its Treatment before Etching. VI — Hints from all Sources. 
 PART III— PHOTO-ENGRAVING ON COPPER. 
 Chapter I— Subjects in Line. II Half-tone Intaglios. Ill— Half-tone In- 
 taglios— Continued. IV— Half-tone Intaglios, Electro Method. 
 
 PART IV— PHOTO-LITHOGRAPHY IN LINE. 
 Chapter I— Photo-lithography in Line. II — Paper Transfers. Ill— Paper 
 Transfers — Continued. IV- Toovey's Negative Transfer Process. V — To 
 Develop Photo-litho. Transfers. 
 
 PART V— PHOTO-LITHOGRAPHY IN HALF-TONE. 
 Chapter I— Photo-lithography in Half-tone. II— Ink Photos. Ill— Hus- 
 band's Papyrotint Process. 
 
 PART VI— COLLOGRAPHIC PRINTING. 
 Chapter I— Half-tone Photographic Negative. II— The Heliotype Process. 
 Ill— The Collotype Process. IV— Printing from the Collotype Plate. V— 
 The New Home Printing Process. 
 
 It describes graphically and in a comprehensive manner, and supplies a 
 long-felt want.— Photo. Times. 
 We heartily commend a book that is so well made.— Anthony's Bulletin. 
 The knowledge of the subjects treated is becoming more and more a 
 necessity. — The St. Louis and Canadian Photographer. 
 
 180 pages 6# x 8% in. Cloth Bound, Price $3.00, Post-paid. 
 Many illustrations and a complete index. 
 
 Edw. L. Wilson, Photo-Book Publisher, 
 No. 853 Broadway, New York. 
 
The Photographic Times, 
 
 Edited by W. I. LINCOLN ADAMS, 
 
 Is Illustrated Every Week with, a Full-page Picture, 
 
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 Schuman, and F. Mueller, of Germany. 
 
 Notes from the Every-day Gallery Experiences of such well-known 
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 Mora, H. McMichael, J. R. Swain, and John Carbutt. 
 
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The K odak C amera. 
 
 This wonderful little instrument supplies 
 the means for the practice of that most fasci- 
 nating pastime — Amateur Photography — in a 
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 Kodak may be used by anybody who can 
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 PRICE, $25.00. exposures have been made, the camera can be 
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 — inserted. If desired, however, the amateur can finish his own 
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 The Kodak is invaluable for tourists, yachtmen, wheelmen, or for anybody who 
 wishes to obtain an accurate illustrated record of the many interesting sights and 
 incidents of a journey, or of every day happenings. Send for a copy of the Kodak 
 Primer, with sample photograph. 
 
 Good Lantern Slides can be made from KODAK Negatives. 
 
 The Kodak is for sale by all Photo Stock-dealers. 
 
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 for Lantern Slides, are in use by the principal amateurs throughout the 
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 printing, we are enabled to select emulsions for our lantern plates that 
 give the exact tone required. A uniformity is thus secured which can 
 be obtained in no other plates. 
 
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 MANUFACTURERS AND DEALERS IN 
 
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TOILERS OF THE THAMES 
 
 i Lcuitern Slide, by the Author. 
 
T H E 
 
 BOOK OF THE LANTERN. 
 
 BEING A 
 
 PRACTICAL GUIDE TO THE WORKING OF THE 
 OPTICAL (OR MAGIC) LANTERN. 
 
 WITH FULL AND PRECISE DIRECTIONS FOR MAKING AND 
 COLORING LANTERN PICTURES. 
 
 WITH SEVENTY-FIVE ILLUSTRATIONS. 
 
 BY 
 
 T. C. HEPWORTH, F.C.S., 
 
 FOR MANY YEARS LECTURER TO THE ROYAL POLYTECHNIC INSTITUTION, LONDON ; 
 LECTURER ON PHOTOGRAPHY AT THE BIRKBECK INSTITUTION J AND 
 EDITOR OF "THE CAMERA." 
 
 First American from the Second English Edition. 
 
 NEW YORK: 
 EDWARD L. WILSON, 
 853 Broadway. 
 
 1 88 9. 
 
Entered, according to Act of* Congress, in the year 1889, 
 By EDWARD L. WILSON, 
 In the Office of the Librarian of Congress, at Washington, D. 
 
CONTENTS. 
 
 Chapter Page 
 
 I. — The Construction of the Lantern BP 1 
 
 II. — The Optical System of the Lantern • . .16 
 
 III. — Oxygen Gap. Making 30 
 
 IV. — Limelight Jets, Regulators, Pressure Boards, <ic. . 50 
 V. — The Limelight and its Management . . .71 
 
 VI.— Screens 86 
 
 VII. — The Preparation of Lantern Slides, Diagrams, &c, 
 
 without the aid of Photography . . . .97 
 
 VIII. — Lantern Slide Making by the Wet (Photographic) 
 
 Process . 104 
 
 IX. — Lanterh Slides on Dry Plates ♦ , # .109 
 
 X. — Home-made Gelatine Plates . , ♦ . .125 
 
Vi CONTENTS. 
 
 XI. — On Colouring Photographic Transparencies for 
 
 Lantern Slides • .145 
 
 XII. — The same subject continued . • • # . 
 
 XIII. — Description of various Experiments — Chemical, 
 
 Electrical, &c. — for Class Instruction, which are 
 possible with the Lantern 171 
 
 XIV. — The Lantern as an Aid to the Photographer . . 204 
 XV.— The Art of Making Photo-Micrographs . .211 
 
 XVI. — Enlarging Photographs with the Lantern 222 
 
 XVII. — The Lantern Microscope and the Opaque Lantern . 240 
 
 XVIII. — Various Lantern Accessories . . . 250 
 
 XIX. — Practical Hints to those who Employ the Lantern 
 for Scientific Demonstration or for Entertain- 
 ments in the Drawing Room or Lecture Hall 264 
 
PREFACE. 
 
 S it is customary for an author to say a few 
 words to his readers by way of introduction, 
 before they become better acquainted with 
 one another, let me briefly state the reason why 
 this book is written, and why I felt some confidence 
 in undertaking the work. The magic lantern has 
 always been one of the most popular instruments 
 ever made. So popular has it been, that children by 
 the thousand recognise its charms, while many of more 
 mature years have a secret hankering after it, which 
 they would fain leave unacknowledged : u For it is but a 
 toy," think they, "and we have left toyland behind 
 us since we reached man's estate." Let me 
 sympathise with these feelings, and own for my pai-t 
 a weakness for pantomimes and fireworks, which 
 weakness I have occasionally the opportunity of 
 indulging, on the plea of taking my children out for 
 a treat. But let me say at once that the magic lantern 
 
viii 
 
 PREFACE. 
 
 is now no toy, but is recognised as a valuable aid to 
 education far and wide. The reason for this is not 
 far to seek. First, we have to look at the vast 
 improvement in the instrument itself. So long as the 
 greasy, evil-smelling oil lamp was almost the sole 
 illuminant available, and roughly executed daubs in 
 varnish colours on glass the only works of art (?) 
 which could be purchased for the lantern, it did not much 
 signify that the lenses were also of a faulty character, 
 and no better in quality than the " bull's eye" of the 
 nocturnal policeman. But when the brilliant limelight 
 came to be adapted to the lantern, it was at once seen 
 that the capabilities of the instrument were not only 
 much increased, but almost without limit. It would 
 be difficult to say offhand how many persons visited 
 the Royal Polytechnic Institution in the forty years 
 during which it was open to the public ; but it is 
 within my own experience that at one period, at the 
 time of the " ghost " illusion, they came at 
 the rate of two thousand per diem. There is no 
 doubt whatever that the Polytechnic caused this form 
 of amusement to become popular, for the lecturers 
 affiliated to the Institution travelled the country 
 round, and gave similar entertainments in all parts. 
 
 There are few branches of science in which the 
 optical lantern cannot be made useful for purposes of 
 demonstration, and as this fact becomes better known, 
 every schoolroom in the kingdom will be provided 
 with one. In every lecture theatre worthy of the 
 
PREFACE. 
 
 IX 
 
 name the instrument is already constantly called upon 
 to illustrate various subjects, and I venture to state 
 that its use will be greatly increased now that so 
 much attention is being paid to the art of photo- 
 micrography, by which enlarged pictures of micro- 
 scopic objects can be easily rendered available for 
 projection by means of the lantern. A large class 
 of students can thus at the same moment study the 
 structure of an organism which may be in reality 
 invisible to unaided sight by reason of its minute 
 size. 
 
 But during the past few years, the number of those 
 who interest themselves in the lantern and its 
 capabilities has been vastly increased by the sudden 
 popularity of the art of photography. Amateur 
 photographers are now to be found in every town in 
 the kingdom, and they are beginning to find out that 
 there is no better, method of showing their friends the 
 pictures which they have taken than by means of the 
 optical lantern. The same instrument, too, as it 
 offers a means of making permanent enlarged copies 
 of small photographs, serves with them a double 
 purpose. 
 
 The introduction as illuminants of the hydrocar- 
 bons, under the name of petroleum, parnffin, kerosene, 
 &c, has also had its share in the recent development 
 of the optical lantern, for now a few pounds will 
 purchase a better instrument than was procurable at 
 any price twenty years ago. 
 
 b 
 
X 
 
 PREFACE. 
 
 With these facts in view, I have long thought that 
 a thorough guide to the working of the optical lantern, 
 the preparation of its diagrams and pictures, the 
 colouring of the same, the production of photo- 
 micrographs, and everything pertaining to lantern 
 work, would fill a vacant place in technical literature. 
 Beyond the two or three shilling handbooks which 
 have appeared, there is nothing of the kind procurable; 
 and in the space available in such books, it is obvious 
 that the various matters to which I have referred 
 cannot be sufficiently dealt with. 
 
 Some of the matter here printed has already 
 appeared in The Amateur Photographer, and in The 
 Camera. The author is indebted to the proprietors of 
 both those periodicals for their courtesy in allowing 
 both text and cuts to be reproduced in this work. 
 
 T. C. HEPWORTH. 
 
 45, St. Augustine's Road, Camden Square, 
 London, N.W. 
 
 January , 1889. 
 
CHAPTER L 
 
 m 
 
 THE CONSTRUCTION OF THE LANTERN. 
 
 KN" that wonderful autobiography of Benvenuto 
 Cellini, which Horace Walpole described as 
 being " more amusing than any novel," we 
 find the account of a weird incantation scene which 
 took place in the Colosseum at Rome. Cellini tells us 
 that he had made the acquaintance of a Sicilian priest 
 who volunteered to initiate him into some of the 
 secrets of necromancy. A meeting was appointed at the 
 Colosseum, where " the priest, having arrayed himself in 
 necromancer's robes, began to describe circles on the earth 
 with the finest ceremonies that can be imagined. I must 
 say that he made us bring precious perfumes and fire, and 
 also drugs of fetid odour. When the preliminaries were 
 completed, he made the entrance into the circle ; and 
 taking us by the hand, introduced us one by one inside it. 
 Then he assigned our several functions : to the necromancer, 
 his comrade, he gave the pentacle to hold ; the other two 
 of us had to look after the fire and the perfumes ; and 
 then he began his incantations. This lasted more than an 
 
 B 
 
2 
 
 THE BOOK OF THE LANTERN. 
 
 hoar and a half, when several legions appeared, and the 
 Colosseum was all full of devils." It has been suggested 
 that these effects were produced by some form of lantern 
 casting images on the smoke from the burning drugs. 
 Should this surmise be correct, it would refer the use of 
 the instrument back to the early half of the sixteenth 
 century — Cellini having been born at Florence in the 
 year 1500 — and the event spoken of having occurred in 
 his early manhood. 
 
 But on careful perusal of the entire account of these 
 supernatural wonders, I feel convinced that no kind of 
 optical instrument can have been used. To produce any 
 remarkable effect in such a large space as that covered by 
 Vespasian's Amphitheatre would certainly tax the powers 
 of the best modern lantern. Besides which, Cellini was 
 a remarkably clever and observant man, and would 
 
 Fig. 1. 
 
 probably have detected the employment of any such 
 apparatus. It is far more probable that the priest was 
 aided by a number of confederates, and that these were in 
 
THE BOOK OF THE LANTERN. 
 
 3 
 
 reality the legions of devils which so impressed the super- 
 stitions mind of the Florentine goldsmith and sculptor. 
 With far more reason might we suspect the use of the 
 lantern in those manifestations which are said to take 
 place among the so-called spiritualists and their mediums 
 of to-day. 
 
 We are certainly on much firmer ground when we 
 ascribe the first conception of the instrument to Athanasius 
 Kircher, the learned Jesuit of the seventeenth century, 
 who has left so many volumes to testify to the great gifts 
 which he possessed. For in one of these books, Ars Magna 
 Lucis et Umbrce, we not only find descriptions and dia- 
 grams of numerous optical contrivances (I may note in 
 passing that many of these drawings, redressed and 
 elaborated, appear in modern text-books as new ideas), 
 but several which show that Kircher quite understood the 
 main principle upon which the optical lantern depends. 
 A tracing of one of these rude cuts is given at fig. 1, 
 from which it will be seen that the design to be projected 
 by the lens is illuminated by three candles — the brightest 
 form of artificial light then known — and an inverted 
 image is thrown upon a screen at a distance. 
 
 Here we have practically the germ of the aphengescope, 
 or opaque form of lantern. But modern writers on the 
 subject, in referring to Kircher, have curiously overlooked 
 this most suggestive drawing, and have given another one 
 from his book, which they erroneously describe as the first 
 form of magic lantern. This I also reproduce (see fig. 2). 
 The description appended to the cut certainly does not 
 bear out that view, but points rather to a means of in- 
 
 B2 
 
4 
 
 THE BOOK OF THE LANTERN. 
 
 creasing the light from *any lantern by using a parabolic 
 reflector behind the lamp or candle flame. The passage 
 (translated) runs as follows : — 
 
 " To construct an ingenious lantern which may show 
 things written at a great distance so that they can be 
 read — 
 
 " Let a lantern be made of the same cylindrical figure 
 
 C 
 
 as you see here represented, in whose base let a concave 
 mirror be placed, having as parabolic a shape as is possible. 
 Within the focus of this mirror let F, the flame of a 
 candle, be fixed, and you will have what is required, for 
 it will shine with such unwonted splendour as to show by 
 night, without any trouble, even the smallest letters when 
 examined by the aid of a telescope. But persons looking 
 at the flame from a distance will think that it is a great 
 fire. If the inner sides of the cylinder are fashioned of 
 polished tin in the form of an ellipse, they will increase 
 the light. But the figure here given will sufficiently show 
 
THE BOOK OF THE LANTERN. 
 
 5 
 
 the invention. E marks the handle and the opening (or 
 window) ; C the chimney or funnel." 
 
 It is worthy of note that Sir David Brewster, in his 
 " Natural Magic," quotes the incantation scene from 
 Cellini at length, and states his conviction that the 
 appearances were brought about by optical apparatus, 
 although he admits that little was known of the action of 
 mirrors and lenses until the time of Kircher. 
 
 It is obvious, however, that such primitive instruments 
 were of the crudest kind, and can only be regarded as 
 interesting curiosities. Up to within quite recent times 
 lanterns for projection held about the same relation to the 
 modern instrument as does the bone needle of the cave 
 men to the sewing machine. Like most instruments of 
 precision, the optical lantern is the outcome of many years 
 of patient thought and labour, and is the result of the 
 working of many minds. No individual can be credited 
 with its invention or discovery. The crude idea is, as we 
 have seen, to be found in Kircher's book, and one improve- 
 ment has been suggested here, and another there, until we 
 have before us a very perfect optical appliance. 
 
 The gradual advance in the instrument very naturally 
 follows the introduction of improved illuminants for more 
 general purposes. The oil lamp was superseded by the 
 argand gas-burner, and this was in its turn supplanted by 
 the whiter and better light afforded by mineral oil, while 
 before this, for the better kind of lanterns, Lieutenant 
 Drrmmond's brilliant limelight was quickly adopted as the 
 best for the purpose. This, too, may possibly, in the near 
 future, give way to the still more brilliant electric arc 
 
6 
 
 THE BOOK OF THE LANTERN. 
 
 light. But the introduction of mineral oil, in conjunction 
 with the adaptation of photography to lantern pictures, 
 have been the main factors in giving the instrument its 
 present popularity. 
 
 The first lantern burning mineral oil, and called the 
 Sciopticon, came to us from America. It was constructed 
 on scientific principles, and was far in advance of anything 
 of the kind before produced. Tt possessed good lenses 
 and a powerful lamp, the two broad wicks of which were 
 placed edgeways towards the condenser. The lamp was so 
 closed in that it formed a combustion chamber, and burnt 
 the oil under the best conditions. The lantern, however, 
 
 Fig. 3. 
 
 had its faults. The front glass of the lamp was apt to 
 break, and a dark vertical line was always seen upon the 
 sheet — a line which was in reality the image of the dark 
 space between the two wicks. By adding a central wick, 
 and by making certain alterations in the ventilation of the 
 lamp chamber, Messrs. Newton conquered both these 
 difficulties, and a far more perfect form of lantern has 
 
THE BOOK OF THE LANTERN. 
 
 7 
 
 been the result. The same makers have, too, made the 
 lamp distinct and separate from the lantern,, so that, if 
 required, it can readily be removed, and a lime-jet used 
 in its stead. The form of lamp referred to is shown in 
 fig. 3, both open for trimming and closed as in use, 
 while a complete mineral oil lantern, of the kind 
 now adopted by most makers, is seen at fig. 4. The 
 
 Fig. 4. 
 
 management of oil lanterns is so simple, really resolving 
 itself into the necessity for keeping the burning wicks at 
 a correct height, and putting the slides or pictures on the 
 stage provided for them, that no more space need be 
 devoted to this portion of my subject. 
 
 The great advantage of using a pair of lanterns is that 
 whilst a picture is being shown by one, another picture is 
 being made ready in the other, and there is no pause or 
 blank screen when the change is made. The so-called dis- 
 solving views, which are produced by making this change 
 slowly, made a great sensation when they were first intro- 
 
8 
 
 THE BOOK OF THE LANTERN. 
 
 duced, perhaps because few knew exactly how they were 
 managed. But they are now so common that many 
 persons consider them rather tiresome than otherwise. 
 Still, they give the operator a ready means of varying his 
 work, if the dissolving apparatus be used with judgment. 
 Thus most beautiful effects can be obtained in landscapes, 
 more especially in seascapes, by using photographic 
 cloud pictures, the gradual blending of one clouded sky 
 into another giving fine aerial and very natural results. 
 In one set of pictures which I prepared to demonstrate 
 the beauties of cloudland, in connexion with a lecture on 
 
 Fig. 5. 
 
 ballooning, a sunrise picture was made to melt into a sun- 
 set picture, and in due time this latter gave place to a 
 moonlight effect. I am convinced that much can be done 
 in this direction if time can be given to the preparation of 
 the pictures. 
 
THE BOOK OF THE LANTERN. 
 
 9 
 
 Originally for such effects two separate lanterns were 
 used side by side, but now a biunial lantern, with one 
 optical system above the other, is employed (see fig. 5). 
 The modern arrangement is far more convenient for the 
 operator, for the apparatus is compact and every adjustment 
 is within easy reach of his hand. A lantern so constructed 
 generally consists of a strong wooden body, lined with metal, 
 with cells for the reception of the condensing lenses. 
 Openings at the back shaped thus JL allow for the necessary 
 to and fro motion of the lime jets and their trays. 
 Between these openings, on the outside of the lantern 
 body, is fixed the dissolving key or tap, connected by india- 
 rubber tubes with the two jets (see fig. 6). In front of the 
 
 Fig. 6. 
 
 instrument are the stages for the reception of the slides, and 
 the metal plates to which are affixed the telescopic tubes for 
 holding the objective lenses. These plates are hinged, and 
 their inclination upward or downward to make the two 
 discs concentric on the sheet or screen is governed by 
 milled headed screws. The objectives can by this means 
 be made to slightly approach one another, while the con- 
 densers remain fixed. It is obvious that it would be better 
 
10 
 
 THE BOOK OF THE LANTERN. 
 
 if the condensing lens also moved with the objective so 
 that the optical axis of one should agree with the 
 other. This could easily be done by making the upper 
 lantern move on a central pivot, and clamping it with a 
 fixed screw ; but the more faulty and elaborate plan has 
 been adopted by manufacturers, and will probably hold its 
 own for a long time yet. 
 
 It is certainly too much the fashion to adorn lanterns 
 with a mass of heavy brass-work. Like any other adorn- 
 ment, the brightly-lacquered brass looks well enough, but 
 represents, to my thinking, a waste both of material and 
 of workmanship, which adds greatly to the cost of an 
 instrument, without adding one jot to its efficiency. In- 
 deed, this brass -work is a positive disadvantage when a 
 lantern has to be carried from place to place by a busy 
 lecturer, and constitutes, not only an inconvenience, but a 
 tax, in the shape of "excess luggage." This superfluous 
 metal must, I suppose, be looked upon as a custom of the 
 trade, which it is very difficult to break down. It is the 
 same case with the microscope, the delicate brass-work of 
 which often costs more than the lenses, expensive though 
 the latter are. In each case the metal- work represents a 
 convenience in operating the instrument, but much of it 
 could be dispensed with, without in any way detracting 
 from its performance. We may, I think, gain a lesson 
 in the construction of an ideal lantern by examining 
 a modern photographic camera for tourists' use, where the 
 greatest rigidity is combined with extreme lightness, and 
 metal is used but sparingly. Looking at such an 
 instrument, we find that it must be extended for f )cus- 
 
THE BOOK OF THE LANTERN. 
 
 11 
 
 sing purposes, and that its chief expanding part is made 
 of folded leather (concertina bellows fashion). Now, why 
 should not the same arrangement be adopted for the 
 optical lantern ? We here require a similar extension of 
 the front of the instrument, in order to suit the foci of 
 the different lenses employed, and according to the dis- 
 tance and size of the picture which we wish to project on 
 the screen before us. Surely some arrangement of the 
 kind could be adapted to the lantern. If such a change 
 of construction were brought about, and with analogous 
 alterations in other parts, the weight of a double or triple 
 lantern would certainly be reduced to about one-third of 
 of what it is at present. It may, perhaps, take some time 
 for opticians to appreciate this view of the case, and there 
 may be good trade reasons for not making a change of 
 such a radical nature. I am not behind the scenes, and 
 so cannot tell. It might certainly be urged with some 
 truth that there is no need to be in a hurry to alter the 
 present type of lantern, seeing that lightness of construc- 
 tion may soon be brought about by the substitution of 
 aluminium for brass. The production of the former 
 metal is daily becoming cheaper, and as its weight, bulk 
 for bulk, is about one-third that of brass, and as it is 
 strong, not easily tarnished, and in other respects is suit- 
 able for the purpose of lantern construction, we may look 
 forward to its adoption in this service. 
 
 Where a lantern is used for educational purposes it 
 requires certain additions which are quite unnecessary in 
 exhibition instruments. On the other hand, several 
 ornamental adjuncts which are desirable in the latter 
 
12 
 
 THE BOOK OF THE LANTERN. 
 
 form of lantern may be dispensed with in the instrument 
 designed for the lecture or school room. Indeed, in an- 
 other chapter I point out how a very simple arrangement 
 
 Fig. 7. 
 
 of lamp and lenses can be made serviceaoie for educational 
 work. One of the most important additions to an instru- 
 ment used for teaching is what is known as the 
 vertical attachment. The object of this arrangement 
 
THE BOOK OF THE LANTERN. 
 
 13 
 
 is to show certain preparations and other objects which 
 must be kept in a horizontal position during exhibition. 
 " Horizontal Attachment " would, therefore, perhaps be a 
 more sensible name for the apparatus — the construction of 
 which can be easily understood by reference to the annexed 
 cut (fig. 7). The round opening in front, four inches in 
 diameter, is the place where the apparatus fits on to the 
 lantern, the lenses, &c, of the latter having been removed 
 for its accommodation. So that the light from the lantern is 
 received by the sloping mirror, and is reflected upwards 
 through a condensing lens, which is placed horizontally. 
 This lens forms a table or stage upon which different slides 
 or preparations can be laid for exhibition. The image is 
 formed by the lens above, and by the prism above that is 
 redirected and cast upon the sheet or screen. It is obvious 
 that some loss of light must result from filtering the rays 
 through so many media, but this cannot be helped. In 
 the chapter dealing with experiments possible with the 
 lantern the use of this vertical attachment will be further 
 alluded to, when its value will be better appreciated. 
 
 Double lanterns to burn oil are usually placed side by 
 side, but fig. 8 shows a convenient form of lantern which 
 has been recently introduced, and which is so constructed 
 that one lantern can be detached from its fellow. Thus, 
 when the lime-light is used they are adjusted one above 
 the other, and when the oil lamp is employed they are 
 placed side by side. Mr. Tyler has still more simplified 
 the matter by inventiog a biunial lantern which burns 
 oil, although the position of the two lamps is one above the 
 other. This he achieves by the use of a bent chimney, 
 
14 
 
 THE BOOK OF THE LANTERN. 
 
 which proceeds from the lower lantern and carries away 
 the hot air, so that it cannot influence the lamp above. 
 
 Fig. 8. 
 
 In the triple lantern (fig. 9) we have three optical 
 systems, and of course three lime-lights. This is the 
 exhibition instrument par excellence, and is commonly 
 used by those exhibitors who may be described rather as 
 entertainers than lecturers. The third lantern is in reality 
 not often used. It is kept in reserve for producing occa- 
 sional effects while the other two lanterns are at work. 
 
 In some respects the optical lantern resembles the king of 
 musical instruments, for the effects which can be produced 
 by it are dependent upon and limited by the number of its 
 parts. If an organ has but one row of keys, the instrument 
 can do little beyond furnishing an accompaniment. With 
 
THE BOOK OF THE LANTERN. 
 
 15 
 
 two rows its capabilities are much increased, for the organist 
 can use them alternately in contrast with one another, or 
 can combine them. With three claviers, his powers are 
 once more amplified, and he can introduce those changes 
 of musical colour for which our language provides no 
 descriptive word. So it is with the lantern. If it have 
 
 Fig. 9. 
 
 but one optical system the operator can only use it as a 
 means of showing simple pictures or diagrams. If it have 
 two systems he can produce the popular dissolving views ; 
 and if it be provided with a third set of lenses, he can 
 mingle with the views shown those " effects," as they are 
 called, which are so welcome to an audience of young 
 folk, and very often to children of a larger growth. 
 
CHAPTER II. 
 
 THE OPTICAL SYSTEM OF THE LANTERN. 
 
 HE three great essentials of a good optical lantern 
 are the light, the condenser, and the objective, the 
 two latter forming the optical system of the instru- 
 ment. Theoretically, the light to give the best results should 
 be a mere point of radiance, but unfortunately this is 
 at present almost unattainable. I say almost, because I 
 believe it to be quite within the bounds of possibility to con- 
 struct an electric arc light which shall f ulfil all the conditions 
 as to steadiness, uniformity of action, and maintenance of 
 a fixed position, which are required in lantern work. Such 
 a light has not yet been found, but when electricity 
 becomes more general as a source of illumination in our 
 cities and towns, — as it surely will, — an arc light or 
 regulator of the required description will, I feel confident, 
 soon be forthcoming. The invention of such a con 
 trivance, when the means of obtaining the requisite 
 current to feed it is so limited, would at present have the 
 disadvantage of coming before its time. The electric 
 arc light has been used more than once experimentally 
 in the lantern, with the most promising results. 
 
THE BOOK OF THE LANTERN. 
 
 17 
 
 The best source of illumination .for the lantern 
 is, — when we exclude electricity for the reasons just 
 indicated, — the lime-light. It has the good qualities 
 of intense whiteness, steadiness, ease of management, 
 portability, and although not a point, its area of radiance 
 is not much greater than the space covered by a pea. I 
 shall describe in detail the method of its production and 
 management later on. 
 
 Having then a convenient form of intense light, we have 
 next to consider the means of using it to the best ad- 
 vantage. We must start with the acknowledgment that 
 in enlarging the image of a picture we must sacrifice a 
 large amount of light. But by using properly-constructed 
 lenses, we can make this loss as little as possible. As 
 already pointed out, the optical system of a lantern 
 consists of two distinct parts, — the eondenser and the 
 objective lenses. 
 
 As many of my readers may be quite unacquainted with 
 
 Fig. 10. 
 
 the matter under consideration, I will point out why this 
 double system is necessary, and describe the work per- 
 formed by each set of lenses. In the annexed diagram, 
 fig. 10, L represents the lime cylinder, with rays of light 
 emanating from it and illuminating the picture P, which 
 
 c 
 
18 
 
 THE BOOK OF THE LANTERN. 
 
 we require to show in an enlarged form. 0 is the objective 
 lens by which this enlargement is to be brought about ; 
 the sheet or screen upon which the picture is projected 
 being suppose d to be far away to the right. With such an 
 arrangement of parts what should we see on that screen ? 
 In the first place we should have but a very feeble light, 
 for as will be seen by reference to the diagram, most of 
 the luminous rays are wasted altogether, only the cen- 
 tral ones proceeding through the lens O. It will be 
 seen also that these rays go through the central portion 
 of the picture only, and that therefore only this part 
 can be projected on to the distant screen. So that as a 
 result of our first efforts at lantern projection, we get an 
 indistinct and badly-lighted portion of a picture presented 
 to us. How can we remedy this state of things ? Ob- 
 viously, the thing to be done is to cause more of the rays 
 from our light source to be utilised, and tnis can be brought 
 about by placing between that light and the picture a lens 
 which shall condense the light upon that picture, and which 
 is therefore known as the condenser. 
 
 In fig. 11 we see a repetition of the diagram, fig. 10, with 
 
 Fig. 11. 
 
 the addition of a condenser, shown m this case, for the 
 sake of simplicity, as a single lens. Referring once more 
 
THE BOOK OF THE LANTERN. 
 
 1!) 
 
 to this imaginary picture upon our screen, we now see that 
 it is complete. It is no longer the central fragment of a 
 design, but covers the sheet, and is equally illuminated. 
 We can at once see the reason for this welcome change by 
 looking once more at our revised diagram, fig. 11. The 
 rays of light instead of being wasted in illuminating the 
 inside of the lantern box, are refracted by the lens which 
 we have introduced, and are bent towards the objective. 
 
 In my diagrams, for the sake of simplicity, I have 
 represented each lens as consisting of a single piece of 
 glass of plano-convex form. Such lenses are found in toy 
 lanterns of the cheapest kind, but are, as might be ex- 
 pected, extremely faulty in performance. In the enlarged 
 picture, they give, owing to their total want of correction, 
 badly-defined margins, curved lines, and fringes of colour. 
 
 Having now seen the purpose fulfilled by the condensir g 
 lens of the optical lantern, let us further consider its best 
 form, and let me at once correct an error into which a 
 purchaser is likely to fall. I have sometimes heard the 
 possessor of a lantern speak somewhat boastingly of his 
 instrument as one with 5, or perhaps 6-inch condensers, 
 the more ordinary size being 4 inches, and often only 
 3| inches. For lantern projection, any size over 4 inches 
 is a positive disadvantage, and instead of representing a 
 gain, means really a great loss of light. The reason for 
 this is readily seen. What may be called the standard size 
 for a lantern picture is 3 inches in diameter (the entire 
 slide with its margin measuring 3^ inches). If the picture 
 be framed in a circular 3-inch mount, a 3|-inch condenser 
 will amply illuminate it. If, however, the orifice of the 
 
20 
 
 THE BOOK OF THE LANTERN. 
 
 mount be square or cushion-shaped, such a small condenser 
 would infallibly cut off the corners of the projected image, 
 and for such pictures, therefore, a 4-inch condenser is 
 necessary. But the smaller condenser transmits more 
 light, for the reason that being of shorter focus, the lime 
 cylinder is brought nearer to it. Some well-known 
 exhibitors, seeing the great importance of getting all the 
 light upon the screen that they possibly can, use nothing 
 but 3 J- inch condensers, but this obliges them to confine 
 themp elves to round pictures. On the whole, I prefer 
 myself the 4 -inch condenser, for although I lose some 
 light, I can make use of any shaped pictures or diagrams 
 which may be required. (If the lantern be used for 
 photographic enlarging purposes, then a large-sized con- 
 denser is the great thing needful, at least, we must have 
 one of a size large enough to cover the negative which 
 has to be enlarged ; a quarter-plate size necessitating a 
 5 -inch condenser and so on. But in that case brilliancy 
 of image is quite a secondary matter, and is compensated 
 for by extension of time occupied in the operation.) It 
 must also be borne in mind that, quite apart from the 
 question of focal length of the condensing lens, there is a 
 limit to the near approach of the incandescent lime 
 cylinder towards it, for the intense light is naturally ac- 
 companied by a fervent heat, which will surely crack 
 a lens if it be too near to it. In the chapter on the 
 working of the lime -light, precautions against this accident 
 are fully dealt with. 
 
 There are two forms of condensers, either of which 
 may be commonly found in commercial lanterns. One 
 
THE BOOK OF THE LANTERN. 
 
 21 
 
 consists of a pair of plano-convex glasses mounted in one 
 cell, with their curved surfaces all but touching one another. 
 This form was, I believe, first introduced with the 
 American sciopticon. It is shown at fig. 12. The other 
 form of condenser is that devised (but not for lantern use) 
 by Sir John Herschell, and which consists of a double 
 
 Fig. 12. Fig. 13. 
 
 convex lens, associated with a meniscus, the concave side 
 of the latter being next the radiant point, as shown in 
 fig. 13. In a good condenser we want not only quantity 
 of light, but also good quality, and these properties can 
 only be secured by careful attention to certain points of 
 construction. Quantity of light is governed by size and 
 focal length, as already pointed out, and it may be as well 
 to indicate here the manner in which lanterns furnished 
 with condensers of larger size than I have recommended 
 may be made to transmit a greater amount of light by the 
 inter j osition of another lens. There were at the old Poly- 
 technic Institution some antique lanterns with 10-in. con- 
 densers, this large size being necessary to cover the 8 -in. 
 hand-painted transparencies which were in use before 
 photography worked a revolution in such things. Such a 
 large condenser, of course, meant a great loss of light, as 
 
22 
 
 THE BOOK OF THE LANTERN. 
 
 already pointed out. So the suggestion was made that a 
 small lens should be interposed between the light and the 
 condenser. This was done with a wonderful gain in the 
 performance of the old lanterns. Fig. 14 will show how 
 
 Fig. 14. 
 
 the additional lens brought this improvement about. Many- 
 other forms of condensing lenses have from time to time 
 been suggested and experimented with, some of these em- 
 ploying three or more combinations. But these various 
 patterns, although one or two of them seem very promising 
 in form, have not been taken in hand by makers generally, 
 — possibly on the score of expense, and probably owing as 
 much to that hesitation and laziness common to human 
 nature, which keeps us all to a well-beaten track. 
 
 But a few years ago the question of lantern lenses was 
 revived by a paper read by the late Mr. J. H. Dallmeyer 
 before the Photographic Society of Great Britain. The 
 reader of this excellent contribution to the subject, explained 
 in the first instance that a well-known worker with the 
 lantern had called his attention to the great want of more 
 
THE BOOK OF THE LANTERN 
 
 23 
 
 perfect lenses for use with the instrument. Mr. Da limey er 
 thereupon determined to tackle the subject, and produced 
 new forms of condensers and objectives, a description of 
 which he placed before the Photographic Society. I can- 
 not do better than quote the description of the new con- 
 denser from this paper, and at the same time reproduce 
 one of the drawings shown in illustration of the remarks 
 made (see fig. 15) : — 
 
 R 
 
 A | J 
 
 B 
 
 
 r " — 
 
 
 
 
 Fig. 15. 
 
 The condenser is of 4-in.. effective diameter, and 2f- 
 in. equivalent focal length. Assuming the light to be at 
 a safe distance of 2f in. from the flat surface of the first 
 lens, this condenser collects an angular pencil of about 
 66°, i.e., about 20 per cent, more light than the shortest 
 focus symmetrical. It consists of two unsymmetrical 
 lenses, A and B. A is a plano-convex of flint 3|-in. 
 diameter, and B is a double convex of crown glass of 4-in. 
 diameter. The lenses are mounted at a certain distance 
 apart, with their deep sides facing each other. Approxi- 
 mate correction of chromatic aberration for centrical pencils 
 is obtained by a proper apportioning of their focal lengths, 
 and the distance at which they are placed. Thus : ray 
 
24 
 
 THE BOOK OF TILE LANTERN. 
 
 L R, after refraction by lens A, diverges into a prismatic 
 beam ; this falls upon different parts of lens B, which, 
 while acting upon the two extremes, — the red and the 
 violet, — in contrary directions to A, canses them to emerge 
 parallel, the condition of achromatism, when they converge 
 to the conjugate focus f, about 9 in. removed from B. The 
 spherical aberration is reduced to a minimum by the forms 
 of the lenses employed, i.e., ray Lr, refracted by the central 
 portions of the lenses, meets the axis at the same point f 9 
 as the marginal rays, or nearly so. I have decided upon a 
 4-in. (effective) diameter condenser, since it fully illumi- 
 nates the corners of a 2|-in. square slide. Of course, a 
 circular slide of 3 in. only requires a 3J-in. diameter con- 
 denser, of proportionately shorter focal length. I need 
 hardly say that the glass composing this condenser has 
 been selected with esp:cial care. It is perfectly limpid, or 
 colourless, and will remain so ; it is free from strice and air 
 bubbles, and has a perfect polish. In fact, it is Chance's 
 best glass ; the only drawback being its cost." 
 
 Mr. Dallmeyer goes on to remark that the defects in the 
 glass of a lantern condenser, are of far more importance than 
 similar defects in the objective, so far as purity and quality 
 of the illuminated disc are concerned. He refers to such 
 defects as scratches, air-bubbles, and the like. In the case 
 of an air-bubble in the objective lens, it is really of no 
 moment whatever. I have known of a photographic lens, 
 otherwise of splendid quality, being rejected because of 
 a tiny air-bubble near its margin, the purchaser being quite 
 content to exchange it for a far inferior lens without such 
 an insignificant blemish. Such a bubble would have no 
 
THE BOOK OF THE LANTERN. 
 
 25 
 
 effect whatever upon the performance of the lens, whether 
 used with a camera, or as a lantern objective, supposing it 
 to be suitable to lantern work in other respects. But 
 transfer the bubble from the objective to the condenser, and 
 it at once constitutes a real eyesore, which will be terribly 
 magnified on the screen. For this reason lantern owners 
 should take the greatest care to prevent their condensers 
 becoming scratched, for a mark hardly visible on the glass 
 will become fatally apparent on the screen. 
 
 It will be seen, from what has gone before, that the duty 
 of the condensing lens is to take up and utilise as large a 
 bundle of light rays as is practicable, and with those rays to 
 brightly illuminate the whole of the picture or slide placed 
 against it. The other part of the optical system of the 
 lantern is the objective lens, which is destined to 
 form a magnified image of that picture or slide. To this 
 important part of the apparatus I must now turn the 
 reader's attention. 
 
 As the duty of the condenser is to give the greatest 
 amount of illumination to the lantern picture or slide, so 
 the province of the objective lens is to form as perfect as 
 possible a magnified image of that picture upon the screen 
 or sheet placed for its reception. Toy lanterns are fre- 
 quently fitted with a doub'e convex, the worst form of all, 
 or with a plain convex lens, which is little better. With 
 regard to lanterns of more pretension, we find that different 
 makers adopt different forms and combinations for their 
 objectives. Some use a couple of plano-convex achromatic 
 lenses, in conjunction with a stop or diaphragm, the flat 
 sides of the lenses being next the light ; a very 
 
2b 
 
 THE BOOK OF THE LANTERN. 
 
 good form indeed, provided that the lenses are of sufficient 
 diameter bo take in the entire cone of rays from the con- 
 denser. This has always been a stumbling-block in 
 adjusting lenses of short focus to the lantern, for it stands 
 to reason that the shorter the focus the nearer must the 
 lens be to the condenser, and if the diameter of the 
 lens be small a large proportion of the rays will not get 
 through at all. 
 
 And this question of focus of the objective is one that 
 must be carefully considered by all who use a lantern. 
 Many are of the opinion that the focal length of the objec- 
 tive used should be so short that the distance of the 
 lantern from the screen should be about the same as the 
 diameter of that screen. In private rooms of small size 
 this may be necessary, if not advantageous, but in larger 
 rooms or lecture-halls a lens which will triple or quadruple 
 that distance is desirable. Much experience of lecture- 
 hall work has led me to the conclusion that a lens of 8-inch 
 focus is more useful as a lantern objective than any other, 
 and it is as well to have one of 10 inches in reserve in 
 case the length of the hall should require it. Let me give 
 my reasons for this choice. I find that the size of sheet 
 most commonly required in rooms used for lecture pur- 
 poses is 15 feet. Some rooms will take an 18-foot sheet, and 
 very few take a larger one than that. But the 15 -foot screen 
 is the one most in request. .Now let us suppose the operator 
 has fitted to his lantern an objective of say 4 \ -inch focus. 
 To cover his 15-foot screen he must plant his lantern less 
 than 20 feet from it, a distance which will land him in 
 the middle of the front seats. His apparatus will 
 
THE BOOK OF THE LANTERN. 
 
 27 
 
 in such a case terribly impede the view of all those 
 behind the lantern, besides causing much disarrange- 
 ment of chairs. But let him use an 8-inch objective, 
 and his lantern can he carried to a distance of 
 35 feet from the screen. This will probably place the 
 lantern quite at the back of the hall. Another point in 
 favour of the latter position is, that if his two lenses are of 
 the same diameter, as most probably they will be, the long, 
 focus lens will admit more light, as already explain e I ; 
 while it will certainly give better definition and less dis- 
 tortion than the shorter focus lens. One more circum- 
 stance in favour of the longer focus lens is, that the lantern 
 is kept more horizontal. When the instrument is close to 
 the screen, unless the floor of the auditorium be inclined, 
 as in a proper lecture -theatre, the lantern must be very 
 much tipped up at its fore-end, so that the disc on the sheet 
 shall be high enough. This raising of the lantern, of 
 course, leads to distortion, unless the screen be inclined 
 towards the lens so as to compromise the matter. With a 
 long-focus lens the distortion from this cause is greatly 
 reduced, and very often it is so slight that there is no need 
 to incline the sheet. I hold the opinion that a good single 
 achromatic lens of long focus is by no means to be despised 
 for lantern work, although a half -plate lens of the portrait 
 type is to be preferred. Such a lens can only be used for 
 the long-distance work. If it is absolutely necessary that 
 the lantern be as near the sheet as possible, then it is com- 
 monly the fashion to use a French quarter-plate photographic 
 lens, — I presume on account of its cheapness. For it is 
 most difficult to select a lens of this description which will 
 
28 
 
 THE BOOK OF THE LANTERN. 
 
 give a flat field, and the ordinary diameter of the back lens 
 of such a combination will not admit the whole of the 
 rays from the condenser : hence we are robbed of light, 
 and very often of the corners of square pictures into the 
 bargain. 
 
 Of late years makers have seen these disadvantages, and 
 have produced lantern objectives which, while they are 
 similar in construction to portrait objectives, are made with 
 much larger apertures at the back. Taking Mr. Dallmeyer's 
 lantern objective as the prototype of these, we find that it 
 consists, like the portrait lens, of two combinations. The 
 back one, next the light, is a convexo-concave of flint, and 
 another of crown glass, separated by a short interval, the 
 two glasses being dissimilar in their curvature. The 
 external form of this combination is a meniscus, its convex 
 surface being next the condenser. The front combination, 
 of smaller diameter, also has the external meniscus form, 
 but consists, like its fellow, of two glasses. 
 
 It must be noted that objectives made for lantern work 
 are not suitable for photography, for the visual and chemical 
 rays are not coincident. I mention this for the sake of 
 those who wish to use the lantern as an aid to their photo- 
 graphic pursuits, in enlarging and so on. It may, therefore, 
 be in some cases desirable for the purchaser to obtain a 
 half -plate portrait lens for his lantern. It will do excellent 
 work, with the limitation already referred to, while at the 
 same time it can be used either for portraiture or for 
 enlarging. For both these uses it is well adapted. 
 
 The rule for calculating the distance of the lantern from 
 the screen in order to obtain an image of a given size will 
 
THE BOOK OF THE LANTERN. 
 
 29 
 
 be found on pnge 95, bat in practice I find it a convenient 
 thing to nse a tape measure. Upon the circular case of 
 this measure I have certain figures to the effect that such 
 and such a lens requires a distance of so many feet to give 
 a 15 or 18 foot disc. The place of the sheet having been 
 decided upon, it is then easy enough to pay out the 
 required amount of tape, and to fix the position of the 
 lantern. 
 
CHAPTER III. 
 
 OXYGEN GAS MAKING. 
 
 HE first requisite for the lime -light is an adequate 
 quantity of oxygen gas, and this chapter will, 
 ' therefore, be devoted to the details of its manu- 
 facture, or rather its separation from those substances with 
 which, in nature, it is associated. For, although the most 
 abundant of all the elements, oxygen does not occur in 
 the uncombined state, and, therefore, the chemist has to 
 be at the pains of separating it from its various yoke- 
 fellows. There are several methods of obtaining this gas ; 
 the greater number of which, being only of experimental 
 interest, may be passed over. 
 
 The gas was originally discovered by Priestley in 1774, 
 and at about the same time, independently, by the Swedish 
 chemist, Scheele. Priestley obtained it by heating mer- 
 curic oxide in a flask, which substance, under such treat- 
 ment, breaks up into mercury vapour and oxygen gas. 
 Such a method is clearly out of the question, when several 
 feet of gas are required for the lime-light. 
 
 Another method, which is applicable when large quan- 
 tities of oxygen are wanted, and which has long been 
 
THE BOOK OF THE LANTERN. 
 
 31 
 
 adopted on a commercial scale, depends npon the action of 
 cobalt on bleaching powder (Calcic hypochlorite). The 
 lime mnst be in the form of a concentrated solntion, and 
 this is best bronght abont by mixing, say, one ponnd of 
 bleaching powder, which is commonly called chloride of 
 lime, with a qnart of water. Stir this mixture and allow 
 it to remain for an hour. Now decant the clear liquid, 
 and pour it upon a fresh pound of lime — stir as before, 
 and strain the product through a calico or flannel bag. 
 Place the liquid in a large bottle, to the cork of which 
 a tube is fitted. Now drop into the liquid, taking the 
 cork out for the time being, a small quantity (say 2 ounces) 
 of a strong solution of cobaltic peroxide, when oxygen gas 
 will be quickly evolved, and will come off through the 
 replaced tube. The evolution of gas is increased by 
 warmth. The same cobalt can be used again and again, as 
 it does not undergo any permanent change. It seems to 
 act merely as a conveyer of oxygen, taking it from the 
 lime, passing it to a higher state of oxidation, and then 
 giving it up again ; any solution of cobalt will answer the 
 purpose. When the gas ceases to come, the residue in the 
 bottle should be diluted with water, and, after having been 
 allowed to rest for some time, the cobalt will settle at the 
 bottom of the vessel. This can then be washed, kept in a 
 moist state, and used over again as often as required. 
 
 But the more general method of preparing the gas is by 
 means of the decomposition of potassic chlorate, and 
 that method I shall now, therefore, describe in detail. 
 
 The lime-light has, in certain quarters, earned the cha- 
 racter of being dangerous, not so much from accidents 
 
32 
 
 THE BOOK OF THE LANTERN. 
 
 which have occurred during its use, but more from certain 
 catastrophes which have taken place during the preli- 
 minary operation of making oxygen gas. There should be 
 no danger whatever about this operation if only ordinary 
 precautions are taken. But some people seem to be unable 
 to do things except in a haphazard manner, and they 
 sooner or later pay the penalty for their carelessness. 
 
 The most important point to begin with is to have 
 proper apparatus ; and by this I do not mean the most ex- 
 pensive, for this is just as often as not faulty in point of 
 
 I 
 
 Fig. 16. 
 
 construction. The articles required are : A retort in 
 which to generate the gas ; a stove for heating that retort 
 (preferably a gas ring-burner) ; a wash bottle, or purifier ; 
 
THE BOOK OF THE LANTERN. 
 
 33 
 
 several feet of good rubber tubing ; and a bag to hold the 
 gas when made. The retort which I prefer is Oakley's 
 pattern, and is made of wrought iron, brazed and rivetted 
 together, and of the form shown in the accompanying 
 sketch, fig. 16. It will be noticed that it is of conical form, 
 and that its lower part, where it rests on the stove, is con- 
 vex in shape. It terminates at the mouth with a brass 
 screw, and in this screw fits a branch, or pipe, which con- 
 veys the gas away as fast as it is generated. An important 
 point in this branch is the arched bend, immediately over 
 the retort, which obviates undue friction, and also prevents 
 any solid particles given off from the retort clogging or 
 stopping up the tube. With that provision one element 
 of danger is avoided. Another point of importance is the 
 •little upright tube, or nozzle, immediately above that same 
 bend. This is merely a short piece of tubing fixed on to 
 the branch, and in which a cork can be fitted. This acts 
 as a simple safety-valve. Should the pressure of gas 
 become too great, the cork will fly out and no damage can 
 possibly occur, except the loss of a very small quantity 
 of gas. 
 
 There are various other forms of retort which are used 
 and recommended by different operators. A cast-iron one 
 is, of course, more . lasting ; but in case of accidental explo- 
 sion, its particles would be as deadly as those of a bomb- 
 shell. But such an explosion should never occur, if 
 ordinary care be taken. With some persons, familiarity 
 with the most dangerous agents so rapidly breeds con- 
 tempt, that they get careless in a very short time. We 
 may suppose that this happened in the case of an optician, 
 
34 
 
 THE BOOK OF THE LANTERN. 
 
 who some years ago was killed by such an explosion of an 
 oxygen retort. 
 
 Many old-fashioned operators nse an iron mercury 
 bottle as a retort, and this, I believe, was the invariable 
 custom when oxygen was procured from manganese per- 
 oxide alone. The* heat required was so great that a thick 
 and lasting receptacle was necessary. But now-a-days, 
 when chlorate is used so universally, the gas comes off at a 
 much-reduced temperature, and a thin retort will last, with 
 care, for about fifty charges. My lantern assistant prefers 
 to use a kitchen digester, which he has had fitted with 
 a pipe and safety cap, and which he regards as a triumph 
 of art, which will not only last his own life-time, but will 
 be handed down to his descendants as an heir-loom. One 
 more word on the subject of retorts. Do not buy a copper 
 one ; it is very expensive, and quickly wears out, and has 
 no advantages whatever. In case a retort should be 
 wanted in a hurry, and cannot be obtained, a common 
 cast iron kettle is a capital substitute for one. Put the 
 chlorate mixture in the kettle, and fasten on the lid with 
 a luting of white lead or clay ; cut a piece of firewood 
 to the correct size, to fit tightly between the lid and 
 the inside of the handle of the kettle, so that no pressure 
 will force it open. Use the spout as a delivery tube of the 
 gas. 
 
 The retort is charged with a mixture of chlorate of potash 
 and oxide of manganese, and the most usual proportions 
 are four parts by weight of the potash to one part of the 
 manganese. 
 
 This is the mixture as given in the various chemical text- 
 
THE BOOK OF THE LANTERN. 
 
 35 
 
 books ; but, as a matter of fact, the exact proportion is not 
 of very great consequence. Indeed, it would seem that if 
 the crystals of potash have mixed with them just sufficient 
 of the black manganese to dirty them well, the mixture 
 will be effective. 
 
 Oxygen gas can be generated from the chlorate alone, 
 but the action is so uncertain that the salt is always mixed 
 with manganese, oxide of iron, or sand. What action the 
 manganese has upon the mixture is not known, for it is 
 a curious fact that, after the operation is over, it remains 
 unchanged, so that it is possible, if one cared to take the 
 trouble, to preserve it and use it over and over again. 
 Where manganese is difficult to obtain, this method may 
 be adopted, but in most towns it can be procured at such 
 a cheap rate that such a course would simply represent a 
 waste of time and trouble. 
 
 The greatest care should be exercised in procuring both 
 components of the oxygen mixture in an unadulterated 
 state. The ordinary commercial chlorate is quite good 
 enough for the purpose, and although it has the disadvan- 
 tage of being contaminated with a certain amount of free 
 chlorine which is given off: in gas-making, it would be 
 a useless expense to employ the pure salt, as used for 
 medicinal purposes. Moreover, the chlorine can be got rid 
 of, as we shall presently see, by simple means. But in 
 most samples of commercial chlorate there are to be found 
 certain foreign bodies, such as bits of straw, bits of wood 
 (from the casks in which the chlorate is originally sold), 
 and other specimens of matter in the wrong place, which 
 would be prejudicial to the operation of gas-making, and, 
 
 J>2 
 
36 
 
 THE BOOK OP THE LANTERN. 
 
 indeed, dangerous ; for carbonaceous material, when mixed 
 with, the chlorate, constitutes a very powerful explosive. 
 (As an instance of this, I may mention that in the greatest 
 explosion of modern times, when thousands of tons of 
 explosive material were fired for the purpose of destroying 
 the " Hell-Gate Rock " at the entrance of New York 
 Harbour, a large proportion of the chemicals employed 
 consisted of chlorate of potash combined with coal-dust.) 
 Before mixing the ingredients together, therefore, the 
 crystals of potash should be carefully picked over by hand, 
 and any unconsidered trifles which have no business to be 
 present should be carefully extracted from it. A little care 
 is also necessary with regard to the manganese. Accidents 
 have happened from lampblack, bone-dust, and other similar 
 compounds, having been substituted (let us hope by acci- 
 dent) for the manganese that was intended to be used. In 
 buying fresh samples, therefore, of manganese, it should 
 be carefully tested, and the best way of doing this is to mix 
 up a small quantity of the potash and the manganese in 
 the proportions above given, and to put them in a test 
 tube, which should be held over the flame of a spirit lamp. 
 If the mixture simply sparkles while oxygen gas is given 
 off at the mouth of the tube (as may be tested by the spark 
 on a blown-out match), the mixture is safe ; but if any- 
 thing in the least resembling an explosion should take place, 
 the manganese is wrong, and must be rejected. Bat the 
 operator is not liable to fall into the error of mistaking 
 lampblack or bone-dust for manganese, because they are, 
 bulk for bulk, so very much lighter than that heavy 
 earth. 
 
THE BOOK OF THE LANTERN. 
 
 37 
 
 The mixture having been made, enough of it must be 
 placed in the retort to give the amount of gas which we 
 require. It will be found that if we allow one pound of 
 chlorate to every 4 feet of gas, it will be about right. 
 Roughly speaking, a bag of 8 feet capacity, — a very useful 
 size, — will take 2^ lb. of the mixture, and it is better to 
 waste a little chlorate than to have a bag which is not 
 quite full. Having charged the retort with the mixture, 
 we can screw on the delivery branch, taking care to insert 
 a washer of leather or asbestos cloth, to prevent any escape 
 of gas between branch and retort. 
 
 In using a new retort, it is always well to blow 
 into it while the branch is fixed in position, so as to be 
 quite sure that there is no leak in the joints which has 
 escaped the maker's attention. Should a 
 leak be discovered, a little white lead will 
 remedy it for the time being. The retort 
 may now be placed on the gas-stove, while 
 its branch rests upon a chair or other 
 support. A tube at least 4 feet long, and 
 of a diameter agreeing with that of the 
 branch of the retort, should be drawn 
 over that branch for about 2 inches. The 
 other end of this tube is to be connected 
 with the wash-bottle. 
 
 The kind of wash bottle which I 
 use, and which I can recommend very 
 highly, is also made by Oakley & Co. Fig. 17. 
 of Bermondsey (fig. 17). It is of half a gallon 
 capacity, and is in reality a glass " Winchester quart " 
 
38 
 
 THE BOOK OF THE LANTERN. 
 
 bottle with a wide neck, such as can be obtained anywhere. 
 Upon this neck fits a disc of lead, perforated with two holes, 
 in which are soldered as fixtures two pewter tubes which 
 bend away from one another at their tops. 
 
 One tube, A, reaches nearly to the bottom of the bottle, 
 and it will be seen that for several inches along its lower 
 part it is perforated with holes. It is this tube which is 
 connected by a rubber pipe to the . retort. The dotted 
 line shows the height to which the bottle must be filled 
 with water. The short tube, B, is the delivery tube of 
 the bottle, and is connected with the gas bag. As a gas- 
 tight connexion between the pewter disc and the bottle, 
 
 Fig. 18. 
 
 there is a thick rubber collar, which is tied on the bottle 
 by means of a piece of strong twine. The larger sectional 
 diagram of the bottle neck (see fig. 18) will assist the 
 reader in noting the arrangements described. In order to 
 prevent any chance of water being thrown up into the gas 
 bag, it is as well to place the bag on a table. Let us sup- 
 
THE BOOK OF THE LANTERN. 
 
 pose that this has been done, and that everything is ready 
 for making the gas. 
 
 The stove should be lighted and turned down almost to 
 its lowest point, for it is as well to begin with a small 
 amount of heat, although I believe that it is the practice 
 of some workers to begin with a full heat, and to turn the 
 supply down when gas commences to come off. The tube 
 is joined to the retort and to the wash bottle ; but the 
 tube joined to the delivery end of the bottle is for the 
 present left free at its other end. After an interval of 
 about five or six minutes, the water in the wash bottle 
 should show by its bubbling that the gas is being generated, 
 but those bubbles are not as yet pure gas, but are partly 
 air which has been contained in the retort, and which is 
 expanded and driven out by the heat. Y» r e must wait 
 some time longer, until these bubbles are given off 
 with regularity, before attempting to fasten the open 
 tube to the gas bag ; and before doing so it is as wij!J 
 to apply the test of the blown-out match to the free end of 
 the rubber tube. If the spark on the match bursts into 
 flame directly it is applied to the tube, we may be sure that 
 gas is coming off in earnest, and we can by a dexterous 
 movement fasten the tube on the tap of the gas bag, at the 
 same time turning on that tap. 
 
 Everything should now go on with regularity and with- 
 out attention, until the bag is nearly half full. During 
 this time it may be noticed that the tube leading from the 
 retort will emit a kind of bubbling noise. This is due to 
 water lodging there which comes from the crystals of 
 potash in the retort. 3y simply lifting this tube up, and 
 
40 
 
 THE BOOK OF THE LANTEKN. 
 
 by giving it a gentle pinch — for half a second— the sudden 
 ontrnsh of gas into the wash bottle will drive off any water 
 that has settled there. When the bag is half full there is 
 generally a lull in the operation, and no bubbles are seen 
 to agitate the water in the wash bottle ; and this opportunity 
 may be taken for turning on a little more gas, but not 
 much more, for presently the oxygen will run off with 
 redoubled vehemence, and if too much flame is applied to 
 the retort the pressure may become too great for the con- 
 nexions, or the cork of the safety valve may fly out. By 
 governing the amount of gas supplied to the stove, the 
 emission of oxygen can be very carefully regulated. (This 
 regulation becomes still easier if a certain amount of 
 common salt be added to the gas mixture in the retort. 
 This should be done just before the retort is charged. The 
 proportions are as follows : — 
 
 Chlorate of potash ... ... ... 8 parts 
 
 Manganese ... ... ... ... 2 „ 
 
 Common salt ... ... ... ... 1^ „ 
 
 all by weight. When common salt is thus added to the 
 gas mixture, the chlorate should be powdered,) 
 
 When the gas bag is full and u as tight as a drum," the 
 various parts of the apparatus used in making the gas 
 must be disconnected, and here some caution is necessary. 
 The first thing to do is to pull the tube from the gas bag 
 and turn off the tap at the same instant. Next remove 
 the tube from the retort, and last of all turn off the gas 
 supply from the stove. Why I say that caution is necessary 
 here, is, because if the gas is turned off before the retort is 
 
THE EOOK OF THE LANTERN. 
 
 41 
 
 disconnected from the wash bottle, the water in the latter 
 may rush back into the retort and cause a small steam 
 explosion. 
 
 This has certainly never happened to me ; but I have 
 heard of cases where such a thing has occurred, and 
 although it would probably be unattended by any serious 
 results, it might lead to a great deal of mess and 
 trouble. 
 
 The retort may be left, until it has become nearly cold, 
 or at any rate until it is cool enough to be handled. The 
 branch pipe should then be unscrewed, and the retort at 
 once washed out with water — warm water by preference. 
 This should be thoroughly done, and many changes of water 
 should be used, until the last wash water comes away per- 
 fectly clean. If the retort is left with the residue of the gas 
 mixture in it, the metal inside is very quickly corroded, and 
 the vessel does not last half so long as it does if it be at 
 once carefully washed. The branch and the india-rubber 
 connecting tubes should be washed out also. 
 
 I have mentioned that the commercial chlorate of potash 
 is contaminated with a certain amount of free chlorine. This 
 soon renders itself evident if the operator places his nose 
 near the delivery tube from the wash bottle when the gas 
 is coming off ; for chlorine gas has a suffocating odour. 
 This is not the only disadvantage which it has in gas 
 making for lantern purposes, for it so acts upon the india- 
 rubber bag and the attached brass work that it quickly 
 leads to deterioration. By placing in the wash bottle 
 water something which will seize hold of this chlorine and 
 detain it, we shall avoid this last difficulty, and the 
 
42 
 
 THE BOOK OF THE LANTERN. 
 
 best substance for the purpose is caustic soda, or 
 potash.. Failing this, common washing soda will answer 
 nearly as well. Caustic soda is rather an awkward thing 
 to travel about with, for it is of a most corrosive nature ; 
 but it should be used in preference to anything else, when 
 gas is made at home. Fragments of disused lime cylinders 
 will also answer well. 
 
 To show that the chlorine is actually taken up by the 
 bag and its belongings, I may mention that if the experi- 
 ment be tried it will be found that the gas when first made, 
 although highly charged with chlorine and inducing 
 coughing and other unpleasant sensations if inhaled, may, 
 after having been left in the bag for an hour or two, be 
 breathed without any ill effect. 
 
 Mr. Fleuss, whose diving and life-saving apparatus de- 
 pends in a great measure upon a supply of compressed 
 oxygen gas, called my attention to the above fact, and told 
 me that he had used gas for breathing purposes which had 
 been freed of its chlorine by remaining in the gas bag for 
 some hours as I have just explained. 
 
 I may mention that the residue left in the retort— and 
 which I have recommended, should be washed out without 
 delay,— consists of chloride of potash, and the manganese ; 
 the latter quite unaltered. It may be useful to point out 
 that the difference between the chlorate and the chloride is 
 easily seen by examining the crystals of each under a 
 microscope. If a little chlorate mingled with water is 
 placed on a slip of glass, and allowed to evaporate, the 
 crystals will have a rhombic form (see A, fig. 19). But if, on 
 the other hand, a solution of chloride of potash be examined 
 
THE BOOK OF THE LANTERN. 
 
 43 
 
 in the same manner, they will be found to be square in out- 
 line, as in B. Should it be desired to use the manganese 
 over again, it must be freed from the chloride by repeated 
 
 changes of water. It will thus be dissolved out, while the 
 manganese remains behind in the form of black mud. 
 This latter must be dried before being again employed in 
 the retort. 
 
 The operation of oxygen gas making is now with many 
 lanternists a thing of the past, for they prefer to buy it 
 ready made. For many years this gas has been supplied, 
 by one or two makers, compressed in iron or steel 
 cylinders. But the price, eightpence per foot, was too 
 high to induce consumers to relinquish the custom of 
 making it themselves. Of recent months, however, the 
 gas has been supplied at half that price, with the result that 
 many prefer to buy it rather than make it themselves. 
 The manufacture of oxygen gas therefore represents " A 
 curious new industry," and under that title I described it a 
 
 Fig. 19. 
 
44 
 
 THE BOOK OF THE LANTERN. 
 
 short time ago in an article in " Chambers's Journal." From 
 that article I will now give the following extract : — 
 
 " Any manual of chemistry will inform us that oxygen 
 is the most widely -diffused element in nature. It enters 
 into the composition of air, of water ; it is found in nearly 
 all earths and rocks ; and forms more than one half of 
 animal and plant life. In fact it is not too much to say 
 that oxygen forms one -half of the globe and its belongings ; 
 but of course it is combined with other elements. Chemists 
 can tell us of a dozen different methods of isolating this 
 gas ; but the one most usually adopted is to subject a salt of 
 potash (potassic chlorate), which is extremely rich in 
 ©xvgen, to heat in a retort, when it quickly parts with that 
 gas, which can be collected in a suitable containing vessel 
 for use. To show the extent to which this salt is used for the 
 production of oxygen, we may mention that we were lately 
 informed by a London dealer that he sold yearly one 
 hundred tons of potassic chlorate, and that he had reason to 
 believe that it was nearly all used for the production of gas. 
 This quantity of the salt would afford, roughly speaking, 
 nine hundred thousand cubic feet of oxygen, and we must 
 not forget that this is the amount dispensed through one 
 dealer only. The natural question which arises as to what 
 purposes this gas is applied, we shall deal with presently. 
 We have preferred to show, first, that there is an enormous 
 demand for oxygen, so that the importance of a new 
 industry for producing it may be at once appreciated. 
 
 " Oxygen forms one-fifth of the air which we breathe, the 
 other four-fifths consisting of an inert gas called nitrogen. 
 And it is important that we should remember that the 
 
THE BOOK OF THE LANTERN. 
 
 45 
 
 mixture of these two gases is a strictly mechanical, not a 
 chemical one. What we mean is this. If it were possible 
 by any means to make visible and magnify the particles of 
 air, we should be able to distinguish the atoms of oxygen 
 and of nitrogen side by side, but in the proportion of one 
 to four. It might be compared to a mixture of pepper and 
 salt, which, although it looks gray to the unaided sight, 
 would, under the microscope, show plainly the independent 
 grains of both constituents. (It is curious to note that a 
 chemical mixture of the two gases, in which their atoms 
 combine to form a new compound, produces that useful 
 anaesthetic, nitrous oxide — laughing gas.) It has long 
 been the dream of chemists that oxygen might be produced 
 direct from the atmosphere by separating its atoms from 
 the atoms of nitrogen with which it is associated but not 
 combined. Indeed, a plan by which this could be accom- 
 plished has long been known, but it happens to be one of 
 those numerous methods, which in theory are perfect, but 
 which when reduced to practice are found to be encumbered 
 by various difficulties. But as a new industry is founded 
 upon the process referred to, and its success has been 
 assured by a patient conquest of the numerous practical 
 difficulties associated with it, we cannot do better than 
 describe it. 
 
 " It was long ago demonstrated by Boussingault that when 
 the substance called baryta, otherwise the oxide of barium, 
 was heated to a low redness, it would absorb oxygen from 
 air submitted to it. He further showed that if this com- 
 pound were then raised to a higher temperature, the 
 oxygen thus absorbed would be given off once more, and the 
 
46 
 
 THE BOOK OF THE LANTERN. 
 
 baryta would be restored to its former condition, ready 
 for a repetition of the action. It would thus seem that 
 there was at hand a process for obtaining from the atmo- 
 sphere an endless supply of its essence, so to speak. But, 
 as we have before hinted, theory and practice are two 
 different things. The process would not* work on a com- 
 mercial scale. All went well at first ; but for some reason 
 or other, the baryta lost its power of recovery, and would 
 not repeat its office of absorbing oxygen. 
 
 " A few years ago, two of M. Boussingault's pupils, Messrs. 
 A. and L. Brin, resolved to carry through a series of ex- 
 periments to find out, if possible, why in this case, practice 
 would not endorse theory. They soon found that the reason 
 why the baryta lost its power of absorbing oxygen was due 
 to certain molecular changes, which ceased to occur if 
 the air supplied was absolutely free from impurities, and if 
 the heat employed for reducing the baryta to its first 
 condition were kept within certain limits. They further 
 found that the necessary temperature might be much 
 reduced if the material were heated in a partial vacuum. 
 Another advantage was found in supplying the air under 
 pressure, in which case the absorption of oxygen from 
 it was much increased. These new conditions were speedily 
 realised in apparatus which was erected in Paris, and which 
 for three years yielded oxygen of the purest description 
 without any renewal of the baryta with which the retorts 
 were charged at the commencement of operations ; and this 
 apparatus was exhibited at the Inventions Exhibition at 
 South Kensington a few years ago. 
 
 " The process having thus been shown to be workable, the 
 inevitable Company was formed ; and oxygen can now be 
 
THE BOOK OP THE LANTERN. 
 
 47 
 
 obtained in any quantity at a cheap rate by any one who 
 requires it. Brin's Oxygen Company has established ex- 
 tensive works at Westminster, where, by a system of 
 retorts and air-pumps, the business of abstracting oxygen 
 from the air is continuously carried on. The gas is carried 
 to a holder, in which it is stored ; and is drawn from that 
 holder and compressed in steel cylinders for the use of the 
 Company's customers. These cylinders are so strong, that 
 one having the capacity of little more than a cubic foot of 
 gas will hold forty feet when that gas is compres ed within it. 
 These bottles, placed in wooden cases, are now sent over 
 the kingdom by rail and carrier." 
 
 The gas is of the utmost purity, and is largely used for 
 charging water for drinking purposes, as a remedy for 
 certain diseases. 
 
 The following table gives the sizes of the cylinders 
 supplied, together with their length and weight : — 
 
 Solid Drawn Steel Cylinders Charged to 120 
 Atmospheres. 
 
 Cubic 
 Contents in 
 feet. 
 
 3 
 6 
 12 
 40 
 80 
 100 
 
 Diameter 
 in 
 inches. 
 
 4 
 
 H 
 51 
 
 Length 
 
 in 
 inches. 
 
 7 
 11 
 
 20 
 30 
 60 
 78 
 
 Weight, 
 
 case 
 included. 
 
 
 lb. 
 
 9 
 
 >> 
 
 15 
 
 ?> 
 
 43 
 
 » 
 
 72 
 
 >> 
 
 84 
 
 
48 THE BOOK OF THE LANTERN. 
 
 Low Pressure Cylinders Charged to 10 Atmospheres 
 
 Cub. contents. 
 
 Diameter. 
 
 Length. 
 
 Weight. 
 
 10 ft. 
 
 u „ 
 
 10 in. 
 10 „ 
 
 20 in. 
 36 „ 
 
 391b. 
 
 68 „ 
 
 Each cylinder is fitted with a tap to regulate the flow 
 of gas, which tap has a nipple over which the rubber 
 tubing can readily be drawn. The 
 advantage of using a bottle instead of 
 a bag in the one point of bulk is re- 
 markable, as may be seen by the above 
 table. Thus, six cubic feet, which will 
 be sufficient for an hour and a half's 
 entertainment, is contained in a re- 
 ceptacle about the size of a champagne 
 bottle, and which can be placed in 
 the empty lantern-box during use. 
 The amount of gas in a bottle can be 
 readily ascertained by the use of a 
 proper pressure gauge. In fig. 20 one 
 of these cylinders is shown with the 
 regulator and pressure gauge attached. 
 The latter is of the form commonly 
 used on steam engines, and is known 
 as Bourdon's pressure gauge. It depends for its efficiency 
 on the action of internal pressure upon a curved tube of 
 oval section. The greater the pressure the straighter the 
 tube becomes, and this movement is communicated by 
 simple gearing to the index-finger. The following table 
 will be found useful to those who employ compressed gas :— 
 
THE BOOK OF THE LANTERN. 
 
 49 
 
 Table showing the amount of gas in various-sized 
 cylinders, as shown by gauge. the gauge indi- 
 cation is in large type, and the corresponding 
 amount of gas in smaller type. 
 
 CAPACITY OF BOTTLES. 
 
 3 ft. 
 
 6 ft. 
 
 12 ft. 
 
 40 ft. 
 
 80 ft. 
 
 lOOft. 
 
 ft. 
 
 ft. 
 
 ft. 
 
 ft. 
 
 ft. 
 
 ft. 
 
 1800-3 
 
 1800-6 
 
 1810-12 
 
 1800—4O 
 
 — 80 
 
 — 100 
 
 1500-21 
 
 1500-5 
 
 1650-H 
 
 1710-38 
 
 — 76 
 
 — 95 
 
 1200—2 
 
 1200-4 
 
 1500-1O 
 
 1620-36 
 
 — 72 
 
 — 90 
 
 900-H 
 
 900-3 
 
 1350- 9 
 
 1530-34 
 
 — 68 
 
 — 85 
 
 600-1 
 
 600-2 
 
 1200- 8 
 
 1440-32 
 
 — 64 
 
 — 80 
 
 300-O* 
 
 300-1 
 
 1050- 7 
 
 1350-30 
 
 — 60 
 
 — 75 
 
 
 
 900- 6 
 
 1260-28 
 
 — 56 
 
 — 70 
 
 
 
 750- 5 
 
 1170-26 
 
 — 52 
 
 65 
 
 
 
 600- 4 
 
 1080-24 
 
 — 48 
 
 — 60 
 
 
 
 450- 3 
 
 990-22 
 
 — 44 
 
 — 55 
 
 
 
 300- 2 
 
 900-2O 
 
 — 40 
 
 — 50 
 
 
 
 150- l 
 
 810-18 
 
 — 36 
 
 — 45 
 
 
 
 
 720-16 
 
 — 32 
 
 — 40 
 
 
 
 
 630 - 14 
 
 — 28 
 
 — 35 
 
 
 
 
 ^40 12 
 
 — 24 
 
 — 30 
 
 
 
 
 450—10 
 
 — 20 
 
 — 25 
 
 
 
 
 360- 8 
 
 — 16 
 
 — 20 
 
 
 
 
 270- 6 
 
 — 12 
 
 — 15 
 
 
 
 
 180- 4 
 
 — 8 
 
 — 10 
 
 
 
 
 90— 2 
 
 — 4 
 
 
 E 
 
CHAPTER IV. 
 
 LIME-LIGHT JETS, BAGS, PRESSURE BOARDS, ETC. 
 
 HERB are three forms of jets for the lime-light, 
 namely, the oxycalcium, the blow-through, or 
 safety form, and the mixed jet. The simplest 
 of all is the first named. 
 
 The oxycalcium jet consists of a spirit-lamp, which is 
 fed from a little reservoir at the back of the lantern. The 
 spirit furnishes the necessary hydrogen, and through its 
 flame a jet of oxygen is passed, and impinges upon a 
 cylinder of lime placed just at the other side of the wick. 
 This lamp will well illuminate a disc of about ten feet in 
 diameter with a clear, white light. It has the advantage 
 of simplicity, but presents one difficulty in the circum- 
 stance that the lantern must be kept perfectly level. If it 
 is inclined backwards, the spirit cannot flow to the point of 
 combustion, and if it is inclined forwards the fluid may 
 flow too rapidly towards the wick. In some forms of 
 oxycalcium lamp this is obviated by a special construction 
 of the spirit cistern, which is furnished with an automatic 
 valve for governing the supply of fluid to the wick. The 
 wick will rapidly become charred if the stream of oxygen 
 
THE BOOK OF THE LANTERN. 
 
 51 
 
 is allowed to impinge upon it; it should be so adjusted 
 that the gas just escapes touching it •while passing through 
 its flame. This form of lamp is sometimes fitted with a 
 wick of asbestos, which well resists the greatest heat that 
 can be brought against it. The oxycalcium lamp is value 
 able where no hydrogen gas can be obtained, and, while 
 far more powerful than a mineral oil flame, can hardly be 
 considered sufficiently powerful for use in a public lecture 
 hall. It is used in many of the hospitals in conjunction 
 with a simple form of lantern for throwing light upon 
 patients during certain operations. 
 
 Before I reached the mature age of 
 twelve I had made oxygen gas by 
 nearly every available method, and had 
 used in this work sundry blacking 
 bottles, ginger-beer bottles, gun-barrels, 
 and gas-pipes, employing as gas-bags 
 disagreeable bladders fresh from the 
 butcher's. It is a wonder to me that 
 I was never blown skywards, but 
 blown-up in a figurative sense I often 
 was. It is now my turn to assume the 
 position of "stern parent," but in doing 
 so I soften towards the juvenile ex- 
 perimenter in memory of my own 
 misdeeds. Perhaps a description of 
 my first lime-light jet, made at 
 the cost of a few pence, of two FlG - 21 • 
 
 gasfitters' blowpipes, will answer the purpose better than 
 anything else, of demonstrating the principle of the ordi- 
 
 e 2 
 
52 
 
 THE BOOK OF THE LANTERN. 
 
 nary blow- through, or safety jet, which, on the whole, is 
 the best form of burner for amateurs to adopt (see 
 fig. 21). 
 
 A is a piece of wood rounded off at one side of its upper 
 end, as shown, so as to accommodate its form to the bent 
 blow-pipe, which is marked O, for this pipe is the conveyer 
 of the oxygen. This is fixed in position by loops of wire, 
 passing through holes in the wooden support. Upon 
 the other side of this support is bound in like manner 
 another blow-pipe, which has its fine nozzle cut off. This is 
 marked H, for hydrogen, and is connected when in use, 
 by means of an india-rubber tube, to the house-gas supply. 
 The upper points of these two pipes are so adjusted that 
 the oxygen gas will blow through the flame from the H 
 pipe, on to the lime cylinder L. A jet formed on this 
 principle has the word "safety" linked to it, because the 
 two gases are kept quite separate until they meet at the 
 point of com bustion. Singly, they are innocent of harm ; 
 but mixed, except under certain precautions, as we shall 
 presently see, they form an explosive compound second 
 only to gunpowder. 
 
 To say that the arrangement thus described and illus- 
 trated is anything but faulty in construction would be 
 absurd, but I will say that there are many jets sold of 
 far more pretension which give no better light, and cost 
 as many florins as this one does pence. But as I have 
 said, 1 have described it as a ready means of explaining the 
 principle of the blow-through jet. I have tried many 
 different patterns of jets, and have selected the one illus- 
 
THE BOOK OF THE LANTERN. 
 
 trated at fig. 22 as being by far the most perfect of any of 
 the blow-through type. 
 
 Fig. 22. 
 
 In selecting such a jet the buyer should be careful to 
 see that the orifice of the 0 pipe is sunk within that which 
 
 1 1 0 CZZ3 
 
 Fig. 23. 
 
 supplies the hydrogen, as shown at M. In many jets the 
 two pipes are brought to the s&me level, but the form I 
 
54 
 
 THE BOOK OF THE LANTERN. 
 
 illustrate gives a much better light, probably because the 
 two gases are better mixed before reaching the lime. L is 
 the pin upon which the bored lime cylinder rests, and it 
 can be moved to or from the jet by means of the shifting 
 .screw S. K is a rod which extends outside the lantern, 
 and which is for the purpose of turning the lime cylinder. 
 The form shown is one commonly met with, and it consists 
 of a rod connected with a bent spiral of wire. I have 
 long ago discarded this arrangement, as it works by fitful 
 starts, and jerks the lime round instead of moving it by 
 degrees. The form of lime-turner attached to the jet 
 shown at fig. 23 is the one to select. 
 
 This form is known as the mixed jet, by which the most 
 powerful form of lime-light is obtainable, but, as already 
 pointed out, it is not so suitable as the one before described 
 for amateur use. Both gases must be under the same 
 pressure, therefore two bags for 0 and H respectively 
 must be employed, usually under the same pressure boards. 
 The jet is safe enough in skilled hands, but is not so, 
 unless care be taken with every detail. The two gases 
 are led to the box or chamber W, where they mix, and 
 impinge upon the lime through the single jet J. D repre- 
 sents a recent improvement which I believe was first 
 suggested by that very good authority on lantern matters, 
 Mr. Lewis Wright ; it deals with the manner of turning 
 the iime cylinder, so that it may not become pitted by the 
 continued action of the jet upon one spot. The primitive 
 plan was to open the lantern door at frequent interval*, 
 and to give the hot lime a hasty touch with the finger. 
 Next the lime pin was furnished with a screw which could be 
 
THE BOOK OF THE LANTERN. 
 
 55 
 
 worked outside the lan fcern, so that it was turned and raised 
 by the same action. But, strange to say, the screw was of 
 so fine a pitch, as in fig. 22, that by one revolution the 
 pitted part of the lime was once more brought under the 
 influence of the jet. In Mr. Wright's arrangement, which • 
 I have long ago adopted, the screw is a spiral, which 
 during one revolution raises the lime quite a quarter of an 
 inch. This plan has still further been improved upon by 
 the addition of a nicked wheel, which prevents the lime 
 being turned by the operator more than is necessary for 
 the time being. This addition is known as "Newton's 
 Improved Check-action Lime-movement." The same firm 
 of opticians have carried out a still further improve- 
 ment devised by Mr. Andrew Pringle. This consists 
 of what is called a " cut off," and is applicable only to 
 the mixed gas jet. It gives the operator the means of 
 setting his jet so that the gases are giving the best pos- 
 sible light, and then by the turn of an extra tap cutting 
 them off, with the exception of a small supply of the 
 hydrogen which keeps burning. He can, therefore, adjust 
 his lights beforehand, and feel, confident that a turn of 
 the tap will once more render them at their best at a 
 moment's notice. 
 
 There is certainly room for improvement in the manner 
 in which lime jets generally are supported in the lantern. 
 A metal tray, sliding in grooves, forms a base board, at the 
 end of which is an upright rod of iron which, during use, 
 projects at the back of the lantern. Upon this vertical 
 rod the whole jet can be moved up or down, and can be 
 clamped in position by means of a couple of screws, with 
 
56 
 
 THE BOOK OF THE LANTERN. 
 
 milled heads. The arrangement is by no means a good 
 one, but it is one of those simple things which have been 
 unheeded by the many, and manufacturers generally have 
 adopted it without perhaps thinking how inconvenient it is 
 in practice. In the first place, the jet is apt to slip either 
 downwards bodily, or to one side or the other by a careless 
 touch of the operator's hand. In either case, such a shift- 
 ing of the light out of the optical axis causes the disc to be 
 darkened until the jet be readjusted, which cannot be 
 easily done without opening the door of the lantern and 
 letting out a flood of light in the darkened room. There is, 
 besides, much trouble in getting the jet central, which could 
 easily be avoided by a more rational arrangement. Mr. 
 Pumphrey, of Birmingham, has devised for the purpose a 
 horizontal and vertical rack motion, very like the same 
 movement which is attached to the mechanical stage 
 of a microscope, but it is somewhat expensive, and 
 
 Fig. 24. 
 
 adds extra weight to the lantern. There is no doubt, 
 at the same time, of its effectiveness and conveni- 
 
THE BOOK OF THE LANTERN. 
 
 57 
 
 ence. A simpler plan is that recently introduced by Mr. 
 Steward, and shown at fig. 24. In this case a tongue of 
 metal is fixed to the supply pipes of the jet, and this 
 tongue has a slot in its centre, which engages a vertical 
 pin on the lantern tray. This pin is threaded so that a 
 couple of discs can firmly clamp the metal tongue when 
 the jet has been once centered. Once clamped in this 
 way, the jet cannot be moved until it is released by 
 unscrewing the discs. 
 
 Another valuable improvement is represented by Wood's 
 lime cylinder shield, which is shown, fitted to a jet, at 
 fig. 25. It consists of a metal cylinder, rather larger than 
 
 Fig. 25. 
 
 the lime, in which the latter is free to turn. There 
 is an opening in front, through which the incandescent 
 lime can throw its light towards the condensing lens. 
 In jets, generally, the lime is quite exposed, and unless it 
 be gradually heated will often crack to pieces, by the 
 
58 
 
 THE BOOK OF THE LANTERN. 
 
 unequal expansion which it undergoes. The shield pre- 
 vents this by confining the heat within a narrow area 
 around it, at the same time keeping the lantern itself com- 
 paratively cool. Mr. Wood tells me that there is an 
 undoubted gain of light from this conservation of heat in 
 and around the lime cylinder. The shield, moreover, does 
 much to obviate a by no means uncommon accident, 
 namely, the fracture of the valuable condenser itself from 
 a flame deflected towards it from a cracked or much-pitted 
 lime cylinder. 
 
 The most general method of storing the gases required 
 for the lime -light is by means of bags, which should be of 
 the best quality. It is necessary to caution the beginner 
 on this point, for I have known cases where a perfectly 
 new bag, fresh from the maker, has been found, on trial, 
 to leak badly. I cannot say that such an unpleasant cir- 
 cumstance has happened to myself, for I go to a maker 
 upon whom I can rely. It may possibly have been the 
 fault of the operator himself, who did not take the pre- 
 caution to warm the bag before use. For these bags in 
 winter time — when of course they are most generally used 
 — get stiff and hard, and if not of good quality are apt 
 to crack, unless carefully warmed before use. 
 
 The best bags are made of un vulcanised rubber, covered 
 on the outer side with twill, and on the inner side w r ith coarse 
 canvas. This rough canvas serves a double purpose — it 
 gives strength to the bag and also prevents the inner sides 
 sticking together when the bag is empty. After a bag has 
 been in use some time, the presence of this canvas makes 
 itself evident by a quantity of fibrous matter which 
 
THE BOOK OF THE LANTERN. 
 
 59 
 
 comes out of the jet, and which I have been gravely told 
 by an ignorant operator is a deposit left by the oxygen 
 gas ! 
 
 The bag is furnished with a brass stop-cock, which is 
 apt to get so stiff as to be very difficult to turn. For this 
 reason the screw holding the plug of the tap should be 
 undone frequently, and the plug touched with a little oil, 
 vaseline, or tallow. This stiffness is due to free chlorine, 
 which, as is explained in the chapter on oxygen making, 
 is often present in that gas. The purchaser of a bag is of 
 course to a great extent at the mercy of the trader, and 
 many inferior, bags are sold to the unwary. But a few 
 inquiries among those who know what a good bag should 
 consist of will soon inform the buyer where he can pur- 
 chase one which is reliable in quality. Certainly too rigid 
 an economy should not be exercised in this particular part 
 of the lantern equipment. 
 
 The gas-bags are made wedge-shaped so that they 
 can be placed between sloping pressure boards fur- 
 nished with weights. I have heard of careless operators 
 who are content to trust to luck for finding suitable 
 boards for their gas-bag, or bags, when they arrive at the 
 scene of operations. This is, of course, a most repre- 
 hensible proceeding. But should an exhibitor be so placed 
 that he cannot obtain boards, a blackboard, such as can 
 be found in any schoolroom, can be used for the purpose, 
 provided that it is fastened by staples to the floor. It 
 must also have a shelf at the other end, on its upper side, 
 against which the weights can rest. This is but a make- 
 shift, and one which should only be resorted to in an 
 
60 
 
 THE BOOK OF THE LA.NTERN. 
 
 emergency. In some of my experimental lectures, where 
 I require a lime-light for occasional use on the plat- 
 
 Fig. 26. 
 
 form, I carry with me a small bag holding only three feet 
 of gas, and a special form of pressure board which I have 
 designed for the purpose. It consists simply of two pieces 
 of inch board, each pierced on one edge with corresponding 
 Centre-bit holes three-quarters of an inch in diameter- 
 Into these holes fit half a dozen round rods of pine. A 
 couple of pieces of wood screwed to the under edge of one 
 of these pieces of board serve as a support to the twenty- 
 eight-pound weight employed. The lower part of this 
 skeleton pressure board is furnished with a couple of bolts 
 which shoot out, and into two screw eyes, fastened to the 
 floor. The whole arrangement will be rendered clear by 
 the annexed sketch (fig. 26). I merely describe it here in 
 the hope that it may be as useful to others as it has been 
 to myself. 
 
THE BOOK OF THE LANTERN. 
 
 61 
 
 For the blow- through jet only one pressure board is 
 required, and perhaps a better form cannot be used than 
 a couple of thin boards hinged together with a simple 
 ledge, or shelf, above, also on hinges, for the reception of 
 the weights. But for the mixed jet another arrangement 
 is necessary. In this latter case the two gases must be 
 under equal pressure. Two pairs of boards, like those 
 just described, may be used side by side, but they will 
 occupy a great deal of space, and a double supply of 
 weights will become necessary. This last objection is, 
 perhaps, more cogent than the first, for in these days of 
 patent weighing machines the old-fashioned 56-pounders 
 are becoming quite scarce. It is, therefore, much better 
 to use a pair of boards, so constructed that they will 
 embrace both bags — one set of weights being all-sufficient 
 for the two. A further advantage of this arrangement is 
 that both bags are under the same pressure, and additional 
 weights put on during performance cannot affect one bag 
 to the prejudice of the other. Dangerous accidents have 
 before now happened when independent pressure boards 
 have been in use, from the weights having been in- 
 advertently shifted from one gas, while the other has been 
 left under full pressure. 
 
 To Mr. Maiden is due the credit of having first designed 
 a pair of pressure boards which would hold both bags 
 under one set of weights, and the arrangement which he 
 suggested is that which is now commonly adopted by 
 opticians, and figured in their catalogues. I myself 
 use a modified form of these pressure boards, and 
 as J have given much thought to the subject before 
 
62 
 
 THE BOOK OF THE LANTERN. 
 
 having them constructed, and as they answer their purpose 
 most perfectly, I will describe them. 
 
 They are what are called skeleton-boards ; that is to 
 say, they consist of frames filled in with sail-cloth. This 
 mode of construction saves a great amount of weight. 
 The wood- work is of best pine, 1| inches thick, and is 
 mortised at every joint. Referring to fig. 27, it will be 
 seen that the upper frame, is furnished with a couple of 
 
 
 f ' N 
 
 1 ' ' 1— 
 
 I® S 
 
 © 
 
 6 <S 
 
 *' 
 
 '•o 
 
 
 
 &' 
 
 7 
 
 \ 
 
 
 Fig. 27. 
 
 Fig. 28. 
 
 hinged shelves, between which the weights are placed. 
 These shelves are made of hard wood, so that they will 
 not readily break. The lower frame (fig. 28) has let into it 
 a smaller frame, which, when the boards are not in use, is 
 bolted into the main frame for travelling. But when in 
 use, this lower frame is caused to fall downwards, so that 
 it acts as a support for the pressure-boards, keeping them 
 at the right angle. The hinges which connect the two 
 
THE BOOK OF THE LANTERN. 
 
 63 
 
 frames together are of wrought iron and of very solid 
 construction ; for they have to bear some amount of strain. 
 It will be noticed that the sail-cloth is made in two pieces, 
 with eyelet holes along the edges where they meet, so that 
 by means of strong cord they can be laced up and rendered 
 as tight as a drumhead. 
 
 Between the two frames there is secured a sheet of sail- 
 cloth, which is nailed down to the lower board at the 
 hinged end. In the centre of its other extremity is sewn 
 a flattened ring of galvanised iron. Where the sail-cloth 
 is nailed to the woodwork zinc roofing nails should be 
 used, for they will never rust. To the end of the 
 lower frame which is farthest away from the hinges 
 is nailed a strong leather strap, about six feet long, and 
 when the bags are in position this strap is passed through 
 the flattened ring on the midway sheet of sail-cloth, and 
 then through a corresponding opening on the upper frame, 
 where it is secured with a buckle. By means of this strap 
 the two bags are kept in place, while the sail-cloth sheet 
 between them also helps to prevent them slipping back- 
 wards. 
 
 It is customary to place the hydrogen bag below and the 
 oxygen one above, but I am not aware that there is any 
 advantage in so doing. Certainly I have met with operators 
 who prefer to reverse their positions, and seemingly without 
 any disadvantage. 
 
 The taps on the bags should have a large bore, and the 
 tnbes which serve to connect them with the lantern should 
 also be of good size. The amount of weight on the 
 bags is governed to some extent by the size of disc re- 
 
64 
 
 THE BOOK OF THE LANTERN. 
 
 quired to be shown. Using a disc of from 15 to 18 feet in 
 diameter the exhibitor will do well to commence when the 
 bags are full with two half-hundredweights on his pressure 
 boards. But when the gas has been so much used that the 
 upper board gets nearly horizontal the pressure will be 
 lessened, and the light will suffer to some extent. When 
 this happens, the experienced operator will place another 
 half -hundredweight in position, and the increased bright- 
 ness of the picture will quickly show the advantage of so 
 doing. 
 
 When the gas or gases are drawn direct from steel 
 cylinders, or bottles, if a double or triple lantern is in 
 use, some form of regulator must be employed. The first 
 introduced, and perhaps the most perfect, is that patented 
 by Messrs. Oakley & Beard. 
 
 Before proceeding to describe this important new de- 
 parture in lantern working, it may be as well to point out 
 one or two difficulties which are incidental to the ordinary 
 method of storing the gases required in india-rubber bags. 
 So far as the writer knows, one of these difficulties has 
 never been recognised in print. This difficulty is com- 
 prised in the fact that any kind of gas, if kept in an india- 
 rubber bag, quickly deteriorates. By the phenomenon 
 known by the term endosmose, two gases separated by a 
 porous diaphragm will effect a mutual exchange. Take 
 the case of an ordinary india-rubber tube used for a table 
 lamp or gas stove. How quickly it begins to smell. 
 This is nothing else but the gas escaping through the 
 india-rubber, and carrying on an exchange with that other 
 gas — the air — which is outside. It would be interesting 
 
THE BOOK OF THE LANTERN. 
 
 G5 
 
 to know how quickly this exchange takes place in the case 
 of a bag of oxygen; but, as an experienced worker, I 
 have no hesitation in saying that there is a marked 
 deterioration in the quality of the lime-light, if the oxygen 
 gas used has been kept for only 24 hours in a bag 
 instead of being freshly made. The same rule will 
 apply to the hydrogen gas in a greater degree, for the 
 hydrogen passes through a porous diaphragm far more 
 rapidly than can oxygen. But, in practice, the H bag is 
 filled from the nearest gas-tap immediately before it is 
 wanted. (Mr. Fletcher, of Warrington, has patented a 
 method of preventing the smell of gas-tubes, by inserting 
 a partition of tinfoil between the two layers of india-rubber 
 which compose the tube. This foil stops the smell, by 
 stopping endosmose. The same principle might, of course, 
 be applied to gas-bags. Here is a hint for manufacturers.) 
 Other objections to the use of gas-bags are found in their 
 initial expense, and the necessity for constant renewal, 
 their bulk, and their liability to mechanical injury. In 
 spite of these defects, I have always preferred to use gas 
 in bags, rather than gas compressed in cylinders. My 
 reasons for this choice I will now give. 
 
 If the gases are compressed in cylinders, there is a 
 great saving in trouble, as well as in bulk of apparatus ; 
 but I have hitherto set my face against them for the 
 following reasons: — 1. The pressure is so great, that the 
 india-rubber tubes are apt to blow off ; and, if tied on, may 
 burst. 2. The light cannot be regulated at the jets and 
 by the taps provided for that purpose, but the taps must 
 be turned fully on, and the outrush of gas roughly 
 
 F 
 
66 
 
 THE BOOK OP THE LANTERN. 
 
 regulated — a very difficult matter — by the screw plug on 
 the nozzles of the bottles. 3. The operator at the lantern, 
 even if he succeed in thus procuring the delivery of the 
 proper amount of oxygen and hydrogen respectively, must 
 stoop down to do so, and, for the time, neglect other duties. 
 4. The pressure is constant ; and, therefore, if a double or 
 treble light is suddenly wanted — as in the case of biunial 
 and triple lanterns - the amount of gas measured out for one 
 light, must serve for two or three, as the case may be — 
 and all suffer. 5. As the bottles gradually empty, the 
 pressure sinks; and, therefore, the screw-plugs have to be 
 opened several times during an evening's work. Every 
 time this becomes necessary, there is a likely chance of too 
 much being turned on, and the tubes being blown off. It 
 is, therefore, seen that, although bags are troublesome, 
 bottles possess many disadvantages which would make any 
 careful operator pause before he adopted them. These 
 disadvantages, however, entirely disappear when the 
 bottles are used with regulators. 
 
 The action of the regulator can be understood without 
 much difficulty by reference to the annexed sectional 
 diagram, fig. 28. The screw-thread d s at the bottom of the 
 drawing, is where the casting D fits upou the bottle of 
 compressed gas ; d l is the delivery tube, governed by the 
 stop-cock d 2 , B is a base-plate supporting the most im- 
 portant part of the apparatus, and E E standing upon it 
 is merely a casing to protect the enclosed part from injury. 
 A A are bellows made of the finest rubber, and of a form 
 not unlike the bellows of a camera, only that it is circular. 
 Th > top of the bellows is heavily weighted, so that its 
 
THE BOOK OF THE LANTERN. 
 
 67 
 
 natural tendency is to remain compressed. This top is 
 fnrnished with a collar C 1 , having a screw-thread in which 
 the screw pillar F can easily turn. It will be noticed 
 that the thread of the screw is coarse, so we may call 
 it an Archimedean screw. At its lower part is a fine, and 
 
 Fig. 23. 
 
 therefore slow-motion screw, which works in the collar c. 
 Now, let ns see how beautif nlly this donble-screw motion is 
 applied to regnlating the delivery of the highly-compressed 
 gas. As soon as the gas emerges from the bottle it passes 
 
 f 2 
 
68 
 
 THE BOOK OF THE LANTERN. 
 
 between the space which is open between the valve f and 
 the valve seat d. It then rashes into the bellows above, 
 which become gradually raised by its pressure. As the 
 bellows rise the screw pillar F is quickly turned in its 
 socket, and gives a slow motion to the screw below. The 
 effect of this movement is to bring the valve f down on its 
 seat d, and the supply of gas is cut off. But in practice 
 the gas will be drawn off from the delivery tube d l so 
 that the bellows will soon be compressed once more. As 
 the bellows move downwards, the screw F acts in the reverse 
 manner, so that the valve F is now raised, and a fresh 
 supply of gas enters the bellows. In this way the bellows 
 are constantly rising and falling. If but one lime-light is 
 in use, and the delivery of the gas is therefore regular, 
 the bellows will be almost stationary, for they will auto- 
 matically adjust the valve F, so that just enough gas, and 
 no more, will pass through the opening. But if two or 
 three lights are in use, and sometimes only one, and per- 
 haps immediately afterwards all three are requisitioned, 
 then the little bellows will have a more lively time of it. 
 In both cases the regulator will deliver the quantity of 
 gas which happens at the moment to be required. 
 
 Some time ago I contributed to The Camera, an illus- 
 trated article showing how, by the use of a small gas-bag, 
 A, the outflow of gas from a cylinder might be regulated. 
 The bag was in this case made to raise a lever as it 
 filled, thus cutting off the gas supply from the bottle, until 
 the bag was partially emptied, when the action was repeated. 
 Shortly after the publication of this article a self-acting 
 valve on the same principle was introduced. This valve 
 
THE BOOK OF THE LANTERN. 
 
 69 
 
 is shown at fie:. 29. A is the loose nut by which it is 
 attached to the gas-bottle ; B, the 
 valve proper, which is governed 
 by the spring lever D. The 
 tendency of this sprjng is to keep 
 the bag shut, and when in that 
 position the tap is open. The 
 gas pressure, however, quickly 
 inflates the bag, and turns off the 
 gas supply. The delivery pipe, 
 E, is connected with the lantern. 
 The apparatus is small and com- 
 pact, and works well. 
 
 It may be noted here, that there is a distinct gain in 
 using pure hydrogen, instead of the carbureted gas 
 from the main, although its employment undoubtedly 
 leads to extra trouble and ex- 
 pense. The most convenient 
 way of making this gas in small 
 quantities is by treating scrap 
 zinc with dilute acid. A con- 
 venient apparatus is that shown 
 in the diagram, fig. 30. It was 
 devised some years ago by Mr. 
 Pumphrey, and published in one 
 of the Photographic Annnals. 
 It consists of a copper container, 
 in which is an inverted box with 
 a delivery tube and tap attached 
 to it for drawing off the gas as 
 it is generated. This inner box 
 
 Fig. 30. 
 
70 
 
 THE LOOK OF THE LANTERN. 
 
 has a removable perforated shelf fitted to it, and the box 
 itself is so arranged that it can be wedged tightly in its 
 place. The shelf is to hold the necessary supply of 
 scrap zinc, and as the acidulated water attacks the 
 metal, hydrogen is rapidly given off, until the water is 
 forced by the pressure of the gas below the shelf, and 
 the action ceases. It is again renewed when gas is 
 drawn off from the tap, for then the water again rises 
 to the zinc, and a fresh supply is generated. This 
 apparatus is clearly a modification of the Dobereiner 
 lamp, in which the gas generated in this manner impinges 
 upon and renders red-hot a pellet of spongy platinum. 
 At a recent lantern exhibition at the Crystal Palace, where 
 a 30 -foot screen was used, pure hydrogen from a bottle 
 fed the lime-light. On one occasion ordinary coal-gas was 
 substituted, with a loss of light which was estimated by 
 those well qualified to form a judgment, at no less than 
 25 per cent. 
 
CHAPTER V. 
 
 THE LIME-LIGHT AND ITS MANAGEMENT. 
 
 [HE lime-light was discovered about the year 1826 
 by Lieut. Drummond, R.E., during the progress 
 of the Ordnance' of Ireland Survey, when the 
 want of some method of signalling between distant stations 
 was much felt. As originally constructed, Drummond's 
 lamp was very different to the convenient forms of lime jet 
 now in use. It consisted of a blow-pipe, which impinged 
 upon a ball of lime about as big as a marble. This lime 
 ball did not last more than half an hour, but when spent 
 another took its place automatically. The lime ball was 
 placed in the focus of a parabolic silvered-copper reflector. 
 With this apparatus, the light was visible from Antrim in 
 Ireland, to Ben Lomond in Scotland, a distance of ninety - 
 nre miles as the crow flies. Upon another occasion, the 
 light from the Drummond lamp was distinguishable at a 
 distance of one hundred and twelve miles. 
 
 When manufactured limes cannot be obtained, a piece 
 of limestone fresh from the kiln can be sawn roughly to 
 
72 
 
 THE "BOOK OF THE LANTERN. 
 
 the cylindrical form, and rubbed down with, a file ; or a 
 piece of good hard chalk will serve, if there is nothing 
 better at hand. The following mixture has been recom- 
 mended as one from which a hard substance can be 
 moulded which will take the place of the usual lime 
 cylinder : — 
 
 Precipitated Chalk 4 parts. 
 
 Heavy Magnesia Carbonate 1 part. 
 
 Mix to paste with gum-water, and mould to form. 
 
 Of late years some new limes have been introduced, with 
 the trade-mark ' ' Excelsior." These will do admirably for 
 the blow-through jet, but will not (at any rate in my 
 hands) withstand the attack of a powerful mixed jet. I 
 have always regretted that I cannot use them, for they are 
 uniform in size, are accurately turned and bored, and are 
 packed in a very convenient manner. A good hard 
 material which will last for several hours, and which is not 
 affected by damp, is a thing that is much wanted for lime- 
 light working. The following extract from Lieut. Drum- 
 mond's paper in the Philosophical Transactions, 1826, is 
 interesting, as showing that the discoverer of the lime -light, 
 made trials of various substances, but found lime to be the 
 best : — 
 
 " The results of several trials made at the commencement, 
 gave for — 
 
 Lime 37 times 
 
 Zirconia 31 times 
 
 Magnesia 16 times 
 
 the intensity of an Argand burner. The oxide of zinc was 
 
THE BOOK OF THE LANTERN. 
 
 73 
 
 also tried ; but besides wasting away rapidly, it proved 
 inferior even to magnesia. 
 
 " Of these substances, and also of their compounds with 
 one another, lime appearing to possess a decided superiority, 
 my subsequent experiments were confined to it alone, and 
 by a more perfect adjustment of the apparatus, by bringing 
 the maximum heat, which is confined within narrow 
 limits, exactly to the surface of the lime ball, and by using 
 smaller balls than those employed in the early experiments, 
 a very material increase of light has been obtained. The 
 mean of ten experiments, made lately with every pre- 
 caution, gives for the light emitted by lime, when exposed 
 to this intense heat, 83 times the intensity of the brightest 
 part of the flame of an Argand burner of the best construc- 
 tion, and supplied with the finest oil. The lime from chalk, 
 and such as is known at the London wharfs by the name of 
 flame lime, appears to be more brilliant than any that has 
 been tried. When well-burned Carrara marble is made 
 into a paste with water, and gradually dried, it appears to 
 be nearly equal to the preceding ; when strongly com- 
 pressed, or very porous, it is inferior." 
 
 The best limes to be obtained are of the kind known as 
 " hard," or " Nottingham limes/' These last better than 
 any others that I know of. They are sold in tin boxes 
 holding one dozen each, and are packed in powdered lime, 
 kept as far as possible from the air. Let it be remembered 
 that these limes will be spoiled by exposure to damp air. 
 By such exposure they swell to double their normal size, 
 will break the strongest box in which they are confined, 
 and will, finally, fall to powder. In other words, they are 
 
74 
 
 THE BOOK OP THE LANTERN. 
 
 made of quick lime, and moisture will slake them. Lime 
 cylinders are difficult things to keep, for damp air will get 
 to them in spite of ordinary precautions. I have tried to 
 preserve them — with partial success — by dipping each 
 cylinder separately into a solution of indiarubber in ben- 
 zole or chloroform, which forms a skin upon its surface. 
 An American writer publishes a better plan. He melts 
 some solid paraffin or bees' wax in a. metallic vessel, 
 exercising care that the heat is just enough to render 
 the substance liquid and no more. He then dips each 
 cylinder into the wax half way, allows it to cool, and then 
 holding it by its waxed end, dips the other half. This 
 coating, he says, quite excludes the air, and the limes may 
 be rolled in paper and packed away until wanted for use. 
 The coating is readily peeled off when the lime is required 
 for the lantern, provided that the heat employed in melting 
 the wax was not too high when the cylinders were dipped. 
 Each lime is cylindrical, and about one inch and a half in 
 length, with a central hole for the reception of the pin 
 upon the jet. This hole should be carefully freed of 
 powdered lime, by running a match through it, after 
 which the cylinder can be placed upon its pin, where for 
 the present we will leave it. 
 
 As already indicated, the most commonly used form of lime 
 jet is the safety, or blow-through kind. If the jet be a 
 properly-constructed one, it will well illuminate a picture 
 15 feet in diameter. In this jet the hydrogen is sup- 
 plied from the nearest household source, by a connecting 
 tube of india-rubber. Herein lies, perhaps, its only dis- 
 advantage. In an ordinary house the connexion is an 
 
THE BOOK OF THE LANTERN. 
 
 75 
 
 easy matter, but in large halls, which are now commonly 
 lighted by one or two sunlights high overhead, the 
 operator finds himself in a serious difficulty. In this jet 
 the two gases do not mix until they reach the point of 
 combustion, and for this reason the apparatus is dis- 
 tinguished by the word " safety." For hydrogen and 
 oxyen, when mixed together, form an explosive vapour of 
 most terrible power, and one which is most difficult to 
 control. If any one should wish to prove this, let him fill 
 a soda-water bottle with the gases over a pneumatic trough 
 in the proportions of two volumes of hydrogen to one of 
 oxygen. Then close the bottle with a well-greased cork, 
 and, after wrapping it in a towel in case of fracture, take 
 out the cork, and put the mouth of the bottle in front of a 
 candle flame. The report caused by the explosion of the 
 gases will be quite equal to a heavily-charged fowling- 
 piece. But when the two gases are used in conjunction 
 with the safety-jet there is no risk of explosion, for no 
 mixture takes place until the gases meet on the lime 
 cylinder. I know that accidents have happened when 
 this jet has been in use, but they are traceable to im- 
 proper use of the apparatus. A case of this kind came 
 under my notice quite lately. An optician had employed 
 a new hand to see after the making of the oxygen gas and 
 filling the bag with the same. This individual was, after 
 a time, left to his own devices, and finding, upon one 
 occasion, that the bag was not full, he attached it to the 
 nearest gas-bracket until it was properly distended. This 
 bag was used in public the same evening, and a few 
 minutes after the proceedings commenced it blew up, and, 
 
76 
 
 THE BOOK OF THE LANTERN. 
 
 besides wrecking the lantern, smashed all the windows in 
 the hall. The cause of the disaster leaked ont afterwards. 
 
 But with proper care this jet is perfectly safe, and 
 one which I have used scores of times for purposes of 
 demonstration in crowded school-rooms. As the bulk of 
 my readers are more likely to adopt this form of limelight 
 than any other, I will give directions for working with it 
 which will at once show its simplicity. We will suppose, 
 in order to make the matter clearer, that the operator has 
 a single lantern fitted with this form of jet. 
 
 Beyond the mere lantern and its belongings, there will 
 be required some india-rubber tubing, a box of limes, and 
 a bag or bottle of gas. The best rubber tubing is the red 
 variety; but it is expensive. It will, therefore, be found 
 economical to adopt a plan which I myself have practised 
 with advantage. Two lengths of tubing are required, one 
 for each of the gases employed. A 6-foot length will be 
 sufficient to connect the 0 side of the jet with the iron 
 bottle or bag ; but the length of the other piece of tubing, 
 which is to connect the H side of the jet with the nearest 
 house gas-burner, is obviously dependent upon the distance 
 of that supply from the place where the lantern is being 
 exhibited. If the nearest tap is in another room, it is best 
 to use a length of compo. (lead) gas-pipe, which is absurdly 
 cheap. Upon one occasion I remember drawing the gas 
 from another house by such a means of communication, 
 the pipe passing through two windows. But it is only 
 upon rare occasions that such a proceeding is necessary, 
 and the worker is generally able to find a source of gas- 
 supply ready to his hand. When such is the case, I 
 
THE BOOK OF THE LANTERN. 
 
 77 
 
 recommend the employment of two different kinds oi 
 tnbing. There is a hard black kind, made, I fancy, in 
 France, but easily procurable in this country, which wears 
 extremely well, far better, indeed, than the ordinary grey 
 kind. It is cheap as well as good. The only part where 
 it seems to deteriorate is the end, where it is being 
 constantly fitted on to the metal jet. This gets soft and 
 rough after some time, a failing which is easily remedied 
 by judicious amputation. Use for each gas a sufficient 
 length of this black tubing, and firmly attach to the end 
 of each piece a short length of the more elastic red tubing, 
 by which connexion with the bottle and house gas respec- 
 tively can be easily made. In joining the two kinds of 
 tubing together, use a couple of inches of lead pipe as a 
 connecting link between them. First draw the black 
 tubing half way over the lead, and then, if possible, allow 
 the red tube to cover both, securing the whole with 
 string. 
 
 Having all these things ready, the H tube fastened to 
 the nearest gas supply, and the O tube to the bottle or bag, 
 we can proceed to work. Let the lime-pin be so adjusted 
 that the lime is about 1-1 6th of an inch from the nozzle of 
 the jet. Then turn on the tap marked H, and light the 
 jet. Turn down the gas until the flame is about one 
 inch high, and let matters thus remain for five minutes, to 
 give the lime time to warm through Without this pre- 
 caution, and if the oxygen is turned on at once, the lime 
 is apt to split up from the sudden heat. 
 
 After this five minutes' rest, you may attend to the 
 oxygen supply. If the gas is supplied from a bottle or 
 
78 
 
 THE BOOK OF THE LANTERN. 
 
 cylinder first turn the O tap of the jet full on, and let it 
 remain so. This is a most important point, and for the 
 following reason : the supply of oxygen must be regulated 
 only from the tap on the bottle, for the pressure of gas is 
 so great that if we turn on the bottle tap and then attempt 
 to check its now by moving the tap jet, the connecting 
 rubber tube will be blown off or possibly split up. There 
 is another advantage in keeping the hydrogen jet burning 
 for some time before the lantern is used. It warms the 
 glasses, and prevents that deposit of moisture upon them 
 which is otherwise always more or less apparent, especially 
 in a crowded room. Turn the H tap until there is a good 
 big flame from the jet, and now very, rery gradually turn 
 the lever tap of the bottle. If you do this too quickly, the 
 sudden mixture of O and H at the jet causes the light 
 to go out with an unpleasant crack. There is really no 
 danger, but the noise frightens nervous people, who are 
 prone to associate with lanterns generally the idea of being 
 blown skyward. The regulation of the two gases is a 
 matter which is soon learned by experience, and is 'governed 
 by the appearance of the disc of light obtained on the sheet. 
 Move the two taps until the best effect is obtained ; the 
 knack of doing so is very soon learned. 
 
 Having seen that the gas jet is burning well and quietly, 
 which is one sign that all is at it should be, the next thing 
 is to see that the light is perfectly central with the optical 
 system. See that the tray upon which the jet is fixed is 
 withdrawn so as to leave a space of about 4 inches 
 between the light and the condensing lens. Raise or lower 
 the jet on its supporting rod, and move it from left to 
 right until the flare of light seen upon the sheet is as 
 
THE BOOK OF THE LANTERN. 
 
 79 
 
 central as possible. When this is the case, tighten the screw 
 or screws (and two are better than one) which hold the jet 
 on the rod, so as to clamp it firmly in position. Now press 
 forward the tray, so that the light approaches the condenser, 
 and this will canse the sheet to become equally illuminated 
 with a sharply- defined margin all round. Now place a 
 slide on the stage of the lantern, and focus it as sharply as 
 possible. The best way to do this is to set the focussing- 
 screw so that it is at its middle position, then focus by 
 sliding in and out the flange into which the objective is 
 screwed. Get roughly the best focus which you can obtain 
 by this means, and then give a finishing touch by means of 
 the focussing-screw. 
 
 If a double or biunial lantern be employed, the necessary 
 operations will be rather more complicated, for here we shall 
 have two lights, and two optical systems to control instead 
 of one. But, when once understood, the working of a double 
 lantern is both simple and easy, so much so that on many 
 occasions when a good assistant was not forthcoming I have 
 worked the lantern myself and lectured at the same time. 
 The two lanterns are connected by means of a dissolving tap, 
 such as that shown in fig. 3, which is a very good pattern. 
 This tap is so arranged that when the lever is upright both 
 lanterns have their full supply, of the gases ; when the 
 lever is turned over towards the left-hand side, the lower 
 lantern only is provided for, whilst when in the reverse 
 direction the upper one is supplied with gas. The original 
 plan for dissolving was to move a couple of serrated 
 screens to and fro in front of the lenses, both jets 
 continuing burning during the entire exhibition. The 
 more modern method of cutting off the gas supply from 
 
80 THE BOOK OF THE LANTERN. 
 
 each lantern alternately has the great merit of saving 
 nearly half the gas bill. It will be noticed in the cut of 
 the dissolving tap that it is furnished with two small stop- 
 
 cocks, which are fixed on vertical tubes near its centre. 
 These tubes are by-passes which allow a small quantity 
 of gas to pass to each burner, although the lever has 
 shut off the main supply. The necessity for this arrange- 
 ment is obvious ; without it the lantern not in actual use 
 would be totally extinguished. In using the blow -through 
 form of jet both by-passes must be employed, but with 
 the mixed jet the hydrogen by-pass only is necessary. 
 The first thing to be done in operating with a double 
 lantern is to light the hydrogen in both lanterns, and to so 
 adjust the by-pass that it will admit just enough gas to 
 the lantern not in use to give a flame about half an inch 
 high. When the blow -through jet is used the correspond- 
 ing oxygen tap must be manipulated to furnish just enough 
 of that gas to tinge the hydrogen flame. If this precaution 
 
THE BOOK OF THE LANTERN. 
 
 81 
 
 be not taken, the sudden influx of oxygen to the burner, 
 when the dissolving lever is turned, will almost infallibly 
 3ause the flame to snap out with a sharp crack. 
 
 The mixed jet is as easily worked as the safety form and 
 — despite the confidence-inspiring name of the latter — is, 
 in my opinion, quite as safe in careful hands. In some 
 forms of mixed jets pumice-stone chambers, receptacles 
 charged with discs of wire-gauze, and other arrangements 
 "which are supposed to prevent the flame passing back 
 through the tubes, form part of the design. I look upon 
 such contrivances as mere obstacles to the free passage of 
 the gas; and, although some of my jets were originally 
 provided with them, I did away with them as quickly as 
 possible. 
 
 The dissolver for a triple lantern is naturally more com- 
 plicated ; but taps ha TT e been devised which are so arranged 
 
 Fig. 33. 
 
 that any one of the three lanterns can be put in or out of 
 action at will. Such a tap is shown at fig. 33. Another 
 
 G 
 
82 
 
 THE BOOK OF THE LANTERN. 
 
 pattern of very compact form is illustrated at fig. 34. In 
 this case the by-passes are governed by taps which are 
 adjusted by the operator with a screw-driver. This seems 
 to be a good arrangement, as there is no chance of 
 accidental turning off or on by a careless touch, as may 
 happen when the by-pass taps are exposed. 
 
 Fig. 34. 
 
 There are one or two methods of manufacturing oxygen 
 gas for the limelight as fast as it is used, and although, 
 for reasons which I shall presently give, I cannot recom- 
 mend such a procedure, the methods are ingenious enough 
 to warrant notice. In Chadwick's apparatus there is an 
 iron gas-holder, which forms the support of the lantern. 
 Associated with it is a special form of retort heated by a 
 Bunsen burner, and charged with chlorate of potash and 
 manganese made up into a cake previously. The operator 
 starts with a full gas-holder, and at the end of perhaps 
 fifteen minutes, when it is nearly empty, lights the Bun- 
 sen burner, and in a few minutes enough gas is generated 
 to fill it once more. The retort is now charged with a 
 fresh cake of mixture ready for once more filling the gas- 
 holder as it sinks. 
 
THE BOOK OF THE LANTERN. 
 
 83 
 
 Another plan was originated some time ago by Mr. 
 Beseler, of New York, and published by him in one of the 
 American journals. In this case the mixed chemicals are 
 placed in a metal tube, with a Bunsen burner beneath it. 
 As the gas is generated it fills a small gasholder, which 
 supplies the lantern. Only one part of the tube at a time 
 is subjected to he it, so that when a fresh supply of oxygen 
 is wanted, all that is necessary is to shift the Bunsen 
 burner to another part of the tube, and the gasholder is 
 replenished. This latter plan is more simple than Chad- 
 wick's ; but I object to both, unless it be for experimental 
 work at home, on two broad grounds. One is, that the 
 blow-through jet can only be used in conjunction with 
 such an apparatus, and the other is, that a lantern operator 
 has quite enough to do in attending to his burners and 
 changing the. pictures without being burdened with the 
 constant anxiety of seeing to the gas supply. 
 
 Of late years much has been heard about the so-called 
 ether-oxygen or ethoxo limelight, so called because the 
 vapour of sulphuric ether is used in lieu of the ordinary 
 hydrogen, or coal-gas. I have tried this light, and, while 
 admiring its brilliance, which is quite equal to any form 
 of limelight which I have seen, I am very doubtful as to 
 its safety. I have no doubt that it can be so arranged as 
 to work with safety ; but several explosions which have 
 occurred with it show very conclusively and unpleasantly 
 that that time has not yet arrived. With the tempting 
 advantages of extreme portability and brilliant light 
 which this or any other system may offer, I hold that it is 
 a positive duty to eschew it until it is known by further 
 
 g2 
 
84 
 
 THE BOOK OF THE LANTERN. 
 
 experience to be absolutely innocuous. Some may say, 
 " Oh, there is no real danger ; the worst that can happen 
 is one of the tubes blowing off with a bang ! " But this 
 apparently harmless " bang " may cause a panic in a 
 public hall, which may lead, possibly, to fatal results. So, 
 for the present, at any rate, I shall do without the ether 
 light, while, at the same time I shall look forward to its 
 gradual perfection with the greatest interest. It is only 
 fair to state that this light is much used in America, 
 its greatest champion being Mr. Ives, who recently con- 
 tributed a paper on the subject to the Franklin Institute. 
 Mr. Ives is such a good worker that his words carry weight 
 with them. I quote the following remarks from his 
 paper : — 
 
 " Notwithstanding the great success of this means for 
 producing the limelight, and the important advantages 
 which it offers, I have always recognised in it certain 
 minor faults, which I hoped to overcome in course of time, 
 an<I my object in preparing this paper has been to call 
 attention to some recent improvements I have made, which 
 I believe will greatly extend the use of the light, and 
 increase its popularity. The first improvement is in the 
 construction of the saturator, which is reduced in size, yet 
 increased in effectiveness. The second is in the use of 
 petroleum ether (rhigolene), which gives the same light as 
 sulphuric ether, but vaporises at a lower temperature, costs 
 much less, and contains neither alcohol nor water to accu- 
 mulate in the saturator. 
 
 "My improved saturator is in the form of a single 
 metallic tube, 2 inches in diameter and 13 inches long, 
 
TIIU BOOK OF THE LANTERN. 
 
 85 
 
 with a handle at the middle and a stop-cock projecting up- 
 ward at each end. A neck, like that of a bottle, projects 
 from the screw cap at the end, and is closed with a cork 
 for convenience in filling. The passage for oxygen is over 
 20 inches long, in the form of a zig-zag channel through 
 the upper surface of the roll of porous material, and 
 secures complete saturation of the gas with vapour. The 
 saturator can be filled from a bottle in one minute, and is 
 ready for use at once, or may be kept filled for any length 
 of time. Petroleum ether costs only thirty cents a pound, 
 which is less than half the price of sulphuric ether ; it also 
 vaporises at a lower temperature, so that the light can be 
 used successfully even in a very cold room, and it has 
 other advantages. It will supply a pair of lanterns con- 
 nected by dissolving key, for two hours continuously. It 
 should be stored in a cool place and kept tightly corked. 
 It is also necessary, when using it with oxygen from a 
 cylinder, to use a valve that can be opened very slowly, 
 because a very small amount of oxygen passing the satu- 
 rator will produce a very large flame at the jet. The 
 Shaw valve, manufactured by Mr. Shaw, a member of this 
 Institute, fulfils the requirements, and is already largely 
 used in this city. Some special instruction for the manage- 
 ment of the light in hot weather may also be called for. 
 
 "In conclusion, I give it as my opinion that this im- 
 proved means for supplying the hydrogen element is so 
 much simpler and more convenient than any other, that it 
 cannot fail to entirely supersede the use of hydrogen and 
 coal-gas, when its merits shall hare become generally 
 known and appreciated." 
 
CHAPTER VI. 
 
 SCREENS. 
 
 NDER this head comes the sheet, hung in 
 the required position by supporting cords, and 
 screens fixed on built-up frames. 
 First, as to the simple sheet. A badly -hung sheet is 
 an abomination. It should be so hung that there is a cer- 
 tain pull upon it from the centre to the edges all round, 
 and this may be brought about by following the directions 
 now given. The sheet may be made of either linen 
 or cotton. I prefer the latter, because it is cheaper, and 
 more opaque, and we shall presently see that opacity car- 
 ries with it certain advantages. If the sheet is of such a 
 size that it must be joined (that is to say, if it be more 
 than about 10 feet square), the necessary seams should lie 
 horizontally, not vertically. A sheet in which the seams 
 are vertical, is liable to hang in festoon-like folds ; but if the 
 seams be horizontal, it will hang straight, so long as its top 
 edge is properly secured. The sheet should have along 
 this edge a broad hem, in which is run a strong cord. 
 This cord should be firmly fastened to the corners of the 
 
THE BOOK OF THE LANTERN. 
 
 87 
 
 sheet, and in such a way that when it is stretched, the 
 material of which the sheet is made will not pucker. At each 
 end of this cord there should be a loop made by doubling 
 it over, and wrapping it round with waxed thread. 
 Along each side of the sheet should be placed, at intervals 
 of about eighteen inches, galvanized iron rings, or brass 
 curtain rings will answer the purpose. The bottom of the 
 sheet may be left free. 
 
 A screen of this description will require no fittings to 
 hang it in position, beyond a couple of screw-eyes placed 
 so far apart that the sheet will easily go between them ; 
 and which should be inserted in the cornice or roof of the 
 exhibition-room, with two more eyes placed immediately 
 underneath the top ones, and screwed into the floor. Next 
 are required two strong but thin cords ; and it is best at 
 the outset to procure these of the best quality possible, for 
 upon their strength the sheet entirely depends. Each cord 
 should be fitted at one end with a swivel and clip like that 
 upon a dog's chain. 
 
 Having made these preparations the hanging of even a 
 large sheet will be comparatively easy. First, let the cords 
 be run through the fixed screw-eyes in the roof or upper 
 part of the wall ; one cord through each eye, and so inserted 
 that the clips on the cords are inside, — i.e., facing each 
 other. Next clip the sheet to the cords by the loops pro- 
 vided at the top corners, as already described. The sheet 
 can now be pulled up bodily, — preferably by two persons, 
 one at each cord. Next place the free ends of the cords 
 through the screw-eyes in the floor, and stretching the sheet 
 as tightly as possible, secure each by a simple knot. 
 
88 
 
 THE BOOK OF THE IANTERN. 
 
 We shall now see the advantage of the eyelet-holes or 
 rings at the sides of the sheet. Fastening a piece of 
 string to the top eyelet-hole at one side, — and this is better 
 done before the sheet is pnlled into position, — allow that 
 string to embrace the supporting cord, next let it pass 
 through the nearest eyelet-hole, then again round the cord, 
 and so on until the bottom of the sheet is reached. By this 
 lacing method the sheet can be rendered almost as flat as a 
 board, and presents the best possible kind of surface so far 
 as a sheet can give it for showing lantern pictures well. 
 
 Some little judgment must be exercised as to the best 
 position for the upper screw-eyes. Of course, in practice, 
 difficulties are apt to occur. The best position may be one 
 which the ladder available will not reach. Again, it is 
 often the case that screw-eyes may be found already 
 in position, and the owners of public halls have a righteous 
 
 Fig. 35. A B 
 
 objection to holes being made, even to the tiny ones 
 necessary for fresh screw-eyes. In such a case the 
 
TUE BOOK OF THE LANTERN. 
 
 89 
 
 exhibitor must content himself with existing arrangements. 
 Bnt supposing that he has a free will in the » matter, he 
 must exercise his judgment with regard to the size of the 
 hall, and the best position for hanging a sheet. For in- 
 stance, in a hall with a pointed roof, the position A (see 
 figure 35) would be preferable to position B. In some 
 halls, again, the walls may be so far apart that the sheet 
 will, when hung in the manner described, drop consider- 
 ably by its own weight, so that, although the screw-eyes 
 may be 20 feet from the ground, the top edge of the sheet 
 will be only 14 or 15 feet above the floor. The best 
 way of obviating this is by the use of two wooden struts, 
 or supports, placed as shown in figure 36. In this dia- 
 
 Fig. 36. 
 
 gram the dotted lines indicate the position which the sheet 
 would occupy without this help. 
 
 The material of which the screen or sheet is made is of 
 far more importance than would be thought by an inexperi- 
 enced worker. A careful artist knows that a good picture 
 cannot be produced on crumpled or dirty paper ; and the 
 lantern exhibitor should be quite as careful to provide for 
 his pictures an unblemished and even surface. Un- 
 
90 
 
 THE BOOK OF THE LANTERN. 
 
 doubtedly the best thing of all is a simple white -washed 
 wall. Why should this be so ? Let me endeavour to 
 explain the matter in a few words. 
 
 Suppose that we go behind an ordinary linen or cotton 
 sheet, while lantern pictures are being thrown in front and 
 upon it. We not only see the picture distinctly through 
 the sheet, but there is enough light round about us to enable 
 small print to be read with ease. At least such is the case 
 with the lime-light, and in a minor degree with the oil 
 lantern. Now all this light means so much deducted from 
 the light available from the lantern, and which, therefore, 
 is completely lost to the spectators in front. From an 
 opaque wall, on the other hand, the light is nearly all reflected 
 to the spectators' eyes ; and although no doubt some must 
 be absorbed, we know that none is actually transmitted 
 through the screen, and utterly wasted, as in the case of a 
 semi-opaque sheet. We might compare the two cases, to a 
 vessel of water with a porous bottom, which will, of course, 
 allow a large portion of the liquid to dribble through and 
 be lost ; as against a vessel with a solid bottom which will 
 hold water without any wasteful transmission. But a 
 white-washed wall is not often met with in a lecture -hall, 
 and the best substitute is a canvas sheet rendered opaque 
 with white-wash. Such a sheet is portable up to a certain 
 size ; and if intended for use as a fixture in any one hall, 
 can be made up to any size, within reasonable limits. 
 Witness the scenes on rollers at our large theatres and opera 
 houses, the basis of which is simply whitened canvas. Such 
 a plan was adopted at the late Polytechnic Institution, where 
 the screen measured no less than 26 feet across. 
 
THE BOOK OF THE LANTERN. 
 
 91 
 
 There is a further advantage connected with using a 
 sheet of this description, which is that when, not in actual 
 use it can be rolled up, and will keep perfectly clean for 
 many years. When soiled, a fresh coat of white-wash can 
 be given to it with little trouble and expense. For home 
 use a screen of this nature is to be greatly recommended. 
 Let me now describe the method by which such a surface 
 can be prepared, and the best way of hanging it in position. 
 The following detailed directions are quoted from an article 
 upon the subject which I wrote some time back : — 
 
 Having decided upon the dimensions of the screen, 
 which, of course, must be governed by the size of the 
 room in which it is to be hung, we must first of all have a 
 frame made upon which the material can be stretched 
 whilst being painted. Any kind of close- textured material 
 will answer our purpose, good unbleached calico being as 
 suitable as anything else. The frame should be strong, 
 for as soon as the sheet is wetted it shrinks, and is apt to 
 pull an ill-constructed frame all askew. The calico, — if 
 joined, should be neatly sewn, — and so tacked on the frame 
 that the seam or seams will lie horizontally. The sheet 
 must be nailed on the frame with tacks, and this appa- 
 rently simple work must be done in a certain way, or 
 it will be pulled into creases. The four corners must 
 be first secured, and afterwards the sides may be nailed 
 down, one side being completely nailed before another is 
 begun. By this means the sheet will, when done, present 
 one even surface. This done, it must receive a coat- 
 ing of size. The best double size should be used, and 
 should be melted in a suitable vessel with its own weight 
 
92 
 
 THE BOOK OP THI LANTEEK. 
 
 of water. The size while on the fire should be watched 
 and occasionally stirred, but should not be allowed to boil. 
 When melted, this size is well brushed into the calico, and 
 allowed to dry. It will then be ready to receive its 
 coating of white paint. This consists of whiting which 
 has been soaked in water until it assumes the appearance 
 of thick white mud. To this strong melted size must be 
 added until the mixture is of the consistence of cream. 
 It can be left now for some hours until it has become 
 perfectly cold. At the end of that time it should have 
 the appearance of very weak jelly, — a jelly which can be 
 easily broken up by the paint-brush. 
 
 The frame being placed upright and properly secured, 
 the workman commences at the top, working the well- 
 charged brush up and down, and then horizontally, so as 
 to avoid leaving any lines upon the surface, until it is all 
 covered. If the sheet be unusually rough in texture, it 
 will benefit by another coat when the first is dry. 
 
 When this painting operation is finished the nails must 
 be drawn from the frame, and the sheet must be tacked 
 on to a roller. This roller may be hung like a window- 
 blind at the top of the room, and governed by a cord in 
 the familiar manner. But if it is of large size, — say 12 
 feet across or more, — the roller is best placed at the bottom 
 of the sheet, and made to roll up by cords upon its pro- 
 jecting ends, and pulleys above like the drop scene at a 
 theatre. 
 
 It has often struck me as a deplorable oversight that 
 halls where lantern lectures are of constant occurrence, 
 are not fitted with permanent roll-up screens of this kind. 
 
THE BOOK OF THE LANTERN. 
 
 93 
 
 I know most of the lecture halls in the kingdom, but I am 
 not aware of a single one where this arrangement exists. 
 The lecturer who visits these places is responsible for 
 bringing his own screen, and his assistant must fit it up, 
 an operation which is sometimes, — owing to the structure 
 of the hall, — very troublesome and difficult. A permanent 
 rolled-up screen would obviate all this difficult} 7- , and would 
 add greatly, for the reasons already given, to the success of 
 the exhibition. I can only suppose that this is one of those 
 . matters which comes under the head of everybody's 
 business, and therefore nobody attends to it, or seeks to 
 remedy what I feel is a mistake. 
 
 We will next consider the method of hanging a sheet on 
 a portable frame. Some lecturers adopt this plan, and if 
 they are not afraid of adding to their luggage a huge 
 bundle of sticks, they certainly have the advantage of 
 being independent of ladders, staples, and all the things 
 necessary for hanging a sheet in the ordinary way. There 
 are several descriptions of frames made for this purpose, 
 which are sold by dealers ; some are good, and some 
 are very much the reverse, giving much more trouble 
 than they are worth. Perhaps the best form of frame is 
 that which is made of round pine sticks, about 4 or 5 feet 
 long, like broom-sticks, and which fit to one another, — - 
 fishing-rod fashion, — by means of brass sockets. The 
 corners of the frame are represented by sockets mitred, and 
 brazed together, see fig. 37. Such a frame as this is easily 
 put up. First of all the top pieces are socketed together, 
 and furnished with their corner pieces and one length of 
 the wooden rods. The side pieces a*e next placed in their 
 
94 
 
 THE BOOK OF THE LANTERN. 
 
 proper sockets, and the top portion of the sheet is tied on by 
 tapes. It is reared up a little higher by the addition of two 
 more side pieces ; and as this building-up gradually goes on 
 the sides of the sheet are secured by tapes to the frame. The 
 
 Fig, 37. 
 
 bottom pieces are finally attached and the frame is com- 
 plete. If there is room enough this operation of mounting 
 the sheet on its frame is best performed when both are 
 lying flat on the floor, otherwise it must be done by 
 gradually building up the frame while it is in a vertical 
 position. At each top corner should be fastened guy 
 ropes, and these can be secured to staples screwed into 
 the floor. 
 
 One advantage of a frame of the above description is 
 that, when, from the nature of the hall, it must be erected 
 on a platform at a higher level than that of the lantern, 
 the whole screen can be made to incline forwards, so as 
 to bring its surface square with the lens. With a strictly 
 vertical sheet the picture would, under such circumstances, 
 be thrown out of shape and out of focus. 
 
 Whatever wood may be chosen for the material of the 
 
THE BOOK OF THE LANTERN. 
 
 95 
 
 frame, it should be strong ; for if the sheet is tightly 
 stretched, as it ought to be, there will be a very heavy 
 strain upon its support. Perhaps the best wood for the 
 purpose is bamboo, which combines the qualities of 
 extreme lightness with great strength. I believe that 
 bamboo frames can now be obtained commercially. 
 
 The rule for finding the correct distance between lantern 
 and sheet is to add one to the number of times enlargement 
 required, and multiply by the equivalent focus of the lens 
 used. If, for instance, a slide measures 3 inches, and it is 
 desired to cover a screen 1 0 feet across, the scale of 
 enlargement is 40 times : and 41 times the equivalent 
 focus of the lens gives the required distance between lens 
 and screen. 
 
 In order to find the equivalent focus of a lens, it is con- 
 venient, in the absence of special apparatus, to proceed as 
 follows : — Focus upon a white surface an image of the 
 Sun or other distant object, taking care to place the lens 
 axis as nearly as possible in line with the object, and 
 perpendicular to the surface receiving the image. When 
 the image is sharply focussed, measure carefully the dis- 
 tance between it and the nearest surface of the lens. 
 Repeat this operation with the lens reversed, and measure 
 the distance to the same surface as before ; in this caae, 
 the surface furthest away. The average of the two 
 measurements thus obtained is approximately the 
 equivalent focus of the lens. 
 
 I am indebted to Mr, Taylor, of Leicester, for the fol- 
 lowing useful table : — 
 
96 
 
 THE BOOK OF THE LANTERN. 
 
 Table of Distances between Lens and Screen for 
 various Scales of Enlargement, and with Lenses of 
 various equivalent focal length, 
 
 1 § 
 
 o & 
 . « 
 
 £ g 
 
 4 
 
 5 
 
 6" 
 
 ? 
 
 8" 
 
 : 
 
 9 
 
 10" 
 
 11" 
 
 12' 
 
 Focus of 
 lens. 
 
 12 
 
 4'4" 
 
 B'5" 
 
 6'6" 
 
 
 
 7'7" 
 
 8'8" 
 
 9'9" 
 
 1016" 
 
 1111" 
 
 13' 
 
 
 18 
 
 6'4" 
 
 7' IF 
 
 9'6" 
 
 11' 1" 
 
 12'8" 
 
 14'3" 
 
 1510" 
 
 17'5" 
 
 19' 
 
 w 
 
 24 
 
 8'4" 
 
 10'5" 
 
 12'6" 
 
 147" 
 
 16'8" 
 
 18'9" 
 
 2010" 
 
 2211" 
 
 25' 
 
 « 
 
 30 
 
 10'4" 
 
 12'1 1" 
 
 15'3" 
 
 181" 
 
 2 '8" 
 
 23'3" 
 
 2510" 
 
 28'5" 
 
 31 
 
 o 
 
 CO 
 
 36 
 
 12'4" 
 
 15' 5" 
 
 18'6" 
 
 217" 
 
 24'8" 
 
 27 '9" 
 
 3010" 
 
 3311" 
 
 37' 
 
 p 
 
 42 
 
 J4'4 // 
 
 l7'4" 
 
 21'6" 
 
 25' 1" 
 
 2S'8" 
 
 32'3" 
 
 3610" 
 
 39 / 6' / 
 
 43' 
 
 
 48 
 
 16'4" 
 
 2oV 
 
 2/6" 
 
 287" 
 
 32'8" 
 
 36'9" 
 
 4' 10" 
 
 4411" 
 
 49' 
 
 
 54 
 
 18'4" 
 
 22' 11" 
 
 27'6" 
 
 32a" 
 
 36'8" 
 
 41'3" 
 
 4510" 
 
 50V 
 
 55' 
 
 
 60 
 
 2 '4'- 
 
 25'5" 
 
 30V 
 
 357" 
 
 40'8" 
 
 45'9" 
 
 5010" 
 
 6511" 
 
 61' 
 
 w 
 
 Hi 
 
 66 
 
 22'4" 
 
 27' 11" 
 
 33'6" 
 
 391" 
 
 44'8" 
 
 50'3" 
 
 5510" 
 
 61V 
 
 67' 
 
 
 72 
 
 24'4" 
 
 30'o" 
 
 36 '6" 
 
 427" 
 
 48'8" 
 
 54'9" 
 
 601 " 
 
 6611" 
 
 73' 
 
 m 
 
 78 
 
 26'1" 
 
 H211" 
 
 39'6" 
 
 46'1" 
 
 52'8" 
 
 5h'3" 
 
 65l<" 
 
 72'5" 
 
 79' 
 
 
 84 
 
 28'4" 
 
 3/5" 
 
 42'6" 
 
 497" 
 
 56V 
 
 63'9" 
 
 7 10" 
 
 7711" 
 
 85' 
 
 
 90 
 
 3<>'4>" 
 
 37/1 >" 
 
 45'6" 
 
 631" 
 
 6"'8" 
 
 68'3" 
 
 75'lfi" 
 
 83V 
 
 91 
 
 ffl 
 
 96 
 
 32'4"' 
 
 40'5" 
 
 48'«" 
 
 567" 
 
 64V 
 
 72'9" 
 
 8«/l' " 
 
 8811" 
 
 97' 
 
 
 102 
 
 34'4 7 
 
 42' 11" 
 
 51'6" 
 
 eo'i" 
 
 68'8" 
 
 77'3" 
 
 8510" 
 
 94'o" 
 
 1 3' 
 
 o 
 
 108 
 
 36'4" 
 
 45'5" 
 
 64'6" 
 
 637" 
 
 72*8" 
 
 81V 
 
 9010" 
 
 9911" 
 
 1' 9' 
 
 
 114 
 
 38'4" 
 
 4711" 
 
 57'6" 
 
 671" 
 
 76'8" 
 
 86'3" 
 
 9510" 
 
 105 5" 
 
 115' 
 
 
 120 
 
 40'4" 
 
 5u5" 
 
 60'6" 
 
 707" 
 
 80'8" 
 
 90'9" 
 
 10010" 
 
 11 11" 
 
 121' 
 
 p 
 
CHAPTER VII. 
 
 THE PREPARATION OP LANTERN SLIDES, DIAGRAMS, ETC., 
 WITHOUT THE AID OF PHOTOGRAPHY. 
 
 EFOKE it became possible to use photography in 
 conjunction with the lantern, what are called 
 hand-painted slides had to be depended upon, 
 for they were the sole pictures that could be obtained. 
 In those days it was common to use a very much 
 larger picture for the lantern than at present. Those 
 pictures which delighted one or two generations of sight- 
 seers at the old Polytechnic, measured about eight inches 
 by five. Some of these pictures were most elaborate works 
 of art ; so much so, that at the sale of the belongings of 
 the Polytechnic in 1881, when the Institution as a place of 
 entertainment was broken up, many of these slides real- 
 ised as much as fifty shillings each. It is to be feared that 
 such hand-painting on glass is now almost . a lost art, for 
 people will not pay the price which would remunerate a 
 competent artist, when they can obtain a more perfect 
 representation, — as to form at least, — by means of a photo- 
 graph. The slide-painter of those days used to work both 
 
98 
 
 THE BOOK OF THE LANTERN. 
 
 in water colour and in oil colour, sometimes, I believe, 
 combining the two methods in one picture; and his first 
 proceeding was to draw the outline on the glass, in black 
 pigment, with a very fine brush. Those who do not wish 
 to dabble in photography, and who have some artistic taste 
 may still adopt the same plan, and they will find that with 
 a little practice they will be able to draw with a fine brush 
 and with a suitable pigment, as finely as they can on paper 
 with a pen. The Japanese artists, — I may mention, — do all 
 their worF, and even their writing, with a brush, and we 
 all know their pictures are not to be despised. It will 
 be found that such an outline is easier to produce if the 
 glass be first covered with a layer of varnish. Some use 
 a weak solution of gelatine in water, to give the glass the 
 necessary surface for taking the pigment. A solution of 
 sugar has also been recommended for the same purpose, 
 A still easier plan of producing diagrams of line drawings 
 without the aid of photography is to use sheet gelatine, 
 which is sold for the purpose. This gelatine is placed over 
 the engraving or other design which it is wished to copy ; 
 and the lines are traced with a sharp point, such as an 
 etching-needle. Fine black lead is then rubbed over the 
 surface with the top of the finger, with the result that the 
 black powder lodges in the scratches, but does not adhere 
 to the smooth surface. This plan I look upon merely as a 
 makeshift; but I mention it for what it is worth. 
 
 A method by which far better results can be obtained 
 was published some years ago by the Rev. Dr. Dallinger, 
 the eminent microscopist, who has for a long time used 
 slides produced in the way he describes. His plan is 
 
THE BOOK OF TITE LANTERN. 
 
 99 
 
 briefly this. He works with a hard pencil on a piece of 
 very finely-ground glass ; afterwards filling in the outlines 
 thus made with water colours, and applying a coat of var- 
 nish so as to give the necessary transparency to the picture. 
 This method he brought before the Royal Microscopical 
 Society, and the following extract from his paper describes 
 the matter so clearly that all will be able to follow his 
 directions : — 
 
 " Most working microscopists have felt the necessity, in 
 reading papers on their work, of accurate illustration. 
 These enlarged drawings fail in matter of detail, unless 
 extravagant labour is expended, and considerable skill 
 employed. Even then the light of an ordinary lecture 
 hall is not enough to enable the most distant of the 
 audience to see them. It is only by means of the limelight 
 and transparencies that really useful illustrations can be 
 given. But here the difficulty is to prepare them accu- 
 rately and inexpensively. Photography cannot be employed 
 in all cases ; and even where it can be, it involves more 
 labour than most microscopists can afford. Drawing and 
 painting on glass in the usual method is an art that it takes 
 years to learn \ and to employ one who has learned it to 
 draw from nature a highly-magnified object, would be to 
 introduce unnumbered errors of interpretation, unless our 
 artist be a microscopist himself. 
 
 " I obviate all these difficulties by the following method : 
 On finely-ground glass, drawing with a black lead pencil 
 is as easy as drawing on London board. I get four inch 
 squares of glass to suit my lantern, carefully ground on 
 one side like the focussing glass of a camera. Now with 
 
 h2 
 
100 
 
 THE BOOK OF THE LANTERN. 
 
 the ground side up, the camera lucida may be used with 
 this as well as with drawing-board, if a piece of white 
 paper be placed beneath it, and the object drawn in the 
 usual way. For outlining and delicate shading I employ 
 H H H H and H II H pencils ; for deep shadows I use 
 H B. By a very delicate employment of the pencil, 
 shadows softer than can be secured by lithography may be 
 made. The camera lucida, of course, is not necessary ; we 
 may draw with the eye and hand alone. If it be necessary 
 to put on colour it may be done cleanly and carefully over 
 the shading ; thus one layer of colour suffices. Now of 
 course, although we have a perfect drawing of the object, 
 with all the detail accurately given, it is not a transparency. 
 But we can easily make it one Thin some good pale Canada 
 balsam with benzine to about the consistence of eream ; 
 and simply float it over the ground surface of your glass, 
 pour off till the drop comes very sluggishly. Then reverse 
 the glass so that the corner from which the balsam was 
 flowing off be placed upward. Let the return flow reach 
 about the middle, then reverse it again, and move it in 
 several directions to get the balsam level. This may be 
 done with very little practice so that the surface shall be 
 undistinguishable from glass. We have now a perfect 
 transparency. All that is required is twenty four hours 
 for hardening (keeping the glass level) and then another 
 square of glass fastened on to it by strips of paper afc the 
 edges, with small pieces of card at the corners to prevent 
 contact, and it makes an admirable lantern transparency. 
 
 "For obtaining very fine points to my very hard leads, after 
 cutting them very loner and even, and grinding them on 
 
THE BOOK OF THE LANTERN. 
 
 101 
 
 glass paper, I finish them on a square of the finest ground 
 glass, and with this beside one in making a delicate 
 drawing, a good, fine working point may be kept a long 
 while." 
 
 There is sometimes a difficulty in procuring ground-glass 
 fine enough for this purpose, and I therefore advise those 
 who feel inclined to try this method of producing lantern- 
 slides to prepare the glass themselves ; which is somewhat 
 tedious, but by no means difficult. Or should they prefer 
 it, they can purchase the glass at certain photographic 
 warehouses, where it is sold for focussing purposes in the 
 camera ; but it is rather expensive. The following direc- 
 tions will enable any one to grind the glass for himself : — 
 
 First of all, obtain a piece of glass which is both flat and 
 perfectly free from bubbles and other flaws. Be careful, 
 too, to cut it to the correct size at this stage of the proceed- 
 ings, so as to avoid all risk of mistake in this direction 
 after it has been ground. The glass is now fixed on a 
 table or board by means of four pieces of wood, nailed on 
 the board or table so as to clip its four sides. These 
 wooden pieces must not be thicker than the glass itself. 
 Now procure a piece of plate-glass measuring about three 
 inches square, to act as a grinder. Failing this, a piece of 
 ordinary sheet-glass can be employed ; but, as it will not be 
 thick enough to afford a proper hold for the fingers, it 
 should have attached to it a pneumatic india-rubber plate- 
 holder to serve as a handle. 
 
 Now take some flour emery and mix it into a thin cream 
 with water. Put some of this on the glass, which you have 
 fixed to the table, and place the grinder above it ; rub the 
 
102 
 
 THE BOOK OF THE LANTERN. 
 
 latter over the former with a steady circular motion, taking 
 care to cover every part in turn. This rubbing should 
 be continued for about ten minutes, adding water if the 
 two surfaces seem inclined to stick together too much, and 
 occasionally collecting with a knife-blade the mud which 
 oozes out between them, and putting it once more in the 
 centre of the under glass. At the end of the time 
 named the glass can be lifted from the table, held under 
 the tap for a few seconds so as to clean it, and care- 
 fully examined by transmitted light. It will most probably 
 show a fine grain, except in certain parts, which remain 
 clear as before. These clear portions are depressions in 
 the surface of the glass, which the emery has failed to 
 reach. The grinding operation must be repeated as before 
 until on examination these clear places have disappeared. 
 
 It has occurred to me that Dr. Dallinger's system of 
 producing lantern- slides might be modified with advantage 
 in the following manner. Coat the glass with varnish 
 which dries with a mat surface, and practically gives the 
 same effect as ground-glass itself. There are several 
 recipes for such varnish, which is used by photographers for 
 retouching purposes. Here is one which will be found 
 effectual. 
 
 Ground- Glass Varnish. 
 Sandarac ... ... ... 90 grains. 
 
 Mastic ... ... ... 20 „ 
 
 Ether 2 oz. 
 
 Benzole ... ... ... \ to \\ oz. 
 
 The proportion of benzole added determines the nature of 
 the mat obtained. 
 
THE BOOK OF THE LANTERN. 
 
 103 
 
 The varnish is simply flowed over the glass and allowed 
 to dry cold, which it will do in a very few minutes. 
 After it is thoroughly hardened it can be drawn upon 
 with a pencil in the way described, and can then be 
 coloured with water colours tempered with ox-gall, as 
 pointed out. We can now make the picture transparent by 
 the addition of another varnish, which must be of such a 
 composition that it will not dissolve or in any way act upon 
 the surface already laid upon the glass. Such a varnish 
 would be represented by one not containing benzine as a 
 solvent for its gums. .1 have not tried this method myself, 
 and so cannot speak from experience ; but I do not see any 
 reason why it should not succeed. 
 
; OHAPTEE VIII. 
 
 PHOTOGRAPHIC LANTERN PICTURES BY THE WET PROCESS. 
 
 [ANTERN slides made by the wet process are 
 certainly easier to produce than those made by 
 any dry method. It is a matter of opinion 
 whether these are better in quality than their rivals on 
 gelatine, &c, and I know that many believe that a far 
 better effect is producible upon a wet plate than upon a 
 dry plate. I myself am of the contrary opinion ; but still, 
 as there may be many who may be inclined to try the old 
 collodion method, my work would be incomplete if I did 
 not give directions by which such slides can be produced. 
 
 If the negatives are of the same size as the lantern 
 plate ; that is to say, if they consist of quarter plate nega- 
 tives, they must be reproduced by contact ; and actual 
 contact with a wet collodion film is of course out of the 
 question. 
 
 There is a method by which this difficulty can be ob- 
 viated. Attach to the negative a couple of strips of note 
 paper, 3-g- inches apart ; the collodion film can then rest 
 against these paper supports by two of its edges during 
 
THE BOOK OF THE LANTERN. 
 
 105 
 
 the necessary exposure ; but in this case care must be 
 taken that the plate is thoroughly well drained, for a drop 
 of the silver bath solution, if allowed to get into actual 
 contact with the negative, will inevitably spoil it. 
 
 But those who advocate the wet process for lantern- 
 slide work nearly always work from larger negatives 
 with the camera, and by following the directions now 
 given it will be found that very good results can be 
 obtained. 
 
 Place the negative to be copied in a suitable frame 
 against the window. This can be done by fixing an ordi- 
 nary printing frame (with the spring removed) against 
 the glass, and by covering up the rest of the window- 
 panes with brown paper, or some other opaque material. 
 Then support the camera on a stand or table, exactly op- 
 posite the negative, taking care that it is square with the 
 negative and carefully focus the image on the ground glass. 
 A focussing glass is a very great help in this work, for the 
 image is often so dimly illuminated that it is difficult to 
 ascertain whether it is sufficiently sharp or not. With 
 regard to exposure, it is very difficult, in fact impossible, to 
 * lay down any hard-and-fast line. I can only say that 
 with a negative of normal density and with a favourable 
 light, the exposure should be about one minute ; but it is 
 of course governed by the type of lens used, and the par- 
 ticular stop employed with that lens. With a portable 
 symmetrical of 5 -inch focus and using No. 4 stop, the 
 exposure with a normal negative will be about that which 
 I have indicated. 
 
 But the great thing which ensures success in this process 
 
106 
 
 THE BOOK OF THE LANTERN. 
 
 is to use a proper developer and a bath which is in the 
 right condition. This bath should be an old one ; that is 
 to say, not a newly mixed one, — one, in fact, which would 
 give very hard results for ordinary portraiture. 
 
 It should have a tmall quantity of nitrate of baryta 
 mixed in it, say 3 grains to the ounce of bath. 
 
 Develop with sulphate of iron sat. sol. ... 4 oz. 
 
 Methylated spirit 4 oz. 
 
 Add these to a Winchester quart of distilled or rain 
 water ; and allow it to stand in the light for some hours, 
 next filter it -into a clean bottle, and add 4 drops of 
 colocine. 
 
 Just before using this developer add to it one drop of 
 acetic acid per ounce. This addition ensures a very fine 
 deposit, without it the deposit may be granular. The 
 exposure should be so regulated that no subsequent intensi- 
 fication is required, but if an error of judgment should be 
 made the image can be strengthened by adding a drop of 
 the silver bath to a little of the developer and flowing 
 it over the plate. The glass used should be the 
 best, and quite free from flaws of any kind. " Flatted 
 Crown " answers this description. It should be care- 
 fully cleaned and albumenised. The albumen should 
 be flowed over one side of the glass only, and it should 
 consisJ of the white of one egg to a pint of water, with 
 the addition of one drop of carbolic acid. 
 
 A quantity of broken glass should be placed in this 
 bottle and the whole shaken up into froth, left to settle and 
 then filtered through cotton wool. As the plates are coated 
 with this albumen mixture, they should be reared up to 
 
THE BOOK OF THE LANTERN. 
 
 107 
 
 drain, and dry spontaneously on a slip of blotting paper. 
 The best collodion to nse is " Mawson's Negative Col- 
 lodion." The plates should be fixed in hypo of the usual 
 strength, and should the image appear to be " dirty " it 
 can be rendered clear by being washed over with a solution 
 of iodine and iodide of potassium. 
 
 After fixation and after the plates have been thoroughly 
 washed, they may be toned in a solution of chloride of 
 platinum, — one grain to 4 ounces of water, and they 
 should remain in this solution until the deposit is darkened 
 throughout. 
 
 Beginners very often fail in getting a good tone from 
 platinum, and complain that instead of darkening the 
 image the salt has the opposite effect. They are recom- 
 mended in some formulae to add nitric acid to the toning 
 bath, but this is useless unless the platinum salt be 
 neutralised in the first instance. The proper mode of 
 procedure is to -break the tube containing the platinum 
 crystals (this chemical, like chloride of gold, is on account 
 of its deliquescent property always sold in an hermetically 
 sealed glass tube) into a certain quantity of distilled water. 
 A convenient plan is to break a tube containing 1 5 grains 
 into 15 drachms of distilled water : one drachm of the 
 liquid will then represent one grain of platinum chloride. 
 Test this liquid before use with litmus paper: if it show by 
 the paper turning red that it is acid, we may be quite sure 
 that it contains free hydrochloric acid, which will have a 
 bleaching effect upon the photographic image. The liquid 
 must therefore be neutralised by the addition of a few 
 grains of carbonate of soda, after which it must be 
 
108 
 
 THE BOOK OF THE LANTERN. 
 
 lendered sufficiently acid with 'nitric acid to slightly redden 
 litmus paper. If the operator is careful to follow these 
 directions he will have no difficulty in toning his trans- 
 parencies with platinum. 
 
 We may summarise the order of operations as follows : 
 Albumenise the glass. 
 Dry. 
 
 Coat with collodion. 
 
 Sensitise in silver bath. 
 
 Expose. 
 
 Develop. 
 
 Fix in hypo. 
 
 Wash. 
 
 Clean with iodide solution if necessary, 
 
 Tone with platinum. 
 
 Wash. 
 
 Dry. 
 
 The operations conclude with giving the film a coat of 
 transparent varnish. Any good varnish may be used, but 
 care must be taken if the slides are to be subsequently 
 coloured, that some varnish upon which turpentine has no 
 action be employed ; otherwise the turpentine used in 
 colouring will most surely mingle with the varnish and 
 ruin the picture. 
 
 It is hardly necessary to add that the operations of sen- 
 sitising, developing, and fixing the plate must be conducted 
 in a non-actinic (red) light, and that all precautions usually 
 taken in dealing with photographic chemicals must be 
 observed. The directions are written for those who have 
 already mastered the details of such work. 
 
CHAPTER IX. 
 
 LANTERN SLIDES ON DRY PLATES. 
 
 HERB are many dry collodion methods which 
 a were originally designed for ordinary nega- 
 tive work in the camera, but which have 
 ]ong ago been superseded by the far quicker and 
 more certain gelatine process. Some of these plates, 
 however, although they have been discarded for the 
 main purpose of photography, are still used by many 
 workers for the manufacture of lantern-plates where great 
 speed is a matter of secondary importance. 
 
 For many of these processes the silver bath is still 
 required, the plate after being sensitised therein, being 
 flowed over with some preservative solution, the function 
 of which is to keep the pores of the collodion film in such 
 a condition that it will not dry into a horny state, im- 
 permeable to any developer which may later on be 
 applied to it. As full particulars of these processes can 
 be found in most photographic text-books, I shall content 
 myself with giving here only a brief survey of them, 
 reserving details of working for the more modern methods 
 of producing lantern-slides on gelatine plates. 
 
110 
 
 THE BOOK OF THE LANTERN. 
 
 Many of these old processes differ only in the kind of 
 preservative fluid applied to them, and from the nature 
 of this preservative they usually are named. Thus we 
 have the Tannin process, the Honey process, the Coffee 
 process, &c. Taking the first named, let me cite it as an 
 example of the others. 
 
 The glass -plate which is to bear the picture is first of all 
 carefully cleaned. It is then edged with india-rubber 
 solution, albumen, or some other body which will prevent 
 the film from slipping off the glass during subsequent 
 operations. Next it is coated with ordinary negative 
 collodion, to which two grains per ounce of bromide of 
 cadmium may be advantageously added. It should now 
 be dipped in a silver bath which has been made distinctly 
 acid, by the addition of a few drops of nitric acid. After 
 thus sensitising the plate, it must be well washed to remove 
 all free silver, after which the preservative is applied, — 
 
 After the plates are dry they are ready for use, but will 
 only remain good for a week or two. 
 
 In another process which gives good results coffee is used 
 as the preservative. In this case the bath can be made 
 very acid, by the addition of one -fifth of its volume of 
 glacial acetic acid. The plate is edged, and sensitised in 
 the bath, and is then flowed over with an infusion of 
 ground coffee, After drying, these plates will keep for 
 some months, and will give fine results. The development 
 is brought about by a plain solution of pyrogallic acid, 
 
 Tannin 
 
 Distilled water 
 
 • • • 
 
 35 grains. 
 4 ounces. 
 
THE BOOK OF THE LANTELIN. 
 
 Ill 
 
 say two grains to the ounce of water, and is afterwards 
 strengthened by citric acid and silver. 
 
 A far greater importance is attached to the next method 
 under disscussion, by which the very finest results can be 
 obtained ; but it requires, at every stage of the process, 
 such great care that few in these days care to take it up. 
 Still it has a commercial importance, and is known as the 
 Albumen process. Here is a sketch of the operations in- 
 volved in it. 
 
 After the plate of glass has been rendered chemically 
 clean it is coated with a film of albumen from fresh eggs, 
 to which has been added some iodide and bromide of 
 potassium. The plate is then inverted on its pneumatic 
 holder, and revolved by means of a vertical cord attached 
 to the bottom of that holder, so that by centrifugal force 
 some of the albumenous coating is scattered, leaving the 
 thinnest possible film on the glass. The plate is then 
 dried, — as yet insensitive to light. Next it is immersed 
 in an acid silver bath for about three minutes, and after 
 washing with several changes of water, a preservative 
 consisting of a saturated solution of gallic acid, is applied 
 to it. Drying by gentle heat completes the manufacture 
 of this form of plate. The development is brought about 
 by a saturated solution of gallic acid, to which has been 
 added a few drops of silver nitrate. 
 
 C0LL0DI0-BE0MIDE PROCESS. 
 
 We will now give our attention to the beautiful 
 Collodio -bromide process, a brief description of which is 
 only necessary, for the collodion emulsion for the lm- 
 
112 
 
 THE BOOK OF THE LANTERN. 
 
 mediate coating of the plates can be bought ready made, 
 with full instructions for coating and development. 
 
 This rr.ethod yields results which cannot easily be beaten. 
 It was introduced about twenty years ago by Messrs, 
 Bolton & Sayce, and a number of good workers have 
 since taken it up successfully. As its name implies, a 
 collodion is employed containing bromide of silver, and 
 although many might be deterred from attempting it, from 
 the fancied difficulties which it presents ; yet, in practice 
 it is by no means a complicated process to work. It has 
 certainly a great many advantages. When the sensitised 
 collodion is once compounded it will keep for a long time. 
 Plates can be coated with it — a dozen at a time if required 
 — and after being dried by artificial heat are ready for 
 immediate use. When the printing from the negative has 
 been performed, these plates, after development and a 
 minute's washing, can be dried, and the slides are finished 
 and ready for the lantern. 
 
 A plain collodion is first of all made with high tempera- 
 ture Pyroxyline, and the usual solvents, ether and alcohol. 
 To this is added ammonium-bromide and citric acid. The 
 silver 'is now dissolved in as little water as possible, and is 
 added to the bromised collodion. The emulsion is then set 
 aside to ripen for some hours, is poured out into a dish for 
 the solvents to evaporate, and is then broken up into small 
 pieces and washed in several changes of water, so as to get 
 rid of the soluble salts which are not required. All these 
 operations are, of course, conducted in non-actinic light. 
 When these pieces have been finally drained as closely as 
 possible, they are once more dissolved in the requisite pro- 
 
THE BOOK OP THE LANTERN. 
 
 113 
 
 portions of ether and alcohol, and, after filtering, the re- 
 constructed emulsion is ready for coating the plates. They 
 can be developed by a weak alkaline developer with pyro, 
 or by the ferrous -oxalate method, which will be described 
 later on, Mr. W. Brooks, of Reigate, has made a study 
 of this process, and supplies the emulsion ready made. 
 Messrs, Mawson and Swan have also lately advertised it, 
 so that it is hardly worth while for the worker to make it 
 for himself, 
 
 WOODBURYTYPE PROCESS. 
 
 This method yields results which cannot be sur- 
 passed, but it may be looked upon more as a com- 
 mercial process than one suited to the amateur worker, 
 for it necessitates the use of expensive plant. I shall 
 therefore dismiss it with a somewhat brief description, 
 albeit my chapters on slide-making would hardly be com- 
 plete without it, In the first place a relief is obtained by 
 employing gelatine, containing one of the bichromates of 
 the alkalies — bichromate of potash, for instance. This 
 relief is placed upon a sheet of lead, and after the two 
 have been fixed in a steel frame, they are submitted to 
 hydraulic pressure, with the curious result that the tender 
 gelatine film preserves its delicate outlines, but the leaden 
 plate gives way, and these markings are pressed into it, 
 This leaden plate then forms a mould of the future picture, 
 its deepest parts representing the shades of that picture, 
 and its higher parts the lights. This is placed in a special 
 press, and a pool of gelatinous ink (made by dissolving any 
 suitable pigment in a warm solution of gelatine and water) 
 
 I 
 
114 
 
 THE BOOK OF THE LANTEKN. 
 
 is poured upon the mould. The square of glass which is 
 to bear the picture is placed on this pool of ink, and the 
 press is lightly brought down upon all. The slide is left 
 thus until the gelatine has had time to set, when the 
 glass is lifted from the mould, and the picture in all its 
 delicate details is left upon it. This beautiful process, 
 which may be looked upon as the most perfect of all the 
 mechanical photographic processes, was due to the genius 
 of the late Mr. Woodbury, who, shortly before his lamented 
 death, modified it so that it might be practised by ama- 
 teurs, 
 
 This modification is known as the Stannotype pro- 
 cess, tinfoil being employed as a substitute for the work of 
 the hydraulic press. The gelatine relief is attached to a 
 plate of glass by a suitable cement, Its surface is then 
 coated with india-rubber cement, and a sheet of ordinary 
 tinfoil is placed above it. The whole arrangement is now 
 passed between a couple of india-rubber rollers, such as 
 are attached to a domestic wringing-machine, so that the 
 tinfoil is forced into the interstices of the picture, We 
 thus obtain a metallic-faced mould without the interven- 
 tion of the hydraulic press, and this mould is afterwards 
 treated with warm gelatinous ink, and prints taken off, as 
 in the Woodburytype process. In the latter process, how- 
 ever, a negative is employed to give the necessary relief, 
 and in the Stannotype a positive. Both of these methods 
 give the best results for pictures where there is not a large 
 expanse of sky, or other high light; for in such a case 
 a slight deposit of the pigmented gelatine is likely to spoil 
 
The book of the lantern. 
 
 115 
 
 the transparency of such lights, and in a good lantern slide 
 they should be represented by clear glass, 
 
 TRANSPARENCIES ON COMMERCIAL GELATINE PLATES. 
 
 For some inscrutable reason, it used to be the common 
 opinion among those who ought to know something about 
 the matter, that the gelatine process is unsuitable for lan- 
 tern transparencies. The introduction lately of gelatine 
 lantern plates into the market has done much to correct 
 this error ; but still there are numerous persons who hold 
 to the belief that the ordinary gelatine plate, such as is 
 used for negative work, will not produce a good trans- 
 parency. For years I have proved the contrary, and with 
 regard to the quality of the transparencies produced, I have 
 seen few to equal them. 
 
 The first operator who turned out successful work of this 
 character was Mr. Kennett, who has the greater honour 
 of being the first to make gelatine plates a marketable 
 commodity. His method of working was to employ a slow 
 plate, to expose it under a negative in a printing frame for 
 the fraction of a second in daylight, or for a longer time 
 by lamplight, and to develop by either the alkaline or 
 ferrous oxalate method. The plate was afterwards flooded 
 with pyro and silver and toned with gold. 
 
 The introduction of chloride plates, which give beautiful 
 effects, may deter some from trying what can be done by 
 ordinary gelatino -bromide plates. But for the amateur 
 whose time is otherwise occupied during daylight, the latter 
 process has many advantages. The chief one is that, while 
 
 I 2 
 
116 
 
 THE BOOK OF THE LANTERN. 
 
 the exposure of a chloride plate to lamplight will occupy 
 about three minutes, a bromide plate can be successfully 
 exposed in less than three seconds, so that a number can 
 be exposed in an hour or two. 
 
 I have already pointed out how a reduced positive can 
 be readily obtained from a negative by means of the 
 camera. I will now suppose that the negative from which 
 the transparency is to be taken, is on a ^ plate, and, there- 
 fore, the right size for the lantern slide, and that the pic- 
 ture is to be printed by contact in a printing frame. 
 The requirements are a red lamp, a gas or paraffin 
 lamp, which can be readily turned up and down, and a 
 frame. 
 
 As in most photographic operations, correct exposure is 
 the main consideration, but whereas where daylight is 
 concerned, this exposure is always difficult to hit upon, 
 because the light varies so much under different circum- 
 stances ; here, where we have a lamp to work by, we can 
 measure its duration to a nicety. 
 
 I may mention here that there is a form of gas-burners 
 sold which is very useful in this work. It is fitted with a 
 bypass, so that it is never actually turned out. A blue 
 bead of light remains, which is quite shielded from view, 
 and this permanent flame ignites the full amount of gas 
 when the stop-cock is turned on. The operation of print- 
 ing a transparency consists in placing the negative in the 
 frame, and placing upon it, film to film, a gelatine plate, 
 measuring 3^ x 3J inches. The frame is closed, and is 
 h eld j within a short distance of the lamp, which is turned 
 
THE BOOK OF THE LANTERN. 
 
 117 
 
 up for a brief period, and then turned down to darkness 
 once more. But how must this period be measured ? In 
 order to answer this question I must call attention to a 
 certain optical law which I have attempted to put in the 
 form of diagrams : — 
 
 Fig. 38. 
 
 Fig. 38 illustrates the manner in which the light rays 
 from a candle strike out all round it like the spokes of a 
 wheel ; but, for simplicity sake, the rays in one direction 
 only are shown. Let A represent our printing frame held 
 at 1 foot from the light source, and let us suppose that 
 at that distance the plate contained in it will require one 
 second's exposure. Now let us expose a similar plate at B, 
 which is 2 feet from the light source, what exposure will 
 it require? "Two seconds," the tyro will probably 
 answer ; but he would be wrong, the plate at double the 
 distance will require four times the original exposure ; at 
 treble the distance, nine times the original exposure. In 
 
118 
 
 THE BOOK OF THE LANTERN. 
 
 other words, " the intensity of illumination on a given sur- 
 face is inversely as the square of its distance from the source 
 of light." 
 
 Fig. 39. 
 
 Fig. 39 will perhaps make the matter still more plain. At 
 1 foot from the candle the square marked i receives a 
 certain amount of light ; at II, that light is spread over a 
 surface four times the area of the first ; and at in over a 
 surface nine times as large as I. This law, which is really 
 of a very simple character, the operator should have con- 
 stantly in his mind, as he exposes his plates to artificial 
 light under a negative. 
 
 The method of development which I recommend is by 
 means of ferrous oxalate, and it will be found that the 
 transparencies produced by it require no toning whatever. 
 I make my own potassic oxalate, and find it, moreover, 
 reliable ; the operation is simplicity itself. In a large 
 basin dissolve half a pound of carbonate of potash (salts of 
 tartar) in a pint and a half of warm water. Now add 
 gradually oxalic acid, a few crystals at a time, for the 
 effervescence is very violent, and difficult to control if 
 much be put in at once. When six ounces of the crystals 
 
THE BOOK OF THE LANTERN. 
 
 119 
 
 have been so added, set the basin aside for an hour or two, 
 then stir its contents with a glass rod, and test with blue 
 litmns paper, adding crystals of acid until the paper turns 
 slightly red. Add to the liquid 30 grains of potassic 
 bromide, allow to settle, and bottle off for use when clear. 
 
 But those who wish to avoid the trouble of making 
 their own potassic oxalate can buy the crystals at any 
 photographic dealer's, in which case its solution should be 
 made with boiling water, and well stirred until all crystals 
 have disappeared. One pound of oxalate will require 
 just a quart of water to make a saturated solution. If 
 more water be used, the solution will not be a saturated 
 one, and will, when mixed with the iron, throw down a 
 muddy red precipitate, and be useless for developing pur- 
 poses. The iron must be added to the potash, and not vice 
 versa, or the same effect will be produced. I have found 
 that with this developer it is always advisable to soak the 
 exposed plate in water as a preliminary step. The gelatine 
 surface then takes more kindly to the solution, and greater 
 density is attained. 
 
 The development should be carried on until the picture 
 looks overdone, for it must be remembered that it has to 
 be ultimately exhibited by transmitted light, and we view 
 it in the developing dish by reflected light only, but hold- 
 ing it up to the red light and looking through it we can 
 judge well when the developing action ought to be stopped. 
 Now follows a rapid rinse under the tap, a few minutes' 
 immersion in alum and water, and fixing in fresh hypo. 
 If ordinary household water has been used, the film will 
 show a milky veil. This is quickly removed by a ten per 
 
120 
 
 THE BOOK OF THE LANTERN. 
 
 cent, solution of sodic citrate, poured on and off, and gently 
 rubbed upon the gelatine surface with a plug of cotton 
 wool. This treatment is not necessary if rainwater is 
 available. Messrs. Mawson and Swan supply an admirable 
 plate for lantern-slide work. It can be used for reducing 
 in the camera, or for contact printing, and is amenable to 
 more than one method of development. 
 
 At one of the exhibitions this firm showed a specimen 
 frame of four transparencies from one negative, — each 
 developed by a different formula, and showing a difference 
 of tint for each. 
 
 I append two of these formulae : — 
 
 A. — Meta Bisulphite Developer. 
 
 B. — Carbonate Soda „ 
 
 A. 
 
 I. 
 
 Pyrogallic Acid 40 grs. 
 
 Meta-bisulphite Potass 120 „ 
 
 Bromide Ammonium ... ... ... ... 40 „ 
 
 Distilled Water 20 ozs. 
 
 IT. 
 
 Liquor Ammonia ... ... ... ... 2^ drms. 
 
 Distilled Water 20 ozs. 
 
 Mix equal parts of A and B just before using. 
 
 B. 
 
 L II. 
 
 Pyro 40 grs. Carb. Soda 1 oz. avd. 
 
 Sodic Sulphite ...180 „ Sodic Sulphite ... 1 
 
 Brom. Potass 20 ,, Distilled Water ... 20 „ fluid. 
 
 Hydrochloric Acid ... 40 mins. 
 Distilled Water up to 20 ozs. 
 
 Equal parts. 
 
 Between development and fixation immerse plate in Sol. of Alum, 
 1 oz. in 20 ozs. water, washing carefully before and after. 
 
THE BOOK OP THE LANTERN. 
 
 121 
 
 Messrs. Samuel Fry and Co., also make a thoroughly 
 reliable lantern plate which is suited to both camera and 
 contact work. It is amenable to more than one developer, 
 but I prefer that in which hydrokinone takes the place of 
 pyro. Here is their formula : — 
 
 A. 
 
 Hydrokinonp, best quality ...* „ # ... 150 grs. 
 Sulphite Soda ... ... ... ... ... 440 „ 
 
 Brom. Pot. ... ... ... ... ..♦ ... 25 „ 
 
 Water — To make a total bulk of 20 ozs. 
 
 B. 
 
 Carb. Soda (not Bicarb.) ... 900 grs. 
 
 Oarb. Potass ... ... , ... 900 „ 
 
 Water — To make a total bulk of ... ... 20 ozs. 
 
 These solutions do not require further dilution. 
 
 For Use. — Take equal quantities of each. The mixed solution 
 should be colourless, and can be used repeatedly, and until the 
 developer fails to render details satisfactorily. 
 
 LANTERN SLIDES FROM PAPER PRINTS — ENGRAVINGS OR 
 PHOTOGRAPHS. 
 
 There are certain main principles to be observed in 
 copying a photograph, or any other kind of picture, if a 
 satisfactory negative, fit for printing a lantern slide from, 
 is to be expected. The copy should be illuminated by 
 diffused light only, and should never receive the direct 
 rays of the sun. A cloudless day is the best to choose, 
 for then the light is regular, and when the exposure has 
 been correctly calculated for the first picture, it will, during 
 some hours of the day, be right for the rest. At least this 
 is true, if we are copying a series of pictures of the same 
 dimensions. But, if our first copy is, say, 12 inches across 
 and our next one only carte de visite size — and we want to 
 reproduce a negative of each, measuring 3J x 3| (the 
 standard size for lantern pictures), our camera must in the 
 
122 
 
 THE BOOK OF THE LANTERN". 
 
 latter cases be so much extended that the exposure must 
 be proportionately increased. 
 
 A picture under glass will seldom give a good result 
 for the surface will take up reflections from surround- 
 ing objects, which may not perhaps be noticed on the 
 focussing screen, but which will most surely become dis- 
 agreeably evident in the negative. A highly glazed 
 albumenized print is objectionable for the same reason, 
 but can be generally coaxed into a position in which no 
 mischief of the kind is apparent. Steel engravings have no 
 gloss, but they seldom make good pictures for the lantern 
 screen, their details being too fine. A first-class wood 
 engraving is far better for the purpose, and as its value is, 
 as a rule, not very great, it can be judiciously touched up 
 before being photographed. Perhaps the artist of such a 
 picture would be horrified at his work being thus interfered 
 with, but the touching up indicated is quite legitimate. 
 Let me further explain my meaning. Suppose that in one 
 of our illustrated periodicals there is a representation of 
 some current event which we want for our lantern. If it 
 is an interior view, it will probably require no doctoring. But 
 if a landscape, or a group of figures with a sky back- 
 ground, then certain parts should be suppressed. The sky 
 is not white, but consists of a number of parallel lines with 
 clouds interspersed ; effective enough in the print, but not 
 suitable for reproduction in an enlarged form. These lines, 
 which seem to mingle so well, giving the effect of a general 
 soft " tint/' will on the lantern sheet look like what they 
 really are — a series of detached bars right across the picture. 
 To get rid of these lines, the outline of the figures, and 
 
THE BOOK OF THE LANTERN. 
 
 123 
 
 other objects which stand against the sky, should have a 
 broad margin painted round them in Chinese white, leaving 
 the main body of the sky to be blocked out with black 
 varnish in the negative itself. 
 
 I have done excellent work with Ross's portable sym- 
 metrical lens No. 3 — which has a focus of 5 inches. Of 
 course, other lenses will do well for copying, but if of 
 longer focus, the camera must have an extending front 
 fitted to it. Very few cameras pull out long enough to 
 photograph a very near object, unless a short focus lens is 
 employed. As a guide to exposure, I may mention that 
 in copying wood-cuts and photographs with the above- 
 named lens, and using a fairly-rapid gelatine plate, it 
 averages 17 seconds with stop No. 4. It is as well to focus 
 with full aperture of the lens, and to insert the stop just 
 before exposure. One more hint. It is sometimes very 
 difficult to sharply focus a soft photograph which has no 
 sharp lines in itself. The difficulty is obviated by affixing 
 to the middle of the copy any little piece of printed matter, 
 wetting it with the tongue for that purpose. Only be 
 careful to remove it before exposure, or your negative will 
 faithfully record the little dodge. 
 
 It would seem a very simple matter, to one who has not 
 tried it, to fasten a picture upon a wall in a good light, 
 stand the camera on its tripod in front of that picture, and 
 proceed to copy it. But difficulties crop up when we want 
 to reduce that picture to a certain size, and to keep the 
 camera square with the copy, so as to prevent distortion. 
 With head beneath the focussing cloth, the struggle to 
 adjust the tripod legs is quite distressing. I myself found 
 
124 
 
 THE BOOK OF THE LANTERN. 
 
 so much difficulty in getting the camera into the exact 
 position required, that I constructed a special piece of 
 apparatus for the sole purpose of copying. To this acces- 
 sory, which works most perfectly, I now direct atten- 
 tion. It is simple in construction, and anybody who knows 
 how to handle a few tools can put it together with ease. 
 The amateur may prefer to employ a professional carpenter, 
 but there is always a difficulty in getting the British work- 
 man to make anything that is at all strange to him. My 
 advice is, therefore, if you want the thing done well do 
 yourself (see fig. 40). 
 
 Fig. 
 
THE BOOK OF THE LANTERN. 
 
 125 
 
 A is a base board, fixed on legs, as shown. It will be 
 evident that a spare table, or even the top of a packing- 
 case, wonld do as well, bnt it must be firm. Upon this base, 
 and fixed firmly to it, is a kind of railway formed by two 
 parallel grooves. D is a skeleton carriage fnrnished with 
 two rnnners at the bottom which will fit the grooves in 
 A, so as to rnn easily to and fro. The carriage D is also 
 furnished with grooves, and these are for the reception of 
 the runners affixed to the super-carriage, E. Upon E is 
 fastened the photographic camera, the camera screw being 
 placed through the centre hole for that purpose. 
 
 In use, the picture to be copied is pinned to the back- 
 board, F, and I may mention as a detail of some im- 
 portance, that the little bead-headed arrangements known 
 to drapers as " ladies 1 bonnet- pins " are best for the purpose. 
 The camera is placed on E, E on D, and D placed on the 
 rails of the baseboard, A. We thus have two separate 
 movements at our disposal in getting the image of the copy 
 focussed centrally on the ground glass. A furnishes the 
 to and fro movement, and the grooves on D give the right 
 and left movement. The board, F, runs between upright 
 grooves, and thus we have a vertical movement. With 
 this simple contrivance a picture can be focussed in a few 
 seconds, and the camera all the time is bound to keep square 
 with the copy. A 3 -inch circle drawn in pencil on the 
 ground-glass of the camera is useful as a reminder of the 
 size to which the picture must be reduced. 
 
 Lastly, this useful contrivance can serve another pur- 
 pose. We may wish to obtain a reduced positive on glass 
 from a larger negative. We can do this direct in the 
 
126 
 
 THE BOOK OF THE LANTERN. 
 
 camera by placing the negative to be copied in an opening 
 in the board, F, marked by a dotted line in the illustra- 
 tion. A couple of laths can then be placed above, so as to 
 rest at one end on the camera, and at the other end on the 
 top of the board, F. These laths will serve as a support 
 
 Fig. 41. 
 
 for a dark cloth, which can be thrown over all. A sloping 
 piece of white cardboard placed behind F (also indicated 
 by a dotted line) will throw reflected light from the sky 
 through the negative. I give no dimensions for this copy- 
 ing machine, for the maker must be guided by the size 
 of his camera, the focus of his lens, and his general 
 requirements. A compound frame for negatives of various 
 sizes, as shown in fig. 41, makes this copying-machine 
 complete. 
 
CHAPTER X. 
 
 HOME-MADE GELATINE PLATES. 
 
 LL makers of commercial gelatine plates put for- 
 ward the quality of rapidity as being the one 
 thing needful in modern photography, and ad- 
 vertise their wares as being ten, twenty, or even sixty 
 times as quick in operation as the old wet collodion 
 process. Such rapid plates are not the best for trans- 
 parency work, and as no maker will acknowledge that 
 his plates are slow, — although opinions may be divided 
 upon the matter, — and as slow plates are the most 
 suitable for lantern slides, the operator who aims at the 
 best work may wish to try his hand at making them for 
 himself. Of the many f ormulse which I have tried for this 
 particular purpose, I prefer that first introduced by Dr. 
 Eder, which I have slightly modified. Gelatine plate 
 making is by no means easy work, but the method which 
 I am about to describe presents fewer difficulties than 
 most others. 
 
 The apparatus required need only be of a very homely 
 
128 
 
 THE BOOK OP THE LANTERN. 
 
 nature, and such as can be found in most households. 
 Here is the list : — An earthenware pot with a cover to it, 
 of about one pint capacity ; a glass tumbler ; a preserving- 
 pan or saucepan standing on a tripod, with a spirit-lamp 
 or Bunsen flame beneath it; a thermometer, two glass 
 stirring rods, a square of Berlin-work canvas, an earthen- 
 ware colander, and a dish. In the earthenware pot put 
 the following : — 
 
 Gelatine 110 grains. 
 
 Potassic Bromide... ... ... 62 „ 
 
 (Ten per cent.) Solution of Salicylic Acid in Alcohol, £ ounce. 
 Water 2 ounces. 
 
 I recommend the use of either Autotype, the Swiss, or 
 Henderson's make of gelatine. After being weighed it 
 should be cut up into strips with scissors and placed in the 
 jar with the other ingredients. With a glass rod press 
 down the gelatine into the water y so that every particle of 
 it is wet and softened. Set aside for ten minutes to swell. 
 Now half fill the preserving-pan with warm water, and 
 place the flame beneath it. The thermometer should be 
 placed in the pan, so as to check the temperature, which 
 should not be allowed to rise about 96° Fahr. Place the 
 pot containing the gelatine in the water, taking the precau- 
 tion to put a piece of thick paper beneath it, so that it 
 does not actually touch the heated bottom. 
 
 The gelatine will very gradually melt, and the # opera- 
 tion may be hastened by an occasional stir with the glass 
 rod. Even when it becomes quite limpid, little particles 
 of undissolved gelatine may be floating about in it 
 and these should disappear before proceeding further, or 
 
THE BOOK OF THE LANTERN. 
 
 129 
 
 they will form insoluble particles, which will lead to 
 difficulties later on. In the glass tumbler place — 
 
 Silver nitrate ••• 77 grains. 
 Water ... ... 2 ounces. 
 
 The common tap water employed will, on account of the 
 salts which it contains, turn milky in appearance when the 
 silver is added. This is of no consequence. The crystals 
 can be crushed under the water by another glass rod, 
 and complete solution will soon be effected. (The tyro 
 must be most careful to keep each stirring rod distinct, or 
 he will spoil the entire work.) When the crystals have 
 all disappeared, pour into the silver solution, drop by drop, 
 some strong liquid ammonia, stirring the solution vigorously 
 all the time. The liquid will turn coffee-coloured, owing 
 to a precipitation of silver oxide, but as more of the 
 ammonia is added this precipitate is redissolved, and the 
 solution becomes as clear as ordinary water. Only just 
 sufficient ammonia should be added to accomplish this 
 result. Now place the glass tumbler in the pan beside 
 the vessel containing the gelatine mixture, and leave it 
 there to warm for about fifteen minutes. All the fore- 
 going operations can be conducted in the full light of day, 
 but now, when the two solutions have to be blended to form 
 a sensitive emulsion of bromide of silver, the light of the 
 red room only must be called into requisition. 
 
 The flame beneath the pan, or water bath, is now no 
 longer required, so let it be removed. Take both the gela- 
 tine and silver vessels from the pan, and place them on the 
 table. Now stir the gelatine briskly, and add a small 
 
 K 
 
130 
 
 THE BOOK OF THE LANTERN. 
 
 portion of the silver solution at a time, until all of it is 
 transferred to the earthenware pot. Wash out the silver 
 glass with half an ounce of water and add that too. The 
 newly-formed emulsion should now look like cream. Place 
 the cover on the jar, and put it back once more in the 
 warm water (without any flame beneath it) for fifteen 
 minutes. At the end of that time pour it out into a dish 
 or plate to set, and cover it over so that neither light nor 
 dust can trouble it. This will complete the first stage of 
 plate- making. 
 
 In a few hours, — according to the general temperature, 
 — the emulsion will have set into a firm jelly. It must 
 now be washed to get rid of certain extraneous matter 
 which has been formed and which is not wanted. The 
 silver nitrate has combined with the bromide of potassium 
 to form silver bromide, — the required salt, which is sensi- 
 tive to light,— but at the same time nitrate of potassium 
 (saltpetre) has also been formed, and must be eliminated. 
 As this latter is soluble in water, while the silver bromide 
 is insoluble, the matter is not a difficult one to accomplish. 
 By dividing the jelly into shreds, and putting it into 
 several changes of water, this universal solvent gets to 
 every side of it, so to speak, and the saltpetre is quickly 
 got rid of. Scrape up the jelly with a silver spoon, or a 
 slip of glass, and place it in the middle of the square of 
 canvas, which has' been previously wrung out in water. 
 Gather up the ends so that the jelly forms a ball confined 
 within the canvas. Now place in a large pan of water, 
 and squeeze and twist the canvas with the hands (under 
 water) so that the jelly is forced through the meshes of the 
 
THE BOOK OF THE LANTERN. 
 
 131 
 
 fabric like so much vermicelli. It will presently sink to 
 the bottom of the pan. Wow pour off the water above it, 
 and fill up with fresh. Let the pan rest for five minutes, 
 and repeat the operation half a dozen times. The emulsion 
 must now be strained. 
 
 A square of cambric, the size of a handkerchief, is 
 squeezed in water, and put in the colander, so as to form a 
 lining to it, with the corners hanging outside. Pour the 
 divided emulsion into this, when most of the water will 
 at once run off, and still more may be made to do so by 
 gathering up the corners of the cambric in the hands and 
 gently squeezing the pudding-like mass. Once more open 
 the cloth, and pour into the contained emulsion an ounce 
 of methylated spirit. Again squeeze up the cloth, after 
 which the gelatine shreds can be spooned up, placed in a 
 clean jar, and tied over with a light-tight cover. So ends 
 stage number two. 
 
 There are many who say, with much truth, that the real 
 difficulty of plate-making begins after the foregoing opera- 
 tion of making the emulsion, for a great many fail in the 
 mechanical work of coating the plates, which is the next 
 and final operation. Before this is attempted the decks 
 should be cleared for action. The operator must have on 
 his table a carefully levelled piece of slate or plate glass, 
 large enough to contain at least one dozen plates, laid 
 edge to edge. He will also want a jug with a good lip 
 from which to pour the emulsion, a glass rod to guide 
 it over the plate which he is coating, and a pneumatic 
 holder. The jar of emulsion must first of all be placed in 
 the water bath at the old temperature of 96° for an hour 
 
 K 2 
 
132 
 
 THE BOOK OF THE LANTERN. 
 
 or two, during which time it can be conveniently stirred 
 once or twice (by red light only, of course). If the cover 
 of the jar be really light tight, this melting operation can 
 go on in daylight, and at the same time the glass to be 
 coated can be cleaned. Polish each glass with a little 
 whiting and water, and when dry rub the side to be 
 coated with a leather damped with spirits of wine. This 
 will counteract any repellant action when the emulsion is 
 applied to the glass surface. When all the glasses have 
 been so treated, wrap them in packets of two dozen each, 
 in clean paper, prepared side upwards, and put them on 
 the kitchen hob to warm through. (This latter precaution 
 is only necessary in cold weather.) The emulsion must 
 now be filtered. 
 
 The best form of filter is a lamp chimney with a flange 
 on its lower orifice, over which a piece of damp wash- 
 leather (which has been washed in soda and rinsed in 
 many changes of water) can be tied. When all is ready 
 for commencing to coat, this filter is held over the mouth 
 of the jug (both should be rinsed out with warm water 
 the instant before), and the emulsion is poured steadily into 
 its upper opening. In a minute it will run through the 
 leather into the jug below, and will be quicker in its move- 
 ment if a pressure of air is kept upon it, by applying the 
 lips to the upper end of the glass. Now comes the coating 
 difficulty. 
 
 Let the operator seat himself at his table so that the 
 slate or glass slab is between him and the red light. 
 Place the glass rod in the jug of emulsion, and when in 
 the act of pouring keep the rod back with the thumb of 
 the same hand that is holdingthe jug. Take the topmost 
 
THE BOOK OF THE LANTERN. 
 
 133 
 
 glass plate, fix it on the pneumatic holder, hold it level, 
 and pour a small pool of emulsion in its centre. By inclin- 
 ing the plate a little, the pool will run to the two further 
 corners, and can afterwards be guided across the whole 
 plate with the help of the glass rod. The plate is then 
 slid on to the slab, where it will speedily set, and the glass 
 rod goes back into the jug. Each plate is treated in the 
 same way until the slab is full, by which time its first 
 occupants will have set, and can be reared up to dry in 
 shelves, or a proper drying cupboard. The glass chosen 
 should be as thin and as free from bubbles as possible, and 
 can be of the standard lantern size, 3^ by 3^ inches. But 
 as experience is gained the operator will find it more con- 
 venient and economical of time to coat plates 6| by 6^ inches, 
 which can afterwards be cut across twice with the dia- 
 mond, to form each four lantern slides. 
 
 GELATINO-CHLOKIDE PLATES. 
 
 My own favourite process for lantern slide making is the 
 gelatino-chloride, which has many good points to recom- 
 mend it. It is suitable only for contact printing, there- 
 fore the negatives used must be small ones only. Capital 
 chloride plates can be purchased nowadays ; but for those 
 who prefer to make their own, I can confidently recom- 
 mend the following formula : Mix up the three solutions 
 — A, B, and 0. 
 
 ( Gelatine 
 ( Water (distilled) 
 Silver Nitrate 
 Water (distilled) 
 ( Ammonium Chloride' 
 I Water (distilled) 
 
 300 grains. 
 
 4 ounces. 
 240 grains. 
 
 4 ounces. 
 100 grains. 
 
 2 ounces. 
 
134 
 
 THE BOOK OF THE LANTERN. 
 
 Melt by heat, but not above 120° Fahr. Then in a 
 yellow light, ponr B into A, stirring rapidly all the time, 
 and finally adding 0. Allow the emulsion thua made to 
 remain for one hour, at the temperature already stated, 
 and then put aside in a dish to set. The washing, filtering, 
 and coating operations are the same as those described for 
 bromide plate making. The bright yellow light allowable 
 is a great help to comfortable working of this process. 
 
 Chloride plates are useless, on account of their slowness, 
 where a slide has to be reduced, by means of the camera, 
 from a negative larger than itself. Nor do I advise the 
 amateur to adopt them unless he can work by daylight, 
 or is fortunately situated like one I know, who lives oppo- 
 site to an enterprising tailor who displays an electric arc 
 light in front of his door. For the chloride plate is most 
 insensitive to yellow light, such as that afforded by gas. 
 For this reason, most commercial makers advise that the 
 light chosen should be that procured by burning an inch of 
 magnesium wire at a distance of so many inches from the 
 printing-frame. This advice is not difficult to follow, but 
 it is very difficult to make two pieces of wire give out 
 exactly the same amount of light ; for magnesium wire has 
 a habit of dropping down in a languid manner under the 
 influence of its own heat, and going out suddenly when it 
 ought to shed its radiance abroad. With diffused daylight 
 all is plain sailing. The negative, with its chloride plate 
 in contact with it, is exposed, say, for three seconds to 
 daylight, and is then dropped into the developer. Here 
 is a good one, devised, if I remember rightly, by 
 Mr. Edwards : — 
 
THE BOOK OF THE LANTERN. 
 
 135 
 
 C Neutral potassic oxalate 2 ounces. 
 
 A < Sal ammoniao ... ... ... 40 grains. 
 
 t Water (distilled) 1 pint. 
 
 f Iron sulphate ... ... ... 4 diaohms. 
 
 •p \ Citric acid ... ... ... ... 2 
 
 15 1 Alum 2 
 
 (. Water (distilled) 1 pint. 
 
 For use, pour a portion of B into an equal quantity of A. 
 
 If the operator is accustomed to the ferrous oxalate 
 developer pure and simple, he will find that it will develop 
 this description of plate, but it is better for being restrained 
 with a few drops of 10 per cent, solution of sodic citrate. 
 Whether he use one or the other, let him be particularly 
 careful in the matter of cleanliness of fingers. A hypo- 
 defiled finger will spoil the developer instantly. To avoid 
 this disaster, — the potency of which I have learned by 
 sad experience, — I have adopted the following method of 
 working : — 
 
 I use a brilliant yellow light, so that I can work comfort- 
 ably, for chloride plates are, as already stated, insensitive to 
 yellow rays ; the developing tray stands in front of it, and at 
 one side is placed a large tray filled with water, to which a 
 little alum solution has been added. Hypo is, for the pre- 
 sent banished from the scene altogether. I expose my plate, 
 and put it into the developing solution. In a few seconds 
 the picture flashes out in the unceremonious manner com- 
 mon to chloride plates. I hold it up to the light, look 
 through it, and find that it is but a ghostly image after all. 
 I expose another plate in an adjoining room, and put it by 
 the one which is in course of development, and which by 
 this time has most likely gained sufficient density. If it 
 has, I wash it for a few seconds under the tap, and drop it 
 
136 
 
 THE BOOK OF THE LANTERN. 
 
 into the alum tray ; and so on, until perhaps a couple of 
 dozen plates have been treated in the same way. I then 
 light my gas-lamp, mix up a tray of fresh hypo, large 
 enough to accommodate half a dozen plates at a time, and 
 proceed to fix my plates. They fix rapidly, and as fast as 
 they are done, back they go into the weak alum solution, 
 until, when the batch is finished, I proceed to wash them. 
 This I do by placing them in a metal rack (see fig. 42), 
 and changing the water occasionally during an hour or so. 
 
 Fig. 42. 
 
 GENERAL CONSIDERATIONS — INTENSIFYING AND MOUNTING. 
 
 Hitherto I have said nothing with reference to the best 
 kind of negative for lantern slide making ; the worker will 
 find out, after a few trials, that some of his negatives will 
 yield, without much trouble, a first-class result, whilst others 
 
THE BOOK OF THE LANTERN. 
 
 137 
 
 seem reluctant to give anything but a very poor trans- 
 parency. A really good negative will give a good print 
 on paper, glass, or indeed on any other possible material, 
 but at the same time a negative, which from its thinness 
 would require special management in ordinary printing on 
 albumenised paper, will yield a fine transparency on glass 
 with half the trouble. In other words, a negative taken 
 purposely for lantern work need not be so dense as one 
 destined for the ordinary printing-frame. The precautions 
 used in dealing with a thin negative in the one case, must 
 be observed in the other ; for instance, the careful printer, 
 in producing a paper print from such a negative, will take 
 his frame far from the window of his room, and give it a 
 very protracted exposure, and, by coaxing it in this way, a 
 good dense print is obtainable. Exactly the same treat- 
 ment is necessary in producing a lantern-slide from the 
 same picture. Instead of holding the printing-frame a foot 
 or two from the gas-burner, as already recommended, let it 
 be removed 6 feet away from the flame, and be given a 
 greatly-increased exposure by the rule already indicated. 
 
 I have advised that the focussing-screen of the camera 
 should be marked with a 3-inch circle, to which the 
 picture should be limited. A still more effective plan, 
 however, is to cover the ground-glass with a card- 
 board mask, having a 3 -inch hole in its centre, which 
 can be placed in situ when required. The operator can 
 then see at a glance whether his pictare is nicely composed, 
 and will have a very good idea of its ultimate appearance 
 as a lantern-slide on the sheet. Most photographers carry 
 into the field with them more than one lens, and it is espe- 
 
138 
 
 THE BOOK OF THE LANTERN. 
 
 cially necessary that lie whose negatives are intended to 
 yield lantern-pictures of a uniform size should do so. The 
 beginner is, perhaps, not likely to see the advantage of this. 
 Let me point it out. Suppose that he has focussed the 
 image of some wayside cottage, and finds to his chagrin 
 that the building fills up all the proscribed circle, and that 
 the surrounding foliage and other accessories which really 
 make up the beauty of the scene, as presented to the eye, 
 are "far, far away." His natural impulse would be to 
 carry his camera farther from the object, but a blank wall 
 behind him forbids him to do this. But with a shorter 
 focus -lens, which should screw into the flange fitted on his 
 camera, the accident can be immediately remedied, and 
 he can proceed on his way rejoicing. This same difficulty 
 has occurred to me time after time, in the case of 
 country churches having small burial-grounds shut in on 
 every side by foliage. From no point can a view of the 
 building be focussed on the glass except by using a lens of 
 very short focus. Very often the conditions are reversed, 
 and the photographer finds himself before a scene with some 
 obstacle in front of him which forbids nearer approach, 
 and the image on the focussing- screen is quite insignificant. 
 Here the obvious course is to screw off the front lens of his 
 combination, and to treat the back one as a long-focus 
 single lens. Of course, the camera must be extended to 
 double its normal length, and no amateur should possess a 
 camera that will not do so, should occasion require it. 
 
 The most experienced workers often obtain a negative 
 full of brilliancy and delicate detail, but with a very thin 
 sky, — a sky so thin that if a lantern-slide were taken from 
 it raw, so to speak, we should have in it a very good repre- 
 
THE BOOK OF THE LANTERN. 
 
 139 
 
 sentation of a November fog. There are several ways of 
 obviating this difficulty. In exposing it before the gas- 
 flame it should, like all thin negatives, be taken several 
 feet distant, so that the time of exposure may perhaps 
 extend to twenty seconds or more. During this time keep 
 the sky portion covered with a piece of card which has 
 been cut in Vandykes all along the edge next the horizon, 
 but do not keep it still, but in gentle movement. This 
 plan gives a clear sky, with the effect of a slight haze over 
 the horizon, — an effect, I need hardly say, frequently seen 
 in nature. Indeed, this hazy effect can often be extended 
 to the landscape itself, with the most charming effect of 
 atmosphere which an artist could desire. 
 
 Another plan of treating a thin sky is to furnish it with 
 clouds by the following simple method : — Paste over the 
 glass side of the negative a piece of white tissue paper. 
 When this is dry, hold it up to the light, and mark upon it 
 the position of the horizon and the outline of any trees or 
 other objects which may appear against the sky. Now, 
 with a stump and a black pigment (such a pigment for use 
 with the stump is sold by most artists' colourmen, — I do 
 not know the name) rub in masses of cloud, taking care 
 that their edges are ill-defined and fleecy. By this means 
 a flat, tame -looking negative can be made to yield a beau- 
 tiful picture. Any water in the composition can be treated 
 in the same way, for it must be remembered that water 
 reflects clouds as well as anything else. Where the sky is 
 dense enough, but contains pin-holes or other blemishes, 
 Bates's black varnish, painted on the plain glass side, is the 
 best remedy ; or the faults can be delicately stopped out 
 by ordinary India ink on the film side. Where there is a 
 
140 
 
 THE BOOK OF THE LANTERN. 
 
 large expanse of sky, the quickest method is to gum over 
 it a piece of orange-coloured paper with a jagged edge. 
 
 A lantern slide, otherwise perfect, will sometimes re- 
 quire a little strengthening. I believe that the best 
 method of intensification is that long ago published by 
 Mr. England. Here it is : — 
 
 Mercuric bi-chloride (corrosive sublimate) ... \ oz. 
 Sal ammoniac ... .... ... ... ... \ „ 
 
 Water 12 „ 
 
 (Dissolve, and mark " Poison.") 
 
 The picture, after well soaking in plain water, is im- 
 mersed in this mixture, in which it will first turn grey, 
 and afterwards quite white if left long enough. The 
 white stage should not be reached unless a very great 
 additional intensity is requisite. Remove from the solu- 
 tion, wash most thoroughly under a tap for three or four 
 minutes, and immerse in the following solution, which will 
 almost immediately turn the film to a brown black : — 
 
 Liq. ammonia-fort ... ... ... ... \ drachm. 
 
 Water ... ... ... ... ... ... 6 ounces. 
 
 Rinse under the tap, and the operation is complete. Many 
 people object to the use of the mercuric salt, on the 
 ground that it is unstable, and that the picture will ulti- 
 mately fade. I have not found this to be the case if the 
 washing operation be thoroughly carried out, but as a rule 
 I should give an intensified film a protecting layer of 
 varnish. Prevention is better than cure, and the amateur 
 should endeavour to produce pictures that will require no 
 doctoring. 
 
 When the lantern transparency is complete it must be 
 mounted before it can be considered out of hand. It is as 
 
THE BOOK OF THE LANTERN. 
 
 141 
 
 well to try it in the lantern first, in order that any little 
 blemish not before detected can be remedied. Any little 
 clear spot where a clear spot has no business to be can be 
 touched with India ink. If the picture is to be coloured, 
 the slide need not be so firmly bound up as one to be used 
 plain. A cover glass, separated from the photograph by a 
 paper mask, with a round, square, or cushion-shaped open- 
 ing, and fastened with one or two slips of gummed (stamp) 
 paper, is quite sufficient until the artist is ready with his 
 palette and brushes. But if the slide is to be exhibited as 
 a plain photograph, it may as well be bound together as it 
 is to remain. For this purpose we require slips of gummed 
 paper fourteen inches long by three-eighths of an inch 
 broad. The paper (black needle paper is the best) should 
 be gummed before being cut, and one sheet will provide 
 for about a hundred pictures. Mix powdered gum arabic 
 with one fourth its weight of loaf sugar, and add sufficient 
 water to make a thick mucilage. Paint the paper liberally 
 with this, and hang it up to dry. When dry it can be cut 
 into slips of the above size. 
 
 To mount a picture, damp one of the slips of gummed 
 paper, and put it sticky side upwards on the table before 
 you. Now take a slide, duly fitted with its black mask, and 
 a cover glass, all perfectly clean and free from dust. Hold 
 the combination tightly between the fingers, and bring one 
 edge down on the end of the gummed slip. Now treat the 
 slide as a porter treats a heavy box, — turn it over and over 
 along the slip of gummed paper, so that each edge will 
 take up its quantum. Now carefully fold down the edges, 
 neatly adjust the corners, and the thing is done. 
 
142 
 
 THE BOOK OF THE LANTEE.N. 
 
 The black masks can be bought ready cut at about three- 
 pence the dozen, or the worker can cut his own if he prefer 
 it. Zinc patterns are sold for this purpose, together with a 
 clever cutting tool, which consists of a little steel wheel set 
 in a handle (see fig. 43). The pattern is placed above the 
 
 Fig. 43. 
 
 paper to be cut, the little wheel is run round the opening 
 in the zinc, and a cleanly cut mask is the result. A sheet 
 of glass is the best bed upon which to lay the paper when 
 cutting it. The gummed slips can also be bought, but 
 those who prefer to be self-dependent will make their own 
 in the way described. 
 
 Not long ago I compared one of my slides with a wet 
 plate — one taken from the same negative — by a first-rate 
 operator, who is used to this class of work, and hardly 
 does anything else. He was bound to admit that the 
 gelatine picture was the better of the two, and said that he 
 should think of relinquishing his bath after seeing what 
 gelatine plates could do. I advised him to do no such 
 thing. A wet plate is so certain in its results, that an 
 unskilled hand, if he be furnished with the materials, can 
 produce picture after picture without difficulty. I cannot 
 say the same of gelatine plates, for they are such ticklish 
 things that oftentimes something or other will go wrong. 
 
THE BOOK OF THE LANTERN. 
 
 143 
 
 But for the amateur worker, to whom a few failures are 
 not of any great moment, gelatine plates are best adapted. 
 The silver bath, with its concomitant stained fingers and 
 spoiled linen, is, I think, best left alone, unless the ama- 
 teur adopts it as a necessary part of his photographic 
 education. 
 
 Those amateur photographers who are used to the work- 
 ing of bromide paper, can produce lantern slides by an 
 easier method than any of those just reviewed, namely, by 
 means of the transferro-type paper which has lately been 
 introduced by the Eastman Company, and with which 
 many succeed in producing very fine lantern slides. This 
 paper is coated with identically the same emulsion as that 
 employed in the well-known bromide paper, and therefore 
 the amateur has an advantage at the outset, of working 
 with a medium to which he is accustomed ; its develop- 
 ment being the same as that of the ordinary bromide paper. 
 It consists of an insoluble sensitised emulsion which is 
 applied to paper having a soluble substratum of gelatine. 
 The tissue is exposed under a negative to gaslight for 
 the requisite time, and according to the density and 
 other peculiarities of the negative in question ; and is then 
 developed in a ferrous-oxalate solution in the ordinary 
 manner. It is then transferred to a piece of plain glass, 
 which should be free from bubbles and other blemishes, 
 while wet, being placed face down on the glass, and 
 squeezed into contact. As much moisture as possible is 
 then removed by the application of blotting paper. In 
 about half an hour it will be ready for stripping ; but may 
 
144 
 
 THE BOOK OF THE LANTERN. 
 
 be left if preferred until the tissue is quite dry. The glass 
 and its print is placed in a dish containing water at 
 the temperature of about 110 degrees if the print is wet; 
 but should the print have been allowed to dry, the water 
 must be some 1 0 degrees hotter. After allowing it to soak 
 for a couple of minutes or so, the paper is raised at one 
 corner, taking every precaution not to injure the sur- 
 face ; when it will readily separate from the film. The 
 plate bearing the picture is then put into a solution of alum 
 for a minute, and is placed in a rack to dry. Upon ex- 
 amining a lantern slide so made, a slight granular appear- 
 ance is observable in the high lights and the sky ; but this 
 is not apparent when the image is projected on the lantern 
 screen. The picture will have the usual grey tone, which 
 is associated with ferrous-oxak te development ; but it can 
 be turned to a rich brown by the following treatment : — 
 
 , ( Potassium ferricyanide ... ... ... 100 grs. 
 
 ( Water 24 ozs. 
 
 -o ("Uranium nitrate ... 100 grs. 
 
 15 (Water ! 24 ozs. 
 
 Take equal parts of A and B and immerse the print in 
 the mixture until the tone changes to the tint required. 
 Then wash thoroughly and immerse for five minutes in a 
 freshly made-up solution — hypo, three ounces ; water, six- 
 teen ounces, wash. The prints that will best yield to this 
 after-treatment are those in which the image is from any 
 cause rather weak ; for this final bath not only alters the 
 tone, but acts as an intensifier. 
 
CHAPTER XI. 
 
 ON COLOURING PHOTOGRAPHIC TRANSPARENCIES FOR LANTERN 
 
 SLIDES. 
 
 N giving directions for colouring lantern trans- 
 parencies, I am quite aware that many persons 
 will say at the outset that a good photograph is 
 better without any colour at all ; on the principle, I suppose, 
 that " good wine needs no bush." 
 
 I quite agree with that opinion, and in colouring a trans- 
 parency of good quality, I should be inclined to describe 
 the operation more as tinting ; for the common method of 
 colouring by which photographs are blotted out and 
 drowned in a mass of pigment is simply atrocious. I 
 lately saw a photographic transparency for a lantern, which 
 was very beautifully and tastefully tinted, evidently by an 
 artistic hand. 
 
 The owner of this picture saw no beauty in it, but com- 
 plained to me that he paid a long price for this thing, and 
 there was hardly any colour on it, just as if payment ought 
 to go by the amount of pigment stuck on the glass. 
 
146 
 
 THE BOOK OF THE LANTERN. 
 
 In the first place, the worker must consider which of 
 his pictures will be benefited by a coating of colour, 
 for some subjects are very much better le£t alone, 
 and shown as untouched photographs. This is especially 
 true of such pictures as exhibit a mass of detail entirely 
 covering the glass ; a woodland scene, for instance, with 
 tangled masses of branches and underwood, and ferns in 
 profusion. On the other hand, if the subject be an open 
 landscape, with more than half of it consisting of white 
 sky, it is undoubtedly improved by being tinted. The 
 white sky receives, with great benefit, its n&fcural tint of 
 blue, relieved by masses or feathery tufts of clouds, 
 which, if carefully introduced, can be made to look very 
 like the real thing. 
 
 In the directions that I am now about to give, it may 
 therefore be taken for granted that all colour is to be put 
 on most sparingly, and that its amount must not be suffi- 
 cient to obliterate the least detail in the photograph. Of 
 course, if a bad photograph is to be coloured instead of 
 being thrown into the dust-hole, — which latter is by far the 
 better course, — colour can be piled on to it to hide its 
 inherent defects, but this is only justifiable when the colour- 
 ing is a necessity, and there is no time to procure a better 
 photograph. 
 
 Let it be understood that this work of colouring lantern 
 transparencies is not easy. It not only requires a steady 
 hand and good eyesight, but it wants artistic perception 
 aiso, — at least, to do it well. I do not say that a knowledge 
 of drawing and painting is absolutely necessary to the slide- 
 painter ; but it is certain that he who understands the use 
 
THE BOOK OP THE LANTERN. 
 
 147 
 
 of any kind of colours, and has some knowledge of the way 
 in which they can be combined to form different tints, will 
 paint a slide very much better than one who is without 
 that knowledge. Should he be quite unused to working in 
 colour, he had best begin by procuring some book upon the 
 general theory of colouring, so that he may understand the 
 difference between a primary, secondary, and tertiary tint, 
 and may learn how to combine them together. There are 
 plenty of such books to be had, and very often the infor- 
 mation is comprised in some of those useful little manuals 
 on water-colour painting which can be had of most artists' 
 colour men. I say water-colour painting advisedly, for the 
 art of slide -painting partakes more of that kind of art than 
 any other ; for the reason that it deals with transparent pig- 
 ments. But do not let it be imagined that I recommend 
 water colours for the work in hand. I know that some 
 writers have advised their use, and there is more than one 
 manual which describes how slides can be painted in water 
 colours. The process may possibly have answered under 
 the old conditions, when the majority of lantern slides were 
 made by the wet process, and when the artist had a layer of 
 collodion to paint upon. But most of my readers will wish 
 to colour their own productions ; and as these will probably 
 consist of gelatine pictures, which any application of water 
 will blister, I will at once reject that method of painting as 
 being inadmissible. 
 
 First, I will make a few remarks with regard to the 
 apparatus required, which is of the simplest description. 
 A retouching desk will make a good easel (see fig. 44), or, 
 failing this, one can readily be made by using a sheet of glass 
 
 L 2 
 
148 
 
 THE BOOK OF THE LANTERN. 
 
 in#a frame. A small school slate measuring about 8 by 5, 
 with the slate knocked out, and a piece of window-glass put in 
 
 Fig 44. 
 
 its place, makes a very good easel for slide-painting. This 
 should be hinged on to a base board with a strut at one 
 side, so as to keep it at a convenient slope for working. A 
 sheet of white paper placed on the base board at the back 
 completes the arrangement. 
 
 Beyond the easel we shall require a palette, and a white 
 tile answers the purpose as well as anything else ; some 
 brushes, a few colours, a sheet or two of white tissue paper, 
 and a piece of linen cloth upon which to wipe the brushes. 
 One or two bottles containing different media will complete 
 the list. The colours employed are those used by artists 
 for oil painting, and which are enclosed in collapsible metal 
 tubes. But, unlike the oil painter, the lantern-slide artist 
 is confined to the use of those colours only which are 
 naturally transparent. To make this clear, let us suppose 
 
THE BOOK OF THE LANTERN. 
 
 14!) 
 
 that any one ignorant of the subject were to attempt 
 to use snch a colour as vermilion, which is opaque ; it 
 would appear to be of the usual vivid scarlet when seen on 
 the glass, but seen through the glass, it would simply be a 
 black patch, because the light cannot filter through it. 
 This being the case with all the opaque colours, we there- 
 fore discard them. I now annex a list of colours which are 
 at the disposal of the slide -painter, and which are all more or 
 less transparent. They are not all actually essential, but 
 still the artist will do well to procure them, as they will 
 give him an immense variety of tints : — 
 
 Prussian Blue Brown Madder 
 
 Indigo Rose Madder 
 
 Italian Pink Purple Madder 
 
 Raw Sienna Crimson Lake 
 
 Yellow Lake Ivory Black 
 
 Chinese Orange Burnt Sienna 
 
 Neutral Tint McGilp. 
 Brown Pink 
 
 It will be noticed that there is only one brilliant blue in 
 this list, that is Prussian blue. For landscape work this 
 blue is used, perhaps, more than any other colour ; for skies 
 always, and it enters into the composition of the various 
 greens, and forms useful tints with most of the other pig- 
 ments. It is not the colour which an artist would choose by 
 preference with which to depict the tender tints of the sky, 
 for, truth to tell, it has a greenish hue, and is rather cold 
 and repellent in character ; but it is really the only blue 
 which can be laid on the glass in a flat, even tint, and 
 
150 
 
 THE BOOK OF THE LANTERN. 
 
 therefore we must make the best of it, such as it is. We 
 have a far larger choice in yellows, for no less than four of 
 the colours quoted are, in spite of their names, yellow in 
 tint. These are Italian pink, the most useful of all ; 
 Raw sienna, not nearly so pure a colour; Yellow lake, 
 rather a difficult colour to work with ; and Chinese 
 orange, a most valuable and rich tint. Brown pink may 
 also be described as a yellow, and brown madder has also a 
 great deal of the same colour in its composition. The reds 
 represent a great difficulty to the slide-painted, for, although 
 they appear to be very rich when spread on canvas, they are 
 very weak colours when we come to look through them in 
 a transparency. It is next to impossible to produce a real 
 scarlet as a transparent colour, but the nearest approach to 
 it can be made by using Chinese orange mixed with crimson 
 lake. A great variety of browns may be obtained by com- 
 bining burnt sienna with the other colours, and the ivory 
 black will be found most useful in this service. The best 
 brushes for general work are those of camel-hair, which 
 have the further advantage of being cheap. But a few 
 sables will be wanted for delicate markings. 
 
 A thing of first importance is the selection of a suitable 
 medium with which to mix the tints. Canada balsam in 
 turpentine is of great value. Another good one, which I 
 believe many slide -painters use almost exclusively, is made 
 by diluting copal varnish with turpentine, while for dark 
 colours, japanners' gold size, diluted in the same way, is an 
 excellent medium, and is of special use in the foreground, 
 The colour should be mixed up on the palette with the 
 medium selected with a proper palette-knife, so as to form 
 
THE BOOK OF THE LANTERN. 
 
 151 
 
 what is in reality a coloured varnish ; and this must be 
 quickly applied to the picture before it has time to thicken 
 by evaporation of the solvents. 
 
 For greens, to be used mostly in foliage and for grass, 
 yellow and blue must be mixed together in varying pro- 
 portions. There is no such thing as a satisfactory trans- 
 parent green which can be bought ready made, and suit- 
 able for the purposes of the slide-painter ; but the use of 
 the two colours named, if we take care to vary the pro- 
 portion of each, can be made to give a great variety of 
 tints. But it should be pointed out that, if used alone, this 
 compounded green will be far too raw, and will exhibit a tint 
 which is never seen in nature. 
 
 We mix, therefore, with the yellow and blue, some red 
 or brown, to take off: this rawness. An endless variety of 
 tints may be made by taking three colours only, and using 
 them in different proportions, and I would advise the slide- 
 painter to mix some of these tints, and put them side by 
 side on a bit of glass, with a ticket attached to each 
 describing their constituents. This specimen glass will be 
 useful for future reference. I give in the next chapter a 
 few compound tints, which can be made easily, and can be 
 used for foliage, etc. 
 
 The list of colours given will be found more than 
 sufficient for all needs, and many slide-painters do very 
 good work with only half their number, for there is no 
 limit to the number of tints which one may get by 
 judicious blending. Mathematicians are able to tell us 
 the number of chances against a whist-player turning 
 up the same cards on two different occasions, and we 
 
152 
 
 THE BOOK OF THE LANTERN. 
 
 know very well that the odds against such an occurrence 
 amount to an enormous figure, but no mathematician 
 would be able to calculate the number of different tints 
 that we can procure, even from the three primary colours. 
 We have such tints in the beautiful solar spectrum, 
 but there they blend into one another so gradually that 
 no eye can count them. 
 
 One of the great helps to success is to observe the rule of 
 being very sparing of both colour and medium when dab- 
 bing in the sky portion of the picture ; but the painter can 
 be more lavish with both when he is dealing with foliage, 
 and any broad masses of light or shade. Here he can 
 often use a large camel-hair brush, and can mop in the 
 colour, only taking care that he does not go over the out- 
 line which circumscribes the particular portion of the 
 picture he is working upon. In the case of a mass of foliage, 
 let him mix up the desired paint on the palette with a 
 flexible palette knife, which he should always have at hand. 
 This should be done thoroughly and quickly ; then let him 
 take up a moderate quantity of this colour in the brush and 
 mop it on to the surface of the picture. For this class of 
 work mastic varnish, very much thinned with turpentine, 
 forms a capital vehicle. The strength of this mixture may 
 be one part of mastic to six of turpentine. This medium 
 keeps liquid long enough for careful manipulation, and yet 
 it dries quickly in comparison with other media which 
 might be named. 
 
 Photographic transparencies are now produced of such 
 varied tones that in many cases it will be found advisable 
 to leave portions of the picture quite uncoloured. With 
 
THE BOOK OF THE LANTERN. 
 
 153 
 
 chloride plates especially a very wide range of tones can be 
 obtained, and practically the experienced worker can pro- 
 duce a picture in any colour, — from black, ranging through 
 different changes of brown, to red ; and even a blue picture 
 can be produced on that type of plate. Tt is often prac- 
 ticable to suit the tint to the class of subject. A woodland 
 scene may be toned a rich brown, for example ; and this 
 tone, which the picture possesses at the outset, will prove 
 of great help to the colourist. Many water-colour painters 
 commence their work by giving the surface upon which 
 they work a yellow-brown tint, and, when that is dry, they 
 commence the picture proper. It will be readily seen that, 
 with a photographic picture toned in the way described, the 
 slide-colourist will work under much the same conditions. 
 The object in both cases is to give a general warm tone to 
 the picture, which cannot be blotted out even by the most 
 careless and ignorant worker. 
 
 It is a good practice to examine the slide in the lantern 
 as the various stages of the painting progress, taking care 
 to protect it from dust. For this reason it should, before 
 being placed on the lantern-stage, be furnished with a 
 paper mask and a cover-glass ; it may then be slipped in 
 a mahogany frame kept for the purpose. By this exami- 
 nation under the light by which it is ultimately to be 
 shown can we alone judge of its defects. It is now that 
 the dust, previously invisible, becomes painfully evident. 
 The beginner will, indeed, be forced to acknowledge that 
 this is an example of matter in a very wrong place. He 
 sees up in the sky of his landscape, which he just now 
 thought would look so very beautiful, what is apparently a 
 
154 
 
 THE BOOK OF THE LANTERN. 
 
 broomstick ; but careful examination shows that it is only 
 a little piece of hair about a quarter of an inch in length, 
 which is magnified into the size of the useful domestic 
 appliance just mentioned, and, what is more, these little 
 bits of hair are very difficult to remove. We may per- 
 haps, lift them with our etching-needle from the paint in 
 which they are embedded, but in doing so we are pretty 
 sure to leave scratches behind which are almost as bad as 
 the hairs. Bits of dust are everywhere, and the only way 
 in which their intrusion upon our work can be avoided is 
 to devote a room to this express purpose of slide-painting. 
 It should be uncarpeted and uncurtained, and should be 
 swept with tea-leaves, or better still, with damp saw-dust, a 
 few hours before any painting is attempted. Its table and 
 only chair should be wiped down with a damp duster, and 
 the same treatment should be applied to the window ledge, 
 or any projecting parts of the wood- work which may be 
 near the painter as he sits at his work. The artist should 
 put on a linen blouse, which is rigidly kept for this work. 
 All these precautions may seem unnecessary, but we must 
 observe them if we want to produce the best possible work. 
 I have seen slides, otherwise well executed, which were 
 quite spoiled by dust, and it is one of the aggravations of 
 the slide-painter's life, that dust always gets into the sky, 
 where, of course, it is more evident than in any other por- 
 tion of the picture. 
 
 Let the table upon which the operator works be placed 
 near a window, preferably under a north light. This 
 table should be wiped over with a damp duster imme- 
 diately before the work is commenced, and it should be 
 
THE BOOK OF THE LANTERN. 
 
 155 
 
 covered with a sheet of newspaper, also wiped with the wet 
 cloth. The easel is put in the front centre of the table ; 
 on its left-hand side may be placed the colours, while on 
 the right the palette must be within easy reach, together 
 with a sheet of tissue-paper folded in four, so as to make a 
 kind of pad upon which to wipe the brushes. The medium 
 employed varies with the particular colour which happens 
 to be in use, but turpentine forms the basis of all. A 
 little cup of turpentine should stand close to the palette, in 
 which the brushes can be washed, previously to being 
 partially dried by being stroked gently on the pad of 
 tissue-paper before mentioned. 
 
 Supposing that the picture upon which the operator tries 
 his 'prentice hand is a landscape, the sky will be the portion 
 of the slide which will first require his attention. Squeeze 
 out from the Prussian blue tube a little bit of colour about 
 the size of a grain of wheat, for this tint is so powerful 
 that a little of it will go a long way. Near it place a little 
 McGilp. Now dip one of the brushes in the turpentine, 
 mix it on the palette with the McGilp, and with sufficient 
 colour to give the strength of tint desired. Now paint 
 over the sky portion of the picture with bold, even strokes, 
 from side to side. The brush will leave plenty of markings, 
 ugly ridges from right to left ; but let these pass for the 
 present, for we shall remove them in the next stage of 
 the process. The picture should remain as it is for a 
 minute or two, so as to give time for the turpentine to 
 partially evaporate, when we must proceed to the 
 operation of dabbing. Dabbers are made of different 
 materials : sometimes it is recommended to use a piece of 
 
156 
 
 THE BOOK OF THE LANTERN. 
 
 fine wash-leather, formed into a little ball by cotton wool 
 inside, tied np like a small pad. I have not found such a 
 dabber to be satisfactory in practice ; for the leather, how- 
 ever fine, leaves feathery marks upon the colour, which, 
 although they are not readily seen on the slide, become 
 painfully evident when the picture is magnified on the 
 screen. I myself tried, a short time ago, to make some 
 special dabbers for this work, which were composed of 
 gelatine and glycerine moulded in a small cup like an egg- 
 cup. These dabbers, also, were not as satisfactory as 1 
 could have wished, although I found that they were better 
 than those of wash-leather. The best dabber which it is 
 possible to get is the finger. This needs a certain amount 
 of preparation. The flesh of the finger is covered with a 
 number of little ridges, which we well know make what 
 we call finger-marks on anything touched. These ridges 
 can be obliterated by rubbing the finger with pumice-stone 
 and water, or by using the pumice-stone soap, which is 
 sold for the express benefit of much-soiled hands. A 
 quicker plan is to rub the finger a few times on very fine 
 glass-paper, when the ridges quickly disappear. It is 
 obvious that the operation of rubbing down must only be 
 carried to a slight extent, or else soreness will result. The 
 finger makes a far more perfect pad than any artificial con- 
 trivance because of its exquisite sensibility ; for in using it 
 we both see and feel the progress of the work. 
 
 Commencing at the left-hand top corner, we dab with 
 the finger rapidly from side to side of the picture ; at first 
 it will make ugly marks, but the turpentine gradu- 
 ally evaporates as the work proceeds, and these marks 
 
THE BOOK OF THE LANTERN. 
 
 157 
 
 blend into one another, until they finally disappear, and we 
 have before ns a flat, even tint of colour. The knack of 
 laying in a sky cannot be gained without a great deal of 
 practice ; but the operator may feel assured that when he 
 has once conquered this initial difficulty half his labour 
 is over. 
 
 If we merely want a plain blue sky, — and where the 
 amount of sky is small it is often expedient that this should 
 be the case, — we can consider this portion of our picture 
 finished with the dabbing ; but if we want to indicate 
 clouds, this must be done before the colour has commenced 
 to dry. Here comes in the work of the artist. From what 
 I have seen exhibited in the shop windows, I conclude that 
 many slide-painters classify clouds under two general 
 heads, namely, large masses called "feather-bed clouds," 
 and small ones, called " bolster clouds." These are created 
 by means of a leather stump, moved with a semicircular 
 motion, by which clouds of either pattern can be wiped 
 out to order. The student of nature will, however, aim 
 at something higher than this ; for he will know that no 
 two clouds, of the thousands he has gazed upon, have ever 
 been alike. For convenience sake, meteorologists write of 
 cumulus, cirrus, stratus, and nimbus forms of clouds, but, 
 in reality, although each term describes a typical form of 
 vapour, they convey very little information to the mind's 
 eye. Each form so constantly blends with the other to delight 
 the eye, that no words can sufficiently describe the vast 
 variety of cloud beauties presented to us. In attempting 
 to imL^te some of these effects of nature in glass-painting, 
 I find that a piece of kid wrapped round a pointed stick 
 
158 
 
 THE BOOK OF THE LANTERN. 
 
 is far more serviceable than an ordinary leather stump 
 The rough side of the leather should be used as the rub 
 bing surface, and, by altering its position on the stick, 
 sometimes letting a soft ragged edge touch the paint where 
 a fleecy cloud is to be described, and sometimes using the 
 material tightly stretched over its support where bold 
 touches are necessary, a great number of different effects 
 can be secured. The sky being finished, it will be convenient 
 now to put in any other parts of the picture where blue 
 or purple is required. The distant hills can be covered 
 with the sky tint, mingled judiciously with a little crimson- 
 lake. Water, in which the sky is reflected, will, of course, 
 be painted in with the sky colour. Shadows generally will 
 also partake of the purple tint already mentioned. These 
 are all laid in with the brush, as before indicated, and, time 
 having been given for the partial evaporation of the turpen- 
 tine, they i must be gently dabbed with the finger. No care 
 need be taken about transgressing over other portions of 
 the picture where blue or purple has no business to be. 
 These can be wiped clean with leather or stump, after the 
 tints have been satisfactorily laid in. 
 
CHAPTER XII. 
 
 ON COLOURING PHOTOGRAPHIC TRANSPARENCIES FOR LANTERN 
 
 slides (continued). 
 
 GREAT many subjects can be advantageously # 
 treated as moonlight pictures, and very attractive 
 they are if well done. In this case, the blue 
 must be laid on of a much darker hue, and can have 
 blended with it a little ivory-black. Having decided 
 upon the best position for the " queen of night," that 
 place should be lightened by extra hard dabbing, and 
 any clouds that may be required can be wiped out at 
 the same time, taking care that their light edges are 
 nearest to the uncreated moon. The moon must not 
 be wiped out, but must be picked out, film and all, so 
 that nothing but bare glass is on the spot covered by it. 
 To accomplish this, wait until the paint is bone dry, and 
 attach to the place where the moon is to be a tiny piece of 
 gummed postage-stamp paper. This should not be bigger 
 than a small pea, and is merely for the temporary purpose 
 of holding the leg of a small pair of compasses. I keep a 
 special pair for this particular work, one leg being ground 
 
160 
 
 THE BOOK OF THE LANTERN. 
 
 so as to form a cutting edge. Having opened the compass 
 to the required distance, plant one point on the paper, and 
 gradually with the other cut through the gelatine film. 
 The circular disc so marked out can now be quickly picked 
 away, bit by bit, with the etching-needle. (This needle, 
 by the way, is merely an ordinary needle, bound to a pen- 
 holder by waxed thread.) The same instrument can be 
 used afterwards for picking out effective lights in the fore- 
 ground ; but the great fear is that the beginner should 
 abuse the power thus put into his hands. The touches 
 should be of the most minute description, and the operator 
 should constantly remember that his work, with all its 
 faults, has to be magnified to a very great extent. 
 
 I need hardly point out that a most effective change can 
 be made by showing a landscape, first coloured as a day- 
 light picture, and then dissolving it into the same view by 
 moonlight. This change requires a double dissolving-view 
 lantern, the daylight picture being placed in one lantern, 
 while the moonlight picture is placed in the other, care 
 being taken that both pictures register; that is to say, 
 occupy exactly the same position on the sheet upon which 
 the images are projected. 
 
 But let the beginner not attempt sunsets of the gorgeous 
 order, after the manner of G. M. W. Turner (deceased), 
 until great practice has taught him the different character- 
 istics of his colours. I do not here allude to their tone 
 character, but to the different ways they behave, mechani- 
 cally, when applied to the slippery surface of the picture, 
 and the different media required to coax them into lying 
 flat. He may think that, because he knows how to produce 
 
THE BOOK OF THE LANTERN. 
 
 161 
 
 a good even sky-blue tint, he has only to try the same pro- 
 cedure with his yellows and reds to produce all kinds of 
 brilliant, ethereal, striped-petticoat effects. But, on trying 
 these colours, he will soon find out his mistake, and will 
 also find that he must add varnish to them before he can 
 work with them at all. Moreover, they seem to be espe- 
 cially prone to attract any little unconsidered trifles in the 
 way of dust which may be seeking rest.. 
 
 1 was so impressed with these difficulties with regard to 
 sunset skies, when first I began glass painting, that 1 sought 
 for another means altogether for gaining what I wished. 
 I was attracted by the brilliant hues of the aniline, or coal- 
 tar colours, and at once endeavoured to enlist them into my 
 service. As others may be tempted to work in the same 
 groove, I may at once state why, after patient trial, I dis- 
 carded them. Most of these colours can be readily dissolved 
 in alcohol, and, therefore, it is not difficult to make 
 coloured varnishes with them. But when I tried to paint 
 my gelatine picture with the splendid tints, I found it next 
 to impossible to confine them within the boundaries of any 
 outlines whatever. They would flow over the edges on 
 their own account, do what I might. The fact is that these 
 aniline colours have a kind of greedy affinity for gelatine, 
 and there seem to be no means of controlling their advance 
 when once they come into contact with it. By flooding 
 an entire picture with a yellow or red varnish, I was able 
 to gain (sometimes) some wonderful effects. But the action 
 of the dye upon the gelatine was of too uncertain a nature 
 to tempt me to adopt that method of working as a perma- 
 nent resource. Lastly, aniline colours are fugitive, 
 
 M 
 
162 
 
 THE BOOK OF THE LANTERN. 
 
 Hitherto I have regarded the picture as possessing a 
 plain glass surface to represent the sky, and this will be 
 found to be the case with most photographic slides. But 
 we all know that a plain white sky in a photograph is, from 
 an artistic point of view, an abomination. By the simple 
 process of colouring we get over the difficulty ; still, if we 
 can produce upon a photographic transparency natural 
 clouds either existing in the original negative by the virtue 
 of a properly-constructed shutter, which will only give a 
 fraction of the normal exposure to the sky, or by a system 
 of printing-in from a separate negative in a way that need 
 not be described here, it will be a great artistic gain. In 
 colouring such a sky the painter has a great advantage, for 
 irregularities in laying on the colour, which would other- 
 wise be distinctly visible, are hidden by the details of the 
 clouds in the picture. 
 
 In colouring such a sky we may commence, as usual, by 
 dabbing on the blue in the spaces which represent rifts 
 between the clouds, and we can then add tender tints made 
 up by mingling such colours as crimson lake, and the 
 various yellows at our disposal, and we can also add to the 
 richness of the general effect by putting in different tones 
 of lavender, mauve, and purple, made up with crimson lake, 
 the madders, and blue. These colours, after the blue has 
 been dabbed on, can best be painted in with the brush, 
 using as a medium Canada balsam in turpentine. This is 
 a good, quick-drying medium, and it has the advantage of 
 being so pale in colour that it will not effect the most deli- 
 cate tints. 
 
 Before proceeding farther with the work, the picture 
 
THE BOOK OF THE LAMERN. 
 
 163 
 
 should be dried by heat, — and there are many means of 
 doing this. An oven, not too hot, w ill do what is neces- 
 sary, but it is uncertain, for the heat may rise to such a 
 pitch that picture, gelatine, and all will curl off the glass. 
 A tin biscuit canister, divided into grooves, and placed 
 (dutch oven fashion) in front of a good clear fire is better ; 
 but the best plan that I have tried is the following : place 
 the glasses to be dried upon a flat iron plate above a gas 
 stove, the heat of which can be regulated. Upon the top 
 of the plate put a frame of wood, covered with fine muslin, 
 to keep off the dust. About twenty minutes of such treat- 
 ment will make the layer of paint on the glass so hard 
 that it can be worked upon with other colours, or sub- 
 mitted to the moonlight operation as already described. It 
 is during the operation of laying in the sky, &c, which may 
 be comprehended under the term " first painting," and the 
 subsequent drying, that access of dust must be carefully 
 guarded against. 
 
 Lantern slides, by whatever photographic process they 
 may have been produced, will stand a great deal of heat, 
 and they can be made hotter than the hand can con 
 yeniently bear with impunity. This heat may be con- 
 tinued for about half an hour, and it will be found that 
 it has a kind of japanning effect upon the oil colours 
 employed; indeed, the colours are by this means made so 
 hard that it is difficult, if not impossible, to remove them 
 afterwards without at the same time destroying the photo- 
 graphic image beneath the pigment. 
 
 After the sky has been dried in the manner described, it 
 can easily be deepened, if found necessary, by the applica- 
 
 x 2 
 
164 
 
 THE BOOK OF THE LANTERN. 
 
 tion of a little more paint, which need not be applied with 
 a brash, but can be simply dabbed on with the finger. 
 Some very good effects are often possible by this second 
 painting, especially when the sky is deepened, in the 
 manner described, at its upper part or zenith ; such a 
 deepening, it will be readily seen, being in strict accordance 
 with the sky of nature. 
 
 A blue sky with white clouds formed by the simple 
 operation of wiping out the colour, and leaving the clear 
 gelatine, is by far the easiest kind of sky to produce. It can 
 be modified in various ways by working other colours upon 
 it near the horizon, — such as red or black, most sparingly 
 bestowed, or the zenith tint can be strengthened after the 
 slide has been dried. A most effective sky is that which I 
 may call the ordinary summer twilight sky, — that is to say, 
 the deep blue at the zenith, fading gradually to a lighter tint 
 until it merges into bright yellow or orange at the horizon. 
 Such a sky is not difficult to produce. The best way will 
 be to commence at the horizon by dabbing, without the 
 use of the brush, Italian pink on to the glass ; a very little 
 colour being applied to the finger, with the addition of the 
 merest trace of medium, such as Canada balsam, in turpen- 
 tine. This must be diligently dabbed upon the glass until 
 its stickiness almost disappears, and its upper margin is 
 left without any hard lines. Then the finger should be 
 washed in the cup of turpentine which the painter should 
 always have" at his elbow, and the blue may be applied to the 
 upper part of the picture in the ordinary way, and dabbed 
 down until it almost touches the yellow which has been 
 previously laid on. Once more wash and dry the dabbing 
 
THE BOOK OF THE LANTERN. 
 
 165 
 
 finger, and then use it, without any fresh application of 
 paint, to merge the two colours into one. In this way 
 it will be found, after a little practice, that a good junction 
 can be made, and that one colour will exhibit a regular 
 gradation into the other. If this work is well done, the 
 effect will be found to be a most pleasing one, and should 
 not be meddled with by the addition of clouds. 
 
 Our painting has now progressed to a certain stage. The 
 sky has been laid in, the clouds have been wiped out, and 
 the shadows have received a delicate purple tint. The 
 whole has been submitted to a baking operation, by which 
 the attached colours are made so hard and firm, that it 
 would be difficult to remove them without destroying at the 
 same time the gelatine film upon which they are superposed. 
 We now place this unfinished sketch again upon the glass 
 easel, and will endeavour to turn it into a finished picture. 
 It is at present what Mr. Whistler would call " an arrange- 
 ment in purple and blue." We will endeavour, by working 
 over these tints where required, and by adding others, to 
 produce a general harmony of effect, as nearly approaching 
 to nature as possible. 
 
 Any one possessing artistic feeling, — and no one without 
 that faculty will make a really good slide-painter, although he 
 may easily come up to a common standard, — will, on first 
 looking at the subject for colouring, make up his mind as 
 to the way in which he means to treat it. He will arrange 
 to have a cloud mass in one place, — possibly to relieve a 
 church steeple or other high building, — or a bright horizon 
 where, possibly, lights are to be seen through tangled 
 masses of foliage ; or in other ways he will have in his 
 
166 
 
 THE BOOK OF THE LANTERN. 
 
 mind a definite programme to follow ont, and will do his 
 best to achieve it, and will do so with more or less 
 success. But, through all, he must bear in mind that his 
 picture will eventually be highly magnified, and that the 
 k*ast blemish will be magnified too. In no art, perhaps, 
 cexq a man learn more by repeated failures (failures 
 which should be, from time to time, submitted to the 
 searching light of the lantern) than he can in this art 
 of slide -pain ting. 
 
 The worker must constantly remember that the effective- 
 ness of his picture is dependent far more upon contrast 
 than upon the tone of any particular tint. Without con- 
 trast his colours will be meaningless and poor, although, 
 individually they may present brilliant hues. The rule 
 governing contrast of painters' colours, — i.e., colours which 
 are complimentary to one another,— is most simple. Here 
 it is in a nutshell. The three primary colours are red, blue, 
 and yellow.* Any two of these mixed together form a 
 secondary colour which is complimentary to the remaining 
 'primary. For example : — Red and blue mingled form 
 purple. What better contrast to purple can there be than 
 yellow, — its complimentary, — being the primary which is 
 left out of the combination ? Again, blue and yellow form 
 green, and green is complimentary to red. Once more, 
 yellow and red form orange, the complimentary of blue. 
 I have no hesitation in saying that a man possessing this 
 little bit of elementary knowledge is far more likely to 
 
 * This is not correct for coloured light, but answers for painters* 
 pigments. 
 
THE BOOK OF THE LANTERN. 
 
 167 
 
 produce an effective picture with three colours than can 
 one ignorant of it, although he may have the run of all 
 the artists' colour-shops in the kingdom. He can never go 
 far wrong if he will, so far as the subject will allow, place 
 green against red, orange near blue, and yellow in conjunc- 
 tion with purple. A subject, such as an Oriental street- 
 scene or bazaar, where such combinations can be made 
 without stint, has a most gorgeous effect when projected 
 upon a screen. Each of these colours can at the same timt 
 be mingled to give an endless range of tints, — in fact, all 
 the colours of the rainbow. And now let me give a few 
 hints as to finishing colours and combinations useful for 
 special purposes, together with the best media with which 
 to mix them. In these finishing colours the dabber, except 
 in extreme cases, must be relinquished, and the brush 
 (camel hair and sable) alone employed. 
 
 Skies and Clouds. — Prussian blue (some prefer Chinese 
 blue), rose madder, purple madder, Italian pink. The blue 
 to be laid on as already described, using as a medium 
 McGilp and turpentine. In laying on after tints a small 
 quantity of copal varnish should be added. 
 
 Water always reflects the colours above it. If the water 
 be very still, the effect of surface may be given to it by 
 drawing gently across it a dry (mop) brush, such as gilders 
 use. In brooks and running streams, lights may be picked 
 out while the colour is wet, with a pointed stick, or when 
 dry with the etching-needle. In representing rough sea, 
 we must remember that such water not only reflects the 
 colour of the sky above it, but shows also its local colour. 
 It may first be painted over with the sky colour, and, after 
 
168 
 
 THE BOOK OF THE LANTERN. 
 
 baking and drying, this can be worked upon with various 
 shades of yellow, blue, brown madder, and indigo ; medium 
 Canada balsam varnish, McGilp, and turpentine. 
 
 Boats and Shipping. — Black, raw sienna, Vandyke 
 brown, burnt sienna, Chinese orange, indigo, — indeed, 
 nearly all the colours available. Medium, same as last. 
 
 Foliage. — For foliage we are limited for our greens to a 
 mixture of Prussian blue and the various yellows, namely, 
 Italian pink, raw sienna, and brown pink. But these will 
 give endless variety of tones, particularly when aided by 
 other colours. Here are a few examples : — 
 
 Bkr, Italian pink, and burnt sienna. 
 
 Italian pink, Vandyke brown, and indigo. 
 
 Italian pink and brown madder. 
 
 Brown madder, Italian pink, and indigo. 
 
 By adding Chinese orange to any of these, autumnal 
 effects are readily obtained. Media, Canada balsam var- 
 nish ) and for the darker colours, gold size. N.B. — These 
 various combinations should be made up on the palette, 
 as required, with the help of the palette knife. 
 
 Foreground. — It is here that the artist can employ all 
 the treasures of his palette. Let him remember that any 
 particular colour can be easily modified by glazing another 
 colour over it. This is done after the first colour is dry 
 by mixing a second tint, which may be applied above it. 
 The medium for this varnish will vary with the glazing 
 colour employed, Canada balsam will do for most, but 
 where reds are used, which are slow driers, the medium 
 should be gold size. 
 
 Let the painter ever remember that force of colour can- 
 
THE BOOK OF THE LANTERN. 
 
 169 
 
 not be obtained by piling on masses of pigment, which will 
 naturally serve to obscure the details of the photograph 
 upon which such pigment is placed ; but this force of 
 colour can be easily produced by judicious contrast of differ- 
 ent tints. As I have before observed, the student must 
 make himself master of the art of colouring, if possible, 
 before he commences its practice. Some years ago there 
 was published an excellent series of little books, costing 
 only a few pence each, giving chromo-lithographic examples 
 of various simple studies in water-colour painting by 
 Callow and other artists, under the title of " Yere Foster's 
 Drawing Books." These books, I believe, are still to be 
 had, — at least, I hope so, for they are full of merit, and 
 give more valuable instruction than many works of far 
 more pretension. They give specimens of water-colour 
 sketches, unfinished and finished, side by side. Perhaps 
 the former are the more valuable for our present purposes, 
 for they exhibit merely broad masses of colour, and show 
 how one tint can be made to contrast with another. It 
 will be seen in some of these pictures that a blue sky is 
 contrasted with orange yellows in the landscape beneath ; 
 and how, on the other hand, a yejlow sky can be rendered 
 at once effective by purple hills upon which it seems to 
 rest. 
 
 When the picture is entirely finished, it may be once 
 more submitted to the baking operation, taking care that 
 the heat never rises to blistering point, or all the labour 
 spent on the slide will be thrown away. The picture may 
 now again be placed on the easel, and if the artist has 
 sufficient reliance upon his power of knowing when to stop 
 
170 
 
 THE BOOK OF THE LANTERN. 
 
 he may with advantage take up the etching-needle ; some- 
 times a single touch of this magic wand will much improve 
 a picture. In forest scenery, for instance, a light on a 
 trunk, or on a protruding branch, will make the one or the 
 other to stand out almost stereoscopically. Now and then 
 too a little spot or two may be picked out of the foliage 
 itself. But not in the manner I lately saw in an exhibited 
 slide, where curly lines, after the drawing-master style of 
 former days, were made to describe the edges of the trees 
 in every direction. This was actually perpetrated upon a 
 good photograph, and represents the worst instance of 
 " painting the lily " which I have had the misfortune to 
 come across. 
 
CHAPTER XIII. 
 
 DESCRIPTION OF VARIOUS EXPERIMENTS, — CHEMICAL, ELECTRICAL, 
 ETC., — FOR CLASS INSTRUCTION, WHICH ARE POSSIBLE WITH 
 THE LANTERN. 
 
 OR different experiments, various forms of slides 
 must be employed. The galvanometer slide, 
 shown at fig. 45, is an extremely useful 
 one for demonstrations in electricity and magnetism. 
 I need hardly mention that such a slide consists of 
 a magnetised needle, which is surrounded by a coil 
 
 Fig. 45. 
 
 of fine wire. This coil is flattened, and there is just 
 
 space enough between its convolutions for the needle 
 
 to move from side to side. It is supported on 
 
172 
 
 THE BOOK OF THE LANTESN. 
 
 a central pin, which is shown bj the screw slit in the cut. 
 
 A pane of glass of a semicircular shape forms a back- 
 ground for the needle ; and this glass can either be left 
 plain, as in the illustration, or it can have drawn upon it a 
 scale. The slide figured is without the arrangement just 
 mentioned, and it is one that I have employed for a special 
 purpose. I have used it as a means of demonstrating the 
 action of the needle telegraphic instrument; and it will 
 be noticed that two little buttons are fastened to the 
 glass in order to prevent the needle making too wide an 
 excursion. 
 
 It may be mentioned here for the benefit of those who • 
 are unused to electrical instruments, that a galvanometer 
 furnishes the means of detecting the existence of an elec- 
 tric current. In its higher forms it is so sensitive that 
 a current, generated by touching two dissimilar metals 
 with the fingers and excited by the natural warmth of the 
 band, can, by a galvanometer, be made evident to the eye. 
 The most simple form of galvanometer can be readily 
 made from one of those little charm compasses which are 
 sold at the opticians' for about Is. each. Take such a 
 compass, and bind it across with several layers of fine silk- 
 covered copper wire. Place it in such a position that the 
 wire coil lies parallel with the needle, which will, of course, 
 be north and south ; now join the entls of the wire to 
 any form of electric battery, and the needle will imme- 
 diately swing round and take an east and west direction. 
 By changing the position of the wires with regard to the 
 poles of the battery, it will be noticed that the needle is 
 deflected in the opposite direction. These phenomena 
 
THE BOOK OF THE LANTERN. 
 
 173 
 
 form the basis of the single needle electric telegraph, and 
 it is to demonstrate the powers of that telegraph that the 
 lantern galvanometer, which 
 is here figured, has been 
 devised. It will be noticed 
 that on its right-hand side it 
 is furnished with two ter- 
 minals. These are connected 
 with the ends of the coil 
 wire, and provide a means of 
 readily joining the instrument 
 up to the battery, placed in 
 any position outside the lantern ; but in practice it will 
 be found advisable to also place in connexion with this 
 slide and its battery a little piece of apparatus which may 
 be called a "current reverser," which can easily be made 
 at home. It is shown in fig. 46. It consists of two 
 little treadles formed out of brass. This brass, it may 
 be mentioned, should be of the hard-rolled kind, such as 
 is used for springs. 
 
 Each of these little treadles is fastened down to a maho- 
 gany b rd, which forms the base of the instrument, and 
 each OxiO is in connexion with a terminal screw, which is 
 indicated in the cut by a round dot. Across the other end 
 of the treadles is a raised bar of brass, against which they 
 spring up and touch when in their normal condition ; but 
 when either of them is pressed down, it touches a piece of 
 brass wire which is let into the top of the mahogany board 
 immediately underneath. 
 
 This wire, as well as the piece of brass just mentioned, 
 
in 
 
 THE BOOK OF THE LANTERN. 
 
 is connected with its own terminal ; these two latter ter- 
 minals in the cnt being lettered bb, and signifying that 
 they should be joined up to the battery employed. The 
 other two, which are lettered gg, are fastened to the 
 terminals on the galvanometer slides. 
 
 In practice it is best for the current reverser to be placed 
 on the lecturer's desk, at some distance from the lantern, 
 while the galvanometer slide is joined up by means of tem- 
 porary wire connexions. The lecturer then has the power 
 of reversing the current by touching with his finger either 
 of the two treadles, and he can demonstrate in the most 
 perfect manner how the different letters in the tele- 
 graphic alphabet are made up of movements of the needle 
 to the right or left, as the case may be. He can also point 
 out that the " dots " and " dashes " of the Morse system 
 correspond with these right and left hand movements of 
 the magnetic needle. 
 
 In the old days of the Polytechnic Institution in Regent 
 Street, which was the resort of so many delighted schoolboys 
 and girls, there were several experiments performed with the 
 lantern which, so far as I know, have not been repeated 
 lse where. One of the most curious was the movements of 
 the legs of a frog. This is rather a difficult experiment tc 
 perform, but when well done, is highly effective on the 
 screen. 
 
 At the Polytechnic the frog's legs covered the large 
 screen, and were thus magnified to about 26 feet. The legs 
 were hung to a special form of slide, and the nerves and 
 muscles of the dead frog were touched with metallic wires, 
 when they immediately kicked out in the most startling 
 
THE BOOK OP THE LANTERN. 
 
 175 
 
 manner. The importance of this experiment, as a demon- 
 stration, will be acknowledged when it is remembered that 
 this movement of a frog's legs, accidentally brought about 
 by Galvani, laid the foundation of our present knowledge of 
 current Electricity or Galvanism, as it used to be called, 
 after that first experimenter. 
 
 Another most effective experiment was shown in con- 
 nection with a lecture upon the Suez Canal by Professor 
 Pepper. After exhibiting a number of experiments upon 
 sand, and showing that it always fell at a certain angle, 
 and exerted lateral instead of perpendicular pressure, 
 an image of an ordinary hour-glass was cast upon the 
 screen. This sand-glass was supported in a frame, and its 
 sides were flattened so that it could fit the lantern stage. It 
 had rather an amusing appearance, because like all instru- 
 ments placed in the lantern, the image was inverted, and 
 the sand therefore appeared to flow upward instead of 
 downward. A curious fact, too, was noticed when this 
 familiar instrument was magnified to such an enormous ex- 
 tent, each particle of sand was seen to strike a blow upon 
 the top of the cone above, and the force from that blow 
 passed from the point of the inverted cone to its base, and 
 formed a peculiar wave-like figure in its passage. 
 
 I have never seen this experiment repeated elsewhere, 
 but it is one that should not be forgotten. 
 
 Among the experiments which can be performed by 
 means of a lantern, and better performed, — so far as an 
 audience is concerned, — than by any other means, are 
 those relating to cohesion figures. Professor Tomlinson 
 was the first to give much attention to these interesting 
 
176 
 
 THE BOOK OF THE LANTERN. 
 
 figures, and lie made many experiments in this direction. 
 He found that almost all the common oils and fats give 
 natural diagrams by which they can be identified; and 
 further, that these figures will vary, according to the length 
 of time for which the oil has been exposed to the air. To 
 get some idea of the nature of these beautiful figures, a 
 drop of pure sperm oil may be allowed to fall on the surface 
 of a pan of water. It will be seen in a few seconds that 
 the film of oil will break up into a number of little open- 
 ings, and that it will exhibit a pattern of great beauty. 
 Hape oil, Lucca oil, and some others, give patterns of en- 
 tirely different designs ; some of them very much resembling 
 beautiful crochet-work. In order to show these patterns 
 in the lantern, we have two or three different methods of 
 going to work. We can exhibit these cohesion figures, for 
 instance, by the simple aid of two pieces of clear glass. 
 Between two such plates put a little vaseline, which in 
 order to increase the effect on the screen may be coloured 
 red with alkanet root. The plates are pressed together, with 
 the vaseline between them, and are then secured by a ring of 
 india-rubber at each end. They are then put into the lan- 
 tern, and while standing upon the lantern stage the blade 
 of a knife is inserted between the two glasses and gradually 
 turned so that they are slightly separated. The effect 
 upon the screen is very beautiful, the disc appearing to be 
 covered with arborescent figures. This experiment may be 
 repeated more than once, but the vaseline will require 
 renewal after a time. Another mode, and perhaps a better 
 one, of showing the same phenomena, is by means of the 
 vertical attachment to the lantern. In this case the 
 
THE BOOK OP THE LANTERN. 
 
 177 
 
 lantern slide must take the form of a shallow box, having 
 a glass bottom. Such a box can easily be made by fit- 
 ting a piece of thin glass, say, 3 \ inches square, into 
 a frame of wood half an inch in height, and cementing 
 the glass in a groove with marine glue. The glass 
 cell so provided should be placed in a horizontal 
 position upon the stage, and be filled with water. Dif- 
 ferent oils can then be dropped on to the surface of the 
 water, and the characteristic cohesion figures due to each 
 will be thrown upon the screen. If this latter mode of 
 showing the phenomena be chosen, it is obvious that a 
 different glass cell must be used for each oil exhibited, 
 and I think that it would be quite possible to produce 
 lantern slides direct from these oily cohesion figures ; 
 although I have not experimented in this direction myself. 
 The principle employed would be that of " Lithography." 
 The oily figures might be transferred to a piece of glass 
 direct from the surface of the water. Those figures could 
 be darkened to any extent by employing a greasy printing 
 ink, taking care to wet the glass so as to repel the ink ; 
 but this is a matter into which I cannot now afford space 
 to enter, and I merely allude to it as a field for profitable 
 experiment. 
 
 Many pieces of apparatus have been devised for the 
 lantern, which exhibit the principle of what is known as 
 " persistence of vision." In older that we may thoroughly 
 understand in what this principle consists, I may men- 
 tion that the human eye possesses a peculiar property 
 which is highly convenient to its proprietor. What is 
 meant by " persistence " is that the retina has the power 
 
 N 
 
178 
 
 THE BOOK OF THE .LANTERN. 
 
 of retaining the image of anything seen for at least one- 
 eighth part of a sec d after the eye ceases to see that 
 object. 
 
 As an example of this, let me remind my readers, that 
 although in the ordinary course of things, we are con- 
 tinually "winking," an operation which is necessary to 
 lubricate the eyeball, we are quite insensible of the cir- 
 cumstance that for the time occupied in doing so, we are 
 placed in absolute darkness. Although the eyelids are 
 closed and the light is shut out, we have no perception of 
 darkness, simply because of this curious property possessed 
 by the retina of retaining the image of the object last seen, 
 for at least the eighth part of a second. It is for this 
 reason, — I may also point out in passing, — that so-called 
 instantaneous photographs of moving objects, such as a 
 "trotting horse," &c, appear to us to exhibit such very 
 unnatural attitudes. As a matter of fact the photographic 
 camera records movements which the human eye, on account 
 of this "persistence of vision," cannot appreciate. It is 
 evident that if this doctrine be true, the eye cannot appre- 
 ciate a movement which takes place in less time than the 
 eighth part of a second, and it is because the photographic 
 lens can grasp and record the movements which take place 
 in a mere fraction of that time, that the attitudes it depicts 
 appear to us so highly unnatural. The human eye has 
 never seen such attitudes, and never will see them. 
 
 Perhaps the simplest illustration of " persistence of 
 vision " is afforded by a burnt stick with a red hot end, 
 which is turned rapidly round in front of the observer ; 
 to that observer the red spot of light looks like a con- 
 
THE BOOK OF THE LANTERN. 
 
 179 
 
 tmuous ring of fire, but we know well enough that it is 
 simply a spark. It is the rapid movement helped by this 
 " persistence " of the retina, that causes the spot of light to 
 appear to us as a continuous circle. So it is that heavy 
 rain drops, — which we know very well are independent 
 globules of water, — appear to be like streaks falling from 
 the sky, and like streaks artists invariably depict them. 
 And rightly so, too, for we do not wish artists to bring 
 before us representations of things as the eye cannot see 
 them, but of objects as they appear to us under ordinary 
 conditions. For this reason the claim which has been made 
 in some quarters, that the unusual attitudes depicted by 
 instantaneous photography, should be a help to artists in 
 their delineation of animal movement, appears to be ex- 
 tremely nonsensical. Such attitudes may certainly be 
 studied by artists, as a means of showing how the various 
 movements are brought about, just as he would study the 
 skeleton of a man, in order to get a better notion of the 
 outward form of the body ; but both should be kept as 
 studies, and certainly not introduced into finished works. 
 
 The kaleidotrope consists of a disc of perforated cardboard. 
 It is supported on a spring of wire in such a manner that it 
 can be rapidly turned round by the finger as the frame in 
 which % it is contained stands upon the lantern stage. The 
 other end of the spring is cemented to a plate of glass so 
 that the light can easily travel through the perforations in 
 the disc and be rendered evident on the lantern screen. 
 As this card is struck with the finger so as to cause it to 
 move and vibrate on its spring in different directions, 
 the spots of light on the screen by their movement assume 
 
 n 2 
 
180 
 
 THE BOOK OF THE LANTERN. 
 
 a great variety of curves. It will be thus seen that this 
 instrument simply gives a variation of the burnt- stick 
 experiment already alluded to. 
 
 Mr. Beale, of Greenwich, has invented a most ingenious 
 and amusing apparatus for the lantern which also depends 
 upon " persistence of vision." This is called the choreuto- 
 scope, and is made in two different forms. In its more elabo- 
 rate shape it consists of a circular plate having upou it figures 
 drawn upon glass, and so arranged with their limbs in 
 different attitudes, zoetrope fashion, that when one figure 
 is rapidly changed for the other, the image seems to be in 
 actual movement. The contrivance is so arranged that 
 before the figure actually changes a little screen obscures 
 it for the moment, so that the movement of the disc is not 
 apparent upon the sheet. Mr. Beale has of late years 
 simplified this instrument. In this case the figures are 
 painted upon a slip of glass about seven inches in length, 
 and by means of a special form of slide they are rapidly 
 brought in front of the lens in the manner just described. 
 
 The most effective set of figures of any is a skeleton, the 
 reason being that it consists only of white on black. 
 Such figures can therefore be cut out, stencil fashion, in 
 a sheet of thin copper-foil ; the openings in this plate per- 
 mitting a far larger amount of light to reach the screen 
 than if the figures were drawn upon glass. 
 
 Another far more perfect and elaborate device for illus- 
 trating the phenomena connected with persistence o 
 vision is an instrument called by the somewhat ponderous 
 title, — the Astrometeoroscope. The inventor of this clever 
 oiece of apparatus was the Hungarian mechanician, 
 
THE BOOK OP THE LANTERN. 
 
 181 
 
 S. Pichler, who designed various other ingenious contriv- 
 ances. He was very jealous about this astrometeoroscope, 
 and the only one made was at the Polytechnic Institution, 
 where it was carefully kept under lock and key, except 
 when in actual use. When the apparatus of the institution 
 came to the hammer, I remember that there was some 
 little excitement when the astrometeoroscope was put up 
 for sale. Opticians and others would have been glad to 
 get hold of it, so as to have multiplied it for sale. This led 
 to a brisk competition, ending with Mr. Pichler giving an 
 extravagant price for his own bantling. And in that way 
 the secret remains in the hands of a few only, and perhaps 
 it would be unkind to divulge it. But,' at any rate, I 
 cannot do much harm by giving a general idea of the out- 
 ward appearance of the instrument and its capabilities. 
 
 The astrometeoroscope consists of a narrow box thirteen 
 inches in length, and of such a width that at one end it 
 will fit the stage of the lantern. At this end it has the 
 usual three-inch disc opening, which is occupied by two 
 plates of metal which are scored across obliquely with slits 
 and which are superposed one on the other, so that the 
 slits on each cross one another diagonally. Now it 
 is clear that the only places where light can pierce 
 these plates of metal so as to make itself evident on 
 the screen is in those places where the slits on the plates 
 intersect one another. The effect on the screen, therefore, 
 whilst the instrument is quiescent, is a series of dots of 
 light all over the screen, but at regular distances from one 
 another. By very ingenious mechanism the two plates are 
 caused to move to and fro in contrary directions, and the 
 
182 
 
 THE BOOK OF THE LANTERN. 
 
 speed of either can be varied at will by the operator. The 
 effect upon the screen is most curious, for it seems to be 
 covered with a lacework of geometrical patterns which 
 constantly change their form. 
 
 A very favourite experiment with the lantern, but one 
 which it is by no means easy to perform, is the decomposi- 
 tion of light by means of a prism. For the most perfect 
 effects the electric light is necessary, but as this is beyond 
 the reach of most of us, — at any rate, for the present, — we 
 must be content with what can be done with the ordinary 
 limelight. The simplest way of showing the spectrum 
 with the lantern is to remove the objective and to place in 
 the lantern stage a card with a slit in it, as 
 I shown in the cut (fig. 47). This slit should be 
 
 BBjfcffiiSt a kout an inch in length, and not more than 
 H one-twentieth of an inch in breadth. The card 
 should be placed on the stage of the lantern in a 
 
 Fig. 47. nor i ZO ntal position and focussed upon the screen 
 in front. A prism is then brought into the path of the 
 slice of light thus formed, 
 and it will be so far bent 
 aside as to exhibit the 
 colours of the spectrum on 
 the ceiling of the room 
 
 (fig. 48). Fig. 48. 
 
 The prism will require a little turning about before this 
 result is arrived at. But at the best this method of show- 
 ing the spectrum is but a makeshift one ; it presents, 
 however, an easy method of demonstrating the decom- 
 position of white light. A preferable mode is to use a 
 
THE BOOK OF THE LANTERN. 
 
 183 
 
 bisulphide of carbon prism. This takes the form of a 
 stoppered bottle with two sides ground away and filled in 
 with plates of glass, which are cemented to the re- 
 mainder of the bottle. In this way the wedge form 
 of the prism is secured. The bottle is then filled with 
 bi-sulphide of carbon, and such bottles, ready charged, can 
 be obtained at the opticians'. A great objection to them 
 is their liability to breakage, for bi-sulphide of carbon, 
 beyond being a most inflammable compound, has a most 
 disagreeable and pungent odour. 
 
 In using a prism of this description, it is kept upright 
 and supported in front of the lantern. The slit in the card 
 must in this case be vertical, instead of horizontal, and the 
 lantern must be placed at such an angle with the sheet 
 that when the spectrum is rendered visible it appears in a 
 central place on the sheet. 
 
 There are several means available for showing on the 
 lecture-table that the various colours of the spectrum will, 
 when combined, once more form white light. Thus we 
 may place in the path of the coloured beam a double con- 
 vex lens, which will at once bring the scattered rays to a 
 focus, and will form a disc of white light. We can also 
 recompose light by collecting the coloured rays by means 
 of a concave mirror, when a card held in the focus of the 
 mirror will exhibit a brilliant spot of light free from 
 colour. Another method is to use two prisms placed 
 against one another, thus — Ay> when one will neutralise 
 the effect of the other, and the emergent beam will be 
 white. Yet another way of recomposing light is to use a 
 number (generally seven) of plain mirrors, which are so 
 
184 
 
 THE BOOK OF THE LANTERN. 
 
 placed upon a stand that they can each be turned in any 
 required direction. The spectrum is allowed to fall upon 
 this system of mirrors, and each one is so turned upon its 
 axis that the particular colour which it reflects is thrown 
 upon one spot. The collective images of the various 
 colours then appears as a white disc. 
 
 The methods thus detailed are all good, but cannot 
 readily be applied to the lantern. A way of demonstrating 
 the recomposition of light with that instrument has 
 recently been published in America, by Mr. G. M. Hop- 
 kins, and the following remarks are borrowed from him. 
 After detailing the various known methods of recomposing 
 light, he says : — " Besides these methods, the spectrum has 
 been recombined by whirling or rocking a prism ; the move- 
 ment of the spectrum being so rapid as to be beyond the 
 power of the eye to follow, the retina receiving the impres- 
 sion merely as a band of white light, the colours being 
 united by the superposing of the rapidly succeeding 
 impressions, which are retained for an appreciable length 
 of time. The engraving shows a device to be used in 
 place of the ordinary rocking prism. It is perfectly 
 simple, and involves no mechanism. It consists of an 
 inexpensive prism, having attached to a knob on either 
 end a rubber band. In the present case the bands are 
 attached by making in each a short slit, and insert- 
 ing the knobs of the prism in the slit. The rubber 
 bands can be held by inserting two fingers in each and 
 drawing them taut. The prism can then be held in a 
 beam of sunlight, and with one finger the prism is given 
 an oscillating motion. The band of light thus elongated 
 
THE BOOK OF THE LANTERN. 
 
 185 
 
 will have prismatic colours at opposite ends, but the entire 
 central portion will be white. To show that the colours of 
 the spectrum pass over every portion of the path of the 
 light, as indicated by the band, the prism may be rocked 
 very slowly. 
 
 "By inserting four screw hooks in a vertical support, and 
 stretching the bands over the hooks, the prism is adapted 
 for use with a lantern. The light emerging from the 
 lantern must pass through a narrow slit to secure a per- 
 fect spectrum, and between the screen and the prism 
 should be placed another screen with an oblong aper- 
 ture, which will allow all of the band of light to appear 
 upon the screen, with the exception of the coloured 
 extremities. With the prism supported in this way, it is 
 an easy matter to turn it slowly back and forth, showing 
 on the screen the moving spectrum, which, with the more 
 rapid movement, produces the pure white band of light." 
 
 The recomposition of light can be well shown in the 
 way just described ; but perhaps a more ready and effec- 
 tive, if not quite so scientific, a method is to use a coloured 
 disc, fitted as a lantern-slide, with a revolving arrangement 
 similar to that used for chromotropes. 
 
 Newton's disc, as it is called, consists of all the colours 
 of the spectrum, painted in transparent colours, in their 
 right proportions, upon a revolving disc, and as this 
 disc is rapidly turned in the lantern, the various 
 colours projected upon the screen in front mingle together 
 on the retina, and the general effect is that of white 
 light. It may happen that a lecturer may touch 
 upon the study of spectra without wishing to burden him- 
 
186 
 
 THE BOOK OF THE LANTERN. 
 
 solf with the necessary apparatus for showing them upon 
 the screen. Or he may be employing a large lantern to 
 illustrate other parts of his lecture, which would be quite 
 unsuitable, — or, at any rate, would have to be re-arranged 
 ' before a single spectrum experiment could be shown. 
 Feeling this want myself, I devised a plan for showing- 
 spectra diagramatically with an ordinary biunial lantern. 
 (It will presently be seen that a double lantern is a neces- 
 sity for this particular manner of working), and I have 
 found the method adopted to answer admirably. A special 
 set of slides is required, but these are not at all difficult 
 to make. They must be home-made, for they are not to 
 be bought at present, although one well-known optician 
 was so pleased with the idea when I described it to him, 
 that he expressed his intention of manufacturing slides of 
 my pattern. The first of the set is a photographic slide 
 showing Newton's well-known experiment with a prism, 
 traversed by a beam of light admitted through an aperture 
 in the shutter of a darkened room. The next slide is a 
 simple-coloured band, or continuous spectrum. This is at 
 length replaced by a similar band, no longer continuous, but 
 crossed by the principal Frauenhofer lines, which are duly 
 marked above with their own distinguishing letters. Such 
 a spectrum can be copied from any work on optics, and 
 drawn and coloured on ground-glass, as explained in 
 another part of this book. We must now prepare a set of 
 slides to serve as " effects " for this last spectrum slide, 
 and which will consist of simple bright lines. The most 
 simple of these would be that due to the metal sodium, 
 which would consist of a double yellow line, to agree in 
 
THE BOOK OT THB LANTERN. 
 
 187 
 
 position with that marked D in the spectrum -slide. To 
 produce such a slide it is only necessary to paste over a 
 piece of glass a piece of stout black paper, and to cut 
 out with a sharp knife, when the paper is dry, the line 
 required. A little varnish colour over the cut-out place will 
 complete the slide. In using this " effect 99 the audience 
 should have explained to them the theory which seeks to 
 explain the reversal of the lines in the spectrum, and at 
 the right moment the spectrum-slide is so far darkened 
 by moving the lantern-dissolver, that the clear sodium 
 line shines out brightly over the spot occupied before by 
 the dark D line. I need hardly say that the two slides 
 must be in perfect register, or the effect will be spoiled. 
 The spectrum-slide can now be once more exhibited, and 
 another bright line example placed in the other lantern 
 ready to be made visible as the sodium one was just 
 now. The spectra of all the different metals can thus be 
 illustrated by the bright lines which they afford. The 
 method may perhaps be considered rough, but the effect is 
 startling, and few among a general audience are able at 
 once to realise how it is done. 
 
 Double refraction can be shown on the screen in the 
 following manner : A card with a simple perforation about 
 one-eighth of an inch in diameter is inserted on the lantern- 
 stage, and its image is focussed on the screen. A crystal 
 of Iceland spa is then placed between this card and the 
 objective lens, and two spots of light will become apparent 
 upon the sheet. 
 
 It may be mentioned here that in all experiments where 
 colour is required it is better, if possible, to use coloured 
 
188 
 
 THE BOOK OF THE LANTERN. 
 
 gelatine than any other medium. Ordinary coloured glass 
 absorbs so much light that it is of very little use in lantern 
 experiments ; and if the operator will try the effect of 
 coloured glass and coloured gelatine side by side he will 
 be surprised at the advantage gained from using the latter. 
 There is one objection to gelatine, and that is, if a very 
 powerful limelight be used it is apt to be affected by the 
 heat ; but this is only the case if the medium in question 
 is kept for a protracted time on the lantern-stage. 
 
 A large number of experiments illustrating the theory 
 of colour and the laws of complimentary tints can be 
 arranged by means of pieces of cardboard with different 
 shaped orifices cut in them, filled in with coloured gelatine. 
 Such examples will easily suggest themselves to any 
 operator with the assistance of a reliable book on the 
 theory of colour. I may mention here a simple arrange- 
 ment for showing the way in which the retina becomes 
 fatigued by looking at an object for some time. 
 
 It consists of a card with 
 two semicircular openings, 
 n divided by a horizontal bar 
 | (see fig. 49). Over one open- 
 • ing, say the lower one, a 
 Fig. 49. piece of card is placed so 
 
 that the image of the upper one alone is projected upon 
 the screen. After looking at this image for some time, 
 the card obscuring the lower opening is suddenly with- 
 drawn, and it is then strange to note how one opening 
 appears to be far duller than the other, although both are 
 in reality equally illuminated. 
 
THE BOOK OF THE LANTERN. 
 
 189 
 
 Another method which illustrates the tiring of the 
 retina, and which also demonstrates the law of compli- 
 mentary colours, can be shown thus : — 
 
 A card having a round opening in the centre, filled in 
 with red gelatine, is placed on the lantern stage, and its 
 image allowed to remain upon the sheet for some little 
 time, the attention of the spectator being concentrated 
 upon it. Thd gelatine is suddenly removed, when al- 
 though the image of the opening is of course perfectly 
 white, it appears to be green, because the retina is tired 
 by its exposure to the red, and can only for a time appre- 
 ciate the remaining colours of the spectrum, which mingled 
 form green; of course, any primary colour can be chosen 
 for the experiment, and its complementary tint will be 
 made manifest. This is but a variation of that advertise- 
 ment which has been so common in our streets for some 
 time, where the onlooker is invited to gaze upon cer- 
 tain colours for so many seconds, when the image of the 
 coloured letters looked at will appear, bi*t in their com- 
 plementary tint, upon the blank space above. 
 
 For experimental work with the lantern, a special form 
 of instrument should be used. I have lately seen a form 
 which I think found its origin in Germany; in which the 
 objective is so arranged on a sliding base board, that a 
 clear space of some inches is left between it and the lantern 
 condensers ; while a little table between the two serves to 
 support any object whose shadow it is desirable to throw 
 upon the screen. If we are content with the mineral oil 
 lantern, — and with such a lantern a great many experiments 
 can be shown, at any rate in a small room, — rwe can ar- 
 
 * 
 
190 
 
 THE BOOK OP THE LANTERN. 
 
 range matters in a very simple manner. Let the lantern 
 stand on a base board, and let the objective be supported 
 upon a sliding piece in front of that board. Cut away the 
 tin nozzle upon which the objective fits in the ordinary 
 way, so that any object can easily be brought between 
 condenser and objective. Or to still more simplify the 
 matter, we can use the lamp only of one of these mineral 
 lanterns and place it as figured in the annexed cut (fig. 50). 
 
 Fig. 50. 
 
 Here we have a base board AA, with a fixed support in the 
 centre B, which is pierced with a hole sufficiently large to 
 contain the condensers of the lantern. Close up to this 
 is placed the lamp L. Another support, C, holds the objec- 
 tive, and this support by means of a sliding piece let into 
 the base board, can be moved to and fro for focussing pur- 
 poses in front of the condensers. It will be seen that by 
 adopting this arrangement, no lantern is necessary. We 
 simply require the illuminator, which must of course be 
 closed in, as sold with most lanterns ; a condensing lens ; 
 and an objective. 
 
 The number of beautiful experiments which are possible 
 with the use of a glass tank, or rather, several glass tanks 
 of the simple form shown in fig. 51 are surprising. Most 
 
THE BOOK OP THE LANTERN", 
 
 191 
 
 of these are of a chemical nature, but there aro others 
 which exhibit physical phenomena in a manner which is 
 perhaps, impossible by any other means, or rather, we may 
 say, that experiments which can only under normal con- 
 ditions be viewed by one or two pairs of eyes on the lecture 
 table, can by means of this tank be made visible to a large 
 audience. 
 
 A fine experiment showing the formation of vortex 
 rings may be shown in the following way. Having filled 
 the tank with clean water, take a penholder or a piece of 
 stick pointed for the purpose and dip it into some milk, so 
 that a drop forms at the end of it. Bring this carefully over 
 the tank and allow the milk to just graze the surface of 
 the water, when it will form a white ring in the fluid 
 which will fall gradually downward, but on the screen, 
 of course, it will appear to rise upward. This ring as it 
 travels to the bottom of the tank will give rise to other 
 similar rings, so that presently there will be quite a number 
 of circles slowly moving upwards on the screen. This* 
 experiment is one which will illustrate well the formation 
 of smoke rings, and of the more important phenomena of 
 whirlpools and whirlwinds. 
 
 Another experiment of a similar nature, and giving a fine 
 effect on the screen, may be performed by filling the tank 
 to within half an inch of the top with methylated spirit. 
 Take now instead of a wooden rod one of glass, or a camel 
 hair brush will do as well. Dip it into an alcoholic solution 
 of any of the aniline dyes, and just allow the drop which 
 hangs from it to touch the inner side of one of the glasses 
 of the tank. Directly this drop reaches the alcohol, it will 
 
192 
 
 THE BOOK OF THE LANTERN. 
 
 descend and immediately break out into a number of 
 branches. These branches will on the screen appear to rise 
 rapidly upwards after the manner of a number of coloured 
 rockets, and by varying the colours of the dyes and putting 
 one or two drops into the tank simultaneously, a most lovely 
 effect on the screen is obtained. 
 
 The decomposition of water is another experiment which 
 has a most curious effect. For this experiment a small electric 
 battery is necessary, and the most convenient form to use is 
 a single bichromate cell, say of one pint capacity. This can 
 be hidden away in a box beneath the lantern, and as it 
 gives off no fumes, there is nothing disagreeable in its use ; 
 moreover its action, if freshly charged, is energetic, and this 
 action can be stopped when required by lifting the zinc 
 plate from the solution in which it is immersed. The wires 
 from the poles of the battery must be long enough to reach 
 the lantern stage ; the slide for this experiment being simple 
 in the extreme. The tank to be used should be of rectangular 
 •form, and as a matter of convenience, it should be furnished 
 with two binding screws on one of its outer sides, so that 
 the wires from the battery can be readily connected with 
 them. These screws should be in connection with two 
 gutta-percha covered wires, which proceed to the bottom of 
 the tank, where their ends are bare and turned upwards for 
 about a quarter of an inch. These ends may be so fixed 
 that they are about half an inch apart. The tank is pre- 
 viously filled with diluted sulphuric acid (one part of acid 
 to eight of water), and is then ready for action. Directly 
 connection is made with the battery, the two wires will 
 rapidly give off bubbles of gas, one being hydrogen and 
 
THE BOOK OF THE LANTERN. 
 
 193 
 
 the other oxygen. It is possible to elaborate this slide by 
 crowning the two terminals with tiny inverted test tnbes, 
 filled with the acidulated liquid. In this case the bubbles 
 of gas displace the contained water in the tubes, the hydro- 
 gen tube being readily distinguished by being emptied of 
 water at double the rate of the tube devoted to the oxygen 
 gas. This proves in a very direct manner the composition 
 of water, which consists of two volumes of hydrogen to 
 one of oxygen. 
 
 In order to show the generation of hydrogen gas alone, a 
 still more simple arrangement can be adopted. The electric 
 battery is not used for this experiment. A few pieces of 
 granulated zinc are dropped into the tank of acid water, 
 when bubbles of hydrogen will be rapidly given off, their 
 downward descent upon the screen giving a very peculiar 
 effect. 
 
 In like manner carbonic acid gas can be generated by 
 using a few pieces of marble instead of the zinc, aud sub- 
 stituting for the sulphuric acid water which has been acidu- 
 lated with hydrochloric acid. We can also easily show 
 that one of the products of the lungs is this same carbonic 
 acid gas. In this case the tank must be filled with lime 
 water, which will remain perfectly clear until it is blown into 
 from the lungs by means of a tiny glass tube, when bubbles 
 of air will rise from the water, and the liquid will rapidly 
 become cloudy, proving that the carbonic acid from the 
 lungs has formed carbonate of lime, or common chalk, in 
 the water. 
 
 It will be noticed that in all tank experiments it is 
 necessary that the lantern stage should be open at the top 
 
 o 
 
194 
 
 THE BOOK OF THE LANTERN. 
 
 and such experiments are for this reason best performed 
 with a lantern having the simple construction shown in 
 Fig. 49. These experiments are so valuable for educa- 
 tional purposes, and can so easily be shown with ordinary 
 oil-lit lanterns that it is to be hoped that manufacturers 
 will see the necessity of providing for them by the adop- 
 tion of an open stage. 
 
 The composition of Prussian blue can be easily demon- 
 strated by means of the chemical tank. For this experiment 
 we shall require a solution of the yellow prussiate of 
 potash from which the colour takes its name. This is 
 placed in the tank. Have in readiness a solution of sul- 
 phate of iron or green vitriol. On pouring the contents 
 of this bottle by means of a pipette into the tank, a heavy 
 blue precipitate is thrown down, but as this precipitate is 
 opaque the colour is not perceptible on the screen ; but by 
 adding to the blue precipitate a few drops of sulphuric 
 acid, and following this by a little bi-chromate of potash 
 in solution, a brilliant transparent blue is immediately 
 made apparent. The formation of other colours can by 
 reference to any book on chemistry be readily demon- 
 strated. 
 
 The tests for acid and alkaline solutions by means of 
 litmus can be demonstrated in the following way : — 
 
 Fill the tank with a solution of litmus or with an in- 
 fusion of purple cabbage, made by slicing a few of the 
 leaves, and pouring boiling water upon them. Place either 
 of these solutions in the tank, when, upon adding a small 
 quantity of acid, the liquid will be seen to turn red ; sub- 
 sequent addition of an alkali, such as a weak solution of 
 
THE BOOK OF THE LANTERN. 
 
 195 
 
 ammonia, will quickly restore the original colonr, and these 
 changes from red to blue, and vice versa, can be continued 
 by adding acid and alkali alternately, as often as may be 
 required. 
 
 If the tank be charged with a solution of sulphate of 
 iron and gallic acid be added to it, a black solution of ink 
 will immediately be produced. Another pretty experiment 
 demonstrates the presence in hard water of various mineral 
 matters which will cause certain chemicals to give a 
 precipitate which they would not do in water that has 
 been freed from mineral matter by distillation. A good 
 plan of showing this is to suspend in a tank a crystal of 
 oxalic acid. As the crystal dissolves in the water long 
 threads of oxalate of lime will be given off by it, forming 
 a very curious appearance on the screen. It may then be 
 shown that by the substitution of distilled for hard water 
 the crystal will dissolve all the same, but these threads will 
 not be given off, because there is no lime present to form 
 them. The action of bleaching powder, commonly called 
 chloride of lime, is well shown by filling the tank with a 
 solution of indigo, which has been acidified with sulphuric 
 acid. Upon adding a solution of the bleaching powder, 
 the sulphuric acid will liberate the chlorine contained in 
 it, and will discharge the blue colour of the indigo, leaving 
 the disc on the screen perfectly white. 
 
 The precipitates caused by the admixture of various 
 chemicals is not effective in the lantern, for the reason that 
 most of these precipitates are opaque, and therefore they 
 look black upon the screen. 
 
 For instance, we may fill a tank with a solution of 
 
 o2 
 
196 
 
 THE BOOK OF THE LANTERN, 
 
 common salt, — i.e., the chloride of sodium, — and upon adding 
 to this a small quantity of nitrate of silver in solution, a 
 heavy white precipitate of chloride of silver is thrown 
 down, but as this is perfectly opaque it will only appear on 
 the screen as black clouds. 
 
 Other very beautiful experiments may be performed to 
 demonstrate the crystallisation of various salts. Plates of 
 glass may be prepared beforehand with saturated solutions 
 of the salts, and these plates, slipped into a slide carrier, 
 can be used for projection, giving very fine effects. But 
 by far the most striking way of exhibiting these interesting 
 phenomena is to show the crystallisation actually in 
 progress. 
 
 This is easy enough if the lantern be furnished with a 
 vertical attachment, but not so easy without such an 
 appendage. But the following experiments can be readily 
 performed with an ordinary lantern. Prepare a saturated 
 solution of sal-ammoniac, and with the help of a camel-hair 
 brush cover a clean glass plate with the liquid ; place this 
 glass on the lantern stage, when the heat from the lamp 
 will speedily cause the water to evaporate and the crystals 
 to form on the glass. It will be noticed that in the crys- 
 tallisation of this salt the branches of the marvellous tree, 
 which grows so rapidly on the screen, always keep at a 
 particular angle to its stem. Another experiment of a like 
 nature is performed by employing a solution of urea in 
 alcohol, in which the crystallisation is quite different, the 
 plate being quickly covered with bundles of fibres which 
 are no longer at right angles to the stem from which 
 they spring, but take ail kinds of different directions. 
 
THE BOOK OF THE LANTERN. 
 
 197 
 
 These experiments are of great use in demonstrating 
 the gradual crystallisation of the various mineral sub- 
 stances of which the crust of the earth is composed. A 
 yery beautiful experiment, showing the structure of ice, 
 has been devised by Professor Tyndall. I cannot do 
 better than describe the manner of performing it in his 
 own words : " Take a slab of lake ice and place it in the 
 path of a concentrated sunbeam. Watch the track of the 
 beam through the ice. Part of the beam is stopped, part 
 of it goes through ; the former produces internal lique- 
 faction, the latter has no effect whatever upon the ice. 
 Bat the liquefaction is not uniformly diffused. From 
 separate spots of the ice little shining points are seen to 
 sparkle forth. Every one of those points is surrounded by 
 a beautiful liquid flower with six petals. 
 
 " Ice and water are so optically alike that unless the light 
 fall properly upon these flowers, you cannot see them. 
 But what is the central spot ? A vacuum. Ice swims on 
 water because, bulk for bulk, it is lighter than water ; so 
 that when ice is melted it shrinks in size. Can the liquid 
 flowers then occupy the whole space of the ice melted ? 
 Plainly no. A little empty space is formed with the 
 flowers, and this space, or rather its surface, shines in the 
 sun with the lustre of burnished silver. 
 
 " In all cases the flowers are formed parallel to the sur- 
 face of freezing. They are formed when the sun shines 
 upon the ice of every lake; sometimes in myriads, and so 
 small as to require a magnifying glass to see them. They 
 are always attainable, but their beauty is often marred by 
 internal defects of the ice. Even one portion, of the same 
 
198 
 
 THE BOOK OF THE LANTERN. 
 
 piece of ice may show them exquisitely, while a second 
 portion shows them imperfectly. 
 
 " Here we have a reversal of the process of crystallisation. 
 The searching solar beam is delicate enough to take the 
 molecules down without deranging the order of their archi- 
 tecture. Try the experiment for yourself with a pocket- 
 lens on a sunny day. You will not find the flowers con- 
 fused ; they all lie parallel to the surface of freezing. In 
 this exquisite way every bit of the ice over which our 
 skaters glide in winter is put together." 
 
 One of the most interesting chemical operations to 
 witness is the development of a photograph, — and even 
 experienced workers will say that they never tire of 
 watching the gradual unfolding of the wonderful image. 
 Those who have never before had the opportunity of watching 
 the effect of the developing fluid on the blank plate, are 
 delighted when first the operation is brought under their 
 notice. It is certainly an experiment which never fails to 
 interest an audience, when properly performed, as it can be, 
 in the optical lantern. But the operator must not be 
 a novice in photography, or he will probably fail, for the 
 experiment requires experience, and great care in all 
 its stages. 
 
 A gelatine bromide plate, such as is ordinarily used 
 for negative work, is of no use whatever here, for the 
 film is too opaque for the purpose. A gelatine chloride plate 
 (such as that described on page 133) is the right thing to 
 employ. If we compare a bromide and a chloride plate side 
 by side in the dark room, we shall soon see that there is 
 little difficulty in distinguishing the one from the other. In 
 
THE BOOK OF THE LANTERN. 
 
 199 
 
 the first case, the film is so thick that we can see nothing 
 throngh it, but in the case of the chloride plate the flame of 
 the red lamp can easily be seen through the glass ; indeed, 
 upon first using such plates, photographers are apt to 
 wonder whether so thin a film can ever yield a picture. As 
 a matter of fact, the film is as thick as that upon a bromide 
 plate, only the emulsion of which it is composed is of a 
 far more transparent quality. 
 
 Having then a chloride plate at hand, and having if ne- 
 cessary cut it down to a size which will enable it to slip 
 with ease into a chemical tank, the course of operations 
 will be as follows: — 1, Exposure; 2, development; and 
 3 j fixation. 
 
 Provide a good negative (if it be a portrait of some one . 
 well known to the spectators, so much the better), and place 
 it in a printing frame, with the chloride plate against it, 
 film to film. Expose to the light of an inch of magnesium 
 wire held two feet away from the printing frame, or to the 
 rays of the lime light for about ten seconds. Now place 
 the little tank on the stage of the lantern, and against the 
 inner side of it, that is, next the light place a sheet 
 of ruby glass. The effect upon the screen will now be 
 simply that of a blank red disc. The exposed plate may 
 now be taken from the printing frame and placed in the 
 tank. Take good care that it is placed there upside down, 
 so that the image when developed will appear the right way 
 up. The developing fluid, ferrous oxalate (see page 121), 
 may now be mixed. This should be at hand in two solu- 
 tions, so that by mixing the one with the other the de- 
 veloper is ready without any delay. As it is poured into 
 
200 
 
 THE BOOK OF THE LANTERN. 
 
 the tank, the surface of the fluid will appear as a descending 
 line across the sheet. The strength of the developer should 
 not be so great as for ordinary development, by which I 
 mean that the proportion of iron can be conveniently 
 reduced so as to render development less sudden than it 
 generally is with chloride plates. When once the developer 
 has been poured into the tank, the red glass can be with- 
 drawn, for the ferrous oxalate developer is red enough in 
 itself to form a protection to the plate from the light. 
 Presently the image will begin to appear, and will gradually 
 gain in strength. When it is fully developed, as it will be 
 in about two minutes, the plate can be removed, washed, 
 and placed once more in the lantern in a tank of fixing solu- 
 tion. Here it will gradually get clear, as the unaltered 
 chloride is acted upon by the hyposulphite of soda solution. 
 
 To perform this interesting experiment in the most per- 
 fect manner, a special form of tank may be employed. It 
 should have a tap at its lower part, to act as a waste pipe. 
 With this arrangement the chloride plate need not be 
 removed from the tank at any stage of the process. When 
 development is complete, the ferrous oxalate can be drawn 
 off ; then water can be poured in, to be immediately drawn 
 off and replaced by the hypo solution. 
 
 The chloride plate employed can be put into the printing 
 frame by gaslight, provided that the operation be performed 
 with ordinary despatch. It should be noted, too, that these 
 plates, or at least some brands of them, rapidly deteriorate. 
 But the careful operator will try the experiment in private 
 before he ventures before the public, and will take care that 
 his plates are above suspicion. 
 
THE BOOK OF THE LANTERN. 
 
 201 
 
 Magnetic experiments are always attractive, and can be 
 well shown with the lantern, for they gain greatly by the 
 magnification possible with that instrument. Fig. 52 shows 
 a simple form of slide which can be manufactured without 
 much trouble ; it consists of a bar of soft iron, bent as 
 shown, and pointed at its ends. These ends or poles are 
 brought to within half an inch of each other. Two 
 wooden or cardboard reels, wound with a quantity of silk 
 covered copper wire, complete the arrangement. The 
 battery already recommended can be used with this mag- 
 netic slide. Here are a few experiments possible with the 
 
 Fig. 52. 
 
 contrivance. Drop upon the poles some iron filings, and 
 show that they are not attracted until the battery connec- 
 tion is made, for then and only then has the iron magnetic 
 properties conferred upon it. Drop a number of small 
 French nails, technically known as pins, upon the poles, 
 when they will meet and assume curious forms, until the 
 current is broken, when they will fall upward, as it will 
 appear. A tiny disc of iron attached to the end of a silk 
 thread and hung between the poles will take up a rigid 
 position directly the battery connection is made, a similar 
 
202 
 
 THE BOOK OF THE LANTERN. 
 
 one of bismuth assuming the opposite direction under the 
 same conditions. This last experiment is to show the 
 difference between a magnetic and dia-magnetic body. 
 
 But the most beautiful magnetic experiments are only- 
 possible with a vertical attachment fitted to the lantern. 
 Obtain a couple of flat bar magnets two inches in length. 
 Place one of these in the centre of the horizontal stage, and 
 focus sharply on the screen. The appearance is that of a 
 thick black bar. "Now sift through a muslin bag some iron 
 filings, so that the screen appears covered with black spots. 
 Tap the stage with the finger nail, so as to disturb the 
 particles of iron, and they will be seen to gather round the 
 poles of the little magnet, and to form the beautiful magnetic 
 curves. A still more striking experiment may be per- 
 formed with two magnets so placed that their poles of 
 opposite names, — N". and S., — face one another, while they 
 are at the same time about one inch apart. Now scatter 
 the filings as before, and the effect of the graceful curves 
 embracing one another between the two poles is simply 
 magnificent. Remove the magnets, wipe the filings from 
 the stage, and once more arrange the bars in the same 
 position, but with poles of the same name facing one 
 another. When the filings are now scattered over the 
 magnets, a great contrast to the last experiment is apparent. 
 Where just now all was harmony, there is visible antago- 
 nism. " Poles of opposite name attract one another, and of 
 the same name repel one another." And this repulsion is 
 most beautifully shown. The curves no longer embrace 
 one another, but meet and turn back upon themselves, 
 forming a line of confusion where the meeting takes 
 
THE BOOK OF THE LANTERN. 
 
 203 
 
 place. The experiments can be varied by altering the 
 position of the magnets, or by nsing knitting needles which 
 have been jnst before magnetised at the lecture table. It 
 will be noticed that these curve experiments require no 
 battery power. They are performed with what are known 
 as permanent magnets, in contradistinction to the electro 
 magnet used with the special form of slide shown at 
 fig. 52. 
 
 In describing some of the experiments possible with the 
 optical lantern, I have purposely refrained from detailing 
 any of the splendid effects due to polarised light — for these 
 have been already dealt with by my friend Mr. Lewis 
 Wright, in a manner which it would be impossible to 
 improve upon. 1 
 
 1 " Light : a Course of Experimental Optics, chiefly with the 
 Lantern.' ' Macmillan & Co. 
 
CHAPTER XIY. 
 
 THE LANTERN AS AN AID TO PHOTOGRAPHY. 
 
 HEN a photographic aspirant first enters npon the 
 practice of what nsed to be known as the " black 
 art," bnt which now, thanks to the cleanliness of 
 dry plate work, no longer merits that stigma, his friends 
 and relatives all look anxiously for some tangible results 
 from his mysterious operations. To them a negative, 
 albeit it may show lovely gradations of tone, and 
 beauties of detail, which a master's eye would revel 
 in, is negative in a far wider sense than its producer 
 would be inclined to allow. A production in which 
 bright skies and white skins are black as night, is a 
 thing which cannot be understood or tolerated, and until a 
 print of that negative is produced, — and sometimes alas ! 
 even then, — the domestic critics are inclined to consider the 
 amateur worker a fraud. The painstaking photographer, 
 after he has succeeded in obtaining a few negatives, will be 
 anxious on this account, if not for his own satisfaction, to 
 print some positives from them. These will afterwards be 
 
TITE BOOK OP THE LANTERN. 
 
 205 
 
 mounted in an album, and much pleasure will doubtless be 
 derived from them. They may possibly not be grand 
 specimens of solar work, but they will serve to remind the 
 author of many a pleasant ramble, and many little incidents 
 of places visited and people met with, which otherwise 
 might have passed into oblivion. He will be able " to fight 
 his battles o'er again/' as he tells his friends of difficulties 
 encountered by the way. But at the best this means a 
 great deal of work, and. work, too, which to a great extent 
 is mechanical, and therefore tedious. The printing, toning 
 and fixing of a batch of prints is no light matter to an ama- 
 teur, who has generally to do everything for himself. Some 
 prints are sure to get over-exposed, others suffer from the 
 opposite failing, and even if all goes well in the preliminary 
 operation of exposure, there is that terrible toning bath to 
 come. This bath sometimes, for some obscure reason, will 
 refuse to give the desired colour, and our batch of prints, 
 instead of being " joys for ever," turn out to be sandy- 
 looking, bilious objects, which we are afraid to show to 
 anybody. 
 
 What if some magician were to appear suddenly at the 
 elbow of the disgusted worker, and tell him that there was 
 a way of producing positives from those negatives without 
 all this trouble ? That such positives could be shown en- 
 larged to an almost indefinite extent, and that pictures five, 
 ten, or fifteen feet in diameter could be shown in perfection, 
 the original negative from which they are taken measuring 
 only three and a quarter inches. There is no need for any 
 magician, for the thing can be achieved, not easily, for the 
 work, like most photographic manipulations, requires a 
 
20G THE BOOK OF THE LANTERN. 
 
 great deal of patience and practice before success is 
 attained. The requisites are good photographic transpa- 
 rencies on glass, and a good optical lantern wherewith to 
 exhibit them. 
 
 The lantern method of showing photographs has the ob- 
 vious advantage that a large number can at the same time 
 view the same picture under the best conditions. They can 
 exchange opinions as to its merits, and can point out little 
 bits of detail which would be almost invisible in a paper 
 print from the original small negative. A great many 
 amateurs, too, take only small negatives. They do not care 
 to be burdened in their rambles with a large camera, 
 which, with its inevitable dark slides or changing box, 
 forms a very heavy travelling companion. Many, there- 
 fore, are wise enough to content themselves with either a 
 quarter-plate apparatus, or one which gives pictures mea- 
 suring 5 by 4 inches. Prints from these small negatives 
 are rather insignificant when mounted in an album, but 
 such negatives are just what are required for lantern trans- 
 parency making ; so that the tourist with his little camera 
 is, with the help of the lantern, placed on the same footing 
 as the toiler with large and heavy apparatus. He can in- 
 crease the size of his pictures, or rather the images of such 
 pictures, to any reasonable extent. I know of an amateur 
 photographer who spent three months on a Mediterranean 
 tour. He took with him a quarter-plate camera, and its 
 accessories, together with a stock of gelatine plates. He 
 brought back with him about one hundred and fifty capital 
 negatives, which were taken in Algeria, Tunis, Malta, 
 Sicily, and Southern Italy. On his arrival in England 
 
THE BOOK OF THE LANTERN. 
 
 207 
 
 these were all printed as lantern transparencies, and he is 
 now able to entertain his friends with an acconnt of his 
 wanderings, and to illustrate his remarks in a very pleasant 
 and novel manner. If the same negatives had been merely 
 printed on paper in the usual manner, and shown in an 
 album, they would, by reason of their smallness, have met 
 with but scant appreciation. 
 
 I may instance another way in which the lantern can be 
 utilised without the necessity of taking original negatives. 
 Most travellers abroad collect photographs of any place they 
 may visit, and an enormous trade is now done in such 
 pictures. These are brought home in due course, mounted 
 in an album, and too often, alas ! gradually fade into sickly 
 yellow ghosts of their former selves. Now, if these pictures 
 were copied by a small quarter-plate camera, the negatives 
 thus obtained could in their turn furnish positives on glass 
 for use in the lantern. Transparencies so produced are 
 never, it is true, so good as those from original negatives, 
 for the texture and the gloss of the paper prints will gene- 
 rally to some extent show themselves in the reproduced 
 negative, but still it is wonderful what good results can be 
 obtained in this way. Indeed, I may say that it requires a 
 critical eye to detect that a second negative has been em- 
 ployed. I have already detailed the best method of pro- 
 ducing these negatives from paper prints, and have given 
 some useful hints by which the disadvantages to which they 
 are subject can be reduced to a minimum (see page 121). 
 
 Paper prints naturally remind one of those portrait 
 albums which are found in every house. Why should not 
 these pictures also be adapted to the lantern? What a 
 
208 
 
 THE BOOK OF THE LANTEKtf. 
 
 fund of interest and amusement could be obtained from 
 an exhibition of life-sized pictures of friends and acquaint- 
 ances well known to the family circle ! There is really 
 no great difficulty in obtaining such pictures when the first 
 principles are understood; and when practice has given 
 experience, negatives from prints can be produced with a 
 rapidity and certainty to which the most experienced land- 
 scape photographer is a stranger. 
 
 Nor must the young folks be forgotten. Although the 
 " man swallowing rats " and the other monstrosities, known 
 in the trade as " comic slips," still have an attraction to the 
 eye of youth, surely we can manage by the means now 
 easily within reach, to place before the youngsters some- 
 thing better worth looking at. The quaintly picturesque 
 little youths and damsels drawn by Kate Greenaway would 
 have additional charm for their living playfellows if shown 
 life-sized on a screen ; and nursery legends, as interpreted 
 by Caldecott's clever pencil, would acquire a new interest if 
 shown in the same fashion. Perhaps as amateur photo- 
 graphy increases its number of workers, as it is rapidly 
 doing, artists may find it convenient to draw subjects 
 specially for reproduction as lantern transparencies. 
 
 There is one feature in this particular class of photo- 
 graphic work which I have not yet dwelt upon, and that 
 is, the possibility of producing these transparencies inde- 
 pendently of daylight. So long as the spring, summer, and 
 autumn days are upon us, the possessor of a camera finds 
 much other work to employ his time. His labours are 
 mostly in the open field, adding to his stock of negatives, 
 and he looks forward with regret to the many dark hours 
 
THE BOOK OF THE LANTERN. 
 
 209 
 
 which winter must bring, in which such work is impossible. 
 But now is his time for lantern preparation. The negatives 
 are looked up and sorted out, and by means of a gas flame 
 or paraffin lamp he can print off transparencies more 
 quickly than even on a favourable day he could produce 
 paper prints. There is no tedious toning or extended 
 washing necessary, and therefore the work does not entail 
 half the trouble that he is accustomed to in ordinary print- 
 ing. In addition to these advantages there is one other. 
 A transparency on glass is far finer in effect than any 
 paper print, for the reason that the picture is absolutely 
 without texture. Magnify a paper print and the texture 
 of the paper becomes at once evident; treat a good 
 glass positive in the same way and its beauty is only 
 increased. 
 
 Lastly, the possessor of a lantern has another field of 
 work in which it can be usefully and efficiently employed, 
 — namely, in making enlargements. Not the evanescent 
 and fleeting images already described, but permanent en- 
 largements of a quarter-plate negative, which is sufficiently 
 rich in detail and interest to warrant its production in an 
 enlarged form. By means of an oil lantern, and a sheet 
 of the excellent gelatino-bromide paper now to be pur- 
 chased, an enlarged positive from a small negative is easy 
 to produce. And here, again, the work is quite indepen- 
 dent of the fickle sun, and can be accomplished in any 
 room not specially set apart for the purpose. 
 
 I have by no means exhausted the list of services 
 which a simple form of optical lantern is able to render, 
 but I have enumerated several which will serve my pur- 
 
 P 
 
210 
 
 THE BOOK OF THE LANTERN. 
 
 pose in pointing out its extreme utility. In a subsequent 
 chapter on enlarging I dwell in detail upon the various 
 operations necessary, and illustrate them by diagrams, 
 so that readers may acquire a practical knowledge of the 
 necessary manipulations. 
 
CHAPTER XV. 
 
 THE ART OF MAKING PHOTO-MICROGRAPHS. 
 
 PHOTO-MICROGRAPH is the picture of a 
 microscopic preparation, as seen by the eye 
 when enlarged by means of the microscope; 
 its converse, being a much-reduced image of an object 
 photographed on glass, which is called a micro-photograph, 
 and which can only be seen when placed in the microscope. 
 This latter, however, is a mere curiosity, and, although 
 it excites some wonder when looked at, has no educational 
 or scientific value, except perhaps as a proof of the fine 
 structure of a photographic film. A photo-micrograph, on 
 the other hand, affords a valuable means of displaying to a 
 large audience the delicate structure of various organisms, 
 both animal and vegetable ; besides which that of coal and 
 other minerals can be well exhibited. Lantern micro- 
 scopes, — some of very beautiful construction,— have been 
 brought forward from time to time, and one of them, at 
 least, I shall refer to in a subsequent chapter. 
 
 But although lantern microscopes may give very fine 
 results, it is an indisputable fact that the amount of light 
 which is able to get through the tiny aperture of a high- 
 power objective, is small. And when this small amount 
 
 v 2 
 
212 
 
 THE BOOK OP THE LANTERN. 
 
 has to be spread over a screen of even moderate propor- 
 tions, the illumination of the whole is so insufficient that 
 although near observers are able to note that the disc is 
 covered with a network of exquisite detail, those who are 
 placed a few yards away cannot distinguish anything of the 
 kind. If this is the case with those whose sight is perfect, 
 how much more true it must be of the large number of 
 persons who are less favourably endowed. Probably the 
 difficulty may be remedied at an early date by the use of 
 the electric light, which is far more brilliant than the best 
 limelight possible, and I know that experiments are 
 being carried on in this direction ! In the meantime, we 
 must look for other means of projecting the image of 
 microscopic objects on a screen if we require such illus- 
 trations for a large number of spectators. I recommend 
 the employment of photo-micrographs of the size of the 
 ordinary lantern-slide, viz., 3^ x 3^ in. as the best way out 
 of the difficulty. I am, of course, aware that a photo- 
 graph of an object is not in many cases so good as the 
 object itself. While this is true, it is also true that there 
 are a great many preparations which cannot be satisfactorily 
 shown by any kind of projecting apparatus, but they can 
 be made to yield photographs which can be exhibited by 
 the optical lantern. There are many different ways 
 of producing photo-micrographs. Some workers use the 
 most complicated apparatus, whilst others seem to obtain as 
 good results with rough home-made appliances. But so it 
 is in every branch of science. Somebody wittily divided 
 microscopic workers into two different species. He dubbed 
 the first of these " Brass and Glass," and the second 
 "Bug and Slug." The first are the possessors of the 
 
THE BOOK OF THE LANTERN, 
 
 213 
 
 magnificent microscopes with all kinds of movements and 
 expensive attachments, and who toy with their instruments 
 rather than work with them. The second class are the 
 hard workers, who will be content so long as they posse ss 
 one or two good powers, and have anything in the shape 
 of a stand to hold them in position. They will accomplish 
 far more real work with a simple magnify ing-glass than one 
 of the " Brass and Glass " fraternity with his gorgeous 
 array of instruments. 
 
 One of the most simple methods of obtaining a photo- 
 graph from a microscopic object is to use a little camera, — a 
 cardboard box with a hole at the bottom to fit over the 
 microscope tube is sufficient, — placed above the microscope 
 as it stands upright on a table. To simplify matters, the 
 eyepiece of the microscope should be removed, — a method of 
 procedure which I recommend in all cases. The upper part 
 of the cardboard box should be furnished with a lid on a 
 hinge, and should have a curtain of black velvet all round it, 
 to prevent any access of light. On its inner sides, half an inch 
 below the lid opening, should be glued four little pieces of 
 wood to support the focussing screen ; the same support 
 serving later on to hold the sensitive gelatine -plate in posi- 
 tion. Now let us go through the required operations. The 
 image is focussed by daylight, or lamplight, as the case 
 may be. The focussing glass is then removed, and while 
 the room is darkened the sensitive plate is inserted in its 
 place, the lid of the box shut down, and all is ready for ex- 
 posure. The time of exposure is of course a matter depend- 
 ing upon a host of circumstances to which we need not here 
 refer. The exposure having been made, the plate is de- 
 veloped in the usual manner. 
 
2H 
 
 THE BOOK OF THE LANTERN. 
 
 Another plan is to bring down the microscope to the 
 horizontal position, — and most microscopes allow of this 
 being done, — and to pnsh the end of its tube into the flange 
 opening of an ordinary photographic camera, with the lens 
 of the latter removed. Bnt both these methods have 
 a disadvantage, among many other drawbacks, which 
 will at once disappoint the operator. The image afforded is 
 so small. The tube of the microscope gets in the way, so 
 to speak, and a large portion of that image is cnt off. This 
 can be remedied by an arrangement of the apparatus which 
 I am now about to describe, and by which I have taken a 
 number of photographs which leave little to be desired in 
 point of excellence, while the necessary manipulations are 
 carried forward with that ease and nicety which go far to- 
 wards the production of first-class results. 
 
 Let it be at once pointed out, in spite of the opinions of 
 our " Brass and Glass " friends, that an expensive instru- 
 ment is not required for this work. (Indeed, I will presently 
 point out how it is possible to obtain capital photo-micro- 
 graphs without any microscope at all, although the essen- 
 tial part of that instrument, — the objective, — must be 
 employed.) What is wanted is a good firm stand, and a 
 fine adjustment, and even this is not very necessary unless 
 high powers are employed. But the majority of readers 
 will look for some ready means of photographing objects of a 
 popular character. The proboscis of a blowfly, the industrious 
 flea (or bee is it ?), section of the echinus spine, and so on ; 
 such things as can be readily photographed with the " inch" 
 objective. And to readers who are content with such as 
 these I chiefly direct my remarks, leaving them to study 
 the excellent treatises and articles upon the subject of 
 
THE BOOK OF THE LANTERN. 
 
 215 
 
 photo-micrography, which have been published, when they 
 feel themselves capable of 
 higher nights in this most 
 interesting domain of 
 scientific research. 
 
 The microscope which 
 I use is of a very ordinary 
 pattern, as may be noticed 
 in the diagram (fig. 53) ; 
 but three little alterations 
 in it make it very con- 
 venient for photographic 
 work. In the front leg 
 of the claw-shaped stand 
 a 3-16ths inch hole has 
 been bored, so that the 
 instrument can by means 
 of a screw be rigidly 
 fixed upon a base board. 
 The next alteration is in 
 the length of the tube. 
 Originally seven inches 
 long, I have had it 
 separated at nearly the 
 centre, so that it can be 
 reduced to three inches ; 
 but an inner tube over 
 which the outer one 
 tightly fits, allows me to 
 use the microscope for ordinary purposes with a tube of 
 
216 
 
 THE BOOK OF THE LANTERN. 
 
 normal length. The third modification which I have intro- 
 duced, is a groove cut in the milled head of the fine adjust- 
 ment screw, the purpose of which we shall presently see. 
 For photographic work, the mirror is thrown out of gear, 
 as indicated in the diagram, for it is not required. 
 
 Referring once more to this diagram, tt is the table on 
 which the whole arrangement rests, and it is best to have 
 a table for the purpose, or at any rate a level base board, 
 upon which all necessary fixtures can be made ; c is a 
 camera which should open out to great extent (most 
 modern cameras are made to do so, so as to give the 
 photographer the benefit of using long-focus lenses) ; 
 m is the microscope, s the stage, p the mirror thrown 
 back out of use, n the coarse adjustment, and k the fine 
 adjustment. We can now see the advantage of providing 
 this milled head of the fine adjustment screw with a 
 groove. In this groove is p]aced a silk cord, which 
 works in a corresponding groove in the little wheel 
 which is fixed on the end of the focussing rod o o. By 
 means of the knob d at the other end of this rod, the 
 operator is able to work the fine adjustment to a nicety, — 
 while he is far away from the microscope, — examining 
 the image on the ground-glass screen of the camera. 
 
 A word about this screen will not be amiss. Ordinary 
 ground-glass will not do for this class of work, for it is 
 far too coarse. It should therefore be replaced by a 
 focussing screen prepared as follows : — Obtain a sensitive 
 gelatine plate, such as is used for negative work, expose 
 it to the light of a gas flame for a second, and then pro- 
 ceed to develop it. Develop until it is uniformly 
 
THE BOOK OP THE LANTERN. 
 
 217 
 
 darkened to a small extent, fix and wash- in the usual 
 manner, and then bleach it in a solution of mercuric 
 chloride. The result will be a plate covered with an 
 exquisitely fine translucent surface, upon which the 
 finest details will be visible. The exact amount of 
 exposure and development to secure this end may not 
 be at first hit upon, but one or two trials will be sure to 
 end in a satisfactory result. Some workers prefer to use 
 a plain glass upon which fine lines have been ruled 
 with a writing diamond. In any case the worker will 
 find the advantage of supplementing his eyesight, how- 
 ever good, by a focussing glass. In this way a far sharper 
 focus is obtainable than by the unaided eye. 
 
 To describe the rest of the diagram, let me point out 
 that / is an ordinary microscopic paraffin lamp, furnished 
 with a reflector f, and that h is a condensing lens, having 
 attached to it a diaphragm-plate, e. 
 
 Mr. T. Charters White, M.R.C.S., has published a 
 method by which photo-micrographs can be produced 
 without the aid of either a camera or a microscope, which 
 is very creditable to his ingenuity. I had recently the 
 pleasure of hearing him describe the instrument, while 
 he practically demonstrated how effectually it would 
 work. The apparatus was home - made, and such as 
 could be produced by any one with the minimum of out- 
 side help, although there are many accustomed to the use 
 of tools who could easily make it without any help at all. 
 I appcmd a diagram which shows the various parts of this 
 simple contrivance (see fig. 54). 
 
 It consists in a lidless box sufficiently large to con- 
 
218 
 
 THE BOOK OF THE LANTERN. 
 
 tain an ordinary microscopic lamp, an objective which 
 screws into one end of the box, — and a movable stage 
 
 Fig. 54. 
 
 to hold the object, having a screw attachment, so that 
 it can be moved to and from the objective in order 
 that the image may be sharply focussed upon a plate 
 held in a frame outside. This frame is fixed to a 
 grooved board, which can be moved in and out of the base 
 board, and this movement determines the distance of the 
 image projected from the Jens, and therefore the size of 
 that image. The apparatus may indeed be compared to 
 an optical lantern in its arrangements, except that the 
 condensing lens (an ordinary one on a stand such as is 
 used for microscopic work) is contained within the box, 
 and that the object to be projected is on a special form of 
 movable stage, as above mentioned. This stage, or fine 
 adjustment, consists of two parallel and horizontal bars, 
 with a fine screw of the same length laid between them, 
 and which works in a threaded orifice in the lower part of 
 the stage. The end of this screw nearest the light is 
 
THE BOOK OF THE LANTERN. 
 
 219 
 
 crowned with a grooved wheel, which is geared by a piece 
 of cord to another similar wheel at the end of a focussing- 
 rod, which is brought within easy reach of the plate- 
 carrier outside the box. 
 
 These various arrangements will be rendered clearer by 
 reference to the diagram, where 0 is the objective, S the 
 stage, F the focussing-rod, L the lamp, C the condenser, 
 and A the frame holding the gelatine plate, or the 
 focussing-glass, as the case may be, for one takes the 
 place of the other. And let me say, in passing, that this 
 method of withdrawing one glass so that the other can 
 take its exact place, is the best that could be adopted, for 
 the merest fraction of difference in register would be 
 perceptible in photo-micrographic work, while it might 
 rimain undiscovered in negative taking of the ordinary 
 kind. 
 
 Mr. White's apparatus was, at the time I saw it, fitted 
 with a 1-inch objective; but he told me that he had 
 used higher powers with it. It certainly is capable of 
 very fine work, as was proved by an album full of speci- 
 mens which he exhibited. His focussing-screen was a 
 plain glass, ruled with lines by a - diamond, and he 
 employed a focussing eye-piece. But it is evident that, 
 with this method of working, the operator could employ 
 an opaque screen, such as a piece of opal glass, for the 
 room in which the work is carried on takes the place of 
 the camera, and he is practically within it, and can 
 look upon the side of the screen which is next the 
 light. By means of a scale upon the sliding-board which 
 carries the gelatine plate, it is easy to note, without actual 
 
220 
 
 THE BOOK OF THE LANTERN. 
 
 measurement, the amount of magnification of the image. 
 And this magnification can be carried to any reasonable 
 extent, for the worker is not limited, as he would be if 
 using a camera, by the length to which that camera can 
 be extended. 
 
 But perhaps the simplest arrangement of all is that 
 recently introduced by Messrs. Mawson & Swan, and 
 which is shown at fig. 55. A is a light metal disc, which 
 
 Fig. 55. 
 
 can be screwed on the camera front in place of the ordinary 
 lens. The opening in its centre is furnished with the 
 regulation microscopic screw, so that any ordinary micro- 
 scopic objective can be readily fixed to it. Upon two 
 horizontal bars, projecting from this metal disc, there 
 slides another similar disc B, also with an opening in the 
 centre. This second disc has fitted to it a pair of small 
 spring clips for the reception of the microscopic slide 
 which it is desired to photograph. Focussing is effected 
 by sliding the disc B to and fro in front of the objective 
 
THE BOOK OF THE LANTERN. 
 
 221 
 
 on A. It will be readily seen that the apparatus may be 
 rendered more effective by the attachment of a screw, or 
 fine adjustment for more accurate focussing ; but with the 
 lower powers this would not be needed. It is an addition, 
 however, which the makers will supply when required. 
 
 All the objectives made by Messrs. Swift, as well 
 as those by a few other makers, are corrected for 
 photography, but in those of older date the visual focus 
 does not agree with the chemical focus. As a rule, no 
 difficulty will be found with the higher powers, and with 
 the others a few trials will soon show what allowance in 
 focussing must be made. As a rough guide to what must 
 be done to correct this fault, which is rendered evident 
 by a sharply -focussed image appearing blurred in the 
 negative, proceed as follows : First focus the image as 
 sharply as possible, and then cause the objective to 
 approach the object until the latter seems to be sur- 
 rounded by a reddish light; now take the photograph 
 and it will be sharply defined, although the image did not 
 look so on the focussing screen. 
 
 The ferrous-oxalate method of development, described on 
 a former page, is very suitable for negatives taken for 
 photo-micrographs. These negatives are then made to 
 furnish lantern slides in the manner detailed in a former 
 chapter. 
 
CHAPTER XVI. 
 
 mm 
 
 ENLARGING PHOTOGRAPHS WITH THE LANTERN. 
 
 HE amateur who works with a quarter plate 
 camera will often congratulate himself upon 
 the slight burden which it entails, even when 
 several double backs and spare plates accompany 
 it. But he will also regret that the little pictures 
 which it yields, — measuring only 3 by 4 inches when 
 trimmed and finished, — are, after all his trouble, so 
 very insignificant-looking. He may possibly have availed 
 himself of the instructions already given for the produc- 
 tion of lantern slides from such small negatives, and thus 
 ascertained that his pictures are full of detail, and will 
 bear enlargement. But lantern images are fleeting things, 
 — dissolving views, in truth, — and he would fain endeavour 
 to find some more permanent way of increasing the size 
 of his pictures. Thanks to the w r onderful photographic 
 revolution achieved by gelatine emulsion, this can be done 
 without very much trouble or difficulty. 
 
 In using the lantern for exhibition purposes we employ 
 
THE BOOK OF THE LANTERN. 
 
 223 
 
 for slides transparent positives on glass, and it stands to 
 reason that, if the sheet or surface upon which the image 
 is thrown were, by chemical means, to be made sensitive 
 to light, we should obtain much the same result that we 
 get by means of our camera, — a negative image, which can 
 be rendered visible by development. If, on the other hand, 
 we employ one of our little negatives as a lantern slide, 
 we can produce from it a positive. Such is the theory 
 which we will now endeavour to reduce to practice. 
 
 The lantern employed can be of the ordinary kind used 
 for projection, but in this case, where the condenser only 
 measures 4 inches, it is obvious that a negative measuring 
 less than that size will be the only one available. The 
 operator will therefore be better off with a lantern made 
 specially for enlarging purposes, the condenser of which 
 must be at least 5 inches in diameter to accommodate a 
 quarter-plate negative. It might, in many cases, be prac- 
 ticable to fit the ordinary lantern with a condenser of that 
 size when it is proposed to use it for enlarging purposes. 
 Whatever be the arrangement, there must be in front of 
 the lens of the lantern a flat board upon which the image 
 can be projected, and which will serve as a support for the 
 sensitive surface at a later stage of the operations. 
 
 A convenient form of upright easel is shown at fig. 56. It 
 can be moved backwards and forwards between a couple of 
 laths nailed on the floor, while the enlarging lantern 
 remains stationary. A light-tight box above it contains a 
 roll of sensitive paper, which can be pulled down and cut 
 off in lengths as required. This easel has a hinged frame, 
 so that when a sufficient length of the paper is drawn down 
 
224 
 
 THE BOOK OF THE LANTERN. 
 
 over the face of the easel, which serves as a focussing 
 board, the frame shuts it in and is clamped. In this way 
 
 Fig. 56. 
 
 the paper is held tight without the necessity of using pins, 
 or other loose fastenings. 
 
 Fig. 57 shows a larger view of this box, with its supply 
 of sensitive material. But the beginner would no doubt, 
 first of all, experiment with a simple board, and one 
 measuring 12 inches by 10 inches would be ample. 
 
 The sensitive surface to be employed when a direct 
 positive is required, is paper specially prepared with a 
 
THE BOOK OF THE LANTERN. 
 
 225 
 
 coating of gelatino-bromide of silver emulsion. If an 
 enlarged negative is desired, either an ordinary gelatine 
 (glass) plate of the required size may be employed, or a 
 paper negative can be made in the manner to be presently 
 described. Messrs. Morgan & Kidd, of Richmond, were 
 
 Fig. 57. 
 
 the first to introduce " argentic gelatino-bromide paper," 
 and therefore the circumstance should be noted to their 
 credit. It can now be obtained from most other dealers, 
 and its manufacture is so well understood that it will be 
 found generally reliable. It can, of course, be used for 
 contact printing as well as for enlarging purposes. But 
 perhaps the sanguine amateur may prefer to manufacture 
 it for himself, and there is no reason why he should not 
 succeed in doing so, if he is already master of the secret of 
 making an emulsion which neither fogs nor frills. Here 
 is a necessarily brief outline of the method of going 
 to work : — 
 
 Procure some good plain Saxe paper. Having made 
 and fiHered your emulsion, allow it to set to a jelly in a 
 
 Q 
 
226 
 
 THE BOOK OF THE LANTERN. 
 
 dish. With a good stiff hog-hair stencil-brush break up 
 the cold jelly, and rub it vigorously over the paper, just as 
 you would break up cold starch jelly in mounting prints. 
 Now drag the paper slowly over an earthenware foot- 
 warmer, which has been duly charged with boiling water. 
 The heat will cause the little specks of jelly on the paper 
 to melt and mingle, and the whole will present a smooth 
 surface. The paper must now be hung up to dry, or it 
 may be used at once. I need hardly say that all these 
 operations must be conducted by non-actinic light. The 
 majority of workers, however, will prefer to buy their 
 argentic paper ready-made, and, by doing so, save them- 
 selves possibly much vexatious disappointment. 
 
 Any room will serve for the purpose of making an 
 enlargement ; but it is preferable to conduct the work 
 at night, because then is saved the trouble of darkening 
 a room so that it is really fit for photographic opera- 
 tions, by no means an easy matter. Having a dark 
 room, the further requirements are a lantern, a screen 
 as aforesaid in front of it, with a sheet of white paper 
 pasted over its surface, a good red lamp, a developing 
 dish, the necessary chemicals, and, lastly, plenty of water 
 and a pail for waste solutions. If the room has in 
 it a tap and sink, so much the better. The negative 
 (which should be a good one, or it will not be worth 
 enlarging) is placed in the lantern like an ordinary slide, 
 taking care that the film side is turned towards the screen, 
 and away from the light. Now carefully focus its image 
 on the white board. Having placed lantern and screen at 
 such a distance from one another that the image is of the 
 
THE BOOK OF THE LANTERN. 
 
 227 
 
 required dimensions, and having seen that that image is 
 as sharply focnssed as possible, it will be as well if a slip 
 of sensitive paper, say, 1 inch wide, is first of all exposed 
 as a pilot. 
 
 In the hnrry and bustle incidental to, if not inseparable 
 from, every-day life, we all have a tendency to work too 
 much by rnle of thumb, and it must be confessed that rule 
 of thumb often turns out very good results. But, in spite 
 of this, and of the old adage to the effect that an ounce of 
 practice is worth a pound of theory, we cannot afford to 
 give theory the go-by entirely. Theory is a useful servant, 
 but a bad master, for those patient, plodding creatures who 
 think of nothing else seldom turn out work which has the 
 stamp of genius upon it. Theory holds them down in her 
 rigid grasp, and they have not the pluck to try anything 
 or dare anything that seems opposed to her teachings. If, 
 on the other hand, theory be regarded as a reliable servant, 
 to be consulted when difficulties occur in practice, her 
 value will soon be recognised. 
 
 These thoughts came into my mind once when watching 
 a young experimenter, who was endeavouring to make 
 some enlargements on bromide paper from small negatives, 
 by means of an oil lantern. The negative was placed 
 on the stage of the lantern, and its image was projected 
 upon the side of a wooden packing-case, which stood on 
 the table in front of it. My young friend was endeavour- 
 ing to make from his small negative (|-plate) enlarged 
 copies of different sizes ; and, to obtain the different sized 
 images, he had, of course, to move the focussing surface 
 either to or from the lens as the image was required to 
 
 Q 2 
 
228 
 
 THE BOOK OF THE LANTERN. 
 
 be smaller or larger. But with regard to exposure he 
 worked entirely by rule of thumb, or rather, I might 
 say, by no rule at all. It was all guesswork, and, 
 although he tried many pilot slips of paper with watch in 
 hand, he failed to turn out any really correctly-exposed 
 pictures. His failure was chiefly due to his utter ignorance 
 of the law in optics, which has been already considered 
 on page 118. 
 
 Referring once more to fig. 39 on that page, let the four 
 squares numbered 1, 2, 3, and 4, be printing-frames 
 placed at distances of 1, 2, 3, and 4 feet from a 
 candle-flame. Let us suppose, also, that we have ascer- 
 tained by experiment that the plate or paper in the first 
 position (No. 1) is sufficiently affected by the light if it 
 remain there for one minute. (This is, of course, merely 
 stated as a case in point. Bromide paper at such a distance 
 would be sufficiently exposed, under a normal negative, in 
 about eight seconds, while a chloride plate under such con- 
 ditions would want two minutes or more.) Then, if we re- 
 move the frame to position No. 2 — at 2 feet from the light 
 source — the necessary exposure will not be doubled, as some 
 might think, but quadrupled. For the square of 2 is that 
 number multiplied by itself, — i.e., 4. The right exposure, 
 therefore, will be four minutes. Removing the frame to 
 position 3, we must once more square that number in 
 order to arrive at the right number of minutes, for ex- 
 posure at this increased distance. 3 x 3 = 9. Therefore 
 nine minutes Avill be the time. It is easy to see that when 
 the printing-frame is removed to the farthest distance of 
 all, which is 4 feet from the light source, the exposure 
 
TI1E LOOK OF THE LANTERN. 
 
 229 
 
 will be sixteen minutes. To make the diagram more 
 explicit, the vertical squares 1, 2, 3, and 4, have been so 
 subdivided that the number of spaces in each indicates 
 the number of units of exposure, be that unit a second, a 
 minute, or an hour. The same rule holds good for en- 
 larging operations. Thus, supposing that we are working 
 with an optical lantern, and that the necessary exposure 
 at 1 foot from the lens is half a minute ; at 2 feet the 
 time will be two minutes ; at 3 feet four minutes and 
 a half ; and so on. The practical worker will have this 
 little bit of theory in his mind whenever he is operating, 
 and he will soon be convinced that the theory is strictly 
 correct. 
 
 Another help in enlarging, which will be found useful, 
 is a little piece of apparatus, — if it can be dignified 
 by that name, — which I have lately made, and which I 
 call an exposing-gauge. It is so simple in construction 
 that any one can make it out of a couple of strips of card- 
 board. The arrangement is shown in fig. 57. The size 
 of the gauge is immaterial, but a length of 20 inches 
 will be found convenient. A slip of card of that length, 
 and about 1 inch in breadth, is cut with pointed ends, 
 each point having a hole pricked in it as shown. By these 
 holes, and with the assistance of a couple of drawling-pins, 
 the contrivance can be readily attached to any flat surface 
 upon which the enlarged image from the lantern is 
 focussed. Placed above this slip is another piece of card 
 slightly shorter, and with a round hole in the centre. The 
 two strips are bound together with pieces of tape glued 
 over their upper and lower edges, the two ends being left 
 
230 
 
 THE BOOK OF THE LANTERN. 
 
 open, like a sleeve, for the reception of a slip of paper 
 like that shown in fig. 58. 
 
 Fig. 58. 
 
 < $k~ ^ * Q> • ^ 1> 
 
 > I « M l c 1 g 1 * ij < 
 
 Fig. 59. 
 
 Fig. 59, as indicated, really consists of two slips of paper 
 gummed together end to end. One is sensitive bromide 
 p per, ten inches in length, which has been spaced out 
 into five divisions, and marked a, b, c, d, e, with an aniline 
 ink pencil. The other part is ordinary white cartridge 
 paper, slightly longer than the sensitive slip. Its purpose 
 is to serve as a handle by which to pull the sensitive paper 
 through the sleeve, and also to furnish a white surface 
 upon which a small part of the picture can be focussed, 
 that small part being confined to the central circular hoi 
 in the upper card. 
 
 Now let us see how the gauge is used in practice. It is 
 first pinned on the focussing board so that a distinctive 
 part of the image is thrown upon the central hole. In the 
 case of a portrait this should be the eye. Having focussed 
 carefully on the blank paper, the first division of the 
 sensitive slip, which will be that marked e, is pulled in 
 front of the opening. Let this be exposed for, say, fifteen 
 seconds ; then pull the slip onwards, and expose d for 
 twenty seconds, c for twenty-five seconds, and so on. The 
 gauge is then taken into the dark room, its slip of sensitive 
 paper taken from its yoke-fellow, and carefully developed. 
 
THE BOOK OF THE LANTERN. 
 
 231 
 
 It will then soon be seen which of the lettered spaces has 
 received the correct exposure ; and a memorandum noting 
 time and distance of lens from screen can either be 
 attached to the negative, or entered in a book against a 
 number corresponding with a number scratched on the 
 glass negative. 
 
 The same principle can be applied to contact printing 
 in a frame on bromide paper, by gas or lamp light. When 
 the frame has been charged with its negative and the 
 bromide paper, support it upright at a distance of, say, 
 18 inches from the turned-down flame. Now, place 
 in front of it an opaque card, sufficiently large to more 
 than cover the frame. This card should have a hole about 
 1 inch in diameter cut in it in one corner. Turn up the 
 light and expose for five seconds. Alter the position of the 
 hole and give ten seconds, and so on. When the paper is 
 subsequently developed the several exposures can be 
 readily identified, and the negative can be labelled to the 
 effect that it requires so much exposure at a given distance 
 from a flame. Thus — Bromide paper, 18 in. 25 sec. This 
 negative will then be an infallible guide for the exposure 
 of negatives of a similar type ; for a systematic worker, 
 unless he be quite a beginner, will fall into the way of 
 producing negatives of much the same character and 
 strength, and printing from them by lamp light will then 
 become an easy matter to hijn. 
 
 After this somewhat long but not unnecessary digression, 
 I will resume my directions for enlarging on bromide 
 paper, and for the sake of simplicity will suppose that the 
 operator is not supplied with the special form of easel 
 
232 
 
 THE BOOK OF THE LANTERN. 
 
 which I have referred to, but is using a mere board for the 
 purpose. 
 
 The paper is supplied in cases, either in flat sheets, or 
 rolled with the sensitive surface inwards. A piece of the 
 required size is pinned on the focussing board \ and the 
 best way to do this is to pin the two upper corners 
 first, and to unfold the paper over the board, pinning it 
 down at the edges as required. Drawing-pins will do, but 
 ladies' bonnet pins are much more easily handled in the 
 semi-darkness of the room. Now uncover the lens for the 
 proper time, and be careful that the lantern is quite free 
 from vibration. If you wish the picture to be vignetted, 
 this is most easily managed during exposure. A piece of 
 brown paper, a foot square, is cut in the centre with an 
 oval opening, with a serrated edge. Hold this in front of 
 the lens, and keep it in gentle movement, so that the 
 pointed edges of the paper are always changing their places. 
 This will cause the edges of the picture to be ill-defined, 
 and a white margin will be left outside them. 
 
 I need hardly point out that in enlarging by this method 
 the operator has a wonderful amount of controlling power 
 at his disposal, in bringing out certain parts of the picture 
 with extra density, and reducing those parts which may 
 require such treatment. Thus the distant portion of a 
 landscape may be lightened by a card moved with discre- 
 tion over that part of the image during exposure. If, too, 
 some point in the negative is of unusual density, it can 
 receive- extra exposure by using a card with a hole in it, 
 in front of the easel. 
 
 At the end of the exposure the lantern is capped, the 
 
THE BOOK OF THE LANTERN. 
 
 233 
 
 paper is unpinned, and carried to the developing dish. It 
 is now saturated with cold water on both sides, and clean 
 hands may assist in spreading the water over the surface 
 until it lies perfectly flat on the bottom of the tray. The 
 water is now drained off and the developer applied. The 
 ferrous oxalate method is by far the best to adopt, but the 
 proportion of iron should be reduced to about one-sixth, or 
 even one-eighth of the oxalate solution ; and to insure the 
 best results, the exposure should be such that only a very 
 small dose of bromide solution is necessary. Some workers 
 prefer to bring the image out slowly by using an old 
 ferrous oxalate solution. I myself prefer it mixed per- 
 fectly fresh, and am quite certain that if the best results 
 are looked for, fresh developer should be mixed for every 
 print required. The development must not be carried too 
 far, for the image gains in density under fixation. When 
 development is judged to be complete, drain off the liquid, 
 and immediately, without washing, flood the surface of the 
 picture with an acid solution. 
 
 Acetic acid (glacial) 1 drachm. 
 
 Water ... ... ... ... 16 ounces. 
 
 The addition of this solution keeps the whites of the pic- 
 ture pure. In a minute or two pour the acid away, wash 
 the print, and fix in fresh hypo of the usual strength. The 
 print ought to be fixed in about ten minutes ; if it is allowed 
 to remain in the hypo longer than necessary the half-tones 
 are quickly destroyed. Now wash the paper in several 
 changes of water, and let it soak for a couple of hours at 
 least before drying. 
 
 It is not very difficult to print in clouds, from a separate 
 
234 
 
 THE BOOK OF THE LANTERN. 
 
 negative, on an enlarged positive on bromide paper. The 
 process depends npon the circnmstance that the paper 
 remains sensitive to light, — but in a diminished degree, — 
 after the developing solution has been applied to it, Pro- 
 ceed as follows : — Expose your landscape as usual, but stop 
 development before the required density is obtained, and 
 wash the paper. Now placing your cloud negative in the 
 lantern, pin up the paper once more, shielding the land- 
 scape portion by a piece of card kept in movement, and 
 give another exposure. Now re-develope to the right 
 density, and you will find that while the landscape gains 
 in strength the clouds will become faintly apparent. The 
 picture can then be fixed and finished according to the 
 directions given. 
 
 If several copies of an enlargement are required, the 
 best method will be to make an enlarged negative on 
 paper, using a glass positive (an ordinary lantern slide) in 
 the lantern. The same operations as those just described 
 are necessary, but the exposure can with advantage be 
 increased. I should also recommend the use of alkaline 
 development, and I think that washing soda and pyro is 
 the best form of it for the purpose. The paper negative 
 when dry is rendered transparent by being passed through 
 a bath of melted paraffin wax. It can then be used in 
 an ordinary printing- frame to produce prints as may be 
 desired. 
 
 Some time ago I published a new method of obtaining 
 enlarged negatives, which will be useful to those who wish 
 to work with an ordinary lantern, and who are ready to 
 undertake the task of plate-making, 
 
THE BOOK OF THE LANTERN. 
 
 235 
 
 I had occasion to obtain from some half-plate negatives 
 some copies of them on plates measuring 16 by 13. The 
 problem I put to myself was this, — which is the quickest 
 and best way of accomplishing the work ? After some 
 consideration I determined to work with the limelight, 
 for the weather was dull and uncertain at the time I am 
 speaking of, and 1 thought that I would at once eliminate 
 one common source of error by adopting a mode of illumi- 
 nation which represents a constant quantity. This being 
 settled, I next thought over the different systems of en- 
 larging, and finally decided to try a new plan. 
 
 I am so constantly using the lime-light for lecture 
 purposes, that a residue of oxygen is always at hand, 
 ready for any home experiment that I like to try ; other- 
 wise, I should, perhaps, have decided to carry out my plan 
 with some other illummant. Fitting a blow-through lime- 
 jet to an experimental lantern with a 4-inch condenser, 
 and with a quarter-plate portrait lens as the objective, my 
 optical arrangements were complete. But a 4-inch con- 
 denser is clearly useless for projecting the image of a 
 negative nearly double its area. My first operation was, 
 therefore, to make some small positives on glass from the 
 negatives. This was easily done by fitting the negatives 
 into my copying apparatus, and using a quarter-plate 
 camera. The size of the resulting positives was just two 
 inches across ; smaller, it may be thought, than was abso- 
 lutely necessary. But, by this plan, I employed the best 
 part of the projecting lens, and there was no chance of any 
 falling off in sharpness at the margin of the pictures. 
 
 The small positives were made with very great care, the 
 
236 
 
 THE BOOK OP THE LANTERN. 
 
 exposure and development being so controlled that the 
 resulting pictures were somewhat denser than would be 
 advisable for an ordinary lantern-slide. They exhibited in 
 miniature every detail to be found in the negatives to 
 which they owed their origin ; and, in more than one case, 
 an improvement was effected in the process of reduction, 
 for some of the negatives were yellowed in certain portions, 
 and would, therefore, print unequally. This was obviated 
 by shading during exposure. 
 
 The positives, although measuring only 2 inches across, 
 were taken for convenience on the standard plates for 
 lantern pictures, 3^ by 3^ ; so that a broad margin of 
 clear glass remained all round them. This was covered 
 with black varnish, after which the glasses were fitted into 
 the usual grooved carriers employed in lantern work. 
 
 The next thing was to arrange a proper focussing-screen 
 for the reception of the image. This took the form of a 
 sheet of glass, 16 by 13, covered on one side with white 
 paper. Temporary wooden c ips, fastened to the wall at a 
 convenient height from the ground, held this papered glass 
 in position, and in such a way that it could be readily re- 
 moved and a sensitive plate put in its place. 
 
 It is with regard to the sensitive plates that I must now 
 speak. I found that commercial plates of the size required, 
 16 by 13, were very expensive; if I remember rightly, some- 
 thing like £2 per dozen was the price quoted to me. This 
 was more than I cared to expend on mere experimental 
 work j besides which, it goes against the grain to buy 
 plates when one has been in the habit for years of making 
 them of unsurpassed quality. I now bethought me that I 
 
THE BOOK OP THE LANTKRN. 
 
 23t 
 
 had put away somewhere a jar of chloride emulsion, which 
 I had made some months before, and had left neglected for 
 want of opportunity to make plates from it. Why, thought 
 I, should I not make some 16 by 13 plates with this 
 chloride emulsion ? The thing was no sooner conceived 
 than put in practice, and that night the plates were coated 
 and racked, to the number of eighteen. I also was careful 
 at the same time to cover a few quarter-plates, with which 
 I could make trial exposures. 
 
 There is one great advantage in manipulating chloride 
 emulsion and the plates made from it : it is so insensitive 
 — about 100 times less so than bromide plates — that the 
 brightest of yellow lights can be used without affecting it. 
 I use a brilliant paraffin lamp, surrounded by a wire fence, 
 and tl*is is covered with a screen of yellow oiled p:iper. 
 The light given is so great that a book can easily be read 
 at the further end of the room, and my coating-room is 
 quite a large one. 
 
 Two days later I was reidy for work, and had the 
 lantern adjusted at the right distance from my focussing- 
 screen on the wall to give an image of the required size. 
 Carefully focussing the first picture, I took one of the 
 little trial -plates, and held it against the focussing screen 
 for one minute. Upon development it showed under- 
 exposure. One or two more trials resulted in my finding 
 that the correct exposure was ninety -five seconds. I now 
 felt some confidence in dealing with the larger plates, and 
 I exposed three, one after another. 
 
 Now came the development. 1 mixed, first of all, one 
 pint of developer from my stock solutions, and this I put 
 
238 
 
 THE BOOK OF THE LANTERN. 
 
 into a jug. The first plate was put into a dish, and the 
 whole jugful swished over it. The image flashed out at once. 
 This is always the case with my chloride plates, so that it 
 did not surprise me Keeping the developer moving over 
 the plate, I lifted up the glass at intervals so as to watch 
 its progress. In about four minutes it had attained 
 sufficient density. I then emptied the developer back into 
 the jug, for I knew it would serve for several plates in 
 succession. The negative in the dish was now thoroughly 
 washed with about a gallon of water, and transferred to 
 the fixing-bath. The remaining plates were then treated 
 in exactly the same way, and without a single failure. 
 
 There was at first some difficulty in thoroughly washing 
 such large plates, but I solved it by making use of the 
 bath-room. The bath was filled with water, and the 
 plates were placed along the sides, film-side down. In less 
 than an hour they were thoroughly freed of the fixing salt. 
 
 These negatives were all that could be desired. Some 
 of them were purposely reversed for printing by the 
 carbon process, this reversal being brought about by the 
 simple expedient of causing the film-side of the little 
 positive to face the light in the lantern. Their perfection 
 of detail may be gauged by the following : In one case the 
 little positive had become rather dusty previously to 
 exposure, and I took it out of the lantern, and rubbed its 
 varnished surface with my handkerchief. This caused 
 some tiny scratches upon it, which were at the time quite 
 unnoticed ; but the scratches were clearly visible on the 
 enlarged negatives. They were, certainly, not thicker 
 than the finest spider's web, — but still, there they were. 
 
THE BOOK OF THE LANTERN. 
 
 239 
 
 I have already indicated how this work of enlarging 
 can be done with an ordinary optical lantern, so long as 
 the size of the negative is not above that of a lantern 
 
 slide. For larger negatives it is far better to use a proper 
 enlarging lantern of the type shown at fig. 60. 
 
CHAPTER XVII. 
 
 THE LANTERN MICROSCOPE AND THE OPAQUE LANTERN. 
 
 P to a recent date the so-called lantern micro- 
 scope supplied by various dealers was but a toy, 
 having all the faults which it was possible to 
 imagine in an optical instrument. Moreover, it neces- 
 sitated the use of specially prepared objects of large size, — 
 the wings of insects and the like. But latterly a good deal 
 of ingenuity has been expended on the instrument, and it 
 has been brought to great perfection. Objects as prepared 
 for the ordinary microscope can now be used for projection 
 in the lantern microscope, and this one change of the 
 conditions under which the instrument can be used points 
 to an improvement of no mean kind. 
 
 There are certain requirements to be looked for in a 
 really serviceable lantern microscope. The first of them is 
 good illumination. The most perfect form of limelight jet 
 must therefore be used, and even this, when the higher 
 
THE "BOOK OP THE LANTERN. 
 
 241 
 
 powers of the instrument are employed, is far from being 
 enough. The electric light would obviously be the best 
 form of illuminant to use for the microscope, but tlie 
 incandescent variety is far too feeble, and the arc form 
 possesses neither the steadiness nor the accuracy and per- 
 manence of centreing which is so requisite in microscopic 
 work. So to the limelight we must at present confine our 
 attention, aiding it as far as possible by careful arrange- 
 ment of the lenses used in conjunction with it. Hence the 
 condenser must be of the best form, and must be seconded 
 by a substage condenser suited to the objective or power 
 which happens to be used. Provision must also be made 
 to filter the light through a layer of alum solution, which 
 absorbs the heat rays, and saves valuable objects from 
 being destroyed. 
 
 Having secured the brightest light possible, and done 
 our best to concentrate it upon the object, we have 
 next to consider the best means of forming an image of 
 that object upon the screen. An objective may do excellent 
 work with the ordinary microscope, but utterly fails to 
 give a satisfactory image on the lantern screen. Perhaps the 
 definition in the centre of the disc is satisfactory, but the 
 margins are all hazy and indistinct. One may examine a 
 large numberof objectives with the lantern microscope before 
 one is found suited to the work. But makers are now 
 giving serious attention to the requirements of the recently 
 perfected instrument, and objectives of great excellence 
 can be obtained. 
 
 One of the most perfect as well as simple arrangements 
 for showing microscopic objects with the ordinary lantern 
 
 R 
 
242 
 
 THE BOOK OF THE LANTERN. 
 
 is the attachment shown at fig. 61. This contrivance 
 may be compared to an ordinary microscope with its tube 
 removed, and with the lantern light at the back of the 
 
 Fig. 61. 
 
 stage instead of the mirror. The attachment is fixed 
 on the lantern in place of the nsnal objective, and the 
 objects to be shown are supported in a vertical position by 
 spring clips. The microscope objective is held, as shown, 
 on a movable arm worked to and fro by a milled headed 
 focussing screw. At the back of the object is a substage 
 condenser, not shown in the cut, and a revolving plate 
 with different sized diaphragms. A trough containing a 
 saturated solution of alum is placed on the lantern stage 
 to protect the objectives from heat. In using the instru- 
 ment the limelight must be adjusted in distance from the 
 condensing lens for each different power used; and, indeed, 
 for every change in the diameter of the diaphragm 
 employed. For living objects, such as those illustrating 
 pond life, a small tank is used, and is placed against 
 the spring clips The objectives suitable for this form 
 of instrument are those which range between 3 in. 
 
THE BOOK OF THE LANTERN. 
 
 243 
 
 and 4-10ths of an inch. Its performance leaves little to be 
 desired. 
 
 A far more elaborate form of lantern microscope is that 
 which is shown at fig. 62, and which has been designed 
 by Mr. Lewis Wright. In the opinion of most of our 
 eminent microscopists, including Dr. Dallinger and the late 
 Dr. Carpenter, this instrument is by far the most perfect 
 of the kind ever produced. Tt is certain that no better 
 effects are possible than are produced with high-power 
 
 Fig. 62. 
 
 objectives with this microscope, until the electric light 
 may be so perfected as to place a new power in our hands. 
 A flea 15 feet long, literally larger than an elephant, is 
 shown with this microscope brilliantly and exquisitely 
 defined, while the circulation of the blood in a frog's foot 
 can be as easily seen as by the table microscope. 
 
 r 2 
 
244 THE BOOK OF THE LANTERN. 
 
 The instrument can be made either complete in itself, as 
 shown in the cue, or it can be fitted to any good optical 
 lantern. In the first case, it is provided with a triple 5-in. 
 condenser, which insures the maximum amount of light, 
 and in the latter case the lantern condenser, of whatever 
 form it may happen to be, is brought into use. The 
 illustration gives a very fair idea of this instrument, by 
 which the relation of its various parts can be well under- 
 stood. It has a coarse adjustment focussing screw, as 
 well as one for fine adjustment. The tube in front of the 
 objective is for the reception of various lenses to give 
 extra amplification, and the necessary alum-tank is let 
 into the brass front tube, midway between its supporting 
 pillar and the large condensers. The details of the stage 
 and revolving diaphragm plate are much the same as in 
 the instrument last described, but the substage condensers 
 are of varying foci, and are suited to the different objec- 
 tives employed. The milled head immediately above the 
 pillar is in connection with a rack tube, which provides the 
 necessary distance adjustment for these condensers. 
 
 THE OPAQUE LANTERN, 
 
 It will be at once conceded that most objects, animate 
 and inanimate, can be photographed, and that such photo- 
 graphs can be used as lantern pictures. But there are 
 still others which cannot be so treated, or rather, which 
 can be better shown as opaque objects. The worker with 
 the microscope will be able to appreciate the possibility 
 of showing, by means of the lantern, objects which are 
 not transparent. Some of the most beautiful effects 
 
THE BOOK OF THE LANTERN. 
 
 245 
 
 seen in the microscope are by means of opaque objects 
 viewed by means of the spot lens. In like manner we 
 can obtain wonderful effects by the use of the opaque lan- 
 tern. Let me give one or two examples of the use of such 
 an instrument. Suppose that a lecture upon the history 
 and construction of the watch is contemplated. How dull 
 such a lecture would be if illustrated merely by a set of 
 diagrams ! The audience would soon be lost in the maze 
 of toothed wheels and springs, and few would understand 
 the difference between one movement and another. But let 
 the same lecture be illustrated by watches in*action, their 
 enlarged images thrown on the screen, and their wheels all 
 at work, and how differently will the audience regard the 
 subject before them. Every tiny screw, the brilliant blue 
 of the steel parts, the very grain of the metal is beauti- 
 fully shown, while the ceaseless and silent working of the 
 mechanism adds greatly to the picture. Coins and medals 
 can also be splendidly shown by the same apparatus, and 
 far better than in any other way. Various fruits can be 
 shown in section ; a lemon or orange so treated being a very 
 curious object, especially if it be squeezed, when the pips 
 and juice fly upward, or, at any rate, appear to do so. A 
 freshly-opened oyster makes another peculiar object for 
 the opaque lantern. These few examples will show that 
 this form of lantern is one which can be of great use in 
 intelligent hands. It is especially serviceable to the 
 owners of cabinets or collections of curiosities, — moths and 
 butterflies, coins, medals, shells, minerals, &c, — which 
 cannot readily be photographed, or which it is desirable to 
 show with their natural colouring. 
 
246 
 
 THE BOOK OF THE LANTERN. 
 
 The opaque lantern was first devised by Chadburn, and 
 for a long time was known by his name. Its construction 
 is simple enough. The object is so placed that it can be 
 strongly illuminated by the condensed rays from either 
 
 shown. At one time, a large instrument of this type was 
 made for casting the image of a human face on the screen, 
 the lenses being of immense size. I saw this instrument 
 at work more than once, but its effect was most dis- 
 appointing. It certainly was not worth the trouble and 
 expense incurred in its construction. It was, of course, 
 fitted with a reversing lens, so that the face should appear 
 the right way up. The owner of this face, by the way, 
 suffered tortures during the short time of exhibition, for 
 the powerful limelights close to, and on each side of his 
 head, were so hot that they blistered his skin. He was 
 made to smile at the audience, and then to drink their 
 good health in a glass of wine, a refreshment which the 
 poor man really needed after his grilling. 
 
 Under the name of Aphengescope a contrivance is now 
 made for fitting on to the ordinary form of lantern, thus 
 dispensing "with the cost of extra lenses. With a lantern 
 
 Fig. 63. 
 
 one or two limelights ; an objec- 
 tive lens being used to form the 
 image on the distant screen. 
 The annexed diagram, fig. 63, 
 will explain the relations of the 
 different parts of a good opaque 
 lantern. LL are the limelights, 
 CC the condensers, O the ob- 
 jective, and E the object to be 
 
THE BOOK OF THE LANTERN. 
 
 247 
 
 thus fitted ordinary carte de visite portraits can be shown, 
 as well as the objects already enumerated. Fig. 64 shows 
 
 Fig. 64. 
 
 a modified form of aphengescope fitted to a lantern which 
 at the same time is ready to show slides in the ordinary 
 
248 
 
 THE BOOK OF THE LANTERN. 
 
 manner. It will be noticed that behind the objective is 
 placed a sloping mirror, which reflects the light upon the 
 card, photograph, or other object above it. The objective 
 is then shifted from its nsnal position to an orifice above, 
 which is shown in the cut with a stopper in it. This 
 lantern — the design of Laverne & Co. — is lighted by a 
 mineral oil-lamp, but, obviously, the limelight could be 
 adapted to it. Mr. Medland, of the Borough, has intro- 
 duced a lantern on the same principle, see fig. 65. So much 
 
 Fig. 65. 
 
 light is necessarily absorbed by the arrangements of the 
 opaque lantern, even in its best forms, that the brightest 
 of illuminants must be secured to give it full effect. 
 It is on record that some years back a form of opaque 
 
THE BOOK OP THE LANTERN. 
 
 249 
 
 lantern was used in an American Law Court to demon- 
 strate to a jury the manner in which a document had been 
 tampered with by a forger. Illuminated by a strong side 
 light, the magnified image showed clearly where the tex- 
 ture of the paper had been disturbed, both by erasure and 
 by the action of chemicals. 
 
CHAPTER XVIII. 
 
 LANTERN ACCESSORIES. 
 
 CARRIERS. 
 
 LANTERN, as supplied by the dealers, is with- 
 out any means of holding the slides during 
 exhibition. The slide stage is there, but it is 
 about 4^ inches in height, while the slides themselves 
 are 3^ inches square. To obviate this difficulty, it 
 becomes necessary to fit this stage with a wooden 
 contrivance called a slide carrier, which can be pur- 
 chased of many different patterns. Professional exhi- 
 bitors use a wooden frame for each separate slide, but 
 this plan is both inconvenient and unnecessary for the 
 amateur. Besides which it is positively a bad plan for the 
 user of a single lantern ; for as each picture is removed, 
 and another one put in its place, the screen is left bare 
 while the transfer is effected. This not only has a bad 
 
THE BOOK OF THE LANTERN. 
 
 251 
 
 effect, but it is distracting to the audience. Moreover, the 
 pictures suffer, for they compare disadvantageously 
 with the far brighter white disc by which they are 
 alternated. 
 
 I can recommend two forms of carrier which obviate 
 this difficulty. The first is a grooved frame, open at either 
 side, with a travelling tape in the lower groove, which is 
 put in motion by a winch handle. The slides move 
 through the lantern one after another, like a panorama, 
 but care must be taken that they are not allowed to fall 
 out and get broken as their time for exhibition expires. 
 The other form which I recommend is quite different in 
 principle, and of the two methods I prefer it. In this 
 latter carrier there is a kind of central frame which 
 is accurately adjusted to the lantern stage. Within it, 
 and moving freely from right to left, is a double carrier, 
 holding two pictures side by side. While one picture 
 is being shown, the other is being changed, the right 
 and left hand carrier being used alternately. The sole 
 objection to this form of carrier is the necessity for 
 the exhibitor to reach over his lantern so as to change 
 every other picture, which is a slightly awkward thing to 
 perform. 
 
 A modification of this sliding principle, which consists 
 of a double changing stage, working vertically, has been 
 introduced, but I fancy that the lantern must be con- 
 structed purposely for it. I mean that it is not sold as an 
 independent carrier, which can be fitted to any existing 
 lantern. This consideration, of course, greatly limits its 
 adoption. 
 
252 
 
 THE BOOK OF THE LANTERN. 
 
 Whiting's patent arrangement for facilitating the ex- 
 hibition of slides is extremely ingenious, bnt seems to me 
 to be an adaptation of Samuels' changing box, for photo- 
 graphic cameras. At any rate, the same principle is 
 involved. It consists of a pusher of wood working be- 
 tween grooves on the lantern stage. Close against it is a 
 box of slides with a powerful spring at the back of them, 
 so that they are forced up against the pusher, the front 
 one being always in the right position to be pushed for- 
 ward on to the stage. The act of moving the pusher 
 sends a picture on to the stage, removes that previously 
 shown, which goes into another box, or drops down an 
 inclined plane out of the way, and at the same time the 
 lens is covered so that there is momentary darkness on 
 the sheet. This darkness is, I think, preferable, and less 
 trying to the eyes of the audience than if the actual 
 change of picture took place visibly. 
 
 Other forms of carriers provide in a different manner 
 for the lens being covered at the moment of change. One 
 very good one consists of a pair of wings, which open and 
 close automatically over the front of the objective lens 
 as the change is made. In this case the first picture 
 seems to darken down on the screen towards the centre, 
 the reverse action immediately discovering the nex^ 
 slide. 
 
 The following remarks, which were written by me, and 
 were published in the Yearbook of Photography, will 
 describe the kind of carrier which I myself use : " When 
 a man is in the habit of travelling about from place to 
 place on lecturing inteix^, ' ne will, if wise, reduce his 
 
THE BOOK OF THE LANTERN. 
 
 253 
 
 impedimenta in the shape of lantern and lantern belongings 
 to the smallest possible bnlk consistent with efficient work. 
 As much of my time has been and is spent in this way, 
 I have given a great deal of thought to this matter of 
 reduction of bulk, aud have achieved some little success in 
 it. But it is only to one particular point that I now wish 
 to draw attention, and I do so in the hope that what I have 
 done may be as useful to others as it has been to me. In 
 the first place I think that all lecturers will agree that each 
 lantern picture should be fitted in a carrier of its own. The 
 various forms of panoramic and shifting carriers which are 
 fixed in the lantern while the glass pictures are passed 
 through them at the time of exhibition are all very well 
 for home use and private work, but in my opinion are not 
 suitable for employment in public halls. I need not name 
 all my objections to them, for one will suffice. The 
 pictures are not sufficiently protected from breakage, and 
 the risk of breakage, even of one slide out of a set, is a 
 thing not to be thought of by a good exhibitor. At first I 
 used 7 by 4 mahogany-grooved carriers for all my pictures, 
 but I found that they were objectionable, on two grounds : 
 one of these is that they readily break, and the other is 
 that in packing they take up far too much room. It was 
 to obviate these difficulties that I designed the carrier now 
 to be described, and which I have had in constant use for 
 three years with every success. My only objection to it is 
 the necessity for making it myself, which is perhaps no 
 real objection at all, for a little carpentry forms a healthy 
 relaxation to one whose occupations are chiefly of a seden- 
 tary nature. 
 
254 
 
 THE BOOK OF THE LANTERN. 
 
 My slide-carrier consists of a piece of wood 7 inches long 
 and 4 inches wide, with a square opening in the centre to 
 receive the glass picture of the standard size, 3^ by 
 inches. This is faced on each side with a piece of card- 
 board, the opening of which is so much smaller as to form 
 a rebate in which the picture rests, and from which it 
 cannot fall out. 
 
 And now to describe the method of manufacture. First 
 procure two pieces of sheet zinc, each measuring 7 by 4 inches 
 outside, but having openings of slightly different areas. 
 These are indicated in the annexed cut (fig. 66), the opening 
 
 ~ — i 
 
 |i 
 
 I 
 
 J* ! 
 
 ** " 1 
 
 L J 
 
 Fig. 66. 
 
 in one piece of zinc being shown by unbroken lines, and in 
 the other by dotted lines. It is best to make these patterns, 
 in the first instance, in thin card, and to hand them to a good 
 workman to copy in zinc. (I may mention in parenthesis 
 that here I found my chief difficulty. The average British 
 working man who has been brought up in the zinc industry 
 
THE BOOK OF THE LANTERN. 
 
 255 
 
 can make a first-rate chimney -pot, but when out of the 
 chimney-pot groove he is rather at sea. If he tells yon that he 
 can cnt ont in zinc yonr pattern correctly, " Trnst him not, 
 lib's fooling thee " ; at any rate, carefully check his work, and 
 yon may find it out a trifle, and this trifle when magnified 
 in the lantern is no trifle.) With correctly-cnt zinc patterns 
 yon can get through the work of making carriers very 
 quickly. The pattern with the larger opening may be 
 labelled W, for it is for wood only, and the other labelled 
 C, for cardboard. 
 
 The wood to use is the best pine, which in thickness 
 should approximate to the average lantern slide, say one- 
 eighth of an inch. This can be obtained at any good saw- 
 mills. Laying the zinc pattern on this, and pencilling 
 *by its aid, a whole board can be quickly marked out for 
 cutting. This cutting can be easily accomplished by using 
 a sharp shoemaker's knife. The cardboard can be of the 
 thinnest description, and this, too, can be cut in the same 
 manner, using the zinc pattern designed for it. With 
 several wooden pieces ready cat, and double their number 
 of cards, you may now proceed to put them together. With 
 good hot, but thin glue, paint over one surface of the wood, 
 and press one of the cards upon it, taking care that the 
 centres of the two agree. Place the joined pieces on your 
 work-table, with a heavy, flat weight above them ; when 
 No. 2 is similarly, treated, place it also under the weight, until 
 you have a goodly pile of pieces of wood faced on one side 
 with card. Leave them for the night. The next opera- 
 tion is to place a glass picture in each half-formed slide, 
 and to glue the cardboard face to each. Once more the 
 
256 
 
 THE BOOK OF THE LANTERN. 
 
 hot glue and weight operation must be repeated, until the 
 batch, — say two dozen slides, —is complete. When com- 
 plete, this batch, with a piece of blank board at each end 
 of the pile, may be screwed up between a couple of car- 
 penter's cramps, and left before the kitchen fire all day or 
 all night, until the glue is thoroughly hardened. When 
 quite dry and hard the slides may be separate 1 and again 
 arranged between the cramps, in such a position that their 
 edges can be run over with a sharp plane. After this thev 
 can be separately rubbed on every edge with glass paper, 
 and, when dusted, they are finished. 
 
 The advantages of these carriers are many. Firstly, 
 you may drop one from a height of 6 feet from the floor 
 with absolute impunity. Secondly, if the zinc patterns 
 be correctly cut, the slides will register correctly with one 
 another. Thirdly, six dozen, — which is about the usual 
 complement for a lecture set, — will pack in the space 
 occupied by three dozen under the old system. The sole 
 disadvantage pertaining to these carriers is, that the pic- 
 tures cannot be readily shifted from one to another. The 
 remedy is obvious. For lectures of an ephemeral cha- 
 racter, — I mean for those the subject of which is merely 
 of passing interest, — use the old form of carrier, but for 
 more permanent ones adopt mine. 
 
 LANTERN LEGS. 
 
 It is given to a few to know what it is to arrive at a 
 schoolroom or other lecture-hall in some remote country 
 district, and to expect to find a few conveniences ready to 
 hand. The first thing to ask for is a table, upon which 
 
THE BOOK OP THE LANTERN. 
 
 257 
 
 can be placed the lantern-box, while the lantern itself com- 
 monly screws to the top of the said box. There is always 
 a difficulty in finding the right kind of table. It is either 
 too small or too large, or else it is rickety and nnsafe, or 
 perhaps it is too beantiful to be devoted to such a heathen- 
 ish purpose as the support of a lantern -box, — all which 
 things happened to me and my assistant times out of 
 number, until I invented a lantern-support for myself, 
 consisting of four iron legs. With them I can now laugh 
 the decrepit local table to scorn, and the beauty of the 
 leather-covered library specimen, which must not be 
 touched by sacrilegious hands, is a thing which ceases to 
 interest me. In a word, I am independent of such primi- 
 tive supports, and am as proud of my iron legs as is a 
 Chelsea pensioner of the wooden understandings which he 
 exchanged in the Crimea for those with which he was 
 born. 
 
 The accompanying sketches will in a moment cause the 
 form and purpose of these legs to be understood. They 
 are made of iron, having a sectional area of 1 inch by 
 three-eighths of an inch. Each fits into a socket upon the 
 lantern box, and each has at its lower end a kind of flat 
 toe turned outwards, through which is a hole by which 
 the leg can be screwed to the floor. This, however, is 
 hardly necessary, for the weight of the lantern and its 
 box, together with the slides which it .contains whilst in 
 use, are quite sufficient to make the whole arrangement as 
 firm as a rock. 
 
 In the annexed cut (fig. 67) A is the lantern box, fitted with 
 a strong frame at the bottom, F, upon which the sockets can 
 
 S 
 
258 
 
 THE BOOK OF THE LANTERX. 
 
 be screwed. L is one of the legs in position. T is an 
 enlarged view of the toe of one leg, showing the screw- 
 hole where it can be attached to the floor. A 1 is a socket, 
 
 Fig. 67. 
 
 showing how it is composed of two pieces of iron, one flat 
 and one bent. I may mention that the top of the leg, 
 which fits into the socket, is diminished in size for that 
 purpose, and that the shonlder thns formed on it holds it 
 firmly in position. I have used these legs for several 
 years, and have never seen anything which would fulfil 
 their purpose so well. They can be secured for travelling 
 by a couple of leather straps, or can be made to go inside 
 the lantern-box. Their combined weight is fourteen 
 pounds. 
 
THE BOOK OF THE LANTERN. 
 
 259 
 
 HAND CAMERAS. 
 
 Photographic negatives for lantern slides should be 
 rather less dense than those used for ordinary printing 
 upon paper : hence it is better to take uegatives for the 
 purpose than to utilise others which have been taken for 
 ordinary reproduction. The lesser density must be gained 
 by stopping the development judiciously, and not, of 
 course, by checking the exposure. There are many 
 cameras now to be had which take small negatives suitable 
 for lantern work. These are so compact and self-contained 
 
 Fig 68. 
 
 that they require no stand, focussing-cloth, or other adjunct 
 and will readily pack away in a portmanteau or box 
 without inconvenience to the traveller. The author has 
 used a camera of this description with great advantage, and 
 has taken many dozens of instantaneous pictures with it. 
 
 A useful form of hand-camera introduced by the 
 Stereoscopic Company is here shown (see fig. 68). 
 
 s 2 
 
260 
 
 THE BOOK OF THE LANTEliN. 
 
 Another camera which is made purposely for lantern- 
 slide negative making has been recently introduced by 
 Messrs. May field & Cobb. This will, when folded np, easily 
 go into the pocket, and is nsed like the last-described 
 whilst held in the hand (see fig. 69). 
 
 Fig. 69. 
 
 A great deal of attention has lately been aroused with 
 respect to so-called detective cameras. They would perhaps 
 be better described as concealed cameras, for there are many 
 reasons why they cannot, except by some happy conjunc- 
 tion of circumstances, be used in the detection of crime. 
 Their manufacture has certainly been brought to great 
 perfection, and a wonderful amount of ingenuity has been 
 displayed in their construction. From experience I can 
 speak most highly of the good pictures which can be pro- 
 duced by them. But one essential condition must not be 
 absent ; such pictures want absolute sunshine. I give 
 three examples of these detective cameras. The first, 
 Watson's (fig. 68), is a leather-covered box, containing as 
 
THE BOOK OF THE LANTERN. 
 
 261 
 
 will be seen oy the dotted lines, a complete camera. This 
 camera can be focussed and manipulated altogether by 
 touching buttons on the outside of the box. 
 
 Fig. 70. 
 
 Next I notice Marion's Parcel Camera (fig. 71), which 
 is of different construction altogether. It consists of a 
 covered box, like a parcel, but this box forms the camera 
 with a lens in front concealed by a paper flap. The 
 
 Fig. 71. 
 
 illustration shows the appearance of the underside of the 
 box, with a slit at one end for the reception of the sensitive 
 plate and the instantaneous shutter apparatus at the other 
 end. The plate is contained in a bag of the shape shown 
 
262 THE BOOK OF THE LANTERN 
 
 at fig. 72, which locks on to the aperture in the bottom of 
 the box, when a plate has to be transferred from one 
 to the other. I have found both these cameras to work 
 perfectly. 
 
 Fig. 72. 
 
 The newest arrangement of the kind is the Kodak 
 Camera introduced by the Eastman Company (see fig. 72). 
 In this small box a hundred pictures can be taken by 
 the simplest possible movements. It contains a ribbon 
 of sensitive material, which is used panorama fashion 
 instead of glass plates. 
 
 Fig. 73. 
 
 I am convinced that there is a very great future before 
 these detective or concealed cameras. That they will pro- 
 duce negatives of firstrdass quality, I have proved again 
 
THE BOOK OF THE LANTERN. 
 
 263 
 
 and again, and it is the thought that such negatives can be 
 so readily made to give lantern slides, or can be used for 
 enlarging purposes with the help of the lantern, which has 
 induced me to give this brief notice of them in my chapter 
 on lantern accessories. 
 
CHAPTER XIX. 
 
 PRACTICAL HINTS TO THOSE WHO EMPLOY THE LANTERN FOR 
 SCIENTIFIC DEMONSTRATION, OR FOR ENTERTAINMENTS IN 
 THE DRAWING-ROOM OR LECTURE-HALL. 
 
 IN the foregoing pages I have endeavoured to 
 describe the best methods of manipulating the 
 lantern ; and I hope that I have done so in such 
 a manner as to enable all my readers readily to under- 
 stand the working of this beautiful instrument. I feel 
 convinced that if my instructions are carefully followed 
 all will go well, — at all events, in the apparatus depart- 
 ment. But the best instrument is no good unless the 
 lecturer be an efficient showman and speaker. Unfor- 
 tunately many essay the task of lecturing who are physi- 
 cally unfit for it. There are many good-natured people in 
 the world who will undertake, very often for some charity, 
 to act as lecturer in a school-room, the slides being 
 borrowed from some optician with a printed lecture fitted 
 to them. This good-natured man will take up the work 
 without much thought or consideration, and the result is 
 too often a very bungling performance. A man may have 
 
THE BOOK OF THE LANTERN. 
 
 265 
 
 a fund of knowledge, but lack the power of imparting it to 
 others. The fault is common enough in the pulpit, where 
 it is often the case that a clergyman who has won high 
 honours at the university, and as a reward for his scholar- 
 ship finds himself in due course incumbent of a living, is 
 an utterly incapable speaker, greatly to the distress of his 
 congregation. He can of course compile or write a good 
 sermon ; that is to say, a discourse which is carefully con- 
 structed and perfect as a specimen of written English ; but 
 when he gets into the pulpit he reads it out in such a 
 droning voice, and with such a lack of emphasis, that many 
 of the congregation dose off into peaceful slumber. Many 
 lecturers have the same want of ability, and it is this 
 circumstance that has had the effect more than any other 
 of prejudicing people against a lecture, as a thing which is 
 necessarily dull and the reverse of entertaining. 
 
 More than once it has fallen to my lot to lecture in some 
 hall which is strange to me, and on such an occasion 1 have 
 generally asked the hall-keeper if a large audience may be 
 reasonably looked for. The answer is too often something 
 like this : — " Well, sir, the people hereabouts don't much 
 care for a lecture ; but last Saturday night the place was 
 crowded from floor to ceiling." " Dear me ! " is my answer, 
 " and who was the lecturer on that occasion ? " " Lor' 
 bless your soul, sir, it wasn't no lecture, it was niggers." I 
 leave my readers to imagine with what feelings I looked 
 forward to the pleasure of meeting my audience. 
 
 A lecture entertainment will fail sometimes owing to the 
 total incapacity of the speaker, — to his bad articulation, 
 nervousness, lack of voice, or want of tact in dealing 
 
266 
 
 THE BOOK OF THE LANTERN. 
 
 with the audience. Still more often failure is due to bad 
 arrangement of the matter which the lecturer has under- 
 taken to. deliver. The remedy for this last fault is 
 obvious, namely, a course of training in the reading of 
 standard works. Some may perhaps think I am recom- 
 mending an old-fashioned book, when I name " Blair's 
 Lectures on Rhetoric," as a very valuable aid to the writer 
 and speaker. I would advise all beginners to write their 
 lectures and go over the matter again and again, before 
 trusting themselves on the platform ; and in constructing 
 the fabric of their discourse, let them remember that the 
 sentences should be as a rule shorter than if the words were 
 merely intended for the eye of a reader. A sentence con- 
 sisting of several lines without any full stop, although it 
 may pass in ordinary composition, is very tiresome to listen 
 to ; a most attentive audience will, by the time the verbose 
 paragraph ends, forget its opening, and the sense be 
 consequently lost. Again, in composing a lecture which 
 is illustrated by lantern pictures, care must be taken to so 
 arrange it that the pictures come in naturally, and are not 
 dragged in willy-nilly, as if they were in stock and must be 
 shown at any price. The views should be the best of their 
 kind, but must be altogether subservient to the text. If a 
 part of the subject is of such a nature that it may be likely 
 to prove tedious to an audience, — and audiences differ 
 amazingly in their receptive faculties,— that part should 
 either be compressed, or it may be lightened by a good anec- 
 dote, or even by some illustration which will raise a laugh. 
 Such pictures introduced with circumspection are most 
 useful ; but the power of employing them should be used 
 
THE BOOK OF THE LANTERN. 
 
 267 
 
 sparingly. Let the lecturer look upon them as the high- 
 lights of a work of art. The novice with a brush will daub 
 such high-lights on every projecting corner of the compo- 
 sition, until the beauty of the whole is lost in their glare ; 
 a true artist, on the other hand, will deftly put in a touch 
 here and another there, with the result that the whole work 
 is brightened and generally improved. 
 
 The grosser faults into which a novice in lecturing is 
 apt to fall are generally the result of simple inexperience 
 or carelessness. He should make it a golden rule that 
 whatever may occur he must not lose his temper. In the 
 ordinary affairs of life, the man who can control his temper 
 has always the best of an argument ; and still more so is 
 this the case on the platform (and on this platform, let 
 us remember that there are often some very trying inci- 
 dents to deal with, particularly amid the darkness of 
 lantern illustrations). I once found it very hard to control 
 both my sentences and my temper, when I became aware 
 that I was a target for some mischievous boy's pea-shooter ; 
 but on politely addressing the unseen youth, and telling 
 him that I knew he was a very smallhoy, and that therefore 
 I could excuse his childish conduct, but at the same time he 
 must keep his peas in his pocket, the nuisance stopped. I 
 recently heard of a case where an inexperienced lecturer 
 was loudly told more than once to " speak up." Instead of 
 taking this invitation as a valuable hint, and acting upon 
 it as he should have done, he retorted rudely, and the audi- 
 ence refused to listen to him any longer. It is to be hoped 
 that he will not again attempt work for which he is 
 evidently quite unfitted. 
 
268 
 
 THE BOOK OF THE LANTERN. 
 
 Iii lectures of a popular and entertaining character, 
 it is often desirable to introduce a little music; but if 
 this is done at all it should be done well, the lecturer first 
 of all satisfying himself as to the capabilities of the 
 musician. They should then arrange together where the 
 music is to come in, and the player should have furnished 
 to him by the lecturer a set of cues, with hints as to the 
 nature of the music to be played at the occurrence of those 
 particular words. To show that this precaution is not an 
 idle one, let me state that recently I heard a lecture de- 
 livered in which a few bars of music came in at stated 
 times. On one of those occasions the lecturer was showing 
 a tomb erected to the memory of some celebrity who had 
 recently departed. He described this tomb and said a few 
 touching words with reference to the high character of the 
 departed one ; and, he had no sooner finished, than the 
 pianist at his elbow struck up a merry waltz ! 
 
 The lecturer should be careful to select an intelligent 
 open tor. The man employed should be one capable of 
 concentrating his attention upon the work which he has 
 to do. The gases will require attention, the lime wants 
 turning every few minutes, or the light from the lantern 
 soon drops ; but, at the same time, too much should 
 not be thrown upon the hands of the operator; for in- 
 stance, the lecturer* should make it a standing rule to go 
 carefully through the slides which are to be shown before 
 the lecture commences, so that each one is not only in its 
 proper place, but each is so arranged that the operator will 
 hardly be able to put one in the lantern except in its right 
 position. A landscape, or more especially a portrait, ap- 
 
THE BOOK OF THE LANTERN. 
 
 269 
 
 pearing suddenly on the sheet standing on its head, is an 
 episode which disturbs both lecturer and audience, and 
 will, for a time, entirely break the thread of the discourse. 
 This can easily be avoided if the slides be marked in a 
 certain way. If the slides are being used in fixed carriers, 
 and are therefore simply' in the form in which they are sold 
 at the shops, each one should be marked with a white disc 
 at the lower left-hand corner of the picture, taking care 
 that the wafer is on the face of the picture, and by pre- 
 ference, beneath the cover glass, so that it cannot be rubbed 
 off. This white wafer will then come conveniently below the 
 operator's thumb when the slide is in its inverted position, 
 as it should be, before being placed in the lantern. 
 The operator will then become accustomed to look for this 
 white dot, which he can easily see even in a darkened 
 room, and he will place his thumb above it, and the picture 
 will of necessity appear on the sheet, as it should do. Tf 
 the back of the picture is placed next the light, of course 
 everything on the sheet appears in reversed order. What 
 should be the right hand of the picture appears on the left 
 of the sheet, and vice versa. This is of no great conse- 
 quence in some cases ; but if the picture should include 
 any lettering, such as that on a sign -post or a shop-front, 
 these letters will appear backwards, and the fault is at 
 once detected by the audience, and commented on by them 
 in audible whispers. I once had a volunteer assistant who, 
 at short notice, supplied the place of my regular operator, 
 who happened to be ill. In the middle of my lecture this 
 man showed a slide upside down ; on seeing his mistake, 
 he took it out of the lantern and put it in again sideways. 
 
2 70 
 
 THE BOOK OF THE LANTERN. 
 
 He again saw the error, took it out of the lantern, and re- 
 placed it, but on its other side ; so, in reality, this genius 
 tried every conceivable way of showing 
 that picture but the correct one. 
 
 It is imperative that there should be 
 some well-understood code of signals be- 
 tween the lecturer and the lantern operator, 
 for. in many cases they are 50 feet apart. 
 
 Some lecturers are content with verb; 1 
 directions, but these are simply intoler- 
 able to any one with any idea of what 
 a lecture should be. To hear a man 
 calling out, " Next picture, please," and 
 so on, utterly spoils even a lecture which 
 is good in other respects. An audible 
 sound signal, such as tapping with a 
 pointer, or sounding a gong when the 
 picture is required to be changed is 
 almost as bad. A lecture lamp has 
 recently been introduced, which not only 
 comprises a shade light for the lecturer's 
 desk, but has at the back, i.e., the side 
 presented towards the audience, and there- 
 fore towards the lantern, a little disc of 
 red glass, which is uncovered by touching 
 a lever at the side of the lamp. See S, 
 .xg. 7 4. When the operator sees the little red flame dis- 
 closed he knows that a fresh picture is wanted, and should 
 he be inattentive to that signal there is a little gong, B, below 
 the lamp which can be used on such an emergency. This 
 
 Fig. 74. 
 
THE BOOK OF THE LANTERN. 
 
 271 
 
 lamp is portable, convenient, and efficient. But above all 
 devices for signalling I prefer a simple electric arrange- 
 ment. The one that I am in the habit of using consists of 
 a single-stroke electric bell with the gong removed from it. 
 When the current is sent through the coils of the attached 
 magnet, the armature is of course attracted, and a little 
 tap is heard, which, although quite unnoticed by the 
 audience, is easily heard by the operator, who is on the 
 look out for it. I used to employ in connection with the 
 bell, — if bell it can be called, — a Leclanche battery which 
 was placed just below my reading-desk. While on the 
 desk itself I had an ordinary bell push, connected with 
 both bell and battery. But this arrangement I have since 
 superseded by a better one. The Equitable Telephone 
 Company have brought out an electric bell which is quite 
 independent of battery power, a small magnetic arrange- 
 ment taking its place. This generator, as it is called, is 
 shown at fig. 75. It acts most perfectly, and is destined, 
 I should presume, to work a revolution in electric bell 
 mechanism generally. The only inconvenience in the 
 arrangement is the difficulty that is sometimes found in 
 carrying the wires between the lecturer and the lantern, 
 and so concealing them or putting them out of reach 
 that there is no chance of their being tampered with by 
 mischievous hands. In a lecture theatre, where there is 
 commonly a gallery, the wires can be run round the 
 front of the balcony quite out of sight. In other cases 
 they can be laid on the floor underneath the carpet or 
 matting. In nine cases out of ten there is no difficulty 
 in adjusting them. The signal should be given about 
 
272 
 
 THE BOOK OF THE LANTERN. 
 
 half a minute before the change of picture is really 
 required, so as to give the operator time for the necessary 
 manipulation. He should be instructed when to dissolve 
 the view slowly, should he be using a double or triple lan- 
 tern, and when to make the change quickly. To dissolve a 
 diagram or a portrait is ridiculous, and sometimes leads to 
 
 Fig. 75. 
 
 very comical effects. I remember once attending a lecture 
 where a number of illustrations were shown of different 
 types - of national costumes. First of all there came a 
 woman in peasant's dress. This was followed by a man 
 whose lower extremities were clothed in tight-fitting white 
 unmentionables. It so happened that one figure occupied 
 on the screen exactly the same place as the other, so 
 
THE BOOK OF THE LANTERN. 
 
 273 
 
 that when the lady was slowly dissolved into the gentle- 
 man, the astounding effect was produced of her clothes 
 gradually melting from her form. 
 
 I must now bring my remarks to a conclusion, with 
 the hope that many will find my book useful. If the 
 word Ego has crept in with too much persistence, I trust 
 that my indulgent readers will impute it rather to personal 
 acquaintance with the things of which I write than to any 
 less worthy source. 
 
INDEX. 
 
 Advantage of pure hydro- 
 gen, 69. 
 Aniline colours, 161. 
 A phengescope, 246. 
 Astrometeoroscope, The, 180. 
 
 Bell, Electric, 271. 
 BiuDial, Detachable, 13. 
 Biunial lantern, 8. 
 Blow-through jet, 53. 
 Boards, Double, 62. 
 Brass work, Superfluous, 10. 
 Brewster, Sir David, 5. 
 Brin's Oxygen method, 46. 
 
 Cameras, Detective, 260. 
 Camera for microscope, 215. 
 Cameras, Hand, 259. 
 Capacity of cylinders, 49. 
 Carriers, 250. 
 Cellini, 1. 
 
 Choreutoscope, The, 180. 
 
 Clamp, Steward's, 56. 
 Clouds, 164. 
 Clouds, Printing, 233. 
 Cohesion figures, 175. 
 Collodio-bromide process 111. 
 Colosseum, 1. 
 Coloured gelatine, 188. 
 Colouring lantern slides, 145. 
 Colours, Complementary, 166, 
 188. 
 
 Colours used for slide painting, 
 149. 
 
 Complementary colours, 166, 
 188. 
 
 Compound frame for copying, 
 126. 
 
 Compressed oxygen, 48. 
 Condenser, Dallmeyer's, 23. 
 Condensers, 21. 
 Copying apparatus, 124. 
 Copying paper prints, 121. 
 Current reverser, 173. 
 
276 
 
 INDEX. 
 
 Cutting masks, 142. 
 Cylinders, Capacity of, 49. 
 Cylinders for gas, 48. 
 
 Dallmeyer's Condenser, 23. 
 Decomposition of water, 192. 
 Desk for slide painting, 148. 
 Detachable biunial, 13. 
 Detective cameras, 260. 
 Developers, 120, 121. 
 Development, 119. 
 Development of photograph in 
 
 lantern, 199. 
 Dissolver, 9, 80. 
 Distance between lantern and 
 
 sheet, 95. 
 Distances, Table of, 96. 
 Double boards, 62. 
 Drummond Light, 5. 
 Drying-rack, 136. 
 Dry plate slides, 109. 
 
 Easel for enlarging, 224. 
 Electric Bell, 271. 
 Emulsion, Filtering, 132. 
 Emulsion making, 128. 
 Enlarging lantern, 239. 
 Enlarging photographs, 222. 
 Enlargements, 209. 
 Equivalent focus, 95. 
 Ether-oxygen light, 83. 
 Experimental lantern, 190. 
 Experiments with tank, 193. 
 Exposing gauge, 229. 
 Exposure, 117. 
 
 Exposures for enlargements, 
 228. 
 
 Filtering Emulsion, 132. 
 Frame for sheet, 93. 
 Frogs' legs, Projection of. 
 174. 
 
 Gas-bags, 58. 
 
 Gas bottles or cylinders, 48. 
 Gelatine process, 115. 
 Gelatino-bromide paper, 225. 
 Gelatino-chloride plates, 133. 
 Glass grinding, 101. 
 Ground-glass lantern slides, 
 99. 
 
 Ground-glass varnish, 102. 
 Gauge for exposures, 229. 
 
 Hand Cameras, 259. 
 Hanging the sheet, 88. 
 Hints, Practical, 2^4. 
 Home-made gelatine platen 
 127. 
 
 Hydrogen generator, 69. 
 
 Ice experiment, 197. 
 Iceland Spa, 187. 
 Intensifying, 140. 
 
 Jet, Blow-through, 53. 
 Jet, Mixed, 53. 
 Jet, Oxycalcium, 50. 
 
 Kaleidotrope, The, 179. 
 Kircher, 3. 
 
 Lamp, Newton's, 6. 
 Lantern and Photography, 
 The, 204. 
 
INDEX. 
 
 277 
 
 Lantern, Binnial, 8. 
 Lantern enlarging, 239. 
 Lantern enlargements, 209. 
 Lantern for experiments, 190 
 Lantern, How to work, 76. 
 Lantern le^'S, 256. 
 Lantern microscope, 240. 
 Lantern, Mineral Oil, 7. 
 Lantern, Opaque, 244. 
 Lantern-slides, 97. 
 Lantern-slide colouring, 145. 
 Lantern - slides from paper 
 
 prints, 121. 
 Lantern slides on dry plates, 
 
 109. 
 
 Lantern-slides on ground 
 
 glass, 99. 
 Lantern-slides on wet plates, 
 
 104. 
 
 Lantern- slides with transferro- 
 
 type paper, 143. 
 Lantern, Triunial, 15. 
 Lecture-lamp, 270. 
 Lenses, Condensing, 21, 23. 
 Lenses, Objective, 26, 27. 
 Lens, Supplementary, 22. 
 Limes, 71. 
 Lime -shield, 57. 
 Limes, Preserving, 74. 
 
 Magnetic experiments, 201. 
 Making emulsion, 128. 
 Making oxygen, 30 
 Masks, Cutting, 142. 
 Micro, Attachment, 220, 242. 
 Microscope, Camera for, 215. 
 Microscope, Lantern, 240. 
 Mineral oil lantern, 7. 
 
 Mixed jet, 53. 
 Mixture, Oxygen, 40. 
 Moonlight pictures, 159. 
 Mounting, 141. 
 
 Newton's Lamp, 6. 
 
 Oakley's regulator, 64. 
 Objective lenses, 26, 27. 
 Opaque lantern, 2 14. 
 Opaque lantern, principle 
 
 of, 2. 
 Optical system, 16. 
 Oxycalciurn jet, 50. 
 Oxygen, Briu's method, 46. 
 Oxygen, Compressed, 48. 
 Oxygen-ether light, 83. 
 Oxygen making, 30. 
 Oxygen mixture, 40. 
 Oxygen retort, 32. 
 
 Painting with aniline colours, 
 161. 
 
 Photographs, Enlarging, 222. 
 Photo-micrographs, 211. 
 Portable fiame, 93. 
 Practical hints, 264. 
 Preserving limes, 74. 
 Pressure boards, 60. 
 Primitive lime-light, 51. 
 Printing clouds, 233. 
 Prism, The, 182. 
 Pure hydrogen, Advantage of, 
 69. 
 
 Purifier, or Wash-bottle, 37. 
 
 Rack, Washing, 136. 
 Regulator, Oakley's, 64. 
 Retort, Oxygen, 32. 
 I 
 
278 
 
 INDEX. 
 
 Sand - glass, Projection of, 
 175 
 
 Sciopticon, 6 
 Screens, 86 
 Sheet, Hanging, 88 
 Short-focus lens, 138 
 Signalling, 271 
 Simple regulator, 68 
 Sir David Brewster, 5 
 Sky, Treatment of, 139 
 Slides by contact, 137 
 Spectrum slides, 186 
 Steward's clamp, 56 
 Steward's regulator, 68 
 Superfluous brasswork, 10 
 Supplementary lens, 22 
 Support for lantern, 256 
 
 Table of distances, 96 
 Tank experiments, 193 
 Tannin process, 110 
 The Astrometeoroscope, 180 
 The Choreutoscope, 180 
 
 The Galvanometer-slide, 171 
 
 The Kaleidotrope, 179 
 
 The Prism, 182 
 
 "Toilers of the Thames," 
 
 Frontispiece. 
 Treatment of sky, 139 
 Triunial dissolrer, 81, 82 
 Triunial lantern, 15 
 Tubes, 76 
 
 Tyndall's ice experiment, 197 
 
 Use of condenser, 18 
 
 Vertical attachment, 12 
 Vortex rings, 191 
 
 Wash bottle, or purifier, 37 
 Water, Decomposition of, 192 
 Wet Collodion-slides, 104 
 Whitewashed screen, 91 
 Woodbury-type process, 113 
 Working the lantern, 76 
 
READ WHAT PROMINENT 
 
 AMATEURS 
 
 SAY OF THE 
 
 SUTER LENS. 
 
 MESSRS. ALLEN BROS. New York, February 20, 1889. 
 
 Dear Sirs : You ask me to give you my opinion of the Suter Lens 
 bought of you three or four years ago. It gives me pleasure to write 
 you that it is my favorite lens for out-of-door work — I have eight of 
 various makes. It works rapidly, and has great depth of focus. 
 
 Yours very truly, 
 
 R. Swain Gifford. 
 
 MESSRS. ALLEN BROS. New York, February 20, 1889. 
 
 Dear Sirs : I am glad to write you that the No. 4 B Suter Lens, 
 which I bought of you some time ago, is very satisfactory. It is about 
 
 as quick as my lens, and is very sharp focus. I use it almost 
 
 entirely in my studio. Yours very truly, 
 
 Louis C. Tiffany. 
 
 From t lie Balloon Photographer. 
 
 Messrs. Allen Bros. Winsted, Ct., November 26, 1886. 
 
 Although circumstances compelled me to give up my projected bal- 
 loon trip this fall, I have used my 3 A " Suter " for other work, photos 
 of animals, viewing, etc. I am glad to say that each time I have used 
 it, it has impressed me with a stronger sense of its good qualities. 
 With your Lens and a Prosch Duplex Shutter, which is fitted to it, I 
 feel well equipped for quick work and feel confident of success in my 
 next balloon trip whenever that is. 
 
 Very respectfully, 
 
 John G. Doughty. 
 
 ALLEN BROTHERS, 
 
 DETROIT, MICH. 
 
 Sole Agents for the United States. 
 
VALUABLE INFORMATION 
 
 for Lantern Slide Makers and Lovers of the Magic Lantern, 
 and everybody in general. 
 
 THE LILLIPUT 
 
 IDEAL DETECTIVE CAMERA. 
 
 NEAT, 
 
 COMPACT, 
 
 SIMPLE. 
 
 Uses ordinary Dry Plates 
 2}i inches Square. 
 
 Lantern Slides can be made from these small negatives 
 and thrown np on the screen to almost any size. 
 
 Size of Camera, 4x4x6 Outside Measurement. 
 
 Illustrated Book of Instructions accompanying each Camera. 
 
 A fine sole-leather case and sling strap, six patent 
 double dry-plate holders, a non-actinic lamp, and dry 
 plates for 108 exposures are included with this Camera, 
 and the price is only $25.00. 
 
 SEN D FOR CIRCU LAR. 
 
 E. & H. T. ANTHONY & CO., 
 
 Nd. 891 Broadway, New York. 
 
 (280) 
 
ESTABLISHED 1870. 
 
 MAGIC LANTERNS 
 
 S. HAWK RIDGE, 
 
 Stevens Institute of Technology, 
 HOBOKEN, N. d. 
 
 Manufacturer of Apparatus for Projection, Magic 
 Lanterns, etc, including the 
 
 COLLEGE LANTERN, 
 
 with Vertical, Microscopic, and Polarizing Attach- 
 ments. 
 
 Oxyhydrogen Apparatus, Gas Generators, Wash 
 Bottles, Steel Cylinders, Gauges, Patent Pressure 
 Regulators. 
 
 High and Low Pressure Dissolving Keys, Patented 
 May 22, 1888. 
 Spectrum Analysis with Electric Light. 
 Automatic or Hand Regulators. 
 
 Also Apparatus for the Illustration of the Principles 
 of Light and Sound, by A. M. Mayer, Ph.D. 
 Wales' Microscopes and Lenses. 
 Spectroscopes and Spectrometers. 
 
 MAGNESIUM, FLASH, AND RIBBON LAMPS, 
 
 (Hand and Automatic), Patents Applied for. 
 
 Correspondence Solicited. 
 
 P. O. Box 187, Hoboken* N. J. 
 
 (281 ) 
 
The Magic Lantern. 
 
 We Manufacture 
 
 STEREOPTICOtiS, 
 SCI0PT1C0NS, 
 
 AND 
 
 MAGIC LANTERNS 
 
 Gas Apparatus. 
 
 We have the exclusive 
 control of 
 
 Arnold's 
 
 Self-Condensing 
 Oxygen Retort 
 and Cylinder. 
 
 No Pumping I Does all 
 the Work Itself. 
 
 No More JLabor to 
 charge this Cylinder 
 than to fill a Gas Bag. 
 
 THE MclNTOSH-IVES SATURATOR 
 
 FOR THE PRODUCTION OF 
 
 The most Brilliant and Powerful Oxyhydrogen Lime Light. A Perfect Substi- 
 tute for Hydrogen or Coal-gas. Stored without a Gasholder, and Ready 
 at all Times. Supplied to the Blowpipe by Simple Mechanical 
 Means, without Heat. ABSOLUTELY WITHOUT DANGER. 
 Get our prices if you want a Lantern, Views, Limes, Screen, Gas, or 
 anything necessary for giving an Illustrated Lecture. We carry over 
 
 20,000 VIEWS 
 
 plain and colored, and can fill all orders on short notice. 
 
 Mcintosh battery & optical go. 
 
 141 & 143 Wabash Ave., CHICAGO^ ILL. 
 
 Send for Illustrated Catalogue. 
 ( 282 ) 
 
W. H. WALMSLEY.umis 
 
 No. 1022 Walnut Street, 
 PHILADELPHIA. 
 Opticians and Photographic Stock Merchants. 
 
 Make a specialty of Imported Lanterns. Among these the 
 Four-Wick 
 
 Pampliengos, 
 
 By Hughes, of London, and Three-Wick 
 
 Universal, 
 
 By Laverne, of Paris, are the best oil-burning Optical Lanterns 
 that we are acquainted with. 
 
 WALMSLEY'S PHOTO-MICROGMPHIC CAMERA 
 
 is an excellent, practical instrument for this purpose, very 
 largely in use in institutions of learning throughout the country, 
 and in most of the Government Departments at Washington 
 and elsewhere. 
 We also furnish 
 
 LANTERN SLIDES 
 
 from many hundreds of subjects in all departments of Natural 
 History from negatives by Mr. Walmsley. 
 
 List of same on Application. 
 
 Every description of Microscopic and Photographic Appara- 
 tus and Materials, in stock ; price lists of which will be mailed 
 on application. 
 
 W. H. WALMSLEY, Ltd., 
 1022 Walnut St., Philadelphia. 
 
 (284). 
 
For parlor or small hall exhibitions, chemical and optical experiments, etc., 
 the Laverne Lantern affords, at a moderate price, the greatest number of 
 advantages, and from its simplicity and non-liability to get out of order, gives, 
 even in inexperienced hands, results superior to ali others. 
 
 When packed for carrying, in its own Russia iron case, it measures 15 x 16 
 x 6 inches, and weighs 12 pounds ; the case serving as a convenient stand 
 when the lantern is in use. 
 
 The Case and Body of the Lantern are of Russia iron and neat and com- 
 pact in form. That part of the body which surrounds the lamp is double, the 
 outer covering being ornamentally perforated so as to allow a constant current 
 of air to circulate and keep down the temperature. 
 
 The Lamp is of the triple wick variety, and so constructed that the three 
 flames combine, and by draught of a ten-inch chimney give a brilliant white 
 flame. 
 
 The Condenser is four inches in diameter, neatly mounted in brass, 
 thoroughly ventilated, and arranged with screw flange so that the lenses may 
 be separated and cleaned when required. 
 
 The Cone, which carries the objective, and the mount of that lens are 
 nickel plated. The objective is a double achromatic lens of one and a half 
 inch clear aperture and five inch focus, so that at a distance of twelve feet 
 from the screen it gives a brilliant picture six feet in diameter. The focus is 
 roughly obtained by sliding the front carrying both cone and lens ; and fine 
 adjustment by a rack and pinion on the objective. 
 
 IMPORTED AND SOLD BY 
 
 Gayton A. Douglass <&, Co., 
 
 Merchants in 
 
 PHOTOGRAPHIC SUPPLIES, 
 
 185 & 187 Wabash Ave., CHICAGO, ILL. 
 
 (285) 
 
BENJ. FRENCH & CO. 
 
 319 Wasttirjgtoi} Street, 
 BOSTON, MASS. 
 
 Sole Agents and Importers of the Celebrated 
 
 VOIGTUNDER AND BAR LOT LENSES. 
 
 We have expressly constructed for us 
 
 Darlot Lenses in Matched Pairs 
 for the Stereopticon, viz.: 
 
 1-4 size, 4 J inch focus, each 
 1-3 » 5 J » » » 
 
 1- 2 » 7 » » » 
 
 2- 3 » 8J » » » 
 4-4 » 10J » » » 
 
 $7 00 
 12 00 
 14 50 
 21 00 
 32 00 
 
 ALSO 
 
 Darlot's Condensing Lenses. 
 
 4J inch, per pair $5 00 
 
 4£ » » 6 00 
 
 5 » » 7 50 
 
 Mounting in tin or brass extra. 
 
 f^** Our initials (B. F. & Co.) engraved on the barrel of the Darlot 
 Lenses, is a sure proof of their genuineness and superior quality. 
 
 Our complete Catalogue sent free, on application. 
 
 (286) 
 
(28 7 ) 
 
PHOTOGRAPHIC APPARATUS AND MATERIAL. 
 
 WILSON'S PHOTOGRAPHIC MAGAZINE 
 
 Is issued every first and third Saturday of the month. Every number 
 contains a handsome photo-embellishment. It is intended to advance 
 photography in the highest sense. It is published in the interest of its 
 subscribers by its editor, owner, and publisher. Its embellishments 
 and illustrations will be more numerous than ever. No magazine 
 in the world publishes so many or gives such useful photographic 
 studies. 
 
 SEND FOR PROSPECTUS AND PREMIUM LIST. 
 
 SUBSCRIBE NOW. $5.00 a year ; $3.50 for Six Months ; $1.35 for 
 Three Months ; 30 Cents per copy. 
 Specimen copy free to all who use a Camera. 
 The Best Photographic Books. Send for Catalogue. 
 
 EDWARD L. WILSON, s -ateSggHEr 
 
 853 BROADWAY, NEW YORK. 
 
 ( 288 ) 
 
r 
 
 v. 
 
 GETTY RESEARCH INSTITUTE 
 
 
 
 
 
 
 II 
 
 
 
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