^''^i:: ■'■A \t §0biJt!t p«ttt;jj ®ltttj;^tirtt ^ mn t0 1903 Aiu^-^f- f/^/bsr ^bjVO- The date shows when this volume was taken. To renew this book ropy the call No. and give to the libra rian. HOME USE RULES. All Books subject to Recall. Books not used for instruction or research are returnable within 4 weeks. Volumes of periodi- cals and of pamphlets are held in the library as much as possible.^ For -special purposes they are given out for a limited time. Borrowers should not use their library privileges for the bene- fit of other perfons. Books not needed during i-ecess periods should be returned to the library, or arrange- ments made for their return ^uring borrow- er'sabsenCe, if wanted. Books needed by more than one person are held on the reserve list. Books of special value and gift books, when the giver wishes it, are not allowed to circulate. Readers are asked to report all cases of books marked or muti- lated. Do not deface books by marks and writing. nr- CO ^nS-""^"^" University Library UO 03.Go5 Scientific handicraft; a descriptive, ill 3 1924 012 324 699 ^3 JOHN J. GRIFFIN AND SONS, MANUFACTUEEES OF IHEMICAL AND PHILOSOPHICAL INSTRUMENTS, 22, GAEEICK STEEET, COVENT GAEDEN, w.c. London, July, 1873. ^^]^tHti0it Bnit p^trals. The following PRIZE MEDALS were awarded to John J. Geietin by the Juries of THE GREAT EXHIBITION OF 1851, AKD THE INTERNATIONAL EXHIBITION OF 1862. GREAT EXHIBITION OE THE INDUSTRY OP ALL NATIONS, 1851. Class X. Philosophical Instruments. PEIZE MEDAL for Graduated Glass Instruments, exceedingly accurate and good ; and for economical and convenient Chemical Apparatus. INTERNATIONAL EXHIBITION, 1862. Class XIII. Philosophical Instkfments, and Processes depending ON their Use. PEIZE MEDAL for general excellence and cheapness of the manufacture of his Apparatus for Chemical Research. INTERNATIONAL EXHIBITION, 1862. Class XXIX. Educational Works and Appliances. PEIZE MEDAL for a good collection of cheap Apparatus for Instruction in Elementary Science. SCIENTIFIC HANDICRAFT: % gtsfrijptik, Illustrate, anir '^x'utts CATALOGUE OF APPARATUS, SUITABLE FOR THE PERFORMANCE OF ELEMENTAEY EXPEEIMENTS IN PHYSICS. JOHN JOSEPH GEIFFIN, F.C.S., AUTHOR OF "CHEMICAL EECREATIONS ;" "CHEMICAL HANDICRAFT;" ETC. VOLUME FIBST: MECHANICS, HYDEOSTATICS, HTDEODYNAMICS, AND PNEUMATICS. LONDON: PUBLISHED BY JOHN J. GKIFFIN AND SONS, CHEMICAL & PHILOSOPHICAL INSTRUMENT MAKERS, 22, GAERICK STREET, W.C. 1873. 4) A-i'^^'^^^l LONDON : PRINTED BY WILLIAM CLOWES AND SOSS, STAMFORD &TREET AM> CHARING CROSS. P.E PREFACE. The nature of this Work is fully explained in the title-page. It is " a descriptive, illustrated, and priced Catalogue of Appaeatds suitable for the performance of Elementary Experiments in Physics.'' The present volume contains the subjects of Mechanics, Hydrosta- tics, Hydrodynamics, and Pneumatics. If it meets with public approval, companion volumes wiU be published on Acoustics, Heat, Light, Electricity, Magnetism, and Galvanism. These works will be strictly practical. They will avoid theoretical disquisitions, and will relate to Apparatus and Experiments only, and especially to apparatus of a cheap character, and to experiments suitable for elementary instruction. Nearly all the Instruments and Experiments described in this volume have been made in the workshops of the Publishers, and tried in the presence of the Editor ; and the figures and descrip- tions have been drawn to agree with the Instruments that had been submitted to these special trials. JOHN J. GEIFFIN. 22, Gahkick Street, W.C. London, July, 1S73. Cornell University Library The original of tliis book is in tlie Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924012324699 ADVEETISEMENT. The Instrmnents described in this Work are offered for sale at the prices aSixed to each. These prices are nett, for ready money. The expense of packing-cases and packing-materials is charged to purchasers. We employ very careful and experienced persons to pack the instruments securely ; but we do not hold ourselves responsible for any breakage that miay take place during the carriage of the goods from our manufactory to their places of destination. The packing-cases and packing-materials are charged at the lowest possible price, and we are compelled to intimate that we cannot take them back, nor allow their value to be deducted from our bills. Orders from strangers in the country must be accompanied by a Remittance, or by a reference to some person iu London. Post-office orders are to be made payable at Chasing Ckoss. Sums under 5s. may be remitted in postage stamps. Foreign orders must either be accompanied by a remittance, or by in- structions for payment in London, on delivery of the biUs of lading, without which payment the orders cannot be executed. A large stock of the apparatus described in this work, both British and J'oreign, being kept ready for imme- diate delivery, shipping orders for comprehensive collections can be executed with promptitude. Such articles in this catalogue as are subject to frequent variations in price are at all times charged according to the lowest market value. The present prices supersede all those in catalogues of earlier date. JOHN J. GEIFFIN and SONS. 22, Garbick Street, W.O. London, July, 1873. ( i^ ) CONTENTS. MECHANICS. PAGE The Mechanical Powers . . . . i Auxiliary apparatus . . . i suspension board or black rail i schoolroom blackboard . . . . i pair of iron hooks for suspend- ing apparatus i light brass scale pans . . . . 2 weights -^ lb. each, two sorts 2 iron pins and hooks, for pulleys 2 cord suitable for pulleys . . 2 The Levek . . 2 lever with a wedge-shaped fulcrum 2 extemporised balance . . . . 3 lever for suspension . . . . 3 varieties of levers 4 lever of the first kind . . 4 lever of the second kind . . 5 lever of the third kind . . 6 Gravesende's suspended lever 6 experiments with it , . 6 The PttLLBY 7 pulley sheave, block, and axle 7 the pulley frame 7 sets of pulleys mounted . . . . 7 restrictions on the action of pulleys 7 simple pulleys, a set of four . . 7 experiments with simple pul- leys 7 moveable pulleys and fixed pulleys 7 systems of pulleys 8 pair of long three-sheave pulleys 8 pair of square three-sheave pulleys .. .. .. .. 10 White's concentric pulley . . 10 pulley frame, and set of brass pulleys 10 The Inclined Plane 10 The Wedge 11 The Wheel and Axle . . 11 Compound Wheel and Axle . , 12 The Screw 13 Small set of models of mechani- cal powers 13 Appabatcs to Illustrate the Centre op Gkavit.y . . . . 14 Centre of gravity of two paral- lelopipeds 14 of a leaning tower .. .. 14 of an irregular board . . . . 14 Centre of gravity not necessarily witliia the volume of a solid body .. 14 The equilibriste .. .. ■■ 15 The bowl-about 15 Double cone to run up an in- clined plane 15 Degrees or Stability .. .. i5 Cone for showing states of equili- brium 1 5 Inertia apparatus 16 Tin pan and dried peas .. . 16 Plumb-line 16 The pendulum 16 Experiments with the pendulum 1 7 The parallelogram of forces .. 18 Adhesion 19 Adhesion plates 19 Toys illustrative of adhesion .. 19 Percussion 19 Percussion machines 19 Laws oe FALLma Bodies . . . . 20 Attwood's Fall Machine . . . . 20 Whirling Table ok Centri- fugal Machine 22 Adjuncts for twelve experiments with the whirling table to CONTENTS. PAGE illustrate tlie laws of central forces 33 Atmospheric optic marvel . . • • 26 The gyroscope or rotating appai* ratus 27 Gyroscope with additions for va-- rious experiments 27 Gyroscopic balance 28 Gyroscopic top 28 Vibrating wire 28 Model of a centrifugal railway . . 29 Constructive mechanics, models . offourjoints 29 Parallel motion 29 Intermittent motion 29 A train of iwheels 29 Hooke's universal joint . . . . 30 Forge or tilt hammer 30 Lock and key, a model . . . . 31 Beittleness illustrated . . . . 31 Prince Eupert's drops . . . . 31 Bolognian flask 3 r Dialysis 31 Graliam's dialyser 3r Graliam's osmometer 31 Cathetometer 3T Vernier 32. Clinometer 32 Balances 32 large hydrostatic balance . . 32 balance in glass case for accu- rate weighings 33 balance for weighing small quantities up to 8 ounces in mahogany box 34 Commercial balances 34 PAGE Balance for weighing small quantities up to J ounce . . 34 for common weighings up to 2 lb 34 Weights. Accurate decimal grain weights from . 600 grains to • 10 grain, in a mahogany box 3 4 Grain weights, less accurate than the above, the series from 600 grains to i grain, in a box 34 Pound pile of avoirdupois, from I lb. to JiOz 34 ditto, in cast-iron 34 Single cast-iron weights from lib. to 28 lb 35 Accurate centigrade weights 35 Gramme weiglits from 50 grammes to 'ooi gramme .. 35 Gramme weights, less accurate than the above, for ordinary use, from 200 grammes to •01 gramme, in a box . . 35 Gramme weights, in cast-iron, in a pile, from 1000 grammes to J gramme 35 Standard gramme weights, in brass cuties 35 Graduated liquid measures .. 35 ounce measures 35 gramme measures 35 Chkomo-Lithogkaphtc Lineab Scales 36 inch scale to 40 inches .. .. 36 centimetre scale to i metre .. 36 HYDEOSTATICS. Water rises to ai level in com- municating vessels .. .. 37 apparatus, figures 201, 202, 203,204 37 apparatus, figure 205 .. .. 38 apparatus, figure 2o5 .. .. 38 apparatus, figure 207 .. .. 39, Spirit level, unmounted i .. .. 39 Spirit level, mounted in ma^ hogany 39, Level of two different liquors in communicating ves- sels 39 apparatus, fig. 213, jar with two tubes. 40 apparatus,, fig. 214, graduated pouret .. .. .. ..40 apparatus, fig. 215, U tube graduated 40 apparatus, fig. 216, ditto un- equal limbs 41 communicating, vessels for three liquids 42 determination of the sp cifio gravity of oil of vitriol and of ether 42 CONTENTS. XI PAGE Boyle's inverted U tute for estimating the speoifie gra- vities of liquids 43 phial of the four elements . . 43 Pressure of water in all direc- tions 44 apparatus, figure 221, glass globe with four tubes . . 44 pressure apparatus of metal with five tubes 45 glass pressure apparatus with four tubes 47 ineompressibility of water . . 46 why water rises in pumps . . 46 Lateral pressure of liquids . . . . 47 jar for showing lateral pres- sure 47 Barker's mill 47 tourniquet hydraulique . . . . 48 Upward pressure of water . . . . 48 fig. 231, cylinder and disK .. 49 „ 234, cylinder and bladder 49 „ 235, hydrostatic bellows 49 „ 236, 237, ditto 50 Bramab's hydrostatic press .. 50 fig. 241, glass model .. .. 51 „ 242, small brass model . . 51 „ 243, large brass model .. 52 Hydrostatic paradox 52 Pascal's hydrostatic principle 52 Pascal's apparatus as modified by Masson •• 53 Haldat's pressure appara- tus ■•54 Apparatus for weighing a cylin- der, or a cone of water, in a vessel without a fixed bottom 55 experiments with a glass cone, 10 inches long 56 determination of the capacity of the cone in ounces of water 56 weight of the column of water that fills the cone when it, is weighed with the narrow end downwards j6 weight of the column of water that fills the cone wheo it is weighed with the wide end downwards 57 paradoxical results 57 Specific gravity 57 PAGE equilibrium of solids when im- mersed in liquid 57 principle of Archimedes, viz. that every solid when im- mersed in a liquid loses a portion of its weight equal to the weight of the- liquid which it displaces . . . . 57 exhibition of differences in specific gravities 58 three liquids of different den- sities 58 three solids of different den- sities 58 experimental demonstrations of the principle of Archi- medes 59 Exhibition of various methods of estimating the specific gravity both of solids and liquids .'. 61 estimation of the specific gravity of a solid body by means of the hydrostatic balance 6r estimation of the specific gravity of a liquid by means of the hydrostatic balance . . 62 estimation of the specific gravity of a solid body by weighing it in a bottle . . 62 estimation of tlie specific gravity of a liquid by weigh- ing it in a bottle 63 Various forms of specific gravity bottles for liquids . . . . 65 prices of specific gravity bottles 65 practical remarks on the choice and use of specific gravity bottles 67 estimation of the specific gravity of a liquid, by weigh- ing in a. beaker a quantity first measured by a ijipette 69 Mohr's hydrostatic balance for the rapid estimation of the specific gravity of liquids.. 69 Mohr's method of estimating the specific gravity of a solid by measuring the water it displaces 71 Nicholson's hydrometer for taking the specific gravities of minerals and other solids 72 Xll CONTENTS. PAGE The Htdeometee 73 Eatimation of the specific gravity of liquids by means of the hydrometer . . . . 73 Tarious forms of the glass hydrometer 74 trial jars for the liquors to be tested 74 detailed accouirt of the treat- ment of percentage solu- tions, especially those of al- cohol 75 results of trials by the bottle . . 75 necessity for rapid testing in business 76 characteristics of the different forms of hydrometers . . . . 76 and of trial jars 76 PACE varieties of hydrometer scales 77 specific gravity scales . . . . 77 Twaddell's scale ... .. .. 77 Baume''B scale 77 chemical percentage scales . . 77 scales adapted for use in hot climates 77 rules to be observed in Ubing hydrometers 78 Price list of a few hydrometers 78 Flotation 79 estimation of the weight of floating bodies by the mea- surement of the water they displace 79 equilibrium of a floating body 80 HYDEODTNAMICS. Capillaeitt 81 Apparatus for expeiiments on capillary action 82 CapiUary tubes 82 Capillary plates 82 Pressure of Liquids peopoh- tionate to Depth .. .. 83 Spouting jars for Torricelli's experiment 83 The Pipette 83 Varieties of pipettes . . . . 84 Price list of pipettes . . . . 85 The burette, a modiflcation of the pipette 85 Price list of burettes .. .. 86 Toys founded on the prin- ciple of the pipette .. .. 87 The mysterious funnel . . . . 87 The magic can 88 Houdin's inexhaustible bottle 88 The Stphon 89 Great variety of forms . . . . 89 Action of the syphon ex- plained 90 Toy syphons 92 Tantalus's cup 92 Hempel's syphon 92 Eye fountain . . 93 Price list of syphons .. .. 93 Glass Sybinges 93 Glass models of Pumps . . . . 94 Lift pump, a glass model . . 94 Force pump, a glass model . . 94 Force pump, another glass model 95 Fire engine, or double force pump, in glass 95 Fire engine, in metal . . . . 95 Models op Pumps, Glass, Brass Mounts 95 Valves, five varieties . . . , ^5 Lift pump, glass and brass . . 96 Force. pump, glass and brass 97 Pump stand, mahogany ,. 97 Tate's school lift pump . . 97 Wiy water rises in pumps . . 97 Speixgs AND Fountains .. .. 97 Classification of springs and fountains 97 Fountain produced by a fall ■of water under common atmospheric pressure .. 98 when condensed »air forces a jet into free air . . . . 99 ■a. Glass fountain .. .. 100 6. Large zinc fountain .. 10 1 c. Small brass fountain .. loi d. Set of four jets .. .. 10 1 B. The chromatic fire-cloud 102 Fountains producedwhen un- CONTENTS. XIU PAGE FOVNTAINS condensed air forces a water jet into an exhausted receiver 102 Fountains in vacuo .. .. 102 Fountain in vacuo with trans- fer plate 103 Fountain in vacuo, without transfer plate 102 Heron's ball 103 Heron's fountain, in glass .. 104 Heron's fountain, another pattern 104 Heron's fountain, in metal .. 105 The syphon fountain . . . . 105 Intermitting spring, in glass 107 Intermittmg spring, another variety 107 Waterworks 108 Water-wheels, undershot, over- shot, and hreast-vvheels . . 108 Archimedian screw, in metal 109 Archioiedian screw, in glass 109 Appold's centrifugal pump . . 109 PNEUMATICS. AlB-PDMPS Ill Varieties and powers of air- pumps in Pump with two vertical barrels 114 Another, of larger, size, with raised plates 115 Tate's single-barrel pump on solid clamp 115 Details of the construction of Tate's pump 116 Comparison of Tate's pump with pumps having double barrels 119 Experiment of the freezing of water 120 Experiment of the fountain in vacuo 120 Tate's pump, mounted on a pedestal 121 Tate's pump, mounted on a table support 122 Extra pump-plate 122 Tate's air-pump of large size 123 Air-pump with three barrels 124 Large Tate's air-pump, moved by circular action with iiy- wheel .. 124 Small single-barrel air-pumps 126 Comparative labour that at- tends the working of these pumps 126 Care of -an air-pump .. .. 127 Air-Sykinges 127 Exhausting syringes .. .. 127 Condensing syringes .. .. 128 Exhausting and condensing syringes 128 Ditto, with clamps .. .. 128 Extra Fittings foe Tate's Pump 128 Extra joint with screw .. 128 Arm to carry a syphon-gauge 128 Extra pump plates .. .. 129 Connecting tubes, &o., for separate plates 129 Syphon gauges, three kinds 129 Stopcocks, Cosueotoes, and Fittings foe Occasional USE 130 Stopcocks 130 Connectors, with i, 2, 3, or 4 screws 131 Caps for jars 132 Washers 132 Joints and connectors for tubes 132 Blocks for a table 133 Ground-plate and hook .. 133 Plate and sliding rod .. .. 133 Clip and weight 133 Single transfer plate .. .. 133 Experiments with it .. .. 133 Double transfer plate .. .. 134 Aurora BoreaUs apparatus 135 Clamps and keys 135 Tallow-holder 135 Grooved plate to secure draught of air 136 X17 CONTENTS. EXPEEIMENTS ON THE PEOPEETIES OF AIE. In Eotje Groups. PAGE Group A. — On the Weight anld Resistance of Air .. .. 136 Estimation of the speciEc gra- vities of gases 136 Description of apparatus . 137 "Weight of air proven .. . 138 Comparative weights of hy- drogen and carbonic acid gases 139 Balloons 139 Baroscope, or cork and ba- lance weight 140 Water hammer 141 V-formed water hammer .. 141 Fork-shaped water hamm er . . 1 42 Guinea and feather experi- ment 142 Brass- work for it 142 Glass cylinders for it .. ., 142 Long tube for It 143 WindmiU 143 Group B. — On the Expansion 0/ Air .. 144 Bulb gauge and glass jar . . 144 Pairof narrow bottles for test- ing exhaustion 145 liungs glass 146 Extrication of air from various bodies 146 From spring-water . . . . 146 From the pores of plants . . 146 From cork 147 From beer or ale . . . . 147 From an egg 147 From coke 147 Elasticity of air in an egg . . 147 Fruit and taper stand . . . . 148 The apple cutter 148 Bladder experiments . . . . 148 Preparation and care of blad- ders 148 Expansion of caoutchouc balls 149 Bladder frame and lead weight 149 Glass breaking squares .. 150 Cage for use with ditto.. .. 150 PAGE Paper smoke-jacks 150 Bells to be rung in exhausted receivers 150 Bell experiment that fails .. 150 Experiment that succeeds . . 151 Leslie's apparatus for freezing water 152 Evaporation In vacuo .. .. 153 Group C. — On the Pressure of Air 154 Downward pressure of the air 154 Filter cup for mercury shower 154 Shower of air in water . . . . 155 Handglass 155 Bladder glass 156 "Weight of the atmosphere .. 157 Crushing power of atmosphe- ric pressure 15 7 Upward pressure of the air . . 157. Inverted glasses of water . . 15 7 Bottle with perforated bot- tom 158 Syringe and lead weight . . 158 Three-globes experiment . . 159 Fire syringe 159 Bottle imps, or Cartesian devils' 160 Magdeburg hemispheres .. 161 Diving-bell 162 Group D. — On the meastirement of Atmospheric Pressure .. 163 The Baeojieter 163 Prices of fittings for barome- tric experiments .. .. r63 The Torricellian experiment 163 How to fill a barometer tube with mercury 164 Support for a barometer tube 164 Scale to measure the height of the mercury in the ba- rometer i65 Syphon barometer .. .. 166 Deduction of the weight of the atmosphere from the Torricellian experiment .. 167 UUJNTJaJNTB. XV Mercury can be raised in a barometer tube by atmo- spheric pressure 167 'Mercury is supported in the barometer by the pressure of the atmosphere, and it sinks in the tube when that pressure is removed .. .. 168 The elasticity or spring of the air is equal to its compress- ing force 169 Mariotte's apparatus; his law 169 Mariotte's apparatus con- structed ito show that under the pressure of two atmospheres ^air is com- pressed into half its ordi- nary bulk 170 Mariotte's apparatus con- structed to show that under the pressure of half an at- PAGE mosphere, air expands to twice its ordinary volume 171 Glass Receivers fok Aie- PUMPS 172 Scale of dimensions and prices' 174 Plat receivers for air-pumps 1 74 Cylindrical receivers . . . . 1 74 -Bell- shaped receivers .. .. 175 Bell-shaped receivers with uecks 1 75 Cylindrical receivers with necks 176 Conical fountain glasses . . 1 76 Guinea and feather glasses . . 177 Tall plain jars 177 Tall cylindrical receivers . . 177 Miscellaneous glass fittings . , 178 Index 181 MECHANICS. THE MECHANICAL POWEES. I . In the explanations of tlie properties of the Mechanical Powers, usually given in elementary works, it is taken for granted that rods, poles, planes, ropes, &o. are destitute of weight, free from rough- ness, from adhesion, and some other physical properties. But when the student comes to handle the apparatus, and to perform experi- ments with it, he finds that he must deal with all these impediments; and it is our business, in ' Scientific Handicraft,' to show him the means of overcoming them, and thereby rendering the experiments successful. We begin by describing some pieces of apparatus that serve to facilitate operations with pulleys, levers, and other mechanical powers. 2. Suspension Board, or Blade Bail, by which levers, pulleys, and other mechanical models arc to be suspended from the top of the usual schoolroom blackboard. Size of the black raU : 4 feet long, I inch thick, 4 inches broad, with two brackets to hang it on the blackboard, and brass pins and holes to receive the other apparatus. In the following figures of levers and pulleys, the suspension rail is marked c d. Figure 2, price 5». The schoolroom blackboard should measure 4 feet in width to fit the rail, and 4 feet from top to bottom to give room for chalking upon it the results of the experiments made with levers, pulleys, cords, &o. 3 . Pair of Iron Eoohs to keep the schoolroom blackboard in an upright position on the easel, in order to permit the apparatus to hang truly vertical from the suspension rail. 2s. MECHANICS. 4, Liglit Brass Scale Pans, fig. 4, for tolding weights aud coun- terpoises, in experiments made -witli levers and pulleys. See Nos. 20 to 37. Set of three pans in a box, 2s. 5. Weights. — A set of 16 zinc weights, eacli -jig- lb. avoirdupois. Four of them have wires of suspension (fig. 6), the others have slots (fig. 7), so that they may be placed on any one of the wires to increase the weight. See figs. 6, 7, and 10. Set of 16 weights, in tiDO boxes, 7 s. 6d. 6, 7. These weights are to be used in all experiments with levers, pulleys, and other mechanical powers. Whenever, in the following descriptions and figures, the word weights, or the contraction ids. is used, it refers to these weights of -jL lb. each. 8. Iron Pins and Hoolcs of two kinds (fig. 8 A and b), for at- taching pulleys, &o. to the suspension hoard, &c. The wire of these pins is -J- inch diameter, and they have sharp points. P^r dozen in a box, i^. 9. Cord fit for use with the pulleys, per packet, IS. The Lever. 10. Lever with a Wedge-shaped Fulcrum. — This lever (fig. 10) is 4 feet long, f inch thick, and 2 inches wide. It is divided in the upper side into eight equal parts, and has eight brass suspension rings below. The fulcrum (/) is wedge-shaped, 6 inches high, and 2 inches wide. The whole is made of hard wood, stained oak colour. Price, without the weights shown in the figure, is. 6d. -^ ^ II. The weights of yij lb. each {N'o. 5) are used with this lever, and may be either placed on the upper part of the lever as THE LEYEB. 6 shown by c, d, or suspeadecl from tte tmder side of the leyer as BhofsTi at a, 6 ; the weights with slots, X o. 7, are used in one ease, and those with wires, Xo. 5, in the other case. Equilibriinn is produced by applying more or fewer weights, according to the respective distances of the weights from the fulcrum or poiat of support. Fig. 10 shows two sets of weights in equilibrium: the pile d, consisting of 3 weights of ^ lb. each, placed on the first mark from the point of support, /, may be reckoned 30. The single weight of -j^j lb., c, placed on the tJdrd mark from the centie may be called 30; and these are in equi li brium. Then, referring to the suspended weights, the single weight, a, suspended from the tldrd division of the lever maybe called 30, while the three weights, h, susjiended from the first division, may also be called 30 ; and these are therefore also in equilibrium. Any fuuther weight, how- ever small, added to these, oversets the equilibrium, and causes the lever to descend on the side that is overweighted. 12. If the lever, from becoming partially damp, or from some other cause, appears to be unequally balanced when placed upon the fulcrum, it can be justiiied by sliding a bronze halfpenny, or other flat piece of metal, along the surface till it reaches the required distance from the centre. The slots in the weights c, (', figs. 7 and 10, should be made to coincide with the lines that cross the lever. If a small pair of scale pans, No. 4, are himg to the rings at the extreme ends of the lever, a balance is extemporised. If necessary, to give room for the pans, the lever can be raised higher from the table by putting the blocks, Xo. 70, or any other level piece of wood, below the wedge-shaped fulcrum. 14. Technically, one of the forces, that is to say, one of the weights or sets of weights ajjplied to a lever, is called the resist- ance, or simply the weight; while the other force is called the power. The weight represents the wort to be done : the ]jov:er is the force that is to do the work. 15. Lee er for Suspension. Price £^8. This lever is made of hard wood stained. It is 3 feet long, and about 2 inches broad. It is divided on the front into 20 parts, and is provided with holes at all the divisions, and with four pairs of rings for supporting weights as represented by fi.g. 15. It is A fl i ■ i 1 ^^ • • • ' T ! T i '^t M N ' J U ——3 15- to be suspended for use from the black rail in front of the school- room blackboard, as represented by figs. 17, 18, 19, 20, and with. B 2 4 MECHANICS. tlic help of tlie simple pulleys, Xo. 30, it serves as a lever of tlie first, second, or tMrd kind. After tlie lever is liung to the suspension rail, and before any ■weights are attached, it must be noticed whether it hangs hori- zontally or not. If defective, a bent wire must bo put on it as a rider, and moved to the place where it justifies the level of the beam. 16. Varieties 0/ Lcivrs. — There ai-e two kinds of levers, which differ essentially from one another ; namely, those on which the forces act on contrai-y sides of the fulcrum, and those on which they act on tlie same side. They are, however, usually distin- guished as of three kinds, according to the respective positions of the fulcrum, with reference to the situation of the power and of the resistance. In levers of the first kind the fulcrum is between the power and the resistance, as in figs. 10 and 17. In the second kind the resistance is between the fulcrum and the jiower, as in fig. 18. And, in the third, the power is betweeii the fulcrum and the resistance, as in fig. 19; and the power exceeds the resistance as much as the distance of the resistance from the fulcrum exceeds the distance of the power from the same point. In other words, when a lever is in a state of equilibrium, the number of weights representing the power and the resistance, multiplied by their respective distances from the fulcrum, show identical results. 17- 17. Lever of the First Kind. — See Lever on a wedge-shaped fulcrum, fig. 10, and Suspended Lever, fig. 17. In this last ex- ample the lever is suspended by a pin and a cord, /, ^hich consti- tutes the fulcrum. The power c(msists of 3 weights put on the 8th division of the lever, measuring from the centre, and the THE LEVEK. resistance consists of 4 weiglits affixed to the 6tli division of the lever, on opposite sides. n\\ i\\\\\n\\\\\\\\\ > 18. Lever of the Second Kind, fig. 18.— In this case the lever is suspended by the cord / constituting the fulcrum ; the power, consisting of 3 weights, is suspended by a simple pulley from the loth division of the lever; and the resistance, consisting of 5 weights, is suspended from the 6th division of the lever, on the same side of the lever. As the 3 weights at division 10 pull the lever upwards, and the 5 weights at division 6 pull it down- wards with equal force, the lever remains horizontal, although no force is applied to the arm b. 6 MECHAKICS. ig. Lever of tie Third Kind, fig. ig.— As explained above, tMs kind of lever is not essentially different from a lever of the second kind. The power of 3 weights is suspended by a pulley from division 2, while the resistance of i weight acts upon division 6 of the lever. Hence the power is greater than the resistance, and is situated between the resistance and the fulcrum. They are brought into equilibrium by their respective distances from the fulcrum. 20. Gravesende's suspended Lever, fig. 20. — This apparatus con- sists of — the suspension rail c d, the lever for suspension a b, a pair of simple pulleys (No. 30), 2 scale pans ( Xo. 4), and a supply of zinc weights (No. 5). 21. Fasten the pulleys with pins to the suspension rail, and attach the scale pans to the lever after passing the strings over the pulleys. Then add counterpoises to the scale pans till the lever is in equilibrium and rests in a horizontal position. The lever is then in a condition to be sensible to the action of a very small weight. Experiment A. — Suspend some weights at 0° in the middle of the lever. Half as many weights must be put into each scale pan to counterpoise the weight at 0°. Experiment B. — Arrange the weights as represented by fig. 20 ; namely, put 4 weights = 40, on the lever, pulling it downwards, and I weight = 10, plus 3 weights = 30, in aU 40, in the scale pans at the two ends of the lever, pulling it upwards. These weights will be in equilibrium. The scale pans at the two ends of the lever are weighted unequally, to correspond with the position of the weight / attached to the lever. THE PULLEY. / This apparatus shows in what maimer a load can be placed upon a lever, so as to bear either equally, as in Experiment A, or very imequally, as in Experiment B, upon the men who support, or the horses that pull, the two ends of the lever. The Pulley. 27. The Pulley consists of a wheel called a sheave, fixed in a frame or Modi, and turning on an axis or axle. Eound its rim is a groove, on which a cord or band can pass to move it. A system of pulleys is a number of pulleys acting in concert. 28. Pulley Frame, of black wood, with hooks, in which to stretch the four sets of pulley blocks. No. 30, 34, 35, 37, to prevent the entangling of their cords, when the pulleys are not in use, 3«. 6d. 29. Sets of Pulleys mounted. — The pulleys, or sheaves, are made of box wood, and are from li inch to 34- inches in diameter, the simple pulleys being 2i inches. The blocks are made of hard wood stained black, and are all provided with brass hooks. "When they are to be used they must be suspended by means of pins and hooks. No. 8, to holes prepared in the suspension rail. No. 2, to receive them. The effects of the friction of pulleys on their axles, of their rubbing against the blocks, the rigidity of the cords, and the weight of the pulleys, produce inaccuracies in experimenting, which have to be recognised and allowed for, in the manner described in the following articles. 30. Simple Pulleys, a set of four, made of box wood, the blocks of hard wood, stained black, all provided with brass hooks. Size of the pulleys zi inches diameter. Price of the set of four, 6s. 31. Experiments with Simple Pulleys. — Fig. 31 represents one simple pulley attached to the suspension board so as to form a fixed pulley. The weights p and w, attached to the cord a, h, must be equal ; the pulley is then at rest. If the power p is lowered a few inches, the weight w rises exactly as many. There is no gain of power by this pulley, but it affords useful aid in the lifting of heavy bodies, and in other modes of transferring power. 32. Eig. 32 represents a Moveable Pulley, b, combined with a fixed pulley, a, both attached to the suspension board. Before the weights p and w are added, it will be found that the apparatus is not in equilibrium, the moveable pulley b being heavier than the cord descending from A. In consequence, a scale pan. No. 4, must be connected with the cord a, and shot be added to counterpoise the pulley b. Then, upon adding weights, it will be found that 2 weights in the pan will balance 4 weights attached to the pulley MECHANICS. B, and that if the power p is pulled down, by extra weights or otherwise, say 12 inches, the weight w will rise 6 inches, the cords 6 and c each becoming shorter by 6 inches. 31. r- 33. A System of Pulleijs, fig. 33. — In this system there are 3 moveable pulleys and i fixed pulley, and with such an arrange- ment we can, with a power of i, counterbalance a resistance of 8. The fixed pulley merely affords a convenient mode of applying the power. After mounting the pulleys on the suspension board, as shown by the figure, the scale pan and any necessary counter- poise must be added to the cord a, before the weights are applied to constitute p and w. After the equilibrium is established, any extra weight, beyond the quantities specified above, added either to P or w will overset the equilibrium, and put the pulleys in motion. When p descends, it will pass over eight inches for one inch that w ascends. 34. Pair of long Tliret-sTieace Pulleys, made of box wood, the blocks of hard wood stained black, provided with brass hooks. Size of the largest pulley, 27 inches diameter. Fig. 34. P/-,'cc 5s. THE PULLEY. I. ii'i-i! ■' '■ ; --'.A ^J :vv 34. 10 JIECHA^^cs. 35- Pair of Square Three-sheaee PidUiis. made of box wood, tlie blocks of bajd wood stained black, provided with brass books. Size of tbe pullevs. ;i incbes diameter. Fig. 35. Price Ks. :;5. Tbe two systems of pullevs. Xos. 3+ aud 35, botb bave six cords to support tbe weigbt, and one cord for tbe power. In eacb case tbe weigbt supported is sis times greater than tbe power, consequently for ei-ery incli tbat tbe weigbt w rises tbe power p descends s/.r inches. In mounting tbese systems of pulleys for experiment tbe scale pan and coimterpoises must be used in eacb case, becanse tbe friction and weigbt of tbe pnlleys is considerable. 37. White's Concentric Pulley, Jig. 37. — Tbe pnlleys are made of box wood, tbe blocks of bard ^yood stained black, provided witb brass books. Diameter of tbe largest pulley of the upper set, 3^ incbes ; diameter of tbe largest pulley of tbe lower set, 3 incbes. Price Sg. Tbe action of this set of pulleys is accompanied by less friction tban tbat of tbe sets described above. TTben ari-anged aud counterpoised, tbe weigbts to be added to produce equilibrium are 7 for tbe resistance and i for tbe power, and when set in motion tbe spaces described by the weigbt and tbe power are as 7 to I . 3S. Pulley Frame, and Set of Brass Pulleys. — Consisting of two brass pUlars, a long cast-ii-on base, and a mabogany connecting beam at top. Size 2^ feet wide aud 3 feet bigb. Tbe brass piiUeys are tbe same, in size aud foi-m, as tbe wooden pulleys described above, Xo. 30, 34, 35, 37. Price of the set, 4Z. 4s. Thb Inclined Plaxe. 46. Inclined Plane, witb base, botb made of bard stained wood ; eacb piece ;; feet long aud 3 incbes wide, connected by a brass binge; witb a brass roller weigbing i lb. avoiidupois, a brass pulley, and a block for raising tbe plane to any re- quired angle. Price, xcithout scale ]}a II and icei(ihts, os. Tbe scale pan Xo. 4, and tbe wcigbts Xo. 5, may be used in experiments with this ap- paratus. 47. In tbis, as in otber me- cbanical powers, time is lost as power is g;viued ; for tbe ver- ticAl height to which a body THE "WHEEL AND AXLE. 11 is raised by means of tlie inclined plane is equal only to the height of the plane, while the space through which the power descends is equal to the length of the plane : the less the height of the plane, the greater the weight that can be raised on it by a given power. When a plane is twice as long as it is high, ^ lb. at 6, fig. 46, acting over the pulley c, will balance 1 lb. at a, or anywhere on the plane, and so of all other quantities and pro- portions. The Wedge. 48, Wedge : 6 inches long, 3 inches wide, with a divided cylin- drical block, 7 inches long and 4 inches in dia- meter, bound with caoutchouc bands. Fig. 48. Price 4s. 49. The action of the wedge is that of a double moveable inclined plane, presenting two faces to two resistances to be overcome. The great prac- tical advantage in the use of the Wedge, and that which gives to it its marvellous power, is, that it admits of being driven by impact, and that any force of impact is infinitely great as compared with any force of pressure. A second useful pro- perty of the wedge is, that it retains every new position into which it is driven between the resisting surfaces. The Wheel and Axle. 50. Wheel and Axle, consisting of two concentric pulleys out of one block of hard wood ; the largest pulley 6 inches in diameter, the smaller 3 inches ; with central pin for attaohing the wheel and axle to the black rail, No. 2, and round which the pulleys move. Price zs. The weights No. 5 are to be used with this model. 51. This machine may be considered a kind of perpetual lever, having its ful- crum or prop in the centre of the axis and the wheel. The acting, or longer part of the lever, is the radius or half the diameter of the wheel, and the shorter, or resisting part, is the radius of the axis. In the model above described, the larger 50, cut 12 MECHAXICS, i-adius is 3 inches and the smaller i A- inch. Consequently, 2 weights suspended from a vnH be counterbalanced by I weight suspended from 6. As to time, it follows of course, that when in motion, while the weight c ascends i foot the weight d must descend 2 feet. This mechanical power is applied to many uses, forming the essential part of the winch, the windlass, the capstan, and the crane. Its power is increased by enlarging the larger wheel and diminishing the smaller; but this mode of gaining power is only practicable to a certain extent. When it is necessary to lift very heavy weights, the Compound Wheel and Axle, Xo. 52, is made use of. 52. Compound Wheel and Axle. — The wheel of this model is 5 inches in diameter ; the thick axle 3 inches, and the thin axle li inches diameter ; the whole apparatus is 9 inches long, made of hard stained wood. Fig. 52. 53. Bracket by which the Compound Wheel and Axle is attached to the Suspension Eail, Xo. 2. This bracket serves also for use- with the Model of the Screw, Xo. 55. 54. The Compound Wheel and Axle, Xo. 52 ; the Bracket, Xo. 53 : the Model of the Screw, Xo. 55. Price of the set, iSs. 55. In the Compound Wheel and Axle the axle is made of different thicknesses, as at a and h, and a cord coils round these axles in different directions, and jasses round a moveable pulley, d, from which is suspended the weight that is to be lifted, w. When the wheel c makes cne turn, by tie action of the power p, the cord is coiled up once round the large axle 6, and is un- coiled once from the small axle a. Consequently it is shortened by a space equal to the difference of w 5:. p the circumferences of the axles a and 6, and the weight w rises a space equal to half that difference. If the weight rises half an inch only while the cord round c descends 30 inches, then I 11). at P will balance ico lb. at w. The power and the rapidity of action of this machine depend THE SCEEW. 13 upon tile difference of the diameter of tlie two axles. The less the difference of these diameters, the less the power required to main- tain the weight in equilibrium, and to move it. By making the two axles more nearly of the same diameter we can diminish the power necessary to raise any given weight, or increase the weight which any given power will raise, without limit. It is evident, that to cause the pulley d to descend, the action of the wheel c (or the winch handle used instead of it) must be reversed, upon which the cord will be unrolled from the wide axle and rolled upon the narrow axle. The Screw. 56. The Screw. — Apparatus for illustrating the principle of the action of the Screw. Size of the screw 6 inches long, 3 inches diameter, with square bottomed thread made of hard wood stained. Mounted on a spindle with handle, and adapted to the Bracket, No. 53. Price : see No. 54. 57. The screw is an inclined plane coiled round a cylinder, as represented by iig. 56. There are two kinds ^ — i of screw, the male screw, with projecting threads as here repre- sented, and the female screw, which has hol- low spaces , corre- sponding ^vith the threads of the male screw. The female screw is often called a nut, which is a block perforated by a screw, that fits any part of the male screw. Every turn of a screw carries it forward in a fixed nut, or draws a move- able nut along with it by exactly the distance between two turns of its thread : this distance, therefore, is the space passed through by the Resistance, while the Force moves in the circumference of the circle described by the handle of the screw. The disparity between these lengths or spaces is often as a hundred or more to one : hence the prodigious effects which a screw enables a small force to produce. 58. Collection of Worldnrj Models to illustrate the Mechanical Powers, consisting of the Lever, the Pulley (several sorts), the Wheel and Axle, the Inclined Plane, the Wedge, and the Screw. 14 MECHA^"ICS. German mamifacture, neatly made in wMte wood, with a printed and illustrated description. In a smootli box witli sliding cover, size 12 by i8 inches. Price 21s. This box of small models does not form part of the series above described. Cestee of Geavitt. ;o. Apparatus to illustrate the Ctntre of Grav'itii. namely, two equal paralMopipeds of hard wood, each 5* inches long, 4 inches wide, 2 inches thick, of a rhomboidal form. They stand firmly on end when separate, but, when placed on one another, they are on the point of faUing : a penny piece suffices to overset the equilibrium. Price 2s. They are marked with lines to show the centre of gi'avity. 71. Leaning Tower, or oblique Cylinder, 8 inches high, 4 inches diameter, in two pieces, made of hard wood. They stand firmly on end when separate, but are on the point of falling when placed on one another. Price is. -2. An Irregular Board, with a string, for showing how th^ centre of gravity of an irregular figure may be found. Lines are drawn on the board to show the position of the centre of gravity as determined by experiment. Fig. 72. Price is. 73. Apparatus to show that the centre of gravity of a body is not necessarily within its volume, consisting of a semicircle of brass weighted at the two ends, and supported on a brass stand, on a knife edge. Fig. 7:5. Price 3 s. 6d. ^ CENTEB OF GRAVITY. 15 74. The Equilibrist, fig. 74, small size, about 2^ Inclies long. Price IS. 6d. 75. Ditto, large size, figure about 4 inches long. Price 2s. 6d. 76. The equilibrist is a child's toy, resem- bling fig. 74. It consists of a figure carved in wood, and reposing by a point on a little pe- destal. Two wires fixed in the figure end in balls of metal. By this means the centre of gravity is thrown below the point of suspen- sion, and the ecLuilibrium is thus rendered stable. The figure is readily moved about, and can be made to oscillate freely ; but after every move- ment it ends by placing itself in such a position of equilibrium that the vertical line passing by the centre of gravity passes also through the point of support. 77. The Bmol- About. — This toy is founded on the principle of placing the centre of gravity very near the lower part of the figure, by accu- mulating the material in that region so as to produce stable equili- brium. Fig. 77. Price 2s. 6d. 78. " There is an amusing Chinese toy, which has the appearance of a little fat laughing man, sitting on the ground with his feet concealed under him ; but where the feet should be there is only a rounded smooth surface, with heavy lead ballast placed in it, so low, as always, when allowed, to raise the body to the erect or sitting attitude. A child 7 7. pushes the little fellow dovm again and again, and would persuade him to be still, but is surprised to see him always up the moment after, shaking about and as lively as ever." — Dr. Neil Arnott. 79. Double Cone, which apparently runs up an in- clined plane. Fig. 79. Price 8s. 6d. yg. IG MECHANICS. This apparatus consists of a doublo cono auil a sort of railway, tlio two liuns of which depart from a centre and at the samo time diverge and rise, as represented in fig. 79. When the doublo cone is placed horizontally across the inclined plane prediicod by these rails, it appears to run up the inelino ; but, in I'eality, the centre of gravity of the double cone descends between the wident'd rails, so that the cono siiils while it seems to ri.te. At tho upper ends of the rails are notches, to hinder tho cono from running off the rails. Degrees op Stability. 80. Cone for slitnrinij xtatcs of E iuveuieut for the experiment required ; the length of the pendulum is to be adjusted ac- cording to the weight and veloeitv of tbe falling body or else to strike se- conds on the bell, and then iumly fixed by the thumb-screw in the neces- sary position. Tbe heaviest of the 3 weights serves to illustrate the Law of Falling Bodies that the velocity is equal to the square of the time. If, for instance, the weigbt be adjusted to 0, and the pen- dulum set in motion at the first stroke, it will fall to i, at the second to 4 (Xo. S on the scale'i, at the third to 9 (Xo. 1 3 on the scale), ite. Arc, till the ninth to Si (Xo. iSz on tbe 22 MECHAWCS. scale) ; the first series of these numbers is marked on the outer graduations. This experiment, as well as the following and many others which can be made with this machine, will be found described in every treatise on Physics. The second experiment for illustrating uniform velocity by using the two lesser weights, the smaller of which is termed the inertia weight, for counteracting the inertia of the mass of matter to be moved, namely, the pulley wheel, friction wheels, pair of buckets and weights. The perforated stage is placed at one of the numbers on the outside scale showing squares of times. On starting, the weight at first falls according to the first experiment in velocities equal to the squares of the times, but at the instant the bucket passes through the perforated stage the longer weight will be removed, and the bucket containing then only the inertia weight will continue to descend at the uniform rate of the velocity acquired at the time of the removal of the longer weight, and not with accelerated velocity as in the first experiment. Fig. 96 represents the general form of this machine, but is not accurate in details ; in particular, it shows the graduation very imperfectly, and omits entirely the representation of the friction wheels which support the pulley at the top. Price of the machine as described above, loZ. los. 97. WJiirling Table, or Centrifugal Machine, with Adjuncts for 12 experiments to illustrate the Laws of Central Force. Price of the machine, with 12 Adjuncts, CI. 6s. CENTRIFUGAL MACHINE. 23 97 A. Price without the 12 Adjuncts, hut loith the Table a, 3Z. The Adjuncts separately, at the price affixed to each. The maoliine is represented by fig. 97, and the adjuncts by figs. 97 A to 97 M, of which pieces, Nos. 97 a and 97 b are shown as if screwed on the machine and in action. The Centrifugal Machine consists of an iron frame or base, on which are mounted an iron wheel to produce rotation, and a pulley for supporting the adjuncts, and conveying the motion to them for the various experiments. The wheel and pulley are connected by a stout band of catgut, which can be strained when necessary by a screw placed under the wheel. The adjuncts represented by figs. 97 A to 97 M are all mounted on female screws, which fit the male screw affixed to the upper end of the axle of the pulley. All these pieces of apparatus, a to m, can be readily screwed on the machine for experiments, and be rapidly removed when the experi- ments are finished. Mg.97A. A circular table of black wood, 12 inches diameter, which being put on the pulley (see a, fig. 97) acts as a fiy-wheel to steady the action of the other pieces of apparatus. Fig. 97 B. Price 6s. This represents an apparatus formed of two elastic rings of thin brass, which are fastened at the bottom to a vertical iron rod, and at the top to a ring which slides freely upon the rod. The lower end of the rod is screwed to the pulley. When the centrifugal machine is set in motion the rings represent a sphere, but when the whirling of the table becomes rapid the rings assume the form shown by the dotted oval. This experiment is made to illustrate the tendency of spherical bodies, which revolve rapidly on their axes, to assume a spheroidal form — as the earth does. Fig. 97 0. Price 5«. 6d. An apparatus to exhibit the effects of inertia. It is to be screwed above the blackboard, fig. 97 A, and rotated slowly. Observe the effects : the ball does not immediately begin to move with the board, but endeavours to con- ^^ tinue in its state of rest. As the rotation pro- ||? ^^^ ceeds, the board communicates its own motion ^^ to the ball, and shortly the ball keeps a posi- g , 0. tion on the board, assuming the same velocity as the board, and having no relative motion of its own. The apparatus now exhibits the state of matter common on the sur- face of the earth, where moveable things of all kinds retain their places, notwithstanding the rapidity of the earth's rotation. But to pursue the experiment in hand. Stop the rotation of the board with your hand. The ball does not stop when the board is j; 24 MECHANICS. stopped, but (MiitiiiiKiH its rovfilntimis on tlio board, imMl it is stopped by iVicd^ioii mid tlio uc^tioii lA' tho iiir'. TIu'h kIiiivvh tliut matter, oiuio put into inotinn, contiiiiios to inovii until it iiicotB witli rosiRtanco. Fig. 97 11. Pricf "js. Cd. This figure ropi-iiMuutH u cnii|iln cf bni,i-iH ballrt, (vinnoctiid hy \i fine wii-o, (ir ii tliin juotal tiibn, mid vvliidi slido ii|i(iii a long wire affiixiid to a frairid, upon tlio bottom of wiiicli iH a w.rciw adapted to tlio wrovv of tlio wliirliiig table. Wlioii tliOHO IhiIIh are |)lii(: left ^ijite. K«paratU8 HYDEOSTATIC PARADOX. 53 known as Pascal's Vases and Haldafs Apparatus, JNos. 247 and 248. 247. Pascal's Apparatus, modified by M. Masson. — Fig. 247. Price, without the balance, 2I. zs. " We owe to Pascal the discovery of the Hydrostatic principle, to which his name remains attached, namely : That the pressure exercised by a liquid on the bottom of a vessel depends exclusively on the dimensions of that bottom and on the height of the column of liquid which it supports. Various apparatus have been con- structed for the experimental demonstration of this principle. I shall describe that which Pascal himself imagined, and which has been brought to perfection by M. Masson. " Three glass vases of different forms, fig. 247, open at both ends, can be screwed by brass mounts at- tached to the lower end of each of them, upon a brass collar, which is fixed upon a tripod. The lower orifices of these three vases, which are all of exactly the same diameter and are carefully ground, can be closed one at a time, by means of a disk, which disk is held by a thread, that traverses the vase and is attached to the arm of a balance. Weights which are put into the scale pan attached to the other arm of the balance, apply the disk exactly against the lower orifice of the collar into which the vase is screwed. " For example, one of the vases, being screwed on the brass collar, we pour into it a certain quantity of water, so much, indeed, that its pressure on the disk makes a just equilibrium with the weights that have been put into the opposite scale pan of the balance. The level to which the water rises in the tube is marked by the indicator — a pointed rod which slides on an upright rod which rises from the tripod. W^e remove the weights from the balances, and, the equilibrium being destroyed, the disk is repelled from the vase, the water escapes into the glass pan placed below it, and the vase is emptied. " The vase is then unscrewed, and is replaced by another vase. We put again into the balance pan the weights that had been removed, and the second vase being thus closed by the disk, we again put water into it, and we ascertain that the height of the 247. 54 HYDKOSTATICS. column of water capable of bringing into equilibrium the weights on the balance is exactly equal in the two vases, although their forms and capacities are different. " We repeat the experiment with the third vase, and find that the result is the same, not only with it, but with any other vase the lower orifice of which has the same diameter." — SalJcron. 248. Saldat's Apparatus, for showing that the pressure of Kqniils depends upon the height and the extent of surface of the bottom of the columns, and not upon the capacities of the vessels. The apparatus is represented by fig. 248. It consists of three large glass vases, mounted with brass coUai's and screws of uniform size ; it has a bent horizontal ii'on tube terminating at one end in an iron cup, to which the glass vases cau be screwed one at a time, and at the other end with a vertical glass tube upon which slides a small brass ring. There is an upright brass rod with a moveable point to mark the sm-face of the liquor in the jar that is in operation. Price of the set, 2I. 2S. 249. When the apparatus is to be used for an experiment the horizontal tube must be filled with mercury, which must be poured into the cup where the stopcock is fixed, but not so much of it as to cause it to run into the stopcock. The mercury then rises to a corresponding level in the naiTow tube at the other end of the apparatus. One of the glass jars is then to be screwed on to the mercury box, and the brass pointer is to be adjusted, as shown in the figure. Water is then to be poured into the jar until it rises to the point of the indicator. When this is observed, the mercury will be found to have risen in the narrow tube at the other end of the apparatus ; and the exact point to which it has risen is to be marked by means of the sliding ring. The water is then to be run off by the stopcock. Meanwhile the mercury in the narrow tube sinks down to its original level; but the position of the sliding ring is not to be altered. The glass jar is next to be removed and exchanged for another, which in its turn is to be filled with water till it rises to touch the point of the indicator. It will then be seen that the mercury has again risen in the narrow tube up to the sliding ring. The operation is to be repeated with the third glass jar, and it will be attended with the same result, 248. PRESSURE OF A CONE OF WATER. 55 namely, that the three vessels when filled with water up to the brass pointer, all drive the mercury in the narrow tube up to the same level. Note on Haldat's Apparatus. — In most books on Physics this apparatus is represented as sharing with Pascal's vases the pro- perty of demonstrating the truth of Pascal's principle, laid down in paragraph 245. We think it fails to give any such demon- stration, and that it rather belongs to the apparatus described as illustrating paragraph 212, which treats of the level assumed by two different Uquids in communicating vessels. The proof of this is, that for every inch which the mercury rises in the narrow tube of Haldat's Apparatus, the water must rise 1 3 • 6 inches in the large tube, whatever may be the form and capacity of the wide tubes, and whatever the area of their bases. The exact correspondence of the diameters of the bases of Haldat's vases does not hinder the performance of his experiments, and does not help it. Eead para- graphs 212 to 216. ApPARATTJS FOK DETBKMINrNG THE PeESSTTEE ON THE BaSE OF A Cone of Watek in a Vessel without a fixisd bottom. 250. Cone. — Fig. 250 represents the vessel employed for this purpose. It is a conical glass tube, 10 inches long, of 2 inches interior diameter at one end, and 2t inches at the other end ; or very nearly of these dimensions. Each end is made as level as possible, has a broad welt, and is finely ground. Price 3s. 6d. 251. Cone mounted for use. — Fig. 251 represents the glass cone mounted for use. It is supported by an iron collar, attached to a strong iron support. The cone is protected by slips of caoutchouc tied on under the iron collar, without which it cannot with safety be screwed up tight. A ground disk of plate glass, 3 inches in diameter, is supported by a thread to the hook of a balance pan, namely, the small pan re- presented in fig. 122, which shows the balance that is suitable for 251. 56 HTDEOSTATICS. these experiments. To get this thi-ead up through the cone, a long iron wii-e with a hook at the end is used. A ghiss pan is placed on the foot of the support, ready to catch the water that, from time to time, escapes from the cone. When the glass cone is properly fitted to the collar of the iron support, it can be inverted without derangement. The whole system is perfectly rigid, and does not give wny when the cone is filled with water. Price of the Ajp}iaratus re^o-esenied by fij. 251, uithoui the balance, ll. 5s. 252. E.c2)eriments icith a Glass Gone, 10 inches long, 2 inches internal diameter at the narrow end, and 2^ inches at the wide end. 253. E.iyeriment A. Beteiininaiion of the capacity of the Cone in Ounces of Water. — Fit up the apparatus as shown by fig. 251. Put into the large scale-pan of the balance enough weights to draw up the disk firmly against the bottom of the glass cone. Then pour water slowly into the cone from a quart glass measure graduated into ounces, such as fig. 1 3 S d. Fill the cone level with the ground welt, and then examine what is left in the graduated measure. In an experiment made thus with a cone of the above dimensions, the quantity of water required to fill it was 2 4^ ounces. 254. E.xperiment S. Determination of the Weight of the Bisk. — The disk and string, in a dry state, sepai-ate from the rest of the apparatus, can be weighed in a balance, and the weight be used in estimating the results of some of the following experiments. We have used disks of thin ground glass, of i ounce and i^ oimces in weight ; and we have used thick disks of ground plate glass of 3 inches diameter that weighed 6 ounces. 255. Adhesion of the Disks to the Cones. — When the disks and cones are wet they adhere to one another with some force, espe- cially when groimd accurately. Not only will the disks suppurt their own weight when the string is slackened, but often 2 or 3 ounces in addition. The adhesive power is greatest when the disk is moderately wet. It diminishes when the disk is either dry, or flooded with water. We have found no way to estimate the amount of the adhesion modifying the results of the following experiments. 256. Experiment C. Pressure on the base of the Cone, placed with tlw narrow end downu-ards, and weighed on the hose disk. Arrange the apparatus as shown by fig. 251, and put into the large scale-pan weights more than enough to counterbalance any expected weight; say 28 or 30 ounces for the water and disk. Then pour water gradually into the cone till it is full. Next proceed very cautiously to put weights into the small scale-pan hung over the cone, to counterbalance the excess of weight in the lai'ge scale-pan. A point is soon reached, when the disk gives way SPECIFIC GKAVITY. 57 and lets out a little water. Take out the weight last added, fill up the cone with water, and add a smaller weight. By one or two changes you finally reach the point where the water is exactly counterbalanced. You may then run out the water and examine the weights in the pans, deducting from the gross weights in the large pan, first the counterpoise of the disk, and then the weights in the small pan ; the residue shows the pressure on the base of the water in the cone. In an experiment with this cone the pressure of water thus determined was 235 ounces. 257. Experiment D. Pressure on the base of the Cone placed with the vide end downwards, and weighed on the loose disTc. Arrange the apparatus as represented by fig. 251, but turn the cone with the wide end downwards. Put 40 ounces of weight into the large scale-pan, and proceed as directed under Experiment C, § 256. The pressure of the water, determined in an experiment made thus with the cone, was 34 ounces. The results of the foregoing three experiments are these : — A. Quantity of water that fills the cone, 24^ ounces. C. Weight on the disk, narrow end downwards, 23 J ounces. D. Weight on the disk, wide end downwards, 34 ounces. The vessel, the water, the balance, the weights, were the same in all cases. These facts seem to constitute a Hydrostatic Paradox, though that term is commonly applied to the Hydrostatic Bellows, described at §§ 235 to 237. SPEcrFio Gkatttt. EQrriLIBEIUM OF SOLIDS WHEN IMMERSED DT LIQUIDS. Principle of Archimedes. 270. Every solid when immersed in a liquid loses a portion of its weight equal to the weight of the liquid which it displaces. — Archimedes. 271. The following three cases can occur on putting this principle into practice, in reference to water taken as a standard : — A. The solid may be heayier than its own bulk of water. In that case it will sink. B. The weight of the solid may be equal to that of the water it displaces. In that case the solid will rest indifferently in any part of the water. C. The weight of the solid may be less than that of its own bulk of water. In that case it swims on the surface of the water ; and its weight is equal to that of the water which is displaced by its submerged portion. ■58 HYDEOSTATICS. These three cases of differences in density are illustrated by experiments 272 to 274. 272. Exhibition of Differences in tlie Specific Gravity of Liqvide. fig. 272, with a strong solution of common salt, and put an egg into it. li. Put an egg into the jar h, and half fill the jar with water free from salt. The egg will swim in the salt water, but sink in the fresh water, because its specific gravity is a little greater than that of tho fro:-h water, and a little less than that of the salt water. c. By cautiously adding fresh water to salt water a mixture can be made in which an egg will float, if it is gently put in above, and allowed to sink till it finds a stratum of liquid of its own density. This it will do after a little oscillation. Fig. c. Price of tJie Jars, fig. 272, 12 incites high, 3 inches wide, 18. M. eorJi. 273. Hie Bottle Imp. — This is a slight glass figure, which can be readily changed in specific gravity, so that it will swim ^^ in a jar at the top of the water, in the middle, or at the bottom, as desired. It serves, therefore, to illustrate the above cited three cases of differences in density. He'; Bottle Imps, § 730, among the Pneumatic Experiments, for a full explanation of this toy. 274. Ti'ree Solids of iJiffereid iJermtieit. — ^Into a glass jar, 12 inches high and 3 inches wide, put a saturated solution of common salt to the dei)th of 6 inches. Into this solution put a ball of ebony, an egg, and a ball of beech-wood. The ebony ball sinks to the bottom, while the beech ball and the egg swim. Xow add water gradually and stir the mixture with a long glass rod. At a par- ticular stage of dilution the ebony ball will remain at the bottom, the beech-wood ball will rise to the Burface, while the egg will remain suspended midway in the liquid. P/-ic« of the two ebr/ny and heech-wood halls, is. Pr'uie of o, glass jo.r 10 incites high and about 3 inches ir.ide, o.nd glass rod, 2«. 274 A. li a handful of ebony and beech-wood balls of the same size are dropped into water contained in a glass beaker, the ebony balls instantly go to the bottom and the beech balls rise to the surface of the water. The separation of the balls is so sndden and so complete, that, simple as the loatter is, the effect is surprising. SPECIFIC GRAVITY. 59 275. Experimental Demonstration of the Principle of Archimedes. — The apparatus consists of A, a cylinder of polished brass closed at both ends and having a hook at the top, its weight being 1000 grains ; and B, a cylinder of brass open at the top, of such capacity as exactly to contain the brass box A, and having a ring handle. In fig. 275 the two cylinders are represented as connected with the beam of the Hydrostatic Balance, No. 122, with the closed box sunk into water. Price of the pair of brass cylinders, 6s. 276. Experiment A. — Attach the two cylinders to the small pan as represented in fig. 275 ; but without using the water jar. Counterpoise the cylinders by weights put into the opposite scale- pan of the balance. Experiment B. — Bring under the cylinders a jar containing water, and raise the jar until the closed cylinder is just immersed in the water. A short water jar (fig. 27 5 b, is.), and a mahogany table support (fig. 275 6, 3s. 6d.) below it, is more conve- nient than the tall jar shown in the figure, because the arrangement permits the raising of the water without disturbing the balance. As soon as the brass closed box is immersed in the water the equipoise is destroyed, the small scale-pan rises and the large pan with the weights sinks. Experiment C. — If then the open brass cylinder is filled with water, applied slowly by means of a pipette till it is full, the equilibrium will be restored. The upper part of the brass box will be level with the surface of the water ; the balance beam will be horizontal and the needle vertical ; and the whole will be at rest ; the upward pressure against the brass box in the water being exactly equal to the downward pressure of the water put into the hollow cylinder, that is to say, to the weight of the water which the box had displaced. The closed box weighs 1000 grains ; it has the bulk of 1000 grains of water, and the capacity of the hollow cylinder is that of 1000 grains of water. Admitting that the above de- scribed experiments clearly demon- strate the truth of the principle ^75 b. 2756. of Archimedes, how are we to explain the following experiment ? 60 HTDEOSTATICS. 277. A glass jar containing water and a brass closed cylinder, suoh as is described above, are placed side by side on tbe scale-pan of a balance and are counterpoised by weights put into the opposite scale-pan. The brass cylinder is then taken up and put into the water contained in the glass jar. But this immersion fails to destroy the equilibrium that was previously established. We have proved above that the brass box loses 1000 grains in weight when immersed in water. Why is the immersion in this case without effect ? Is it not evident that what the box loses in weight is gained by the glass and water, which acquire the power of a dovraward pressure to compensate for the upward pressure that existed against the box ? This can be verified by an experiment made with the apparatus represented by fig. 278. 278. Weigh a glass beaker partly filled with water ; then im- merse in the water tbe closed brass cylinder supported externally by the method shown by fig. 278. When the brass cylinder enters the water the equilibrium is overset, and the balance beam descends on the side of the beaker. By how much does the immersion of the brass cylinder, though supported exter- nally, augment the weight of the water ? Precisely by the weight of the water displaced, namely, 1000 grains. To prove this fact it is only necessary to remove, by means of a pipette, as much water from the glass beaker as will fill the suspended hollow brass cylinder. When the latter is thus filled, the equilibrium will be restored. The theoretical explanation of the above facts is very simple. When we plunge a solid body into water we raise the level, and consequently we augment the pressures in the vessel to the same extent as we should do by adding a volume of water equal to that which the immersed solid displaced. 279. Price of the Stand for supporting the brass cylinders, Jig . 278, I OS. 6d. This stand is similar to the support of No. 251, excepting that the vice is removed from the block, and a rod with a hook at the end substituted for it. SPECIFIC GRAVITY. 61 Exhibition of variohs methods of Estimating the Specific Gbayity both of Solids and Liquids. 280. The principle of Archimedes (No. 270) serves to resolve a very interesting problem, that, namely, of estimating the com- parative densities, or specific gravities, both of solid and liquid bodies. We shall describe briefly some of the principal methods of effecting the solution of such problems. In all the specific gravity estimations, both of liquids and solids, the standard taken for comparison is pure Water at 62° of tempe- rature by Fahrenheit, the barometer being at 30 inches, and both water and other substances supposed to be weighed in the open air against weights made of brass. The only exception is alcohol, which, by Act of Parliament, is valued at 60° Fahrenheit. When French weights and measures are referred to, the conditions of the French standards are assumed to be adhered to. 281. Estimation of tJte Specific Gravity of a Solid Body hy means of the Hydrostatic Balance. — First, the solid is to be weighed in the air. Which of the balances described between Nos. 122 and 125 should be used for this purpose depends upon the bulk or weight of the solid, and upon the degree of accuracy to be aimed at in the operation. We shall refer to the Hydrostatic Balance, No. 122, which has been already several times referred to, as suitable for Class Experiments in Hydrostatics, but with the notice that it is unfit for working with very small quantities. Eead the descriptions of Nos. 122 to 137. The weight of the object being found, the next step is to deter- mine the weight of an equal volume of water. The division of the former weight hy the latter gives the required density. The deter- mination of the weight of an equal volume of water may be made as follows : — 282. The solid body under trial may be suspended by a thread, a hair, or a fine wire, to the small pan of the hydrostatic balance. It is to be counterpoised in air, and is afterwards to be plunged into water, which destroys the equilibrium. The weight which it loses is precisely equal to that of the water which it displaces, and is exactly that weight of a volume of water equal to the volume of the solid which we wish to ascertain. To prove this fact it suf&oes to place the indicated weight upon the small pan to which the submerged object is suspended, which immediately restores the equilibrium. Example a. — A solid weighed 400 grains in air. In water it weighed 300 grains. Hence the weight of its volume of water was 100 grains. Then, f^ = 4 ; so that the specific gravity of this solid was 4000, water being 1000. 62 HYDROSTATICS. Example h. — A piece of copper weighed 250*70 grains in air. In water it lost 28 ■ 48 grains. Then, %''g-'-^g = 8-80, which is the specific gravity of the piece of copper, water being I • 00. 283. Estimation of the Specific Gravity of a Liquid hy means of the Hydrostatic Balance. — Weigh a solid body first in air, and then in water, and also in the liquid whose specific gravity is to be estimated. The loss in each of the last two cases will be that of the weight of a volume of each liquid corresponding to the bulk of the solid submitted to trial. The solid to be weighed ought to be a globe of glass about f inch in diameter, containing a little mercury, and it should be fastened to the hook under the small pan of the hydrostatic balance by a thread or fine wire. When first weighed in air, and then in water, the loss shows the weight of a volume of water equal to the volume of the solid. Then having carefully cleaned and dried the solid, and weighed it in the liquor to be assayed, the second loss gives the weight of an equal volume of that liquid. Dividing the last result by the former, we have for quotient the required density. Example. — In an experiment made with alcohol the loss of weight was 354' 3 grains, and with water the loss was 442-8 grains. Then f|-|-f = o • 8, which was the specific gravity of the alcohol submitted to trial. Instead of a spherical glass weight a species of cylinder, or plummet, may be used with advantage, especially as this form of solid can be provided with a small thermometer for determining the temperature of the liquids submitted to experiment. See Mohr's Specific Gravity Balance, No. 299. 284. Estimation of the Specific Gravity of a Solid Body by weighing it in a Bottle. — The bottles for this purpose are repre- sented by a and b, fig. 284 ; they are made of slight blown glass, with wide mouths and hollow stoppers, capacity about half an ounce of water, not adjusted. Method of use. — Fill one of these bottles with distilled water up to the point of the stopper, and place it on the scale-pan of a balance, and by the side of it place some fragments of the body to be tried, which must be small enough to enter the mouth of the bottle, but not be in powder, say 100 grains accurately weighed. One of the finer balances, Nos. 123, 124, should be used for this experiment. Counterpoise by , weights put into the opposite scale-pan. 'Then put the solid body into the bottle, from which, of course. SPECIFIC GEAVITT. 63 there issues a volume of water equal to the volume of the solid ; put the stopper into the bottle and see that it is as full of water as it was at first ; wipe the bottle dry on the outside, and put it again on the balance pan. It will not produce equilibrium, but will require a compensation for the loss of the water that was displaced, say 25 grains. The density of the solid in that case will be i^" = 4. Here, as in the two former oases, the specific gravity of the solid body is the expression of the number of times wliich it is heavier than an equal bulls: of water ; and that expression is found by dividing the weight of the solid in air by the loss of weight which it suffers when it is weighed in water. Fig. 284 c represents a bottle with a tube stopper having a con- tracted neck on which the normal quantity is marked. All the liquor above that mark is removed by a roll of filter paper, and the upper stopper prevents further evapora- tion. Prine of these Bottles, of the capacity of about half an ounce, but not adjusted: figs, a and 6, is. each; fig. c, 2«. 285. Estimation of the Specific Gravity of a Liquid by Weighing it in a Bottle. — The specific gravity of a liquid can be determined by weighing a quantity of it in a bottle of the form and size represented by fig. 285. This bottle, when filled up to the mark a a on the neck, contains the hundredth part of an imperial gallon, or 700 grains of water at 62° Fahr. The bottle must have a brass counterpoise with a moveable cover, to admit of occasional corrections of the weight. Its convenient use also demands the following additions. A pipette, fig. 285 b, of the capacity of 50 septems, for use in filling the bottle to a a without wetting the outside. A narrow pipette, for adjusting the liquor in the bottle to the normal mark a a, after regulating the temperature. And a thermometer cased in glass, fig. 285 c, and made narrow enough to pass through the narrow neck a a of the bottle, fig. 285. This bottle may be weighed with the balance. No. 124, and the weights No. 127. 285. Price of the articles named above : — a. The Bottle 6. The Counterpoise c. Pipette, 50 septems When an experiment is to be made, the bottle should be filled by means of the pipette a little above the mark a a; the ther- 284 c. s. d. s. d. 2 6 d. 3 Small Pipettes .. 6 2 e. Thermometer 4 I /. The Set .. 10 64 HTDEOSTATICS. mometer stould then be used to try the temperature. If found correct, namely at 60° Fahr. for alcohol, and at 62° Pahr. for all other liquids ; then the small pipette should be used to adjust JDS 285 2855. 285 c. the liquor accurately to the mark a a, and the vessel be closed by the stopper. It may then be weighed. Deduct the weight of the counterpoise from the weight of the filled bottle, expressed in grains, and divide the residue by 7 ; the result is the specific gravity of the liquid submitted to trial, compared with water at 100. SPECIFIC GEAVITY BOTTLES. 65 VAnioD3 Forms op Specific Gkavity Bottles pok Liquids. For various purposes of science, or manufacture, many altera- tions have been made in the form of specific gravity bottles, of a few of which it may be useful to give a brief description. Fig. 287 to 253 represent the most important varieties. We subjoin a list of Prices of different sizes of each kind. 287. 291. 292. 293. 286. Eegnault's Specific Gracihi Bottle, form of fig. 2S5, with stopper and mark on the narrow part of the neck : — s. d. 250 grains 2 25 grammes . 2 500 „ 2 50 2 6 700 „ 2 6 100 ■ 3 1000 „ •• 3 66 HYDEOSTATICS. 287. Slight Blown Glass Bottles, with perforated stopper like fig. 288, in a japanned tin case with counterpoise, fig. 287 : — s. d. 8. d. 250 grains 500 „ 1000 „ ■■ 4 •• 4 •• 5 6 25 grammes . 100 ■ 4 • 5 ■ 5 6 6 288. Slight Blown Glass Bottle, with perforated stopper, without case or counterpoise, fig. 288 ; or Solid Glass Bottle, fig. 288 A, with massive stop- per, having a vertical groove on the side, without case or counterpoise : — 100 grains 250 „ 500 „ 700 „ 1000 „ I cubic inch d. o 6 o 6 o o 5 grammes 10 20 25 50 100 d. o o 3 6 o 6 289. Measuring Flasks, without stoppers, with i mark on the neck : — d. 9 o 50 septems ..09 10 grammes 100 „ ..10 25 500 J. ..19 50 1000 „ ..20 100 „ I pint .23 I litre 290. Measuring Fhshs, with stoppers, and I mark on the neck : — 4 6 8 10 o 100 septems 250 500 1000 ^ „ I pint I cubic inch 1000 grains d. o 6 o 6 o o o 10 grammes 25 50 100 250 500 ,; I litre s. o o I I I 2 2 291. Siiecijic Gravity Bottles, with thermometers ground in as stoppers. 292. Specific Gravity Bottles, different pattern, same price :— «. d. g. d. 250 grains ■• 4 6 25 grammes . ■ 5 500 „ 5 6 50 . 6 1000 „ •• 7 100 ■ 7 5 o 6 o 7 6 10 s. d. lo grammes ■ 5 25 . 6 50 ■ 7 6 00 . 10 SPECiFIC GEAVITY BOTTLES. 67 293. Specific Grant!) Bottle, i cubic inch, with finely divided thermometer, ground in as stopper, and an extra neck with I mark and ground cap. Price los. 6d. 294. Solid Glass Specific Gravity Bottle, with solid stopper, having a vertical groove on the side, form of figure 288 a ; accu- rately justified with counterpoise in leather case : — 100 grains 250 „ 500 „ 1000 „ 295. Practical Bemarlcs on the CJioice and Use of Specific Gravity Bottles. — As there is always a chance of error in measuring a definite quantity of liquor to be weighed, and also in changing the temperature of the liquor while wiping the bottle after filling it, especially when a perforated stopper is used, and as such errors aifect small quantities more seriously than large quantities, it is advisable in all cases to weigh the largest quantity of a liquor which the balance will carry, provided enough liquor is at com- mand. For example: — 8 fluid ounces of water (3500 grains) weighed in a balance that turns with J grain (see No. 124), will give a more accurate result than 500 grains weighed in a much more accurate balance ; because there may be in both cases an error of I grain in filling the bottle and finding the tempsrature, and that error falls less heavily on 3500 than on 500 grains. Knowing the power of the balance that is to be used, it is easy, by means of measuring flasks and measuring pipettes, to measure oif the greatest quantity of liquor that will suit the balance, and this can be done without giving rise to troublesome calculations. In proof of which I give the following tables, which embrace all the ordinary septem, decem, and gramme measures. By the word septem I mean the measure of 7 grains of water, and by decem the measure of 10 grains of water, at 62° Fahr. The first Table gives, in the second column, the m.ost common septem and decem measures: in the first column, their equivalents in grains of water at 62° Fahr. ; and, in the thii-d column, the number of times which the weight in grains must be taken to represent the specific gravity of the liquors that are tried in com- parison with water fixed at 1000. Examples. — i. 100 septems contains 700 grains of water. If this is divided by 7 and multiplied by 10, we have 1000 as the standard of specific gravities. 2. If a liquor ij times the weight of water is weighed in the same bottle, it is clear that 100 septems will weigh 700 -t- 350 = F 2 6-8 HYDEOSTATICS. 1050 grains. If this number is divided by 7 and multiplied by 10, we have 1500, which is the specific gravity required. Grains of 1 Septems ! or 1 Multi- Grains of Septems or Multi- pliers. Water. Decerns. | pliers. Water. Decerns. 7 I S. I 0^00 600 60 D. V 10 I D. 100 700 100 s. 10 T 35 s s. 200 7 750 75 D. 1 5° 5 D- 20 800 80 D. V 70 10 S. 100 875 125 8. 1 100 10 D. 10 900 90 D. '/ 125 12^ D. 8 I GOO 100 D. 140 20 8. ¥ 1250 125 D. 150 15 D. ¥ 1500 150 D. * 175 25 8, Y 1750 250 S. 1 200 20 D. 5 2000 2CO D. i- 250 25 D. 4 2500 250 D. ' t\ 300 3& D. '3" 3COO 300 D. i * 350 50 S. t" 3500 1 500 8. 2 j T 400 40 D. 10 5000 : 5 CO D. tV 500 1 50 D. 2 7000 1000 s. 1 ! 1 Gramme.?. 5 10 20 25 50 Multiplier. 200 100 50 40 JO Grammes. 100 200 250 500 Multiplier. 10 5 + 2 carry 3. A cheap laboratory balance, such as No. 124, which will rry 8 ounces in each pan and turn with -^ grain, will give good UOilAV u i^uAA»./v.a iii v.M.vxi j^wjj wuu i/uiii »Tiuix -^Tj- Ki't-lii, VVIIl tilVO gwu** general results with a bottle of the form of fi^. 290, and of the capacity of 250 septems = 4 fluid ounces; since even this quantity of concentrated oil of vitriol will be within the range of the balance, for if the specific gravity of the acid is I • 846, 250 septems of it will weigh 3230-5 grains. According to the Table the equivalent of water is 1 7 50 grains, and if that is divided by SPECIFIC GEATITT BALANCES. 69 7, and multiplied by 4, it gives 1000. So also, 3230-5, if divided by 7 and multiplied by 4, gives 1845 as tbe req[uired specific gravity. The second Table gives tbe factors to be used in reckoning the products of weigHngs of gramme (or centimetre cube) measures expressed in gramme "weights. 296-298. Estimation of the Specific Gravity of a Liquid hy Weljldng in a Bealcer a quantity first measured by a Pipette. 296. The specific gravity of any acid, alkaline, or saline solu- tion, can be readily tested by the following process. By means of a measuring pipette, fig. 296, transfer a small carefully mea- sured quantity of the so- lution that is to be tried, into a beaker, fig. 297, or a wide-mouthed light flask, fig. 298, and u-eigli it. To save trouble in calculation the quantity thus measured should be one of the quantities named in the above Table ; say, for example, 100 grains; then, the weight of the liquid, multiplied by 10, gives the specific gravity. Price of pipette, fig. 296 = 1000 grains „ jar, 297 = 5 ounces „ flask, 298 = 5 ounces s. d. I 3 o 8 o 5 299. Mohr's Hydrostatic Balance, for taking the specific gravity of liquids by an easy method, which gives the specific gravity without calculation, and requires but a small quantity of liquid, and no other apparatus than that represented in fig. 299. 299. Price, in a mahogany glass case, including a portable maho- gany box, 4Z. 14s. 6d. 300. Price, in a mahogany box, without glass case, 2I. 15s. Description of Mohr's Specific Gravity Balance. — This apparatus consists of the articles represented in fig. 299; namely, a lo-inch beam, of which i branch is divided into 10 parts ; a glass plummet, which contains a thermometer, and is attached to a platinum wire by which it can be suspended from the beam ; a glass cylinder, 70 HYDROSTATICS. and a maliogaiiy tray for it ; a small brass pan to counterpoise the plummet ; a pair of pans, marked e e in the figure, for the ordinary weighing of solid bodies ; a set of riders, marked a h c d, oi which d is equal to the weight of the water dis- placed by the plummet, while c = i^g- of d, & = ^ of c, and a = TV of 6. The apparatus can be dismounted and packed in the maho- gany box, and then removed from the glass case for tra- velling. The scale of the thermo- meter included in the glass plummet is usually that of Eeaumur, for which reason we give the following equi- valents of the degrees most likely to be observed : — 2y9. E. r. E. F. E. F. E. F. 20° 77-° 16° 68-° 12° 59-° 8" 50° 19 74-75 15 67-75 II 56-75 7 4y75 18 72-5 14 63-5 10 54-5 6 45-5 17 70-25 13 61-25 9 52-25 s 43-25 Process. — I. When the small pan is attached to one end of the beam and the plummet to the other end, the beam rests in equili- brium. 2. If the plummet is plunged into distilled water, that end of the beam rises. 3. If in that case one of the largest riders, d, is put on the hook at that same end of the beam, the equilibrium is again restored. This result shows that the rider d is equal in weight to the displacement of the plummet. 4. If a liquid lighter than water is submitted to trial, the large rider d must be placed somewhere on the divided branch of the beam, where it will produce equilibrium. But when, as commonly happens, this occurs at some point between two notches on the beam, it is best to rest the rider on the notch of lowest value of the two between which it rests, and then to apply the next sized rider, c, to determine the diiferenoe. Thus, in fig. 299, we see the SPECIFIC GRAVITY BALANCES. 71 large rider at 8, and the small rider at 5. In tliis case, tte former represents 8 in the first place of decimals, and the latter represents 5 in the second place of decimals. Thus, 0'85. If the rider c does not effect an equilibrium, when fixed in a notch, but falls between 4 and 5, then it must be placed in 4, and the third sized rider, 6, must be employed to find the exact point of cfiuilibrium. This third size of rider stands for the third place of decimals in the expression of the specific gravity : and finally, the smallest rider, a, expresses the fourth place of decimals, thus : — ffl is = -OOOI to "OOOQ 1 . T ,-, . 1 • .1 J • , i „ According as they stand m the IS = 'OOI to -000 .( i. 1, i ii , , -^ ) notches i to q on the beam C 18 = '01 to 'OQ , , , -^ , . J. when at rest. a IS = • I to ■ 9 ) 5. If a liquid heavier than water is tried, the process goes on exactly as above described, with the addition that one of the riders d is in every case hung at 10, the extreme end of the beam, to serve as the equivalent of the weight of water, while the riders which show the difference between water and the given heavy liquid cross the beam at the proper points. A few examples will illustrate this principle. In the following plans the figures repre- sent the notches on the beams, and the letters the respective sizes of riders : — ■ 2345 6 7 8 9 10 h e d d = I • 842 Sulphuric Acid. dc d = 1-33 Caustic Potash. e d = 0-96 Ammonia. c d = 0-75 Ether. d b c d = I '495 Nitric Acid. Power of the Balance to weigh Solids. — It will carry 1000 grains, and show -^^ grain. With 500 grains, it shows ^^j- grain ; and with 300 grains, it shows -r}^ to 3L grain. The larger pair of pans, marked e in fig. 299, are used for weighing solids. 301. Mohrs method of estimating the Specific Gravity of a Solid by measuring the Water it displaces. — The apparatus consists of a glass beaker, ground smooth on the edges ; a flat slip of wood or brass, having, on the under side, a conical piece of brass ending in a fine point ; and a pipette. See fig. 301. Price €s. "When the experiment is to be made, the beaker must be fixed by a little wax upon a steady horizontal table. The conical brass spike must be rubbed with chloride of platinum, which makes it black, and afterwards be slightly greased with tallow. If the solid body that is to be examined is weighed in grammes, the pipette must be graduated into centimetre cubes. If the solid is weighed 72 HYDROSTATICS. in grains, the pipette must be graduated into grains or septems convertible into grains. Process. — Pour some water into tbe beaker, put on tbe brass pointer, and add water to the beaker, carefully and slowly, by means of the pipette, until the surface comes into contact \'i'itb the brass spike. This can be done with wonderful precision ; for when the light of the sky plays upon the surface of the water, it forms a brilliant white gi'ound 5^,,^ upon which the reflection of the black spike is ^^^ very distinct, and the meeting of the water and f/f index is instantly recognised. The index is then if removed, the substance whose specific gravity is f^Mjfj to be estimated, and which has already been | ^'^°gS l weighed in air, is put into the water ; and the 301. pipette, which must be previously wetted inside with other water, is to be used to take out of the beaker as much water as appears to be a little more than the volume of the solid body under trial. The index is then to be replaced on the beaker, and, if the proper quantity of water has been taken up by the pipette, the index will not touch the water in the beaker. Then water is to be slowly dropped from the pipette into the beaker, until the surface rises to touch the black spike. The water that then remains in the pipette is necessarily the volume of the solid body. The value is read ofl' in grammes or grains, accord- ing to the graduation of the pipette ; and, on dividing the weight of the solid by that of the water, we have the required specific gravity. 302. Nicholson's Hydrometer, for taking the Specific Gravity of Minerals and other Solids.— Fig. 302. A. Price, in japanned tin, 5s. B. Price, in brass, 6s. 6d. This instrument is formed as shown by fig. 302. It is usually about 9 inches long and ji inch in diameter. At the top is a small basin for holding weights or the solid substance that is to be tried. There is a small pan at the bottom, which is loaded with lead to make the instrument swim in a vertical position. In the middle of the neck a mark is painted or cut (not shown in the figure). A normal weight, say 200 grains, when put into the upper basin, sinks the instrument in pure water at 62° Fahr. down to the mark on the neck. That is the normal condition of the instrument. \=j When an experiment is to be made, the instrument is to V he placed in water at the temperature of 62° Fahr., and 302. the solid to be tried is to be put into the upper basin, r\ THE HYDBOMETEE. id with as manv weights as will mate np the 200 grains which con- stitute the normal power of the instrument. The weight being completed, the iustrument sinks till the surface of the water cuts the mark on the neck. Deducting from 200 the weights added to the solid, the residue is the weight in grains of the solid when weighed in air. Eaise the hydrometer in the water, remove the solid from the upper basin to the pan at the bottom, and sink the instrument again in the water, when it will be found to have lost weight, which necessarily is the weight of the volume of water dis- placed by the solid (^see § 281) ; then add to the weight that remains on the basin as much more as will restore the equilibrium. The weight so added is equal to that of the displaced water. Dividing the weight of the solid in air by the loss of weight in water, the quotient is the specific gravity. Example — In an experiment with a piece of sulphur the weight in air was found to be 64-2 grains, and the loss of weight in water was 31 grains. Hence 64-2, divided by 31 = 2-07. The Htdeometee. Estimation of the Sjjecijic Grnvity of Liquids hy means of the Hydrometer. 310. The hydrometer is an instrimient employed to determine the specific gravity of liquids. It is commonly made of glass, especially when it is to be used with corrosive chemical liquids ; but, for a few special purposes, it is made of brass or silver. The usual forms of the glass instruments are represented by figs. 3 10 a, fe, loaded by ;v bar of lead, that when the brass weight is at the bottom Lif the mast the model, when floating in the water basin, will right itself after being dis- placed laterally ; but when the brass weight is screwed up to the top of the mast, the model will readily upset. The changes in the state of equilibriimi, and the passage from stability to instability, may be examined by gradually shifting the position of the brass screw. HYDEODYNAMICS. 351. The science of Hydrodynamics treats of liquids in a state of movement. A special department of this science is devoted to the art of conducting and raising water, and is called Hydraulics. Capillaeity. 352. The different conditions of equilibrium which have been illustrated in the preceding chapters suffer remarkable exceptions when the liquids are contained in very narrow vessels, or when we consider the action of the liquids in contact with the sides of the containing vessels. We can only refer to two or three particulars. Water, when poured into a glass vessel and shaken a little, wets the sides of the glass above the horizontal level of the mass of water, and the surface of the water assumes a concave figure. When a glass tube is dipped into water, the water rises round the outer sides of the tube to a higher level than the horizontal surface of the water. Inside the tube the water rises to a level more or less above the level of the water outside the tube, and assumes a concave surface. The height to whicli water thus rises in a tube increases as the diameter of the tube diminishes. In short, the elevation is inversely proportional to the diameter of the tube. different liquids have different ascensional powers. Experiments made at 65" Fahr. with a tube of -^ inch diameter, give the fol- lowing results : — Water rose about i-^- inch, alcohol J inch, nitric acid I inch, and essence of lavender -^ inch. Mercury, when poured into a glass vessel, recedes from the sides of the glass, leaving a space between the glass and the horizontal surface of the mercury. When a glass tube is dipped into mercury, the metal is repelled by the outer surface of the glass. Inside the tube, the mercury is kept down below the external horizontal level; it is repelled from immediate contact with the glass, and acquires a convex surface. The student is recommended to try these experiments with a little clean mercury and a variety of narrow glass tubes. G S'5 HYDEODTNAMICS. 353. Set of six capillary Glass Tubes, fig. 353, with japanned tin frame and trough, for the exhibition of capillary attraction. Price 28. 6d. 353- 354- 354. Pair of flatted Glass Plates, 4 inches by 3 inches, to show capillary attraction between surfaces, mounted in a japanned tin frame. Fig. 354- Price is. 6d. 355. Two Wooden Balls, i inch in diameter, to show capiUaiy attraction when they float in water. The pair, price 4(?. All these capillary instruments, when put into water, must be par- ticularly clean, and the tubes and plates should be wetted with dis- tilled water, some of which also should be put into the little troughs. 356. Capsule of Iron-xoire Gauze, which, when slightly oiled, contains water, and floats on water, showing the repulsion between water and greased surfaces. Price is. 6d. 357. Filtering Tuhe. acting by capillarity, 6 inches long, 1 inch bore, smooth at both ends. Fig. 357. Three for 6d. It often happens in chemical researches that when a turbid mixture has been well shaken, especially after boiling, the precipitate it contains slowly settles down and leaves a very shallow stratum of clear liquor upon its sui-face. By using a very narrow glass tube, cut off smooth and square at the ends, it is possible to remove from the surface of such a mixture a sufficient quan- tity of clean liquor for testing, without waiting till the mass of precii^itate subsides. The method is exhibited by fig. 357. The tube is made barely to touch the surface cif the liquor : it is not dipped into it ; no suction is applied, because the effect of capillary attraction is alone sufficient to raise the required quantity of clear liquor. When the mixture allows this abstrac- tion of clear liquor to be effected, it is, of course, much preferable to filtration. 3 5 8. Filtering Paper, a stout roll put into a tall nar- row jar, with some water coloured blue by indigo dye. No. 204 6, affords a good example of the ascent of liquids by capillary attraction. 35 7- THE PIPETTE. 83 358. a. Filtering paper, per quire. Price is. 6d. h. Jar, on foot, 10 by 2 inches. Price is. Pbessubb op Liquids propoktionate to Depth. 359. Particles of fluid, on escaping from an orifice, possess the same velocity as if they had fallen freely in vacuo from a height equal to that of the fluid surface above the centre of the orifice. — Torricelli. 360. Spouting Jars for illustrating Torricelli' s Theorem. — Japanned tin-plate, form of fig. 360, size 20 inches high, 6 inches diameter, with necks of glass tube, and stoppers. A. With two necks. Price 6s. B. With three necks (fig. 360). Price 7 s. 6d. If the vessel (fig. 360) is filled with water up to the mark d, and the apertures, a, h, c, are afterwards opened, the water will escape from them with very different velocities. At a the water will possess the same velocity as if its particles had fallen in vacuo from d to a ; at & and c the escaping currents will possess the same velocities as if the liquid composing them had fallen from D to 6, and from d to c. Observe that the metal necks of the apparatus are closed by corks, that the corks are perforated and pierced by small glass tubes, and that these tubes are closed by small stoppers of caoutchouc or cork till the time comes for showing the experiments. The Pipette. 361. The Pipette has been long used in chemical laboratories for transferring small quantities of different liquids from vessel to vessel. During the last thirty years it has derived increased im- portance in consequence of its great utility in the art of Volumetric Analysis. Figs. 361 to 367 represent some of the principal forms of the pipette. They are all open at both ends. The opening at the lower end is about ^^ inch in diameter. The opening at the upper end should be about -^ inch in diameter, the glass there should be about -^ inch in substance, and the end should be ground flat. The pipette should be held near the upper end by the thumb and middle finger of the right hand, while the fore-finger should be 81 HTDEODTKAMICS. sliglitly wetted and kept ready to close or open the npper orifice of the instrument. When the pipette is to be filled, the lower end of A \ 1^ V : a, / S jas u 361. it is to end to 362. 364. 36;. A 100 V 366. 367. be put into the liquid and the month applied to the upper su(i up the liquid. As that is sometimes poisonous, you must take care not to suck it into your month. Some authors recommend the pipette to be formed like fig. 368, with a bulb near the upper end, assuming that the liquid will, in case of need, rest in that caritv ; but that is really an inse- cure safeguard, for if the lower end of the pipette rises suddenly above the sur- face of the liquid, then the air rushes through the liquid in the pipette with such velocity as to force it into the operator's mouth. A safer plan is to mount any short pipette with a caoutchouc tube, as represented by fig. 369. The glass tube is held by the left hand at a, the liquid is sucked np till it is visible ni p n TiT>r>Ti Tvhirli the PAmitf^linTip. ^ho THE PIPETTE. 85 is pinolied by the finger and thumb of the right hand at h, and the liquid secaired in the pipette. Another plan, which a steady operator commonly finds suflioient, is to provide pipettes that are sufficiently long above the highest graduation, to enable him to see distinctly the height to vrhich he can safely suck up the liquid. Keeping his eye upon that mark he fills his pipette, and then quickly closes the upper end with his finger. In all cases the pipette is first filled above the mark by which the quantity for delivery is regulated ; then holding the instrument in a vertical position the wet fore-finger is to be slightly relaxed to let air enter and cause some of the liquid to fall, drop by drop, till the surface in the pipette meets the required graduated line. The liquid in the pipette is then ready for delivery. The pipettes, Nos. 363, 364, 365, 366, are graduated with one mark, a, or a 6, and when filled up to that mark, they will deliver at once the marked number of measures of any standard description, say 10, 20, 50, or 100 septems, decerns, centimetre cubes, &c. On the contrary, the measuring pipettes (figs. 361, 362) take up a quantity which, after adjustment, is to be delivered in partial quantities of i, 2, 5, 10, measures, &c., as the analysis may demand. For the accurate delivery of very small quantities, the pipette, No. 362, is the best to use, because, when it has been carefully filled and justified at 0°, it is possible to deliver one or two or five measures accurately, which cannot be dope with the pipette. No. 361, in consequence of the uncertain delivery of the lowest degree. Pipettes of the form of figs. 367, 368, are commonly used for taking liquids out of long bottles that have narrow necks. Finally, the simplest form of piptttes is a glass tube of uniform bore, and with both ends cut off square. A use of such a pipette is shown in § 357. But a tube with uniform bore, and no confined jet at the bottom, cannot be safely used for the delivery of very small measured quantities of liquid, nor will it safely carry large quantities, When mercury is to be lifted by a pipette, the bore of the pipette should not exceed -^ inch ; the substance of the glass should be nearly as much, and the upper end of the tube should be well ground, that the finger may have a firmer pressure. Pbiobs of Pipettes. Pipettes not graduated. 361. Plain pipette, form of fig. 361, 6-inch. Price 2d. 364. Bulb pipette, form of fig. 364, 2 ounces. Price 4^. Bulb pipette, form of fig. 364, 4 ounces. Price Sd. Cylinder pipettes same price as bulb pipettes. S6 HYDEODYXAMICS. 365. BuPj Pipettes, graduated to deliver one quantity. Form of figs. 363 to 566. s. d. s. I ounce I 100 Sep terns I 3 I cubic inch I = -xws gallon 1 100 sraiTiR 9 25 grammes 10 500 grains I 50 gi-amnies I icco grains I 3 100 grammes .. I 3 50 st-ptems I 361. Scale of Pipettes, namely, pipettes that are graduated from end to end, like figs. 361 and 362, to afford the means cf measuring any given quantity Tvithin the capacity of the instrument : — s. d. s. d. I ounce, in 8 drachms 2 o 50 septems. in 50 spaces 2 o I cubic inch, in tenths . . 2 o j looseptems, in 100 spaces 3 6 5 cubic inches, in fifths 2 6 : 25 grammes, in 50 spaces 2 o ICX3 grains, in 100 spaces 2 o | 50 grammes, in 100 spaces 3 3 500 grains, in 100 spaces 3 o I loogrammes, in loospaces 4 6 1000 grains, in 100 spaces ; 6 1 370. The Burette, or Pouret, is a modification of the pipette. having for object to reserve all the powers of the pipette as regards the transvasing and measurement of liquids, and at the same time to set free the operator's hands and permit him to apjaly his tests leisurely. Fig. 37c represents (ray-Lussac's form of burette, adjusted to an apparatus for showing the exact height of the liquor in the instru- ment. Fig. 371 is Binks's burette; fig. 372 is Mohr's burette. In this, the most perfect form of burette, the pipette has only the additions marked a and 6. The jet a is of glass; 6 is a metal pinchcock, crossing a caoutchouc tube, which it opens and closes at pleasure. The variety of pipettes, burettes, and other instruments requisite for the practice of Volumetric AhaJtisis, is so considerable, that we refrain from giving further details, and refer the reader to Griffin's • Chemical Handicraft,' in which work the subject of Volumetric Analvsis is treated at length. 370. PbICES or A TEW YAEIEIIES OF BUEIETTES. Gay-Lussac's form, fig. 3-0 I Binks's form, fig. 371 > AH at the prices named below. 3Iohi's form, fig. 5 7 2 J THE BUEETTE. 87 A. Contents, 50 septems, in 50 spaces. Price 2s. 6d. 15. „ 100 septems, in 100 spaces. Price 3s. 6d. C. „ 1000 grains, in 100 spaces. Price 4s. D. „ 50 grammes, in 100 spaces. Price 3 s. 6d. E. Mahogany foot for Gay-Lussac's and Binks's burettes, same as fig. 214. Price is. 60!. F. Mahogany support for Molir's burette. Fig. 372. Price 5s. Consult Griffin's ' Chemical Handicraft ' for full particulars of burettes, and their prices. 37°- 371- 372- Tots founded on the Pklnoiple of the Pipette. 373. The Mysterious Funnel, figs. 373 and 374; japanned tin- plate. Price zs. This instrument consists of two funnels, placed one within the other, and joined air-tight at the top. Fig. 373 represents the external appearance of the funnel; fig. 374 shows it in section. There is a small hole under the handle which communicates with the space between the two funnels. 88 HYDEODYNAMICS. 375. 374- Close the bottom of tte funnel by tlie finger, leave open tlie hole under the handle, and fill the funnel with coloured water; then close the hole under the handle and open that at the bottom, upon which all the coloured water will escape from the inner fimnel, but will leave the closed space full. The inner funnel may then he filled with common water, both the holes being kept closed. It is now in the operator's power to deliver the colourless water alone by opening the bottom hole, or the two kinds of water mixed, by opening also the hole nnder the handle. 375. The Magic Can, figs. 375 and 376; japanned tin-plate. Price 3 s. This instrument consists of two vessels, one within the other, as shown by the figures, where 375 represents the outside of the apparatus, and 376 a section of it. Under the handle is an opening which communicates with the space between the two ves- sels, and admits the pres- sure of atmospheric air when it is required. Leave open the hole imder the handle and fill the vessel with coloured water ; put down the lid and pour out the coloui-ed water from the inner vessel, keeping the hole under the handle closed. The vessel may now be shown to be empty ; but it deKvers a stream of coloured water when the hole under the handle is opened. 377. Robert Moudiiis inexhaustible Bottle for delivering four different liquors, size of an ordinary wine-bottle, with funnel and small wine-glass. Price 5s. This bottle, which plays a popular part in all representations of physique amusante, and with which one can dispense to each of four assistants a glass of wine at his choice, is made of tin-plate and painted to imitate a common black wine-bottle. It is divided within into four compartments, representing so many pipettes, each having the upper orifice leading to a hole in the outer surface of the bottle, where it can be safely closed by a finger, and a jet which represents the neck of the bottle. The compartments being previously filled with the four liquors, the process of giving to each person the wine 375- THE SYPHON. 89 that lie asks for consists in liberating tlie mouth of the particular pipette that contains the desired wine. The four holes in the outer surface of the bottle are necessarily so placed as to be manageable by the iingers and thumb of the operator's right hand. 381. The Syplion. — The syphon is a bent tube, one leg of which is longer than the other. When it is filled with a liquid, and the short leg is put into that liquid, a current runs out of the long leg until the supply of liquid sinks below the end of the short leg, when the action ceases. The two principal uses of the syphon are to transfer liquors from vessel to vessel, or to run off a clear liquid from above a sediment or a precipitate. The following figures show several varieties of the syphon : — M .2 'a""~ 382. Fig. 382, letters a, h, c, d, represent the simplest form of the syphon. As represented in this figure, it is set in action by air 90 HYDRODYNAMICS. Llown in by the tube, e, /; and, once in action, it continues to act till the liquor is all transferred, or tUl the tube, e,/, is stopped at e. There is an advantage in the arrangement shown in this figure as respects the operation of washing a filter, which goes on with great regularity when the water is driven over at a constant rate by the pressure of air in the tube e f. Fig. 383 represents a syphon with a suction tube. Fig. 3S4 represents such a syphon as 383 in action. To use it, the short leg of the instrument, c, is dipped in the liquid that is to be transferred, a finger is put on the end of the long tube, g, and the liquor is to be sucked up by the side tube at until it is seen to run over the bend at a into the long leg ; the mouth at the side tube and the finger at the bottom of the long leg are then to be removed. At d in fig. 384 is a laige mass of sediment or precipitate, from which the clear liquor is being syphoned. To avoid stirring up the mass d and mixing it with the clear liquor, the end, c, of the syphon is turned a little upwards. Fig. 385 is the ordinary form of the syphon when used in the arts. Fig. 386 shows a method of syphoning, in which every part of the apparatus is put under control, and which, therefore, affords a complete illustration of the operation. It consists of a bottle which contains the liquor that is to be drawn off; secondly, of a plain syphon passed through a stopper of cork or caoutchouc ; and lastly, of a blowing-tube, consisting of t^vo glass tubes connected by a caoutchouc tube, crossed by a pinchcock. Supposing the apparatus to be newly set together, you put the blowing-tube into your mouth, squeeze the pinchcock, and blow into the bottle, upon which the liquor passes through the syphon and escapes. If you wish that action to continue, you have only to slip the pinchcock from the caoutchouc tube to one of the two short glass tubes, when the operation proceeds ; but if you wish the action to stop, you remove the pinchcock back to the caoutchouc tube and permit it to press it closely, when the action ceases. Fig. 38- represents the application of a syphon to the decanta- tion of a solution, without the direct access of atmospheric air. Suppose it to be a solution of potash, contained in a stock-bottle, which is to be let off by the syphon from time to time in small portions for use as a test. The syphon is fixed, as shown on the figure, with a burette jet and pinchcock at the bottom. In the stopper of the stock-bottle is placed a tube, containing lumps of potash for absorbing carbonic acid from the air that passes through it. Under this arrangement the syphon remains always full of the testing-solution, and when a little is draxiTi off its volume is supplied by purified air that enters by the upper tube. THE SYPHON. 91 Fig. 388 represents a syphon, surmounted by a stopcock, to be used instead of a suction tube to set the syphon in action. B^'g- 389, the Wiirtemberg syphon. This acts like a common syphon, although the two legs are of the same length. When it is to be set in action it must be filled with some of the liquor to be syphoned, and then have one leg dipped into that liquor. J 390. Fig. 390 is an interesting example of the use of syphons iu the arrangement of chemical apparatus. The figure represents a pair of Mohr's burettes, fitted to two large stock-bottles for supply- ing countervailing solutions for volumetric analysis. All the parts from a to g stand on the worktable ; the other parts, Ji to Z, are mounted on a shelf. The purpose is to transfer from time to time small quantities of test liquors from the two bottles, Jc I, to the graduated tubes, d, e. These transfers are effected as follows : — Suppose a small quantity of test-liquor is to be passed from the bottle h into the glass beaker placed below the left-hand tube. The pinchcock / is opened, upon which the Kquor passes from the tube d into the beaker. The quantity is measured, not only by the gradu- ation on the vertical tubes, but by a circular line on the floats d and e, which serve to check the other graduations. When this small quantity of liquor passes out of the tube d, its place is immediately supplied by air, which enters from i by the syphon g, and afterwards the tube d is supplied with other liquor which comes by the syphon h from the bottle h ; but when this supply of liquor takes place, some 9'2 HTDEODTXAMICS. air must go out of the tube d to make room for it. Tliat air goes up by tbe tube g into the bottle 1-. fiut since a certain mass of liquor passes out of tbe system of apparatus into tbe glass beaker, an equal volume of air must come into it to preserve tbe equili- brium. That equivalent volume of air comes in by the tube /, in passing through ■which tube the air is deprived of carbonic acid, dust and other matters that might prove injurious to the liquor in the bottle Jc. Exactly what takes place Tvhen liquor is abstracted from the bottle k, takes jjlace also when a similar abstraction is made from the bottle I, where there is an equal arrangement of syphons and air tubes. Stphon Tots. 391. Tantalus's Cup.— A. glass beaker on foot, with a curved syphon within it. This glass can be fiUed with water nearly to the top of the glass, but not quite ; for when the water rises to the upper part of the bent syphon, the latter begins to act, and the water all runs out. The stem and foot of the apparatus are both perforated, and the lower end of the syphon is fixed there by a cork. Fig. 391. Price is. 6d. A short tube passes from the cork doicmcards, to carry off the liquid. 392. SempeVs Syphon, another form of Tantalus's Cup. — Xearly of the same construction as No. 391. The central tube, open at both ends, is part of the outlet tube; the tube that covers it is put over it loosely. When the water rises to the top of these tubes, it flows out by the syphon action. Fig. 392. Price is. 6d. 394. Sometimes Tantalus's cup is made of glass or japanned tin- plate, having within it a figure of king Tantalus, within which a 390. PRICES OF SYPHONS. 93 syphon is concealed. Water is poured into the vessel until it nearly reaches the lips of the figure, whereupon the syphon begins to act and draws off the whole of the water. The price of this toy is about los. 395. Fountain Syphon, or Eye Fountain, for bathing inflamed eyes, fig. 395, 24 inch. Price 6d. 392. 395- Peices of Syphons. 382. Gay-Lussac's plain syphon, 24 inch. Price is. 382 A. Gay-Lussac's plain syphon, fitted with regulating-bottle as represented by fig. 382. Price 3s. 6d. 384. Syphon with suction tube, 12 inch. Price <^d. 24 inch. Price is. ^d. 385. Syphon with suction tube, common form, 36 inch. Price IS. 6d. 386. Syphon apparatus, with blowing- tube, fitted for ex- plaining the theory of the syphon. Price 4«. 387. Syphon fitted to bottle for test liquor. Price 3s. 388. Syphon with stopcock. Price 3s. 6d. 389. Wlirtemberg syphon, 36 inch. Price is. 6d. Intermitting springs, desorilaed in another section, depend upon syphons for their action. Steinges. 403. Glass Syringe, about 8 inches long, I inch diameter, fig. 403. Price IS. 6d. 404. Glass Syringe, about 8 inches long, I inch diameter, with laent point, fig. 404. Price 2$. 403. 94 HTDEODTNAMICS. Glass syringes of smaller sizes, namely : — 405. 3 inches long. Price ^d. 406. 4 inches long. Price 6d. 407. 5 inches long. Price Sd. The pistons of all these glass syringes are solid and covered with cotton wool. The piston rods are guided by corks fixed in the ends of the tubes. There are no metal fittings. Glass Woeking Models or Pumps. 412. Lift Pump, a worTcing model in glass, with glass valves; size of barrel about 10 inches by ij inch; fig. 412. Price 4s. 6d. Figure d shows the construction of the piston c, which contains a valve that opens upwards. The valve at 6 is closed and weighted with mercury. When the ■o hi 412, piston is drawn up by the handle at e, the valve at 6 rises and admits water into the barrel of the pump. When the piston is depressed the valve in d permits the water to rise towards a, and the next stroke expels it from the spout of the pump. The water pan is not included in the price of the pump. A piece of caoutchouc tube can be put on the neck 6, and the pump can be mounted on a jar like the pump in fig. 425. 413. Force Pump, a working model in glass, with glass valves : size of the barrel about 10 inches by ij inch ; fig. 413. Price without the glass pan, 4«. 6d. The valves at e and g are both solid. When the piston is drawn up, the valve at e rises and admits water into the barrel a. When the piston is pressed down the valve e closes, and the water is forced through the pipe c, and past the valve / into the air- chamber h. Successive strokes of the pump cause the water in the air vessel to press strongly on the air contained therein, which in turn forces the water out of the pipe d in a strong jet. WOEKING MODELS OF PUMPS. 9;3 414. Force Pump, a worMng model, with large air-vessel similar to tliat of a fire-engine, made in glass, with coloured glass valves ; mounted on a maho- gany frame ; fig. 414. Price without the hasin, 8s. a is the force pump, 6 the air vessel, c a flexible tube carrying the jet pipe. 415. Fire Engine, or double- barrelled force pump, a work- ing model, made in glass, with coloured glass valves, mounted on a mahogany frame ; fig. 415. Price without loater basin, 12s. 6d. a, a, are the two force pumps ; 6 is the air vessel ; and c, a flexible tube carrying the delivery pipe or jet. 415 416. Fire Engine, a working model of a fire engine, or double- barrelled force pump, japanned tin-plate. Price 7s. This model will throw a jet of water to a distance of 20 feet or more ; but it cannot be opened to show the interior con- struction. The glass models are better adapted to explain the mode of action of a fire-engine. Working Models op Pumps, in Glass, mounted with Beass. 418. Valves. — Models of 5 varieties, namely, the butterfly valve, bellows valve, round spring valve, conical valve, and oil-silk valve, in stained hard wood, each 6 inches in diameter. Price of the set, I OS. 6d. 96 HYDRODYNAMICS. Valves are a species of flood-gates, that open a passage for a stream of liquid or gas in one direction, and close the passago against the stream in the contrary direction. These valves are models on a large scale of valves that are used for pump work. a. Butterfly valve. h. Bellows valve. c. Round gpring .■J'^^^ t~^ valve, ' '^ ^^* ' d. Conical valvo. e. Oil-silk valve. 421. Lift Pump, a working model, of a superior description, with stout glass Isody, about 7 inches long by li inch wide, mounted with brass ; fig. 421. Price without stand, i6s. 422. Force Pump, a working model, of a superior description, 421. 422. 425. SPEIXGS AND FOUNTAINS. 97 with stout glass barrel, about 7 incLes long by ij inch wide, mounted with brass; fig. 422. Price without stand, 25s. 423. Pump Stand, a polished mahogany frame with a japanned tin-jiiate water cistern, to suit either of the pumps, Nos. 42 1 and 422, as represented in these figures. Price 5s. 425. Tate's School Lift Pump, a worldiig model, large hut cheap, with a glass barrel about 10 inches long, and 2 inches diameter, mounted in. japanned tin-plate, with a wide trough at top, and stone marbles for valves. Price fs. 425 A. Glass Cylinder to contain water to supply this pump when in use; size 14 inches high, 4 inches diameter, with a board for the pump to rest upon. Price 3s. £d. This apparatus gives a continuous stream of water, and the action is visible by a Class. Before it is exhibited it must be examined, to see that the cotton packing of the pistons is in good condition. At first, some water must be poured into the trough d, to wet the pistons and enable them to commence action. 427. Water rises in Pumps in consequence of the pressure of air on the Water in the Reservoir. — The apparatus for this demonstration is represented by fig. 427. The part a, h, is the model of the working part of a common lift pump, see No. 421. At the lower part of this is a ground brass plate, to rest upon the ground neck of the receiver a, d. To the centre of this plate a tube can be screwed, which descends into the water jar placed under the receiver. When the air-pump is first worked, before the air is exhausted from the receiver, the water flows freely from the spdut; but, when the exhaustion of air is effected, the pump ceases to deliver water. When air is admitted into the receiver, the pump resumes its power to deliver water. Price of this apparatus, as represented by fig. 427, iZ. Springs and ForNTAiNS. 4-7 There exist a great variety of Springs and Fountains. Our apparatus afford illustrations of the following six varieties, viz. : — 439-445. Fountain produced when water falls from a high reservoir and supplies a jet. 446-459. When condensed air forces a water jet into free air. Condensed air fountains. J>8 HYDEODVNA:\nCS. 440. 460-470. When uncoiideused air foroes a water jet into an exhausted reocivcr. Fountains in vacuo. Heron's Ball. 4-1-475. When a column of water con- denses a confined portion of air iiud causes it to force a water jet into free air. Heron's Fountain. 476. When a fall of water from a syphon creates a vacuum into which a water jet is forced by free air. 4S0-4S2. When an interrupted supply of air causes a spring to be intermittent. 43q. Fountains produced when water fulls from a high n^servoir and supplies a jet. This is the ordinary method of supplying fountains for public garilens such as that of the Crystal Palaoo. The water is pumped up to a high reserveir and then allowed to descend through a system of pipes. With the following ap- pui-atns the experiment can be shown in a leetiire room. 440. Foinilain prodiwed bi/ a Fall of Water from an ciiiinriifc iiinlcr common at mosplu'fic pytVKure. — I'^ig- 440 represents an ordinary ChonicaJ (hw llohlcr. It is of a cylindi'ical form, and is nia(l(! of japanned zinc; the body is 18 iuehes high, and loi inches diameter; contents 1500 cubic inches. It is represented as standing on a table or shelf, and in use for hydraulic experiments. We shall, however, explain the references : a is the neck by which gas can be delivered into the gas holder, the 2 stepeoeks being closed at the time, upon wliieh water runs out of the neck a, bulk for bulk, with the gas that is passed in. p is a funnel by which water is J)ut into the reservoir. It is made 18 inches long, to give a pres- sure when required, g 1 d show the moans of passing out gas in any direction. At /( is a wide gauge-pipe, to show the level of the water in the gas liohliir at any time. The contents ai'O shown by a graduation into spaces of 50 cubic inches. SPRINGS AND FODNTAINS. 99 The fittings of the gauge pipe are so constructed that, if the glass ^iibe shoulcl happen to be broken, it can be easily replaced by another, the screw h being moveable. +40. Price complete, as represented by fig. 440, zl. 441. Price of the gas holder without the lower stopcock and ihe pieces marked t, Ic, 1 7. los. 442. Price of the lower stopcock, +s. 443. Price of the pieces i, k, viz., fountain jet and 6 feet of caoutchouc tube f inch bore, 6s. 444. Water Bottle, by which a supply of water can be provided for a fountain on a small scale. The bottle, filled with water, is to be placed on a high sheK, and the tube that is to supply the jet is to be fixed on the stop- cock c. 444. Price of two-gallon jar with brass cock, 7.1. 445. Price of five-gallon jar with brass cock. 13 s. 446. Fountains produced when con- densed air forces a water jet into free au-. There are thi-ee vai-ieties of this kind of fountain, Nos. 447, 448, 449. The condensed air fountains consist of a brass condensing-pump, or syringe, to which is connected a vessel for containing the condensed air ; this vessel is furnished with a stopcock which screws on the top, with a tube descending nearly to the bottom of the vessel : to the upper screw of the stopcock a tube and a variety of jets can be attached. Wlien used, the vessel is about half filled with water, and the condensing-pump being screwed to the tube and the stopcock opened, air is forced into the vessel, which, rising through the water, becomes condensed and presses strongly on its surface. After turning the stopcock, the syringe is to be removed and one of the jets being fitted to the tube, the stopcock is to be opened, and the air condensed within will force up the water in a jet, varying in appearance as the jet is varied. 447. Condensed Air Fountain, consisting of a glass globe on foot, in I piece, stout Bohemian glass, 6 inches in diameter, and nearly i inch thick in glass, with brass collar, water tube and stopcock. Fig. 447, which shows this fountain in action, when mounted with jet No. 447. Frice of glass fountain and stojK-ocJi, without jets, 3IS. £d. 447 A. The fountain, with the 4 jets complete. Price 52s. 6d. 44S. Condensed Air Fountain, large size, made of stout sheet 100 HVDHODYNAMICS. mil I ilill li I I wm I li! iiiliii ,; iili r>>y"\-«i 452. SI'EIXGS AND FOUNTAINS. 101 zinc, or zinced iron; size 12 inches in heiglit, 6J- inches in diameter, with extra neck, 8 inch water basin, and two stopcocks ; fig. 448. Price, without jets or syringe, 428. The use of the extra neck is to permit the supply of additional air while the fountain is in action. 448 A. The fountain with the 4 jets complete. Price 638. 449. Condensed Air Fountain, small size, brass cylinder, mea- suring 6i inches in height, 2^ inches in diameter ; fig. 449. Price, vjiih a stopcock hut without jets, 12s. 449 A. The fountain with the 4 jets complete. Price 31s. 6d. r.'- 450. Fountain Jets, a set of 4, figs. 447, 451! 45^, 453- They suit all the 3 fountains, and are sold either as a set or separately. Price of the set, 22s. Prices separately : — «. d. s. d. 447- 2 o I 452. 9 ^5 451. 5 o I 453- 5 6 10'2 HYDRODYNAMICS. Tho jet, No. 45+, is shown by jot No. 453, wlien uiuliu- strong prcssui'o. No. 452 is a revolving jet. Coiidi'ii^lng Siiriiiije for supplying air to tho fountains, fig. 455- 455. Small size. Pi-lrr Ss. 456. Large size. Price i6s. 457. Tlw Cliromalii- Fin' cIiiikL — Tlio chromatic firo-eloud is produced when tho air vessel is supplied with a strong solution of chloride of strontium and chhirido of copper in spirit of wine, instead of water. ■ Air is con- densed into it, tho stopcock closed, tho syringe removed, and a jet applied as above described. On tho stop- cock being ojiened tho compressed fluid is driven out with great violouee, and must be projet^tcHl on a wall or the coiling of a diu-koncd room ; a light should bo ap- plied to tho vapour on tho coiling, and small quantities of the liquid must from time to time bo ]ir(ijeeti:d so as to sustain tho flame. The effect produced is exceedingly brilliant, as tho luminous waves ai'e of almost every coloiu'. 460. Fountains produced when uncondensed air forces a water jet into an exhausted receiver. — Fountahis in vacuo. Three varieties, Nos. 461 to 463. 461. The apparatus represented by fig. 461 shows a method of making such a fountain by using the table of Tate's air-pump as a transfer plate. It is described in the article respecting that instrument, see § 5 1 6. 462. Fountain in Vacuo. — Fig. 462 shows tho Single Trniisfcrrcr (fig. 627) in active use. Price of Iraiisfer plate 011. inm foot witltoiit basin and receiver, 17*. 6d. The transfer plate can be unscrewed from its wooden base (fig. 627) and bo fixed to the pump plate by its screw. A receiver may be placed on the plate of the transferrer, and be exhausted ; and the stopcock, being turned ofi", the receiver may be removed from the pump, and be placed on a suitable support. If then a water tube is attached below, and a jar or pan of water supplied, it is only further necessary to open the stopcock to produce a fountain in the receiver ; see fig. 461. In fig. 462 the transferror is supported by a special foot screwed on the stopcock. 463. Fountain in vacuo, without a tranxfer iilate.- liepniHentod by fig. 463. The glass receiver is mounted with a collar, a stop- cock, and a fountain jet. It is exhausted in tlie usual way, then removed from tho air-pump, screwed upon a foot, and placed in a water pan. The stopcock being then opened, tho jet is formed in the receiver. If .desired, the stopcock can bo screwed to a water SPRINGS AND FOUNTAINS. 103 tube, and set on a water bottle like fig. 461. Price of fountain on foot with receiver, hut without the water basin, 24s. 461. r^ mk 467. Heron's Ball, to produce a fountain in vacuo. — Tbis apparatus consists of a glass flask one-balf full of water, into whicb a glass tube, dipping into the liquor, is securely fastened by a cork. When tbis flask is placed under an air-pump receiver, about to be exhausted, the subsequent expansion of the air witbin tbe flask forces the water through the tube, forming a fountain in vacuo. If air is admitted into the receiver, the effect instantly ceases. A. Size of flask, 3 ounces of water. Price is. B. Size of flask, 6 ounces of water. Price is. Any glass receiver sufficiently wide and tall may be used for this experiment. The moveable pump plate (No. 563) may be used, with a view to keep the water from the pump itself. 468. Heron's Ball, a more elegant form, globular glass on foot, 101 IIYDRODYNAMIO*. with brass fittings ; fig. 468. Prire urilhiut tlm riimrcr and glass basin, 6s. 471. Fountains produced wlion a column of wuicir <',(iii(1(!Iik('h a oonfiiiod portion of air and ciuiscs it to ionto a \val13r jet into fino air. — Heron's J''iii. 472. Heron's Fountain, for showing tho olasfcic force of (imri- pressed air; the middle iubo and half of oach ball hIioiiUI contain air; the rest be filled with water, iiicliidinR the fiiinicl. a. Price, mounted mi a maliogany stand liku fig. 472, hilt without the glass cistern, 5«. b. Price of the glass fountain not mounted, 38. 473. Heron's Fountain, anothdi- pattern, and stylo of mounting, as shown by fig. 473. Price with wooden foot, Cs. 47i. 47;i. SPEINGS AND FOCNTAIXS 105 The fountains (figs. 472, 473) ara charged with water by partly filling them at the top, and then turning them upside down for a short time. When they are properly charged, the action is kept np by pTitting water into the funnel. Care must be taken to use water free from bits of straw, or other material that can stop up the jets. 474. Heron's Fountain, made of japanned tin-plate, height about 15 inches; figs. 474, 475. Price 4s. Atmospheric air is capable of being condensed or reduced in volume to a very considerable degree ; but, when it is thus compressed, it has a tendency to recover the same volume or space which it originally occupied, and hence exerts a pressure on the objects by which it is enclosed. The action of Herons Foun- tain depends mainly upon this principle. The upper reservoir a being first filled with water at the opening c, which must then be securely stopped by a cork, water is poiired into the basin d at the top of the reservoir. This water runs through the tube e into the lower reservoir h, which had previously con- tained nothing but air. Till.' air, being compressed by the entrance of the water, forces its way up the tube / into the upper reservoir ; here, finding no vent, it acts like a spring on the surface of the water in the reservoir, and forces the liquid out through the jet tube g I, thus producing the very pleasing elfect of a miniature fountain. When the fountain ceases playing, the water may be drawn ofi" by withdrawing the cork from lihe opening in the lower reservoir ; but at all other times it must be kept carefully closed. The other columns have no connexion with the interior, and are merely intended as supports. This fountain derives its name from its invtntor. Heron, of Alexandi-ia. 476. Fountain produced when a fall of water from a syphon creates a vacuum into which a water jet is forced by free air. 477. Fountain produced by the action of a syphon. Price of the syphon, consisting of 3 glass tubes and a carl:, 4s. €d. 474- 106 HYDRODYNAMICS. Price of the iron support, g*. Price of the glass heaher, is. The pieces of tMs apparatus being put together as represented in fig. 477, and the beaker being filled with wat^r, the fountain is set in action by sucking air from the lower end of the long tube. The pressure of the atmosphere upon the water in the beaker then forces a jet up into the fountain glass. The proper play of the apparatus depends upon the proportions which the orifices of the two tubes bear to one another. 477- SPRINGS AND FOUNTAINS. 107 480. Infpymittent sjjriiKju. 481. Glass model of an intermiilinij spring (fig. 481). s. ,1 Price of the flask and funnel A b, with the tubes attached . . . . . . .50 The glass receiver, c . . 20 The tall iron stand . . . . ..go The set complete 16 Use. — The stand, the receiver C, and the funnel are first arranged ; the flask A is then nearly filled with water, and the cork with tubes is adjusted at c. The tube a goes into the funnel a little more than halfway down. Some water is put into the funnel to cover the lower end of the tube a. The whole is then in working order, providing the tubes are all clean and clear. Tlie action is as follows : When the pipe d has carried off some of the water from the funnel, so as to uncover the lower end of the tube a, air passes through that tube up into the globe a, where- upon the water in the globe passes through the four narrow delivery tubes into the funnel, in which it accumulates so as to stop the passage of air up the tube a. The action of the fountain then ceases, until the outlet tube d has again liberated the end of the tube a ; and thus an intermitting action is sustained, until the water in the globe A is exhausted. It is of importance to regulate the flow from the jet d. If it is either too slow or too rapid, the action ceases. But it is easy to keep it in order. All the pipes must be kept clean. 482. Glass model of an Intermitting Fountain. — The description of the Inter- mitting Spring (No. 481) applies pretty well to this apparatus also. A fall of water from the lower mouth of the water bottle causes a fountain to rise in the funnel. The water speedily rises in the funnel and closes the lower end of the long tube that carries air to the upper part of the water bottle. When the supply of air is thus cut off, the water ceases to run out of the bottle and the fountain ceases to play. But in the meantime the water flows from the funnel into the glass pan, and sets free n>s HYPROIANAMICS. tlio air tube in t.lio funnel, and tlio action of the appitratus ilopoiuls a good (leal upon tlio regularity of tlmt 1low of water froiu tho fuiuiol. Tho lioiglit of tlio fountain in tlio fuuuol ilopt-mls upon the length of the two tubes tliat sepavafo the fuuiiol from tho botiK- : the louger tliese tubes, the hiuher is the jet. .-•. ./. Priee of the fountain without the stand .. .. 6 (.< iron stand ,. .. .. . q o water basin, 6 inebes diameter l ^ Complete l6 6 A\'atehwokks. 486. ]Vatrr-tr]irch. a set of working models, made of tlii-pbite, japanned green, and consisting of nu ovev-sbot wheel, im under- shot wheel, both wlieels being 8.\ inebes in diameter; a water cistern, a frame to sujiporl tho whole in aetiiig position, and a jiau to reeeive tho spent watt-r. ■l.-.O. Both wheels work at tbo samo iimo. Tlio water lead must, be so adjusted, by gently bonding tho gntteis, that not too niueli water is supplied to tho ovrr-sliot wheid. Fig. 486 sluiwH tho two whools in aetiou. Fig. 48-7 shows tho mode of adjusting one of WATEKWOBKS. 109 the wheels, so as to make it act as a breast wheel. Price of the sut in a box, 31s. 6(7. 488. Archimeduiii Screw, a working model consisting of a metal pipe wound round a cylinder, mounted on a metal frame over a water cistern, japanned. Price los. 6d. 489. Glass Arcliimcdian Sc7-ew, mounted on a japanned metal frame, more elegant than iho above. Price 21s. 4»9- Before using the screw, at u, lecture, a small marble ball, half an inch in diameter, should be passed through it, from below up\vai-ds, to prove the passage to be clear. 490. Appold's Ccnlrifiiijal Pump, a working model, which gives a continuous stream of water ; the acting centrifugal wheel is if inch in diameter; it is accompanied by a separate model of the wheel 6 inches in diameter, which is one-half of the diameter of the acting wheel of the large or "lass 4'ji. J 10 HYDRODYNAMICS. pump that was shown at the Great Exhibition of 185 1. Fig. 491. Price of the set, 4Z. " The most advantageous application of Appold's pump is in raising large quantities of water to small altitudes ; for example, it has been very successfully employed in draining fens, &c." — Broolce. 490. PNEUMATICS. AIR-PUMPS. 501. Air-pumps of the most improved forms, and guaranteed to he in perfect action. All the screws of pneumatic apparatus are made of the same size and thread, so that the several pieces are easily fitted to one another. If an air-pump is not used for a considerable time, the various parts require the addition of a little oil, which may be easily applied by pouring a teaspoonful into the centre hole in the brass plate, as shown at a, fig. 503 ; when a few strokes of the piston up and down will convey the oil to all the internal parts, and the machine will be in good working condition. The ground edges of all receivers should be smeared with tallow prior to being fixed on the .air-pump plate. See 639. Stopcocks should be always laid aside open ; and when a pump is put aside the blank nut, letter s, fig. 505, should always be screwed into the plate, to prevent the entry of dust. 502. Exhausting power of the Air-pumps described in this section. — I have added to the description of each pump a reference to its ex- hausting power. It is proper to state in what manner these powers were ascertained. This was by trial with syphon gauges. The pumps were new, and therefore in good order ; the joints screwed tight together ; the washers, the inside of the pumps, and the leading tubes were well supplied with oil; the receivers were carefully ground on the edges and greased with tallow ; and the mercury in the syphon gauges which were of the form represented in fig. 577, and of which several were used, had been recently boiled in the tubes. The temperature of the room in which the trials took place was about 55^ Fahr., and the barometer stood at 30 inches. The results are quoted in the table (see page 112). The Besidues of air left in the receivers, according to these indi- cations, are as follow : — J^'inch = I in 600 -j\ inch = I in 300 \ inch = I in 240 •j\ inch = I in 1 60 ¥ ■ i inch = I in 80 112 PNEUIMATICS. 1. 2. 3. 4. 6. The kind of Pump tried. riiipaciiy ol Urcdvcr, Ciip;ioiiy of Itivcivrr, ('!i|};u-lly of llru'lvcr, C'lpucity of U.'n't\HT. Under colnniris 2 to ^ ia shown the <)(■>-) 280 8() 25 atmospheric pressuri' indicated cubic iiirln's ; cubic inclios ; cubic iiicbcs; cubic luclir.s ; by tha s.rphon gtinRes nt tUe its b.iMf, its bnsi', lis buBi', \i'^ l)iiM', point of greaieBt exhaustion. 9 iiichfS diameter. 7 Inclirs dlaiiii'ler. 4 inches (lliinirtt'f. 2 Inclii'S (llunickT. inch. llH'll. inch. inch. 503. 2-bari'cl pump, 8-inch \ plate 1 I ;i 1 i 8 504. 2-b;xrrel pump, lO-V ., 1 i inch plalo J S 1 505. Tiite's pump, 7-inoli\ plate ( 1) A ■i 519. Tale's large io-inch\ plate j 1 ] ] s 1(» i:t 520. 3-barrel pump, 10- inch plute, when Uir. , 1 vertical barrels v/m: " ■I " used ,1 S20. ;-)>arrol pump, lo-jl inch plate, wlnai the , J 1 ■i\i horizontal pump was i'' used 521. Pump with fly-wheel | J T) r TO Poircrs of Syphon Gaiu/cn. -Foi- tlio sako of thost: who may wish to try the power of their pumps in this manner, I may add to tho conditions of trial ahove cited a caul:l(jn respecting the syj)hoii gauges. In their ordinary (-Dudition — tliat is to say, after having been for some time oxjaisid to the air — tho syphon gauges arc, of no use for such trials as tltuso recorded above. For such experi- ments tho mercury must be rr.cnithj hnilcil in t/ir. (jiriiijr.f, and tlien tliey retain the power of giving accurate results for oidy a short time. If they arc exposed for two or three days to tlio air, they lose their power. If on the day they are made llu-y are put under a receiver, and repeatedly exhausted and refilled witli air, they are thus, deprived of their proper power. The air in tho gauge gets among the mercury, and puts an end to its accurate indications. When the exhausting power of a piiinii is tcslcil by a gauge thus deteriorated, the exhaustion appears to be much greater than it actually is, even when the quantity of air in the gauge is so small that it cannot bo scon as a bubble in tho nierenry, eillKir by the naked eye or with a lens ; wliilo the oxistcnee in tho gauge of a very small vixilile bubble of air -will enable the pump to rodu(a_; tho mer- cury in the closed limb of the gauge lower tlian that in the opon limb : in other words, the exhaustion will appear to take out of tho AIR-Ff:iIFS. 113 receiver more air than it contained, and thus reduce the atmospheric pressure to less than nothing. Just as it is possible to make the power of a pump appear to he better than it is by usiug a fallacious gauge, so it is possible to err the other vraj, and by neglecting to take the precautions which I have pointed out, make the power appear to be worse than it is. A pump cannot, indeed, be always Heir ; but it is always possible to see that its pistons and valves are in good order, that the pump is clean and well oiled, that its parts are screwed tight together and fixel firmly to a table, and that the receivers are ground smooth on the edges, and are clean and properly greased. Without taking these precautions, a pump cannot be made to work well. Xotwithstanding what is said above, the syphon gauge is highly useful for comparative experiments, and to indicate results ap- proximately. I have not stated in the trials recorded above the number of strokes that are required to produce each eftect : that indication of power is much subject to variations from accidental circumstajices, such as the gi-eater or lesser rapidity of the struk?s, and the greater or lesser accuracy with which the piston of Tate's pump is driven or pulled home to the end of the barrel at each stroke. Xeither have I answered a question that is frequently asked — How many minutes will it requii-e with a given pump to freeze water '? Generally, I may say. that any pump will freeze water over sulphuric acid, if it will produce pretty readily a vacuum indi- cated by ^ inch of mercury in the syjihon gauge. But one cannot fix the quantity of water to be freizen and the time to effect the freezing without knowing the power of the pump, the size of the receiver, the strength of the acid, the temperature of all parts of the apparatus, of all the materials to be used, and of the room iu which the experiment is to be made. Such details camiut be entered into in this note. Some readei-s may, perhaps, consider that the exhaustions quoted in the above table do not indicate ver v- accurate pumps ; for it is very frequently stated in books that double-barrelled pumps will exhaust to i in looo, when the mercury in the gauge will be at -[J^j inch. No doubt, air-pumps at three times the cost of any in this list could be made a Kttle more accurate than these are : but I fancy that when the above statement is made as regarding ordinary working air-pumps, due care has not been taken to distinguish the power of the pump from the fallacy of the gaTige. Eecetvees of various forms and sizes suitable far experiments mth the different air-pumps are described between Xos. 8co and 900, and also in connection with the principal experiments. I 114 PNEUMATICS. The pumps are without receivers or other separate apparatus, at the quoted prices, unless otherwise described. 503. Air-piimp, double barrels, 6^ inches long, l^-inch bore, 4|-incli stroke, with. 8-inch plate, on mahogany stand, and stop- cock between the plate and the barrels. Fig. 503. Price 81. 8s. Exhausting power of this pump, see § 502. 503. 504. Air-pump, double barrels, 7 inches long, ij-inch bore and 52-inch stroke, with lo-inch ground plate, on mahogany stand, supported by four pillars, with small gauge plate, mercury gauge, and key. Pig. 504. Price 14Z. Exhausting power of this pump, see § 502. 505. Tate's Double-action Air-pump, which contains two pistons in one barrel, takes in the air from the receiver in the centre, and expels it at the two extremities of the barrel. Length of barrel, 16 inches; bore, ij inch ; stroke, 85^ inches. It has a 7-inch plate, a syphon-gauge, marked r, and a screw, marked n, to enable the pump to be used as a condensing-pump. It is mounted with a massive brass clamp, by which it can be securely fixed to any solid table. Fig. 505. Price 3Z. 13s. 6d. AIR-PUMPS. 115 A brass cap to collect the oil ejected at the valve n, is included in the price of the pump. It is shown at fig. 517. Exhausting power of this pump, see § 502. 505. 1 a IK! rN'Er:\[ATics. It will freeze wntor ovor sulphuric ncid in ftrooeivorof 300 iMibio inches, in 150 stvokes nt about 60"^ Fahr., and in lialf tliat number of strokes at about 40° Fabr. 506. This air-pump is made on the pviiiciplo first explained by Mr. Tate (^seo his paper 'On a uew denble-aeting air-pump, witli a single cyliuder,' in tlie ■ Phibisoptiieal ]\[aga/.ine' for Aj>ril, l8i;6). It is represented iu perspective by lig. 505, smd its barrel in section by figs. 507 and 508. The ret'ereuces iu the following description ai'e made to these three figures. The bai'rel a, h, is a brass cyliuder, 16 inches huig, with a boro of ij inch diameter. It contains two pistons, c and d, ligs. 507 and 508, which are both attaidied to one piston-rod, c, moved by tho handle,/. Tho cylinder is firmly fixed iu a horizontal jiositioii to a table by means of a massive brass clanij), ;/, tig. 505. Other methods of fixing it are shown in tigs. 517 mid 518. The pump- table, h, which is made 7 inches or nuue iu diameter, is tixod above the middle of the bai'rel by the block /, and tho stopcock h. There is an aii'cock at/, to let air enter into the nceiver »(, when requiicd. At the end of the barrel n, there is a small orifice, with a valvo opening outwoi-ds; this is covered by a brass cap, which has an external male screw. At the other end of tho barnl, 0, there is also a small orifice with a valve opening outwards, and covered with a brass cap terminating in a bent p pe jj. 509. To ascertain if tlir rmiiji in in aood ii-oi-l-iiiij onlo-.— Clamp tlio pump firmly to a table, so that wben the ]iisl.oii-rod is pushed in, and pulled out, by means of the handle/, as far as it w ill go, tliero is no vibration of the table h. If the jwmp works st idly, pour a little iieat's- foot oil into the hole iu the middle of the table h, alter removing AIB-PCilPS. IIT the SYphon r, and opening the stopcock h The oil will descend into the barrel and lubricate the pistons, and will afterwards be gradually forced out at b^ith ends of the cylinder. The pipe p is so bent as to throw the ejected oil on the piston-rod, which must always be clean and well greased. The oU which is projected from the end n is collected in a brass box. which is represented in figs. 517 and 5 1 S. but not in fig. 505. This box must be often emptied. It sometimes happens that when a pump is new the pistons set, or hecome fixed. In that case, after clamping the pump firmly to the table, yon may poll out the piston-rod by main force. No harm will occur if you apply only as much force as is necessary for this ptrrpose. The handle / must always be in a horizontal position, to be conveniently grasped by both hands ; but as the piston easily turns round in the cylinder, the handle often comes into a vertical position. In that case, you must put it into the horizontal position by turning it from left to right, and not from right to left, other\vise yon may unscrew the piston-rod from the piston. Supposing the pump to be in working order, you must see that the plate h is clean, and that the receiver m is also clean, perfectly drv. and well sreased on the flattened edge with tallow, or a mixture of wax and taUow, according to the temperature. This grease can be conveniently applied by means of the tallow-holder described at § 639. When the receiver is thus placed on the table, it is easy to ascer- tain by a few strtikes of the piston whether the junctions are all tight. If they are, the receiver soon becomes fixed to the table ; if not, yon must search for the leakage. Ail the parts of the pump should be tightly screwed up. Wherever there is a joint, there must be an intermediate oiled leather-washer, and this washer must be always clean, and soft with oU, and from time to time it must be examined, and if defective, renewed, § 611. When the leakage is not at one of the joints, it is commonly found to be between the receiver m and the table h. If it is owing to defective grinding of the edge of the receiver, and that detect is but slight, a little more tallow may cure it ; but if the grinding has been insufficient, or if there is a chip in the glass, the rim must be re-ground. If a few strokes of the piston are found to fix the receiver upon the plate, the pump is in working order. See §711. 510. Action of this Pump. — The two pistons can be pushed into the positions shown by fig. 507. In this case there is a communi- cation between the receiver m, and that half of the barrel which is marked a. I assume that the stopcock k is open, and I shut This refers to fig. 505 . The pistons can now be pulled into the positions shown by fig. 508. There is then a communication between the receiver hi and that part of the barrel which is marked 6. By this 118 PNEUMATICS. second motion, all tlio air that was in tlio front half of the barrel a, is forced out of the barrel tliro\i,L;h fho valvo at the oml, o—ncmiij all, but not quite all; for a .smiill quantity of air rcniaius in the little pipe between the piston (/ and tho valve in o, and this expands into tlio half cylinder (r, and into the receiver v), wlicii the pistons are again put into tho positions shown by fig. 507. In lliat third niovenieiit, tho air contained in tho half h, of tho barrel, as shown in fig. 508, is forced out tlirongh the valve at the end -it, except, as before, a small rosidiie in the pipe between the piston r., and tho valve in n<. That this residue may be as little as possible, tho jiistons must at each movemoiit&e driven, quite linmc. But this must be done firndy and steadily, not with too much violence or too much rapidity. The operator must remember thiit all the air that is expelled at each stroke has to pass throuj^h an opening which is, for the above reason, made as small as possible, and he must not give this little hole and the valve belonging to it too much work to do. If the barrel of the pump, and above all, the stuffing-box, q (fig. 505), becomes hot to tho hand during the pumping, the operator is pumping too fast, and he must work more deliberately. Another precaution which he must take is, to work the piston-rod as evenly as he can in the direction of the cylinder, and not to make it waddle in the stuffing-box, q. If it waddles, the hole in the stuffing-box will speedily become enlarged, the pump will leak seriously, and the stuffing-box will require to be re-packed — work for tho instru- ment-maker. The exhausting power of the pump is tried by means of the syphon-gauge, which is marked r in fig. 505. That this may show the state of the exhaustion in the receiver m, a li(de is bored in tho brass foot by which the gauge is screwed into tho hole in tho table. With a receiver that is capable of holding 100 culjic inches of air, Tate's pump of the above size, and in perfect coTidition, will bring down the mercury to one-tenth of an inch in about 60 strokes. It will also readily freeze water over sulphuric acid in a flat receiver of 300 cubic inches ; but the requisite number of strokes for this experiment varies greatly with the temperature of the watir, and of the apparatus, and the apartment, from 150 strokes at between 60° and 70° Fahr., to half that number at between 30° and 40° Fahr. The other pieces of apparatus shown in fig. 505 are, a screw, », adapted to the hole in the table, h, and intended to prevent tlio running of water and mercury into the barrel of tho puin]), when spilt in certain experiments on the table, h ; tho jet t, and tho wator- j)ipe u, are for the oxiieriment called a fountain in vacuo, which 1 shall describe presently. 511. JJge as a Condensing Pump. — If a globular vessel mounted with a brass cap, containing a female screw, is adapted to the screw AIK-PDMPS. 119 at the end of the barrel n, the air which is there ejected from the pump will be necessarily forced into the vessel so placed to receive it. 512. Advantages possessed hy Tate's Air-pump. — There is no valve placed between the receiver and the barrel of the pump, so that when the air becomes rareiied it is not required to lift a valve, but has simply to difFuse itself as each half of the barrel is alternately opened to receive it. The pump is not difficult to work. Though the barrel is 16 inches long, the effective stroke is only 8 inches. At first, the friction of two pistons makes the pull rather stiff, but as the exhaustion proceeds the pull becomes easier, because the action of the external atmosphere is cut off from the pistons by the valves placed at o and n, which is the reverse of what occm-s with all pumps that have valves placed between the cylinder and the receiver. Tate's Pump compared with Air-pumps icith doiible barrels. — Though Tate's pump is a great improvement upon all single-barrel air-pumps, and does the work of exhaustion thoroughly, yet as its power is only in proportion to the capacity of its barrel, it does not work with sufficient expedition for a lecturer who desires to perform a series of experiments before a large, and perhaps an impatient, audience. T^'hen the size of the barrel is much enlarged, the labour is too heavy for the operator's hand. The piston-rod must be worked by a rack and pinion moved by a lever, and the apparatus then becomes expensive. To meet the necessity of a more rapid, though less effectual ex- haustion, recourse is had to air-pumps with double barrels, two common forms of which are represented in figs. 503 and 504. Fig. 504 is a pump with a raised plate and a syphon-gauge. Fig. 503 is a pump of a cheaper construction without a syphon- gauge. It is also represented in the figure without a stopcock between the receiver and the barrels, which is a very nnadvisable piece of economy, because it presupposes an absence of leakage at all joints of the pump, which, though desirable, is not always obtain- able, especially when the pump is old. In fact, this pump is now supplied with a stopcock. In pumps of this description, with vertical barrels, there are valves in the pistons, and also at the base of each cylinder, and the exhausting action of the pump ceases when the rarefied air in the receiver is no longer able to lift the lower valve when the piston is drawn upwards in the barrel. The labour of pumping increases with the exhaustion, and with wide barrels is considerable, because you have a vacuum under the piston and the full pressure of the atmosphere upon it, whereas in Tate's pump the pressure of the atmosphere is cut off from the pistons by the valves, which open outwards only, at the two ends of the barrel. 120 PNETOIATICS. When rapid action and complete exhaustion are both required, it is advisable to use the large size of Tate's pump. No. 519. 515. Fref'zing of Water. — With the help of Tate's air-pimip, the porcelain acid-pan, fig. j, and the flat receiver, fig. h 5 1 8, it is easy to freeze water. The pan must be half filled with concentrated sulphuric acid, not the fuming Nordhausen acid, but oil of vitriol that has not been diluted. The water should be put into a watch- glass, placed upon the acid-pan. This experiment succeeds best when the pump, the water, and the air of the room are as cold as possible. The pump and every part of the apparatus being in good condition, it takes twice as many strokes of the piston to freeze water when the air is at 60° Fahr. as it takes when the air is at 40° Fahr. In winter, when the apparatus and water are tolerably cold, Tate's pump will freeze the water with less than 100 strokes. In summer, at about 60°, it will require at least 150 strokes; and if you allow the water and pump to stand in the sun till they are warm, or if you take diluted acid, or too much water, or too large a receiver, you will entirely fail to freeze the water. A small quantity of water is, of course, more easily frozen than a large quantity; but when Tate's pump (the small size) is in good condition, and the weather cold, three or four ounces of water can be frozen, if placed in a thin porous earthenware capsule. As Tate's pump is usually sold with ad- juncts for producing a fountain in vacuo, I shall add a description of that experi- ment. 516. Fountain in Vacuo. — The table Ji of Tate's air-pump can be unscrewed in com- pany with the stopcock l; from the block i, fig. 505. The jet t can be screwed into the hole in the middle of the plate h. The pipe M, fig. 505, or a, fig. 516, can be screwed to the stopcock A-. These letters refer equally to figs. 505 and 516. Process. — The pump being in good work- ing order, ascertain that the table h and stopcock k are easily removable. Screw up tight, put in the jet t, cover with the coni- cal glass receiver B ; or, in default of that, with the cylinder of the guinea and feather glass closed at top with a well-greased glass AIE-PUMPS. 121 plate. Have ready a wide-moutlied bottle or jar, a, filled with water neai-ly to the neck : also a thin disk of glass, wood, or mettil, with a hole in. the centre, c. Exhaust. Close the stopcock h, and then unscrew it. and all above it, from the pump. Put on the disk 0, screw on the pipe a, and place the whole upon the glass bottle A. If the stopcock t is now opened, the weight of the atmosphere acting on the surface of the water in the vessel A forces the water, in the form of a jet or fountain, up into the exhausted receiver b. As this experiment wets the plate and stopcock of the pump, and renders them unfit for other experiments until thoroughly dried, it is better to use for it a separate small table and stopcock, which is commonly called a transferer. See §§627 and 462. When a teacher has no separate transferer, it is better to defer experiments with water till the other experiments of the same day's lesson have been performed, because it takes some time to diy the ti'ansfer-plate and the stopcock sufficiently to enable other exhaustions to be made by the pump ; for the presence of vapour diminishes its power. See § 462. 517. Tate's Air-pump, of the same form and dimensions as Xo. 505, but mounted on a solid and elegant japanned iron pedestal, repre- sented by a, fig. 517. Price of the pump on pedestal support, with syphon gauge, 3Z. 13 s. 6d. The prices of the exti-a pieces represented in fig. 517 will be found at the follo'n'ing numbers :— &, at No. 561 ; c, at No. 562. 122 PNEUMATICS, The pedestal requires to be screwed to the table where the pump is to be used. The pump is then perfectly soHd. On the other hand, the clamp (fig. 505) is useful when the pump has to be carried about for use in diiferont localities. The round box represented at the far end of the pump cylinder in figs. 517, 518, and 520, is intended to catch the oil, of which more or less is expelled from the pump with the air at every stroke. There is a hole at the upper part of the box to let out the air. From time to time the oil should be removed from the box. Though not shown at fig. 505, this oil-box is now sold with the pump, No. 505. Exhausting power of this pump, the same as that of 505. 518. Tales Air-pump, same form and size as No. 505, but mounted on a solid iron table, a, fig. 518, which has four legs screwed to an iron plate, 6, which plate can either be fixed permanently to the work-table by four screws, or be fastened to it by the large iron clamp, c, which permits the removal of the pump. Price of the pump and table, a, h, with the common syphon gauge, d, fig. 517, 3Z. i3«. 6d. 518 A. Extra fittings for any of Tate's pumps, as represented by c, d, e,f, g, g, h, i,j, k, I, fig. 518, cost 2I. 2S. AIR-PUMPS. 123 Exhausting power of this pmnp, the same as that of Xos. 505 and 517. The three pnmps are of the same size and power, they differ only in the style of mounting, and are supplied at the same price. 519. Tate's Air-pumj), of the same form as the preceding, No. 518, hut of ahove double the size and power, namely, with a barrel of 17 inches in length, ij-inch bore, and 9-j-inch stroke. It is mounted on an iron table similar to a, h, fig. 518. with a plate of 10 inches diameter, and supplied with the extra joint and arm marked 6, c, in fig. 517, and the gauge marked Z, in fig. 518. This is the largest and most powerful form of Tate's air-pump which can he con- veniently worked without rack-work, lever, or other machinery. It gives great power, is pretty easily worked, and is sold at a mode- rate price, 8Z. Exhausting power of this pump, see § 502. 520. 12-i PXEUlIiTICS. 520. Air-pump with three Barrels, serving either for rapirl action at lectures, or for more complete exhaustion for researches, fig. 520. Price, without the jar and rod, h, i, 18?. Exhausting power of this pump, see § 502. This apparatus consists of an air-pump with two vertical barrels, marked a, b, in fig. 520, which are worked as usual by the handle c acting on rack-work. Bore of the vertical barrels, if inch ; length of barrels, 7 inches ; stroke, 5^^ inches ; diameter of the pump-plate, 10 inches. ^Vith this arrangement, large receivers, having, for example, a capacity of a thousand cubic inches, can be rapidly and easily exhausted till the mercury in the gauge falls to -J inch, and small receivers can be brought to a vacuum of j inch. This is sufficient exhausting power for most of the experiments that are usually exhibited at lectures to illustrate the principles of Pneu- matics. But, as more perfect exhaustion is sometimes required, a separate pump on Tate's plan is added to the vertical pump. VThen the power of the latter ceases, Tate's pump is put into action, and the exhaustion then proceeds, imtU the mercury in the gauge descends in receivers of a thousand cubic inches to -^^ inch, and in small receivers to ^ inch, and even to -^ inch. Sec the experiments recorded at § 502. This compound air-pump is therefore adapted either to give quick results when moderate exhaustion is requisite, as at lectures, or more effectual exhaustion when that is required for special experiments or for researches. The extent of the ex- haustion is shown by the gauge g, on the plan of Xo. 577, fixed on the lower table of the pump. The apparatus is made in the most solid manner, and is mounted on a French-polished mahogany frame. The price quoted includes the gauge, but not the rod and receiver marked h and i. 521. Tate's Air-pump, of large size, arranged for easy and rapid action, worked by a winch and crank, regulated by a fly-wheel, fig. 521. Price 21?. Exhausting power of this pump, see § 502. The barrel is 1 2 inches long ; it has a bore of 2^ inches, and the stroke is 6 inches. The valves are of brass, and work in oil ; the barrel is fixed upright. The framework is of iron, and the top is of polished ma,hogany, bearing a brass pump plate of 10 inches diameter. Upon the mahogany top there is a screw to receive a syphon-gauge, similar to No. 577. There is also a descending gauge-tube of 32 inches long below the pump, and accompanied by a scale of inches. An oil-box is adapted to each end of the barrel to receive the oil which passes out with the expelled air, and these boxes from time to time must be emptied. When the pump is set up for use, the two ends of the barrel must be unscrewed and some oil must be put into each of the boxes that contain valves, about AIE-Pr3IPS. 125 4 fluid otmces in the lower bii. and 2 flnid ounces in the upper box. About 2 fluid ounces of oil should also be put into tLe pump tj tLe hole in the centre of the ground plate, which, on w.; rkir g the handle of the pump, will be distriLiiteJ throughout the interior. 521. 126 rNKl'MATlCS. An air-pump of this Jcsoriptiou, whitli effects witli oaso in five miuntes, in Lirgo vessels, a vacuum reprosentcil by | inch of moveurv in the gaug.'. civu be usefully applied in umny of tlio arts. 522. Siiiijle-barrcl Air-pnnip. tho barrel of brass, mounted on a maliOii'auy stand, form of tig. i;2:, hut irillioiil tlic basin ami rrrciivr. Piauieter of the plate, 6',' inclu's : length of the barrel. 8 inches ; bore of the bam-l, i [ iueli ; length of stroke, "j inelies. Prii-t-, irilli slopcork. 4<;.v'. 52V Siiiitll Siiiscription, with vertical barrels, sucli as Nos. 503,50+, and 520, are easy to worJc at tlie lieijiiniiii ditVu'ult as tlic exlia,nstiou approaches completion. This arises from the increasing pressnro of the atmosphere upon the ujiper faces of the pistons in the barrels when tlie spaces under the pistons are nearly t'rei- from air. With Tate's pump the contrary etl'ect is produced: at the beginning llu! pressure is considerable, bnt alter two or three strokes it gradually becomes easier and easier, tlie atm; 19, which has pistons of I^ inch diameter, requires for the first t.wo or three pulls a pretty strong hand; for, besides the atmos|ilieric pressure, there is in this case a much greater amount of friction from llio pistons to be overciauo: after two or tlireo pulls, it worlis easily enough. With a view to apply Tatty's prinei]de to large puni])s, the apparatus No. 521 has been made. In this case the force nec<'ssary to work the pistons is acquired mechanical ly, and w(! have an appa- ratus that is worked with great facility. It will be olis<>rved in the table given at § 502, that theri^ are three jnnniis. Nob. 519, 520, 521, having lo-inch plates, which can he used with receivers that hold 1000 cubic inches of air, and which exhaust these cylinders with AIE-SYEINGES. ] 27 the same degree of accuracy, while the respective cost of thesn pumps is 81., l8Z., and 21Z. The higher prices include the cost of the machinery for making the pnmps work easily and quickly. The cheapest of these pumps will do the same work as the dearest, if you give it a little more time and a little more labour. The choice of a pump must be guided by circumstances. If you require rapid exhaustion with easy work, No. 521 is the best pump; and next to it, No. 520 ; but if economy is an object, the pump No. 519 may be safely taken. Comparing together two pumps of the same price — namely, Nos. 503 and 519 — the former is easier and quicker in action ; the latter is much more effective, and without any other drawback than the two or three stiff pulls at the beginning of an exhaustion. The small Tate's pumps, Nos. 505, 517, 518, are beyond question greatly superior to all the two-barrelled pumps that are usually sold at twice their price. These small pumps can be worked without diSBculty, and, as shown in the table at § 502, they give excellent results. Care of an Aik-pump, 528. It should be made perfectly clean before being put away after having been used for a series of experiments. If it cannot be preserved in a glass case, a cover of pasteboard should be prepared to shelter it from dust. In winter it must not be taken out of a cold room and immediately submitted to use. It ought to be put for some time in a warm room. In pumping, the action should be moderate and regular. Every stroke should go home, so as to leave no residue of condensed air in the barrel ; but the pumping must never be so rapid as to leave too little time for the condensed air to escape through the valves; it must never make the barrel of the pump warm ; it must never make the mercury in the gauge jump about violently. Air, when let into a receiver by the aircock, must be let in very slowly, otherwise the action risks the spoiling of the gauge — the long barometer gauge is esj)ccially liable to destruction by a careless admission of air. A receiver should never be removed from a pump-plate without first having air let in by the aircock to sot it free, and when the receiver is removed it should never be by a direct upward jtuJh but by a sliding motion towards the edge of the pump-plate. When a pump is set aside, all the stopcocks should be left open ; for they are less subject to corrosion from acid vapours when open than they are when closed. AiK Syringes, polished Brass. Exhausting Si/ringes, u-ithoui stopcocls, fig. 531 : — 531. Barrel 6 inches long, f inch outside diameter. Price 8s. 128 PNEUMATICS. 532. Barrel 8 incies long, i^ inch diameter. Price l6s. 533. BaiTel 9 inches long, if inch diameter, mounted on a clamp. Price 35 s. 534. Barrel 12 inches long, 2 inches diameter, mounted on a flange to screw to a table. Price 42s. 535. Barrel 12 inches long, 2 J inches diameter, mounted on a flange. Price 50s. Condensing Syringes, without stopcocTzs, fig. 531 : — 541. Barrel 531- t^ 545- long. Price 8 542. long, 4 inch 6 inches diameter. 549- Barrel i^ inch Price 1 6s. Exlmusting and Condens- ing Syringes, form of fig. 545:— 545. Barrel long, |- inch Price I OS. 6d. 546. Barrel long, i^ inch Price 1 8s. Exhausting and Condens- ing Syringe, with a cross- 8 inches diameter. 6 inches diameter. 8 inches diameter. piece and clamp to fasteil it to a table, fig. 549 : — 549. Barrel 6 inches long, ^ inch diameter. Price 1 8s. 550. Barrel 8 inches long, i^ inch diameter. Price 27s. All these syringes end with female screios, and therefore require stop- cocks and connectors with male screws, to connect them with other appa- ratus. The woodcuts from No. 590 to 622 v:ill expilain this matter fully. ExTBA Fittings tor Tate's Pump. 560. Extra Screw between the pump-plate and the stopcock, represented at the upper part of 5 in fig. 5 1 7, and d in fig. 518, with a blank nut to close it when not required for use. ' Price 3s. 6d. This is not a separate piece of metal, but a prolongation of the stopcock marked k in fig. 505. It is useful for the purposes repre- sented in figs. 517 and 518. 561. Extra joint with Screw. — Those who already possess Tate's pump, as figured at Xo. 505, can have an extra joint with this screw supplied at the cost of 5s. 562. Arm to carry a Syphon Gauge, applicable to the extra screw No. 560, represented by c, fig. 517. Price 4s. EXTRA FITTINGS FOE AIE-PUMPS. 129 The syphon-gauge, when used merely to test the power of a pump, can be screwed into the plate, as shown at r, fig. 505. In that case a hole is drilled in its brass base to permit the passage of the air. But when it is desired, during the progress of an experi- ment, to know the extent of exhaustion within the receiver, the gauge can be mounted, as represented by fig. 517. The gauge d must then be without the extra hole in its brass base. Instead of this form of gauge, that represented by fig. 577 can be used in this manner. 563. Extra Pump Plate, for use in drying chemicals in vacuo, or in freezing water, over sulphuric acid, consisting of a cast-iron table, mounted on three legs, with plate-glass surface, an air-tube and stopcock, the thread of which fits a union joint, as represented by e, /, g, fig. 518, three sizes : 563. 8-inch plate, with stopcock. Price 14s. 564. lo-inch plate, with stopcock. Price l8s. 565. 12-inch plate, with stopcock. Price 25s. 566. Connecting Tube, flexible metal, 3 feet long, h, fig, 518, with a screw i, to fit the extra joint d, and a union joint g, to fit the stop- cock /, of the extra plate. Price 4s. 6d. One connecting-tube serves for any number of separate plates, Nos. 563 to 565, each of the plates having a stopcock to keep the vacuum. During the exhaustion of a receiver placed over a separate pump plate, a gauge is fixed in the centre of the fixed pump plate, as represented by fig. 518, to mark the progress of the exhaustion. 567. The connecting-tube, with the stopcock /, g, Ji, i, fig. 518, complete. Price 6s. 568. Flat glass receivers for the extra pump plates, of strong German and Bohemian glass, welded and ground on the edges, see article on Eeceivers, § 796, and fig. 800. 569. Pans for containing sulphuric acid, represented at fig. 518, are described at § 705. Syphon Gauges, for showing the extent of exhaustion effected by air-pumps within their receivers. These are of three kinds : — 575. Common three-climbed syphon gauge, mounted on a brass foot, with male screw, fig. 575. Price 3s. 6d. This gauge may be had either with or without an air-hole drilled in the brass foot ; see Note to No. 562. It is used as shown by r, fig. 505, and d, fig. 517. 576. Syphon gauge, with scale, form of fig. 576, mounted on a flat stand, and requiring to be placed under a receiver 5 75- 5 76. 577. for trial. Price 5s. 130 PNEUMATICS. 577- Syphon gauge, witli glass scale, form of fig. 577, the gauge enclosed in a glass tube. Prirr, with stopcock, I0». M.. 578. Ditto, without stopcock. I'rirc 78. Of these three syphon gauges, the one that is least trustworthy is the first. No. 575, in consequence of the difficulty of filling it with mercury quite free from air. This variety also is not gi-adiiiitud. The difference in the level of the two columns of mercury indicates the extent of the exhaustion. The other two are graduated to show twentieths of an inch. No. 577 is represented in use by I, fig. 518, and g, fig. 520. Purchasers of the pumps, Nos. 505, 517, 518, with which the gauge No. 575 is delivered, may have No. 577 instead, on payment of the difference in price. The precautions to be taken to secure accurate results in the use of syphon gauges have been detailed at § 502. Stopcocks, Connectoks, and Fittings foe occasional use. The following stopcocks and connectors are all London-made, of the best quality, and of polished brass : — Stopcocks and connectors of polished iron cost about onehalf more than those of polished brass. Stopcocks. 590. Stopcock, with two male screws, fig. 590. Price 3*. 591. Stopcock, with one male and one female screw, fig. 591. Price 3«. 5';0. 552. Stopcock, with a male screw at one end, and at the other end a union joint and a long brass tube for attaching a flexible tube, fig. 592. Pri/c 58. 594. Stopcock, with a female screw at one end, and at the other end a union joint and a long hracs tube for attaching a flexible tube, similar to fig. 592, but having a female screw instead of a male screw. Price 58. 502- EXTRA FITTIKGS FOE AIR-PUMPS. 131 595. Stopcock, with a tube at one end for connecting a caout- cliouc tube, and at the other a male screw, fig. 595. Price 38. 596. A similar stopcock and tube, but having a female screw at one end. Price 3«. 595- 597- 597. Stopcock, having at each end a tube for connecting a caout- chouc tube, fig. 597. Price 3*. Connectors. 600. Connector, with two female screws, fig. 600. Price is. 601. Connector, with two male screws, fig. 601. Price is. 602. Connector, with one male and one female screw, fig. 602. Price IS. 603. Blank nut, with one male screw, fig. 603. Price is. 604. Blank nut, with one female screw, fig. 604. Price is. These blank nuts are used to stop openings that are not required ; see No. 560. p n-T 605. 606. Three-way and four-way Connectors ; four patterns. Pr each 38. .• — 605. Connector, two female screws, one male screw, fig. 605. K 2 132 PNEUMATICS. 606. Connector, three female screws, fig. 606. 607. Connector, three female screws and one male screw, fig. 607. 608. Connector, two female screws and two male screws, fig. 608. 609. Brass Caps for bell-jar receivers, and for L;lobos for gastw, with female screw ; dianiotiu's to suit glass nooks of f , i, !;[ inch, fig. 609. Frice each is. 610. Similar brass caps, il, 2, and 2|^ inches in diameter, to suit large receivers. Pri.ci'. each 2s. 611. WksJu'is. — ^When stopcocks, connectors, &o., are screwed to- gether, there should be a piece of oiled leather, a washer, of the form of fig. 611, placed between them, to ensure an air-tight joint. These washers must always be kept clean and softened with oil, and the screws should be frequently- cleaned and slightly oiled. Price per dozen gd. 6 1 6. Bladder piece, or socket to tie in the neck of a bladder or a gas bag, with female screw for receiving a stopcock, fig. 616. Price gd. Goy. 611. 619. 617. Connector for attaching a flexible caoutchouc tube to brass fittings, with female screw, fig. 617. Price gd. 618. Ditto, with male screw, fig. 618. Price gd, 619. Connector to join a ;J-inch to a i-iuoh caoutohouo tube, without screws, fig. 619. Price 6d. 620. Union joint for connecting two flexible tubes togetlier, fig. 620. Price 2S. 621. Block to be screwed to a table, with female screw to receive the ends of syringes, cross-pieces, or other articles that need to be fixed in an upright position ; two kinds, fig, 621, flat. Price is. 622. Ditto, raised. Price is. EXTRA FITTINGS FOE AIE-PUMPS. 133 [1 -A n 1 \ r* 1 V 620. 621. 622. 'S b24. 626. 624. Ground Brass Plate and Hook for suspending objects in exhausted receivers that have welted and ground necks, such as Nos. 684, 725, 4 inches diameter. Price 5s. 625. Ground Brass Plate, with sliding Rod, passing through a stuffing-box, to affijrd the means of moving apparatus suspended in an exhausted receiver; see Nos. 696, 666. 4-inch plate. Price 12s. The brass plate has a small hook on the under side, which is not shown in fig. 625. The hook at the bottom can be unscrewed and removed, for certain operations. 626. Clip and Weight for hold- ing plants under water in vacuo, to show the quantity of air dis- engaged, fi-g. 626. Price 2s. 6d. The clip in action is shown by fig. 676. 626 A. More powerful clip for large objects, with box contain- ing lead shot. Price "js. 6d. 627. Single Transfer Plate, or Fountain Plate; a ground brass plate, with stopcock, water pipe, and fountain jet, for producing a fountain in vacuo, as described at § 462. Fig. 627 shows the appa- ratus mounted on a mahogany stand ; the small figure is the water-pipe. 627. A. 4-ineh plate, jprice 15s. B. 5-inch plate, jjn'c'e 1 8s. 628. jExperiment loith the single Transfer Plate. — The transfer plate is used when it is necessary to produce a vacuum in a vessel suddenly. The arrangement is represented by fig. 628. The o 625, 627. 134 PNEL'MATICS. small upper receiver is the vessel in which the vacuum is to be produced suddenly. Under it is a larger receiver, and the transferer connects them. The subject to be operated upon is placed in the upper receiver, the lower receiver is then exhausted ; after which, on turning the stopcock of the transferer, the air rushes suddenly from the upper into the lower receiver, leaving a partial vacuum. The degree of rarefaction will be in proportion to the difference in the capacities of the two receivers. 62a. Experiment witli Caoutchouc Balls. — Take two small caoutchouc balls, each containing a little air. Dip the mouths iato chloroform, which closes them air-tight without tying them. Put one ball into each receiver; leave the transfer stopcock open; exhaust partially. As the air passes out, both caoutchouc balls swell. When they are about l^ inch in diameter, shut off the transfer cock and continue to exhaust ; the ball in the lower receiver wUl then swell to 4 or 5 inches in diameter. Cease to pump ; open the transfer cock, upon which the upper ball will suddenly become larger and the lower ball smaller, because the air rushes from the upper receiver to act in the lower receiver. Price of the reeeirer, mounted with screw cap, 5s. 630. Boulle Transferer, fig. 630, consisting of two 4-inch ground EXTRA FITTrSGS FOE AIE-PC3IPS. 135 brass plates, each with a stopcock helow, both connected with a horizontal tube, which is attached in the centre to a third stop- cock, capable of being screwed to a stand, as here figured, or to the table of the air-pump. Hence receivers, such as d, e, placed upon the transfer plates, can be exhausted separately, or be put into communication with one another. Price of the set, imlhout retewers, j^zs. Unscrew the apparatus from the wooden foot, and screw the end of the stopcock c into the plate of the air-pump. Open the stopcocks a and c, and dose the stopcock h. Place a receiver d upon the table of a, exhaust the air from it, and turn off the stopcocks a and c. The apparatus can then be removed from the pump, and the wooden foot be screwed to it. Then put a receiver e upon the plate over the stopcock h. The apparatos will now appear as represented in fig. 630, but the receiver d will be fixed, and the receiver e be loose. Xest, open both a and h. Half the air contained in the receiver e will then pass into the receiver d, and both receivers will be fixed upon their plates by the atmospheric pressure, though each will be kept down by only one-haK of the pressure that acted on the first receiver when exhausted of its air. This experiment shows very clearly the expansibility of air. 631. Aurora Borealig Apparatus, consisting of a ground brass plate, 4 inches diameter, with three spikes ; the plate adapted in width to the top of the conical glass receiver of the guinea and feather apparatus ; and of a second brass plate, with three spikes, to screw into the plate of the air-pump. Price of the pair io«. 6d. TVhen this apparatus is properly arranged, screwed up tight, and exhausted, the aurora borealis appearance is produced when a current of electricity is sent through the vacuum. 634. Brass clamp, for fastening an air-pump to a table, ifcc, 2^ inch, fig. 634. Price 3«. 6rf. 635. Iron clamp, fig. 634, 3 J inch. Price is. 6d. 636. Iron clamp, 4^ inch, represented by fig. 636, and by c, fig. 518. Price 4.?. 637. Brass key, for screw- ing up the joints of air- pump apparatus, connectors g,^ to stopcocks, iVc. A- Single, price is. 6d. B. Double, price 2«. 6d. TallotB-holder, which consists of a mahogany tube, containing a piston moved by a screw, fig. 63S. 638. Small tellow-holder for general use, bore ^ inch. Price is. 136 rXEUMATICS. 639. Large tallow-lioMer, for use with the air-pump, bore J inch. Price IS. 6d. Tallow, or a mixtui-e of tallow and was ia summer, or tallow and lard in winter, is convenient for greas- ing the edge of a glass vessel pre- ____ viously to decanting a liquid, in order g.g to prevent the running of the liquid over the edge of the vessel so as to descend outside. TaUow is also required to grease the edge of air- pump receivers, to make them fit the ground-plate air-tight. To fill the taUow-holder, the piston is screwed back to the top of the tube, and melted tallow is pouied in till the tube is full. After cooling, the tallow is projected as required by turning the screw. 640. Porcelain poiu-er, in which to mix and melt tallow, wax, &c., to fill the tallow-holder. Price is. In collecting tallow from the air-pump plate and the rims of receivers, which can be done by a steel spatula No. 640 a, and transferred to the pourer No. 640, care must be taken to col- ^ ■ lect no dirt or grit, which would subsequently act mischievously. After melting such collected tallow, it ought to be examined for grit by the finger I - — TTi \ before it is applied to use. Fat ^ l-Ji — ) set aside for future use should be g ^ preserved in a pot provided with a cover to keep it free from dust. 641. Groorecl Plate. — In the middle of every air-pump plate is a hole through which the air is drawn in exhaustion. Many objects with flat bottoms are placed upon this plate, and may stop up the hole and prevent exhaustion, unless that stoppage is guarded against. Sometimes a hole is drilled in the flat foot of the object subjected to experiment, or in the tube that rises from it, to retain a thoroughfare for the air undergoing exhaustion. A very useful foot for general purposes is a flat plate of metal, with parallel faces, and on the under face several grooves leading to the central hole in the pump plate. Price of ^-inchor .^-inch grooved plates, 4A EXPEEIMENTS ON THE PEOPEETIES OF AIE. IX FOUR GROUPS. Gkotjp a.— The weight axd eesistakce or Aie, § 650 to § 670. 650. Estimation of the Specific Gravities of Gases. — The apparatus employed for this purpose is represented by figs. 650 and 651. EXPEEIJIENTS ON THE WEIGHT OF AIK. 137 I 650. Tall glass gas receiver, about 1 2 inches high by 6 or 7 inches wide, flanged and ground at the bottom, graduated into (about) 350 cubic inches, mounted with a stout glass globe, 5 inches dia- meter, two stopcocks with double male screws, and a double female connector. Price of the set, fig. 650, 20s. 651. Flask to show that air has weight, namely, a globe of very light glass, mounted with brass cap, with a small stopcock, an extra screw, a, to adapt it to the air- pump, and a hook for the balance. Size of the globe, about 4^^ inches diameter ; capacity, about 50 cubic inches ; for use in weighing air and gases. Price 7s. 6d. In fig. 651, the screw marked a serves either to attach the globe to the air-pump or to the jar 650 a. I copy the following details from Griffin's ' Chemical Eeoreations,' page 277. The ap])aratus for esti- mating the specific gravities of gases consists of the following parts : — " I. A cylindrical jar, a, in which the gas can be collected. It may be graduated into cubic inches and decimal parts, or into cubic centimetres. " 2. A very light glass globe, 6, fitted with a small and light brass cap, d, and a small stopcock e. In the figure, the caps d and c, and the stopcocks e and g, are made of the same size. The figure, however, represents an aj^paratus suitable for other experiments in chemistry. But for the determination of the specific gravity of gases, not only must the globe 6 be made as light as possible, but the brass fittings d and e must also be made small, and very light. " 3. The brass fittings c to g complete this apparatus; c is a cap cemented to the jar a. It has a female screw ; d, a cap cemented to the globe b, has also a female screw ; / is a connector with two female screws ; and the two stopcocks e and / have each two male screws. These pieces are shown by figs. 590, 600, and 609, at about half the full size ; excepting that the small cap d should not be larger than fig. 609, and the stopcock e not larger than fig. 590. " The operation of taking the specific gravity of a gas is performed as follows : — " The globe, h, having been made perfectly clean and dry, is filled with perfectly dry atmospheric air, and with the cap, d, and stop- 651. 138 PNEUMATICS. cock, e, is weighed. It is tlien screwed to an air-pump, or air- syringe, and exhausted of the atmospheric air as completely as possible. The stopcock, e, is closed, and the globe is weighed again. The difference between the first weighing and the second shows the weight of the atmospheric air which has been withdrawn by the air-pump. The exhausted globe, h, is next connected to the receiver, a, by the intermediate brass-work shown in the figm-e. The two stopcocks, e, g, being then opened, gas passes from the receiver, a, into the globe, 6, and fills it. The stopcocks are then closed, the globe, with its stopcock, e, is unscrewed from /, and once more weighed. The difference between the result of this weighing and of the second weighing shows the weight of the gas submitted to trial. " If the jar a, from which the globe is filled with gas, stands over water, the gas will be saturated with aqueous vapour, the quantity of which must be allowed for by calculation, or the gas must be passed, for weighing, not directly from the jar a, into the globe h, but through an intermediate apparatus for drying it. " If the globe 6, employed for these experiments, be sufficiently large to contain, at 6o° Fahr., and 30 inches bar., ^6"J cubic inches of gas, the bulk will represent one grain of hydrogen gas, and that globe will contain the quantities of the elementary gases which are represented by the atomic weights of these gases. That is to say— " I volume of hydrogen gas being = i grain I volume of oxygen gas will be = 1 6 grains I volume of nitrogen gas „ = '4 ,, I volume of chlorine gas „ = 355 „ And the quantity of a compound gas will be represented by its atomic weight divided by its atomic measui'e. Thus : — " I volume of carbonic acid gas, CO^, will be = 44-^-2 =22 grains. I volume of carbonic oxide gas, CO, will be = 28-^2 = 14 grains. The same volume of atmospheric air will be I4"47 grains." The light glass globe usually sold with the apparatus No. 651, commonly contains about 50 cubic inches, or 1 5 grains of air, so that the large balance No. 122 can be used to weight the globe No. 651, and give a result approximately true. 652. Experimental proof that Air has weight. — The apparatus and experiment described at §§ 650, 651, afford the means of proving this fact in the most precise manner. The following experiment also serves to prove it, in an easy and satisfactory manner, when no air-pump is at command. Connect a narrow glass tube, by means of a sound cork, to a globular flask, draw out the external end of the tube to a very fine point, which must be left open. The joints EXPEEIMENTS ON THE WEIGHT OF AIE. 139 must be completely air-tight, and the cork may be varnished to ensure this condition. The apparatus being prepared, the flask is to be gradually heated over a spirit lamp or charcoal fire, and is finally to be made very hot, to drive out as much as possible of the included air. The point of the tube is then to be suddenly brought into the flame of a spirit lamp or a blowpipe jet, and closed by fusion. The best way to do this is to use a second spirit lamp and blowpipe, while the apparatus is being heated over a separate lamp. Allow the apparatus to cool, and coun- terpoise it in the pan of a balance. Then break off the point of the tube, upon which air will rush into the flask, the apparatus will become heavier and the counterpoise will be overbalanced. 653. Comparative Specific Oravities of Hydrogen Gas and Car- honic Acid Oas. — These have been stated at No. 651, and the facts can be proved by collecting the gases in the cylinder No. 650, transferring them to the globe No. 651, and weighing them. But the following method is quicker and therefore more suitable for a class expei'imenfc. It is a rough sort of operation, but it demonstrates the prime facts that hydrogen gas is much lighter than air, and carbonic acid gas much heavier. Fig. 65 3. is a cylinder of pasteboard, measuring about 7 inches in length and 5 inches in diameter; it is open at one end and provided with strings, by which it can be suspended by either end to the hooked pan of the hydrostatic balance No. 122. Experiment A. — Suspend the cylinder mouth down- wards and counterbalance it ; then bring under it a jar or bottle filled with hydrogen gas. Eemove the stopper 5,, from the gas bottle and pour the gas into the paper cylinder. In consequence of the lightness of the hydrogen gas, it will rise into the cylinder and the atmospheric air will sink down. The counterpoise will be thereby destroyed, and the cylinder con- taining the hydrogen gas will rise. Experiment B. — Suspend the paper cylinder to the balance moutli upwards and counterbalance it ; then pour into it from a jar a quantity of carbonic acid gas. This will cause the paper cylinder to descend, because carbonic acid gas is heavier than atmospheric air in the proportion of 3 to 2. The two jars of gases should be provided beforehand. If time permits, the gases may be introduced into the paper cylinder by the tubes coming directly from the generating gas bottles. But this method is slow and uncertain. Price of the paper cylinder, mounted with strings, 6d. 654. Balloons, for rising in the air when inflated by hydrogen 140 PNEUMATICS. gas, or coal gas. Splierical sliape, commonly coloured in gores ; but the 9, loj^, and 12 inch sizes can be supplied coloui-ed plum- pudding pattern. 9 inch, price is. ^d. lO|V inch, jyiice is. gd. 12 inch, pciVe 2s. 6d. 15 inch, ^ivVe 3«. 18 inch, ]}rice 5s. 6 inch, for hydrogen ga,s,price is. Balloon, in shape of Mr. Punch, 6 feet high, 9 feet in circum- ference. Price 63s. Balloon, in the shape of an elephant, 3 feet long, 2^ feet high, ascends in proper position, and can be led by a guiding string into any part of a room. Price 35 s. Balloon, fish shape, 15 inches long. Price 4s. These balloons are made of gold-beater's sldn. When not in use they should be kept in a clean tin case, with a little camphor, to preserve them from the attacks of insects. They ought never to be wetted. When they are expanded with air from the mouth, the lips ought not to touch the mouth of the balloon. They will all ascend with dry coal gas. In filling a balloon the gas should be passed through a glass tube containing pieces of chloride of calcium, to free the gas from water. The large sizes of balloons, when in good condition, may be kept suspended two or three days, fastened by a string to the table ; but the hydrogen gas is gradually ex- claanged for atmospheric air by osmotic action, and the balloon finally descends. The hydrogen gas with which a balloon is to be filled must all be prepared before the filling is attempted, and should be contained in a gasholder, or in large jars provided with stopcocks. 655. OTlie Baroscope, or Balance, with u-cigM and corh, to show how the bulk of objects affects their weights when they are weighed in atmospheric air, and in vacuo. Price icithout the receiver, 6s. The weight and cork attached to this balance are in equilibrio in free air. Place them under a receiver and exhaust the air. The cork will then appear to be heavier than the weight ; for as its bulk is greater than that of the metal of which the weight is made, it must be more sustained by the air. Admit air to the receiver, and the original equilibrium is restored. For, as bodies which are immersed in liquids are known to lose a part of their weight, equal to the weight of a quantity of the EXPEEI5IEXTS OX THE EESISTAXCE OF AIE. 141 liquid of the same bulk as the immersed body, so bodies of different specific gravities, wbicli are in equilibrio in air, will not be so in vacuo ; for then they will gain that weight which they lost in air, and the body of the greatest bulk will gain the most. As cork changes in weight when exposed to moist air, it is neces- sary previous to every experiment to justify the counterpoise, which is made to open for that purpose. A receiver of the form of fig. 825 is generally used for this ex- periment, because the receiver of fig. 655 requires a very wide plate to rest on. 656. Water Hammer, or PMlosopJiical Summer, for showing the force and solidity with which water falls in a vacuum. This is a glass tube, partly filled with water, and quite freed from air. When this is held vertically in the hand, and smartly jerked up and down, the water falls in a block, vrith a noise resembling that produced by the stroke of a hammer. The most effective motion is a steady lift upwards, succeeded by a powerful and sudden jerk dovmwards. If the jerk is too strong, the water sometimes drives out the bottom of the tube. Several sizes are supplied : 7 inch, price is. 6d.; 9 inch, price 2s. ; 12 inch, price 2s. 6d. 656 A. — Water Hammer, V-formed, about 16 inches long, closed at one end and mounted at the other end with a brass stopcock, suitable for ex- haustion by the air-pump, fig. 656 a. Price, with stopcocTc, 8s. Management of the Y-formed Water Hammer. — ■ Fig. 656 A represents the apparatus in four positions. g,6_ It consists of a V-shaped tube, having a brass collar fixed on its open end and joined to a stopcock. There must be a leather washer between the two brass pieces, and that washer must be in good condition, well oiled, soft and flexible. One limb of the tube is three-fourths filled with water. a. Hold the apparatus in this position, screw the stopcock into the plate of the air-pump, and exhaust thoroughly. The air will be seen to rush out of the water for a long time. When the dis- charge of air appears to cease turn off the stopcock, unscrew the apparatus from the pump, and transfer the water to the branch over the stopcock. b. Then hold it in this position. If there is any leakage about the brass fittings, either in the plug of the stopcock, or in the cement, or about the washer, air will rush up in bubbles through the water. 142 PNEUMATICS. Correction of the leakage must be made and the air be again esbausted, until the water remains quiet in the position marked h. c. Transfer the water to the closed limb and hold the apparatus in position c, applying your hand to the stopcock. Give the appa- ratus a jerk up and down, as directed in § 656, when, if the ex- haustion is good, the water will fall like a solid block. If the exhaustion is not good, then upon tapping the table with the bottom of the tube that contains the water a slight jingling noise wiU be heard, and a multitude of minute bubbles of air will rise up through the water. d. Put the tube into the position marked d. If the exhaustion is good, the water will remain in the closed branch, as represented ; but this will require very complete exhaustion. This experiment affords an excellent illustration of the difficulty of completely abstracting air from water. 656 A. 656 B. Forh-shaped Water Hammer, fig. 6563. Price zs. 6d. 6^'j. Guinea and Feather Experiment, to show that heavy and light articles fall with equal rapidity when air is removed. 658. Brass-worJc for this Experiment, consisting of a 4- inch ground brass plate, with stuffing-box, sliding rod, and two falling stages ; the plate is also furnished with a hook, on which to hang a bell, the Magdeburg hemi- spheres, &c. See fig. 65o. Price 1 8s, 659. Brass-worJc for three falls. — Similar brasswork arranged for three falls, but not provided with the hook. Price 2 IS. 660. Open Conical Glass Receivers for the Guinea and Feather Experiment, flanged at both ends and well ground. See sizes and prices at Nos. 888, 889, 890. 664. The Guinea and Feather Apparatus is intended to illustrate the fact that the air diminishes the velocity of falling bodies, and this diminution is greater or less according to the 656 B. EXPEEIMENTS ON THE RESISTANCE OP AIE. 143 density of tlie falling body ; but if the air is removed, the velocity of all falling bodies is equal, whatever difference may exist in their comparative densities. To show this with effect, place a tall open receiver, No. 660, on the plate of an air-pump, and on the top of the receiver put the guinea and feather apparatus, having previously placed on the flap of the apparatus a guinea or other coin, and a feather; exhaust the receiver, then turn the milled-head until the flap falls, and the guinea and the feather will strike the plate of the air-pump at the same time. But if the experiment is repeated without exhausting the re- ceiver, the resistance of the air will cause the feather to occupy a much longer time in descending than the guinea. The eye of the observer should be directed towards the bottom of the re- ceiver, to ascertain accurately the co- incidence of descent in the two bodies. Guineas are never used in this ap- paratus, and feathers not always. Common coins, farthings, or even disks of lead, answer the purpose, and very often round pieces of thin paper are used instead of feathers. The latter are liable to stick to the sides of the receiver, and to be thus arrested in their fall. 665. The Ghxinea and Feather TSx- perimeni can be performed with a glass (,(,q_ tube; size about 4 to 5 feet long and about I J inches wide, mounted with brass caps at both ends, and with one brass stopcock, having two male screws. Fig. 665. Price 15s. 666. Windmill, with two sets of equal-sized vanes, one set striking the air edgeways, the other set striking it with their broadsides. In the open air the latter soon become still, while the former continite to revolve. In vacuo they both travel the same length of time. Fig. 666. Price 36s. To set the mills in motion in the open air, pull up the rod in the middle, which puts both sets of vanes in action. The broadside G 665. 144 PNEUMATICS. vanes ouglit to stop some time sooner than the set fixed to rim edgeways. If they do not, they are out of order ; most probably some object is adhering to one of the sails, making it heavier than the others, and therefore irregular in action. In that case, if you turn the mill slowly you will find the stoppage to occur when- ever one particular sail, after a little oscillation, rests lowest. That points out where the correction is required. If the mills work regularly in the open air, put them under a receiver of tlie form of fig. 696, mounted with the sliding rod, fig. 625, so arranged that the lower end of the sliding rod is put above the knob of the windmill, when that knob is pulled up as far as it will go, which it should be before being placed under the receiver. The mills should be placed on a suitable grooved plate. See No. 641. When the receiver has been sufficiently ex- hausted, the rod No. 625 should be suddenly pressed down and the mill be set in action. If in good order, the two sets will remain in motion during the same time. Group B. — On the expansion of Air, § 671 to § 710. 671. Bulb Gauge and Olass Jar, for testing the exhausting power of an Air-pump; the bulb about an inch in diameter and the stem about 4 inches long, in a jar of about 5 ounces capacity. Price of the pair 2s. Experiment A. — Place the apparatus (after putting a little water into the jar) upon the plate of the air-pump, cover it with a receiver, and exhaust the air. The pressure being re- moved from the surface of the water in the jar, the air in the bulb will expand and escape in large bubbles through the water. After suf&- cient exhaustion, admit the air into the re- ceiver, and its pressure on the water in the jar will force it up into the bulb, leaving therein only a small bubble of air. The bulk of this bubble, compared with the bulk of the tube and bulb, indicates the degree of the exhaustion. KX.PEEIMENTS ON THE EXPANSION OF AIK. 145 Experiment B. — Fill the biilb-tube almost full of water, leaving only a very small bubble of air. Pill the jar with water, invert the tube and plunge it into the jar ; then remove most of the water from the jar by means of a syphon or pipette, leaving enough to cover the mouth of the bulb-tube. Place the jar under a receiver and exhaust it. The small bubble of air will then expand and force all the water out of the bulb-tube. On readmitting air to the receiver, the water will be driven back from the jar into the bulb-tube. 672. Experiment 0. — Similar experiments to A and B can be made with vessels prepared for other purposes, but combined for this experiment, as represented in fig. 672. a is the plate of the air-pump ; h a guinea and feather glass, serviceable also as a foun- tain glass ; c a ground glass plate to close it; d a, tall jar on foot, resting in this case on a small porcelain support (see No. 641) ; e a bulb-tube with long stem. For the experiments just described the figure shows too much water ; but that is subject to correction. 672. 673. Pair of narrow Bottles, connected by a bent tube fastened by a cork to the mouth of one of them. Price is. 6d. Fig. 673 a is the plate of the air-pump, 6 a receiver. The bottle c is supposed to be nearly full of water, but retains a small quantity of air. The cork must fit tight. When the air is exhausted from the receiver, the expansion of the small quantity of it left in c drives the water through the tube e into the bottle d. When air is lie PNEUMATICS. readmitted into the receiver h, the water is driven back from tlie bottle d into the bottle c. 674. Lunijs Glass, fig. 674. Price, witlmid the receiver, 5s. The apparatus with this fanciful name is constructed as follows : — A globular glass on foot is sm-mounted by a brass cover. A bladder is tied round a small pipe that descends from the cover into the globe, but the air within and without the bladder is not in com- munication. When this apparatus is placed under a receiver, and the air is partly withdrawn from the bladder, the spring of the air surrounding the bladder in the globe, which cannot escape, compresses the bladder ; when air is let into the receiver, the bladder expa7ids. That is the whole action. These motions are slow when held to be ana- logous to those of the lungs. The best way to proceed is as fol- lows : — Partially open the aircock that supj)lies the receiver with air, and leave it in that state, and then exhaust slowly. Every stroke of the exhausting piston partially condenses the bladder, but the aircock meanwhile restores the expanding pressure. A little experience suffices to enable the operator to work the appa- ratus with some regularity. EXTEICATION OF AlB FEOM VARIOUS BODIES. 675. Jdr from Spring-water. — Place a vessel of fresh spring- water under the receiver of the air-pump and exhaust the air. As soon as the pressure of the atmosphere is removed, the gases that are dissolved in the water expand by their elasticity, form lajrge bubbles, and escape from the water, producing in the latter a state of effervescence. It must be borne in mind that in all experiments with water the vapour of water passes into the works of the air-pump, and makes it impossible to procure a good vacuum until the water has been again exhausted from the pump. Hence, at a lecture, it is prudent to avoid experiments with water until all other experiments that demand a good vacuum have been performed. 676. Air from the pores of Plants. — The plant selected may be a sprig of fresh mint, but many other plants serve equally well, either fresh or dried. Fasten the stalk of the plant in the clip No. 626, and lower the clip and weight by a wire or cord to the bottom of a tall jar containing fresh and clean spring- water. Place the jar on the air-pump plate and cover it with a tall receiver. The arrange- ment is shown in fig. 676. A shorter and wider apparatus may also EXPERIMENTS ON THE EXPANSION OF AIE. 147 be iisecl. Exhaust the air from the receiver. The whole surface of the mint will be covered with minute bubbles of air, which give it a beautiful appearance. These are disengaged in part from the spring-water, and in part from the plant. Price of tall receiver, 6 inches diameter and 20 inches high, 25s. Price of tall jar, 4 inches diameter and 16 inches high, Bohemian glass, 8«. 677. Air extricated fi-om Cork. — Fix some lead to a piece of cork, enough merely to submerge it in water. Place the jar containing the cork and water under a receiver, and exhaust by the air- pump. The air contained in the pores of the cork will then expand, so as to swell it and make the mass lighter than water. It will consequently rise to the top of the water and swim, cork and lead together, and the surface will be covered with a beautiful mass of globules of air, resem- bling the pearly drops of dew on the blades of grass. When the air is admitted into the re- ceiver, the bubbles of air disappear and the cork sinks. 678. Air from Beer or Ale. — Place a beaker. No. 678, partly filled with beer or ale, under a receiver, and exhaust. The liquor will expand, and a mass of froth rise up in the beaker to form a large white head. This production of froth is due to the tenacity of the fluid, which 676. prevents the bubbles of air from escaping as soon as they rise. When the air is readmitted to the receiver, the bubbles contract and subside. On tasting the beer, after this operation, you will find it to be flat and spiritless. 679. Air from an Egg. — If you put an egg into a beaker of water, place it under a receiver, and work the pump to produce a vacuum, you will see the air rise in a very beautiful manner in small jets through the water from the pores of the egg- shell. 680. Air from Colce. — Put two pieces of coke into water in a beaker; both will swim. Tie one of the pieces to the weight and clip No. 626, and sink it to the bottom of some water in a beaker. Put the glass under the air-pump receiver and exhaust. A great quantity of bubbles of air will come from L 2 678. 148 PNEUMATICS. the submerged piece of coke. When the discharge of air slackens, take the coke from the clip and add it to the other piece of coke still swimming in the original beaker, in the water of which it will instantly sink to the bottom, showing that water, when present in coke instead of air, greatly adds to its weight and specific gravity. 68 1. Elasticity of the Air-lubhle in an Egg. — The air-bubble in an egg is situated at the great end between the skin and the shell. On making a small hole in the little end of the egg and inverting it in a glass, and placing the glass under an air-pump receiver and exhausting it, the bubble of air will expand and force out the con- tents of the egg through the small hole in the lower end. 682. Fruit and Taper Stand, fig. 682. Price 3s. Shrivelled apples, prunes, or raisins, after being soaked a little in warm water, when placed under the receiver of an air- pump, on this stand, will become plump on the receiver being exhausted, from the elastic force of the air within their cells; but on readmitting the air the fruit loses its apparent freshness and re-assumes the same appear- ance as before the experiment. This stand also serves to support a taper under the air-pump receiver, to show that it will not burn when air 682. is removed. 683. Apple-cutter, fig. 683. Price 3s. This is a glass jar mounted with a brass collar provided with a circular cutting edge. Upon this circular knife an apple is fixed by gentle pressure, care being taken to see that the apple leaves no part of the cutting edge free. The jar is then placed on the plate of the pump, and the process of exhaustion is commenced. As this proceeds, the apple descends under the continued action of the circular knife and the pressure of the atmosphere, and a cylindrical mass falls into the jar. 684. Bladder experiments, to show the expansive power or elasticity of the air. Take a clean and soft bladder, containing a little air, and tie the neck close ; then suspend the bladder by a hook, similar to No. 624, under a receiver, similar to No. 684 ; place the receiver on the plate of the air-pump, and exhaust the air. Thereupon the bladder will be expanded and blown up by the spring of the small quantity of air left in it. See fig. 684. On re-admitting air to the receiver, the bladder will shrink into its former shape. 685. Price of bullock's bladders, prepared for use, 6d. 686. Sheep's bladders, prepared for use, 2d, 688. Bladders should be occasionally washed with a mixture of EXPEEIMENTS ON THE EXPANSION OP AIR. 149 water and glycerine, to prevent their cracking into holes. After iising a bladder it should, ■while still moist, he fully blown up and then sponged ..^ ^^ __--, ^_ with a mixture of glycerine '==^: J^-—. and water. Before sub- mission to an experiment at a lecture, the soundness of bladders should be ascer- tained by trial ; for they are constantly subject to per- foration by insects. Solution of carbolic acid in water deprives bladders of a bad smell when they are put aside in a wet state. 689. Elastic Bolls. — Four caoutchonc balls containing a little air, and sealed air-tight by dipping their mouths into chloroform, for showing the elasticity of air by expansion in an exhausted receiver. Price of the set is. A single caoutchouc ball, firmly closed and containing a little air, can be expanded under a receiver until it becomes very large. Fig. 689 represents a curious experiment. Two sealed caoutchouc balls, containing a little air, are put under a small bell-shaped receiver, which is exhausted. As the action proceeds the balls swell and soon become too large to lie quietly together on the plate, whereupon a strife takes place between them and they both fly to the upper wider part of the receiver and remain there, side by side, resting against the walls of the jar. Consult § 628 for another ex^ieriment with caoutchouc balls. 690. Bladder frame and lead loeights, to show the elasticity of air when relieved from pressure, figs. 690 and 691. 690. Small size, diameter of lead weights, 2^ inches. Price 8s. 691. Large size, diameter of lead weights, 3^ inches. Price l6s. The bladder used for this experiment f;„o_ must be of small size, sound, contain a little air, and be well tied. 691. It should also 150 PNEUMATICS. have been rendered flexible by soaking in water, mixed witb a little glycerine. Tbis apparatus illustrates the expansive force of tbe air. The small portion of air vrithin tbe bladder expands on removing tbe external pressure, by means of an air-pump and receiver. If the ex- haustion is continued, the expanded air will exert such force as to raise the heavy weights placed upon the bladder. On admitting the air the bladder shrinks to its original bulk, and the weights descend. 692. Glass hrealdng squares, to show the expansive power of the air. Price each is. 6d. These are thin square glass bottles, of about half a pint capacity. To use them take one of the bottles, cork it, and cover the cork with sealing-wax, so as to prevent the escape of the enclosed air ; then set it under the receiver of an air-pump and exhaust the air from the receiver. The air within the bottle will then expand with such force as to burst the bottle. The wire cage, § 693, is required for this experiment. 693. Wire Cage, to cover the breaking squares and collect the fragments of glass when they burst. Price 3s. It is prudent also to cover the plate of the pump with a thick piece of paper, or a disk of felt, to prevent scratches from the fragments of the exploded glass. 694. Paper Smohe-jacles, two patterns, a wheel and a serpent. Price of the pair is. They serve to show the rising currents pro- duced when air is warmed and expanded. They may be suspended over a lighted lamp by a thread, or on a needle point, placed on the side of a magnet. The vanes of the wheel must be bent when the apparatus is to be used. Bells to be bung in Exhausted Eeceivees. 695. Bell suspended in a brass circle, mounted on a wooden foot, to be rung by being shaken. Price 5s. 6d. 696. Bell mounted on a brass foot, to be rung by a blow on the upper table, mounted on a felt disk. Price, without receiver, 5s. 6d. When a bell is struck in the open air it rings, because the air about it is put into a state of vibration. When a bell is struck in an exhausted receiver it ought not to ring, because no air is present to be put into vibration. Many forms of apparatus have been contrived for this experiment. We shall limit our description to the two represented by figs. 695 and 696. 695 Unscrew the brass-work from the mahogany foot and screw EXPEEIMEXTS ON THE EXPANSION OF AIE. 151 it in the centre of the air-pump plate. Cover it with a receiver, lift up the pumjj and shalie it. This last direction brings a difficulty. If you use Tate's pumj), or any of those from No. 503 to No. 521, you cannot shake it. It is only with small pumps such as Nos. 522, 523, that you can put this process into operation. The shaking makes known another difficulty. If you have a small receiver over the bell, the shaking produces scarcely any sound, although the receiver is full of air. The reason is, that in a small receiver there is not space enough for sufficient air to vibrate. The difference in the sound of the bell when shaken in the open air and when shaken in a small receiver is very great. However, you pro- ceed to exhaust the z-eoeiver as completely as you can, and then shake again. You will still hear some sound, because there is a continuous metallic contact between the bell and the open air through the plate of the air-pump. The difference in the sound of the bell when thus rung, first without exhaustion and then after exhaustion, is so slight, that the experiment is a failure. If you use Tate's air-pump, the only way to succeed with this experiment is to use an extra jsump-plate, No. 563, and the largest receiver you have at command, that is not too wide for the pump-plate. 696. This apparatus represents a call bell, mounted on a brass foot which rests upon a tidclc disk of felt. The bell is rung when a blow is struck upon the small table which surmounts it. A bell- shaped receiver is put over it, the largest at command, and the widest that fits the air-pump table. The receiver has a neck and ground mouth, upon which is placed the brass plate and sliding- 152 PNEUMATICS. rod, fig. 625, the hook at the bottom of it being first removed. The apparatus, as represented by fig. 696, being arranged upon the plate of the air-pump — the receiver being greased, if necessary, to make it fit the table — a blow is given to the bell by forcing the sliding rod down with a slight jerk. The bell sounds with an intelligible note. The receiver is then to be exhausted as thoroughly as possible, and another blow is to be struck by the sliding rod on the bell. If the exhaustion is good, there will be scarcely any sound produced. The thick disk of felt is interposed between the bell and the pump- plate to prevent the direct conduction of the sound through the pump. Fig. 696 may be called a successful bell experiment. 700. Leslie's Apparatus for freezing water in vacuo, over oil of vitriol, consisting of a flat bell-shaped receiver for the air-pump, a porcelain pan for the sulphuric acid, and a glass capsule for the water. The apparatus is represented hjj 1-, in fig. 518. Price of tlie set Js. 6d. 701. When the apparatus is to be used there should be put into the pan, half an inch in depth, of the strongest oil of vitriol (not the fuming Nordhausen acid). The pump must be well screwed up, the edge of the receiver be greased, to make it fit close, and the whole apparatus should have been kept for some time in a cool place. 27*6 above apparatus is suitable for use with Tate's small air- pump. 702. This experiment succeeds best -when the pump, the water, and the air of the room are as cold as possible. The pump and every part of the apparatus being in good condition, it takes twice as many strokes of the piston to freeze water when the air is at 60° Fahr. as it takes when the air is at 40° Fahr. In winter, when the apparatus and water are tolerably cold, Tate's pump will freeze the water with less than 100 strokes. In summer, at about 60°, it will require at least 150 strokes; and if you allow the water and pump to stand in the sun till they are warm, or if you take diluted acid, or/too much water, or too large a receiver, you will fail entirely. A small quantity of water is, of course, more easily frozen than a large quantity ; but when Tate's pump (the small size) is in good condition, and the weather cold, three or four ounces of water can be frozen, if placed in a thin porous earthenware capsule. In all cases the glass receiver must be as small and as flat as possible. 703. Porous evaporating Basins, for use in freezing large quan- tities of water, when the more powerful pumps are used ; red clay, Wedgwood's. 4 inches diameter, price Sd. 5 inches diameter, price is. 4c?. EXPEBIMENTS ON THE EXPANSION" OF AIE. 153 704. It is often recommended to freeze water by the evaporation of sulpliurio ether in an exhausted air-pump receiver. That opera- tion has several disagreeable points. The ether is very expensive, the vapour from it fills the whole room and is especially unpleasant to the operator ; it attacks the oil in the air-pump, and it fails more frequently than the process with sulphuric acid, when the latter is made with the precautions just pointed out. 705. Evaporation in a Vacuum. — It is often desirable in chemical operations to expel water from substances which cannot be heated without being made to undergo changes that are injurious. In such a case the chemist avails himself of the power of the air-pump. A porcelain pan, similar to fig. 705, is half filled with concentrated sulphuric acid, a liquid which rapidly absorbs aqueous vapour, and this is placed upon the table of the air-pump. The substance that is to be evaporated or dried is placed in a watch-glass or a porcelain capsule upon this pan. The whole is covered with a flat glass receiver, such as is represented in fig. 518, and the air is exhausted from the receiver. Water then rises from the substance that is to be dried to form an atmosphere in the receiver, but the concentrated sulphuric acid rapidly absorbs it ; fresh vapour is then formed and is absorbed by the acid, and thus the evaporation proceeds till the required result is produced. It is sometimes expedient to dry substances contained in filters without removing them from their glass funnels ; in which ease the arrangement represented by fig. 706 is useful. The lower part of this apparatus is made of porcelain, and the upper part of wood. Acid is put into the porcelain pan, and the wooden table being placed over it, the funnels and capsules containing the mixture that is to be dried are placed upon the table. The exhaustion and evapo- ration then proceed as described in the preceding paragraph. 705. 706 707. The apparatus last described is sometlrues employed with con- centrated sulphuric acid to dry substances without the aid of the 15i PNEUMATICS. air-pump. The method of proceeding is shown by fig. 707. b is a round wooden table, in wliicli is turned a circular groove, m ra. A is a glass or metal receiver, which fits the groove m m. a and 6 represent the apparatus, which is sho\vn separately by fig. 706. If the receiver a is made of tin-plate, the groove m m is filled with oil. If the receiver is of glass, the groove may be filled cither with oil or mercury. With this apparatus the evaporation goes on more slowly, because the air in the receiver prevents the rapid vaporisa- tion of the water. Group C. — On the pbessuke op the Air, § 711 to § 745. 711. Downward pressure of the Air. — Place a receiver on the plate of the air-pump and exhaust the air as completely as the pump permits. A gauge, § 575, may be screwed into the plate under the receiver, to show the degree of exhaustion attained. The re- ceiver will become so firmly pressed down upon the plate by the external air, that it would be exceedingly difficult to separate it by force. This will not yjj_ appear sm-prising when we consider that the glass is pressed down with a force equal to as many times 15 pounds as there are square inches covered by the bottom of the receiver. That is to say, a receiver of 7 inches diameter is pressed by about 577 lb., one of 8 inches by about 754 lb., and one of 10 inches by about 11781b. Hence the necessity, before removing an exhausted receiver, of relieving its pressure by an admission of air through the aircock. 712. Filter Cup, for causing mercury to be forced by the pressure of the atmosphere in a copious shower through extremely fine pores in a piece of wood, fig. 712. Price of tJie filter cup 7s. 6d. 712 A. Filter cup, small size. Price 4s. 6d. Place the apparatus represented by fig. 712 upon the air-pump plate and put a little mercury into the cup c ; then exhaust the air from the receiver, upon which an abundant silvery shower will fall from the end of the filter cup, in consequence of the pressiire of the atmosphere forcing the mercury through the empty pores of the neck of the cup. Fig. 712 contains the following pieces of apparatus : a, the plate of the air-pump ; b, a glass cylinder or receiver, with ground flange ; c, the wooden filter cup ; d, a ground brass plate belonging to the filter cup ; e, the ground -neck of the glass receiver ; /, the porous neck of the filter cup ; g, a glass jar, set to catch the mer- EXPERIMENTS ON THE PBESSDEE OF THE ATE. Lj5 cury and prevent its entering tlie pump ; h, a small porcelain stand, to keep open the way to the exhausting power. This is a compli- cated arrangement for a simple experiment ; but it serves to show one of the ways to be used to keep mercury, water, &c., from entering the air-pump. 713. Shower of Air in water. Apparatus for showing, fig. 713. Price ■js. 6d. This apparatus consists of a filter cup, the neck of which is a porous cane. When this is arranged as shown by fig. 713, and the receiver is exhausted, the pressure of the atmosphere through the cane and water to fill the vacuum in the receiver causes a copious shower of air to appear in the water. 712. 713. 714. Hand and Bladder Glass. — This instrument has this double name, because it is used for two purposes. There are also two forms, which differ in quality of glass and in price. 714. Conical form, German glass, fig. 714. Price is. 6d. 715. Swelled form, fine Bohemian glass, fig. 715. Price 3s. When placed with the narrow end uppermost, they are called hand glasses. When placed with the wide end uppermost, they are called bladder glasses. They must both have strong welts and be well ground on the edges. Their uses are as follow ; — 716. Experiment with the hand glass. — The hand glass is used to prove the pressure of the atmosphere. Set the large end on the plate of an air-pump, and place the palm of the hand so as to cover and close the small end. On the glass being exhausted, the pressure of the air is felt so strongly that it is nearly impossible 156 PNEUMATICS. to move the hand ; but if the air is admitted into the receiver, the hand will be again loosened. When this experiment is made in a school, the narrow end of the cone should be so small as to bo completely closed by the small hand of a child, otherwise the experiment fails. 714. 715- 717. Experiments with the Madder glass. — Preparation: a piece of thin and clean pig's bladder, soaked in water till it is quite flexible, is to be tied tightly over the wide end of the bladder glass and set aside till it is become dry and drawn tight, as represented by fig. 715. The narrow end of the glass is to be placed on the plate of the air-pump, and the air to be exhausted from it. The bladder, yielding to the external pressure of the air, assumes a concave figure, which increases in depth as the exhaustion proceeds, until the strength of the bladder is overcome by the incumbent weight of the atmosphere, and it bursts with a great report. In several books it is recommended to perform this experiment on the pressing powers of the atmosphere by placing a thin plate of ■window glass, instead of a bladder, on the top of the bladder-glass. If this is done, the glass is no doubt broken with a loud report ; but I have also known the glass cone to be broken and the glass to be scattered about dangerously. This experiment includes also the special chances of damaging the surface of the plate of the air- pump by scratches effected by the glass fragments, and of driving fragments of glass into the body of the pump through the hole in the plate. Immediately before use it must be ascertained that the bladder is dry and well stretched. The safest plan is to dry the bladder before the fire at the time. If it is left damp and slack, the experi- ment fails. If a barometer gauge is attached to the pump, access to it should be cut off by closing its stopcock, or it should be alto- gether removed from the pump before this experiment is made ; liecause the sudden rush of air into the pump, when the concussion occurs, is liable to destroy the gauge. EXPEKIMENTS ON THE PEESSUEE OP THE AIR. 157 718. In considering the performance of experiments with the hand and bladder glass, it is proper to bear in mind the approxi- mate weight of the atmosphere pressing upon openings of different sizes. Thus : If the diam. of the glass is i j in., the pressure is about 26 lb. 2 in., „ „ 47 lb. 2i- m., 3 m., 73 lb. 106 lb. This sufficiently accounts for the bursting of a pane of glass, or a dry and strained slip of bladder. But it also warns the operator to be cautious in experiments with the hand glass, and especially to see that the rim of glass on which a child is desired to press his hand is suitably prepared for that purpose, that the glass is thick and smooth, and free from sharp edges or points. 719. Weight of the Atmospltere. — Apparatus, consisting of a square bar of iron, i inch diameter, 15 lb. weight, to show to young people the amount of the pressure of the atmosphere per square inch at the surface of the earth. Price 6s. The length of bar iron having a cross section of I square inch, proper for this model, is ascertained as follows : 1 5 pounds multi- plied by 7000 gives 105,000 as the corresponding weight in grains ; 252-458, the number of grains in a cubic inch of water, multiplied by 7'7, the specific gravity of bar iron, gives 1944 grains as the weight of a cubic inch of iron. Then 105,000, divided by 1944, gives 54 as the number of cubic inches of iron demanded. But the bar itself being I inch square, it is only necessary to cut oif a piece 54 inches in length, to have a measure of the weight of the atmosphere. See § 752. 720. Crushing Power of Atmospheric Pressure, exhibited by a cylinder of thin tin- plate, measuring about 10 inches high by 4^ inches wide. Fig. 720. Price IS. 6d. A small quantity of water is boiled in this vessel over a gas-bur- ner or a spirit lamp till the atmospheric air is expelled by the steam. The cylinder is then promptly closed by a good-fitting cork and is placed in a pan, and a quantity of cold water is poured over it : the cylinder imme- diately collapses. 721. Upward Pressure of the Air. — Use for this experiment a glass jar with a smooth and level mouth. The form and size of the 158 PNEUMATICS. --fc jar are immaterial. Those represented by figs. 721, 722, and 723, all answer the purpose. Pill the jar quite full of water, cover its mouth with a piece of Bristol board or stiff writing-paper, put one hand lightly but steadily on the paper to keep it close to the glass, and with the other hand quickly invert the glass jar. It will then remain quite full of water, as shown by the figures, even when the hand is removed from the paper. The upward pressure of the air prevents the escape of the water as long as the glass jars are steadily kept in a vertical position. It is upon this principle of the eflfect produced by the upward pressure of the air that pipettes act (see § 361), and that mercury is upheld in the barometer (see § 747). Prices of these glasses : — 721. Size 6 by 3 inches, mouth 2I inches, is. 722. Tall conical test glass, 3 inch mouth, is. 723. Jar with foot and fiange, 6 by 2 inches, <^d. 724. Bottle of japanned tin-plate, with perforated bottom,, to show the upward pressure of the air. Price zs. To fill the bottle dip it into a deep beaker filled with water, permitting the air to escape from the bottle by the hole in the neck. When the bottle is full, close the _ hole by pressing a thumb on it, and lift the bottle out of the water, keeping it upright. Then, although the bottom of the bottle is full of holes, the water is re- tained until the hole at the top is opened. In short, this bottle acts on the same principle as the pi- pette. See No. 361. 725. Syringe and Lead Weight, for showing the pressure of the atmosphere. Price, without the re- ceiver and hook, los. This apparatus is intended to prove the pressure of the atmo- sphere. If the piston is pulled out to the fullest extent in the open air, on removing the acting force it immediately resumes its usual position, although the lead weight may be so placed as to exert its weight. The reason of this is, that when the weight is pulled down a vacuum is produced in the syringe, and there is no valve to per- mit the supply of air. But if the apparatus is suspended by the handle from the inside of a receiver placed on the plate of an air- pump, and the air is exhausted, the weight will immediately begin to descend, and its descent will be proportionate to the amount of exhaustion. On re-admitting the air to the receiver, the weight 724. 725. EXPEEIMENTS ON THE PEESSUEE OF THE AIE. 159 and body of tlie syringe will ascend in consequence of tlie atmo- spheric pressure. 726. Set of three Glass Globes, fixed one over the other, and so connected as to show the pressure of the atmo- sphere ; size of the globes 3 to 3^ inches dia- meter, with brass connectors. Price of the set 1 6s. 727. The set mounted with corks instead of brass tubes. Price 8s. 728. The glass receiver, to cover them, size 6 inches diameter, 20 inches in height. Price 25s. Use. — Nearly fill the lowest globe with co- loured water. The brass work unscrews be- tween the lowest and the middle globe for that purpose. Set the apparatus on the air-pump plate, cover it with a tall receiver, and exhaust. A small hole is pierced near the top of the middle globe, through which the air of the two upper globes escapes during the exhaustion of the receiver. The confined air left in the lowest globe will then expand and drive part of the water up into the middle globe through the jet pipe which extends from the bottom of the lowest globe to the top of the second. Admit air into the receiver ; that air will enter the middle globe by the small hole pierced in it, and its pressure will force up a quantity of water from the middle globe into the upper globe. After the experi- ment, the globes are to be separated by unscrewing the brass fittings, and emptied. 729. Fire Syringe, to set fire to German tinder by the sudden compression of air in a brass syringe. Price 4s. The German tinder should be quite « dry, and a small piece of it be put into |^ the cavity at the end of the piston. The piston should be pushed into the tube, and the knob at the far end of the tube being placed against some firmly-fixed object, the piston should be suddenly and forcibly driven in, and immediately withdrawn, when it ought to bring with it the lighted tinder. The operation requires a little practice. 729. -^UUM^ QY" .1^^- IGO PNEUMATIC?. 730. Bottle Imps, or Cartesian Devils, to illustrate the compressi- bility and elasticity of air. 730. Small grotesque iigures of coloured glass, a variety. Price, each c,d. 731. Larger figures, gondola, balloon, cage, &c. Price, each zs. 732. Pair of figures, mounted like fig. 730, namely, in a glass jar, measuring 12 inches by 3 inches, with foot and flanged mouth, with a piece of sheet caoutchouc, 6 inches square, to tie the mouth of the jar when the jar has been nearly, but not quite, filled with water, and the two imps have been put into it. Price 4s. N.B. — They can be delivered in London, tied over and filled with water ; but they cannot be safely sent into the country when filled. 733. The bottle imp is hollow, and has a small opening in one of the feet or in the tail. The weight of the figure is so adjusted that, with the included air, it is a very little lighter than water, and floats at the top of the jar. Nevertheless, when pressure is applied by the hand to the caoutchouc cover of the jar, the image sinks to the bottom of the water. As soon as the pressure is removed the figure rises again to the top. The reason of this is, that the pressure of the hand condenses the air left between the water and the cover of the jar. The condensed air then presses more heavily upon the water, and that in its turn upon the air contained within the image. This air is accordingly condensed into less space, and the image admits a little water, the addition of which makes the image and its contents heavier than the surrounding water, and therefore it sinks. When the hand is removed the compression ceases, where- upon the elasticity of the confined air begins to act. The air within the image, resuming its original volume, expels the water through the hole by which it had entered, and the image, thus restored to its original weight, rises in the water. If the pressure is continued until the image has too much water forced into it, it will no longer act properly. It should then be wiped dry, and be gradually warmed over a spirit-lamp until the heat forces out of it a sufficient quantity of the superfluous water. Of course, this warming requires a little care, to prevent the cracking of the glass. Another method of raising imps from the bottom of the jar is to put the jar under a tall receiver on the air-pump, and partially exhaust it ; the air within the imps then expands and drives out part of the water, and thus renders the imps lighter and able to float. EXPERIMENTS ON THE PEESSUKE OP THE AIR. 161 When a jar, like fig. 730, is to be set up, the empty imps are to be loaded with water by first gently warming them over a spirit- lamp and then dipping their feet or tail into cold water. Some water then goes into them. If not enough, repeat the process. If too much, expel a little by the method described above. When more water is required, hold the image with its head downwards while you heat it. If water is to be expelled, hold the image with its head upwards while you gently warm it. Sometimes glass images for this experiment are made in the shape of a balloon. The principle upon which they act is the same, and they require the same management. " This exceedingly beautiful philosophical toy,'' says Dr. Arnott, " proves many things : the materiality of air, by the pressure of the hand on the top being communicated to the water below through the air in the upper part of the jar ; the compressibility of air, by what happens in the image just before it descends ; the elastic force of air shown in expansion, when, on the pressure ceasing, the water is again expelled from the image ; the lightness of air, in the buoy- ancy of the image. It shows also that in a fluid the pressure is in all directions, because the effects happen in whatever position the jar be held ; it shows that pressure is as the depth, because less pressure of the hand is required the farther that the image has descended in the water : and it exemplifies many circumstances of fluid support. A young person, therefore, familiar with this toy, has learned the leading truths of hydrostatics and pneumatics, and has had much amusement as well as instruction." 734. Magdeburg Hemispheres, for showing the pressure of the atmosphere to be about 15 Ib^ per square inch. The power of the following instruments is found approximately thus : — Multiply the outside diameter by itself, and the product by twelve : the second product expresses pretty nearly the pressure of the atmo- sphere, or the adhesive force of the hemispheres in pounds avoir- dupois; thus 3i X 3i = 12I and 12I x 12 = 147 H^- Cast-iron hemispheres : — 734 ''• 32 ™cies outside diameter. Price 6s. 7346. 4^ inches ditto. Price 8s. Polished brass hemispheres, with brass handles and wooden foot : — 734 c. 2j^ inches outside diameter. Price los. 6d. 734^- 3^ inches ditto. Price 21s. 734 e. 4^ inch' s ditto. Price 358. These hemispheres are delivered without stopcocks. When in use, they require a stopcock, with one male and one female screw, fig. 591, the cost of which is 3s. M 162 PNEUMATICS. 735. The Magdeburg hemispheres, as represented by fig. 734 consist of two hollow hemispheres of brass or iron, fitting accurately together, furnished with two handles and a stopcock. On removing the moveable handle which is attached to the stop- cock, the hemispheres may be screwed to the screw-hole of the air-pump, or to an exhausting syringe, to be exhausted of air by it. The stop- cock must then be turned so as to prevent the re-admission of air; and on unscrewing the hemispheres and attaching the handles it will be found that they are firmly held together by the external pressure of the atmosphere, and the united exertions of two very strong men will not eifect their separation. It is scarcely pru- dent to permit boys to tug at the hemispheres ; for if they separate suddenly and the boys fall, the hemispheres may be dashed upon the fioor so as to damage the edges and put them out of use, especially when the hemispheres are made of cast-iron. But if they are suspended within a receiver. No. 684, by means of the brass ground-plate and hook, No. 624, and the air is exhausted from the receiver, their own weight is sufficient to separate them. A tray or other vessel should be put to receive the falling hemisphere, to prevent its damaging the face of the air-pump table. Another proof of the cohesion of the hemispheres is to hang to them a very heavy weight, say 50 lb., which it must be ascertained, before showing the experiment in a Class, the apparatus will carry with certainty. Before making an experiment, the ground edges of the two hemispheres should be carefully freed from dust, and be greased by means of the tallow holder. No. 638. Of course, pupils must be shown that the hemispheres do not cohere before they are emptied of air. 738. Glass Model of a Diving Bell, with chain to lower it into water, and Con- densing Syringe, to keep up a supply of air. Price, without the jar, 21s. This apparatus consists of a glass bell, arranged to illustrate the principle of the EXPERIMENTS ON MEASUEING ATMOSPHERIC PRESSURE. 163 common diving-bell. When it is lowered into a jar, filled with water, the action of the condensing syringe serves to supply the bell with fresh air. 739. Deep glass jar for working the above, about 18 inches high and 5 inches wide. Price 8s. 6d. Geoup D. — On the mbasdebmbnt of Atmospkeeic Pebssube, § 746 to § 790. Thb Baeombtek. Prices of fittings for Barometer Experiments, Nos. 746 to 758 : — 746. Support for tubes, fig. 746, black wood. Price 4s. Ditto, mahogany. Price 5s. 6d. 747. Glass mortar, or basin, 3^ inch. Price lod. 748. Straight barometer tube, empty. Price is. 6d. 749. Porcelain cup, with sharp spout. Price is. 751. Chrome-lithographic scale of 40 inches, with iron stand. Price Js. 751 a. Ditto, scale of 100 centimetres, with stand. Price Js. 6d. 751 6. Syphon or cistern barometer tube. Price 2s. 753. Barometer tube and receiver, with caoutchouc stopper, but without mercury basin. Price 4s. 754. Barometer tube, with receiver with ground mouth, ground brass plate, and stuffing-box. Price 1 zs. 6d. 755. Bottle, with barometer tube and cork. Price 3s. 6d. 756. Tall receiver, 36 inches high, Bohemian glass. Price 1 8s. 758. Bottle, with open tube and caoutchouc stopper. Price 3 s. 6d. 758 a. Set of six borers for caoutchouc stoppers, with file, in case. Price 3 s. 781. Slip of whalebone, 3 feet long, for clearing air from mercury in a barometer- tube. Price is. 746. The Torricellian Experiment. — In experiment 721 we have seen the upward pressure of air exerted to sustain water in three glass jars filled quite full and placed in a vertical position, with their mouths downwards. In fig. 746 we have an experiment represented, in which a column of mercury is sustained by the upward pressure of air in a glass tube which is closed at the top and open at the bottom. The open end of the tube rests in a glass basin containing mercury. The tube is about 3 3 inches long. The mercury in it rests at a point marked 30", which signifies 30 inches from the surface of the mer- cury in the basin. The space above the 30" in the tube is a vacuum. This figure represents a temporary barometer. We proceed to explain M 2 164 PNEUMATICS. the method of preparing it, and' how it is that by means of it we arc able to prove what is the weight of the atmosphere. 750. 747. How to fill a Barometer Tuhe with Mercury. — Take a clean dry warm glass tube, closed at one end, open at the other, 33 inches long and about ^ inch in the bore, or of the size O^dibk of fig. 747. This size is most convenient for ^S filling without loss of time and waste of mer- cury. The tube holds when full about i^ lb. of mercury. A narrow tube of about ^ inch bore, nearly like fig. 748, can be filled with less 74:- 748. THE BAEOMETEE. 165 mercury, but the operation of filling it and also of emptying it is much more troublesome and liable to considerable loss of mercury, in consequence of the difficulty of getting the air out of the tube while the mercury is being passed into it. When it is absolutely necessary to fill a very narrow tube, it can be best done by using a long and very narrow tube as a funnel, the mouth of it being a little widened, in a funnel form. The glass tube being provided, mercury is to be poured into it. The mercury, clean and dry, should be held in a small porcelain cup having a sharp spout, fig. 749 ; the tube should be held in a slanting position and the mercury be passed into it a little at a time, say as much as will fill 4 inches in length of the tube. The tube shouldthen be held in an upright position and the lower end be gently struck upon a solid piece of felt laid upon the table or the floor ; that agitation causes the bubbles of air to collect together and to rise above the mercury. Then another quantity of mercury should be passed into the tube and the air be again shaken out, and that operation is to be repeated until the tube is filled with mercury up to within half an inch of the open end ; then you should close the opening with your finger and partially invert the tube so as to bring the sealed end a little higher than the end closed by your finger. The air that was left at the open end of the tube then passes to the sealed end, carrying with it many small bubbles of air that had been i-etained by the mercury. The level of the tube is then to be altered and the bubble of air to be again passed through the mercury, the tube being mean- time revolved a little to bring a fresh surface of mercury upwards. After repeating this operation four or five times, the small bubbles of air will have been carried away. If, however, any remain visible, the process is to be repeated till they are all swept out. 750. Next fill the tube with mercury to the top, brimfull ; hold it with your right hand applied near the middle of the tube ; close the opening with the fore-finger of the left hand ; invert the tube carefully, without letting air into it ; plunge the end of the tube below the surface of the mercury contained in a trough, for which a stout glass mortar serves well, and then remove the finger (see fig. 750). Upon the removal of the finger the mercury sinks in the tube to such an extent as to leave in it a column of mercury that measures about 30 inches from its upper surface to the surface of the metal in the mortar. The exact number of inches depends upon pressure of the atmosphere at the time of performing this operation, which pressure varies from day to day. Above the 30" of mercury is a space — a vacuum. You will observe that there can be no air in that space, for until the finger that closed the orifice of the tube was 166 PNEUMATICS. taken away in the basin, that space was filled with mercury, and the column of mercui'y, which was 3 3 inches high, sank in the tuhe and left that space of 3 inches free from air ; for no air could get into the tube unless it could force its way through the mercury in the basin and through the 30 inches remaining in the tube, or else penetrate through the sealed end of the glass tube. But, since neither of those could be done, it follows that the part of the tube which the mercury leaves must necessarily be a vacuum, unless, indeed, we consider it to be filled with a vapour of mercury, vola- tilized at mean temperatures. 751. Scale to measure tlie Jieiglit of the mercury in the Barometer, fig. 751 . — This is a chromo-lithographic scale of 40 inches in length, coloured and mounted on a board, as described in § 141. The board is connected with a support, as represented by fig. 751. a is an iron rod, 5 an iron foot or base, c is a thumb-screw connected with a bar that is attached to the board, and d is & guide intended to keep the scale in a vertical position. The scale can be raised or lowered so as to put the zero of the measure in any desired posi- tion. Thus, if it is made to touch the surface of the mercury in the basin or mortar of fig. 746, it will then show the exact height of the mercury in the tube of that apparatus. 751a. Measures can be supplied, similar to fig. 751, but graduated to 100 centimetres, instead of 40 inches. 7516. Syphon Barometer. — In the syphon barometer the tube and cistern for holding the mercury are in one piece of glass, as represented by fig. 751 &. The height of the mercury is the distance between the surfaces at a and at 6. The tube should be of the length and width described in § 747, and the cup & of 751 6 should be about I inch in diameter. The tube is filled with mercury by the following process : — Hold the tube upright, as repre- sented in the figure. Fill the bulb h quite full of mer- cury, poured into it from the porcelain cup, fig. 749. Close the mouth of 6 with your thumb, bring the tube into a horizontal position and transfer the mercury, or as much of it as you can, by a series of jerks from the bulb into the tube. Bring back the tube into the position fig. 75 1 &. Again fill the bulb, and again jerk part of the mercury into the tube. Eepeat this process four or five times and the tube will be full. The bubbles of air are to be collected together and swept out by alternately raising and lowering the two ends of the tube, as de- ,„ J scribed in § 747. When the air is all expelled the tube is to be filled as completely as possible, and then raised J THE BAEOMBTBE. 167 into tlie vertical position, fig. 751 6, when the mercury will sink and produce a vacuum at a. The bulb b should he half filled with mercury, and the tube should be put into a support like that of fig. 746. The distance between the two level surfaces of mercury at a and 6, measured by the scale, fig. 751, should be 30 inches, or what may happen to be the barometric pressure of the day. 752. Deduction of the weight of the Atmosphere fvom the Torri- cellian experiment. — The pressure of the atmosphere suffices to sustain a column of mercury of 30 inches in height. If the tube that contains the column of mercury has a horizontal section of I square inch, the result is the same as that obtained with the narrow barometer tube. The weight of a column of the atmosphere of I square inch in section at the surface of the earth is therefore equal to the weight of a column of mercury of the same section and 30 inches in height. That weight is easily determined thus : — I cubic inch of water weighs 252-458 grains, and i cubic inch of mercury weighs 13-6 times as much, or 252-458 x I3"6 = 3433-4288 grains, and this, multiplied by 30 for the height in inches, comes to 103,002-8640 grains, or, reduced to pounds, it is 14-7147, or nearly 15 pounds upon the square inch, equal to 21 ig pounds on the square foot. The surface of a man's body is commonly assumed to measure 15 square feet. In that case the atmospheric pressure upon him is 21 ig X 15 = 31,785 pounds. 753. Mercury can be raised in a Barometer Tube ■ by atmospheric pressure. — Fig. 753 represents a ba- rometer tube connected with an air-pump receiver by a perforated caoutchouc stopper. At the bottom of the receiver is a glass mortar, containing rather more mercury than will suffice to fill the tube. The apparatus, as figured, is placed on the plate of the air-pump, and the tube is pulled up so as to make its mouth clear the mercury. The sliding of the glass tube in the caoutchouc stopper takes place easily if the tube is well smeared with tallow. The pump is now to be worked and the air exhausted as completely as possible. That you may know how the exhaustion is proceeding, the pump ought to be provided with a side gauge, such as c, d, fig. 517. When the exhaustion is complete, there is, or ought to be, no air either in the tube or the receiver. Push the barometer tube gently down into the mer- cury and slowly admit air into the receiver by the aircock. This air, acting upon the surface of the 168 PNEUMATICS. mercury in the basin, drives it up into the barometer tube, higher and higher in proportion to the excellence of 'the previous ex- haustion. Of course, when the barometer No. 746 stands at 30", the mercury in this apparatus, measured by the graduated scale No. 751, ought also to stand at 30". But it rarely comes quite so high, because of the imperfect exhaustion both of the receiver and the tube. Nevertheless the experiment shows very clearly that the support of the mercury in the tube is entirely due to the pressure of the air. 754. The apparatus 753 is generally made with brass fittings, including a stuf&ng-box for the barometer tube. That is a more elegant and more accurate method of mounting it. But the action of the caoutchouc stopper, well greased, is satisfactory. 755. Mercury is supported in the Barometer by the pressure of the Atmosphere, and it sinks in the tube when that pressure is removed. — The apparatus required for this experi- ment is represented by figs. 755, 756. 755 is a narrow, new, and clean ba- rometer tube filled with mercury by the process described in § 747. It is con- nected with a small wide-mouthed bottle by a cork that holds the tube upright, but does not fit the bottle air-tight. In preparing this apparatus, the tube and bottle are both to be quite filled with mercury, the cork is to be pushed up out of the way, and the tube dipped into the bottle without admitting air — a pro- cess requiring a little dexterity. Most of the mercury is then to be poured out of the bottle, leaving only enough to cover the mouth of the tube. There must be enough space left in the bottle to receive all the mercury contained in the tube when it is subsequently made to descend. Adjust the cork so as to keep the tube upright, put the bottle on 755- 756- the plate of the air-pump, and cover it with the large receiver, fig. 756. 756. This receiver measures about 36 inches high, the tube of it is 2 inches wide and about 30 inches long ; the lower part measures 5 inches across the ground flanges. 757. The apparatus being properly adjusted, the air-pump is to be worked. The mercury in the tube immediately begins to descend, aind. as the exhaustion continues, the mercury constantly descends maeiotte's apparatus. 169 until it has all left the tube and gone into the jar. There will then be a vacuum in the receiver. A column of 30 inches of mercury was suspended in the barometer tube when the air pressed freely on the mercury in the bottle, but the mercury sank as the pressing air was withdrawn, and none was left in the tube when the receiver was fully exhausted. The conclusion, that it is the weight of the air that supports the mercurial column is confirmed by the admission of air into the receiver by opening the aircook of the pimip, for the air then rushes into the exhausted bottle, and pressing the mercury into the tube, makes it rise till it stands therein at its former height of 30 inches. 758. Tlie elasticity or spring of the Air is equal to its compressing force. — The apparatus required for this experiment is represented by figs. 755, 756, excepting that 755 is mounted as follows: — The bottle is to be half filled with mercui-y, the tube to be open at both ends, and dip deeply into the mercury ; and the stopper must be of caoutchouc, and fitted air-tight both to the bottle and the tube. It may not be amiss to state here that perfectly round holes can be cut in caoutchouc stoppers by using brass cork borers, fig. 758 a, filed r\ f^'\ pretty sharp on the cutting-edges a V J 2' and thoroughly wetted with spirit of .,g ^ wine. In use, the joints between the glass tubes and the caoutchouc should be greased with tallow. Process. — Place the apparatus, fig. 755, corrected as above de- scribed, on the table of the air-pump, cover it with the receiver, fig. 756, and proceed to exhaust the air from the receiver. As that exhaustion goes on, the air in the bottle expands, and pressing upon the surface of the mercury, forces it up the tube. When the ex- haustion is completed, the mercury will be nearly at barometer height in the tube. On admitting air into the receiver, the mercury descends from the tube into the bottle. Maeiotte's Appaeatus fob showing the compeessibilitt and ELASTICITY OF AlK. 780. The volume of a given weight of air is inversely as the pressure to which it is exposed ; that is to say, the greater the pressure to which the air is subjected the smaller becomes its volume, and the less the pressure the larger is the volume. This is commonly called the law of Mariotte. It was discovered independently by jMariotte in France, and Boyle in England, about the year 1670. We demonstrate the truth of this law by two experiments : one, fig. 781, to illustrate the effects of pressure greater than that of the 170 PNEUMATICS. atmosphere ; the other, fig. 782, to illustrate the eflfects of pressure less than that of the atmosphere. 781. Mariottes Apparatus, constructed to sJiow that, under the pressure of two atmospheres, air is compressed into half its ordinary bulk, fig. 781. Price i8s. This apparatus consists of two graduated glass tuhes connected by iron fittings. The short tube is graduated to show its cubical contents, and has twenty- divisions in two spaces of ten each. The long branch is graduated to show 32 linear inches. The tubes are both about J inch in diameter. The iron base is perforated, so that the two glass tubes are in direct commu- nication with one another. The apparatus requires 2 J lb. of mercury to work it. Use. — By means of the key, h, unscrew the tubes, and see that the leather washers are in good condition. If not, replace them with new ones (see § 611). Then screw up the tubes, shut the stopcock, unscrew the cap on tie short tube, and, with the help of a small funnel, put into the apparatus as much mer- cury as will rise up to 20 in the short tube and to a in the long tube. Screw on the cap of the short tube. You have now, eon- fined in that short tube, 20 measures of air, acted upon by the pressure of the atmo- sphere at a. Pour into the long tube as much mercury as will rise to the mark 30 inches near the top of the scale. Eemove the air bubbles by dipping into the mercury a long narrow slip of whalebone (not a metal wire), and adjust the mercury at 30 inches. The air in the short tube will then be level with ro on the scale ; consequently 20 parts of air, when under the pressure of one atmo- sphere, become 10 parts when under the pressure of two atmospheres. 781 a. The apparatus, fig. 781, is an ex- ample of the communicating vessels with two liquids, which were described at § 215. In the first part of the above experiment we have a level line of junction seen at 20 in one tube, and a in the other, and the liquids in equilibrium are the un- condensed air in the short tube, and the atmosphere in the long tube. In the second part of the experiment we have the level line of junction MARIOTTES APPAKATTJS. 171 elevated to lo in the short tube and to o in the long tube, while the liquids in equilibrium are the lo volumes of condensed air in the short tube, and in the long tube a compound of 30 inches of mercury j;Zms the pressure of the atmosphere. We see, therefore, that the 10 measures of condensed air have a power of pressure or resistance equal to that of two atmospheres, or to 60 inches of mercury. When the experiment with fig. 781 is concluded, the mercury should be removed from it. The base of the apparatus should be placed near the edge of a table with the stopcock projecting beyond it, and a glass bottle be so held below the stopcock, that when the latter is gently opened the mercury may be collected in the bottle without loss. 781 a. Price of slip of whalebone, 3 feet long, is. 782. Mariotte's Appm-attis, constructed to show that, under the pres- sure of half an atmosphere, air expands to twice its ordinary volume, fig. 782. Price I2S. This apparatus consists of two glass tubes, a being about 22 inches long by J inch wide, and b about 24 inches long by f inch wide, a is mounted with a small stop- cock, and is graduated, first, into two equal cubical spaces, marked i and 2 ; and secondly, with a scale of 16 linear inches, beginning with o at the mark 2. 6 is supported by a large and heavy wooden foot, about 6 inches wide and 5 inches high. This apparatus, like fig. 781, requires 2^ lb. of mercury to work it. Use. — Fill the tube b with mercury up to about 2 inches from the top. Eemove air-bubbles by means of the slip of whalebone mentioned in the preceding article. Then open the stopcock of the tube a, and slowly plunge the graduated open end of that tube into the mercury contained in the tube h. It must go down so far as to cause the mark I to be on a level with the surface of the mercury then present in both tubes. To make this convenient, the mercury in the tube b should come to about an inch from the top when the tube a is immersed in it. When this point is adjusted, the stopcock of the tube a is to be closed. You have then in that tube I measure of air at atmospheric pressure. Pull up tube a slowly with the mercury which rises within it until mark 2 is found level with the surface of the mercury con- tained in tube a. Then, upon reading the scale of inches engraved i 782. 172 PNEUMATICS. on tube a, commencins! at o at the level of 2 on the same tube, and descending, you will find that the surface of the mercury in the outer tube rests where 15 inches is marked on the inner tube ; conse- quently the volume of the air enclosed in tube a is enlarged from one to two volumes, while the atmospheric pressure is reduced to 15 inches of mercury. As the figures on the narrow tube a are necessarily very small, it is convenient to show the space of 1 5 inches between the two mercury levels in a and h, by using a chromo-lithographic scale of 20 inches, mounted on wood, as described at § 141. 782 a. We have shown in § 781 that the apparatus there described may be taken as an example of the communicating vessels with two liquids which were described at § 215. The same may be said of the apparatus represented by fig. 782. In the first part of the experiment the tube a is plunged into the mercury contained in tube 6 (the stopcock of a being first opened) until the mercury in both tubes is level at the mark I on the small tube, that tube being held steadily in its place to prevent its swimming. At that moment the level of the mercury in both tubes is the horizontal line of junction, and the atmospheric air pressing upon the mercury in both tubes is in equilibrium. In the second part of the experiment the stopcock a is closed and the small tube is lifted up with the mercury that rises with it until there is a difference of 1 5 inches in the two levels of the mercury. At that moment the horizontal line of junction is level with the surface of the mercury in the tube. 6, and with the line of 15 inches in the tube a. Above that line of junction there rests in tube h the pressure of one atmosphere, and in the tube a there is first the pressure of 1 5 inches of mercury, equal to half an atmosphere, and above that the pressure of the expanded air, which must be equal to another half atmosphere, in order to complete the pressure necessary to produce equilibrium. GLASS EECEIVEES FOE AIE-PUMPS, All with Flanged Eims, Ground Flat, ready foe itse. The measurement of Width includes the Ground Flanges. The measurement of Height is from the base to the centre of the Dome, inside the Receiver. 796. The flat ground flange of the receiver that rests upon the plate of the air-pump commonly measures from ^ inch to i inch across. The bore of every receiver is therefore from f inch to I inch less than its extreme width over the flange or welt. It is GLASS EECEIVERS FOE AIR-PUMPS. 173 this extreme width over the flange that serves to show for what air- pump plate the receiver is suitable. Thus a 7-inch air-pump plate (see No. 505) will take a receiver that has an extreme width of 7 inch, or any smaller size ; but it will not work with any receiver that is wider than 7 inches, not even with one of 7^ inches. In selecting receivers for the air-pump, the widtli is therefore the main thing to which attention must be paid. The height may be variable, and indeed is necessarily variable for different appa- ratus. As a general rule the receiver should be so small as merely to cover the object submitted to experiment, because the smaller it is the less work there is for the pump to do in exhausting the air from it. This is sometimes important, as, for example, in the ex- periment of the freezing of water, § 700, in which case a small flat receiver is essential. On the contrary, for the trial of the bell in vacuo (see §§ 695, 696), a large receiver best answers the purposes of the experiment. When, again, an experiment is to be made at a lecture, and to be seen by a large audience, it is proper to have some space between the apparatus set in action and the dome of the receiver that covers it, otherwise the apparatus is liable to be ren- dered invisible by the play of light from the glass dome. Finally, there is the fact' to be dealt with, that every operator wishes to have as few receiver's as possible, in order to limit his expenses. In the following list some care has been taken to point out the most useful forms and sizes, and the operator who compares this list with the figures and descriptions in the chapter on Pneumatic Experiments, will be readily led to select what are most suitable for his purposes. 797. All the receivers described in this list are of hard glass, not flint gluss. Those in the column^.' headed b are of fine Bohe- mian glass, and handsomely finished. Those in the column headed g are of hard German glass, not quite so clear from specks and free from colour as the Bohemian glass. The whole are well annealed. 798. Exact sizes are specified in the lists of glass vessels in order to guide purchasers in their choice, and when instructions are received by the advertisers to supply vessels of special sizes, these instructions will be attended to as closely as possible ; but at the same time no guarantee can be given that in such cases the mea- surements shall be correct to small fractions of an inch, for it is impossible to have glass vessels manufactured with such scrupulous exactness in non-essential particulars. Very great changes in the price of glass have taken place during the years 1872-73. While this sheet was in the press, a rise of 1 5 per cent, occurred close upon previous rises ; consequently the prices in this list must be considered as the pices of the day, but not unalterably fixed. 174 PNEUMATICS. 800. Flat Receivers for Air-pumps. 809. Cylindrical Meceivers. Kii Inches wide. Inches high. Peices. No. Inches wide. Inches high. Pbices. B G. B. G. 800 6i 3i s. 4 6. 2 6 809 % 8 s. s s. 3 801 7 4 4 6 2 6 810 7 8 6 I 3 802 8 6 7 3 6 811 7 12 9 o| 5 803 10 6 II 6 4 6 8l2- 8 12 10 6 ; 6 804 Hi 7 17 6 6 813 814 81S 816 10 4 6 5 14 6 20 36 22 2 38 »1 - 6 j I ' GLASS EECEIVEES FOE AIE-PUMPS. 175 840. Bell-shaped Beceivers. Bell-shaped Beceivers imth necTcs. -^^^ Jnches . wide. 1 Inches high. Prices. 840 Inches wide. Inches high. Peices. B. I G. B. 1 G. 82s 4 6 s. d. 3 8 d. 2 6 4 6 s. ri. 3 6 s. d. 2 6 826 6i 8 7 6 3 6 841 6i 8 8 3 6 827 7 8 9 4 842 7 8 10 4 828 8 loi 14 6 6 843 7 12 13 6 6 829 10 12 24 9 844 8 loi IS 6 6 j 845 10 12 25 9 Tlie necks of the receivers, fig. 840, are 3 inches in bore, and 4 inches across the ground flanges. They are adapted to the brass plate of the hook, fig. 624, and the sliding-rod, fig. 625. 176 PNEUMATICS. 860. Cylindrical Beceivers with necks. 880. Gdnical Fountain Glasses. JNO. Inches wide. Inches high. Pkioes. No. Inches wide. Inches high. Pbioes. B. G. B. 860 5 14 s. d. 9 8. d. 4 880 4 15 s. d. 7 6 s. 4 861 7 12 12 6 5 881 S 15 12 6 5 862 10 14 24 •• 882 5 21 18 6 The necks of the above are 3 inches in bore, and 4 inches over the ground flanges. Like fig. 840, they fit the brass, plate of the hook, No. 624, and. the sliding-rod, No. 625. 866 4 10 5626 With neck of 2^ inches bore, and 3^inches over the ground flanges. Used for the filter cup, No. 712. GLASS KECEIVEES FOE AIE-PUMPS. 177 (trwi'" 888. Guinea and Feather Glasses. 815. 895. 815. Tall Cylindrical Becehers. 895. Tall plain Jars. No. Wide at bottom. Wide at top. Inches high Peices. No. Inches wide. Inches high. PfllOES. B. s. d. G. B. 1 G. s. d. s. d. 8. C 588 4i 4 16 15 5 895 4 30 18 889 5 4 18 18 6 896 4 16 8 3 ' 390 5 4 24 21 7 6 » 178 PNEUMATICS. MISCELLANEOUS GLASS FITTINGS, Fob Pneumatic and Hydrostatic Experiments. 901. Bohemian glass basins, flat bottoms, with vertical sides, fig. 901. No: Wide. Deep. Contents. Price. 901. 6 inches 3^ inches 2 pints IS. id. 902. 8 „ ' S „ 6 „ 2s. 6d. 903- 9 „ 5h „ 8 „ 3s. 3d. 904. 10 „ 6 „ 10 „ 4«. 6d. 905. 15 „ 7 „ 28 „ 15s. 913. Deep conical stoneware pans, salt glazed, fig 9' [3- 913. Diameter 8 inches, contents 3 pints. Price IS . Sc?. 914. 10 „ 55 5 J) » 28 915- 12 .„ 3) ° )3 3) 2S '.6d. 913. 916 917. 916. Glass jars on feet, hard German glass, with flanged mouth, fig. 916, or with spout, fig. giy, at the same price. Sizes as follow : — No. High. Wide. Price. 916. 6 inches 2 inches lod 917- 8 „ 2 ,, i». 918. 10 „ 2 „ IS. MISCELLANEOUS GLASS FITTINGS. 179 Glass jars on feet, continued. No. High. Wide. Price. 919. 12 inches 2 inches IS. 4^?. 920. 15 )T 2 ., i«. 8d. 921. 8 ?3 4 .- IS. 4& 922. 10 5) 3 „ IS. 6d. 923- 12 !J 3 „ IS. 9d. 924. 10 3J 4 J, 2s. 6d. 925. 16 )5 5 „ 6s. Many other sizes can he supplied. 916 c. Circular disks of htout plate glass, polished on both sides and on the edges, fig. 916c: — 3 inch, pn'ce is. 4 inch, is. 6d. 5 inch, 2S. 6 inch, 3s. 931. Wide-mouthed bottle, to use as water reservoir in fountain experiments, size 12 inches high, 5 inches wide, mouth 2^ inches in bore. See a, fig. 516. Price 3s. 936. Bohemian glass beakers for holding liquids, either hot or cold, large set of 15 beakers, holding from i ounce to 220 ounces, fig. 936. Price 1 6s. 937. Ditto set of 8, from 8 to loo ounces. Price gs. 938. Ditto set of 5, from 3 to 18 ounces. Price 3s. 941. Griffin's beaked "tumblers, with spouts, set of 6, contents from 5 ounces to 40 ounces, fig. 941. Price ^s. 936. 941. 943. Conical beakers, with spout, fig. 943 : — ^ pint, price Sd. ^ pint, price lod. li pint, price is. 3d. 3 pints, price is. 9^. 4^- pints, price 2s. 6(7. 9 pints, price 3s. 6d. N 2 180 PNEUMATICS. 945. Glass funnels, fig. 945 : — 1 incli,^nce lid. | 4 inch, price 4(1. 2 inch, price 2d. \ 6 inch, price lod. 946. Funnel holders for small funnels, black wood. Price is. 947. Ditto for large funnels, mahogany. Price 5s. ( 181 ) INDEX. Adhesion plate, 19 Air, difficulty of extricating it from water, 142 ; and from mercury, ,65 its elusticity equal to its compress- ing ibrce, i6g its extrication from various bodies, 145 weiglied, 136 Air-pumps, in Tate's, mounted on clamp, 115 on pedestal, 121 on table, 122 large size, 123 with fly-wheel, 124 with eitra fittings, 122 compared with other pumps, 119 details of construction, 116 with two vertical barrels, 114 with two barrels, raised plate, 115 with three barrels, 124 one barrel, small size, 126 exhausting power of, 112 extra fittings for, 128 instructions for care of, 127 labour of working diiferent kinds, J 25 Air syringes, brass, 127 condenhing, 128 exhausting, 127 exhausting and condensing, 128 with clamp, 128 Alcoholometer, 75 GaA -Lussac's, 78 Sikes's, 79 Tralles's, 78 Ale, air from, 147 Apple cutter, 148 Appold's centiifugal pump, 109 Archimedes, princi(.le of, 5 7 experimental demonstration of, 59 Archiniedian screw, glass, 109 model in metal, 109 Atmosphere, weight of, iron bar to represent, 157 weight of, how deduced from the Torricellian experiment, 167 Atmospheric optic marvel, 26 pressure, crushing power of, 157 measurement of, 163 Attwooii's fall machine, 20 Aurora borealis apparatus, 135 Balance extemporised, 3 hydrostatic, 32 Mohr's, 69 for accurate weighings in case, 33 in mahogany box, 34 commercial, 34 Balloons, 139 Barker's mill, in glass, 48 in metal, 47 Barometer, 163 to fill with mercury, 164 support for, 164 scale for, i65 syphon, 166 mercury raised in it by atmo- spheric pressure, 167 effect of removing that pressur(f, 168 Baroscope, 140 Batavian tears, 3 1 lleiiker glasses, 179 Beer, air from, 147 Bell shaped receivers for air-pumpa, 175 with necks, 175 Bells to be rung in vacuo, 150 Bliick rail, i Bladder experiments, 148 frame and lead weights, 149 glass, 155 experiments with, 156 piece, 132 Bladders, preparation and care of, 149 182 INDEX. Blank nut, 131 Bohemian beakers, 1 79 Bolognian flasks, 31 Bottle imps, 58, 160 Bottles, specific gravity, 65 Bottle to hold ^ gallon, 64 Bowl-about, 15 Boyle's inverted U tube, 43 Bramah press, glass, 50 small brass, 50 large brass, 5 1 Brass pulleys, set of, 10 Breaking squares, 150 Breast water-wheel, 109 Brittleness, 31 Bulb gauge and jar, 144 Bulb pipettes, 85 Burette, 86 Binks's, 86 Gay-Lussao'Sj 86 Mohr's, 86 Caoutchouc balls, 134, 149 Capillarity, 81 Capillary plates, 82 tubes, 83 Caps for air jars, 132 Carbonic acid gas weighed, 139 Cartesian devils, 160 Cathetometer, 31 Central forces, laws of, 22 Centre of gravity, 14 instruments for showing, 1 4 bowl-about, 15 brass semicircle, 14 double cone, 15 equilibriste, 15 irregular board, 14 leaning tower, 14 parallelepipeds, 14 Centrifugal machine, 22 adjuncts for 12 experiments, 23 Centrifugal pump, Appold's, 109 railway, 29 Chromatic fire-cloud, ro2 Chromo-lithographic scales, 36, 166 Clamps, 135 Clinometer, 32 Clip and weight, 133 Coke, air extricated from, 147 Collision, 19 Communicating vessels, 3 7 for one liquid, 3 7 for two Uquids, 40, 4 1 for three liquids, 42 Compound wheel and axle, 12 Condensed air fountains, 99 with glass reservoir, 99 large zinc reservoir, 99 small brass reservoir, 10 1 jets for, 101 syringes to supply air, 102 Cone for illustrating stability and instability, 16 Cone of water weighed, 55 Conical beakm-s, 1 79 Conical fountain glasses, 176 Connectors, brass, 130 I, 2, 3, and 4 way, 131 Constructive mechanics, 29 Cord for pulleys, 2 Cork, air extricated from, 147 Cork and balance weiglit, 140 Crimson dye for water, 38 Crushing weight of the atmosphere, 157 Cylindrical receivers for air-pumps, 174 with necks, 1 76 Dialyser, Graham's, 31 Diving-bell, 162 Double cone, to roll up hill, 15 Double tiansferer, 134 Downward pressure of the air, 154 Elastic balls, 149 Equilibrium of a floating body, 80 of solids, 16 of solids when immersed in liquids, 57 Equilibri&te, 15 Evaporation in vacuo, 153 Exhausting powers of air-pumps, in Expansion of air, 144 Eye fountain, 93 Palling bodies, laws of, 20 Filter cup for mercury shower, 154 for shower of air, 155 Filtering-paper, 82 Filtering-tube to show capillarity, 82 Fire engine, glass model, 95 metal, 95 Fire syringe, 159 Flat receivers for air-pumps, 174 Floating bodies, weight of, estimated by measuring the water they dis- place, 79 Flotation, 79 INDEX. 183 Force pumps, 94, 95, 96 Heron's ball, 103 Forge hammer, 30 fountain, 104 F(jun tains, 97 glass model, 104 produced by a fall of water from an metal model, 10; eminence, under common at- Ilnoke's universal joint, 30 mospheric pressure, 98 Hooks for blackboard, i when condensed air forces a water Houdin's inexhaustible bottle, 83 jet into free air, 99 Hydraulics, 81 when uncondensed air forces a Hydrodynamics, 8t water jet into an exhausted Hydrogen gas weighed, 139 receiver, 102 Hydrometers, 73 when a column of water con- forms of, 73, 74, 76 denses a confined portion of jars for, 73, 74, 76 air and causes it to force a Baume's, 77 water jet into free air, 104 Nicholson's, 72 ■when a fall of water from a Twaddell's, 77 syphon creates a vacuum into special scales for, 7 7 which a water jet is forced by rules for using, 78 free air, 105 price list of, 78 when an inteixupted supply of Hydrostatic balance, 22 air causes a spring to be inter- Mohr's, 69 mittent, 107 bellows, 49, 50 Fountain glasses, 176 paradox, 52, 57 syphon, 93 press, 50 Freezing of water by the air-pump, principle, Pascal's, 5 3 152 Hydrostatics, 37 Fruit stand, r48 Fulcrum for lever, 2 Inclined plane, 10 Funnels, 180 Indigo blue dye for water, 38 Inertia illustrated, 27 Glass basins, 178 apparatus, 16 Glass breaking squares, 150 Intermittent fountain, 107 Glass jars on feet, 178 motion, 29 Governor, Watts' s, 25 spring, 107 Graduated measures for ounces, 35 Iron pins and hooks, ^ for grammes, 35 Iron connectors, 130 Graham's dialyser, 31 Iron stopcocks, 130 osmometer, 31 Irregular board to show centre of Gravesende's lever, 6 gravity, r4 Gravity, centre of, 14 Grease for air-pump receivers, manage- Key, 135, 170 ment of, 136 Ground brass plate and hook, 133 Lactometer, 79 with sliding rod, 133 Lateral pressure of liquids, 47 Guinea and feather experiment, 142 Laws of falling bodies, 20 brass work for, 142 Leaning tower, 14 glasses for, 1 42, 177 Leslie's apparatus for freezing water, long tube for, 143 152 Gyroscope, 27 Level of different liquids in commu- small size, 28 nicating vessels, 39 Gyroscopic top, 28 of junction of two liquids, 39 of water in communicating vessels, Haldat's hydrostatic apparatus, 54 37,38,39 Hand glass, 155 Lever, 2 Hempel's syphon, 92 of the first kind, 4 184 INDEX. Lever : Pipettes : of the second kind, 5 various forms of, 84 of the ihird kind, 6 safe use of, 84 Giavesende's, 6 prices of, 85 for suspension, 3 Pipette toys, 87 •with solid fulcrum, 2 Plants, air extricated from, 147 varieties of, 4 Plumb-line, 16 Lift pump, 94, 95, 96 Pneumatics, in Linear measures, inches, 36 Porous evaporating-basins, 152 centimetres, 36 Pressure of fluids proportionate to Lock and key, 3 1 depth, 83 Lungs glass, 146 Pressure of the air, 154 Pressure of water in all directiuns. Magdeburg hemispheres, i6r 41, 45, 47 Magic bottle, 158 Prince Rupert's drops, 31 can, 88 Pulley, 7 Mariotte's apparatus, for showing the simple, 7 compressibility and elasticity of fixed, 7 air, 167 moveable, 7 constructed to show that, under the Pulley frame, 7, 10 pressure of two hemispheres. Pulleys, set of, wood, 7 air is compressed into half its set of, brass, 10 ordinary bulk, 1 70 system of, 8 and that under the pressure of concentric, 10 half an atmosphere it expands long three-sheave, 8 to twice its ordinary volume, 1 71 square three-sheave, 10 Mechanical powers, i Pumps, Water-, 94 small set in box, 13 cause of the rise of water in, 47, 97 Mechanics, i lift-pump, glass, 94 Meicury, shower of, 155 brass mounts, 96 Mohr's hydrostatic balance, 69 Tate's school pattern, 97 Mysterious funnel, 87 force-pump, glass, 94 larger, 95. Nicholson's hydrometer, 72 double action, glass, 95 melal, 95 Oblique cylinder, 14 brats mounted, 96 Cptic marvel, 26 mahogany stand for, 9 7 Osmometer, 31 Overshot water-wheel, 108 Eeoeiversfor air-pumps, 172 Eegnault's specific gravity bottle, 65 Pair of narrow bottles for transfer of Eesistance of air, 156 air, 145 Rotating apparatus, 27 Pan and peas, 16 Rupert's drops, 31 Pans, 178 Parallel motion, 29 Saccharometer, 79 I'arallelogram offerees, 18 Scale pans, 2 Parallelopipeds, 14 Scale pipettes, 86 Pascal's hydrostatic apparatus, 53 Schoolroom blackboard, i Pendulum, 16 Screws 13 Pereus.-ion machine, 19 Semicircle of brass, to show centre of Phial of the four elements, 43 gravity, 14 Philosopliical hammer, 141 Shower of air, 155 Pipettes, 83 Simple pulley, 7 bulb, 86 Single transfer plate, 133 ecale, 86 in use, 102 INDEX. 185 Sliding rod ia stuffing-box, 133 Smoke jacks, 150 Specific gravity, principle of, 5 7 experimental illustrations, 59 difference in liquids, 58 in solids, 5 8 of solids and liquids, method of estimating, 61 of solids, determined by tlie hy- drostatic balance, 61 of liquids, determined by the hy- drostatic balance, 62 of a solid, determined by weigh- ing it in a bottle, 62 of a liquid determined by weigh- ing it in a bottle, 63 bottles for solid bodies, 6 2 for liquids, 63, 65 bottles, on the choice and use of, 67 various forma of, 65, 66. Specific gravity of a liquid estimated by weighing in a balance a quan- tity first measured by a pipette, 69 Specific gravity of a solid estimated by measuring the water it displaces, 71 Specific gravity of a liquid estimated by means of the hydrometer, 73 Specific gravity of gases, 136 Specific gravity, table to facilitate calculations, 68 Spirit level, 39 Spouting jars for illustrating Torri- celli's theorem, 83 Springs and fountains, classification of, 97. Stability and instability of floiiting bodies, 80 Stopcocks, pneumatic, 130 Suspension board, i Syphon, 89 various forms of, 89 principle of action-, 90 use in fitting complex forms of che- mical apparatus, 91 Syphon barometer, 166 Syphm fountain, 105 Syphon gauges, powers of, 112 various forms of, 129 Syphon toys, 92 Syringes for air, 127, 128 for water, 93 Syringe and lead weight, 158 Systems of pulleys, 7, 8, 10 Tall cylindrical receivers, 177 TiiU plain jars, 177 Tallow holder, 135 Tantalus's cup, 92 Taper stand, r48 Three-globe apparatus, 159 Tilt hammer, 50 Top of tops, 28 Torricellian experiment, 163 Torrioelli's theorem, 83 Tourniquet hydrauhque, 48 Toys founded on pipettes, 87, 158 founded on syphons, 92 to illustrate adhesion, 19 Train of wheels, 29 Transfer plates, single, 133 double, 734 Undershot water-wheel, io3 Universal joint, 30 Upward pL'esaure of the air, 157 Upward pressure of water, 48, 49 Valves, 9; butterfly valve, 96 bellows valve, 96 round spring valve, 96 coniciil valve, 96 oil silk valve, 96 Velocity of falling bodies, 20 Vernier, 3 2 Vibrating wire, 28 Volumetric analysis, 83 Washers, 132 Water, ditficulty of freeing it from air. 142 falls solid in vacuo, r4r freezing it in vacuo, 152 pressure in all directions, 44 lateral piessure, 47 upward pressure, 48, 49 pressure proportionate to depth, 83 pressure on the two ends of a cone, 57 incompressibility, 46 weighed in a vessel with a loose bottom, 55 rises to a level in communicating vessels, 137 to colour blue, 38 to colour red, 38 Water hammer, straight, 141 V-fonued, 141 fork-formed, 142 186 INDEX. Water-pumps, 94 AVater-wlieels, 108 "Waterworka, 108 Wedge, II Weiglits, 34 for levers and pulleys, 2 grain weights, accurate, 34 grain weights, not adjusted, 34 pound pile, brass, 34 cast-iron, 34 Centigrade, 35 Wheel and axle, 11 compound, 12 Whirling table, 22 adjuncts for twelve experiments, 23 White's concentric pulley, 10 Windmill, 143 Wire cage for breaking squares, 150 Wire gauze capsule, 82 Wooden balls to show capillary ac- tion, 82 Wurfcemberg syphon, 91, 93 THE END. LOKDOH : FEINTED BY WILLIiM CLOWES AND SONS, STAMFORD STREET, AND CHARIKG CROSS. SCIENTIFIC BOOKS AND CATALOGUES PUBLISHED BY JOHN J. GKIFFIN & SONS, 22, GARRICK STREET, LONDON, W.C. CATALOGUE OF SCIENTIFIC APPARATUS for USE in SCHOOLS: Comprehending Instruments required for Performing Experiments to illustrate the following Sciences : Mechanics, Hydrostatics, Hydraulics, Pneumatics, Acoustics, Meteorology, Heat, Lii;ht, Electricity, Magnetism, Galvanism, Electro-magnetism, Chemistry, Geology, Crystallography, Mathematics. 56 pages, demy 8vo. Price M. post free. STUDIES IN CHEMICAL PHILOSOPHY, Embracing Discussions respecting the Constitution.s of Acids, Bases, and Salts ; the Atomic Weights, the Radical Theory, the Constitution of Gases, the Construction of Chemical Formulse, the Principles of Chemical Nomenclature, the Doctrine of Types and Substitutions, Special Account of the Constitution of most of the important Varie- ties of Salts, &c. &o. &c. By John J. Gkiffin, P.C.S. Crown 8vo., 558 pages. Price 5s., oloth. ECONOMY IN SUGAR MAKING. Directions for Testing Cane Juice, so as to determine the exact quantity of Quicklime required to temper the juice. 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Air, Water, the Gases, the Acids, and a Summary of Organic Chemistry ; including an extensive Course of CLASS EXPERI- MENTS, with Instructions for their successful performance, illustrated by 440 Engravings of the most efficient Apparatus. Contents of the SEOOITD DITISION of OHEMIOAL KEOEEATIOITS. The Eadical Theory : — 1. Oxygen. 2, Hydrogen. Compounds with Oxygen. 3. Nitrogen. Compounds with Oxygen and Hydrogen. 4. Carbon. Compounds of Carbon with Oxygen and Hydrogen. Organic Compounds. Salts produced by Organic Radicals. Special examples of Organic Salts. (_)rganio Compounds that contain Nitro- gen. Combustion, Fuel, lUumination, Fusion. Gas Furnaces. 5. Sulphur and its Salts. 6. Selenium. 7, 8. Tellurium. 9. Plios- phorus. 10, 11. Arsenic. 12, 13. Antimony. 14. Chlorine. 15. Bromine. 16. Iodine. 17. Fluorine. 18. Boron. 19. Sih'con. 20, 21. Chromium. 22, 23. Molybdenum. 24, 25. Vanadium. 26. Tungstenum. 27. Titanium. 28. Tantalum, 29. Pelopium. 30. Niobium. The "Work complete, in One Volume, clotli gilt, 12s. 6d. JOHN J. GEIFFIN & SONS, 22, Gaerick Street, W.C. 2 SCIENTIFIC WOBKS hy JOHN J. GBIFFIN, F.C.S. CHEMICAL HANDICRAFT: A CLASSIFIED AND DESCRIPTIVE CATALOGUE OF CHEMICAL APPARATUS, Suitable for the performance of Class Experiments, for every Process of Chemical Research, and for Chemical Testing in the Arts. Accompanied by copious JSTutes, explanatory of the Construction and Use of the Apparatus. By JOHN J. GEIFFIN, F.C.S. In One Large Volume. Svo„ o/472jpp., Illustrated hy Sixteen Hundred Engravings on Wood. Price 4s., cloth, CONTENTS. Apparatus for Mechanical Operations : Hammers, Mortars, Glass-blowing Apparatus, Supply of Water, &c. Supports for Apparatus, of iron, wood, &c. Weighing and Measuring. Apparatus for determining the Specific Gravity of Liquids: Hydrometers, Alcoholometers, Saccharometers, Urinometers, Specific Gravity Bottles, &c. 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Analytical Operations : Application of Chemical Tests, Testing Apparatus, Chemical Tests in solution of graduated strength. Volumetric Analysis: Weights and Measures used. Apparatus: Burettes, Supports for Burettes, Pipettes, Measuring Flasks, Test Mixers, Mixing Jars, Indic-ators. Special Volumetric Operations. Testing of Carbonates, Chlorides and Iron Salts, Water Test, Assay of Milk, Wine Testing, Sugar-cane Juice Testing, Assay of Zinc Ores, Sets of Apparatus and Test Liquors for Volumetric Analysis. Volumetric Solutions on various standards : the Septem, the Cent. Cube, and the Decem. Urinometry : Sets of Instruments and Tests for the Assay of Urine. Blowpipe Apparatus and Apparatus for Microchemical Operations. Apparatus for Experi- ments on Coloured Flames. The Spectroscope. Cabinets of Blowpipe Apparatus both for qualitative and quantitative Analysis. Apparatus for Assaying, and for Metallurgic Operations in general. Marsh's Arsenic Test. Organic Analysis. Collections of Chemical Apparatus arranged for special purposes : some in portable Cabinets. Specimens of Minerals, illustrative of Mineralogy, Geology, and Metallurgy. Crystallography: Collections of Crystal Models. Chemical Books. List of Chemicals, Acids for Exportation, With all other Requisites for Experi- ments of Demonstration or Research. JOHN J. GEIFFIN & SONS, 22, Gaerick Street, W.C. 3 SCIENTIFIC WOBKS hy JOHN J. GBIFFIN, F.C.S. POPULAR GUIDE TO CRYSTALLOGRAPHY. In demy 8vo., pp. 520, with numerous Figures, price 5s., A SYSTEM OF CRYSTALLOGRAPHY, WITH ITS APPLICATION TO MINERALOGY. By John Joseph Griffin, F.C.S. This is the only English work in which the mathematical rules for the examination and description of Crystals are ex- pressed in words at length, as well as in algebraic lormulse ; and it contains the only English Catalogue of the Forms and Combi- nations presented by the discovered Crystals of each species of Mineral, CONTENTS. Pakt I. PEIN0IPLE3 OF Crtstallogravht : — 1. Axes of Crystals. 2. Planes of Crystals. 3. Prisms and Pyramids, and tlieir Combinations with one another. 4. Classification of Crystals. 5. Possible limit to the number of Planes that can occur upon Crystals. 6. Ciystallographic Notation. 7. Cleavage and Primitive Forms. H. Forms and Combinations. 9. The Five Zones. 10. Law of Symmetry. 11. Theory of Crystallisation. 12. Use of Spherical Trigonometry io Crystallisation, explained in a popular manner. 13. Inquiry into the variety of Forms and Combinations that occur upon the Crystals of Minerals. Explanation of the Six Systems of CryttiiUisation:— (1) The Octahedral System ; (2) The Pyramidal System ; (3) The Ehombohedral System ; (4) The Prismatic System ; (5) The Oblique Prismatic Syste}u ; (6) The Doubly-oblique Prismatic System. 14. Brooke's System of Crystallo- graphy. 15. Considerations on the utmost possible Abridgment of Crystallo- grapMc Notation. 16. Table of Sines and Tangents. Part II. Appuoation of Crystallography to Mineralogy : — 1. Eose's Tabular Arrangement of known Crystallised Minerals, according to Six Systems of Crystallisation. 2. Catalogue of Crystallised Minerals, showing the Combinations that occur in Nature. 3. Systematic arrangement of the Crystals found in the Mineral Kingdom, with a Li^t of the Minerals common to" each Crystal, with an explanation of the.Mineralogical Characters employed to dis- criminate the Minerals that Crystallise in the same Form. 4. Descriptive Catalogue of a Series of 120 Models of Crystals employed to illustrate this system of Crystallography. MODELS OP CRYSTALS: a Series of 120 Models of Crystals, executed in Biscuit Porcelain, size from 2 to 4 inches in leni'th most of them representing Crystals that occur among Minerals, and' adapted to facilitate the study of Cry&tallographic Science. Frice of the Set of 120 Models, 42s. JOHN J. GRIFFIN & SONS, 22, Garrick Street, W.C. 4 SCIENTIFIC WOBES hy JOHN J. GRIFFIN, F.C.S. THE CHEMICAL TESTING OF WINES AND SPIRITS. Bt JOHN JOSEPH GRIFFIN, FiC.S. In One Volume, Grown 8vo., Illustrated by numerous Woodcuts. Second Edition, Revised. Price 5s. CONTENTS. Analysis of 41 Wines by the processes described in this work. Table of the weight in grains of the constituents of a gallon of each Wine. Table of the percentages of the same constituents. Determination of the specifio gravity of Wines and Spirits. Alcohol Tables, an entii-ely new series, founded on the latest analytical investigations. Table of diluted Spirits of from to 12 per cent, of absolute Alcohol by weight, showing, 1, Percentage of Alcohol ; 2, Specific Gravity ; 3, Weight of a centigallon of the mixture ; 4, Weight of absulute Alcohol ; 5, Weight of Proof Spirit; 6, Percentage accordmg to Sikes. Table of Diluted Alcohols from to 100 per cent, by weight, with similar details in six columns. Table of Percentages of Alcohol by volume, according to Tralles and Gay-Lussac, compared with pircentage of Proof Spirit, accordmg to Sikes. Harmony of these various Alcoholometers. Table for the dilution of Spirits, and for the valuation of Proof Spirits according to Sikes. Series of Problems for calculations respecting Alcohol. Corrections for temperature required by experiments made with Alooliol. Experimental Determination of the quantity of Alcohol in Wines. Experi- mental Determination of the quantity of Free Acid in Wines. Investigation of the best means of separating volatile from fixed Acids in Wines. Experi- mental Determination of the quantity of Sugar in Wines. Process for the separate estimation of Grape Sugar and Cane Sugar. Determination of the amount of Solid Eesidue left when Wines are evaporated to dryness at 230° Fahr. Determination of the quantity of Ash, or incombustible substances in Wines. Determination of the qua,ntity of Eree Alkali cont.iined ia the Ash of Wines. Estimate of the neutral Organic bodies contained in Wines. Programme of a Wine Analysis according to the methods described in this work. Mutual relations of the Constituents of Wines. Conclusions respecting the propoitiona in which Alcohol, Acid, and Sugar ouglit to exist with one another to form good Wines. Testing of Spirits. Chemical notes on some special points in the manufacture of Wines. Testing of JIust in good seasons and in bad seasons. Correction of Acid Must in. bad seasons to render it fit to make good Wine Preparation of good Wines from unripe Grapes. Wine- making without Grape-juice. Quick process for Maiming Wines. Blendino- and fortifying of Wines and Spir-its. Import duty on Wines. CHEMICAL APPARATUS and TEST LiaUORS for analysing Wines by the rapid and easy methods described in this work, supplied complete with Balance and Grain Weights. Price £9 9s. The same collection without Balance and Grain Weights. Price £6 Gs. JOHN J, GEIFFIN & SONS, 22, Gaebick Street, W.C. 5 SCIENTIFIC WORKS by JOHN J. GBIFFIN, F.C.S. CATALOGUES OF SCIENTIFIC APPARATUS. 1. CABINETS and COLLECTIONS of CHEMICAL APPARATUS and TESTS, suitable for the Private Study of Ele- mentary Chemistry, for Students in Chemical Schools, for Qualitative Analysis, for the Illustration of Chemical Lectures, for Travelling Mineralogists, Metallurgists, and Engineers, for Toxicology, Urino- metry, and other Medical Purposes; for Agricultural Chemists, and other special experimental purposes. Arranged by John J. Gkiffin, F.C.S. [Extracted from "Chemical Handicraft."] 40 pages, 8vo., sewed, price M., post free. 2. APPARATUS for the PRODUCTION and APPLI- CATION of HEAT by means of Furnaces, Lamps, and Gas-burners, and Fittings suitable for the various Chemical Processes of Evapora- tion, Drying, Ignition, Fusion, &c. 80 pages, 8vo., illustrated by 300 vpoodcuts, price Is., post-free. 3. ILLUSTRATED CATALOGUE of CHEMICAL AP- PARATUS, suitable for the Private Study of the Science, for Lectures and Class Teaching, and for Analytical Investigations. [A select List from the " Chemical Handicraft."] 64 pages, demy 8vo., with 230 woodcuts, price Is., post-free. 4. MAGIC LANTERNS, Apparatus for Dissolving "Views, and first-class Sliders, in great variety ; witb copious Lists of sets of Sliders, and full Instructions for the Use of the Apparatus. 32 pages, 4to., with 14 woodcuts, price 3d., post-free. 5. ACCOUNT of a GAS FURNACE, suitable for Ctemical Fusions at a White Heat, and Assaying Operations by tbe Muffle without the aid of a Blowing Machine. Price Id., post-free. 6. LIST OF PURE CHEMICAL TESTS, and otber Chemical Preparations for Experiments of Demonstration or Re- search. Price Id., post-free. JOHN J. GEI-FriN & SONS, 22, Gareick Street, W.C. 6