DIRECTIONS 
 
 FOR THE 
 
 TEACHING OF GEOLOGY: 
 
 A MANUAL FOR THE TEACHER, TO ACCOMPANY 
 “THE FIRST BOOK IN GEOLOGY.” 
 
 BY 
 
 N. S. SHALER, S.D., 
 
 PROFESSOR OF PALZONTOLOGY IN HARVARD UNIVERSITY. 
 
 BOSTON: 
 PUBLISHED BY D. C. HEATH & CO. 
 LSo7. 
 
Entered, according to Act of Congress, in the yeal 
 
 N. 8, SHALER, 
 im the Office of the Librarian of Congress ac Washing 
 
DIRECTIONS TO TEACHERS. 
 INTRODUCTION. 
 
 © A preparing the set of text-books of geology of which 
 aw this primer constitutes the first volume, I have been 
 .. guided by my experience in teaching the subject, gained 
 i in about twenty years’ work with individual students and 
 ~~ classes as well as by a careful inquiry into the methods 
 ‘, followed in such work by the teachers of this and other 
 countries. ‘This practical experience has included work 
 ~ with students of all grades, but principally with beginners 
 , iy. the science, of more mature years than those for whom 
 4 this primer is designed. I have, however, been able to 
 ¢ test the method with young children of ten or twelve 
 ? years of age, and am satisfied that there is no difficulty in 
 ~ making use of it even with younger persons. 
 r ‘Everyone who has had experience in the teaching of 
 * nature to children has seen how eagerly they accept any 
 e natural contact with the physical world. All that is to 
 be taken in through the senses is welcome to them. It 
 is only when we try to turn their attention to things that 
 are not to be touched or seen that the teacher’s task be- 
 comes difficult and the danger of inattention great. This 
 is the result of the order in which the faculties develop. 
 5 In that period of intellectual development which we may 
 cal mental infancy, the mind can properly do little more 
 than receive impressions, which are built into itself and 
 become a part of the consciousness. We must wait for 
 the second stage of development before the imagination 
 begins to use this meee for higher ends. Therefore 
 
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4 PRIMER OF GEOLOGY. 
 
 the aim of this primer is to secure a limited number of 
 memories, and these of things that may help the mind in 
 its later growth. 
 
 In trying to effect this result, I have felt it necessary to 
 rely upon the exertions of the teacher more than upon the 
 didactic part of the work itself. Were it not for my 
 belief that there exists a sufficiently devoted body of in- 
 structors to warrant this trust, I should not have under- 
 taken this series of text-books. For any competent in- 
 struction in science, we must expect far more from the 
 teacher than need be demanded from them in any other 
 branch of elementary education. In mathematics, in lit- 
 erature, in history, the current of life sets towards the 
 learning we seek to instil; moreover, the race has for 
 centuries been occupying itself with this class of ques- 
 tions, and they are no longer strange to the mind of man. 
 Science, however, is not yet a part of the common intellec- 
 tual heritage, and its ways, if they be true to its spirit, are 
 to a great extent different from those of, the humanities. 
 
 I would not have it thought that the teaching of science 
 even to the very young is a more painful task than the 
 teaching of the more common branches of education. On 
 the contrary, I am convinced that if it is rightly done, it 
 is more pleasant, even if more laborious, than any other 
 part of the teacher’s work. Nor would I have it believed, 
 as some men of science are inclined to claim, that science 
 may replace the other branches of education. I will not 
 enter on the broad field that opens to us when we en- 
 deavor to determine the place of science in a system: of 
 education, but I would like, in order that the motive 
 that has guided me may be plain, to state my firm convic- 
 tion that science cannot in any way replace the old edu- 
 cation. It must be added to it. And its good results can 
 
DIRECTIONS TO TEACHERS. 5 
 
 only be secured by the commingling of its teaching with 
 those branches of learning that have lifted the human 
 mind to its present level. 
 
 It seems to me very desirable that the first steps of the 
 child in the study of the physical world should be given 
 by teachers who give the beginnings of the other branches 
 of learning. Although it is held by some students of the 
 problem of science-teaching that the work must be done 
 by special teachers of science, I am inclined to believe 
 that the view is'a mistaken one. The well-trained teacher 
 in the humanities who knows something of science, and who 
 pursues the right methods, can blend science with the 
 other learning. The special teacher will have to divide 
 the intellectual life of the student, and in the infantile 
 stages of education it is difficult to make this division. 
 
 I have therefore assumed that those who make use of 
 these primers are persons of only a general acquaintance 
 with natural science, whose principal task is to teach the 
 subjects ordinarily taught to students of primary or sec- 
 ondary schools of the lower grade. I have therefore de- 
 termined to make a careful statement of the purposes of 
 this little book, and to accompany each lesson with a set 
 of directions which will make it possible for the teacher to 
 give the work the right turn for the students’ advantage. 
 
 It is of the utmost importance for the teacher to 
 notice that the science of geology, as well as astronomy, 
 ealls for certain conceptions of space and time that it is 
 not easy for the student to attain to. We see the magni- 
 tude of this difficulty in tracing the history of these 
 - sciences. It was long before man could accept the ideas 
 of distance and duration which are necessary in order to 
 grasp the merest outlines of these sciences. We cannot ° 
 hope to get these vast images into the minds of children, 
 
6 - PRIMER OF GEOLOGY. 
 
 yet some seed may be sown which in time will take root 
 and flourish. This task is the more difficult because the 
 whole course of our civilized life is away from such con- 
 ceptions. The savage gets in his wilderness life a sense 
 of distances and durations which our own life does not 
 give to us. Even in our teaching of history we do not 
 take pains to force the student to strive for the perspec- 
 tive the past should give, but let the historic pictures 
 stand more out of true proportion in the memory than 
 a Chinese landscape. As this power to conceive space- 
 relations must grow with all teaching of geology if the 
 instruction is to help the mental growth, I venture to give 
 special importance to it, and to set out the method by 
 which the student may be helped on his way. 
 
 In gaining the power to conceive the space that things 
 occupy, the child should, as soon as possible, be accus- 
 tomed to measure space with the simplest means. Some 
 unit of measure, by preference the yard or the metre, 
 should be hung in the schoolroom, or, better still, marked 
 on sticks with which the children take calisthenic exercise. 
 It will be well to write on the school wall, in a place 
 where the children’s eyes will often meet it, a diagram 
 showing the actual length of the metre, yard, rod, ete. 
 The aisle of the schoolroom may be marked into divisions 
 of metres by brass-headed tacks driven into the floor. 
 Thus the children will learn to perceive this unit in a 
 practical way. 
 
 The children, from about seven years old, should be 
 taught to draw proportionate horizontal planes of the 
 desks they use; then, of the schoolroom floor; next, of 
 the ground on which the schoolhouse stands. This work 
 should gradually be extended until the student can show 
 the general relation of all the ground he personally knows. 
 
DIRECTIONS TO TEACHERS. i 
 
 I have found this style of work, modified to suit the con- 
 ditions of the person, useful to students of all grades. 
 They gain thereby a power of conceiving space-relations, 
 without which all efforts towards the study of the earth 
 are in vain. This, as all other work that really develops 
 the mind, is welcomed by all wholesome-minded students. 
 It is not at all important that these drawings should have 
 any perfection of finish. It is doubtful if this quality in 
 such work is to be striven for among children. It is, how- 
 ever, essential that the sketch maps should be referred to 
 the main points of the compass, that they should be ap- 
 proximately proportionate, and that the student should 
 use some scale for his work. A yard measure does well 
 for buildings. For a larger field, such as a square mile or 
 two of country, the mile and its fractions are well suited. 
 The power of mentally grasping any considerable area 
 will not be found in small children. Indeed, there are many 
 educated people who cannot carry a square mile of the 
 earth’s surface in their imaginations. So this work must be 
 somewhat proportioned to the capacities of the individual 
 student. Iam inclined to believe, however, that the topo- 
 graphical sense is more general and more easily stimulated 
 to activity than any other intellectual power. The teacher 
 will see the profit of it to the child not only in the depart- 
 ment of physical science, but also in mathematics. The 
 science of relations depends upon a constructive imagina- 
 tion. The drawing of sketch maps stimulates this power 
 more than any other work I know. As soon as children 
 have gained a certain sense of the horizontal elements of 
 geography, they will be able to see the relation between 
 maps and the face of the earth, which is rarely established 
 in a child’s mind in our ordinary ways of teaching geog- 
 raphy. It will be found to help this work if the teacher 
 
8 PRIMER OF GEOLOGY. 
 
 will take pains to show the student a well-made map of 
 the region he has endeavored to delineate. An excellent 
 plan is to let a party of children be taken for a walk. 
 Their attention should be drawn to the shape of the 
 country, the direction of the streams and the woods, the 
 position of hills and important buildings. When they 
 return, they should be at once urged to make a plan of 
 the ground they have traversed. Interest will be given to 
 the work by allowing them to use crayons in making the 
 maps, using sky-blue for the streams and red for the 
 woods, while they show the position of the hills by some 
 simple hatchure lines. 
 
 The conception of height should ae if possible, be 
 given to students, but it is more difficult to give a simple 
 means of training the eye and mind in this than in hori- 
 zontal dimensions. It is important that something, how- 
 ever inadequate, should be done in the way of training in 
 this element of space-perceptions. It is best to begin with 
 small ranges of height, and then proceed gradually towards 
 more and more extended conceptions. ‘The height of the 
 schoolroom should be given as the first study, and the 
 lesson enforced by a diagram showing the relation of 
 length to height. If the wall contains any conspicuous 
 objects, such as diagrams or maps, these should be given. 
 Then an external plan of the building will furnish an ap- 
 propriate exercise. It will be found advantageous to rule 
 a scale of heights on the schoolroom wall. By ascertain- 
 ing the heights of some of the principal buildings or trees 
 in the immediate neighborhood of the school, the teacher 
 will be able to give the students some data for judging 
 elevations. If the country familiar to the child be of 
 irregular surface, excellent studies are sure to be at hand 
 on which the child can find exercise after the beginning 
 
DIRECTIONS TO TEACHERS. 9 
 
 is made. The vertical outline of a hill, with an estimate 
 of its height from objects upon it, is an excellent thing 
 for training the eye. Also, the task of drawing an out- 
 line of a wood, showing how it rises above and falls below 
 a horizontal line. Only at the last, if at all, should any 
 effort be made to represent hills by either hatchure lines 
 or by contour lines. This is the most difficult task of 
 delineation, and to bear the surface of a country so well 
 in mind that it can be thus given with any approxima- 
 tion to truth requires either more training than most 
 students can give to it or a more than ordinary topo- 
 graphical memory. If the training can be carried on for 
 some years, even if but an hour a week can be given to 
 it, students may be able to remember the shape of a con- 
 siderable surface of country. 
 
 Although it is often an agreeable exercise for the stu- 
 dent to make his drawings in the field, and there is no 
 objection to his doing something of this in time, yet at 
 the outset he should give only what he can bring to the 
 school in his memory. On this same account, in the first 
 stages of his work, the child should be urged to delineate 
 rooms that are not before the eye at the time when the 
 work is done. Even when this work must be begun by 
 the child drawing the figure of the wall in the next room, 
 and repeatedly going to the room to refresh the memory, 
 it will be well to take this simple step for a beginning. 
 It should be remembered that it is not so much the de- 
 lineative power that we are seeking to train, but the 
 power of creating an image of definite form in the mind 
 by an effort of memory. This is the first object. The 
 next is to secure the memory of the true proportions of 
 space, separating objects in nature and their relations in 
 space. The capacity of the hand to follow the eye in 
 
10 PRIMER OF GEOLOGY. 
 
 simple delineation, though in itself a worthy object of 
 training, is nothing like as important for the development 
 of the habit of mind necessary to a student of nature. 
 In fact, a very high degree of capacity of comprehension 
 may be attained without much development of the delinea- 
 tive power. ‘There are many very capable and philosophi- 
 cal naturalists that have very little capacity for delineation, 
 but I doubt if there are any that have not a considerable 
 sense of the spacial relations of things. 
 
 It need hardly be said, however, that the making of dia- 
 grams to show geographical relations is excellent exercise 
 in delineation, or, rather, in the training of the mind and 
 hand to co-operation. 
 
 Next in importance to this development of the sense of 
 distance and direction, I would place the training of the 
 habit of observation. It is a natural but most unhappy 
 misconception on the part of many who are seeking to 
 make science a part of education that it is the fact part 
 of science that is of value to the young mind. They think 
 that, if the student can only be possessed of all the body 
 of fact known to science, he would have a most precious 
 store. So far, the greater part of the efforts to teach 
 science have been made worse than worthless by this per- 
 nicious notion. 
 
 The truth is that the mere facts of science, important 
 as they may be in an economic sense, have very little 
 value as elements of education. They do not of them- 
 selves enter into the whole of human life as do the 
 facts of history or language. The fact that the trias pre- 
 cedes the jura in the geological succession is of no sort 
 of intellectual consequence to the student. It does not 
 link itself with human instincts as the fact that Constanti- 
 nople fell to the Turks in 1458, though in the whole of 
 
DIRECTIONS TO TEACHERS. iy! 
 
 nature it may be an even more momentous truth. It 
 seems to me that any considerate man must hold with me 
 that even if a person of marvellous memory should be 
 able to remember every ascertained fact in all the natural 
 sciences, he might, if his knowledge went no further, be 
 still an essentially uneducated man. He who should know 
 all the facts of man’s history would find that his own 
 humanity would necessarily produce a unity of under- 
 standing, and such a man would truly become ripe and 
 scholarly. But the mere facts of nature have no such 
 thread of human sympathy or other common level to give 
 them unity in the intelligence. These things science can 
 give the mind,—the sense of cause and consequence, 
 or what we call natural cause, properly taught, and the 
 power of independent inquiry into the truths of nature. 
 It cannot humanize the mind, and this humanization is 
 the first and principal work of education. In this last 
 gift, the power of independent inquiry, we find the benefi- 
 cent place of natural science in education. The greater 
 part of that which has to be given to students in educa- 
 tion must be given didactically. There can be in the 
 ordinary student’s work no independent inquiry into the 
 facts of history or of literature, and but little in the matter 
 of speech or of mathematics. He must open his mind 
 to receive, asking no other reason for the belief than 
 that those who are his masters bid him take it so. The 
 attitude of independent inquiry is hardly possible in any 
 of the most essential matters of education. Of course, 
 reasons are given for most things, but the student can 
 never, in the ordinary course of human life, stand fear- 
 lessly before the hidden truth and claim it as the prize of 
 his own skill or courage. In natural science, this indi- 
 vidual manner of acquaintance with nature is possible to 
 
12 PRIMER OF GEOLOGY. 
 
 all. Every student may then feel himself in the exalted 
 position of an independent inquirer, with no master be- 
 tween him and the eternal truth. 
 
 Only those who have in youth felt the great and enno- 
 bling stimulus that comes from this direct contact with 
 the truths of the physical world can know how full it is 
 of power for good. Once possess the mind of this habit, 
 and commonplace methods of inquiry are ever afterwards 
 stale. If there be any natural strength in him, the stu- 
 dent will do better work in all the fields of activity for 
 the strength he acquires in his wrestle with nature. The 
 training in observation that children require is easily 
 given by any one in the least degree in sympathy with 
 the work. We may at the outset rely upon the instinc- 
 tive desire to know which is the strongest mental work 
 of childhood. ‘This curiosity concerning the external 
 world is generally an inconvenience to the older members 
 of the race, and so a desire as natural as hunger, and 
 which if gratified would serve to build and strengthen 
 the mind, becomes vitiated by time and dulled by want 
 of use. Our whole method of didactic teaching neces- 
 sarily works against this instinctive desire to know. 
 The child is led by his nature to a love of the outer 
 world, the actual graspable, seeable world. We turn him 
 to abstractions, so that his mind is palled with things for 
 which he has no appetite. I do not mean to object to 
 didactic methods. Education cannot be effectual without 
 such methods of instruction, and the habit of taking 
 knowledge in this way must be impressed upon the mind 
 in early youth. But the mind should have its share of 
 exercise in the other fashion, the fashion in which the 
 child’s nature most clearly invites it. 
 
 The difficulty of giving any training in observation in 
 
DIRECTIONS TO TEACHERS. 13 
 
 the classes of our ordinary schools is undoubtedly very 
 great. At one time it seemed to me so great that I de- 
 spaired of any success in the effort to attain it. Of late I 
 have become.more hopeful about the matter, principally 
 because I have seen the profitable results of very simple 
 but well-directed labor on the part of several teachers 
 working with students of various ages. 
 
 The method of working must be left in the main to the 
 teacher. So much depends upon the circumstances of 
 each school that it is impossible to devise a system that 
 shall be applicable to all cases. One of the conspicuous 
 advantages derived from the training in the perceptions 
 of space relations above described is that, besides the spe- 
 cial end in view, it lays the foundations of the observa- 
 tional habit. When nothing else can be done, much can 
 be accomplished by extending and elaborating this sort of 
 work. | 
 
 When schools are situated in close-built cities, and there 
 is no contact with the open fields, it will generally be 
 necessary to limit observation to the following matters. 
 The students may be induced to grow certain plants and 
 to observe the simple processes of development. Any 
 window-sill, with two or three pints of earth in vessels of 
 any description, or a jar of water in a warm room, will tell 
 them some of the most fascinating truths concerning the 
 physiology of plants. The teacher, by possessing himself 
 of Dr. Gray’s admirable little book, entitled ““ How Plants 
 Grow,” will be able to guide the experiments to success, 
 and to make an intellectual use of the results, even though 
 he has never before given any attention to botany. 
 
 There are certain advantages in beginning the training 
 of students in observation in organic forms, living things 
 especially. Animals have an immediate interest to chil- 
 
14 PRIMER OF GEOLOGY. 
 
 dren that inorganic nature does not possess. The life that 
 is in plants and animals excites a more vigorous curiosity 
 than the physical machinery of the world can ever do. 
 
 In this style of science teaching, or at the very outset 
 of the work, it is well to make of avail the interest of 
 accumulation that possesses all children. They may ad- 
 vantageously be taught to collect plants and dry them, or 
 to make small collections of insects. This work should 
 not be allowed to descend to mere gathering of things 
 together, but it should lead to a beginning in classifica- 
 tion. The child should find out such essential differences 
 as those between butterflies and moths, or at least between 
 the several principal orders of insects. The little collec- 
 tion of natural objects which is designed to accompany 
 this series of text-books will show the essential nature of 
 these differences, but the actual seeing that teaches the 
 child should come through its own eyes, with the least 
 possible help from the teacher. When it comes to the © 
 wider and more varied seeing that is essential in the study 
 of geology, the work has to be varied very much, accord- 
 ing to the particular circumstances under which it is 
 carried on. If the teaching is done in large cities, 
 where the child can never have access to the face of 
 nature, the work will have to be limited. Still the 
 child can be shown the action of frost and rain; the 
 buildings will show considerable variety of stones; and 
 museums, that are hardly wanting in any large cities, will 
 show them a great range of minerals, rocks, and fossils. 
 There is pretty sure to be a river or a bit of seashore near 
 by from which the eye can take in some of the little prob- 
 lems suggested in the list at the end of this essay. If 
 a fair museum of natural history be accessible to students, 
 they should be urged to compare their collections with 
 
DIRECTIONS TO TEACHERS. 15 
 
 the specimens there shown, as far as it may be possible for 
 them to do so. 
 
 One of the most interesting amusements that can be 
 suggested to children is the gathering of insects, in the 
 pupa state, and the watching for their full development. 
 I know of few things more calculated to assure a lively 
 curiosity in their minds and to open to them a delightful 
 sense of the wonderful in nature. In the science of ge- 
 ology, the work must be adapted to the ground. Where 
 fossils occur, they afford the readiest road to the interest 
 of the student. We may be certain that the least trace 
 of distinct organic remains in the rocks will excite the 
 imagination of any child who is capable of feeling an in- 
 terest in the phenomena of nature. There is a mystery 
 about these remains of other days that is sure to awaken 
 at times a lively interest in minds which cannot be brought 
 to feel a keen interest in living animals. It is the case in 
 the history of geology, where men, whose curiosity con- 
 cerning the earth was not awakened by the lofty moun- 
 tains, by the earthquake or the volcano, were driven to 
 use their wits to solve the mystery of fossils. Fortunately, 
 a very large part of the teachers of this country will 
 find themselves near deposits containing organic remains. 
 Outside of New England, there are few schools three 
 miles away from deposits containing interesting fossils. 
 The teacher will do well to make himself acquainted with 
 these localities, that he may direct the attention of stu- 
 dents to them. When fossils fail, there are always inter- 
 esting minerals, and then, as over the greater part of the 
 Northern States, there is usually also an abundance of 
 glacial pebbles. After children have been told something 
 about the last glacial period, they may advantageously be 
 urged to make collections of these pebbles, to show the 
 
16 PRIMER OF GEOLOGY. 
 
 variety of materials of which they are composed, their 
 scratching, etc. I have more than once found young 
 people in New England who became readily intenested in 
 observations of this simple sort. 
 
 When the circumstances favor it, I strongly recommend 
 the study of the banks of a river. On a short excursion 
 it is almost always possible to show the children how a 
 river works ; how it carries along sand and gravel when it 
 moves with moderate speed, or only mud when it flows 
 slowly. The constant going of its current, now cutting 
 away on one side, and filling in on the other, can also be 
 shown, and perhaps the fossils laid down when the stream 
 was at a higher level than it is at present. 
 
 If the teacher is near the seacoast, it cannot be too 
 strongly urged that the students should at least once see 
 the phenomena of the shore. ‘There is nothing else in 
 nature that can do so much to stir the mind and force it 
 towards broad conceptions of nature as a look upon this, 
 the most wonderful aspect of the earth. The sea and 
 the river are the best means of carrying to the child a 
 sense of the essential mystery of the earth which the 
 work of our modern life hides from us. The teacher 
 will find in some cases the world and all its beauty are 
 hidden from the child by the density of that veil of the 
 commonplace, which is really lifted to but few mortals. 
 It is not desirable that the child should feel too keenly 
 the true awfulness of the material world; but, if a child is 
 possessed by the distressing ennui that wraps some mis- 
 trained minds, resort must be had to these grander aspects 
 of nature, which often have a strong quickening power. 
 I venture also to suggest the use of certain descriptions of 
 natural scenery, of the habits of animals, etc., in the reading 
 classes of the school. Something of these are to be found 
 
DIRECTIONS TO TEACHERS. 17 
 
 in the ordinary school-books, but in the appended list a 
 better selection is made. ‘This part of the work may 
 easily be overdone, and it is somewhat apart from the end 
 I have in view, which is rather to secure the personal ac- 
 tivity than the passive acceptance of the student. 
 
 Much has been said by writers on education concerning 
 the use of instruction in drawing to enforce the habit of 
 observation, and by some a great deal is expected from it. 
 I have had much experience in the use of this method of 
 instruction, and have been driven to the conclusion that 
 mere delineation does not do much to awaken the mind 
 to a perception of nature. 
 
 Limited to the task of transferring the form of natural 
 objects to the picture, the mind acquires the power of 
 seeing the facts without any effort of the reason or the 
 imagination to interpret them. One fact of form or 
 color after the other is apprehended and transferred to 
 the sketch, but the mind acquires the habit of dismissing 
 the observation as soon as made. The questioning spirit 
 is not awakened, and the principal aim of all science 
 teaching should be to arouse this spirit and train it to a 
 fit activity. Drawing is an excellent means of developing 
 the faculty of attention until it becomes automatic, when 
 the subsequent exercise of it without other mental stimu- 
 lus is calculated to breed habits opposed to the spirit of 
 inquiry. 
 
 Much better fitted to the use of a well-devised teaching 
 system is the habit of delineation by words. Speech, even 
 when written, has a tendency, which drawing has not, to 
 arouse all the faculties of the mind. If a child can be 
 ' brought to writing descriptions of objects, it will be forced 
 thereby to see and to understand. Written statements are 
 _ better than verbal, for the reason that the child is compelled 
 
18 PRIMER OF GEOLOGY. 
 
 to remember and compare its statements in a more com- . 
 plete way than is possible in spoken words. The two 
 methods are, however, susceptible of being combined. 
 
 One of the best methods I have ever found of beginning 
 the work of the student, is to require him to describe, with 
 the thing before him, some simple creature, such as a house 
 fly, or a bee, that he has captured and imprisoned under a 
 bell-glass. The first questions should be of the simplest 
 sort, —how the creature walks, how many legs it has, 
 how it flies, the number of its wings, how it breathes, etc. 
 Then, when the evident external features of the insect 
 have been perceived and noted down, another insect, such 
 as a grasshopper, should be placed under the bell-glass 
 along with the first object, and a comparison between the 
 two should be made. The number of the wings will be 
 found to be different. Though the legs are the same in 
 number, the way in which they are used is very different. 
 Next, a beetle may be added to the collection, with the 
 same set of questions to be answered. Then a spider 
 may be taken in the same way. The points of difference 
 between the second two insects and the spider will be 
 easily seen, and scarcely ever fail to arouse in the student, 
 as no words can do, a sense of the diversities and relations 
 that exist in nature. 
 
 In the department of geology I can recommend, that 
 when it is possible for the student to make a little sketch 
 map of any district, however simple the sketch may be, 
 he be encouraged to note the kind of rocks or fossils or 
 pebbles he finds at particular points on the surface and to 
 mark where there are woods, and where springs. ‘The 
 nature of soil may also be noted,— where the soil is deep, 
 where thin, where clayey, where sandy, ete. Of course, 
 this work has to be adapted to the age of the child; but 
 
DIRECTIONS TO TEACHERS. 19 
 
 children of from ten to thirteen years or thereabouts can 
 do all this with very little help from the teacher. If there 
 are any maps of the vicinity, it is an excellent plan, though 
 not always practicable, to give them a copy of the map, on 
 which they may lay down the things they can find out. 
 
 It will add to the interest of this work if the teacher 
 knows something of botany, and can teach the children 
 the difference between the principal kinds of trees and 
 lesser plants. Forest trees always vary very much in 
 different parts of a field, and the child will get valuable 
 impressions from such observations. I may remark, in 
 passing, that forest trees afford an admirable field for 
 training the observational power. Our American woods 
 commonly contain from twelve to twenty species of trees, 
 excluding the willows, which are hard to separate into 
 species. In a single season a child will learn to distinguish 
 the more evident species of trees, and so obtain an excel- 
 lent training of the power of observation. The mass and 
 dignity of a forest tree makes it a matter of more interest 
 to a child than the lesser plants. 
 
 If there are quarries within reach of the school, the 
 student can be advantageously occupied with them. The 
 elements of human interest that the work going on in 
 the quarry lends to the questions it illustrates will aid the 
 teacher in exciting the attention of the student. These 
 quarries will always show a variety of mineral substances, 
 and perhaps fossils as well. They will, in most cases, 
 show something of bedding in the rocks, and always some- 
 thing of joint structure. In many cases there will be dykes 
 and veins that illustrate the facts described in the primer. 
 
 Every chance opening beneath the surface of the earth 
 will exhibit something of interest to the student. Any 
 cellar-pit is certain to show the varying character of the 
 
20 PRIMER OF GEOLOGY. 
 
 soil, — how on the surface it is blackened by the vegetable 
 mould, how this blackening caused by the humus fades 
 out as we go downwards, until in the subsoil we come to 
 where roots do not penetrate. If the opening reaches to 
 the rock, and be not in a soil made by the glacial period, it 
 will show how the rock, by its decay, gives the materials 
 whence the soil is made, so that, while it is always washing 
 away on the surface, it is continually renewing below. 
 
 At a later stage in the progress of the investigative 
 habit, the teacher may aid the student to place signs upon 
 his map to show the outlines of certain kinds of rock. 
 
 A very useful exercise, but one that demands more aid 
 from the teacher than any of those which have already 
 been suggested, is to have the student make an ideal sec- 
 tion through the country in the fashion indicated by the 
 diagrams in the text-book. ‘This work is, of all a student 
 in geology can do, the best fitted to develop that combi- 
 nation of the imagination and the reason which character- 
 izes the better class of scientific minds. When the geo- 
 logical conditions are simple, the teacher can readily learn 
 to do this class of work with sufficient skill to be very 
 helpful to the student. I do not venture, however, to 
 advise an early resort to this sort of work, as it is fit 
 rather for those of maturer age than for those who are 
 just beginning the study of nature. 
 
 The foregoing pages are intended rather to give the 
 teacher a general idea of the means whereby the student 
 may advantageously be led to a study of nature than 
 to set up a determined scheme to be pursued in all 
 eases. After all, in this, as well as in all other forms of 
 teaching, the spirit must come to the child through the 
 personal skill of the instructor. I believe, however, that — 
 any intelligent teacher, even if quite without training in 
 
DIRECTIONS TO TEACHERS. yi | 
 
 natural science, will find it possible to apply many of 
 these suggestions to great advantage. There is no means 
 of finding the way into any field of learning like pre- 
 paring one’s self to teach the elements thereof. While 
 the best teacher of the elements of a subject is the perfect 
 master of that subject, who at the same time loves his 
 work, the next best instructor is the skilful beginner, 
 who, with a mind trained in other fields of learning, can 
 readily keep ahead of his less skilful pupils. He will 
 make mistakes, but the leadership he gives is more per- 
 sonal and more familiar than that which is likely to come 
 from one who has come to feel somewhat fatigued by the 
 oft-trodden way. The study of nature is in no way a 
 mystery that requires of the novice a careful initiation. 
 Many of those naturalists who have had the most mental 
 profit from their pursuit have been entirely self-taught. 
 The work to be done demands only intelligence and an 
 interest in the matter. If, with these qualifications, the 
 teacher will but address himself to nature, and emanci- 
 pate himself from the authority of books until he begins 
 to see with his own powers, the end is easily attained. 
 This initial emancipation from books is necessary, and 
 is perhaps the only serious difficulty to be encountered 
 by any intelligent student in working his own way into 
 communication with nature. It is difficult because the 
 whole drift of our education is towards books. We take 
 all that is given by our ordinary system of education by 
 authority. The printed page is the gospel towards which 
 all faces turn. Nature does not speak directly to man, but 
 through its oracles the text-books. Now text-books are 
 fit and worthy means of teaching many subjects, but in 
 natural science, if used at all, they should have a very 
 subordinate place. They can serve only to do a secondary 
 
rye PRIMER OF GEOLOGY. 
 
 work. The principal part of it must be done by the 
 teacher, whose task should be to stimulate the minds of 
 his pupils to independent activity. He should use the 
 text-book to widen and strengthen the impressions that 
 have been gained by the actual contact of the child’s 
 mind with the problems, as they are expressed not by 
 words but by the face of nature itself. 
 
 In using this first book of geology, the teacher should 
 clearly understand the aim with which it is prepared. 
 This aim has been to secure to the student certain distinct 
 impressions of those facts in the history and economy of the 
 earth that can best be conveyed by words. The effort has 
 not been to go over the whole field of geology, but, on the 
 contrary, to select the crucial facts, and above all those 
 that were likely to be made familiar to the student by his 
 ordinary contacts with the world about him. If this little 
 book is used quite without reference to what is contained 
 in the companion volume, it will be found no worse than 
 an ordinary text-book. I believe it has an advantage over 
 any known to me in the fact that it does not confound the 
 student with the multitude of things, but gives those 
 things which he may reasonably understand at the outset 
 of his study of nature. If, however, the teacher will 
 make use of the suggestions contained in these parallel 
 notes, and will by words and by showing specimens, 
 pictures, and models expound and solidify the matter 
 of the text, then I believe that much more can be done 
 to stimulate the intelligence of the child than can be ac- 
 complished with any other system of text-books on this 
 subject. | 
 
 It is my hope that the teachers who use this first 
 book will endeavor to carry out the scheme of collateral 
 instruction suggested in the following parallel chapters. 
 
DIRECTIONS TO TEACHERS. 23 
 
 Each chapter of the book that is to be put into the 
 hands of students bears a number answering to one of 
 the following chapters. The intention of the chapters in 
 this book is to put the teacher in possession of the pur- 
 poses the writer has in each chapter, and to suggest illus- 
 trations from the neighborhood geology that cannot, of 
 course, be noted in the book itself. In many cases refer- 
 ences to other easily accessible books are given, so that 
 the teacher may consult authorities. In some cases a few 
 simple experiments, designed to show the phenomena that 
 are capable of illustration without special apparatus, are 
 given. 
 
 It must be noted that, in this first book, abstractions that 
 require special training or call for a large development of 
 the imagination are kept out of the text, though they are 
 sometimes recommended to be given by the teacher. The 
 reason for this is that statements of this kind are much 
 more easily conveyed by speech than by written words. 
 There is a flexibility, an element of mind awakening 
 sympathy in the words of a teacher that cannot be put 
 into a printed page. This it is that will always make the 
 personality of a teacher a necessary element in all com- 
 petent instruction. I find myself the more willing to try 
 this rather perplexing scheme of teaching, from the hope 
 that it may, in a measure, serve to give greater value to 
 our whole system of teaching by once again directing the 
 work of teaching in the true way. Whoever knows much 
 of our system of education knows that its greatest danger 
 arises from the effort to supplant the living mind of the 
 teacher by the dead language of the text-book. 
 
CHAPTER I. 
 THE ACTION OF WATER. 
 
 SRES object of this chapter is to bring the student into 
 contact with the forces of nature through the most 
 familiar facts that the world affords. In the work of water 
 the forces of the world appear in a more living shape than | 
 anywhere else. The presentation of the subject is begun 
 with the most simple of all the operations of water where 
 it acts through the rain. The restoring and destroying | 
 effects of rain are but briefly told. ‘The cutting power of 
 water may be illustrated in almost any region by hosts of 
 familiar examples. Wherever there is a stream, there will 
 be no lack of illustrations. Any gutter after a rain will 
 show the carriage of sand, the rolling of pebbles, ete. In 
 most regions, the tilled hillsides will show occasional 
 waterways cut in the soil. It will give reality to the car- 
 rying power of water if a tall jar is filled with water con- 
 taining fine clay, which is allowed slowly to subside. This 
 will show how the stuff carried down by rivers may jour- 
 ney far. A river in its time of flood is a most instructive 
 example of the power of water. The protecting effect of 
 vegetation can be shown by the difference in the color of 
 water that flows from a forest and that which comes from 
 tilled fields. 
 
 If there is a waterfall near by, the students should see 
 its action. There are sure to be pot-holes below it that 
 will prove interesting. It is likely also that the fall will 
 show evidence of gradually working up stream. This is 
 
THE ACTION OF WATER. 25 
 
 pretty certain to be the case if the fall is formed, as it is 
 at Niagara, by a hard, nearly horizontal structure of rock 
 overlying softer layers. 
 
 If the region is underlaid by limestone rock, as is the 
 case in a large part of America, there will be caverns 
 formed in it. These caverns will prove most interesting 
 to the student. ‘There is an atmosphere of mystery about 
 a cave that stimulates the mind and makes it quick to re- 
 celve any impressions. Large springs, if they exist, are 
 also things to be seen. The underground course of water 
 has a fascination to the mind that will help the teacher. 
 The sponge-like character of the soil, caused by the action 
 of the roots, should be dwelt upon; then the gathering of 
 the underground waters formed by the slopes of the rocks, 
 and finally the discharge at the surface. A simple experi- 
 ment by precipitating the lime contained in the water, or 
 boiling down the water for its sediment, will show that the 
 stream carries away some of the soil. It would be well to 
 boil down two little flasks of water,— one of pure rain 
 water, the other of spring water. The sediment in the 
 latter will show what goes away by the springs. It is 
 worth while, if the conditions are favorable, to show how 
 much water goes out from a single spring. This can be 
 reckoned by taking the size and speed of flow of the 
 stream from its course. 
 
 The phenomena of alluvial land can generally be illus- 
 trated along the banks of any stream. It can be shown 
 how the stream cuts off the curves, leaving ‘ oxbows,” or 
 ‘“moats,” as figured in the text. The student must be 
 made to see how the flood waters, when they escape into 
 the flats, lay down their sand and pebbles because their 
 currents are slackened. Lakes are hard to illustrate in 
 a clear fashion. If there are any large millponds acces- 
 
26 PRIMER OF GEOLOGY. 
 
 sible, the deposits on their bottom, or the greater purity 
 of the waters that escape from them over that of the 
 streams that enter there, may be used as an illustration of 
 the fact that lakes are settling reservoirs that catch the 
 waste of the land on its way to the sea. 
 
 Deltas can be shown on the banks of the smallest 
 streams. Even in the gutters of a country road, on a 
 rainy day, when the waters are flowing, the process of car- 
 riage of mud, sand, and small pebbles can be seen when 
 they have ceased to flow. ‘The principles on which the 
 valleys of streams are formed can be well traced in these 
 miniature models. We often see on a smooth tilled field, 
 or a new dirt road, how at once the surface becomes 
 divided into distinct watersheds and valleys. 
 
 The insensible evaporation of the water of the seas may 
 be illustrated by taking an open-mouthed bottle or jar 
 and exposing it for a day in a warm room. No vapor is 
 seen to rise, yet the water goes into the air. <A familiar ~ 
 example of condensing clouds can be found in the little 
 shower of rain that falls in cold weather out of the steam 
 from any large steam pipe. 
 
 1 In illustrating all the phenomena of the earth, globes should by prefer- — 
 ence be used. They convey the idea of sphericity of the earth, which is not so 
 easily gained in any other way. A very poor globe is better than a very good 
 map for young students. After the idea of the shape of the earth is well 
 fixed in the mind, maps may be more advantageously used. Above all, avoid 
 the Mercator projections with young children. Despite the distinct advantages 
 of this projection for many practical uses, it has been a curse to the cause of 
 education. The world will always be out of joint to a person who has had 
 them impressed on his mind in youth. I have never been able entirely to clear 
 away the misconceptions they fixed on my own mind. If they are used at all} 
 no pains should be spared to expose their inaccuracies to the child’s full 
 understanding. Even with college students, I feel called on to state their 
 falsity, and the reason for it, every time I turn their attention to one. If 
 glebes cannot be had, use spherical projections. The child can readily com- 
 pass the delineation of a hemisphere. 
 
THE ACTION OF WATER. aT 
 
 In treating of rainfall, the teacher should acquaint him- 
 self with the precipitation in the country where he lives, 
 and give the students the facts of the amount of this rain- 
 fall in the four seasons, and its aggregate. In the United 
 States, this is now well given by the Signal Service. An 
 ordinary pan, six inches deep, with vertical sides, placed 
 on a post three feet from the ground, a score of feet from 
 any building, will give the rainfall during a shower with 
 a close approximation to truth. It is worth while to have 
 a barometer, a regular rain-gauge, and a standard ther- 
 mometer in the schoolhouse grounds. These instruments 
 were once to be had for about fifty dollars of the United 
 States Signal Corps. It is an excellent practice for 
 children to take observations on these instruments, and 
 this is recommended to those teachers who have the time 
 to give to the work. 
 
 The “ oxbow cut-offs,” or moats, that abound on the al- 
 luvial plains of many of our rivers, are very instructive 
 to the student. They help him to form the habit of 
 looking into the past. They afford, perhaps, the best be- 
 ginning for the student in the difficult art of picturing to 
 himself the geological past. No opportunity should be 
 lost of creating and strengthening this habit of conceiving 
 the past. It is very remote from our ordinary ways of 
 thinking, and demands much imagination. It is therefore 
 necessary to wait its growth with patience. It is, how- 
 ever, the most precious of all the mental habits that geol- 
 ogy can give, and it is given so well by no other branch 
 of learning. 
 
 The porosity of the soil, 7.e., its capacity for holding 
 water, may be shown to the student by simple experiment 
 and by the use of the microscope. It is worth while to 
 impress upon the student’s mind the fact that all the life 
 
28 PRIMER OF GEOLOGY. 
 
 of the land depends upon the soil, and that this soil is 
 decayed rock, so that the destruction of rock gives the 
 basis of all our land life. 
 
 In the chapter on frost action, the teacher should use 
 the ordinary facts of our winter experience to illustrate 
 the principles of the text. The passage of snow from the 
 flowery crystals that fall through the air to the compact 
 sheet that it forms when it has lain long on the ground 
 will show the first stage of preparation of a glacier. The 
 compact ice that this snow-sheet forms after it has been 
 rained on is an illustration of its further passage into true 
 ice. 
 
 It often happens in our winter season that the snow 
 that has gathered on the roofs slowly shdes down the 
 slope in a gradual way until it hangs in drooping masses 
 over the eaves. ‘This may illustrate the motion of gla- 
 ciers. Although the action is not precisely the same on 
 the snow that it is on the ice, it is near enough for the 
 illustration. By urging the student to conceive what 
 would happen if the winter’s snows were to be increased 
 to such a depth that the summer’s sun would not be able 
 to melt them away, his mind may be prepared for the 
 difficult conception of a glacial period. 
 
 In this connection, it will be well for the teacher to 
 show the student something of the effects of climatal 
 changes on all the life of the world. The easiest way to 
 do this is by tracing in outline the effects of the Gulf 
 Stream. It should be made plain that this stream carries 
 the heat that falls upon the sea in the Tropics to warm 
 the northern Atlantic region. So effective is its action 
 that the region within the Arctic Circle receives as much 
 heat from this tide of warm water as it does from the 
 direct action of the sun. When this is made clear to the 
 
THE ACTION OF WATER. 29 
 
 student, the teacher should show him that the Kuru 
 Sivo, or Pacific Gulf Stream, is now barred out from the 
 Arctic Circle by the lands that form the north-eastern 
 parts of Asia and the north-western parts of America. If, 
 in the constant changes of the lands, these barriers should 
 be lowered beneath the sea, as they have often been low- 
 ered in other geological ages, then the Pacific Gulf Stream 
 would enter freely into the Arctic Ocean. The effect of 
 this conjoint action of the ocean streams would be very 
 great. The climate of the whole Northern Hemisphere 
 would be changed. It is likely that it would almost en- 
 tirely destroy the winters of the region about the North 
 Pole, making their average climate about as warm as that 
 of Southern England. Almost all children above twelve 
 years of age can compass this idea ; and, when it is well in 
 their minds, they will have a larger idea of climate than 
 can be obtained in any other way. 
 
 When the teacher is so fortunate as to be able to show 
 the student the phenomena of the seashore, he should on 
 no account omit to do so. There, more than anywhere 
 else, the phenomena of the world’s principal machinery is 
 laid before our eyes. It is well to begin with the study 
 of the destructive work that is going on upon the chosen 
 bit of shore. If there are cliffs near by, the first study 
 should be upon the method by which the sea successfully 
 assaults them. The wide contrast between their form and 
 that of the beach should be made clear. Then the de- 
 struction of the sand and pebbles on the sandy beach 
 should be clearly seen, the drifting inland of a certain 
 portion of the sand, and the washing out to sea of the 
 fine ground sand which can float on the water. 
 
 If possible, the beach should be seen during all the 
 hours from high to low water; in the time of spring 
 
30 PRIMER OF GEOLOGY. 
 
 tides, for the various conditions of its functions are not 
 evident at any one hour in the tidal period. At high 
 tide we find the destructive work of the sea best exhibited. 
 At such times, the waves beat against the cliffs and 
 against the steep part of the beaches. If the waves are 
 high, the wear of both can be readily traced. As the tide 
 goes out, revealing the lower levels of the shore, there are 
 several facts that can be made extremely interesting to an 
 intelligent child. The crowded barnacles and seaweed on 
 the rocks, which serve to protect them against the beat of 
 the waves, the way in which each.rock and cranny among 
 the shoals gives shelter to a host of living things, are worth 
 attention. It should be seen that the constant rush of the 
 water serves to bring food to these creatures, so that, 
 though they are often crushed between the rolling stones 
 or broken up on the beach, they take these risks to get 
 the chance of life that is here opened to them. ‘The ob- 
 server should notice that the water along the shore is 
 much richer in food than in the open sea. The constant 
 grinding up of seaweed, mollusks, star-fishes, and other 
 creatures fills the water with matter that is excellent 
 nutriment for all these animals. It is this abundance of 
 provender that causes them to brave the dangers of the 
 shore. If we take up a glass of water from the surf, we 
 find it full of the broken remains of animals and plants. 
 When the tide is lowered beyond its middle point, we 
 begin to see that part of the shore where the construction 
 exceeds the wearing. Flats of sand and mud that gener- 
 ally stretch far from the shore line to the seaward begin 
 to be bared. ‘These flats are usually formed from the 
 waste of the shores ground up upon the beaches or along 
 the cliffs. The existence of these mud flats, only a few 
 feet below the high-tide mark, shows how little power the 
 
THE ACTION OF WATER. 31 
 
 sea-waves have, except when they pound against the cliffs 
 or roll the stones upon the sea-beach. 
 
 It is not often that there is any evidences of change of 
 sea-line along the coasts that can be made clear to the 
 student. If such there are, he should be made to note 
 them at any rate. The teacher should seek to have him 
 frame some conception of what the action of the sea must 
 be as the land rises from, or sinks into, its depths in its 
 constant changes of level. Even a young child can see 
 that, as the land rises and falls, the seashore is drawn 
 across the land, subjecting any position of the surface to 
 its peculiar wearing action. This is one of the largest 
 conceptions that can be brought into the mind by the 
 study of existing geological causes, and it should be well 
 impressed upon the mind. The fact that these old beaches 
 are little traceable upon the surface of the land is due to 
 the action of frost and rain upon the rocks, which the old 
 beaches left in the process of retreat, as the land came up 
 from the sea. This will serve to show, though it is but 
 one of many instances, how powerful have been these 
 wearing agents that work on the surface of the lands. 
 
 Along the coast of New England, the teacher will be 
 able to point the student to old beach lines wherever he 
 can find the face of a terrace of gravel and sand looking 
 towards the open water. Such terraces facing the sea are 
 not uncommon all along the shore from New York to 
 Eastport. They are also equally conspicuous along the 
 shores of the Great Lakes of the St. Lawrence, especially 
 along the southern coast of Lake Erie. It should be 
 noticed, however, that the beaches along these and other 
 lakes are due to the lowering of the surface of the water, 
 and not, as along the shores, to a positive rising of the 
 land. Otherwise, the shores of the Great Lakes afford 
 
32 PRIMER OF GEOLOGY. 
 
 essentially the same conditions as those of the ocean, 
 though on a smaller scale and without the peculiar action 
 of the tides. 
 
 I have found the tides useful in impressing upon the 
 mind of the student a sense of the far-reaching operations 
 of nature. Especially are they valuable in conferring a 
 sense of the power of the gravitative force in the universe. 
 The theory of tidal action is, when fully stated, too com- 
 plicated a matter for the use of young minds, but the 
 general fact that the tides are due to the attraction of the 
 heavenly bodies; that the moon makes the greater wave, 
 because, though the smallest, it is the nearest of the 
 heavenly bodies that is visible to the naked eye; that 
 the sun, though really larger, makes only a very small 
 tide on account of its remoteness: yet, further, that every 
 star in the heavens has some slight pulling effect upon 
 the earth; all these are widening ideas that cannot be 
 grasped without their having some small educative power. 
 
 The only objection to the seashore as a place for teach- 
 ing is, that it is, on the whole, too diverting and too con- 
 founding, by its variety of impressions, to leave the mind 
 much chance for thought. I have rarely found a youthful 
 mind that was able to withdraw itself from the intense 
 life of the shore to any reflections on smaller things. On 
 this account, all persons find the sea-line a hard place for 
 thinking, and the child most of all. Instruction from the 
 impression of the seashore can most advantageously be 
 given after leaving the perplexing scene. 
 
 Although glaciers and glacial streams have a large 
 place in modern geologies, they have been slenderly 
 treated in this primer because the evidence is hard to 
 point to a child. The whole subject is wrapped in a 
 deeper cloud than any other geological question of great 
 
THE ACTION OF WATER. 33 
 
 importance; yet the impressions that may be obtained from 
 a study of the more evident phenomena are too valuable 
 to be neglected. In nearly all the Northern States of 
 this country, it is possible to show the student much that 
 will lift his mind to large ideas through simple observa- 
 tions on glacial phenomena. 
 
 If possible, access should be found to some surface worn 
 by glacial ice. This is generally to be found in any 
 region within the range of the ice sheet of the last glacial 
 period. On such a surface, the scratches, the grooves, and. 
 the general wearing down and rounding of the surface 
 should be shown. The contrast of this surface, which has 
 only recently been exposed to the action of the atmos- 
 phere, with any surface long enough exposed to have had 
 its glacial marks effaced by the-action of the air, should 
 be dwelt upon, in order that the peculiarity of the glacial 
 surface may be fully perceived. Then, if possible, some 
 pebbles, that have been carried for a considerable distance, 
 should be used to make the transporting action of the 
 glaciers apparent. After these points have been made 
 clear, the teacher may freely ask the beginner to suppose 
 the region where they occur to have been covered in a 
 recent geological day with ice to the depth of several 
 thousand feet, which slowly, only a foot or two a day, 
 crept toward the southward. It will not do to force such 
 conceptions, for the youthful mind is more impatient of 
 an illy-demonstrated conclusion than is the trained logician. 
 The teacher must first exhibit the reasons for his belief 
 in a condition of things before he demands acceptance of 
 so seemingly preposterous a proposition as that of a gla- 
 _ cial sheet having been over these lands. With this point 
 well made, the teacher will find that the youth of any 
 imagination becomes exceedingly interested in the condi- 
 
34 PRIMER OF GEOLOGY. 
 
 tions of those days, so unlike all those of our own time. 
 If the instructor cares to do so, he may proceed to trace 
 some of the most obvious features of glaciers as they are 
 to be found among the remnants of ice left in the valleys 
 of mountains or about the polar regions. It will, how- 
 ever, be found that the existing examples of glaciers are 
 rather remote from experience, and that even their foot- 
 prints that can be seen are better than the things them- 
 selves beyond the reach of eye. 
 
 After the student has conceived the mighty revolution 
 of the glacial period, it is worth while to tell him that 
 there have certainly been many, probably scores, of such 
 ice times in the earth’s history; yet they have been so 
 limited that, though it might seem likely that they would 
 kill all the life of the earth, they have left it constantly 
 unharmed. It is through such conclusions that we must 
 hope to find the way to the enlargement of the student’s 
 mind. Each exercise upon such problems tends to the 
 cultivation of the scientific imagination, which it should 
 be the principal object of the teacher to develop. 
 
 The teacher will be able to supplement the lesson on 
 sand with many important illustrations that may be taken 
 from the immediate neighborhood of the school, whatever 
 may be its position. If this position be in any rural dis. 
 trict, there will be abundant access to various forms of 
 sand. It will generally be possible to trace the breaking 
 down of some rock that yields sand. This may be a crys- 
 talline rock, such as granite or syenite, or it may be a 
 sandstone, a rock itself composed of sand grains once 
 free, now cemented together, now again by decay return- 
 ing to the state of separated grains. Such examples are 
 of great value to the teacher, as they serve to show the 
 student one of those successions of events which it is 
 especially important that he should be able to perceive. 
 
THE ACTION OF WATER. Oo 
 
 If the student can have access to the seashore, or to any 
 running stream, the process of making and wearing down 
 this sand into mud can be shown him. In almost any 
 sand cliff, the re-cementation of this sand can be shown, 
 a process whereby it, passes again from the state of inco- 
 herent grains to a stone. This is most easily seen where 
 the sand is penetrated by iron oxides, or by lime-charged 
 waters. By the action of these cementing substances, 
 sands that have recently been formed may be cemented 
 into a rather solid stone. 
 
 Something can be done to fix the interest of the stu- 
 dents by the use of the magnifying glass upon ordinary 
 sand. This will show the battered and age-worn look of 
 the grains, which is not to be seen with the naked eye. 
 
 The substance called mud is the last stage of the wear- 
 ing to which substances are brought by the various agents 
 of decay. The student should be brought to consider all 
 mud, not as a repulsive substance, but as the carefully- 
 prepared, finely-divided rock material, from which all the 
 land _ plants draw the nutriment which makes their own 
 life possible, as well as the substance which, by the ease 
 with which it is carried in water, is the most widely dis- 
 tributed over the sea-floors, and hence the most potent 
 agent of rock-building. In a word, he should see that 
 this fine division of the rock matter is the condition that 
 must precede much of the most important work of the 
 world. 
 
 This is the last point at which to introduce the student 
 to the action that goes on in the soil stratum of the 
 earth. Any soil will furnish evidence of the progressive 
 decay of stones that are contained within it or beneath 
 its floor. In this silent mechanism of the soil, the most 
 important processes of the earth go quietly on, for there 
 
36 PRIMER OF GEOLOGY. 
 
 the matter of rocks comes into a shape to combine with 
 water and the materials of the air in order to enter into 
 the plants. It will frequently be necessary to recur to the 
 structure and mechanism of the soil, for there we find 
 the beginning of some of the most important changes that 
 the geologist has to note. 
 
 This study of the soils can be carried on with particular 
 advantage where the school is in a rural district. The 
 children should be taught to see the action of plants and 
 animals in making this soil. The teacher will draw many 
 hints for interesting topics of discussion in Darwin's 
 charming memoir on earth mould and earthworms. He 
 will there learn that in any acre, our gardens and tilled 
 fields as well as in most forest areas, there are from twenty 
 to fifty thousand of these creatures constantly at work in 
 pulverizing and dressing the soil, and in making it the 
 more fit for the uses of plants. Many of these observa- 
 tions on the behavior of earthworms are quite within the 
 limits of the child’s study, and may be repeated to advan- 
 tage. The action of insects, moles, and burrowing ani- 
 mals in opening the soil to the entrance of the air and 
 rain, as well as the constant stirring that it receives from 
 the rocks, should also be considered. In this way, the 
 student will come to conceive to what a host of actions 
 we owe the fertility of this life-giving decay level of the 
 earth. 7 
 
 Any old quarry will show the interesting process of 
 soil formation. If such be inaccessible, then the bare 
 surface of any rocky cliff may be used; or old masonry 
 will show how lichens or the smaller mosses will lay the 
 foundations of the soil. Various forms of fertilizing the 
 soil, such as subsoil-ploughing, or manuring with pow- 
 dered lime, will furnish instances that show how the divi- 
 
THE ACTION OF WATER. 37 
 
 sion of the rock matter into minute bits serves to increase 
 the supply of plant food, and thus to illustrate the action 
 of decay in the preparation of the soils for life. Another 
 familiar and instructive action may be found in the work 
 of frost in enriching the soil. Every country child can 
 see that the farmer finds a profit in turning up the heavier 
 soils so that they may be strongly acted on by the frost. 
 He should see that this frost action causes the rock bits in 
 the soil to be split into yet finer bits, yielding more sur- 
 face for the roots to work upon. 
 
 It will not be amiss for the teacher to do what he can 
 to create in the student’s mind a sense of respect and re- 
 sponsibility for the soil, on which all human interests 
 depend. He should be brought to see that its importance 
 makes it worthy of the utmost care, and that all who deal 
 with it have the greatest natural treasure in their keep- 
 ing. It is particularly necessary to impress this sense of 
 duty by the soil upon all our youth who are likely in any 
 way to have to do with the care of the soil, for there is a 
 disgraceful neglect in this matter in all parts of America. 
 If a soil is impoverished only by careless agriculture, it 
 may be restored by a generation of care; but in large 
 areas of this country the soil is actually stripped away by 
 the rains, so that ten thousand years of care could not re- 
 store it. The same action has gone on in modern days 
 in many European States, especially in those about the 
 Mediterranean, with the result that the life-sustaining 
 power of the peninsula of Italy has been much reduced 
 since Roman times. 
 
CHAPTER II. 
 THE MAKING OF ROCKS. 
 
 Qe first chapter was designed to give the student an 
 
 idea of the processes at work in preparing materials 
 for rock building, through the decay of the preceding 
 rocks. This chapter is intended to show them how these 
 rocks are composed and metamorphosed so as to make new 
 rock masses. In this part of the subject, the teacher can- 
 not find so many additional instances to illustrate the 
 matter as in the previous chapter. The following sugges- 
 tions may, however, be found of value. 
 
 In the first place, the effort should be made to encour- 
 age the student to find specimens of the simpler rocks, 
 or, as will be the most convenient in cities and towns, of 
 the building stones used in’ the vicinity. Almost any 
 town will furnish in its houses and its cemeteries speci- — 
 mens of a half-dozen of the most important stones. Sand- 
 stones, marbles, and slates are sure to be represented. 
 
 Yonglomerates are less common, but the student can 
 readily imagine a mass of pebbles cemented together, and 
 so get the impression of what a conglomerate is. 
 
 If there are any quarries of stone, especially of bedded 
 stones, in the neighborhood, the student can be shown the 
 structure of rocks when they pass from the divided state 
 of sediments to the aggregated shape of rocks. In these 
 quarries he should be shown, if they are present, how the 
 fossils lie in the rocks, and how they are akin to the crea- 
 tures that live to-day, while they are entirely different in 
 their kinds, 
 
THE MAKING OF ROCKS. 39 
 
 The teacher should make it plain that there are two 
 kinds of rocks: one group, such as sandstones and con- 
 glomerates, is entirely the product of physical forces ; 
 while another group, such as coals or limestones, is in 
 the main built of the remains of animals and plants. 
 There is no other way in which the student can be so 
 readily brought to understand the vast mass and duration 
 of living creatures on the earth’s surface so well as by 
 showing him that the limestones that cover the floor of 
 the Mississippi Valley, to the depth of thousands of feet, 
 owe their existence to the life and death of animals. It 
 will not often be possible for the teacher to show the stu- 
 dent limestone quarries, yet every cemetery has its tombs 
 or headstones of marble, which afford specimens of lime- 
 stones, which, by the action of heated waters, have been 
 converted into crystalline rock. Some of these tombstones 
 contain evident fossils; but, even if they are crystalline, 
 the student can readily be made to see that each one of 
 them is the tomb of thousands of creatures that lived and 
 died on the old sea-floors. 
 
 In the matter of coral islands, the teacher will find a 
 subject that will assume a very keen interest in the minds 
 of his students. There is probably no question not de- 
 monstrable by specimens that as strongly appeals to the 
 ordinary imagination. It will be well if he can prepare 
 himself to give a somewhat fuller account of the coral 
 animals than the text of the primer affords. Any good 
 wall-map will give the student an idea of how these 
 islands are scattered through the broad fields of the Pa- 
 cific and Indian Oceans. For further details, the teacher 
 may advantageously consult the admirable “Corals and 
 Coral Islands” of Professor Dana, which gives abundant 
 information of trustworthy and popular sort. 
 
40 PRIMER OF GEOLOGY. 
 
 It'is much to be desired that each instructor in geology, 
 or in any other department in natural history, should have 
 a microscope of the simpler sort at his command. There is 
 no other teaching instrument so effective in awakening the 
 youthful mind and getting it beyond the region made 
 tedious by the sense of the commonplace. It need be 
 but a simple and cheap instrument, with few accessories 
 in the way of apparatus. Indeed, it is better that it should 
 be of the simpler sort, for the beginner in the art of 
 microscopy can make no especial profit from the costlier 
 machinery of elaborate investigation. With such a micro- 
 scope, the teacher will be able to show the students some- 
 thing of the multitudinous lower life that enters into the 
 building of our rocks. 
 
 I hope the teachers who use this text-book will enforce 
 the points concerning the supply of lime and other sub- 
 stances carried to the sea, through the dissolving action of 
 water containing carbonic dioxide (see p. 44 of Primer). 
 This is one of the large general facts concerning the 
 machinery of the earth which the student will readily 
 comprehend, and which cannot fail to enlarge his concep- 
 tion of the world. 
 
 In the familiar phenomena of coal, the teacher will find 
 another opportunity of showing the student an instructive 
 succession of facts, beginning with ordinary growing 
 plants, passing then to such decayed woody matter as our 
 wet forest-beds or swamps afford. The student’s obser- 
 vation can be led along the series through lignite, soft 
 bituminous coal, to anthracite, and finally to the peculiar 
 conditions of carbon found in graphite and the diamond. 
 It should be made plain that the beginning of this won- 
 derful series is to be found in the carbonic dioxide or car- 
 bonic acid gas of the atmospheric air, and that the most of 
 
THE MAKING OF ROCKS. 41 
 
 this gas is returned at once to the air by the decay of the 
 dead plants, only a small part finding its way into the 
 strata of the earth. In this connection, the teacher may 
 advantageously note the fact that all our limestones are 
 in a certain way related to the coals, in that they too are 
 largely composed of carbon, but combined with lime. It 
 should also be brought to the students’ notice that while 
 the coals are altogether the product of vegetable life, the 
 combinations of carbon in our limestones are mainly the 
 result of the animal life. 
 
 I have found that the student is readily attracted by the 
 fact that all our coals are essentially stores of solar force 
 gathered from ancient days and imprisoned in strata. By 
 showing him how the heat from the coal that is burning 
 before him was gathered from the sunshine of days that 
 have vanished, for millions of years, the teacher will be 
 sure of making a most profitable impression on his mind. 
 
 Peat bogs are generally distributed throughout the 
 Northern States of America, and, even where they do not 
 occur, there are sure to be swampy places that will illus- 
 trate the first stage of the process of coal-making. When 
 the teacher is so fortunate as to be able to show the stu- 
 dent coal in its original beds, attention should be called 
 to the lower level of fire clay, or the “dirt bed” in which 
 the. plants were rooted, and to the evidence that after the 
 coal was formed, it was buried beneath the sea, where it 
 was covered by mud and sand. It will be well for the 
 teacher to dwell upon these lessons that are to be derived 
 from the geology of coal, for the reason that the familiar 
 experience with the substance, and the sense of its eco- 
 nomic importance, makes it easy to excite and sustain a 
 lively interest in the stages of its history. 
 
CHAPTER III. 
 THE WORK OF WATER AND AIR. 
 
 N many accounts, it would be best to begin the study 
 
 of geology by teaching the important phenomena of 
 the air. The only objection to doing so lies in the fact 
 that the air being essentially invisible, it is not easy for 
 the youthful mind to accept any statement concerning its 
 peculiar properties. That a thing is, and is invisible, per- 
 plexes the pupil. I therefore advise the teacher to do 
 all he can to give the student a sense of the reality of 
 the air. In the pursuance of this object, the first effort 
 should be to force the perception that the air is sub- 
 stantial. To make this impression, many simple experi- 
 ments may be devised. The student should be shown 
 distant hills, that he may observe the dimming of their 
 features by the thickness of the air, while the moon, that 
 is perhaps ten thousand times as far away, shows sharp 
 against the sky. It then should be explained that, on 
 account of the greater density of the air next the surface 
 of the earth, we look through several times as much air 
 when we gaze on a mountain thirty miles away as we do 
 when we look at the moon. The simplest way, however, 
 of giving a sense of the air’s substantiality is by forcing 
 the student to observe the action of the wind. 
 
 Next to the substantial character of the air, the teacher 
 will do well to show that the air is not a simple thing, 
 but that, like almost everything else in the world, it has 
 a complicated structure. The shortest way to this result 
 is by burning a candle in a closed glass jar, showing how 
 
THE WORK OF WATER AND AIR. 43 
 
 the flame of the candle takes out something in its burning 
 and finally expires. By showing the diminished size of 
 the candle, the child will see that a part of the carbon 
 of the tallow has gone into the invisible state in the air. 
 It will then be easy to explain that a plant growing in 
 this air would again remove the carbon from its invisible 
 state, depositing it in the woody matter, that the plant 
 fed to an animal might be again converted into the tallow. 
 In this way, the idea of the air as a great reservoir, like 
 the sea, into which various actions are passing gaseous 
 matters, and from which other agents were constantly 
 taking these substances back into visible forms, may be- 
 come well impressed on the student’s mind. 
 
 In approaching the phenomena of the winds, the teacher 
 should take the following measures for bringing the matter 
 into a concrete form. ‘The schoolroom will always show 
 the phenomena of currents induced by differences of tem- 
 perature. In cities, it is an easy matter for children to 
 notice the inrush of cold air on the lower floor in cold 
 weather, and the outrush of cold air on that level when 
 the outer air is warmer than that of the building. If the 
 schoolroom has a heated stove, it will show the system 
 of currents as noted in the text. If the conception of 
 causes of these actions is clearly grasped by these illus- 
 trations, the mind of the student will readily extend the 
 conception to the larger field of the earth’s hemispheres. 
 Next, the student should see the effect of the friction of 
 the winds upon the water in producing currents. ‘This 
 can be easily illustrated by blowing in a basin of water. 
 This idea can be readily extended to include the surface 
 _ of the oceans. As soon as the child has had the least 
 exercise in inferring the behavior of great things in 
 the world from the action of small things that he can 
 
44 PRIMER OF GEOLOGY. 
 
 control, he will welcome this mental process with eager- 
 ness. 
 
 In returning to the work of water, the teacher will do 
 well to compare in a general way the three great fluid 
 envelopes of the earth. Outside of all filling, the great 
 spaces between the spheres of planets and suns is the 
 universal ocean of the ether that gives no resistance to 
 any motions, and seems to have none of the qualities 
 that we associate with matter. Between all the earth’s 
 surface and this region of pure ether is the realm of 
 air, a very fluid mass, made mostly of nitrogen, but con- 
 taining something of many other things. Below the air, 
 and covering only a part of the earth’s surface, is the 
 ocean, composed mainly of water, but holding something 
 of all other substances dissolved in it. All these three 
 fluid realms are somewhat commingled. ‘The ether ex- 
 tends through all the interspaces of the atoms of air 
 and water, some part of the air is mingled in each drop 
 of the ocean’s water, and some portion of the water 
 from the seas is constantly to be found in the smallest 
 visible portion of the air. In the sea, the air serves to 
 give breathing material to the marine animals; through 
 the air the water goes to all its work upon the land. 
 These phenomena of inter-action between water and air 
 are extremely varied, and generally complicated; but, 
 taken in a limited way, they are very interesting even 
 to the dullest students. They are among the largest and 
 most easily illustrated conceptions that can be brought into 
 the child’s mind. \ 
 
 Some of the best means of enforcing attention to the 
 sea can be found in our common aquariums. Even if 
 small in size, they will serve to show the student how fitted 
 are the realms of water for the uses of life. They also 
 
THE WORK OF WATER AND AIR. — 45 
 
 serve very well to show the student how necessary it is 
 that the water should be aerated in order to serve the 
 needs of animals; and the function of plants in supplying 
 oxygen can also be made plain. 
 
 In illustrating the heat-carrying power of water, the 
 ‘teacher will not find it easy to obtain striking familiar 
 illustrations. Perhaps the best may be had in the steam- 
 pipes for warming buildings, by which heat is often 
 carried many hundred feet from its source. The student 
 should be convinced of the large heat-storing power of 
 water as compared with any other substance. If it is 
 desired to show this in practice, an alcohol lamp may 
 be used in one case to melt lead, in the other to vapor- 
 ize water. The student will readily see that the lead 
 has its heat raised to several times the temperature of 
 the water with a less amount of heat. This illustration 
 is inconvenient for the class-room, yet I know no other 
 that is very effective. 
 
 It seems to me well worth the teacher’s while to show 
 how great is the work of water in all the machinery of 
 organic life. Perhaps the most striking experiment that 
 can be made is that of growing any plants in water, so that 
 they have nothing but what they obtain from that fluid 
 or from the air. If the teacher possesses a microscope, 
 the phenomena of circulation of sap or of blood in the 
 lower animals or plants may be shown to the student, but 
 a different reference to the well-known importance that 
 the water bears to all other substances in the human 
 body, and some illustrations from the process of drying in 
 the arts may serve the purpose of enforcing this lesson. 
 
 The lesson on mineral veins is put into this chapter 
 because it seemed desirable that the student should see 
 that the most important part of their phenomena depends 
 
46 . PRIMER OF GEOLOGY. 
 
 on the action of water. All the most important elements 
 in the causation in mineral veins comes within the easy 
 reach of illustration. Saturate some water with sugar to 
 the point where it will dissolve no more, place a thread in — 
 the fluid,-and the familiar forms of sugar crystals show, 
 themselves. Salt, alum, and a host of other substances, 
 used in a similar way, will bring the phenomena of depo- — 
 sition by crystallization clearly before the mind. It will 
 be easy also to illustrate the fact that heat gives the water 
 a power to take substances into solution which it will be 
 compelled to throw down when it cools. All the sub- 
 stances mentioned are more abundantly dissolved in water 
 that is heated than in water that is cold. 
 
 The effect of carbonic dioxide gas in the water cannot 
 be so easily shown, but if the teacher has a small lot 
 of chemical apparatus, it will be easy to illustrate that 
 also. Actual veins exist in nearly all of our hard strati- 
 fied rocks, and are of common occurrence in the metamor- 
 phic rocks; so that the teacher who has any contact what- 
 ever with the rocks cannot fail to find abundant examples 
 of this action. He may readily recognize veins, and sepa- 
 rate them from dykes by their structure. They have the 
 materials that compose them arranged in bands roughly 
 parallel with the boundary walls of the crevice in which 
 the vein was formed. Moreover, this rock is generally 
 more distinctly crystalline than it is in crevices that have 
 been filled with lavas. Quartz veins are the commonest 
 in most rocks. In fact, the only way in which quartz 
 occurs in an unmixed condition is in veins; it seldom or 
 never occurs as a dyke stone. 
 
 It will be noticed that the series of changes which lead 
 metallic substances from the vein through the watery solu- 
 tion to the sedimentary deposits, and thence back to the 
 
THE WORK OF WATER AND AIR. 47 
 
 vein again, is one of the most complicated, as it is one of 
 the most important, of the geological cycles. I find that 
 it is not readily apprehended by the student, and am con- 
 vinced that it will be well for the teacher to strive to lead 
 a student to its full understanding. Nowhere else do we see 
 so well how destruction is but a stage in creation. I feel par- 
 ticularly interested in having these cycles of change made 
 clear to the student’s mind, because I find that young people 
 readily get a notion that there are phenomena of pure 
 destruction in nature, and that the world is constantly 
 tumbling towards ruin. The ordinary experiences of life, 
 especially the imminent personal death they have just 
 learned to apprehend, tend to foster this crude and painful 
 conception of nature. It is the best work that geology 
 can do to diminish the darkness of this shadow, and to 
 show that, in a larger way, death is not destruction, but 
 only a process of change which, on the whole, lifts the 
 world ever higher on its way of life. 
 
 The course of water in underground channels is a very 
 charming subject for the young imagination. It is not 
 easy to show children the phenomena of rivers in such 
 fashion that they will find their fancy appealed to; but 
 trace the way of a spring down to its outlet, and there is 
 a chance for fancy to take hold of the matter. 
 
 The first point to be made clear is the dissolving power 
 of water on the rocks. The cutting power of water 
 charged with pebbles, as it flows over rocks, will be easily 
 grasped by the student, but he should also see that each 
 rock is in some degree, however small, dissolved by water. 
 In granites, etc., this absorption is almost infinitesimal, 
 - but in limestone it is considerable, especially when the 
 water is somewhat carbonated. I know of no very good 
 indoor illustration of this action. The teacher who lives 
 
48 PRIMER OF GEOLOGY. 
 
 in any limestone country will have abundant familiar in- 
 stances to which to appeal. But to those who have no 
 limestone beds near by, the neighboring springs will serve 
 to illustrate the points set forth in this connection. 
 
 In the matter of the streams of air which rush into or 
 out of the larger caverns, the teacher will find another 
 capital instance of the facts of motion of the air under 
 the influence of temperature changes. ‘This can readily 
 be brought to illustrate the principle of the atmospheric 
 movements set forth in the previous chapter. 
 
 The subject of volcanoes is an exceedingly disadvan- 
 tageous one for the teacher, as there are few familiar 
 instances that can be brought to the student’s attention. 
 There is, however, an element of strangeness in their 
 action, which causes their phenomena to be of much inter- 
 est to the young mind. 
 
 I think it would be well for the teacher to preface this 
 chapter with a simple account of the distribution of vol- 
 canoes, showing the child on the globe the regions where 
 they abound, and making it plain that the part of the North 
 American mainiand north of Mexico is practically with- 
 out active volcanoes, though there are some on the west 
 coast that have been in action in recent times, and occa- 
 sionally show a little trace of activity. Next the explo- 
 sive power of steam should be made as clear as possible. 
 The case of steam boilers is a familiar one. If the teacher 
 is willing to take the necessary trouble, he can give a 
 simple example of such explosive action, thus illustrating 
 geysers as well as volcanoes, by the following means: 
 Take a piece of common gas-pipe, say twelve feet long 
 and one inch in diameter, plugged at the lower end. Bore 
 a hole through the floor of any room so that this pipe may 
 extend to near the floor of the room below. Let the upper 
 
THE WORK OF WATER AND AIR. 49 
 
 open end terminate in a large tin funnel, say four feet in 
 diameter, or, in place of this, any ordinary tub will answer. 
 Fill the pipe with water, allowing a little depth of water on 
 the bottom of the tub or funnel. Then heat the bottom 
 of the pipe with a large alcohol lamp, or in any other con- 
 venient way. 
 
 When the heat is applied to the tube, the temperature 
 of the water quickly rises to above the boiling-point in 
 the section immediately next to the lamp, while the water 
 in the upper part of the tube remains unchanged in tem- 
 perature, and, by its pressure, acts as a plug to restrain the 
 escape of the steam from the heated portion. The heat 
 of the lower portion increases until it attains a point 
 where the tension or tendency of the steam to force its 
 way outward is sufficiently strong to overcome the pres- 
 sure of the water above it. Then the lower and most 
 heated portion of the water passes rapidly into steam, 
 driving the restraining water before it. The cold water 
 is blown up into the air in a fountain whose height is 
 determined by the depth of the pipe and the consequent 
 temperature of the water at the time of explosion. It is 
 not a simple, instantaneous outburst, like the discharge of 
 a gun, but proceeds more slowly. The process is this: at 
 first a little water is forced out by the passing into steam 
 of the water that is next the fire, and is hot enough to 
 overcome the pressure. This makes it possible for the 
 next higher lying water to change to steam, which in time 
 discharges more water, still further reducing the pressure, 
 and permitting the collection of more steam, until in the 
 end all the water passes out of the tube. This is an exact 
 - parallel of the action that takes place in geysers, and is a 
 fair illustration of the forces that produce the volcano. In 
 the geyser we have a tube or crack that has its lowest part 
 
50 PRIMER OF GEOLOGY. 
 
 in a mass of old lava that still retains a heat great enough 
 to bring water above its boiling-point, and a rainfall great 
 enough to keep the tube filled. The result is a succession 
 of explosions such as will take place in the funnel-topped 
 pipe of the experiment. When the water has been blown 
 out of the pipe, it will be gathered in the funnel, and again 
 forced up into the air. The process will be repeated as 
 long as the heat and water are kept in this relation. In 
 the natural geyser, the water rushing back into the pipe 
 causes itself a conical opening, which answers to the fun- 
 nel of the experiment. 
 
 In the volcano the pipe is more complicated. There is, 
 in the first place, the covering of sedimentary rock that 
 has to be blown away in order that the pipe may be 
 formed. Then, between the successive eruptions of the vol- 
 cano, there is a plug of hardened lava formed that must be 
 removed before the steam can find its way of escape. Even 
 when formed, the tube of a voleano does not act as that 
 of a geyser. The water does not find its way down to the 
 heated depths of the earth by gravity, but probably is 
 built into the earth as the rocks are formed on the sea- 
 floors. Still, this experiment has the advantage of show- 
 ing the explosive force of steam, even when its tempera- 
 ture is raised only a slight degree above the boiling-point. 
 It should be made clear to the student that in the volcanic 
 sources the rocks are more hot than molten iron, and the 
 steam has an explosive power to be compared with gun- 
 powder. 
 
 Even if it is not possible to give the above experiment, 
 the teacher will do well to describe it clearly to the 
 student, accompanying the account with a description 
 of some geyser phenomena, such as those observable in 
 the Yellowstone region or in Iceland. If the teacher is in 
 
THE WORK OF WATER AND AIR. 51 
 
 a position to show the student any of those processes of 
 the arts in which stony matter is melted, it will be well to 
 make use of these arts in the illustration of this subject. 
 
 The flows of metal and slag from a blast furnace imi- 
 tate in all essential features the behavior of lava streams. 
 They are, in their composition essentially like many lavas 
 from volcanoes, so that the mineralogist would often be 
 puzzled to show the differences between the two classes of 
 products, — those of nature and those of art. In a less 
 perfect way, the glass furnace will give the student an idea 
 of the behavior of molten rocks. Even the ordinary black- 
 smith’s forge, with its slag, or, better, the foundry with 
 its melted pig iron will serve to explain that part of vol- 
 eanic action which depends on the melting of rocks. 
 
 It is difficult to give the student an idea of the vast 
 forces involved in the production of the greater accidents 
 of the earth. None of our arts imitate them. The near- 
 est analogy is from the action of gunpowder. The rush 
 of gases from the cannon’s mouth affords the nearest like- 
 ness to the up-rush of volcanic gases from the crater. If 
 the student has ever seen the swift motion of the smoke 
 from a piece of artillery, he may be helped to a conception 
 of what a very powerful eruption is by imagining a vast 
 cannon, perhaps a mile in diameter, planted vertically, and 
 exploding for days with several times the force of artil- 
 lery. If this comparison cannot be made, then the famil- 
 iar out-rush of steam may supply a weaker basis for the 
 imagination. 
 
 The building of volcanic cones can be illustrated in 
 various ways. It may be shown by a jet of air or steam 
 emerging vertically, bearing with it particles that are 
 thrown upward, and fall upon the table from their grav- 
 ity; but such apparatus is not commonly in the control 
 of teachers. 
 
52, PRIMER OF GEOLOGY. 
 
 The generation of the volcanic steam within the earth’s 
 crust by the intense heating of strata needs careful illus- 
 tration, else the principle will escape even the mature stu- 
 dent. There are many collateral illustrations. The walls 
 of our buildings holding the heat in will give a notion of 
 non-conductive action. The effect of putting successive 
 blankets or coats of cloth on the warm body will aid the 
 conception. If the idea of a constant outpouring of heat 
 through the crust is first secured, then it can be made 
 clear that putting on a deep coating of rocks will serve to 
 hold the heat in, so that the old buried sea-floor will in 
 time receive a high temperature. 
 
 If the teacher has an opportunity, it will be well to give 
 a history of the various eruptions of Vesuvius. An excel- 
 lent account of this mountain may be found in the Veswu- 
 vius of Professor Phillips.1 
 
 The recent great eruptions of Java, which have been 
 the greatest in human history, have extended their effects 
 over the whole world. As yet, the accounts of this great 
 disturbance are exceedingly imperfect. Still the fact that 
 the dust from these eruptions, thrown far up into the 
 earth’s atmosphere, has drifted over the whole earth, is a 
 matter that cannot fail to give a new interest to volcanic 
 phenomena.? 
 
 1 Vesuvius, by John Phillips, A.M., &c., Oxford, at the Clarendon Press, 
 
 1859. 
 2 See an article on Red Sunsets, Atlantic Monthly for April, 1884. 
 
CHAPTER IV. 
 CURRENTS OF THE AIR AND SEA. 
 
 ey this chapter we return to the action of the atmos- 
 
 phere, in order to give the student a better basis for 
 understanding the action of this important part of the 
 earth’s machinery. There is here a certain element of 
 repetition of matter given in a previous chapter. This 
 repetition is intentional. The work of the air is at the 
 root of all the earth’s life. It is impossible to dwell enough 
 upon this subject. : 
 
 The fact of the storage of heat in the earth, and its con- 
 veyance above the surface in the winds and currents, should 
 be dwelt upon. The illustrations given in the text are so 
 simple that they need not be carried much farther. They 
 may, however, be supplemented in the following ways: 
 Let the teacher explain how these currents have been 
 determined and studied. First, it should be shown that 
 the drifting of ships called the attention of mariners to 
 this motion of the sea. Determining their rate of travelling 
 by their “logs,” the mariners found that, in going certain 
 ways, they always travelled faster than their reckoned rate 
 of sailing should have taken them; while, in retracing 
 their way over the same route, they found that they sailed 
 less rapidly than they reckoned. ‘This led them to believe 
 that the water had a motion. The great Benjamin Frank- 
 lin was the first to see the meaning of these observations 
 of the mariners, and, by studying their records, he became 
 the discoverer of the Gulf Stream. Next, after the study 
 of ships’ logs, came the exploration by means of bottles 
 
54 PRIMER OF GEOLOGY. 
 
 which were thrown into the sea, with the place and time 
 when they started on their voyage marked on a paper 
 contained within. The beginning and end of the voy- 
 ages of thousands of these bottles being determined, it 
 became easy by marking them on a map to get some idea 
 of the course of the ocean movements. 
 
 The matter can be still further impressed by taking 
 account of the carriage of material things in these ocean 
 currents. The abundant carriage of driftwood from the 
 tropical rivers to Iceland and other lands in the Arctic 
 regions of the Atlantic, and the drifting of dismasted 
 ships with their crews from the China coast to the Amer- 
 ican shore, give sensible evidence of the movement of 
 these streams. 
 
 If the teacher will picture to the student the effect of 
 destroying these currents, showing how the tropical heat 
 would become unendurable, while the temperature of the 
 regions north and south of 40° would be too cold for life, 
 he will serve to impress the action of this circulation of 
 the seas upon the pupil’s mind. It is not too much to say 
 that the currents of the sea are the condition of terrestrial 
 life as the circulation of our own blood is the condition of 
 the bodily life. 
 
CHAPTER V. 
 HILLS AND MOUNTAINS. 
 
 1 taking up the accidents of the earth’s surface, we 
 
 find ourselves in a field where the opportunities of 
 illustration are very numerous. This subject has the 
 peculiar value for the teacher, that he can show in the field 
 the most important stages of the action he desires to 
 illustrate. 
 
 The best way to begin practical illustration is by 
 showing the action of water on ordinary fields of earth. 
 Its cutting power may be seen from day to day, or from 
 hour to hour, during times of storm. In this way we can 
 illustrate the making of hills, those simplest yet most im- 
 portant features of the land. The student has then only ° 
 to suppose that the hard rock takes more time to wear 
 than the soft earth, to get the true idea of their formation. 
 If the teacher does not have access to the fields, he can 
 imitate this within, by sand and a stream of water from a 
 faucet. A little ingenuity will enable him to show all the 
 important points in the phenomena. In the field the rela- 
 tion between the streams and the hills, except in glacial 
 countries, where the hills owe their shapes to the ice, is 
 always very plain. The student, where the ground is 
 favorable, should have a chance to see this relation clearly. 
 It is one of the simplest, and, at the same time, the most 
 profitable of these large relations of forces. 
 
 It should also be noticed that this is a precious oppor- 
 tunity for enlarging the student’s conception of geological 
 time. There is perhaps no other so constant and effective 
 
56 PRIMER OF GEOLOGY. be 
 
 a reminder of the time durations of the past as this sight 
 of the hills that have slowly formed from the cutting power 
 of the streams. This conception is made the stronger if 
 the teacher will show here, that while the streams are cut- 
 ting away the basis of the hills, their summits are all the 
 while slowly wearing down, so that their height is only the 
 excess of the stream-cutting above the down-wearing of 
 their summits. If the action of the streams is large com- — 
 pared with the area of rain and frost on their summits, 
 then the hills will be high. If the wearing at base and 
 summit be nearly equal, the hills will never have much 
 relief. 
 
 When the idea of a hill structure is well ‘established, it 
 will then be well to begin the consideration of mountains. 
 It should be made clear that mountains are. hills, plus an 
 elevating force that arises from a pressing of the rocks 
 together. It is not easy to illustrate this compressive 
 action. Something can be done by the following means: 
 Take a strip of rubber, say an inch wide and a foot long; 
 stretch it six inches longer. Fasten upon its surface, by 
 means of any elastic cementing substance, a number of 
 colored strips of any flexible material; strips of clay are 
 the best. Then let the strip of rubber slowly contract. 
 The result will: be the puckering and wrinkling of the 
 inelastic layers above. 
 
 The idea of the slow upward growth of mountains, as 
 the streams plane them down, is of great value in enfore- 
 ing the essentially slow nature of the earth’s changes. 
 
 Good specimens of flexed rocks are obtainable in almost 
 any region that has crystalline strata. 
 
CHAPTER VI. 
 ORIGIN OF VALLEYS AND LAKES. 
 
 eee previous studies have prepared the student’s mind 
 
 to perceive the causes of these features in the topog- 
 raphy of the lands. Illustrations will abound in every 
 district where this book is used. Even in our cities it 
 rarely happens that a bit of river topography is not pres- 
 ent. The principal reliance of the teacher in his efforts 
 to show the operation of rivers must be on the tempo- 
 rary streams that the rain makes in every field. He will 
 there find all the phenomena on a small scale in perfect 
 completeness of exhibition. ‘There are none of the large 
 geological phenomena so well illustrated on this small 
 scale. The mountain torrent is shown in the steeper part 
 of the temporary rill. The alluvial plain, in its middle 
 part, never fails to be shown from point to point in its 
 course, and the end of the streamlet, if in a pond, will 
 show the delta structure. 
 
 The action of the waterfalls of a river may be well illus- 
 trated where there is a milldam to show the powerful blow 
 of the stream when falling from a height. When this can- 
 not be seen, the water from an ordinary hydrant falling 
 into a vessel, such as a flower-pot, will show by its action 
 on pebbles, or little bits of soft earthenware, such as the 
 fragments of a flower-pot, the energetic cutting action that 
 takes place below a fall. The formation of pot-holes can 
 be thus illustrated. This illustration will also answer for 
 the account of caverns previously given. 
 
 Finally, from the action of rivers, the student’s mind 
 
58 PRIMER OF GEOLOGY. 
 
 should be turned once again to the principles of erosion 
 and deposition. Once again it should be pointed out that 
 the lands waste into the sea, building on their floors new 
 strata, which in time may be lifted into lands, so that the 
 matter. on the earth’s surface tends to make a circle from 
 land to sea and from sea to land. 
 
 The consideration of tides can with profit be carried 
 much farther than is indicated in the text. This tidal 
 action is not easy to explain in a complete fashion, but 
 without going into the details of the subject, there is a 
 great deal of interest that can be presented to the young 
 mind. First, it may be noticed that this is one of the 
 forms of gravitation, —the same force that brings a falling 
 body to the earth, only the force is the gravity of far-off 
 spheres, —namely, the sun and moon. 
 
 It will be well to dwell upon the fact that the life of the 
 sea is mostly sedentary or fixed to the bottom, so depend- 
 ent on the movement of the water for food. On the 
 shore, the currents of wind waves serve to feed this life; 
 but in the deep seas this life is greatly dependent on the 
 motion the tide gives the sea. So, in a certain way, it 
 may be said that the far-off moon brings the food to the 
 mouths of the creatures so deeply buried in the sea that 
 its light, or the light of the sun, never reaches to them. 
 This is one of the most interesting cases of the far-reaching 
 effects in nature. 
 
 In the lesson on lakes there is not much that can be 
 done to aid the student. The teaching from salt lakes 
 may be extended a good deal with profit. Their saltness 
 may be made to explain the saltness of the sea, and to 
 illustrate more forcibly the fact that, while rain-water is 
 pure, rivers always have in their water some of the mate- 
 rials of all the rocks it has passed through. 
 
CHAPTER VII. 
 MOVEMENTS OF THE EARTH’S SURFACE. 
 
 HIS is a matter which needs all the illustration that 
 can be given to it, because the facts are against the 
 elements of ordinary experience, which is all of a nature to 
 fix the idea of the earth’s immobility. There are many 
 ways in which suggestions of its mobility in the force of 
 quakes or tremblings may be had. The beat of forging 
 hammers, quarry explosives, or even the jar of carts on 
 the stony streets, may produce slight motions which rattle 
 the windows. It will be easy to extend this idea to sway- 
 ings that can overthrow buildings and shake down the 
 monster cliffs. Even a jar made with the foot on the floor 
 will show its effects on a glass of water. The idea of the 
 propagation of compression waves through a solid will be 
 readily grasped from these illustrations. Next, the elas- 
 ticity of rocks may be illustrated by the familiar experience 
 of bouncing a large marble on a stone floor. Comparing 
 the bounce of this marble on stone with its movement 
 on a wood floor will give an idea of the extreme resilience 
 of rock. This will show how, once started, a jar will run 
 a long distance through the rocks before it wears out. 
 There is an abundant literature, out of which more 
 extented accounts of earthquakes may be taken, if they 
 are desired. Probably the best accounts for this use are 
 to be found in Lyell’s Principles of Geology, from which 
 the three selected shocks described in the text are ex- 
 tracted. 
 The observed movements of the earth that bring about 
 
60 PRIMER OF GEOLOGY. 
 
 the greater changes of the shape of lands and seas cannot 
 be illustrated by experiences of any sort. The only help 
 that can be given will be from the free use of the globe, 
 showing how the changes in the shape of the lands will 
 effect the conditions of the surface. The imagination of 
 the pupil will readily respond to this appeal, provided the 
 working of the sea currents and their effects have been 
 duly impressed upon his mind. As this trial of the imag- 
 ination practically closes the consideration of the earth’s 
 purely physical history, it should be much dwelt on, pro- 
 vided it seems fitted to the student’s mind. Nothing else 
 will so affirm the understanding of the actual conditions 
 as an effort to conceive how alterations of geography will 
 effect the action of the earth’s machinery. I confess, 
 however, to the fear that it will generally be found beyond 
 the grasp of the beginner. It is, however, surprising to see 
 how quickly children of twelve to fifteen get a hold upon 
 such problems, and how quickly the mind grows from their 
 consideration. They must be presented in the right way 
 as living things, and, as such, they claim our attention. 
 
CHAPTER VIII. 
 THE PLACE OF ANIMATED THINGS IN THE WORLD. 
 
 HIS chapter gives a difficult set of considerations, — 
 one that the teacher will find not easy to make profit- 
 able; yet, if it goes to the child’s mind, it will be extremely 
 helpful to him. The ordinary idea that life is something 
 essentially apart from the mechanism of the earth, some- 
 thing imposed upon the physical world, is a prejudice that 
 lowers the conception of the earth. Better than that 
 was the notion of the inspired Kepler, that this sphere was 
 really alive, and that the tides were the evidences of its 
 breathing, — the slow breath of the giant slumbering 
 beneath our feet. 
 
 The teacher may urge the consideration that the soil 
 stratum of the earth is constantly passing into soil out of 
 life; that this mould layer has been a thousand times 
 through the mechanism of life; that the carbon that floats 
 in the air has had a myriad living shapes; that the carbon 
 of our coal may have been through innumerable creatures, 
 plant and animal, before it went to rest beneath the earth; 
 that when we release it by burning, we set it once again 
 on its round from life to life; that death is but a turning- 
 point in life is the first and truest lesson the earth teaches. 
 
 Those who are at all familiar with the theories of classi- 
 fication will see in the lesson on this subject an effort to 
 show, in a simpler way than has heretofore been used, the 
 nature of the relations among organisms. The teacher 
 can help easily this thought by taking the more familiar 
 animals and plants, and showing a number of examples 
 
62 PRIMER OF GEOLOGY. 
 
 of affinities, such as are sketched here. Among plants, 
 the best examples are found in our rosaceous plants and the 
 nut-bearing trees, such as the oaks. These considerations 
 depend for their effective enforcement on repetition. 
 Among animals, the ordinary domesticated forms can be 
 used; better still, the birds and insects. It is not worth 
 while to attempt any very complete classification of ani- 
 mals and plants, for the detail has to be given by words, 
 and this should on principle be avoided. 
 
 The illustrations from human devices, though objection- 
 able on certain accounts, seem to simplify the idea of 
 natural classification, and give a little training in the 
 categoric method of enquiry. If the teacher has had some 
 training in the science of biology, he may profitably extend 
 the method of looking at natural objects, given here in the 
 case of the honey bee, to several other groups, so as to 
 solidify the idea. When possible, the words should in all 
 cases be illustrated by the specimen. 
 
CHAPTER IX. 
 A SKETCH OF THE EARTH’S ORGANIC LIFE. 
 
 en glance at some of the series of organic forms is 
 ~ designed to show the student how certain evident 
 series of changes were brought about. 
 
 The illustrations from the plants may be made numer- 
 ous and effective; but those from animals will be more 
 difficult to present. The most effective way of interesting 
 children in this part of the subject is by permitting them 
 to rear certain plants. A school window-garden will illus- 
 trate all the important points dwelt on in the text. The 
 association of a number of individuals into an organic 
 community is something that, at first sight, puzzles while 
 it interests the student. Facts of this sort are so numer- 
 ous in the organic world that it will be well to make the 
 matter as clear as possible. It is most clearly done in the 
 plant kingdom. The possibility of developing a tree from 
 a bud or a graft, and other gardener’s arts, all serve to 
 show the action of the communistic principle in our ordi- 
 nary plants. A comparison between a rose-bush and an 
 ordinary duckweed will show the basis of the difference. 
 The rose-bush is a multitude of buds or phytons, each of 
 which can be made to develop alone. On the other hand, 
 the duckweed consists of but one such centre of life. 
 These considerations are easily extended to compound 
 animals, such as our common coral-making polyps. 
 
 The series of contrivances for the better nutrition of 
 the seeds and otherwise aiding them is very interesting. 
 The teacher will do well to consult the works of Darwin 
 
64 PRIMER OF GEOLOGY. 
 
 for many illustrations that bear on this point. The con- 
 trivances are infinitely various. <A _ tolerably bright child 
 will take great pleasure and profit from a search for these — 
 adaptations. In the autumn, a little collection can easily 
 and profitably be made of seeds that have barbs to aid 
 them in catching into the hair or wool of animals, or the 
 floats to secure their diffusion through the air. 
 
 Attention is momentarily drawn in the text to the strik- 
 ing differences between animals and plants, as to the ends 
 they seem to seek. This matter can be carried further 
 with much profit. The habit of making just such com- 
 parisons is what we desire to breed in the mind. 
 
 In the group of protozoa and radiates there is little 
 chance of aiding the child by concrete examples, unless 
 the teacher possesses either a cabinet or a microscope. 
 Neither of these resources need be at all costly. There 
 are ‘microscopes costing fifty dollars that will serve excel- 
 lently well for such work. But for the tax which it pleases 
 this government to place on microscopes, a thoroughly 
 trustworthy instrument could be imported for about thirty 
 dollars. 
 
 A collection of protozoa cannot well be represented to 
 the naked eye, except by means of models. Only a few 
 of them are large enough to disclose their structure to the 
 naked eye. A small collection of corals and echinoderms 
 is easily and inexpensively made. A very few forms will 
 serve to show the essential principles of their structure. 
 If this practical side cannot be given to the study of the 
 animal series, this part of the book would best be studied 
 with rapidity. 
 
 Where it is possible for the teacher to use objects in 
 teaching these facts concerning animals, it will be well to 
 observe the following points: First, to begin the illustra- 
 
A SKETCH OF THE EARTH’S ORGANIC LIFE. 65 
 
 tion of the extinct creation by carefully showing some 
 recent form, if possible, living; if not, in the best state of 
 preservation. Something of the habits and mental quali- 
 ties of this living form should be given. Then, from this 
 foundation, the student should be led back into the realm 
 of ancient life. Thus, before speaking of these ferns and 
 other cryptogams of the carboniferous period, a little pre- 
 sentation of our living ferns and horse-tails should be 
 given. Before speaking of the fossil reptiles, our living 
 kindred forms should be brought plainly to mind by 
 descriptions and specimens. In following this way the 
 teacher will always be proceeding on the true search for 
 the path from the known to the unknown. 
 
 The protozoa and radiates are almost inaccessible to 
 the ordinary observer, unprovided with collections or 
 microscopes. The molluscs, on the other hand, can be 
 very easily studied from the specimens accessible in our 
 brooks and fields, except the cephalopods, specimens of 
 which are generally to be found along the shores. An 
 ordinary fresh-water aquarium, even if it be limited to a 
 large jar or a milk pan, will serve to keep our ordinary 
 fresh-water mussels alive; and if salt water is obtainable, 
 the shores will furnish a host of interesting forms to place 
 in it. 
 
 The detailed anatomy of animals cannot be profitably 
 taught to young pupils. The simplest functions alone can 
 be noticed. The methods of progression, the periods of 
 obtaining food, breathing, and, in some cases, of reproduc- 
 tion, can alone be treated by the teacher. 
 
 At the outset the teacher will find himself under the 
 need of determining what method he will take in dealing 
 with the reproductive system of animals. ‘This is a sub- 
 ject about which it is very difficult to give advice that can 
 
66 PRIMER OF GEOLOGY. 
 
 be uniformly followed. It is not worth while to dictate 
 as to the general policy of making questions of this sort a 
 forbidden field for the student. ‘This practice is so fixed 
 in our social usages that it is not worth while to consider 
 its policy. The teacher will always find that almost all 
 the children from decent families have been brought up 
 with the idea that it was indelicate to consider such mat- 
 ters. My own preference is in favor of a perfectly free 
 teaching of those points, beginning with the reproduc- 
 tive systems of plants, and then going straight forward 
 through the animal kingdom. Fortunately, the parts of 
 this subject that are important are limited to the more 
 general facts. Only in the viviparous animals, especially 
 the mammals, is there any ground where there can be any 
 tisk in this open method of treatment. The fact of the 
 young being born alive, the nature and important relations 
 of the placenta and mammae to the development of the 
 young,—these points should, I think, be treated with per- 
 fect frankness, and will, I think, so far from proving inju- 
 riously suggestive to the child, prove cleansing and whole- 
 some in their effects. It is perfectly certain that chil- 
 dren’s minds are generally dangerously full of sexual 
 ideas. This course of plain teaching will, by example, 
 teach them to look upon such matters as things of course, 
 to be treated as simply as other facts in nature. If the 
 teacher feels that this method of proceeding is not pos- 
 sible, then the only plan is to omit all consideration of 
 this subject. 
 
 The group of articulates is of all the groups of animals 
 the most convenient for the use of the teacher of zodlogy. 
 Its most interesting forms, the insects, are the tenants of 
 the land, and are the most abundant and varied of ani- 
 mals. The complications of the insect’s structure are so 
 
A SKETCH OF THE EARTH’S ORGANIC LIFE. 67 
 
 great that it is not advisable that anything beyond the 
 outlines should be given to students. Beyond these, the 
 attention should be devoted to the habits of insects, and 
 the outline of their structure will come into the memory 
 from the study of those habits. An admirable store of 
 facts concerning those habits will be found in Mr. Ro- 
 mane’s capital book on animal intelligence. 
 
 The teacher may be sure of a singular attention from 
 his pupils for all that he may be willing to give them con- 
 cerning the habits of insects. It is often very useful to 
 start the students on the way of keeping and observing 
 insects. ‘The changes from the caterpillar to the chrysalis, 
 and thence to the butterfly stage, can easily be made 
 the matter of experiment. Perhaps the most interesting 
 creatures for such studies are our common spiders. Being 
 creatures of solitary habits, and moderately long-lived, 
 they may be readily kept in glass jars, where their habits 
 of catching prey, their spinning habits, etc., may be mod- 
 erately well observed. Better by far than any experi- 
 ments on captive forms are the observations made on the 
 creatures in their natural state. The student should be 
 urged to observe the field life of some one kind of insect. 
 For this field work the ants afford perhaps the best forms 
 for study, but boys are more easily interested in spiders or 
 the groups of wasps, perhaps because of the combative 
 humor of these creatures. The modern glass beehives 
 afford by all odds the most charming means of observation 
 that can be had by the student of insects. When it is 
 possible to show the students something of bees, the 
 chance should not be lost. 
 
 In the group of vertebrates, the chance of complete 
 illustration of the zodlogical succession of the forms is 
 excellent. The fishes, amphibians, reptiles, birds, and 
 
68 PRIMER OF GEOLOGY. 
 
 mammals are more or less well shown on every hundred 
 square miles of this country. The teacher will find it 
 advantageous to confine the illustrations, as far as pos- 
 sible, to the domesticated forms of animals or familiar 
 wild birds. Suggestions concerning birds that may be 
 useful for immediate reference may be found in the 
 appendix. 
 
 CHAPTER X. 
 FOSSILIZATION. 
 
 FTER the conception of living creatures and their 
 
 ancient kindred have been fully presented to the 
 student, it will be found that he will take an interest 
 in the process of fossilization described in Chapter X. 
 This is sufficiently treated in the text; the only need is 
 of illustration. If the teacher has any access at all to 
 specimens of petrified animals, it will be very easy to give 
 all necessary illustration of the process. 
 
CHAPTER XI. 
 THE ORIGIN OF ORGANIC LIFE. 
 
 sie is not possible to give even the most elementary 
 
 account of the earth’s features without saying some- 
 thing concerning the origin of organic forms. It is not 
 necessary to say that the treatment of this subject is a 
 matter of singular dithculty, not only on account of the 
 shadowy nature of the problem, but because of the popu- 
 lar prejudice that surrounds the matter. I believe that 
 the statement given in the text-book is sufficiently com- 
 plete to fix in the student’s mind the essential points of 
 the modern view, provided the teacher will enforce with 
 ample illustration the considerations on which it rests. 
 The most important point to make clear is the surplusage 
 of life in each generation. To give this its full power, 
 illustrations should be drawn from each important group 
 in the animal kingdom. Next, the way in which our 
 domesticated breeds of animals and plants are formed 
 should be made clear to the student. Then the battle for 
 existence, with its consequence —the survival of the fittest 
 —should be dwelt on. 
 
 It cannot be hoped that these considerations will have 
 their weight with young people; yet, if they are carefully 
 explained and reiterated, there is some reason to hope that 
 the pupils will have that which is denied the mass of 
 men,—some distinct notions concerning the Darwinian 
 hypothesis. 
 
 I think it well, in presenting this theory, to dwell upon 
 the evident fact that the result of these changes is not a 
 
70 PRIMER OF GEOLOGY. 
 
 haphazard in nature; that even if the means whereby 
 animals and plants become what they are, be thus simple 
 and apparently mechanical, the result is a beautiful order 
 and purposefulness in the order. Evolution does not 
 explain this order: it only shows the immediate means 
 whereby the order has come about. 
 
 The proof that the world is very old is one that is very 
 hard to bring into a clear shape, even to the best-trained 
 mind. The difficulty is not in getting a consent to the 
 argument, but a conception of time, the most elusive of 
 all ideas. The most that can be done is to put the truths 
 clearly and forcibly into the mind, as we put seed into the 
 eround, leaving the fruit to come in its way and time. 
 The succeeding chapter will call for a frequent exercise of 
 this effort to conceive past time. The teacher can do some- 
 thing to actualize the impressions by again and again call- 
 ing attention to the illustrations given in the text, where 
 an effort is made to illustrate the duration of time by the 
 simpler and more conceivable notion of distance. I have 
 found this analogy more effective than any other that has 
 been suggested. 
 
CHAPTER XII. 
 
 A BRIEF ACCOUNT OF THE SUCCESSION OF EVENTS ON 
 THE EARTH’S SURFACE. 
 
 eS chapter begins with a brief account of the nebu- 
 
 lar hypothesis. If the teacher will make use of the 
 heavens, especially if he be able to command the use of a 
 small telescope, he may show the rings of Saturn, and so 
 give a novel solidity to the idea of growth by the forma- 
 tion of rings, and their breaking up and consolidating into 
 spheres. If he cannot do better, let him get from any 
 astronomy an idea of nebule, and show their structure to 
 the class. 
 
 It is hardly worth while to do more than exhibit this 
 simple skeleton of that part of the earth’s history which 
 lies in the realm of shadowy things. I find that intelli- 
 gent youths demand some resting-ground for their feet in 
 this obscure part, and this has the advantage that was of 
 old found in imagining the earth to rest on an elephant, 
 and the elephant to stand on a tortoise. 
 
 In the lessons on the history of organic life, the teacher 
 will find that the time to be given with profit will depend 
 on his having some means of illustration. 
 
 A very small collection of fossils will go far to give an 
 actuality to the statements made in this part of the text. 
 Something can be done by pictures of fossils, but the task 
 of giving solidity and actuality to an idea presented by a 
 picture, however good, is one that is not possible for the 
 ordinary student to effect. It will be observed that the 
 text gives constant reference to the existing life. This is 
 
yy PRIMER OF GEOLOGY. 
 
 the only method in which the interest of the student in 
 these things of the old world canbe kept alive. It must 
 be used at every step. In the case, for instance, of the 
 horse, it can be made to give life and meaning to the 
 singular chapter of the paleontological record in which 
 the history of that animal’s ancestry is written. 
 
 The appendix to the book gives some outlines of the 
 subject of mineralogy. This was omitted in the body 
 of the work, because it is not necessarily connected with 
 the things which it seemed desirable to teach in that 
 place. It is given here, in order that those teachers who 
 desire to do so may make it a part of their instruction. | 
 Although it gives but the merest outlines of the subject, | 
 it will be impossible to present it with any satisfactory 
 results, without some illustration by means of specimens. 
 
 The student should have it well impressed on his mind 
 that each mineral species usually has many variations of 
 its crystalline forms, only one or two of which are given 
 here. . 
 
 The best introduction to this study of the mineral side 
 of geology can be given by a few hours in a field, where 
 the student can be shown the composition of rocks in a 
 general way: how some rocks are crystalline, whilst others 
 show no trace of crystals: how dykes and veins occur, 
 and how the crystals are blended with them. This per- 
 ception of the general conditions of occurrence of erys- 
 tals should precede the study of their structure and form, 
 just as the botanist, who would do well by his students, 
 should first go with them to the field for the plants, in 
 order that he may secure a chance, to show the essential 
 beauty manifested in their natural places and connections. 
 
 The teacher will also find it profitable to trace out the 
 uses of many of those substances mentioned. A little de- 
 
SUCCESSION OF EVENTS. to 
 
 scription of the method of making glass may be given 
 with the account of quartz, or something of the processes 
 of mining gold, when that metal is mentioned. 
 
 In closing these directions to teachers, I feel it my duty 
 to say, that they seem to me, on the whole, unsatisfactory. 
 Their defects arise in part from the want of experience of 
 a profitable sort in all departments of pedagogic art; but 
 in larger degree from the difficulty that arises from the 
 wide differences of condition that environ teachers in dif- 
 ferent places. The directions that are put for one geo- 
 eraphical position are unfit for another. Something of 
 this difficulty of position may be remedied by means of 
 collections designed for teaching which shall give a cer- 
 tain uniformity to the home work. 
 
 To meet this need the writer is now engaged in prepar- 
 ing a collection for the uses of schools, which shall, by 
 means of specimens of living animals, fossils, models, pic- 
 tures, and other adjuncts, furnish a certain common basis 
 for the illustration of the principal points touched upon 
 in this treatise, and in the book which it accompanies. 
 
 In closing this essay, [ invite the teacher who may read it 
 to regard it as an appeal for another and a better form of 
 teaching in science than that commonly in use in our 
 schools. If this better manner is to be attained, it must 
 be by the teachers becoming the interpreters of nature, 
 relegating the books to a very subordinate position. 
 
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FHTISTORY. 
 
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 Hawthorne and Lemmon’s American Literature. A manual for high schools 
 and academies. $1.25. 
 
 Meiklejohn’s History of English Language and Literature. For high schools 
 and colleges. A compact and reliable statement of the essentials. go cts. 
 
 Hodgkins’ Studies in English Literature. Gives full lists of aids for laboratory 
 
 method. Scott, Lamb, Wordsworth, Coleridge, Byron, Shelley, Keats, Macaulay: 
 Dickens, Thackeray, Robert Browning, Mrs. Browning, Carlyle, George Eliot, Tenny- 
 son, Rossetti, Arnold, Ruskin, Irving, Bryant, Hawthorne, Longfellow, Emerson, 
 Whittier, Holmes, and Lowell. A separate pamphlet on each author, Price 5 cts. each, 
 or per hundred, $3.00; complete in cloth $1.00, 
 
 Scudder’s Shelley’s Prometheus Unbound. With introduction and copious 
 notes. 7octs. 
 
 George’s Wordsworth’s Prelude. Annotated for high school and college. Never 
 before published alone. $1.25. 
 
 George’s Selections from Wordsworth. 168 poems chosen with a view to illustrate 
 the growth of the poet’s mind and art. $1.50. 
 
 George’s Wordsworth’s Prefaces and Essays on Poetry. Contains the best of 
 Wordsworth’s prose. 60 cts. 
 
 George’s Webster’s Speeches. Nine select speeches with notes. $1.50. 
 George’s Burke’s American Orations. Cloth. 65 cts. 
 
 George’s Select Poems of Burns. 118 poems, with introduction, notes and gloss- 
 ary. $1.00. 
 
 George’s Tennyson’s Princess. With introduction and notes. 45 cts. 
 
 Corson’s Introduction to Browning. A guide to the study of Browning’s Poetry. 
 Also has 33 poems with notes. $1.50. 
 
 Corson’s Introduction to the Study of Shakespeare. A critical study of 
 Shakespeare’s art, with examination questions. $1.50. 
 
 Cook’s Judith. The Old English epie poem, with introduction, translation, glossary and 
 fac-simile page. $1.60. Students’ edition without translation. 35 cts. 
 
 Cook’s The Bible and English Prose Style. Approaches the study of the Bible 
 from the literary side. 60 cts. 
 
 Simonds’ Sir Thomas Wyatt and his Poems. 168 pages. With biography, and 
 critical analysis of his poems. 785 cts. 
 
 Hall’s Beowulf. A metrical translation. $1.00. Students’ edition. 35 cts 
 
 Norton’s Heart of Oak Books. A series of six volumes giving selections frem the 
 choicest English literature. 
 
 See alse our list of books for the study of the English Language. 
 
 D. C. HEATH & CO., PUBLISHERS. 
 BOSTON, NEW YORK, CHICAGO. 
 
CIVICS, ECONOMICS, AND SOCIULOGY. 
 
 Boutwell’s The Constitution of the United States at the End of the Firs! 
 Century. Coutains the Organic Laws of the United States, with references to the 
 decisions of the Supreme Court which elucidate the text, and an historical chapter re- 
 viewing the steps which led to the adoption of these Organic Laws. / press. 
 
 Dole’s The American Citizen. Designed asa text-book in Civics and morals for the 
 higher grades of the grammar school as well as for the high school and academy. Con 
 tains Constitution of United States, with analysis. 336 pages. $1.00. 
 
 Special editions are made for Illinois, Indiana, Ohio, Missouri, Nebraska, No. Dakota, 
 So. Dakota, Wisconsin, Minnesota, Kansas, Texas. 
 
 Goodale’s Questions to Accompany Dole’s The American Citizen. Con- 
 tains, beside questions on the text, suggestive questions and questions for class debate. 
 87 pages. Paper. 25 cts. 
 
 Gide’s Principles of Political Economy. Translated from the French by Dr. 
 Jacobsen of London, with introduction by Prof. James Bonar of Oxford. 598 
 pages. $2.00. 
 
 Henderson’s Introduction to the Study of Dependent, Defective, and 
 Delinquent Classes. Adapted for use as a text-book, for personal study, for 
 teachers’ and ministers’ institutes, and for clubs of public-spirited men and women engagea 
 in considering some of the gravest problems of society. 287 pages. $1.50. 
 
 Hodgin’s Indiana and the Nation. Contains the Civil Government of the State, 
 as well as that of the United States, with questions. 198 pages. 70 cts. 
 
 Lawrence’s Guide to International Law. A brief outline of the principles and 
 practices of International Law. Jn press. 
 
 Wenzel’s Comparative View of Governments. Gives in parallel columns com- 
 parisons of the governments of the United States, England, France, and Germany. 26 
 pages. Paper. 22 cts. 
 
 Wilson’s The State. Elements of Historical and Practical Politics. A text-book on 
 the organization and functions of government for high schools and colleges. 720 pages. 
 + §$2.00. 
 
 Wilson’s United States Government. For grammar and high schools. 140 pages. 
 60 cts. 
 
 Woodburn and Hodgin’s The American Commonwealth. Contains several 
 orations from Webster and Burke, with analyses, historical and explanatory notes, ana 
 studies of the men and periods. 586 pages. $1.50. 
 
 Sent by mati, post paid on receiptof prices. See also our list of books in History. 
 
 D. C. HEATH & CO., PUBLISHERS, 
 BOSTON. NEW YORK. CHICAGO. 
 
SCLIN GL: 
 
 Shaler’s First Book in Geology ¢ For high school, or highest class in grammar 
 school. $1.10. Bound in boards for supplementary reader. 70 cts. 
 
 Ballard’s World of Matter. a Guide to Mineralogy and Chemistry. $1.00. 
 
 Shepard’s Inorganic Chemistry. Descriptive and Qualitative ; experimental and 
 inductive; leads the student to observe and think, For high schools and colleges. $1.25. 
 
 Shepard’s Briefer Course in Chemistry; with Chapter on Organic 
 Chemistry. Designed for schools giving a half year or less to the subject, and schools 
 limited in laboratory facilities. go cts. 
 
 Shepard’s Organic Chemistry. The portion on organic chemistry in Shepard’s 
 Briefer Course is bound in paper separately. Paper. 3o0cts. 
 
 Shepard’s Laboratory Note-Book. Blanks for experiments: tables for the re 
 actions of metallic salts. Can be used with any chemistry. Boards. 40 cts. 
 
 Benton’s Guide to General Chemistry. A manual for the laboratory. 40 cts. 
 
 Remsen’s Organic Chemistry. An Introduction to the Study of the Compounds 
 of Carbon. For students of the pure science, or its application toarts. $1.30. 
 
 Orndorff’s Laboratory Manual. Containing directions fora course of experiments 
 in Organic Chemistry, arranged to accompany Remsen’s Chemistry. Boards. 40 cts. 
 
 Coit’s Chemical Arithmetic. with a short system of Elementary Qualitative 
 Aunalysie For high schools and colleges. 60 cts. 
 
 Grabfield and Burns’ Chemical Problems. For preparatory schools. 60 cts. 
 
 Chute’s Practical Physics. A laboratory book for high schools and colleges study- 
 ing pnysics experimentally. Gives free details for laboratory work. $1.25. 
 
 Colton’s Practical Zoology - Gives a clear idea of the subject as a whole, by the 
 careful study of a few typical animals. go cts. 
 
 Boyer’s Laboratory Manual in Elementary Biology. A guide to the 
 study of animals and plants, and is so constructed as to be of no help to the pupil unless 
 he actually studies the specimens. 
 
 Clark’s Methods in Microscopy. This book givesin detail descriptions of methods 
 that will lead any careful worker to successful results in microscopic manipulation. $1.60. 
 
 Spalding’s Introduction to Botany. Practical Exercises in the Study of Plants 
 by the laboratory method. go cts. 
 
 Whiting Ss Physical Measurement. Intended for students in Civil, Mechani- 
 cal and Electrical Engineering, Surveying, Astronomical Work, Chemical Analysis, Phys- 
 ical Investigation, and other branches in which accurate measurements are required. 
 
 I. Fifty measurements in Density, Heat, Light, and Sound. $1.30. 
 II. Fifty measurements in Sound, Dynamics, Magnetism, Electricity. $1.30. 
 III. Principles and Methods of Physical Measurement, Physical Laws and Princi- 
 , ples, and Mathematical and Physical Tables. $1.30. , 
 IV. Appendix for the use of Teachers, including examples of observation and re- 
 duction. Part IV is needed by students only when working without a teacher. 
 
 $1.30. 
 Parts I-III, in one vol., $3.25. Parts I-IV, in one vol., $4.00. 
 
 Williams’s Modern Petrography. An account of the application of the micro 
 scope to the study of geology. Paper. 25 cts. 
 
 For elementary works see our list of books in Elementary Science, 
 
 D. C. HEATH & CO., PUBLISHERS. 
 BOSTON. NEW YORK. CHICAGO. 
 
ELEMENTARY SCIENCE. 
 
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 Bailey’s Grammar School Physics. A series of inductive lessons in the elements 
 of the science. Illustrated. 60 cts. 
 
 Ballard’s The World of Matter. A guide to the study of cnemistry and mineralogy; 
 adapted to the general reader, for use as a text-book or as a guide to the teacher in giving 
 object-lessons. 264 pages. Illustrated. $1.00. 
 
 Clark’s Practical Methods in Microscopy. Gives in detail descriptions of methods 
 that will lead the careful worker to successful results. 233 pages. Illustrated. $1.60. 
 
 Clarke’s Astronomical Lantern. Intended to familiarize students with the constella- 
 tions by comparing them with fac-similes on the lantern face. With seventeen slides, 
 giving twenty-two constellations. $4 50. 
 
 Clarke’s How to find the Stars.. Accompanies the above and helps toan acquaintance 
 with the constellations. 47 pages. Paper. 15 cts. 
 
 Guides for Science Teaching. Teachers’ aids in the instruction of Natural History: 
 classes in the lower grades. 
 I. Hyatt’s About Pebbles. 26 pages. Paper. 1o cts. 
 II. Goodale’s A Few Common Plants. 61 pages. Paper. 20 cts. 
 III. Hyatt’s Commercial and other Sponges. Illustrated. 43 pages. Paper. 20 cts. 
 IV. Agassiz’s First Lessons in Natural History. Iiustrateds 64 pages. Paper. 
 25 Cts. 
 Vv, Hyatt’ ’s Corals and Echinoderms. Illustrated. 32 pages. Paper. 30 cts. 
 VI. Hyatt’s Mollusca. Illustrated. 65 pages. Paper. 30 cts. 
 VII. Hyatt’s Worms and Crustacea. Illustrated. 68 pages. werer 30 cts. 
 VIII. Hyatt’s Insecta. Illustrated. 324 pages. Cloth. $1.25 : 
 XII. Crosby’s Common Minerals and Rocks. Illustrated. 200 pages. Paper, go 
 cts. Cloth, 60 cts. 
 XIII. Richard’s First Lessons in Minerals. 50 pages. Paper. 1o cts. 
 XIV. Bowditch’s Physiology. 58 pages. Paper. 20 cts. 
 XV. Clapp’s 36 Observation Lessons in Minerals. 80 pages. Paper. 30 cts. 
 XVI. Phenix’s Lessons in Chemistry. 20 cts. 
 Pupils’ Note-Book to accompany No. 15. 10 cts. 
 
 Rice’s Science Teaching in the School. With a course of instruction in science 
 for the lower grades. 46 pag-s. Paper. _25 cts. 
 
 Ricks’s Natural History Object Lessons. Supplies information on plants and 
 their products, on animals and their uses, and gives specimen lessons. Fully illustrated. 
 332 pages. $1.50. ¢ : 
 
 Ricks’s Object Lessons and How to Give them. 
 Volume I. Gives lessons for primary grades. 200 pages. go cts. 
 Volume II. Gives lessons for grammar and intermediate grades. 212 pages. go cts. 
 
 Shaler’s First Book in Geology. For high school, or highest class in grammar school, 
 272 pages. Illustrated. $1.00. © 
 
 Shaler’s Teacher’s Methods in Geology. An aid to the teacher of Geology. 
 74 pages. Paper. 25 cts. 
 
 Smith’s Studies in Nature. A combination of natural history lessons and language 
 work. 48 pages. Paper. 15 cts. 
 
 Sent by mail postpaid on receipt of price. See also our list of books im Science 
 
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 BOSTON. NEW YORK. CHICAGO. 
 
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