IK ME/ 
 
 John 
 
 ^MAM 
 Swett 
 
 
GEOLOGICAL 
 
 OR, 
 
 THE RUDIMENTS OF GEOLOGY 
 
 FOR YOUNG LEARNERS. 
 
 BY ALEXANDER WINCHELL, LL.D., 
 
 PROFESSOR OF GEOLOGY AND PALAEONTOLOGY IN THE UNIVERSITY OF MICHIGAN. 
 FORMERLY DIRECTOR OF THE GEOLOGICAL SURVEY OF MICHIGAN. 
 AUTHOR OF "SKETCHES OF CREATION, 1 ' "WORLD LIFE," 
 ETC.. ETC. 
 
 Science-teaching should begin early in the school-course. 
 
 PRESIDENT ELIOT, Harvard University. 
 
 CHICAGO: 
 
 S. C. GRIGGS AND COMPANY. 
 
 1884. 
 

 COPYRIGHT, 1884, 
 
 BY 8. C. GRIGGS AND COMPANY. 
 i|Oh D 
 
 E^Hf^yaaaj 
 
CONTENTS. 
 
 PAOB 
 
 PREFATORY NOTE I 
 
 A WORD WITH THE TEACHER 5 
 
 i 
 SOME PRACTICAL SUGGESTIONS 
 
 STANDARD SAMPLES OF MINERALS AND ROCKS ... 11 
 
 EXCURSION I. In the Garden. 
 
 ORGANIC AND INORGANIC . 13 
 
 EXCURSION II. In the Garden and Field. 
 
 BOULDERS AND SAND 15 
 
 EXCURSION III. To the Gravel Bank. 
 
 THE DRIFT 21 
 
 EXCURSION IV. To Another Gravel Bank. 
 
 SPRINGS AND WELLS 26 
 
 EXCURSION V. To Our Laboratory. 
 
 How THINGS ARE PUT TOGETHER 30 
 
 EXCURSION VI. To the Field. 
 
 QUARTZ 36 
 
 iii 
 
 f>4 \ V I 
 
iv CONTENTS. 
 
 EXCURSION VII. To the Field. 
 
 THE FELDSPARS 40 
 
 EXCURSION VIIL To the Field. 
 
 CALCITE 46 
 
 EXCURSION IX. To the Field. 
 
 THE MICAS, HORNBLENDE AND TALC 50 
 
 EXCURSION X. Among the Boulders. 
 
 QUARTZOSE ROCKS 54 
 
 EXCURSION XI. Among the Boulders. 
 
 MICACEOUS ROCKS 57 
 
 EXCURSION XII. With the Stone Cutter. 
 
 HORNBLENDIC ROCKS 62 
 
 EXCURSION XIIL To the Marble Yard. 
 
 CALCAREOUS ROCKS 69 
 
 EXCURSION XIV. To the Clay Pit and the Field. 
 
 ARGILLACEOUS ROCKS 74 
 
 EXCURSION XV. To the Specimen Drawers. 
 
 EXERCISES IN IDENTIFICATIONS 78 
 
 EXCURSION XVI. By the Waterside. 
 
 SEDIMENTS 81 
 
 EXCURSION XVII. In the Gorge. 
 
 DECAY AND EROSION OF ROCKS ...... 87 
 
CONTENTS. V 
 
 EXCURSION XVIII. At the Rocky Ledge. 
 
 STRATA AND SYSTEMS OF STRATA . 95 
 
 EXCURSION XIX. To the Diagrams. 
 
 How THE STRATA ENWRAP THE EARTH .... 101 
 
 EXCURSION XX. To the Geological Map. 
 
 How TO UNDERSTAND A GEOLOGICAL MAP . . . 109 
 
 EXCURSION XXL To the Geological Map. 
 
 GEOLOGICAL SECTIONS ......... 116 
 
 EXCURSION XXIL To the White Mountains. 
 
 THE Eozoic ROCKS . 123 
 
 EXCURSION XXIII. To the Upper Mississippi. 
 
 CAMBRIAN (OR LOWER SILURIAN) ROCKS AND HISTORY 131 
 
 EXCURSION XXIV. To Niagara Falls. 
 
 SILURIAN ROCKS AND HISTORY 140 
 
 EXCURSION XXV. To Mackinac. 
 
 DEVONIAN ROCKS 146 
 
 EXCURSION XXVI. To Burlington, Iowa. 
 
 THE LOWER CARBONIFEROUS ROCKS 153 
 
 EXCURSION XXVII. To the Coal Mines. 
 
 THE COAL MEASURES 160 
 
 EXCURSION XXVIII. To Selma, Alabama. 
 
 THE MESOZOIC ROCKS . 168 
 
CONTENTS. 
 
 EXCURSION XXIX. To Claiborne, Alabama. 
 
 THE TERTIARY FORMATIONS 173 
 
 EXCURSION XXX. To the ftiver Valley. 
 
 QUATERNARY FORMATIONS 178 
 
 EXCURSION XXXI. To Switzerland. 
 
 ABOUT GLACIERS 185 
 
 EXCURSION XXXII. Through the Ages. 
 
 ABOUT THE PLANTS AND ANIMALS OP THE PAST . 191 
 
 QUESTIONS ON THE TEXT 202 
 
PREFATORY NOTE. 
 
 ADDRESSED TO TEACHERS AND SCHOOL OFFICERS. 
 
 r I lHAT the elements of geology are so seldom taught either in 
 -L. our primary or secondary schools is a circumstance to be 
 regretted. No tendency seems manifest toward any improvement 
 in this particular. In Michigan, which enjoys a justly high repu- 
 tation for the excellence of its schools and teaching, even less 
 geology is studied in school than was customary a dozen years 
 ago. No knowledge whatever of this subject is required for 
 entrance into the University of Michigan in the " Classical 
 Course," nor in the " Scientific Course," nor in the so-called 
 " English Course " though in the last two courses the candidate 
 is given his option between preparation in Chemistry, Geology, 
 Zoo'logy and Physiology. Of necessity, Physiology, which is 
 generally taught in the schools, is almost always the chosen sub- 
 ject, though next to this stands Chemistry. Practically, there- 
 fore, the study of geology in the University begins with the 
 elements in every course. A similar state of things exists in 
 most of our colleges. There is no course where geology is a 
 prerequisite, so that the student on entering may find himself in 
 position to push on to some advanced knowledge of the subject. 
 One would anticipate that a course specifically denominated 
 " Scientific," would demand a more extended scientific prepara- 
 tion than the old " Classical " course, and that a science which 
 has done as much for industry, civilization and culture as geology 
 has, would not fail to be enumerated among the requirements. 
 
 Since geology is not so required for entrance into college, it 
 has ceased to be taught in the schools as if geology had no 
 
 i 
 
% PKEFATORY NOTE. 
 
 uses if not demanded as a preparation for college. This seems 
 to the present writer a greater mistake than the other. For 
 assuredly, the large majority of pupils, not expecting the oppor- 
 tunity for collegiate study of the science, have reason to com- 
 plain that they must be deprived altogether of the opportunity 
 to learn even the nature of the subject. When they enter upon 
 the affairs of adult life, and especially, if they mingle in the 
 intellectual life of the age, they find living questions agitating 
 the world, before which they must remain dumb and uninformed, 
 because their merits are rooted in the great facts of the earth's 
 history and the history of life. 
 
 Such life-long ignorance of geology is quite as unnecessary as 
 deplorable. The elements of the science are not a body of 
 principles difficult to master, nor encumbered with a greater 
 number of scientific terms than the sciences of physiology, 
 chemistry and botany. The data of geology, moreover, lie all 
 about us, and are the most obtrusive and noticeable of all the 
 objects which we daily encounter. Stones and rocks never fail 
 to awaken the curiosity of the boy or girl; and there are few 
 children who have not made collections of stones, distinguishing 
 their varieties by precisely the same characters as the most expert 
 student. Assuredly, it seems a dictate of educational philosophy 
 to take a hint from these childish predispositions and aptitudes, 
 and shape the child's education with some regard to what he 
 seems peculiarly fitted to study. 
 
 But, however appropriate and useful this study, where are the 
 teachers who will properly lead the pupil? They are exceedingly 
 few in number. As geology is not taught in the schools, and as 
 nineteen-twentieths of our teachers have not studied it in college, 
 there is almost no preparation among the teachers of primary 
 and secondary grades to induct a pupil into an elementary knowl- 
 edge of the subject. In this state of the case, it would seem 
 very difficult to begin the desired improvement. 
 
 To the writer, the only hope of early reform seems to lie in 
 furnishing teachers with a text book so framed as to be capable 
 
PREFATORY NOTE. 3 
 
 of successful use by a teacher without previous acquaintance 
 with the subject. Certainly, no such text books exist; for, 
 though there are several which might be employed by teachers 
 thoroughly disciplined by previous study, the large majority of 
 our teachers are not so disciplined, and it may not be necessary; 
 and these text books, moreover, are too much conformed to the 
 dogmatic or didactic method telling about things which are far 
 away, or, if near at hand, are not identifiable by the aid of the 
 book. Due discrimination is not observed between those concep- 
 tions of the subject which are abstract and beyond the reach of 
 the young pupil, or older novice, and those which can be attained 
 through accessible concrete illustrations. Many of them are 
 good systematic presentations of the subject, but they are pro- 
 nounced "dry" and unintelligible. They are, in truth, too sys- 
 tematic and too complete. 
 
 The present author has pursued a fundamentally different 
 plan, and hopes he has prepared a primer of geology so simple 
 and so intelligible that no previous preparation of the teacher 
 will be needed. Hence any teacher who will pursue the method 
 will obtain an insight into the subject, and will be able, also, to 
 lead pupils of very tender years. One lesson which the author 
 has learned from much experience is here applied. The beginner, 
 especially if young, retains, as the result of his first course of 
 study in any subject, a surprisingly small amount of tangible and 
 available information. This is the author's first principle of pro- 
 cedure. His second is, to enlist the senses and the sentiments. 
 Hence the method is essentially inductive; the book speaks to 
 the pupil in the second person ; it leads to the application of each 
 item of knowledge in some useful or interesting relation, and 
 seeks to awaken the thought of the learner. 
 
 More specifically, it directs a large amount of attention to the 
 pebbles and stones so abundant everywhere in the drift of the 
 northern states; and to the phenomena of sedimentation and 
 erosion everywhere accessible. From these most familiar illus- 
 trations, it passes to the phenomena of stratified rocks and the 
 
4 PREFATORY NOTE. 
 
 way they are arranged upon the earth. Here much use is made 
 of maps and sections, as these train the learner to the indispen- 
 sable conceptions of superposition, succession, continuity and 
 discontinuity. Not much is said about purely systematic geology, 
 and still less about palaeontology and geological theory. These 
 divisions of the subject are more abstract and complicated, and 
 ought to be deferred till some familiarity is acquired with the 
 conceptions capable of illustration from familiar facts and 
 phenomena. Then much stress is laid upon the " Exercises." 
 These are not mere questions on the text. The answers to many 
 of the questions are only inferences from statements in the text. 
 Some are practical applications. Frequently the question leads 
 to an extension of knowledge. Some questions are asked which 
 will require considerable reflection some even, which cannot be 
 answered categorically. It is intended that the pupil shall keep 
 the question in mind, and search for the proper answer by asking 
 his elders, by consulting books or by exploring in collections of 
 specimens. It is profitable to have something to ponder over. 
 
 There is not a great amount of science imparted. It is sur- 
 prising often discouraging, to observe how limited is the total 
 amount of exact knowledge acquired even by older students after 
 a more thorough course. It is also an interesting fact that a 
 very little knowledge, if it is fundamental, and fully mastered by 
 viewing it from all sides, will serve to answer a very large number 
 of common inquiries. It is also true that a good deal of verbiage 
 is employed. Many sentences add nothing to the statement of 
 facts. They are intended simply to control attention and keep 
 alive the pupil's interest. 
 
 The very gist of the method is, that the pupil shall do all that 
 is indicated, and positively see every thing that is described, as 
 far as possible. Great efforts must be made to render this pos- 
 sible. Just so far as anything must be studied about, without 
 the opportunity to handle and examine it, and make drawings of 
 it, so far the pupil is unfortunate; so far the plan of the book is 
 not brought into practice. 
 
A WORD WITH THE TEACHER. 5 
 
 A large part of these " Excursions " has been used in actual 
 trials by actual teachers, while yet in manuscript. The result 
 encourages the hope that they may be found suited to the object 
 set forth, and may thus become instrumental in diffusing knowl- 
 edge and appreciation of a branch of science as accessible as any, 
 and as fruitful as any in results of high value in the industries 
 and culture of modern civilization. 
 
 This primer is, therefore, commended to the candid considera- 
 tion of teachers and school officers, in the hope that they already 
 feel the desirability of early instruction in geology, and may be 
 disposed to join with the author in testing the value of the method 
 which is here proposed. 
 
 A WORD WITH THE TEACHER. 
 
 Here, ladies, is a little book in which I hope you will be 
 interested. I address you, because nearly all the teachers of 
 those for whom the book is suitable are women; and also because 
 I have found women especially interested and apt in the studies 
 which are here introduced. The book is thought to be so simple 
 that it will literally " teach of itself," if you let it have its way. 
 So you need not be deterred from forming a little class in 
 "geology" in consequence of having geology omitted from your 
 own education. It is, I confess, too childish in style for your 
 own use as a learner ; but please consider that you are not the 
 pupil only so far as you may find it desirable to become a 
 pupil. 
 
 Now, please permit me to note concisely what seem to me 
 the points most essential in making this little book a success : 
 
 1. Positively do and have done everything indicated in the 
 text. Do not say some of these things are so simple or so 
 obvious that the doing would be a mere form. Probably some- 
 thing will turn up which you or your pupils could not anticipate. 
 
6 A WORD WITH THE TEACHER. 
 
 Do not be afraid to take hammers and collecting bags or baskets 
 into the garden or the field, and actually break the rocks and 
 study them and bring them home. No matter about keeping 
 quiet in this class. The very study requires talking and move- 
 ment. The novelty of the method and its conformity with the 
 impulses and instincts of the child's nature will assuredly make 
 it the favorite class of the school. 
 
 2. Should you happen to be located in a large city or upon 
 a prairie or other section of the country where boulders are not 
 easily accessible, the best recourse will be to a wagon load or 
 two of boulders brought from some boulder region and thrown 
 down in the school yard. These may be broken into moderate- 
 sized fragments by any man with a large-sized stone hammer. 
 All teachers, as a provision against rainy days, might have a 
 large lot of fragments placed under a shed. Even teachers in 
 states south of the boulder-covered regions of our country 
 might get a supply by the cheap help of a freight car from 
 the North. 
 
 3. A day or two before the class is taken on an " Excursion," 
 read it over yourself so as to know what to expect, and be 
 prepared for its requirements. When the excursion is taken, 
 you may let every pupil carry a book; or if you think better, 
 only carry one yourself, and read aloud from it, giving the 
 pupils time to examine and think and respond. 
 
 4. Make yourself sure that every pupil sees and does and 
 understands everything which is required, and does the best he 
 can in answering all questions. Be deliberate enough to render 
 this possible. Sometimes the lesson will need to be divided. 
 With some classes it will be best to devote an hour to the 
 excursion proper, and then the " Exercises " may occupy the 
 time on the next day. This may be the best method with all 
 classes. Sometimes the whole must be twice gone over. In 
 almost every lesson the positions of localities mentioned will 
 have to be studied from the School Atlas. 
 
 5. Accustom yourself and your pupils to copying the figures 
 
A WORD WITH THE TEACHER. 7 
 
 in the book; and practise still more in making drawings of 
 other things not figured, such as gravel banks, boulders, cliffs, 
 ravines, landscapes. Do not say, " I never took a lesson in 
 drawing," for the most finished draughtsmen were once in the 
 same situation. Try. Try again, and so continue. If you are 
 already somewhat practised in drawing, you will find your skill 
 extremely useful. The geological sections required, and the 
 other exercises on the geological map may be troublesome at 
 first, but no exercises can be more profitable. 
 
 6. Lay much stress on the "Exercises" and invent addi- 
 tional ones. Some of them are merely intended to set pupil 
 and teacher to thinking and investigating. Some of the ques- 
 tions cannot be definitely answered. When a question is pro- 
 posed which you cannot answer at once, say so frankly. We 
 all have to confess ignorance. I think the " Exercises " will 
 awaken much interest. You will, of course, have to ask many 
 questions on the text and its subject matter; but these you will 
 frame for yourself or find at the end of the book. 
 
 ?. Adhere strictly to the method indicated in the book; 
 but vary the details according to the circumstances, and extend 
 the instruction and the observations according to your own 
 judgment. 
 
 8. Have every pupil collect, preserve and label specimens. 
 A good plan to pursue is the following: To each specimen 
 attach a little circular bit of white paper to receive the " school 
 number." Let each different species or variety of minerals and 
 rocks receive a separate number. Those which are the same 
 species or variety will receive the same number. In a little 
 book write the numbers, and the names of the specimens cor- 
 responding to them. Let each pupil also attach to each of his 
 own specimens, a little colored paper each pupil choosing 
 some different bright color; or, if the same color as that of 
 another pupil, let it be cut oval or square or diamond shaped; 
 so that each pupil's specimens can be picked out when all are 
 placed in a pile together. Have each pupil also keep a cata- 
 
8 A WORD WITH THE TEACHER. 
 
 logue. Then the number on the white ticket stuck to each of 
 his specimens will give the name of the specimen as soon as 
 he refers to his list. You will find, a little beyond, some 
 practical directions for this work. 
 
 9. Use other specimens additional to those collected by the 
 class if it is possible to do so. By this means you will get 
 for study more species and varieties. There may be some 
 small, neglected collections or single specimens in your neigh- 
 borhood, lying on dusty mantels, what-nots and etageres. Look 
 them up and press them into service. I am sure you will find 
 many sorts which are not mentioned in this little book, because 
 the book mentions the most common things, which it is most 
 important to know something about; while people generally 
 seek to lay up rare things from distant regions. But use all 
 that you can. Besides this, there ought to be a small labelled 
 collection obtained from some reliable dealer, furnishing true 
 examples of the more common minerals and rocks. Such a 
 collection can be purchased for two or three dollars, or a 
 better one for five dollars. 
 
 All that may be learned by the aid of this little book will 
 only conduct the pupil over the threshold of the subject. But 
 even so much may be made highly interesting and indeed very 
 useful. Beyond this threshold are departments of the subject 
 not mentioned here, and a whole range of ideas and conclusions 
 about the history of the world, and of other worlds, which would 
 not be appropriate here, but which, nevertheless, are extremely 
 fascinating to the student, and tend greatly to enlarge and 
 ennoble his intelligence. 
 
 Now, I wish to feel in communication with all the teachers 
 who try to use this primer. Please exercise the freedom to 
 write on any point which you think may require further eluci- 
 dation from the author. 
 
 ALEXANDER WINCHELL. 
 
 UNIVERSITY OF MICHIGAN, 
 ANN ARBOR. 
 
SOME PRACTICAL SUGGESTIONS. 
 
 FOR STUDENTS OF ALL GRADES. 
 
 1. Hammers and some other instruments best suited for 
 breaking and studying rocks are described in Excursions VI 
 and VII. 
 
 2. For making the little circular or oval tickets, white or 
 colored, a saddler's or tinner's " punch " is suitable. One which 
 will cut tickets three-sixteenths of an inch in diameter is large 
 enough for small specimens. If many tickets stick together as 
 they come from the punch, place a lot in one hand and rub them 
 with the fingers of the other hand. Fold the paper so as to 
 punch through several thicknesses at each blow. Use a thin 
 quality of paper. 
 
 3. For attaching the tickets do not use common mucilage, 
 but prepare a cement as follows: 
 
 Clear Gum Arabic, 2 oz. 
 
 Fine Starch, H oz. 
 
 White Sugar, I oz. 
 
 Rub them together in a mortar; add as much water as the laun- 
 dress would use for that amount of starch, and wait till the gum 
 arabic is well dissolved; then cook the solution in a vessel sus- 
 pended in boiling water until the starch becomes clear. The 
 cement must be nearly as thick as tar. Keep it in a wide- 
 mouthed bottle stoppered by a cork having a small round bristle 
 brush passing through it. Drop in a small lump of gum camphor 
 to prevent souring and mouldiness. It will keep a year or more. 
 When too much dried away add a little water. This cement is 
 strong, and is good for repairing breakages of specimens, and 
 also for attaching specimens to cards for exhibition. 
 
10 SOME PRACTICAL SUGGESTIONS. 
 
 4. When many specimens are to be ticketed at once, spread 
 them on a table and touch each one in a proper place with the 
 tip of the brush, leaving a little cement, but not too much. 
 Spread a quantity of well separated tickets on the table; moisten 
 the tip of your finger on the tongue or a damp towel, and pick up 
 a ticket and press it firmly on one of the gummed spots; then, 
 as some of the cement probably adheres to your finger, remove 
 it on your tongue or the damp towel, and pick up another ticket 
 and attach it in the same way. This method is rapid. After 
 a half hour the tickets will be dry enough to receive the num- 
 bers. Use only the blackest and best ink in writing them, with 
 a fine-pointed steel pen, and make the figures perfect as possible. 
 
 5. Good cabinet rock specimens are generally dressed to a 
 rectangular shape if possible. For a school cabinet they may be 
 about two and a quarter by three inches square, and one or two 
 inches thick. But it is better to have a shapeless specimen than 
 none at all. Most of the pupils will probably be suited with 
 mere fragments. But in all cases, some approach may be made 
 to the standard form. Mere minerals must be preserved as 
 we can get them. When a specimen is reduced nearly to the 
 requisite size, the trimming may be best done while holding the 
 specimen in the left hand and striking a quick blow with a light 
 hammer, so as to chip off small pieces. Remember, the sharper 
 the blow, the less liable is the specimen to shatter. The last of 
 the dressing may be done by striking the specimen square on the 
 edge. This is especially practicable with quartzose and all crys- 
 talline rocks. Fossils should be worked out of the rock with 
 hammer and chisels and other appropriate tools, or at least the 
 adhering rock should be as much removed as possible. 
 
 6. When specimens are to be boxed for transportation, wrap 
 each separately in paper, and use enough packing material of 
 paper, hay or straw, to prevent rubbing against each other. 
 Always fill the box as full as possible. If the specimens will 
 not do it, use waste paper, sawdust or anything even fine 
 chips to fill all the empty spaces. 
 
STANDARD SAMPLES OF MINERALS AND ROCKS. 
 
 [To illustrate WinchelPs "Geological Excursions."] 
 
 The whole list forms "Collection No. 1." The list omitting the 
 starred names forms " Collection No. 2." 
 
 1. Quartz (at least one crystal with 
 
 termination). 
 
 2. Chalcedony or Agate. 
 
 3. Red Jasper. 
 
 4. Hornstone or Chert. 
 
 5. Orthoclase, showing crystalline 
 
 form. 
 
 6. Labradorite. 
 
 7. *Albite, or at least some third 
 
 feldspar. 
 
 8. Muscovite (common mica), show- 
 
 ing crystalline form. 
 
 9. Hornblende. Dark variety, show- 
 
 ing crystalline form. 
 
 10. *Actinolite. 
 
 11. Augite, common variety, show- 
 ing crystalline form. 
 
 12. Talc, foliated variety. 
 
 13. Calcite, rhombohedral and dog- 
 tooth varieties. 
 
 14. *Pyrites. 
 
 15. *Selenite. 
 
 16. *Hematite. 
 
 17. ^Magnetite. 
 
 18. *Limonite. 
 
 19. Quartzite, vitreous. 
 
 20. Quartzite, granular. 
 
 21. Quartzose Conglomerate. 
 
 22. Sandstone, gray. 
 
 23. *Sandstone, red. 
 
 24. Granulite (Quartz and Feldspar). 
 
 25. Granite (Quartz, Feldspar and 
 Mica), strictly unstratified. 
 
 26. Gneiss, distinctly stratified. 
 
 27. Mica Schist. 
 
 28. Hydromica Schist. 
 
 29. Hornblende Rock (Amphibolite). 
 
 30. Hornblende Schist. 
 
 31. Syenite (Quartz, Feldspar and 
 Hornblende) strictly unstratified. 
 
 32. Syenitic Gneiss, distinctly strati- 
 fied. 
 
 33. Hyposyenite (Orthoclase and 
 Hornblende). 
 
 34. Diorite (Plagioclase and Horn- 
 blende). 
 
 35. Diabase (Plagioclase and Augite). 
 
 36. *Dolerite. 
 
 37. *Modern Lava. 
 
 38. *Epidote Rock (or Epidotic 
 Rock). 
 
 39. *Talc Rock or Steatite. 
 
 40. Serpentine. 
 
 41. Argillite or Slate. 
 
 42. Shale, argillaceous. 
 
 43. *Kaolin. 
 
 44. *Petrosilex (Cryptocrystalline, 
 Quartz and Orthoclase). 
 
 45. Felsite (Cryptocrystalline, Quartz 
 and Plagioclase). 
 
 46. Porphyritic Rock. 
 
 47. *Marl. 
 
 48. Common Limestone, with Fos- 
 sils. 
 
 49. Marble (Crystalline Limestone). 
 
 50. Dolomite. 
 
 11 
 
12 . STANDARD SAMPLES OF MINERALS AND ROCKS. 
 
 1223 BELMONT AVENUE, 
 PHILADELPHIA, PA., January 8, 1884. 
 
 1 agree to supply suitable standard specimens, according to the foregoing 
 list, for schools using WinchelPs "Geological Excursions" the rock speci- 
 mens to be dressed to cabinet shape, and all to be permanently labelled, and 
 delivered in Philadelphia according to directions, for the following prices : 
 
 For "Collection No. 1," Students' size, $3.00; Teacher's size, $5.00. 
 For "Collection No. 2," Students' size, $2.00; Teacher's size, $3.50. 
 For Fragments, or undressed specimens, "Collection- No. 1," $1.50; 
 "No. 2," $1.00. 
 
 Extra for compartment tray (if ordered) with lid, as follows: 
 
 Pasteboard Tray, No. 1, Students' size, $1.00; Teacher's size, $1.50. 
 No. 2, Students' size, $0.75; Teacher's size, $1.15. 
 For Fragments, "No. 1," 75 cents; "No. 2," 50 cents. 
 
 With sides and top of black walnut, double the above prices.* 
 
 A. E. FOOTE. 
 
 *The "fragment" collections may be sent by mail the "Collection No. 1 " for 
 about 35 cents, and ".No. 2" for about 25 cents. 
 
GEOLOGICAL EXCURSIONS. 
 
 EXCURSION L In the Garden. 
 Organic and Inorganic. 
 
 T ET us step into the garden. Here is a gravel walk ; its 
 -*-* surface is covered with small rounded stones. If it is 
 not a gravel walk we can at least find a few small stones in 
 it. These stones do not grow, like asparagus and roses. 
 They do not take food of any kind ; they do not see or feel 
 as we tread upon them. Here are some plants. Probably 
 they do not see or feel ; but they grow, and they take in 
 nourishment through their roots and leaves to enable them 
 to grow. Here is a toad, sheltering himself under the 
 leaves of the plant. He is waiting till sunset, when he 
 will hop out and search for insects to eat. The toad also 
 feeds and grows ; and in addition he sees and feels. 
 
 We say the plant and the toad and the insect are organic ; 
 because they have organs or parts which enable them to do 
 all the various things which their lives require. State what 
 some of those things are. The power to do one of these 
 things we call a function. The heart is an organ whose 
 function is to propel the blood through the blood vessels. 
 What is the function of the teeth ? Every organ has some 
 function. But the stone has no organs, and it performs no 
 
 13 
 
1* GEOLOGICAL EXCURSIONS. 
 
 functions. It simply lies still, and permits the atmosphere, 
 the rains and the frosts and the sun to do all they can to 
 dissolve it, or crumble it to powder, and cause it to waste 
 away. It is inorganic. It has neither mouth nor legs, nor 
 liver, nor any other organs. If we should examine it with 
 a microscope, we should not be able to find any cells, or 
 fibres, or membranes, or vessels, as we would in a plant or 
 an animal. The stone is very similar all through, from 
 side to side. So we see a great difference between an inor- 
 ganic body and an organic body. The substances of which 
 an inorganic body is composed are called mineral sub- 
 stances. The chemist tells us that an organic body is also 
 composed of mineral substances ; but the difference is that 
 in the organic body the substances are made first into com- 
 pounds which do not exist in the inorganic body, and these 
 are then made into organs, which are also wanting in the 
 inorganic body. 
 
 All organic bodies have life, or have had life. An or- 
 ganic body when dead is still organic until it is decomposed. 
 Its parts are then inorganic. Organic beings may produce 
 substances which have no organic structure such as sap, 
 spider's web, perspiration and dandruff. These are organic 
 products, and are therefore organic. 
 
 EXERCISES. 
 
 Name several organic bodies. Name several sorts of inor- 
 ganic bodies. In what respect is a silver coin like a stone ? 
 Is a stone organic or inorganic ? Is the head on the coin 
 organic or inorganic ? How is it with a board ? a pen ? the 
 outer dead bark of a tree? a linen handkerchief? a silk dress? 
 
IN THE GARDEN AND FIELD. 15 
 
 a dinner plate ? a potato ? a dish of mashed potatoes ? the 
 breath from your nostrils ? a dead leaf ? an extracted tooth ? 
 milk ? beer ? molasses ? clay ? paper ? a squash ? the same 
 squash mashed for dinner? the ashes from a coal fire? the 
 ashes from a wood fire ? lemonade ? a pocket knife ? an oyster 
 shell ? a peach stone ? the sting of a bee ? a loaf of bread ? a 
 loaf of bread burned to ashes ? a dead bird ? chewing gum ? 
 hair of a mouse ? gelatine ? stove-mica ? lamp smoke ? air ? 
 Which are more abundant, organic things or inorganic things? 
 Which are more useful ? Which decay more easily ? Are you 
 organic or inorganic ? Is there any mineral matter in your 
 composition ? In what respects do you resemble a stone ? In 
 what do you differ from a stone ? 
 
 EXCUKSION II. In the Garden and Field. 
 Boulders and Sand. 
 
 Let us go into the garden again. Look very carefully at 
 the gravel on the walk. Here, where there is no gravel 
 walk, we still see some little stones just like those which 
 form gravel. The stones are of various sizes. Some are so 
 small that we might call them grains of sand ; and some are 
 large enough to be called pebbles. Still others are so large 
 as to be called cobble stones, and are sometimes used to 
 pave streets, or at least, to pave the gutters along the sides 
 of tho streets. The little stones which the boys throw are 
 rounded pebbles; the larger ones which they use to crack 
 nuts are cobble stones. 
 
 But then, what is the difference between a cobble stone 
 and one of those larger rounded stones in the field or by the 
 roadside which a boy could scarcely lift? or even those 
 
16 GEOLOGICAL EXCURSIONS. 
 
 still larger ones which a man could not lift ? Is there any 
 difference except in size? Let us examine some of them. 
 We must go into the field. There is no difference. If we 
 inspect grains of sand, we see that most of them are light- 
 colored when washed clean. But many are stained, and 
 some are brown, and some are even black. Different grains 
 thus differ among themselves. 
 
 Now collect a lot of pebbles. You see that they differ in 
 the same way as the grains of sand. Only you see some 
 pebbles which seem to be made up of different sorts of 
 mineral matters. Some look as if a great many grains of 
 sand had been stuck together to form a cobble stone. Each 
 different kind is a separate mineral. Most of the large, 
 loose rocks in the field present the same appearance. Some- 
 times a larger stone seems to be made of several pebbles. 
 
 Well, if we turn now from the larger to the smaller again, 
 you will find some of these grains of sand, on close examin- 
 ation, to be composed of different mineral materials. Let 
 us select a number of such grains. You may know them by 
 the difference of color in different parts of the grain. How 
 many colors in this grain ? How many in the next one ? 
 What colors are they? 
 
 Of course, the stones larger than pebbles and cobble 
 stones generally contain various mineral substances also. 
 Let us examine some of these stones. Here is one in which 
 we can detect much white rock, together with some pink and 
 some smoky. Here is one with white and cream color and 
 black. Here is one with two kinds of white and also black. 
 Here is one full of red rounded spots or pebbles, with some 
 
IN THE GARDEN AND FIELD. 17 
 
 smaller dark-colored ones, and many white or glassy ones. 
 Here is a large rounded rock with white grains of two kinds 
 and black grains of two kinds. 
 
 Now, perhaps, where you are you will not find exactly 
 such kinds and such mixtures of minerals as these, but you 
 will find some kinds. You can also tell what colors they 
 are and how they are mixed. Do not fail to tell all that you 
 can. How many colors or kinds of minerals can you find 
 all together ? Are the separate minerals always rounded ? 
 Are the separate minerals ever angular like grains of coarse 
 salt? See if you can find rocks with the same mineral colors 
 as I have just mentioned. 
 
 Well, all these rounded stones are called boulders. Some 
 stones are not boulders. All stones taken from quarries are 
 not boulders. All stones which have been broken from a 
 ledge of rock not far away are not boulders. You may 
 know a boulder by its rounded and smoothed appearance, 
 and by the fact that it is a different kind of rock from any 
 ledges or quarry stones in the neighborhood. Would you 
 call a boy's pocket marbles boulders? 
 
 In some regions there are no stones to be found except 
 boulders. This is the case in some parts of the western 
 states. In the Lower Peninsula of Michigan there are very 
 few ledges of rocks ; and the people sometimes break up 
 boulders for building stones. Sometimes boulders are large 
 enough to weigh fifteen, twenty or even hundreds of tons. 
 In New Hampshire and Vermont are many enormous boul- 
 ders. Here is a picture of one in New Hampshire, which is 
 46 feet long, 24 feet wide, and 26 feet high. You see a 
 
18 
 
 GEOLOGICAL EXCURSION'S. 
 
 FIG. 1. GREAT BOULDER NEAR GILSUM, N. H. 
 (C. H. HITCHCOCK.) 
 
 school house in the 
 shelter of the rock. A 
 piece 33 feet long and 
 10 feet wide was split 
 off by frost in 1817. 
 The whole stone be- 
 fore splitting contain- 
 ed 32,000 cubic feet, 
 and weighed 2,286 
 tons. Far away, a 
 
 thousand miles from 
 this, large boulders are equally abundant. Here in Figure 2, 
 
 FIG. 2. GREAT BOULDER OF PORPHYRY AT ST. IGNAOE, LAKE SUPERIOR, 
 
 (PHOTOGRAPH.) 
 
IN THE GARDEN AND FIELD. 19 
 
 is a view of one at St. Ignace, Lake Superior. It is composed 
 of porphyry, and is 25 feet high. Notice how it is rounded. 
 You can see also, that the region abounds in smaller boulders. 
 In most parts of New England large and small boulders are 
 everywhere to be found. Here in Figure 3 is a view near 
 
 FlG. 3. A BOULDER-COVERED FlELD NEAR GLOUCESTER, MASS. (SlEELE.) 
 
 Gloucester, Massachusetts. In Connecticut, in the neigh- 
 borhood of Long Island Sound, some regions are so thickly 
 overspread that one can cross a field without touching the 
 ground. On the contrary, there are some regions where no 
 boulders are to be found. There are very few on the prairies 
 of Illinois. There are none south of Virginia, Kentucky 
 and Missouri. In some of the southern states also, there 
 are almost no ledges of rocks ; and the people have no 
 building stones except such as are brought from a great dis- 
 tance. But almost everywhere some pebbles may be found. 
 Now, one thing more. Examine this soil. What does 
 it seem to be composed of? It is partly fine and partly 
 
20 GEOLOGICAL EXCURSIONS. 
 
 coarse. Let us try an experiment. Take a tall glass vessel, 
 or even a clear glass bottle or fruit jar, and stir 
 a handful of soil in the vessel full of water. 
 There, how muddy the water becomes! but 
 most of the matter sinks quickly to the bottom. 
 Some, however, settles slowly. Watch it. 
 Now we have a handful of soil assorted. The 
 coarser parts are at the bottom ; the coarse 
 sand is above these ; the fine sand next, and 
 the particles of mud are floating in the water. 
 FIG. 4. We will pour off the muddy water and fill the 
 ASSORTMENT vessel again with clear water. The water is 
 IN THE SOIL. st ^ stained ; but most of the matter in the 
 vessel can now be seen to consist of sand, with 
 a few small pebbles. Is it possible ? The soil itself is 
 almost wholly composed of mineral substances, which do 
 not differ from pebbles except in being finer. These finest 
 substances and the coarser all belong to one class. What- 
 ever made the larger boulders and the pebbles, made also 
 the principal part of the whole soil. 
 
 EXERCISES. 
 
 What was the mud composed of which we poured off with the 
 water? Did it consist chiefly of still finer mineral substances? 
 Are there any organic substances in the soil? What is the 
 reason for your answer? What could be the origin of any 
 organic substances in the soil ? Do the roots of plants use any- 
 thing in the soil? What is the use of the soil to a tree except 
 to support it just like a fence post? If plants use anything in 
 the soil, do they use it in a solid state or in a state of solution ? 
 What substances may serve as food for plants? Do any of these 
 
TO THE GKAVEL BANK. 21 
 
 come from the mineral matters in the soil? Would plants grow 
 in a soil composed of clean sand? Why do you answer thus? 
 Do you suppose the grains of sand were ever parts of larger 
 mineral masses ? Could you make sand out of a pebble ? Could 
 you make mud from a pebble? Are these pebbles undergoing 
 any changes? Are there any causes which reduce them slowly 
 to the condition of sand and mud? Take this pebble home and 
 bring it back as mud. What is a brick made of ? Is clay in any 
 respect like mud? How was the brick made so hard? Is the 
 brick a rock? Do you think any of the rocks may have been 
 made of mud originally? Can you think of one way in which 
 the mud and gravel could have been hardened into rocks? Are 
 there any boulders about the place where you live ? How many 
 kinds of boulders can you bring from your garden? Try it; and 
 if a boulder is too large, bring a piece of it. 
 
 EXCURSION III. To the Gravel Bank. 
 The Drift. 
 
 Let us make an excursion to some gravel bank. We 
 may find it alongside of the river or brook, where the 
 stream flows close to the high land. Or we may find it 
 on the railroad in the " deep cut." Or just in the border of 
 the town, where the authorities obtain gravel to spread on 
 the streets, or the masons dig for sand for making mortar. 
 Somewhere is a gravel bank. Here it is. (See Fig. 5.) 
 
 This is a common gravel bank. Here is the soil at top, 
 such as we found in the garden ; but in this place we see 
 what lies beneath the soil. First, we have the subsoil, 
 which is very commonly of a yellowish or reddish color, and 
 is apt to have many gravel stones and pebbles scattered 
 
22 GEOLOGICAL EXCURSIONS. 
 
 through it. The subsoil is indicated by a a a a. In one 
 place we see a deep funnel-shaped prolongation downward, 
 which is perhaps a place once filled by the tap root of some 
 tree which grew there. The subsoil shows very little strati- 
 fication. That is, it is not arranged in layers. Beneath the 
 subsoil we find beds of gravel stones and fine sands ar- 
 ranged in irregular layers, which constitute a confused strati- 
 fication. First, we see some gray gravel beds, b t> , which 
 incline in diiferent directions. Then we come to a thick bed 
 of pale buff fine sand, c c c c, which is pretty evenly strati- 
 fied, with the thin layers or laminae nearly horizontal. Be- 
 neath this is a course of pebbles, d d d, and at e e e is 
 another course. Between them is a stratum of pebbly sand 
 which is obliquely laminated. Below e e is a bed of gravel, 
 f f ft quit 6 distinctly laminated, but with the laminae in- 
 clining toward the left instead of the right. At g g is a bed 
 of coarse sand, with laminse inclining toward the right. It 
 reaches up and partially blends with the gravel stratum be- 
 tween d and e. At A A is another stratum of fine buifish 
 sand, with lamination inclined steeply to the right. All 
 these bands and strata are distinguished by differences in 
 coarseness and by differences in color. At the foot of the 
 bank is a sloping pile of sand, i i i, which has run down 
 from above. In one place, j, is a collection of lumps of 
 red subsoil fallen down from the top. A sloping bank of 
 rubbish at the foot of a bluff of gravel or rocks is called 
 a talus. Often we find cobble stones along the foot of the 
 bluff which have rolled out of the bank above. These are 
 sometimes iron-stained ; sometimes covered by a white crust, 
 
TO THE GRAVEL BANK. 
 
24 GEOLOGICAL EXCURSIONS. 
 
 which holds gravel stones cemented to the larger stones. 
 This crust is a precipitate of calcium carbonate. This will 
 be explained hereafter. 
 
 This fine example of a gravel bluff simply illustrates 
 what may be found on almost every square mile of the 
 northern states. This view is 129 feet above the bed of the 
 Huron River, and 204 feet above the bed rock, which has 
 only been found by boring. On the bed rock the drift is 
 found to be a heavy mass of unstratified clay, with many 
 large boulders dispersed through it. At other localities 
 this bottom boulder clay is found exposed at the surface. 
 
 We may find these loose materials lying upon the sur- 
 face in all parts of the northern states. The depth varies 
 from nothing to one, two or three hundred feet. It is won- 
 derful that by any means such an enormous amount of loose 
 materials could have been spread over the country. The 
 sands and clays are generally somewhat assorted, and ar- 
 ranged irregularly in separate layers. Can you not recall 
 some railroad cut where this assortment is shown ? Such 
 arrangement is known as stratification, and the separate 
 layers are strata. When we wish to speak of one layer it 
 is a stratum. Sometimes the finer materials have been 
 completely removed, and we find only a bed of pebbles and 
 large boulders, as at many places in Massachusetts. Visit- 
 ors to Martha's Yineyard may find such a coarse deposit 
 at many points along the beach. All these loose materials 
 scattered over the northern states are Drift. The whole 
 extent of the deposit forms the Drift formation. 
 
 Along the shores of the ocean and the Great Lakes the 
 
TO THE GRAVEL BANK. 25 
 
 sands are washed out by the action of the waves in certain 
 places, and transported and deposited again in more pro- 
 tected places. Sometimes two habitual movements conflict- 
 ing with each other cause the drifting sands to be deposited 
 in enormous banks and sandy sloping beaches. When dried, 
 the winds sometimes lift the fine sands which have been left 
 high along the beach, and drive them inland. Thus are 
 formed piles of dry sand called dunes or downs. The wind 
 continues to drive the sand forward, and so, fertile fields, 
 gardens, houses and forests are sometimes buried beneath 
 it. At the south end of Lake Michigan especially about 
 Michigan City maybe seen some enormous sand dunes. 
 At Grand Haven the sand buried the railroad track, fences 
 and buildings, and the station had to be removed to the 
 opposite side of Grand River. 
 
 EXERCISES. 
 
 What is the nature of the surface of Cape Cod? Can you 
 imagine how Cape Cod may have been formed? Is Cape Cod 
 extending or diminishing? Can you think of any other sandy 
 cape forming in a similar way? What is Sandy Hook? Are 
 there any sand dunes on the coast of New England? What is 
 the connection between dunes and the prevailing direction of the 
 wind ? Why are there so many dunes on the east shore of Lake 
 Michigan and none on the west ? What is the prevailing direc- 
 tion of the wind in the northern states? Should there be any 
 sand dunes on the coast of California ? What is the fact in the 
 case? Should there be any on the east side of Chesapeake 
 Bay ? What is the source of the materials which so suddenly 
 form bars and new islands in the Mississippi River? Do you 
 know of any bed rocks which are not covered with Drift ? 
 Where are they ? Why does the Drift not cover them ? Are all 
 
26 GEOLOGICAL EXCURSIONS. 
 
 bed rocks ledges ? Are all ledges bed rocks ? Why is there so 
 little vegetation on sandy surfaces? What is the desert of 
 Sahara? Is there any way to prevent the drifting of the sands 
 from dunes ? Now make a sketch of the sand bank or gravel 
 bluff, and bring it to the next meeting of the class. 
 
 EXCURSION IV. To Another Gravel Bank. 
 Springs and Wells. 
 
 Let us go to another bank. It may be very near the 
 first. Here is a little difference. A spring of pure water 
 issues from the bank and trickles down the slope. Just 
 underneath the spring is a bed of clay, and all the bank 
 above is composed of loose materials. The clay bed or 
 stratum can be traced in both directions some rods, and 
 it is seen to show a concave depression at the spring. The 
 water issues from a small opening which has been worn 
 by the flow. Now it is plain that when the rain falls on 
 
 FIG. 6. GRAVEL BANK AND SPRING. 
 
TO ANOTHER GRAVEL BANK. 27 
 
 the surface of the ground, it soaks downward through the 
 gravel as far as this dish of clay. Then it follows along 
 the surface of the clay toward a lower level. In this case 
 its course leads directly to the face of the bank, and when 
 it reaches that, the water issues as a spring. Suppose we 
 go to the top of the bank and dig a well at a point not 
 too far back ; when we reach the clay stratum we shall 
 find the water resting on it, and the water will flow into 
 the well. If the clay stratum were not there we should 
 have no spring and no well. But there is probably an- 
 other clay stratum at some greater depth, and undoubtedly 
 water would be found resting on that. So a well might 
 be obtained by digging deeper. There are many gravel 
 banks where several clay beds may be seen, or found by 
 digging. But they seldom continue uninterrupted for great 
 distances. Nor are they parallel with each other. They 
 overlap each other in every fashion and are inclined in 
 various ways. 
 
 Suppose some stones or substances exist in the gravel 
 bank which are capable of being dissolved in water like 
 salt or limestone or gypsum or iron oxide. Then the water 
 which issues at the spring will be a solution of such sub- 
 stances. The water will be a mineral water more or less 
 strong. 
 
 Many times the water dissolves some substance in one 
 place and then deposits it in another. Some mineral is 
 very frequently deposited by the water where it escapes at 
 the spring. This is because water generally cannot hold 
 so much mineral in solution when exposed to the air as 
 
GEOLOGICAL EXCURSIONS. 
 
 it can while confined deep in a gravel bed. In New York 
 and the Western States spring waters often deposit large 
 amounts of matter consisting chiefly of limestone that had 
 been dissolved in the earth. The matter is not all thrown 
 down or precipitated until the water has flowed several 
 rods. If the water flows over a hard sloping surface, it 
 deposits a hard crust which continues to grow until some- 
 thing similar to a bed of limestone is formed. "We call it 
 travertin. In some countries it forms extensive beds 
 which are quarried for building 
 purposes. If the water flows over 
 flat ground and stands, the deposit 
 is spongy and irregular, and we call 
 it calcareous tufa. Often it is 
 mixed with earth and stones. 
 Sometimes the stems of mosses and 
 dry leaves and sticks and bones of 
 animals become incrusted with it. 
 Some very beautiful specimens of 
 so called "petrified moss" are pro- 
 duced. If the water is collected in 
 a pond or lake the deposit falls to the bottom and forms 
 a white powdery layer which we call marl. Here it 
 becomes mingled with dead shells of molluscs which 
 lived in the pond or lake, and thus forms shell marl. 
 These shells are real fossils. Sometimes shell marl be- 
 comes quite dry and hard. It is then extremely like a 
 common limestone with fossil shells in it. Water which 
 contains limestone in solution is called hard. In many 
 
 FIG. 7. "PETRIFIED 
 Moss." 
 
TO ANOTHER GRAVEL BANK. 29 
 
 parts of New England there are no limestones in the 
 gravel deposits; and hence no " hard "water is produced. 
 The water of wells and springs is there soft. 
 
 Besides limestone there is often iron oxide in the earth 
 to be dissolved by the waters which circulate underground. 
 Such waters are called chalybeate. The iron is sometimes 
 deposited in marshy situations, and forms bog iron ore. 
 Frequently both lime and iron are deposited, and the mix- 
 ture forms a sort of paint called ochre. The greater the 
 amount of iron the deeper the color. Also, when the iron 
 oxide is chemically combined with water, the ochre is 
 yellow, more or less pale; but if it is burned so as to 
 drive oif the water, the ochre is of a red color. Before 
 the paint can be regarded of first quality it has to be 
 ground very fine. Iron deposits from springs are common 
 in most parts of the country. The pebbles and sand from 
 a bank of drift are often deeply incrusted and even ce- 
 mented together by a deposit of iron. This is very strik- 
 ingly shown along the bluff shores of Martha's Vineyard. 
 
 EXERCISES. 
 
 Can you mention any chalybeate spring? Do you know any 
 spring whose waters stain the stones of a reddish color? Can 
 you point out any bed of bog iron ore ? Are chalybeate springs 
 much resorted to for purposes of health? Have you ever seen 
 a bed of marl ? Of what is marl chiefly composed ? Where did 
 the material come from ? Do the rains increase or diminish the 
 amount of soluble matter in the soil ? Is lime in any form use- 
 ful to vegetation ? Is it ever used by farmers ? Is it more used 
 in the eastern or the western states ? What use may the farmer 
 make of the marl which accumulates in the ponds and low 
 
30 GEOLOGICAL EXCURSIONS. 
 
 grounds ? A man dug a well and found water at the depth of 
 twenty feet; his near neighbor had to dig sixty feet; why was 
 that ? On a gravel hill two hundred feet high the well is only 
 fifteen feet, while at the foot of the hill water is found only by 
 digging fifty feet; why is that? Can you make a diagram 
 showing how the materials are arranged to produce such results ? 
 If I dig a well in sand near the sea shore and water enters below 
 the sea-level, why is that water fresh? Why are some wells 
 lower in a wet spell than in a dry one ? Why do the rivers not 
 cease to flow during a summer drouth ? Why does the earth 
 retain some moisture even in the dryest weather? Which is 
 best to retain moisture in a dry spell, a very clayey soil, or one 
 with a good proportion of fine sand ? What is the cause of the 
 crust which forms on the bottom of the tea-kettle? 
 
 EXCURSION V. To Our Laboratory. 
 How Things are Put Together. 
 
 You know already that many different kinds of rocks 
 exist. They are of different colors and different degrees 
 of hardness, and they are also different mixtures of min- 
 erals. We are very anxious to know more about rocks, so 
 as to be able to call each one by its name. Most rocks 
 are mixtures of different minerals, and we must therefore 
 learn a little about minerals. But minerals are mostly 
 composed of two or more substances or chemical elements ; 
 and therefore we must learn something about chemical ele- 
 ments and the way they combine with each other. 
 
 Now let us perform a couple of little experiments. 
 First, take a piece of chalk and drop a little strong acid 
 upon it. Vinegar will answer if strong. Do you see the 
 
TO THE LABORATORY. 31 
 
 little bubbles rise as if the chalk were boiling? A drop 
 of water or oil will not produce such a result. This ia 
 chemical action ; we shall try to understand it. 
 
 Again, let us take a vial of lime-water. We can pro- 
 cure it of the druggist, or can prepare it ourselves by 
 shaking up some quick-lime in water and pouring off the 
 clear water into a glass bottle after the mixture settles. 
 Now take a glass tube, which can also be had of the drug- 
 gist ; or otherwise take a simple oat straw and breathe 
 through this into the clear lime-water. Do you see the 
 white cloud which forms? Continue to do so for two or 
 three minutes, and then let the lime-water stand for some 
 time. There, do you see the fine powder settling on the 
 bottom? It will all fall down and leave the liquid clear 
 above. This is also a chemical operation. Now let us see 
 how it can be explained. 
 
 You remember the stone which you took and pounded 
 to a fine powder, and, by mixing a little water, made into 
 mud. Well, however fine you made the powder, each 
 particle might, by some means, be made even smaller. 
 We can at least think smaller particles. But it is com- 
 monly believed that there are really particles so small that 
 it would not be possible by any means to make them 
 smaller. These are called atoms. They are really vastly 
 finer than the finest particles of the finest dust which floats 
 in the air. If we could take a drop of water and magnify 
 it to the size of this earth, and magnify the atoms in it in 
 the same proportion, the atoms would be about the size 
 of small shot. All substances are made up of these minute 
 
32 
 
 GEOLOGICAL EXCURSIONS. 
 
 atoms. Iron is made of atoms. Water is made of atoms. 
 The air is made of atoms. 
 
 There are about sixty-four different kinds of atoms 
 known. Iron contains one kind, sulphur another kind, 
 silver another. The atoms of each kind have a strong 
 attraction for certain other kinds of atoms. This is chem- 
 ical affinity. The two kinds corne together when they can, 
 and remain close together. This is a chemical combina- 
 tion. So most substances are compounds of different kinds 
 of atoms. Water is made of two kinds of atoms ; that is, 
 water is a compound. But iron is composed of only one 
 kind of atom ; that is, iron is an element. All the metals 
 are elements. Now there are only sixty-four elements 
 known in all the great mass of the earth. Not more 
 than thirteen of these are very important in making all 
 the rocks. I will give their names because they ought to 
 be learned. If we should take 100 pounds of the average 
 solid earth, there would be in the mass 
 
 Oxygen, 
 Silicon, . 
 Aluminum, 
 Iron, . 
 
 Calcium, 
 Sodium, . 
 
 45 pounds. 
 
 Potassium, 
 
 25 
 
 Carbon, 
 
 10 
 
 Hydrogen, 
 
 8 
 
 Sulphur, 
 
 6 
 
 Nitrogen, 
 
 2i * 
 
 Chlorine, 
 
 
 Magnesium, j 
 
 2 pounds. 
 
 All together nearly 
 11 pounds. 
 
 In the atmosphere and in water there are larger pro- 
 portions of Nitrogen, Oxygen and Hydrogen. 
 
 Oxygen has a strong affinity for most of the other 
 elements, and the compounds which it forms with them 
 are called oxides. So chlorine unites with other elements 
 
TO THE LABOKATORY. 33 
 
 and forms chlorides. We are very familiar with many of 
 the oxides. Water is hydrogen oxide. Lime is calcium 
 oxide. Caustic soda is sodium oxide. Caustic potash is 
 potassium oxide. Iron rust is iron oxide. So common 
 salt is sodium chloride. Now state what these different 
 oxides and chlorides are composed of. Some compounds 
 contain two or three times as much oxygen or chlorine 
 or other elements as other compounds contain; but we 
 cannot go so far as to take any account of that at the 
 present time. 
 
 The union of oxygen with certain elements results in 
 acid-forming oxides. With other elements bases are 
 formed. The addition of hydrogen to the acid-forming 
 oxides makes acids of them. The names of the acids 
 most important for us end ill ic. Thus, sulphuric acid, or 
 "oil of vitriol," is composed of sulphur, oxygen and 
 hydrogen. Nitric acid is composed of nitrogen, oxygen 
 and hydrogen. The basic oxides have names which end 
 in a. Many of them have also old popular names. Thus 
 the oxide of potassium or potassium oxide is potassa or 
 potash ; the oxide of sodium is soda ; the oxide of cal- 
 cium is lime ; one oxide of iron is iron rust. 
 
 Now please have patience with a little further explana- 
 tion. The acids generally have strong affinities for the 
 bases, and the compounds which they form are called 
 salts. When the name of the acid ends in ic^ the name 
 of the salt ends in ate. If sulphuric acid unites with pot- 
 ash the salt is sulphate of potash, or as it is now called, 
 potassium sulphate. So sulphate of soda, or sodium sul- 
 
34 GEOLOGICAL EXCURSIONS. 
 
 phate, is formed from sulphuric acid and soda ; silicate of 
 lime, from silicic acid and lime ; carbonate of lime (com- 
 mon chalk, marble, limestone or marl) is composed of 
 carbonic acid and lime. 
 
 Some acids have stronger affinities than other acids 
 have for certain bases. Sulphuric acid attracts lime more 
 powerfully than carbonic acid does. So if we should mix 
 sulphuric acid, carbonic acid and lime together, the lime 
 would be taken by the sulphuric acid. Even strong vine- 
 gar, which is acetic acid, would do the same thing. More 
 than this, suppose carbonic acid to be already combined 
 with lime, forming chalk ; then suppose a little strong 
 vinegar or sulphuric acid to be brought into contact with 
 the chalk, it seizes the lime and drives the carbonic acid 
 off with much ado. Carbonic acid is a gas, and that is 
 the reason why its escape produces effervescence. But if 
 we introduce carbonic acid into water containing lime in 
 solution, this acid unites with the lime, forming carbonate 
 of lime in the water. As carbonate of lime is not much 
 dissolved by water, the particles remain suspended in the 
 water for a time. They finally settle down, however, as a 
 white powder. This is of the same nature as chalk and 
 marl. It is even called precipitated chalk. This is the 
 explanation of the little experiments just made. 
 
 EXERCISES. 
 
 Cut about seventy-five small square pieces of white card- 
 board. On ten of these write a heavy capital O, which stands 
 for oxygen. On six of them write H, which stands for hydro- 
 gen. Put also the symbol of each of the other principal ele- 
 
TO THE LABORATORY. 35 
 
 ments on four others, thus: Si for silicon, Al for aluminum, Fe 
 for iron, Ca for calcium, Na for sodium, K for potassium, C for 
 carbon, S for sulphur, N for nitrogen, Cl for chlorine and Mg 
 for magnesium. Then put S and O together, representing an 
 acid-forming oxide, and to show that it is such add a card 
 having on it a cross made with red ink. Add H, and you have 
 an acid. What is the name of it ? Then put Ca and O to- 
 gether representing a basic oxide ; and to show this put with 
 them a card having on it a cross made with blue ink. What 
 is the name of this base ? Then put the acid and the base 
 together, and tell what is the name of the salt. Examine the 
 cards now and see what different elements enter into this salt. 
 With these little cards illustrate the other combinations men- 
 tioned. Also those to be mentioned in these exercises. 
 
 Now, what caused the effervescence when we dropped a 
 little acid on the chalk ? What is the name of the acid which 
 escaped. Represent it with the cards. What became of the 
 lime? Represent it with the cards. What is the name of the 
 salt formed? What became of the carbonic acid? When you 
 breathed in the lime-water what caused the white cloudiness ? 
 What was the substance which fell to the bottom? Represent 
 its composition by means of the cards. If oxygen unites with 
 iron what is the name of the compound? Show me some oxide 
 of iron. When chlorine unites with sodium what is the name 
 of the compound? What is its common name? If oxygen 
 unites with aluminum what results? Suppose silicic acid com- 
 bines with alumina, what is the compound ? When lime-water 
 stands exposed to the air what causes the crust which forms 
 on the top ? Why does the druggist keep his lime-water close- 
 stoppered? What complaint of the stomach is lime-water good 
 for? Suppose you put a little strong acid in a bottle half filled 
 with water, and then drop in some chalk and stop the bottle 
 tightly, what would result ? What, if you should drop in some 
 bits of marble? Suppose pulverized chalk and flour are well 
 mixed, and then the whole is kneaded with vinegar and water, 
 what would result? Suppose carbonate of soda, tartaric acid 
 
36 
 
 GEOLOGICAL EXCURSIONS. 
 
 and flour are mixed and kneaded with water, what results? 
 Can we see the atoms of matter with a microscope ? What 
 are the components of sulphate of potassa? 
 
 FIG. 8. GEOLOGICAL HAM- 
 MER, PALEONTOLOGIST'S 
 PATTERN. 
 
 EXCURSION VI. To the Field. 
 
 Quartz. 
 
 Now we will walk into the field again, and will take some 
 simple implements with us. "We shall want first of all one 
 or two hammers. If each person 
 can have a hammer that will be bet- 
 ter. A good form of geological 
 hammer is here shown in Figure 8. 
 The pene a is at right angles to the 
 face 1} and the handle. The face is 
 flat, and a little longer than broad. 
 The hammer should be of fine steel, with the temper of a 
 stone mason's hammer. The eye should be large, and the 
 handle of hickory. For student's use a hammer weighing 
 from half a pound to a pound will be 
 most generally useful. But a hammer 
 weighing two pounds or more will 
 
 frequently be needed also. The form 
 FIG. 9. GEOLOGICAL HAM- 
 MER, QUARRYMAN'S PAT- of the regular stone mason's hammer 
 
 (Fig. 9) is quite as suitable for work- 
 ing among very hard rocks. It is better to use any hammer 
 which can be had than not to break the rocks at all. We 
 shall want, also, a pointed piece of hard tempered steel to 
 test the hardness of minerals. A good strong knife blade 
 
TO THE FIELD. 37 
 
 will answer well; but if you feel unwilling to subject a knife 
 blade to such use, you can employ a simple implement like 
 Figure 10. This is simply a piece of steel rod flattened and 
 pointed at one extremity, and rather high tempered. But 
 
 FIG. 10. HARDNESS TESTER. 
 a. View of flattened side of point, b. View of taper toward the point. 
 
 whatever implement you become accustomed to should be 
 used every time. It will be well to have also a small vial 
 of acid either very strong vinegar or diluted hydrochloric 
 acid. 
 
 Well, here we are amongst the rocks. Let us first give 
 attention to the boulders, for we can find more varieties of 
 rocks among them. We first pick out a rock showing a 
 mixture of light and dark colors. These are probably differ- 
 ently colored minerals. Now fix your attention upon one of 
 these minerals and see if you can scratch it with your steel. 
 Do you say yes? Well, look at it closely, so that when you 
 see another piece of the same kind you will know it. See 
 if you can find another just like it. Well, does your steel 
 scratch it just about as easily ? Try another light colored 
 mineral, does your steel scratch it ? If not, this is a harder 
 mineral ; it is a different mineral. Your steel leaves a dark 
 line on it. The mineral which you cannot scratch is quartz. 
 But see, there are several differently colored minerals which 
 
38 GEOLOGICAL EXCURSIONS. 
 
 the steel does not scratch. Do yon find them? They may 
 not be all in one stone. Well, they are all quartz. They 
 are different varieties of quartz. You will find one variety 
 to be white and opaque like porcelain ; another will be trans- 
 parent; another slightly rosy; another smoky; another 
 almost black ; another brick red. That is, you will be able 
 to find all these sorts if you examine different rocks. But 
 they all have a glassy appearance. Quartz is the hardest 
 mineral you will have to deal with. It is hard enough to 
 scratch glass. Besides its hardness, you may know it by its 
 glassy lustre. The freshly broken surfaces glisten like broken 
 glass. Further, it always breaks with an irregular fracture; 
 and this is also like glass. Sometimes you find a boulder 
 composed entirely of quartz. They are generally white or 
 very light colored. They are often called "flint rocks." 
 But flint proper has generally a little duller lustre, and is 
 apt to be dusky or dark colored. The red quartz is mostly 
 red jasper. Many gems are' little else than quartz. This is 
 the case with agate, amethyst, carnelian, chalcedony, onyx 
 and some others. The colors are caused by the admixture 
 of impurities. 
 
 Well, what is quartz \ It is only silicic acid ; or we com- 
 monly say when this oxide is not combined with the base, it 
 is silica. It is, therefore, composed of only two elements, 
 when pure. It forms also, beautiful crystals beautiful in 
 form and beautiful in glassy transparency. Here are some 
 quartz crystals (Figure 11). You see each one has six 
 sides. It is a hexagonal prism. The sides may all be 
 equal; but generally they are not so, because more 
 
TO THE FIELD. 
 
 39 
 
 crystalline matter has been deposited on one side than on 
 others. See also, how the end 
 of the crystal tapers off. The 
 taper too is six-sided. Some- 
 times both ends have such a ter- 
 mination. Whenever, in study- 
 ing minerals, you find a very hard 
 glassy mineral which is not so 
 broken but that you can detect a 
 portion of such a form as this, 
 
 that circumstance is probable FIG. 11. A GROUP OF CRYSTALS 
 
 /. ,1 , i . i . OF QUARTZ. 
 
 proof that the mineral is quartz. 
 
 If, in addition, it has a glassy lustre and the hardness 
 of quartz, the proof is conclusive. 
 
 Let us see now how many varieties of quartz we can col- 
 lect. Break the boulders to pieces, and save the pieces 
 which contain minerals too hard to scratch. It is very 
 necessary to know quartz in all its conditions whatever its 
 color, however mixed with other substances. When you 
 can identify quartz with certainty, and distinguish it from 
 two other white minerals next to be considered, you have 
 made excellent advancement. 
 
 EXERCISES. 
 
 Look over the small pebbles before collected, and see whether 
 any quartz exists among them. Are any of them composed 
 wholly of quartz? Examine this washed, clean sand and say 
 whether the grains appear to be quartz. What proportion of all 
 the grains may be considered quartz? Try some sand from 
 another location, and ascertain whether as large a proportion is 
 
40 GEOLOGICAL EXCLUSIONS. 
 
 quartz. Is the fine sand which makes up the greater part of the 
 garden soil quartz ? Is it true then, that quartz forms the greater 
 part of the drift ? Are these grains, pebbles and other boulders 
 angular or rounded ? Were they always as they are now in this 
 respect ? Does it appear that they have been worn ? Why are 
 they not worn completely to powder? Why are there so few 
 boulders of rocks less hard than quartz ? Look at this boulder 
 with a white streak through it ; is that quartz ? Is there any 
 quartz in the rock besides this vein f What makes this white 
 vein project above the general surface ? Can you find a boulder 
 with more than one quartz vein through it ? Can you find a 
 specimen with one quartz vein cutting another ? How many 
 varieties of quartz have you now ? 
 
 EXCITKSIOJST YIL To the Field. 
 The Feldspars. 
 
 Now we have made the acquaintance of one mineral 
 which is almost always light-colored sometimes looking 
 almost exactly like glass. This quartz we find everywhere. 
 It is in almost all rocks. If we should take one hundred 
 pounds of the average rocks, about sixty pounds would be 
 quartz. When we know quartz thoroughly we are acquainted 
 with more than half of all the mass of the earth, so far as 
 it is in sight. 
 
 But there are other white minerals which we found not 
 to be quartz. We must study them further, because we see 
 they are very abundant also. Now we try our steel on a num- 
 ber of them. Those which are not scratched when we press 
 hard we know to be quartz, and take no further notice of 
 them. But see, here is one which we can barely scratch. 
 
TO THE FIELD. 41 
 
 A piece of quartz will also scratch it. Probably we shall 
 find others which scratch quite easily; let us pass these by 
 for the present. 
 
 Now look at this one, which we can barely scratch. 
 Does it look altogether like quartz ? Tell me how it differs 
 from quartz. Has it a real glassy lustre like quartz? Yes, 
 you say ; but after all, it is not quite so glassy. Turn it 
 until your eye catches the light reflected from one of its 
 surfaces. It may be a very small surface ; but if you can 
 catch the reflection, you will perceive that it does not glisten 
 quite so brightly as a quartz surface. If you cannot get this 
 reflection from one surface, try another. You need not 
 break them out of the rock to make these trials. 
 
 Next, tell me if the form is entirely like that of quartz. 
 In the first place the real crystalline form of quartz can sel- 
 dom be seen in a rock mass ; there is no portion of a hex- 
 agonal prism. Yery little of the quartz in an ordinary rock 
 shows that it was broken from a hexagonal prism. But 
 then, in the second place, you can find a form in many 
 rocks which does not belong to quartz. Now look carefully 
 among these whitish minerals which are not quartz, if we 
 may judge by their hardness. You will see here and there 
 some smooth, flat surfaces like a in Fig. 12. Well, quartz in 
 the rocks seldom shows flat, smooth surfaces, 
 as we just now said. But look once more, and 
 you will see that some of these smooth, flat 
 surfaces are bounded, on one side at least, by 
 a straight line. It is not an irregular fracture, 
 as if the surface had been simply broken orf 
 
GEOLOGICAL EXCURSIONS. 
 
 there. You will also perceive that this line is the border 
 of another surface which stands about at right angles with 
 the first surface, like two sides of a box. In the figure, I is 
 this other surface. You see it is long and narrow. Sometimes 
 you may find it wide. Now, have you seen anything in 
 quartz like these two surfaces ? Not at all. This is quite 
 another mineral. We call this mineral Feldspar. 
 
 These are poor specimens of feldspar ; but this is the 
 condition in which we generally find it, and we must learn 
 to know feldspar as it ordinarily occurs in the rocks. Yery 
 often, however, we meet with O ood specimens, which show 
 the form quite completely. If we can find a vein of whitish 
 mineral in a rock of some other kind, we shall be likely to 
 get a better view of the crystalline form, as we call it. 
 Here is a crystal which will enable 
 you to understand more clearly the 
 form and lustre of feldspar. The flat 
 surfaces are called faces or planes. 
 See, here, one plane, li, at right angles 
 with another, li. Also O at right 
 angles with li. Who among us has 
 the best crystal of feldspar? Every 
 person must keep the best he has 
 until he finds a better. 
 
 Now, we have talked about feldspar 
 as if it were one kind of mineral, like 
 quartz ; but, in truth, we have several 
 
 species of feldspar. Most commonly feldspar has a cream col- 
 or or pinkish color. Sometimes it is very white. Sometimes 
 
 FIG. 13. LARGE CRYS- 
 TAL OF ORTHOCLASE, 
 A SPECIES OF FELD- 
 SPAR. 
 
TO THE FIELD. 
 
 43 
 
 it is somewhat transparent, like glass, and has a more glassy 
 lustre than common feldspar f and, in this case, is apt to be 
 composed of thin layers or lamellae. These are likely to be 
 different feldspars ; but we must not try to name different 
 species till we have made more advancement. There is an- 
 other little peculiarity of certain feldspars. Often, when the 
 light reflected from the surface strikes the eye, very fine 
 parallel lines or striae may be seen. These generally indi- 
 cate a feldspar which is not the common species. Let us 
 look carefully for a surface having these lines. Do not look 
 too long in one rock. Try another. Sometimes all the feld- 
 spar in one rock will be of the common kind, while in an- 
 other it will present the striated surfaces. In making the 
 examinations you should have a cheap 
 pocket magnifier. When you learn how 
 to use it you will find it almost as indis- 
 pensable as a pocket knife. (See Fig. 14.) 
 
 If you are unable to collect these dif- 
 ferent species readily look in some col- 
 lection of minerals, and pick out all the 
 quartz and all the feldspar, and point out 
 the different feldspars. 
 
 The most important difference between 
 quartz and feldspar we have said nothing 
 about, because it does not appear to the eye. Feldspar is 
 made of different elements. Do you remember what is 
 meant by elements ? The chemist knows how to separate 
 feldspar into all its different elements, and ascertain how 
 much there is of each one. We are not prepared to do this 
 
 FIG. 14. MAGNIFY- 
 ING GLASSES. 
 a, OVAL, b, BELLOWS- 
 SHAPED. 
 
44 GEOLOGICAL EXCURSIONS. 
 
 for ourselves ; but we will do it, if we stick to the study. 
 Well, the chemist has ascertained that all feldspars contain 
 silicic acid, alumina and some alkali. Now the acid unites 
 with the base alumina, and if the alkali were not present, 
 there would be formed simply silicate of alumina, which is 
 also called aluminum silicate. The acid also unites with 
 the alkali, and if the alumina were not present there would 
 be formed simply a silicate of some alkali. But as all are 
 present, there is formed silicate of alumina and an alkali. 
 Now, there are several alkalies. Potash, soda and lime are 
 alkalies. Either one of these may be the alkali in a feld- 
 spar ; and that is the way we get different species of feld- 
 spars. So one is a potash feldspar and that is the most 
 common feldspar (Orthoclase). Another is a soda feldspar 
 and that is generally white (Albite). Another is a lime 
 feldspar and this is glassy and transparent (Anorthite). 
 Others are soda lime feldspars ; and one of these is gray, 
 brown or greenish, and sometimes shows a beautiful play of 
 colors in reflected light (Labradorite). Another (Oligo- 
 clase) is white, with a faint greenish tinge, and fine striae 
 on the principal surfaces. But you need not learn all these 
 names at present. All the feldspars mentioned which are 
 not orthoclase may be called Plagioclase. 
 
 Any feldspar is composed of silica, alumina and an alkali. 
 The different colors are caused by minute quantities of iron 
 and other substances. If we take one hundred pounds of 
 common feldspar, about sixty-five pounds are silica, eighteen 
 pounds alumina, fifteen pounds potash, about one pound 
 iron ; and the remaining pound is soda, magnesia and lime. 
 
TO THE FIELD. 45 
 
 When feldspar decomposes it forms a pure white clay called 
 Kaolin. Feldspar is used extensively in the manufacture of 
 porcelain. 
 
 Feldspars are very common in crystalline rocks. Fine 
 specimens occur in St. Lawrence and Orange counties, New 
 York. Also in Haddam and Middletown, Connecticut; and 
 at Royalston and Barre, Massachusetts. Fair specimens 
 may be had in boulders all over the northern states. 
 
 EXERCISES. 
 
 Now, how many specimens of quartz and feldspar have you ? 
 Are all your specimens of quartz different varieties ? Have you 
 a specimen of pink feldspar? Have you a specimen of pink 
 quartz ? How does the pink quartz differ, to your eyes, from the 
 pink feldspar ? Have you a specimen of cream-colored feldspar ? 
 What other minerals, so far as you can answer, were in the same 
 rock with it ? Show me a feldspar with striations. Is it more 
 or less glassy than one without striations ? Is it orthoclase or 
 a plagioclase ? Can you see the striations with the naked eye ? 
 Here is a piece of common feldspar weighing one hundred grains ; 
 how many grains of silica in it ? How many grains of potash ? 
 What constituents of feldspar contain oxygen ? What are the 
 different elements in common feldspar ? Try and find a piece of 
 dark feldspar. Do all your specimens of feldspar show some of 
 the peculiar crystalline forms of the mineral ? Take your chem- 
 ical cards and arrange them so as to show the composition of 
 common feldspar. Also the composition of other feldspars. 
 
46 GEOLOGICAL EXCURSIONS. 
 
 EXCURSION VIIL To the Field. 
 Calcite. 
 
 I wish you next to make the acquaintance of another 
 light-colored mineral. It is much softer than feldspar, and 
 you will not be very likely to find it scattered through bould- 
 ers containing feldspar and dark minerals. We had better 
 look for veins or seams of white mineral matter cutting 
 through other rocks. We shall probably find some among 
 the boulders. Ah, here is a white vein. Try your steel on 
 it. Is it hard? Can't you scratch it? Then you know it 
 is a quartz vein. Besides, see how glassy it looks. We 
 may find many quartz veins. Here is a soft vein very 
 much softer than feldspar. The steel scratches it very 
 easily. Certainly, then, it is neither feldspar nor quartz. 
 This is probably our Calcite. Now let us inspect it as we 
 did feldspar. Can you find a smooth face anywhere ? 
 There may be plenty of them. Well, look at this face or 
 flat surface ; how smooth, shining and even it looks ! It 
 does not seem to be a common fracture. How much like 
 feldspar it is ! And yet it is not so pearly as feldspar. Do 
 you see one straight edge to this face ? Search till you find 
 a face which shows a straight bounding edge. Here it is. 
 The face a is bounded by the straight line m n. 
 Now you can see that the line shows where the 
 face a is cut by another plane, b. This is just like 
 feldspar, you say. Not quite, for you perceive 
 that these two faces do not make a right angle 
 with each other. The angle is considerably more 
 
TO THE FIELD. 47 
 
 or less than a right angle. That makes the plane angle at 
 m either acute or obtuse. How is it in jour specimen ? 
 
 You can even detect something further. A close exam- 
 ination of the face of your crystal probably shows fine lines 
 like cracks running across or partly across. There are two 
 sets of them. One set runs exactly parallel with the side 
 m n, and the other parallel with another side. These are 
 cleavage lines. The crystal breaks most easily along those 
 lines. Very likely you might break out fragments which 
 would show several faces even six faces, somewhat 
 perfect, all bounded by lines parallel on opposite sides. 
 Here is a fine large specimen. We often find such. They 
 
 are generally rather opaque ; but sometimes 
 
 they are clear as glass. You must remem- 
 ber seeing such crystals on some one's 
 mantel or " what-not," or in some cabinet FIG. ie. CRYSTAL 
 
 OF CALCITE. 
 
 of specimens. You can generally detect 
 
 cleavage lines on the surfaces of these specimens. This is 
 
 calcite. 
 
 But this handsome mineral often presents itself under 
 another form, called dog-tooth spar, be- 
 cause resembling somewhat the canine 
 tooth of a dog. Here is a figure of a 
 couple of such crystals grown together, 
 as we generally find them. 
 
 This mineral is largely composed of 
 lime. It is by far the most important 
 lime-containing mineral. If we take one 
 
 i-ii . r, i ., . . FIG. 17. DOG-TOOTH 
 
 hundred grains of pure calcite it contains SPAR . 
 
48 GEOLOGICAL EXCUKSIONS. 
 
 forty-four grains of carbonic acid and fifty-six grains of 
 lime. It is therefore carbonate of lime also called cal- 
 cium carbonate. This is the same composition as chalk. 
 What will be the eifect of a little dilute acid applied ? It 
 should effervesce like chalk. To make sure of a fair test, 
 it is better to pulverize the calcite and drop a little acid 
 on it in a test tube. 
 
 There are two other minerals quite similar to this, differ- 
 ing chiefly in having magnesia in place of all the lime 
 (which makes Magnetite), or about half of it (which makes 
 Dolomite). But it will not be best to attempt to study them 
 at present. They do not effervesce so readily as calcite. The 
 pulverized mineral in the test tube with dilute acid must be 
 heated to produce active effervescence. 
 
 Now you have made the acquaintance of the three most 
 important white or light-colored minerals. If you know them 
 well, and can always distinguish each one from the others, 
 you can make good headway in naming rocks as soon as 
 you know two or three of the dark minerals. Calcite you can 
 certainly distinguish by its comparative softness. Feldspar 
 can generally be distinguished by its hardness and lustrous 
 cleavage faces. Though generally somewhat glassy, they 
 are seldom as glassy as quartz. After a good deal of prac- 
 tice you will be able to decide at a glance that the feldspar 
 is generally more pearly than quartz. In any case, the 
 cleavage planes, if you can detect any, will decide the case. 
 Hold the specimen so that you get reflected light. Turn it 
 in different positions, until the reflected light reveals a 
 cleavage plane. The u glassy feldspars," it must be con- 
 
TO THE FIELD. 49 
 
 fessed, will sometimes trouble you. They look extremely 
 like quartz in lustre, and the crystals are often so broken up 
 that it is difficult to detect unmistakable cleavage planes. 
 But we must keep trying and searching. Yery seldom is it 
 really impossible to distinguish feldspar from quartz, either 
 by lustre, cleavage planes, lines, angles or inferior hardness. 
 
 EXERCISES. 
 
 Which of the three white minerals contain silica ? What is 
 in calcite and not in feldspar ? What is in feldspar and not in 
 calcite ? What is in feldspar and not in quartz ? Suppose you 
 have a square box, and, placing your hand on one corner, crush 
 it over by pressing toward the opposite corner at the bottom, 
 which mineral does the box now resemble in form ? How must 
 you press the box to produce the form of one of the other min- 
 erals ? Did you ever see a crystal of transparent calcite ? Take 
 one if you have it, and lay it on a printed line ; what is peculiar 
 in the appearance of the line ? Have you found any brown crys- 
 tals soft as calcite ? Have you any brown crystals with curved 
 surfaces? The brown crystals probably contain magnesia. Try 
 and detect some intermediate forms between calcite and dog- 
 tooth spar. Inquire among your friends for specimens of crys- 
 tals, and see what minerals they are. Of course you can't name 
 them all yet. Please do not neglect this, for we shall get much 
 help in this way. Some specimens worth nothing where they 
 lie may be exactly the things which a student wants to see. 
 
50 GEOLOGICAL EXCUKSIONS. 
 
 EXCURSION IX. To the Field. 
 The Micas, Hornblende and Talc. 
 
 There are two or three dark minerals of first import- 
 ance. One of these is Mica, although it is not always 
 dark. Almost every one is familiar with transparent mica 
 as used in our stoves ; but we will go among the boulders 
 again for the purpose of studying it as it enters into the 
 formation of rocks. "We will seek a boulder with whitish 
 and dark varieties of minerals mixed together. We shall 
 soon find one in which the dark mineral exists in small 
 thin scales, or piles of thin scales. That is mica. Some 
 people ignorantly call it isinglass. Now select the largest 
 specimen at hand and try with a knife-blade to separate 
 the thin leaves. You see there is almost no limit to the 
 possible splitting of the mineral. If the mica is bright, 
 the leaves are elastic and tough. If it is dull, the mica is 
 softer and less elastic. In some rocks the mica is all dull. 
 In hardness mica is not far from calcite. Common mica is 
 transparent or translucent, and is generally brown, pale- 
 green or white. Deep-black mica is another species (Bio- 
 tite). In New Hampshire there are plates of mica over a 
 yard in diameter. 
 
 Now, as to substances in its constitution, we must say 
 that mica is the name of a family, as in the case of feld- 
 spars. But the micas all contain silica, alumina and pot- 
 ash, and almost always iron. The common mica (Mus- 
 covite) contains much iron, and that seems to give it its 
 dark color. It also contains magnesia and soda. Water 
 
TO THE FIELD. 51 
 
 is often present, and that causes the duller lustre, lighter 
 color and less elastic leaves (Hydromica or Margarodite). 
 
 Mica is a mineral which you can hardly mistake. Let 
 us examine next another dark mineral called Hornblende. 
 It is sometimes green or dark green, and frequently black. 
 It is exceedingly common in the boulder rocks in all the 
 northern states. It has about the hardness of feldspar, 
 and if you scratch it the streak is white or whitish. You 
 can generally detect a crystalline face, and sometimes you 
 find a crystalline form like a four-sided rod. Sometimes 
 the structure is lamellar that is, in layers which are much 
 thicker than the leaves of mica, and are not elastic, but 
 are apt to break as you attempt to lift them up. Many 
 times, however, you will not find any crystalline face. 
 The hornblende is simply a shapeless 
 fragment closely imbedded among other 
 minerals. 
 
 This is also a silicious mineral, and it 
 generally contains much iron, magnesia, FIG. is. CRYSTALS 
 
 OF HORNBLENDE. 
 
 alumina, and lime. There are many vari- 
 eties, some of which are white and fibrous (Tremolite, 
 Asbestus). One variety (Actinolite) consists of bright- 
 green, radiating fibres. There is also another mineral 
 (Augite) very similar to hornblende, but more inclined 
 to greenish and whitish colors, and less commonly to 
 black though it is sometimes black. It has cleavage 
 surfaces nearly at right angles with each other. But it 
 is difficult to distinguish augite from hornblende by any 
 means which we can at present employ, though it is 
 
52 GEOLOGICAL EXCURSIONS. 
 
 very important for the geologist to do it. Augite is 
 quite common. 
 
 There is only one other mineral to be troubled with in 
 this course of study. That is Talc. It occurs often in 
 thin scales like mica, and glistens somewhat. You might 
 easily mistake it for mica. But let us take a specimen 
 and pick apart the thin scales. See how soft this mineral 
 is. It is the softest mineral in the world. When you lift 
 up a scale does it tend to spring back on removing your 
 knife ? No, you say. Well, these scales are not elastic. 
 The scales of mica are elastic. These are two excellent 
 ways for separating rnica and talc. Sometimes they may 
 be separated by the color, for talc is pale and silvery- 
 greenish, and never black. The chemist tells us, more- 
 over, that talc is a magnesian mineral. It contains silica, 
 magnesia and water. It is a silicate of magnesia. 
 
 Talc always feels smooth and greasy. Eemember this 
 when you find a specimen large enough to test by the feel. 
 Soapstone is nothing but talc all crushed and compacted 
 together. It is sometimes made into inkstands and grid- 
 dles and foot-warmers. What the well-borers call soap- 
 stone is only clay shale or indurated clay. 
 
 EXERCISES. 
 
 Now let us think over some of the things learned. What is 
 the name of the glassy mineral? What are the white minerals? 
 Are they always white ? What are the two scaly minerals ? 
 What minerals are sometimes black? Which is the softest of 
 the white minerals? Which is most glassy? Which is the softest 
 of the black minerals ? Which mineral effervesces when acid is 
 
TO THE FIELD. 
 
 53 
 
 applied ? Why does not hornblende effervesce? Which ones 
 of all these minerals will scratch calcite? Which will calcite 
 scratch ? Which cannot be scratched by any of the others ? 
 Which minerals contain silica? Which contain iron? Which 
 calcium ? Which magnesium ? Which aluminum ? What 
 other chemical elements exist in any of these minerals? Which 
 ones are most easily detected by their crystalline form ? Which 
 by its hardness? Which by its softness? Have you ever seen 
 the crystalline form of mica in any rock ? What minerals are 
 often green or greenish ? Which minerals sometimes occur 
 black and sometimes white? Which one is sometimes shaped 
 like needles? Which like fine silk fibres? What minerals are 
 likely to be kinkish ? What ones of a cream color ? Which 
 ones will scratch glass? Which cleave most readily? Which 
 least readily ? 
 
 Here is a table showing the composition of all these minerals. 
 Their names will be seen at the head of the columns, and the 
 names of the various substances which combine together to form 
 the minerals are at the left. In the case of feldspar we have 
 considered simply common feldspar (Orthoclase), with its most 
 common composition. The same is true of mica and hornblende. 
 The figures show how many pounds or grains of each element are 
 present in 100 pounds or grains of the mineral. 
 
 
 Quartz. 
 
 Feldspar. 
 
 Mica. 
 
 Horn- 
 blende. 
 
 Talc. 
 
 Calcite. 
 
 Silica, 
 
 100 
 
 65 
 
 45 
 
 47 
 
 62 
 
 
 Alumina, 
 
 
 18 
 
 32 
 
 12 
 
 
 
 Alkali, . 
 
 
 15 
 
 10 
 
 
 
 
 Magnesia, 
 
 
 
 . . 
 
 15 
 
 31 
 
 
 Lime, 
 
 
 
 1 
 
 11 
 
 
 56 
 
 Iron Oxide, . 
 
 
 1 
 
 5 
 
 12 
 
 2 
 
 
 Carbonic Acid, . 
 
 
 
 
 
 
 44 
 
 Water, 
 
 
 
 4 
 
 
 4 
 
 
 Other Substances, 
 
 
 1 
 
 3 
 
 3 
 
 1 
 
 
 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
54 GEOLOGICAL EXCURSIONS. 
 
 EXCUKSION X. Among the Moulders. 
 Quartzose Hocks. 
 
 Let us continue our wanderings among the boulders. 
 We are ready now to learn the names of some of the 
 commonest rocks. The rocks are composed of mixtures 
 of minerals, or, in a few cases, of single minerals. The 
 majority of all the rocks are formed from the six common 
 minerals which we have studied. This seems surprising ; 
 but we must remember that each mineral may present 
 many variations in color, and that feldspar and mica exist 
 each in several species. Then, again, the same minerals 
 may exist in different proportions in different rocks, and 
 the minerals may be in different conditions as to fineness 
 and as to crystallization. Also, rocks having the same 
 mineral ingredients may differ in structure. All these 
 things we will now proceed to see for ourselves. 
 
 One of the very commonest of rocks in all the northern 
 states and among the pebbles of the southern states is 
 composed of a single mineral, and that mineral is quartz. 
 The name of the rock is Quartzite ; but there are almost 
 endless varieties of it. Let us find a white boulder nearly 
 uniform in color. Here it is. Test it for hardness. Is 
 it as hard as quartz ? If not, we will pass it by. If this 
 white rock is as hard as quartz, then it is one variety of 
 quartzite. The farmers would say it is a " flint rock," or 
 a "hard head." Now look closely at it. Yery probably 
 you will notice some variation in color in different parts. 
 Probably, also, you can discover an obscure bounding line 
 
AMONG THE BOULDERS. 55 
 
 to the differently colored parts. If, however, the bound- 
 ing lines are indistinct, and the whole rock breaks through 
 like glass, this is a vitreous quartzite. Some vitreous 
 quartzites show quite striking contrasts of color in dif- 
 ferent parts. These are apt to be coarse or conglomeritic. 
 Let us find a vitreous quartzite which is jaspery. 
 
 In many quartzites the different parts, whether of dif- 
 ferent colors or not, are clearly so many different pebbles 
 or cobble-stones. The rock seems to be a mass of rounded 
 quartz stones cemented together. This is a quartzose 
 conglomerate. There are also, sometimes, conglomerates 
 composed of rounded stones which are not quartzose, 
 Also, many conglomerates have the different stones feebly 
 cemented together. But here we come on something dif- 
 ferent. It is a quartzite composed, evidently, of grains of 
 sand, for we can see the outlines of separate grains 
 throughout. Well, this is a granular quartzite. 
 
 Now suppose the granular quartzite to be a little less 
 firmly cemented. It is simply a coarse sandstone or grit. 
 When you break this sort of rock you do not notice the 
 glassy lustre of the quartzites. The grindstone is a sand- 
 stone. The "Nova Scotia stone" so much admired for 
 building purposes is a sandstone, and so is the u brown 
 stone " used so extensively for fine buildings in New York 
 and other eastern cities. It is found in great abundance 
 along the valley of the Connecticut River and in northern 
 New Jersey. Throughout the states of New York and 
 Pennsylvania are many reddish, yellowish and grayish 
 sandstones. In Ohio are many quarries of beautiful build- 
 
56 GEOLOGICAL EXCURSIONS. 
 
 ing stones known as "Waverly sandstone. The sandstones 
 and grindstones from Berea and Cleveland are mostly of 
 a grayish and bluish color, and much admired for window 
 sills and caps. In Michigan very similar stone is quarried 
 at Point aux Barques on Lake Huron. In the southern 
 part of the state the same stone is often quite reddish. 
 In Ottawa county it is bluish. In Iowa, at Burlington and 
 in that neighborhood, it is yellowish. Other kinds of 
 sandstones are always likely to be found in the vicinity of 
 beds of coal. Often they have black charcoal-like specks 
 in them. Sandstones are liable to contain various impu- 
 rities, consisting most frequently of lime or clayey matter 
 or iron-oxide. Many sandstones have minute mica-scales 
 scattered through them. These are micaceous sandstones. 
 
 EXERCISES. 
 
 It is time to get together all our specimens of quartzose 
 rocks. There are endless varieties, although only one of our six 
 common minerals has been employed in their formation. Please 
 pick out the specimens which you think might be called quartz- 
 ites. Are all the rest sandstones? What is the difference 
 between a sandstone and a quartzite ? Are both quartzose ? 
 Are both silicious ? Have you any granular quartzites ? Sepa- 
 rate them from the others. What kind of quartzites are the 
 others? What is the most compact variety of quartzose rocks? 
 Show me a jaspery quartzite if you have it. Show me a quartz- 
 ite with dark flints in it. Have you noticed any mica-scales in 
 any quartzite? What other minerals have you seen in any of 
 your quartzites? Is there any feldspar or hornblende? Have 
 you seen any quartzite with black straight crystals running 
 through it; and are they hornblende? Are the sides curved 
 and unevenly striated ? If so, they may be Tourmaline. Have 
 
AMONG THE BOULDERS. 57 
 
 you found any pure quartz running through a rock which was 
 not all quartz ? If so, there was a vein of quartz. Have you 
 found any calcite in contact with quartz? Was it in a quartz- 
 ite ? Do you discover any talc scales in any quartzite ? What 
 is the difference between a granular quartzite and a gritty sand- 
 stone ? What sort of rock is a whetstone ? What is an oil 
 stone ? What is a hone ? Is there anything peculiar about a 
 scythe stone ? Examine a piece of sandstone with your magni- 
 fier and see if you can clearly perceive the grains of quartz. Is 
 the quartz clear or colored ? Do you see anything except grains 
 of quartz ? What seems to hold the grains together ? What is 
 the color of the other material ? Put a drop of your acid on the 
 sandstone; does the rock effervesce? If not, what do you con- 
 clude the other material to be ? If it does, what is indicated ? 
 Would carbonate of lime hold the quartz grains together? Now 
 try and make a sandstone yourself. Put some loose, clean, fine 
 sand in a small box and pour some lime water on it, allowing it 
 to leach through slowly. Then, after an hour or two, pour on a 
 little more. Repeat this a number of times, and then allow the 
 sand to dry, and see if the grains are cemented together. Try 
 this experiment at home and report success when we meet for 
 next excursion. Bring your sandstones with you. 
 
 EXCURSION XL Among the Boulders. 
 Micaceous Rocks. 
 
 We stick to the boulders, and I will tell you why. It is 
 because boulders are found almost everywhere, so that a 
 person in any part of our northern states can easily find 
 specimens of rocks. Another reason equally good is that 
 these boulders are of so many different kinds that almost 
 everywhere may be had all the principal sorts of rocks. In 
 many places rocks which are not boulders may be found, and 
 
58 GEOLOGICAL EXCURSIONS. 
 
 we will examine them by and by; but not at present, because 
 most students do not live near quarries and ledges of rocks. 
 Besides that, we can only find one sort of rock at a quarry 
 or a ledge, generally speaking, while the boulders in one 
 field will furnish ten or twenty sorts of rocks. 
 
 Well, how did you succeed with your experiment ? Did 
 you make any sandstone? Now, that is one way in which 
 nature sticks together grains and crystals to make rocks. 
 But take this rock with mica-scales in it and apply acid. It 
 does not effervesce ; so there is no calcium carbonate in it. 
 But the parts are well stuck together; how is it done? Ex- 
 amine with the lens; do you see any kind of cement? 
 There is nothing of this kind visible and yet how firm the 
 rock is. We must keep this question in mind, as we con- 
 tinue our studies. 
 
 You see mica in this rock; what other minerals do you 
 find ? You say quartz, certainly ; that is right. Mica and 
 quartz have great fondness for each other, and are very 
 generally found in company. But they have a mutual friend, 
 feldspar, which seems to be equally intimate with both mica 
 and quartz. Ah, you say feldspar is here too ? Very likely, 
 as I said. Well, now tell all about the appearance of this 
 feldspar. How do you know it is not calcite? How do you 
 know it is not another variety of quartz? Are you quite 
 sure we have in this rock the three minerals, quartz, feldspar 
 and mica? Is there no other mineral present? Only a very 
 little of something, you say, in one corner of the specimen. 
 Well, no matter for that. But are these three minerals 
 evenly distributed through the specimen, or is the mica 
 
THE BOULDEBS. 59 
 
 more abundant in certain streaks across the rock? Ob, you 
 say the mica is arranged in streaks. Yes, the quartz, too, 
 is not quite evenly distributed. This, then, is a stratified 
 rock. Let us lay it aside, and take another specimen not 
 stratified. There, this is entirely unstratified. But look 
 closely and be sure that it contains quartz, feldspar and mica. 
 Does it? And is there no other mineral somewhat plentiful 
 in it? Well, this rock is what we call granite. Now think 
 this over and state what a granite is. Granite is a most 
 important rock. You have accomplished much when you 
 can be sure whether any rock is a granite or not. Many 
 other rocks are called granite by quarrymen and stone cut- 
 ters ; but you must judge for yourself. 
 
 Take notice. It makes no difference whether the granite 
 is coarse or fine; it is still granite. A fine granite may be 
 better for building purposes 
 than a very coarse one. 
 Sometimes quartz, feldspar 
 and mica are thrown together 
 in so coarse a state that the 
 
 granite is worth nothing as a Fia.lo. -PORPHYRITIC ROCK. 
 
 building stone. A granite Granite from Land's End, Eng- 
 
 land. (Lyell.) 
 
 with large crystals of feld- 
 spar scattered through it, is called a porphyritic granite. 
 Any rock with such feldspar crystals is called porphyritic. 
 
 Take notice again. It makes no difference what is the 
 color of the quartz, or what is the color of the feldspar, or 
 what is the color of the mica. "Well, how many possible 
 variations there must be in the appearance of granites! In 
 
60 GEOLOGICAL EXCURSION'S. 
 
 some, the reddish spots are quartz ; in others, the reddish 
 spots are feldspar. Sometimes, also, there are two kinds of 
 quartz. Sometimes there are two kinds of feldspar. Some- 
 times there are two kinds of mica. A good way for us is to 
 go to a stone cutter's and examine different sorts of granites. 
 
 Take notice the third time. Some granites contain but 
 little mica, and then the rock may be very light-colored. 
 But, if either the quartz or feldspar is reddish, the rock will 
 be variegated whitish and reddish. In some granites, on 
 the contrary, the mica is exceedingly abundant. If the mica 
 is black it gives a dark complexion to the rock. So the 
 number of varieties of granite is almost endless. In some 
 cases there is almost no mica, and the rock is then a Gran- 
 ulite. If mica and quartz are both wanting, or nearly so, 
 the rock is a Felsite. In some felsites, quartz is intimately 
 combined with feldspar. This forms a Petrosilex if the 
 feldspar is orthoclase, and a proper Felsite if the feldspar 
 is a plagioclase. Granite blocks are often used for street 
 paving. 
 
 You remember that all the granites are unstratified. We 
 had at first a rock with the constituents of granite, but we 
 found it stratified, and laid it aside. Here it is. Such a 
 rock we call Gneiss (pronounced Gn-ice, not Gne-iss). Of 
 course now, there may be just as many varieties of gneiss as 
 of granite. Some varieties are so little stratified that one 
 would take them for granites unless we had large samples 
 to examine. Such gneisses always pass for granites among 
 stone-cutters. Many of them are quite as valuable as gran- 
 ites for building purposes. 
 
AMOKG THE BOULDEKS. 61 
 
 But here is a micaceous rock which is very distinctly 
 stratified. See how abundant is the mica. It is arranged 
 in courses of varying thickness, and between the courses is 
 what? Well, it is mostly quartz in grains. In one speci- 
 men it is wholly quartz ; in another we can detect a little 
 feldspar. Kow, such a rock we call Mica Schist (pronounced 
 Shist). A schist is any rock composed of beds or layers of 
 crystalline minerals. There are many sorts of schists, as 
 we shall see. Perhaps if we look around, we shall discover 
 a mica schist with garnets in it. Every one knows garnets. 
 We will keep this question in mind. If the mica is soft and 
 lustreless we have a Hydromica Schist. We shall certainly 
 meet with such. Mica schists are much used for sidewalks. 
 
 Occasionally we find an unstratified, granite-like rock 
 consisting of quartz and mica. This is called Greisen (pro- 
 nounced Gri-sen). But a little mica in a common quartzite 
 would make a micaceous quartzite. 
 
 We must not forget about these important rocks. 
 
 EXERCISES. 
 
 Give the names of the micaceous rocks. Which ones are 
 stratified? Which is most distinctly stratified? Suppose a 
 fragment of rock is handed you and you find it unstratified and 
 containing quartz, feldspar and mica, what is its name ? But then 
 suppose another fragment from the same boulder or ledge is 
 stratified; what is the name of that fragment? Then would you 
 say one part of a boulder or ledge is granite and another part of 
 the same is gneiss ? Just exercise your best judgment in giving 
 the answer, for many questions cannot be answered positively. 
 Suppose the part of a ledge which seems to be gneiss ten rods 
 away from the part which seems to be granite, must we call it all 
 
62 GEOLOGICAL EXCURSIONS. 
 
 granite or all gneiss ? Suppose you find a granite boulder or a 
 ledge with a vein of quartz running through it, does that make 
 the ledge or boulder gneiss? Suppose a vein of feldspar 
 runs through it, what kind of rock forms the ledge? Sup- 
 pose a vein is composed of quartz and feldspar intermixed, 
 what kind of rock is the vein ? Does that prevent the ledge from 
 being granite ? Well, suppose the vein is of quartz, feldspar and 
 mica, what kind of rock is the vein ? Does that make the ledge 
 stratified ? May we have two sorts of granite in one ledge or 
 boulder ? Please find a granite in which the feldspar is glassy. 
 Can you find one with a dusky feldspar ? Have you found a por- 
 phyritic granite ? Suppose we could remove the mica from a 
 granite, what would the rock become ? Suppose we find a granu- 
 lite stratified, what should we call it ? Suppose we could remove 
 the feldspar from a granite, what would the rock become ? Did 
 you ever see such a rock ? Did you ever see a rock composed of 
 mica alone ? Did you ever see a rock composed of feldspar 
 alone ? Ask your father or some other person to tell you the 
 composition of granite. Ask some one to tell you the difference 
 between granite and gneiss. If any person asks you such ques- 
 tions, do not fail to answer them satisfactorily. 
 
 Now let us hear about your success in making a sandstone. 
 Show the sandstones made. Is such a sandstone different from 
 old mortar ? Now explain how it is that mortar becomes so hard. 
 What would be the effect if much dirt were mixed with the sand 
 used? 
 
 EXCUKSION XII. With the Stone Cutter. 
 Hornblendic Rocks, 
 
 For the sake of varying our excursions a little we will 
 visit the stone cutter's yard, where many varieties of rocks 
 may be found, such as are used for building and for ceme- 
 tery monuments. In some parts of the West, churches and 
 
WITH THE STOJs'E CUTTEK. 63 
 
 residences are constructed of rough-dressed boulders. The 
 boulders are hauled from the neighboring fields and ravines, 
 and workmen, with heavy sledge hammers, break them into 
 suitable shapes for putting into the walls of a building. 
 Cart loads of freshly broken chips are made, and the vari- 
 eties of rocks which may be picked up are almost endless in 
 number. If all that carting and hammering had been done 
 expressly for the geologist, it could not have been better 
 done. Such a place is even better than a stone cutter's 
 yard ; and we will visit it afterward. 
 
 Here at the stone cutter's. You see rocks white, clouded, 
 reddish, red-mottled and red-specked, gray, black and white 
 variegated, black and red variegated, and other sorts. Now, 
 to-day we wish to study hornblendic rocks. We must look 
 for rocks containing hornblende. "What is the prevailing 
 color of hornblende ? Well, pick out your hornblendic 
 rock. Here it is ; what other minerals do you find in it ? 
 Quartz and feldspar, you say. That is a very common sort 
 of mixture. Here you have the same two minerals in com- 
 pany which you found in granite. But the mutual friend is 
 not mica. It is hornblende in this case. Such a mixture is 
 not granite, whatever the stone cutter may tell you. It is 
 Syenite. Bear that name in mind. It is the same kind of 
 rock as the ancient Egyptians quarried at Syene, in Egypt, 
 and the geologists thought it would be pleasant to name the 
 rock from the place. But it is wonderful that the Syene 
 rock should be found in all parts of the world. 
 
 Notice how much syenite resembles granite. Even some 
 scientific writers include it in granite. We may also have 
 
64 GEOLOGICAL EXCURSIONS. 
 
 numerous varieties corresponding to the varieties of granite. 
 Often the feldspar is reddish, and then we have the so-called 
 " Scotch granite." Some of these syenites are fine, some 
 are coarser. Some have a dark complexion and some a 
 light one. Most of the so-called granites from Maine to 
 Massachusetts are syenite. The Quincy granite, which is 
 sent to New York and the southern states and the West 
 Indies, is a syenite. The custom house and other buildings 
 in "Wall street, New York, are of syenite. The capitol at 
 Albany is chiefly syenite. There is a large amount of syen- 
 ite in the Upper Peninsula of Michigan ; also in northern 
 Wisconsin and Minnesota. Syenite is even more durable 
 than granite. Syenite and granite are both found in enor- 
 mous ledges and mountain masses along the eastern flanks 
 of the Alleghanies to North Carolina. In Ohio you will 
 only find syenite and granite in the form of boulders. The 
 same is true of the Lower Peninsula of Michigan, of Indi- 
 ana and Illinois. 
 
 It often happens that some mica is present in syenite, 
 and then we have a micaceous syenite. If the mica is nearly 
 as abundant as the hornblende we have a syenitic granite. 
 If the mica is much more abundant than the hornblende, 
 the rock is a granite, but it is hornblendic. Let us look 
 around and find some of these species of rocks in the stone 
 yard. 
 
 We shall have to go back to our boulders, after all, to 
 get all the sorts of hornblendic rocks. Now here is a syen- 
 ite-looking rock, but it contains almost no quartz ; what 
 shall we call it? Well, if the feldspar is common feldspar, 
 
WITH THE STONE CUTTEE. 65 
 
 the rock is Hyposyenite which some say is the only proper 
 syenite. Is the feldspar reddish or creamy? Then it is 
 common feldspar or orthoclase. But is the feldspar pure 
 white ? Then it is probably albite. Now, hornblende and 
 albite form a rock called Diorite. This is a handsome rock, 
 with its white and black or greenish colors. Sometimes 
 diorite is coarse enough to enable us to study the minerals ; 
 but sometimes it is very fine, If any other light-colored 
 feldspar not orthoclase is mixed with hornblende, we call 
 the rock diorite also. Diorite is a very tough rock, and 
 makes a building stone of the first class. Diorites are very 
 common about Lake Superior. Also among the boulders of 
 all the northern states. 
 
 If the dark mineral in a diorite-looking rock is not horn- 
 blende, but augite, then the rock is Diabase. So diabase is 
 a rock composed of augite and a feldspar not of the ortho- 
 clase group that is augite and a plagioclase. Some main- 
 tain recently that most of our northwestern rocks heretofore 
 called diorites are in reality diabases. But this is not certain. 
 
 All these hornblendic rocks are unstratified ; but, as with 
 the micaceous rocks, we have many gneissic forms. Syenite 
 stratified is syenitic gneiss. Diorite stratified is dioritio 
 gneiss. Diabase stratified is diabasic gneiss. If the feld- 
 spar in a syenite is supposed diminished and the hornblende 
 increased, and the rock is distinctly stratified, we get a 
 hornblende schist. This corresponds to mica schist. If the 
 quartz is supposed removed from a hornblende schist, little 
 besides hornblende remains, and we have hornblende rock. 
 This is a black rock, and by no means uncommon. It is, 
 
66 GEOLOGICAL EXCURSIONS. 
 
 however, schistose, and has some lustre. Many black and 
 lustreless rocks, not showing distinct crystals, contain other 
 minerals besides hornblende. They are then simply horn- 
 blendic. Sometimes a dark feldspar (Labradorite) is abun- 
 dant in such rocks. But we must not undertake to study 
 this group of rocks at present. We will confine ourselves 
 to rocks in which the crystals are visible to the naked eye, 
 or, at least, with a magnifier. Such rocks are called phanero- 
 crystalline ; and those in which you cannot distinguish sepa- 
 * rate crystals are called cryptocrystalline. These are pretty 
 long words, but they are no stranger than you can find by 
 the dozen in any fashion book. 
 
 Take notice. In both the micaceous and the hornblendic 
 series of rocks, we have mixtures of minerals which may be 
 unstratified, or may be obscurely stratified, or may be very 
 distinctly stratified. Now let us call the first kind massive, 
 the second gneissoid, and the third schistose. 
 
 Just as we have micaceous and hornblendic rocks, so we 
 may have a series of talcose rocks. Quartz, feldspar and 
 talc, when massive, give us Protogine ; when gneissoid, 
 protogine gneiss ; when schistose, talcose schist, since, in the 
 latter case, very little feldspar is ever found. When a schist 
 consists almost wholly of talc, it is a talc rock / and if the 
 talc is pulverized and closely packed, the rock is steatite. 
 
 EXERCISES. 
 
 Now let us review again. Sit down by your collection of 
 rocks and pick out all the hornblendic specimens. Next sort out 
 those which are true syenites. Lay aside the hyposyenite. Pick 
 out the diorites. Arrange the syenites according to their coarse- 
 
WITH THE STOJJE CUTTER. 67 
 
 ness. Now arrange all the massive hornblendic rocks according 
 to the amount of quartz in them. Next arrange the gneissoid 
 and schistose rocks of the hornblendic series according to the 
 amount of quartz in them. Suppose the hornblende in all these 
 schistose rocks should change to mica, what would their several 
 names become? Suppose it should change to talc, what would 
 the names become ? Take a specimen of syenite in hand and 
 suppose the hornblende to change to mica, what does the rock 
 become ? Suppose the hornblende to change to feldspar, what is 
 the name of the rock? But if you hold syenite and the quartz 
 changes to feldspar, what is the rock? If the quartz changes to 
 hornblende, what is the rock ? Now, if you take hyposyenite, 
 what kind of feldspar is in it? If the orthoclase changes to 
 albite, what does the rock become? What, if it changes to 
 oligoclase? If you take hyposyenite and add mica, what might 
 we call the rock? If we add talc instead, then what? What 
 sort of rock is the glistening scythe stone ? Which is the tough- 
 est rock, diorite or granulite ? Look on the weathered surface of 
 a granitic or a syenitic boulder, and state what mineral projects 
 most. Which has changed its color most? Which weathers 
 most rapidly, hornblende or feldspar? What change in lustre 
 does feldspar undergo in weathering ? 
 
 You must be very particular to see for yourselves all the 
 things about which these questions are asked. When you go 
 home tell your people what hyposyenite is, and ask them to 
 explain diorite. 
 
 REVIEW. 
 
 Here is a table to assist the memory and to aid in review. 
 The minerals studied are placed at the top of the columns. At 
 the side also are placed the minerals, as well as the names of 
 rocks formed of two minerals; as also syenite. Then the names 
 of rocks formed by uniting minerals and rocks named at side and 
 top are found in the spaces where the vertical and horizontal col- 
 umns intersect. Rocks whose names are printed in small capitals 
 are massive ; those whose names are in ordinary letters are gneiss- 
 

 
 
 
 
 
 
 
 
 j, 
 
 
 i 
 
 
 K 
 
 i 
 
 
 
 
 
 
 
 
 : 
 
 .I| 
 
 
 W 
 
 
 P 
 
 02 
 
 
 
 
 
 
 
 
 
 
 S'g,^ 
 
 
 80 W 
 
 
 1 
 
 
 
 
 
 
 
 
 
 t! 
 
 2^0 
 
 
 O H 
 
 
 Q 
 
 
 
 
 
 
 
 
 
 a~ 
 
 O "o -^ 
 
 
 J *5 
 
 
 ^ 
 
 
 
 
 
 
 
 
 
 SS 
 
 ^ 
 
 
 H ^ 
 
 
 H 
 
 a 
 
 
 
 
 
 
 1 
 
 
 
 4 | 
 
 
 
 
 
 0> 
 
 
 
 
 
 
 H V 
 
 
 
 c 
 
 
 
 
 
 p 
 
 * 
 
 * 
 
 * 
 
 * 
 
 
 I] 
 
 
 
 .til 
 
 
 
 
 
 E3 
 
 
 
 
 
 
 S3 
 
 
 
 ess 
 
 
 
 
 
 H 
 
 
 
 
 
 
 II 
 
 
 
 s^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 2 
 
 
 B.S 
 
 
 
 
 
 
 
 
 
 
 
 
 P 
 
 
 l| 
 
 
 
 
 
 
 
 
 
 
 
 * 
 
 
 to . 
 
 
 gS ^^ 
 
 g 
 
 
 
 
 
 
 
 
 
 w 
 
 
 O H 
 
 
 
 
 
 
 
 
 
 
 
 
 S.2 c 
 
 
 r i% 
 
 
 lc ll 
 
 
 
 
 
 
 
 
 
 
 as c^ 
 citi^ 
 
 
 i& 
 
 
 III 2 
 
 9 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 3 
 
 
 
 
 
 
 11 
 
 QC 
 
 S 
 
 
 
 
 
 
 
 fo 
 
 * 
 
 
 
 
 
 g!| 
 
 1 
 
 g? 
 
 
 
 || 
 
 
 
 
 
 
 
 
 
 
 
 2.S .5 
 
 1 
 
 
 
 Hi 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 w 
 
 
 
 M 
 
 1 
 
 * 
 
 
 
 
 
 |1 
 
 .i 
 
 
 
 111 
 
 
 
 PI 
 
 < 
 
 
 
 
 
 
 DIORITI 
 Dioritic 
 Dioritn 
 
 DlABASl 
 
 Diabas 
 
 
 
 
 
 
 B 
 
 6 
 
 
 
 
 
 
 o 
 
 41 
 
 A 
 
 E 
 
 
 
 
 
 
 
 s 
 
 
 
 
 
 
 . 
 
 h 
 
 
 
 
 
 
 
 -3 
 
 * 
 
 
 
 
 
 H * 
 
 B 
 
 
 
 tt 
 
 
 
 
 I 
 
 o 
 
 
 
 
 
 
 SM 
 
 AUGITE 
 
 NITK. 
 
 
 
 GRANITE. 
 Gneiss. 
 3ftca Sch 
 
 
 
 
 Quartz. 
 
 Quartzite. 
 Quartz Schist. 
 Silicious Schist. 
 Sandstone. 
 
 GRANULITE. 
 Granulitic Gneiss. 
 Granulitic Schist. 
 
 ALBITIC GRANTJLITE 
 Granulitic Schist. 
 
 OLIGOCLASIC GRAN- 
 ULITE. 
 Granulitic Schist. 
 
 GREISEN. [ite. 
 Micaceous Quartz- 
 Mica Schist, [stone. 
 Micaceous Sand- 
 
 Hornblendic 
 Quartzite. 
 Hornblende Schist. 
 
 &s 
 
 1 
 
 Talcose Quartzite. 
 Talcose Schist. 
 
 
 
 SYENITE. 
 Syenitic Gneiss. 
 Hornblende Schist. 
 
 ALBITIC SYENITE. 
 Syenitic Gneiss. 
 Dioritic Schist. 
 
 
 
 
 d 
 
 
 
 
 
 4 
 
 
 
 
 
 
 
 
 
 d 
 
 1 
 
 <D 
 
 1 
 
 
 5 
 
 m 
 
 
 g 
 
 A 
 
 H 
 
 
 . 
 
 
 I 
 
 a 
 
 s 
 
 
 O 
 
 i 
 
 o 
 
 
 
 I 
 
 i 
 
 1 
 
 GREISE 
 
 H 
 
 W 
 
 i 
 
 5 
 
 cc 
 
TO THE MARBLE YARD. 69 
 
 old, and those whose names are in italics are schistose. Some of 
 the unfilled spaces might receive the names of rocks not men- 
 tioned ; but it is best not to be troubled with rare rocks. Also 
 the spaces at the upper right hand, containing stars, might be 
 filled with the same names as are in other parts of the table. 
 The pupil may exercise himself in doing it. 
 
 EXCURSION XIII. To the Marble Yard. 
 
 Calcareous Rocks. 
 
 You must have noticed that none of the rocks which we 
 have studied thus far contain any calcite. It might be that 
 calcite crystals should occur sparingly in some of these rocks, 
 but they are not essential. If they should so occur we 
 might describe the rock as calciferous. But when a rock is 
 composed chiefly of calcite we call it calcareous. There are 
 many such rocks. 
 
 Here we are in the marble yard. Nearly all marbles are 
 calcareous. The stone cutter has many varieties of marbles. 
 Pick up some of these marble chips and test them for hard- 
 ness. They are all rather soft. Test some of them with 
 acid. They all effervesce. If you find a rock having the 
 hardness of marble, which does not effervesce, it is probably 
 formed of dolomite instead of calcite or at least, in part of 
 dolomite. Pulverize a bit, put the powder in a test tube, 
 pour in a little dilute acid and heat the tube. Now you 
 perceive effervescence. Yes, this is also a carbonate, and the 
 acid with heat (if not without) drives off the gaseous car- 
 bonic acid. 
 
 You will notice that some of these marbles are coarse. 
 
70 GEOLOGICAL EXCURSIONS. 
 
 If you look closely you will perceive plenty of crystalline 
 faces. It looks as if a quantity of calcite crystals had been 
 broken and compacted together. The so-called Potomac 
 marble is of this kind. It has been used in building the 
 Washington monument. It is too coarse for fine work. 
 Here is a granular marble, white like loaf sugar, and having 
 the texture of loaf sugar. Such marbles are called sacchar- 
 oidal. Here, next, is a finer marble. It only differs from 
 the last in fineness. The finest marbles may be used for 
 making statues. For this reason they are called statuary 
 'marbles. 
 
 Some marbles are colored in various ways, and thus we 
 get almost countless varieties of them. Many Vermont 
 marbles are clouded and veined with a darker color than the 
 ground color. The ground color itself is sometimes far from 
 white, inclining to a bluish or clay color. Some marbles are 
 reddish. The red color is either uniform or distributed in 
 blotches, clouds or veins. There are some varieties with 
 much dark matter as a ground color, or forming veins. 
 Egyptian marble, so called, is almost black, with occasional 
 veins of a lighter color. All the colorings of marbles are 
 produced by impurities. Reddish colors are often caused 
 by iron oxide closely combined with the calcite. Blackish 
 colors are commonly due to carbon or bitumen disseminated 
 through the rock. Bluish veinings and ground colors seem 
 to be caused by argillaceous (clayey) materials. 
 
 Some fine varieties of marble are produced by the com- 
 bination of distinct bodies. One of the Tennessee marbles 
 is a conglomerate or pudding stone. This is a favorite mar- 
 
TO THE MARBLE YARD. 71 
 
 ble for pillars of public buildings. Sometimes a compact, 
 calcareous rock has numerous forms of corals, shells and 
 other things distributed through it, and if it takes a fine 
 polish, it forms what is called shell marble. 
 
 Light-colored and clouded marbles of various kinds are 
 quarried at various localities from northern New England to 
 Maryland. Western Vermont, Massachusetts and Connec- 
 ticut, and also eastern New York, abound in marble ledges. 
 Black marble is quarried at Shoreham, Vt., and also near 
 Lake Champlain. Yerd-antique marble occurs at Milford, 
 Ct., and also in Essex county, N. Y. This is common 
 marble clouded green with serpentine. Shell marbles are 
 found in Onondaga and Madison counties, ~N. Y. "White 
 saccharoidal marbles, sometimes fine enough for statuary, 
 are found extensively in the regions south of Lake Superior. 
 All over New England and the northwestern states may 
 be found boulders of marble. 
 
 We are still in the marble yard. You notice that the fine 
 cemetery marbles are supported by bases of some sort of 
 rock not marble. This is probably a calcareous rock. Try 
 your acid on it. Does it effervesce ? Well, it is a limestone 
 not crystalline enough to take a fine polish. Still, it is com- 
 posed mostly of calcite. You see it is distinctly stratified; 
 the marbles are not so. There are many varieties of lime- 
 stone ; but there are three characters by which you may dis- 
 tinguish them from most other rocks. 1. They effervesce 
 with acids. 2. They are easily scratched. 3. They are not 
 composed of worn or rounded grains. There is a variety 
 made up largely of uniform spherical pellets stuck together 
 
72 GEOLOGICAL EXCURSIONS. 
 
 by a fine cement, or sometimes imbedded in it, but these are 
 not grains rounded by wearing. It is called oolitic limestone. 
 Limestones may contain various impurities silica, clay, 
 sand, iron, coal, bitumen, petroleum and still other sub- 
 stan^es. So we describe the limestone as silicious, argil- 
 laceous, arenaceous, ferruginous, carbonaceous, bituminous 
 or petroliferous. 
 
 What is chalk? That we found to be capable of effer- 
 vescing. It is simply a soft limestone. There are all grades 
 of limestones in point of hardness, between marbles and 
 chalk. The carbonate of lime precipitated in the bottom of 
 a little lake is marl. It is often mixed with clay or peat. 
 We can frequently find marl beneath the peat of a common 
 swamp. The carbonate of lime precipitated from flowing 
 spring water is travertin and calcareous tufa, as before ex- 
 plained. That which forms in the shape of icicles hanging 
 from the roofs of caves is stalactite. When the same water 
 falls on the floor of a cave and makes a deposit, we call it 
 stalagmite. This is exactly like travertin. 
 
 When limestone is burned, the carbonic-acid gas is driven 
 off and only lime remains. If lime is left exposed to the 
 air, especially if damp or wet, it takes carbonic acid again 
 from the air and water, and is reconverted into carbonate of 
 lime. 
 
 EXERCISES. 
 
 Did you ever notice the crust formed around stones in the 
 bottom of a brook ? What is it ? Where does it come from ? 
 How may stones or grains of sand become cemented together ? 
 What is the stone base of your oil lamp ? Why is marble used 
 
TO THE MARBLE YARD. 73 
 
 instead of quartzite ? How many sorts of marbles have you 
 collected ? Arrange them in order according to their coarseness. 
 How many sorts of limestones have you ? Arrange them accord- 
 ing to their hardness. How does chalk differ from marble? 
 What is the difference between stalactite and stalagmite ? Does 
 a stalactite increase internally or externally ? Does other lime- 
 stone grow ? Which is most compact, marble or quartzite ? 
 What causes the surfaces of marbles long exposed to the weather 
 to turn black ? Can limestone be dissolved in water ? What 
 other rocks or minerals thus far studied can also be dissolved ? 
 Do the rains dissolve limestones ? What effect have limestones 
 on the soil? Are limestone soils desirable for farming purposes? 
 Are sandy soils equally desirable ? Why not ? Have you ever 
 seen a black marble or limestone ? What causes rusty stains on 
 the surfaces of some white marbles ? Which are best stratified, 
 marbles or common limestones ? Suppose you find a limestone 
 with fine sand distributed through it, what is the name of the 
 rock ? What is the taste of lime ? Is lime soluble or insoluble ? 
 When limewater is exposed to the air, what causes the film which 
 forms on the surface ? How does this differ from limestone ? 
 Were limestones formed in this way ? Take an oyster shell and 
 test it with acid ; does it effervesce ? Now burn the shell and 
 see if it becomes lime. Of course you will postpone this until 
 you have a convenient fire. But suppose the shell burned, you 
 will see that it has the acrid taste of lime. Could mortar be 
 made of it ? Take any other shell and test it in the same way. 
 Suppose a common river clam shell (properly called Uhio) should 
 lie in the water until the shell disintegrates, what would the 
 powder be ? Suppose thousands of shells should disintegrate in 
 the same way, what would be found on the bottom of the pond ? 
 Is this the way marl is made ? Suppose calcareous spring water 
 should flow into the pond, would anything be precipitated ? 
 What? How would this differ from marl? Now which way 
 does marl originate ? Which would you think most durable for 
 building purposes, marble or granite ? What causes the parallel 
 
74 GEOLOGICAL EXCUKSIONS. 
 
 lines in a piece of polished stalagmite ? Have you found any 
 fragments of a brown or blackish limestone? If so, rub it 
 smartly with another stone and see whether any odor is emitted ? 
 What variety of limestone is this ? Have you found limestones 
 with hard flinty patches forming what is called cherty limestone ? 
 
 EXCUKSION XIV. To the Clay Pit and the Field. 
 Argillaceous Bocks. 
 
 Let us begin to-day with this broken slate. It has been 
 used in school for writing on, and is called graphic slate. 
 Do you see any indications of quartz or calcite in it 3 How 
 many sorts of minerals does it seem to be composed of? 
 All one kind, you say. Try it with your magnifier. Can 
 you see any crystals or grains ? Not at all. It is very dif- 
 ferent from the granites and schists. Try your acid on it. 
 No effervescence ; it is not a carbonate. Let us put a frag- 
 ment in a mortar and reduce it to fine powder. There, that 
 is done. Now moisten the powder a little, and what does 
 your slate look like ? Like mud, you say. So it is mud. 
 
 Were you ever in a brick yard, or in a clay pit where 
 material is obtained and ground up for bricks ? Well, does 
 the clay make you think of your pulverized slate ? They are 
 in fact both the same. The brick clay probably has some 
 very fine silicious sand disseminated through it. You might 
 dissolve the clay in water and allow the fine sand to settle 
 to the bottom, as it did in the case of the garden soil. The 
 remainder would be almost exactly like this pulverized 
 slate. I must tell you what is the mineral in these sub- 
 
TO THE CLAY PIT AND THE FIELD. 75 
 
 stances which gives them their character ; it is alumina. 
 But this is rather a chemical substance than a mineral. But 
 the aluminous substances are not formed of any distinct 
 minerals, as quartzite and marble are. The alumina enters 
 directly into the formation of rocks. 
 
 Did you ever notice in the coal bin an occasional flat 
 piece of stone called u slate"? You can almost always find 
 some "slate " among the coal. Here is a piece ; try it with 
 your steel. Do you find it as hard as the graphic slate ? It 
 is softer, you say. Well, pulverize a piece, and see whether 
 it makes a similar kind of mud. It does. Now, is there 
 no way to distinguish this from the graphic slate ? It is 
 rough, but that is only because it is in a state of nature. It 
 is softer, you say. But there is no other difference. It is 
 an aluminous rock, but is softer than real slate. We call 
 such a rock shale. 
 
 If we stroll among the boulders again, we shall see some 
 blackish, fine-grained rocks which we never yet ventured to 
 take in hand. Do they seem to be hornblende rocks? No, 
 they have not sufficient lustre. Are they black marble ? 
 No, they are too hard. It is difficult to scratch them. 
 Notice the fine, even lines of stratification ; do they resem- 
 ble a hornblende rock or hornblende schist ? Not at all ; 
 this is a kind of rock not yet studied by us. I must tell you 
 the name. It is argillite. It is composed of alumina and 
 silica closely mixed. It is true that hornblende is also 
 present with some argillites, and so are minute scales of 
 mica. It is also true that some very fine hornblendic rocks 
 resemble this. But the argillite is the rock with which we 
 
76 GEOLOGICAL EXCUKSIOtfS. 
 
 are concerned. Examine it carefully. This is also an 
 aluminous rock. 
 
 Thus we have a series of aluminous rocks ranging from 
 argillite, which is almost flinty, to clay, which can be 
 moulded in the hand. The purest sort of clay is Kaolin. 
 It is nearly white, and we often find it in association with 
 quartz and mica, in such a situation as to show that Kaolin 
 is simply decomposed feldspar. The alkali has been dis- 
 solved out of the feldspar, and some of the silica has disap- 
 peared. What remains is nearly pure alumina and water. 
 So we see how the decomposition of granite or other rocks 
 containing feldspar has given origin to the vast beds of 
 impure blue clay used for bricks, pottery, tiles and other 
 purposes. The pure Kaolin is used for porcelain. Even 
 feldspar is often ground up for the same purposes. The 
 alkali in it gives the ware a translucent, glassy character. 
 
 EXERCISES. 
 
 Suppose, in the decomposition of feldspar, the alkali is not all 
 removed, and the clay resulting is burned, what will be the 
 appearance of the bricks? What causes the red color of common 
 bricks ? Why are some bricks not red ? What is the peculi- 
 arity of Milwaukee bricks? Can you name another locality 
 which affords light-colored bricks ? Why is porcelain whiter 
 than common bricks? What is the cause of the translucency 
 of China ware ? Did you ever observe statuettes of biscuit, 
 or unglazed porcelain, to be called " Parian marble " ? Are they 
 of any kind of marble? Do the sellers seem to think they are 
 real marble ? How do they differ from marble ? What is the 
 difference between graphic slate and roofing slate ? What are 
 slate pencils made of ? Are slates and pencils ever made of any 
 other than an aluminous rock ? What sort of slate pencils could 
 
TO THE CLAY PIT AND THE FIELD. 
 
 77 
 
 be made of steatite? What is the "French chalk" used by 
 tailors? Do all clays belong to the Drift? What are the colors 
 of the slates which you have seen? How are letters and designs 
 sometimes represented upon slated roofs? Of what are the tiles 
 made which are used on floors and about fireplaces? What use 
 do sculptors and modellers make of clay ? When did mankind 
 begin to use clay for pottery? Why are not silicious argillites 
 employed for roofing? How does argillite differ from Egyptian 
 marble ? 
 
 REVIEW. 
 
 Now let us recall some of our lessons. We have had a series 
 of silicious rocks and a series of calcareous rocks, and here is a 
 series of aluminous rocks. Each series begins with rocks which 
 are hard and not well stratified, and ends with rocks which are 
 incoherent or soft. It will aid our memory to get these arranged 
 in order in a table. Here is such a table: 
 
 TABLE OF ARRANGEMENT OF FRAGMENTAL ROCKS. 
 
 GROUPS or 
 ROCKS. 
 
 CRYSTALLINE. 
 
 INDURATED. 
 
 SEMI- 
 INDURATED. 
 
 INCOHERENT. 
 
 SILICIOUS 
 ROCKS. 
 
 Quartzite 
 Vitreous. 
 Granular. 
 Conglomeritic. 
 
 Sandstone 
 Compact. 
 Conglomerate. 
 
 Sandstone 
 Friable. 
 
 Sand. 
 
 ALUMINOUS 
 ROCKS. 
 
 Argillite. 
 
 Slate. 
 
 Shale. 
 
 Kaolin. 
 Clay. 
 
 CALCAREOUS 
 ROCKS. 
 
 Marble 
 Conglomeritic. 
 Saccharoidal. 
 Statuary. 
 
 Limestone 
 Compact. 
 Travertin. 
 Calcareous Tufa. 
 
 Limestone 
 Soft. 
 Chalk. 
 
 Marl. 
 
 This is a table of rocks which do not occur very extensively 
 as boulders. Leaving out the "crystalline" "silicious rocks," 
 those which remain are not sufficiently hard to endure the usage 
 to which boulders have been subjected. Yet, leaving boulders 
 out of the account, the most abundant bed rocks throughout the 
 country are those designated above as "indurated" and "semi- 
 indurated." That is, outside of New England and a region 
 
78 GEOLOGICAL EXCUKSIOKS. 
 
 along the eastern flanks of the Alleghanies, the common bed 
 rocks of the country are of the indurated and semi-indurated 
 sorts, until we are north of Albany, Lake Huron and Minneapo- 
 lis. But the boulder-forming rocks furnish us with a much 
 greater number of varieties than these fragmental rocks. It is 
 in the fragmental rocks that we find fossil shells and corals. 
 These things are of intense interest for study, but we cannot take 
 them up until we reach a more advanced course. 
 
 Very often we find silicious matter mixed with aluminous and 
 calcareous rocks; also aluminous matter mixed with silicious and 
 calcareous rocks; also calcareous matter mixed with silicious and 
 aluminous rocks. Then we have to prefix the qualifying word 
 "silicious," "aluminous" or "calcareous" to the proper name of 
 the rock. So we may have silicious slates or limestones; alum- 
 inous sandstones or limestones, and calcareous sandstones or 
 shales. Further, if iron oxide imparts its reddish or yellowish 
 color to any of these rocks they are also ferruginous. In the 
 same way any of these rocks may be bituminous, carbonaceous, 
 micaceous or petroliferous. 
 
 EXCURSION XV. To the Specimen Drawers. 
 Exercises in Identifications. 
 
 "We may arrange an analytical table to enable us to 
 determine the commoner rocks. This will also present the 
 subject in another light. There is nothing in the table 
 which has not been included in the previous lessons. It is 
 only requisite that the pupil should be able to identify the 
 principal minerals, and understand the terms which have 
 been already explained. 
 
 Now, let us take any specimen at random, and see if we 
 can ascertain its name by the use of this table. Then we 
 will try other specimens. 
 
TO THE SPECIMEN DKAWEES. 79 
 
 ANALYTICAL TABLE FOR THE DETERMINATION OF THE 
 COMMONEST ROCKS. 
 
 A. Crystalline, some of the constituent minerals having shining, lustrous 
 
 surfaces, or fine, compact, and hard. 
 I. Phanerocrystalline, consisting of minerals distinguishable with naked 
 
 eye or pocket lens. 
 1. No effervescence with acids. 
 
 (1) Quartz present and no other mineral, Quartzite. 
 
 (2) Feldspar alone with quartz. 
 
 (a) Structure massive, Granulite. 
 
 (b) Structure schistose, Granulitic Schist. 
 
 (3) Mica present in thin, glistening, elastic scales. 
 
 (a) Quartz present, and no third mineral. 
 
 (aa) Structure thick-bedded, Micaceous Quartzite. 
 
 (bb) Structure thin-bedded, Mica Schist. 
 
 (b) Quartz and feldspar present with the mica. 
 
 (aa) Structure massive, Granite. 
 
 (bb) Structure thick-bedded Gneiss. 
 
 (cc) Structure thin-bedded, little feldspar, Mica Schist. 
 
 (4) Hydromica present in thin, lustreless, inelastic scales. 
 
 (a) Quartz present, and no third mineral. 
 
 (aa) Structure thick-bedded, Hydromica Quartzite. 
 
 (bb) Structure thin-bedded, Hydromica Schist. 
 
 (b) Quartz and feldspar present with the hydromica. 
 
 (aa) Structure massive, Hydromica Granite. 
 
 (bb) Structure thick-bedded, Hydromica Gneiss. 
 
 (cc) Structure thin-bedded, Hydromica Schist. 
 
 (5) Hornblende present. 
 
 (a) No mineral but hornblende, Hornblende Mock. 
 
 (b) Quartz present and no third mineral. 
 
 (aa) Structure thick-bedded, Horriblendic Quartzite. 
 
 (bb) Structure thin-bedded, Hornblende Schist. 
 
 (c) Quartz and feldspar, with hornblende. 
 
 (aa) Structure massive, Syenite. 
 
 (bb) Structure thick-bedded, Syenitic Gneiss. 
 
 (cc) Structure thin-bedded, little feldspar, 
 
 Hornblende Schist. 
 
 (d) Orthoclase only with the hornblende, structure massive, 
 
 Hyposyenite. 
 
80 GEOLOGICAL EXCUKSIONS. 
 
 (e) Plagioclase only with the hornblende. 
 
 (aa) Structure massive, Diorite. 
 
 (bb) Structure schistose, Diorite Schist. 
 
 (6) Augite present. 
 
 (a) No mineral but augite, Augite Rock. 
 
 (b) Quartz only, or chiefly, with augite, Augite Schist. 
 
 (c) Plagioclase only with augite. 
 
 (aa) Structure massive, Diabase. 
 
 (bb) Structure schistose, Diabase Schist. 
 
 (d) Orthoclase only with augite, Augite Hyposyenite. 
 
 (7) Talc present. 
 
 (a) No mineral but talc, | ^^' 
 
 (b) Talc alone with quartz. 
 
 (aa) Structure thick-bedded, Talcose Quartzite. 
 
 (bb) Structure thin-bedded, Talcose Schist. 
 
 (c) Talc and orthoclase with quartz. 
 
 (aa) Structure massive, Protogine. 
 
 (bb) Structure thick-bedded, Protogine Gneiss. 
 
 (cc) Structure thin-bedded, Protogine Schist. 
 
 2. Effervescence with acids, Marble. 
 
 II. Cryptocrystalline, constituent minerals undistinguishable. 
 (Determinations uncertain by simple inspection.) 
 
 1. Hardness equal to quartz, lustre glassy, Vitreous Quartzite. 
 
 2. Hardness a little less than quartz, lustre dull. 
 
 (1) Color black [sometimes Diorite or Diabase, but 
 
 frequently], Aphanite. 
 
 (2) Color very dark, structure generally banded, Silicious Argillite. 
 
 (3) Color reddish, whitish, greenish, smoky, lustre horny, Felsite. 
 B. Uncrystalline (fragmental), distinctly stratified. 
 
 I. Effervescence with acids, at least when heated. 
 
 1. Rock hard, often containing fossils, Limestone. 
 
 2. Rock easily cut with a knife, Chalk. 
 
 3. Rock without much coherence, Marl. 
 
 II. No effervescence with acids, or only very little. 
 
 1. No quartzose grains. 
 
 (1) Rock can be cut with a knife, Slate. 
 
 (2) Rock very easily cut, Shale. 
 
 2. Quartzose grains present. 
 
 (1) Grains cohering together, Sandstone. 
 
 (2) Materials uncemented, Sand. 
 
BY THE WATEKSIDE. 81 
 
 Do not think all rocks can be determined by this little 
 table. If you try a specimen which can not be so deter- 
 mined, lay it aside until you have opportunity to take a 
 more thorough course. 
 
 If you can use this table, and determine the more com- 
 mon rocks, you certainly have made an excellent start. 
 You already know something about geology. Should you 
 go no farther, you will have much satisfaction in under- 
 standing something about the most common rocks all over 
 the northern United States. 
 
 EXCUKSION "XN\.By the Waterside. 
 
 Sediments. 
 
 How often we have noticed a sediment in some standing 
 liquid. This little observation is the key to the geological 
 work which has made nearly all the rocks known to us. 
 Let us go out and study some sediments recently made by 
 geological action. We hardly step into the street without 
 noticing some deposits left by the last shower. We walk 
 along a country road and soon find a spot where the torrent 
 of water has reached the level ground and laid down its 
 load of sand and stones brought from the hill slope. See 
 the method of assortment. First, the coarse stones were 
 dropped as soon as the force of the water was slackened too 
 much to bear them along. Then, after a little further 
 slackening, smaller stones were dropped. Just beyond 
 these we find small pebbles and sand ; and the fine mud has 
 accumulated in the hollow where the water stood. Why are 
 there no pebbles at the bottom of the roadside puddle ? 
 
82 GEOLOGICAL EXCURSIONS. 
 
 And why is there no mud at the foot of the hill where the 
 cobble stones lie? 
 
 If we go down to the brook side in the meadow, we shall 
 find a low, flat place which the stream overflows occasion- 
 ally. A little examination will show that the soil here is 
 simply a brook or river sediment. It is alluvium, formed 
 from the deposit of the stream. There is drift material in 
 it, composed of stems and chips and bits of lumber, besides 
 leaves and grasses. There are also some whitened shells 
 which once lived in the stream. 
 
 Let us go down by the pond. Do you notice the steep 
 banks around one or two sides and the low, marshy margin 
 on another side ? See how the rushes and the cat tails rise 
 from the shallow, stagnant water near the shore. See the 
 sedges and grasses growing in the bog nearer the shore. 
 These plants are killed by every winter's frosts, and the old 
 stems fall down and go to decay almost exactly in the places 
 where they grew. They decompose into a blackish sort of 
 soil called peat. How thick a deposit of peat do you sup- 
 pose might be accumulated in a man's lifetime ? Would it 
 not pretty nearly fill the pond, especially on the side where 
 the vegetation grows so rankly ? Now this query leads us 
 to look a little farther back from the shore. Here is quite a 
 broad, marshy belt (see Figure 20), and beyond is some 
 meadow land. All this marsh and meadow land is as level 
 as the pond or lake. Still beyond, the dry upland begins. 
 Now it looks exactly as if the lakelet had once extended to 
 the upland, and had become filled with peat as far as the 
 level surface extends. Let us go and dig in the meadow 
 
BY THE WATERSIDE. 
 
 83 
 
 FIG. 20. THE LAKELET SLOWLY FILLING. 
 FORMATION OF MARL AND PEAT. 
 
 and see if it is peat. Certainly it is. It is true, then, that 
 the lakelet is filling, and is made shorter every year on the 
 side where the vegetation grows so luxuriantly. But does 
 the filling and shortening take place only on one side ? Let 
 us think a minute. Which way do the winds blow mostly? 
 Why, they blow from the side opposite the marsh. Then 
 all the leaves and twigs and grasses which get into the 
 water are blown over toward the marshy side. Certainly ; 
 and when the lakelet first existed these drifted materials 
 were lodged at the foot of the slope on that side, and went 
 to decay and formed a sort of peaty material in the bottom 
 of the water. After some years the deposit became con- 
 siderably extended. Meantime the plants which like to 
 grow in stagnant, shallow water made their appearance 
 there ; and nothing else has been necessary but to let these 
 operations have time enough, and the whole breadth of the 
 peaty marsh would grow into existence just as we see it. 
 That is the explanation of the marsh and meadow on one 
 side of the lakelet. Of course, much dirt has washed down 
 the hill slopes on the other sides and has gone into the 
 
84 GEOLOGICAL EXCURSIONS. 
 
 lakelet. The coarser material has been left near the shore, 
 and the finer has been floated into the deeper water. Some 
 has floated over to the marsh side, and the fine aluminous 
 mud has settled down and mingled with the growing peat. 
 
 Now, you ask if this pond or lakelet will not become 
 completely filled by and by. Of course it will. There are 
 plenty of lakelets which have been filled already. How do 
 you suppose the place would look if the pond had been quite 
 filled already ? Why, that level meadow would extend all 
 over it. There would be no more lakelet. There would be 
 a level marsh. Well, don't you know any level marsh 
 exactly such as you think this pond will become by and by ? 
 Of course, you know a good many of them. One is all 
 overgrown with flags and rushes, and one is full of tamarac 
 trees, and another has alder bushes growing all over it. If 
 you ask your father or your uncle, or some other man who 
 has lived here a good many years, he will tell you he 
 remembers when the water stood in the place where that 
 bog is. He may remember when the dam was built, and the 
 mill pond formed when the water first overflowed some of 
 the land. He will tell you that the water at first was clear, 
 but now you can see that the mill pond is half grown up 
 with rushes, and is filling every year. 
 
 Now you are asking about that white substance which 
 was dug from under the peat in a certain place. I will tell 
 you about it. Come with me to the water. In most ponds 
 and lakelets you may find some little shells some uni- 
 valves like snails, and some bivalves like clams. They form 
 their shells from the calcium carbonate in the water ; and 
 
BY THE WATERSIDE. 85 
 
 the calcium carbonate comes from the limestone in the soil 
 or rocks through which the water flows which tills the lake- 
 let. This is not abundant in New England, but it is through- 
 out the West. When the animal in the shell dies, the shell 
 rests on the bottom and slowly decomposes. In time it 
 forms over the bottom a bed of white, soft, calcareous mat- 
 ter called marl. So, as the peat bed extends, it forms above 
 the bed of marl ; and after the water is quite displaced 
 by these accumulations, we find a bed of peat underlaid by 
 a bed of marl. These marl beds are most abundant 
 in the western states ; but peat beds form wherever there 
 are lakelets and vegetation. The bed of peat maybe called 
 a stratum of peat; and the bed of marl a stratum of marl. 
 So you see what is the origin of these two strata. 
 
 In spring, after the heavy rains, the streams are full of 
 sediment. Even a summer shower will muddy all the small 
 streams. Where do these sediments go? The stream 
 empties into another stream or into a lake, or into the ocean. 
 But wherever the stream empties, the water gets finally into 
 the sea, and some of the sediment is compelled to go with 
 it. When the sediments reach the sea they may be tossed 
 about for a time by the waves, but they must finally settle 
 to the bottom. The water of the Mississippi River is full 
 of mud at all times of the year. Immense quantities are 
 brought down by the Missouri River. When you travel on 
 a Mississippi River steamboat, they will fill your drinking 
 glass with water from the muddy river. One accustomed to 
 the clear water of the eastern and northern states can hardly 
 endure such drinking water. Let a glass of it stand for 
 
86 GEOLOGICAL EXCURSIONS. 
 
 thirty minutes and a frightful amount of mud settles to the 
 bottom. Well, where does all this mud in the Mississippi 
 go ? Into the gulf of Mexico necessarily except what set- 
 tles upon the land at times of overflow. The sediment 
 carried into the gulf is literally filling it up. Some of the 
 finest floats a long time and settles to the bottom hundreds 
 of miles from the mouth of the river. A larger amount is 
 deposited at the mouth, where the current is neutralized by 
 the gulf water. This deposit forms what is called the bar 
 of the Mississippi, which so much obstructs navigation. It 
 increases at such a rate that it advances 336 feet every year, 
 The whole amount of sediment carried down by the Missis- 
 sippi, if dried, would make every year a pile a mile square 
 and 268 feet high. Much of the Mississippi sediment is 
 spread over the region of the overflow, and is many feet 
 deep. This deposit forms the delta, of the Mississippi. 
 
 All streams emptying into the sea carry more or less 
 sediment. So the sea bottom is becoming covered with lay- 
 ers of mud ; and with the mud must be mingled the remains 
 of all the animals which perish in the sea. 
 
 EXERCISES. 
 
 Mention some marsh with which you are acquainted. Is it 
 quite level ? What once existed in its place ? Why is the lake- 
 let not there still ? What is the upper stratum of the marsh 
 composed of ? If you should find much earth or sand mixed with 
 the peat, how would you explain that ? If you should find white 
 shells in the peat, how could that be explained ? Is the peat 
 chiefly organic or inorganic? Is peat of any use to the 
 farmer ? What is the use of marl ? What is the composi- 
 tion of marl ? Is the bar of a river composed chiefly of 
 
IN THE GORGE. 87 
 
 fine or of coarse matter? How does the sediment far from a 
 river's mouth compare with that near the mouth ? Can any 
 sediment get into the sea except that brought down by rivers ? 
 Why is the border of the lake or the sea lined with pebbles and 
 cobble stones ? When the waves wear away a gravel bank, what 
 becomes of the sand and clay ? If you could dig through the 
 layers of sediment in the bottom of the pond, or in the bottom 
 of the Gulf of Mexico, would you find all exactly alike ? Why 
 are some coarser than others ? Why are they of different colors? 
 Has the Hudson River any delta? What might prevent a river 
 from having a delta? Mention some rivers having extensive 
 deltas. Why are some rivers clear and others turbid ? 
 
 EXCURSION XVIL In the Gorge. 
 Decay and Erosion of Rocks. 
 
 You saw how large an amount of sediment accumulates 
 in ponds and lakelets ; how much is carried down by rivers, 
 and how the sea is actually filling up through the processes 
 of sedimentation. Now, all this sediment comes from some- 
 where. Let us see if we can find the sources of it. 
 
 The muddy stream by the roadside well, you are ready 
 to say at once that the mud comes from the street. Yes, 
 that accumulation of stones and sand which we examined at 
 the foot of, the slope is nothing but stuff washed down from 
 the roads. Just above is a deep, rugged gully washed out 
 by the rain. Look at it. Where has the stuff gone which 
 came out of that hole ? Is it all at the foot of the hill ? Is 
 there no more deposited there than was washed out here ? 
 The wearing away of the ground we call erosion. 
 
 Now we have reached the ravine. This is on a hillside. 
 
88 
 
 GEOLOGICAL EXCURSIONS. 
 
 The hill may not be very steep, but it causes water to flow 
 down. There is a little brook here which is always running. 
 Look in the bed of the brook ; why is it so stony ? Has 
 there been no soil there, nor sand ? Here in the bank are 
 sand and loam, and the only reason why such fine materials 
 are not in the bed of the stream is that the water has washed 
 them away. The sand and loam have gone down to the 
 flat, and very likely we might find them there spread out just 
 like the stuff brought down by the roadside torrent, which 
 only worked one afternoon. But sometimes this stream is 
 
 vastly larger than at present; 
 then it moves the larger stones ; 
 and as these are taken away, 
 others come from higher up. 
 And when the water is high it 
 washes these banks, and re- 
 moves sand and stones, and in 
 this way makes the ravine wider. 
 Think of that ; the stream wid- 
 ens this ravine every year. We 
 can think of a time when the 
 ravine was much narrower, and 
 also shallower. We can think 
 back to the time when the ra- 
 vine first began to be formed. 
 
 Ita. SI-VIEW IN THK GOEOE At V*t it is broad and deep; 
 AT W ATKINS' GLEN, N. Y. but it appears that it has all 
 (-EAINBOW FALLS ), Inus- hag been d out fe ^ wat(Jr 
 
 TEATING EROSION BY WATER. 
 
 (PHOTOGRAPH.) which has flowed down the 
 
THE GORGE. 
 
 89 
 
 hillside. If this hill had not so many stones and rocks 
 in it, the rapine would have become much deeper than it is. 
 In Alabama, where stones are fewer, or at least smaller, you 
 can see deeper ravines excavated during one man's lifetime. 
 Unless, however, the rocks are of the crystalline and 
 quartzose sorts commonly found in boulders, it seems to 
 make little difference whether the sides of the ravine are 
 rocky or mere incoherent drift. We could visit hundreds of 
 localities where some little stream has cut deep through solid 
 strata. At Watkins' Glen, in southern New York, is a very 
 wild and interesting spot. Some of you will visit that spot 
 Fig. 21 is a picture which all can examine. Is it not strange 
 that mere water could wear away the solid rocks on so vast 
 
 FIG. 22. THE "DALLES" OF THE WISCONSIN, 
 SHOWING RIVER EROSION. (PHOTOGRAPH.) 
 
90 
 
 GEOLOGICAL EXCURSIONS. 
 
 a scale ? It is a fact, nevertheless, and all the material has 
 gone somewhere. Let us look on the map and ascertain 
 where. Here is Watkins in Schuyler county, at the head 
 of Seneca Lake, and here is the tiny stream which has worn 
 the gorge. The stuff has certainly gone into Seneca Lake, 
 and lies spread over the bottom. 
 
 In Figure 22, is a similar example from quite another 
 portion of the country. The Wisconsin River has cut its 
 gorge through the ancient strata, forming a scene of beauty 
 as well as of geological interest. A grand example of the 
 
 work of a mightier stream may 
 be seen along the banks of the 
 Upper Mississippi Biver in 
 Wisconsin and Minnesota. 
 Here a wide valley has been 
 excavated through vast forma- 
 tions of sandstone and lime- 
 stone, and the walls of rock rise 
 on each side one or two hun- 
 dred feet: Between them flows 
 the broad Mississippi. (See 
 Figure 23. Also Figure 51.) In 
 the Far West is a river known 
 as the Colorado which has 
 worn a gorge in some places 
 more than a mile in depth. 
 
 F. 23.-CL, o. THE UPP EK But the rocks everywhere 
 
 MISSISSIPPI NEAR TREMPEALEAU, ^e wearing out. The very 
 Wis., ILLUSTRATING RIVER ERO- , 
 
 SIGN. (CHAMBERLIN.) rain and dew tend to dissolve 
 
IN THE GORGE. 
 
 91 
 
 the cement which holds their parts together ; and freezing 
 and thawing are powerful agents in disintegrating them. 
 You will recall what was said of kaolin as simply the result 
 of decomposition of feldspar. In the southern states, and in 
 all warm countries, you may sometimes trace the encroach- 
 ment of decay from the exposed surface of a bed rock down- 
 ward ten or twenty feet. All over the land the rocks are 
 decaying, and the rains wash the powder and the grains into 
 the streams ; and this is the source of much of the sediment 
 which floats in the rivers and spreads over the sea bottom. 
 It is calculated that the surface of 
 the land is lowered a foot in six 
 thousand years. Of course some 
 rocks decay faster than others. 
 Sometimes rocks are undermined 
 by the more rapid decay of the 
 rocks beneath them. Here is an 
 interesting case in Wisconsin in 
 the bluff of a creek. In many 
 cases cubic miles of rock have 
 been eroded and removed from 
 the midst of the land. All the central part of Tennessee 
 is a vast basin sunk through the solid limestone. All 
 around the border the remaining limestone rises in massive 
 walls a hundred feet high and more. In east Tennessee is 
 another valley formed by extensive erosion. These are shown 
 in the cut, Figure 25. See, also, how the nearly vertical strata 
 of the Unaka range have been worn down to mere stumps. 
 Where have gone the continuations of those upturned strata ? 
 
 FIG. 24. 
 
 MAGNESIAN LIMESTONE UNDER- 
 MINED BY THE DISINTEGRA- 
 TION OF A SANDSTONE BE- 
 NEATH. (CHAMBERLIN.) 
 
92 
 
 GEOLOGICAL EXCURSIONS. 
 
 See the wonderful proof of vast 
 erosions along the Appalachians. 
 (Figure 26. ) Here the actual sur- 
 face is shown along ABC. Can 
 you believe that the slight ele- 
 vation at A represents truly one 
 of the ranges of the Allegheny 
 Mountains ? And that B repre- 
 sents the range known as Bald 
 Eagle Mountain ? How the 
 vast series of strata has been 
 folded here. Notice the moun- 
 tain mass represented by E, 
 which once rose thirty-five thou- 
 sand feet above the present sur- 
 face, and all has been carried 
 away by erosion. This section 
 is in Centre county, and shows 
 but a fraction of a full section 
 across the Appalachian chain. 
 But all the mountain elevations 
 have been similarly worn down. 
 In other cases singular col- 
 umns of the eroded rock have 
 escaped erosion. They have 
 been protected by a fragment of 
 harder rock, which rests on them 
 like a cap. Lr'Monument Park," 
 Colorado, are many remarkable 
 examples. (See Figure 27.) 
 
IN THE GORGE. 
 **> 
 
 93 
 
 FIG. 26. ILLUSTRATING ENORMOUS EROSION IN THE APPALACHIAN REGION. 
 A, Allegheny Mountain at Snow Shoe ; B, Bald Eagle Mountain ; A, B, 
 C, present surface all above swept away ; D, probably a subterranean 
 mountain of Eozoic rocks; II to III, Cambrian; IV to VI, Silurian; VII 
 to IX, Devonian; X to XII, Lower Carboniferous; XIII, Coal Measures 
 (after Lesley). Compare for explanations, Excursion XVIII. 
 
 So we learn there has been a vast destruction of the rocks 
 during the course of many ages. They have been gradually 
 reduced to gravel and mud, and carried off by the streams, 
 to be laid down on the plains or spread as sediment over the 
 bottom of the sea. Other interesting cases of erosion are 
 shown in Figures 52, 53, 60, 61 and 73. 
 
 EXERCISES. 
 
 Can a quartzite be worn out by any means? If quartz peb- 
 bles are fragments of rocks, why are they not sharp angled? 
 Which wears fastest, a quartzite or a limestone? If water flows 
 through a fissure in a limestone, by what two means will the 
 fissure be enlarged ? If the fissure is underground, what will it 
 become ? Are many caverns produced in this way? Which make 
 the steepest banks to a stream, hard rocks or soft ones ? Why 
 are not the walls of all gorges nearly perpendicular? Does 
 weathering affect the angles of cliffs and rock fragments ? What 
 sort of climate would weather the rocks most rapidly? Would 
 vertical cliffs be most likely to stand in a dry climate, or a change- 
 able one ? In a climate with freezing and thawing, or one with 
 
94 GEOLOGICAL EXCURSIONS. 
 
 no freezing? What is the difference between erosion and 
 weathering ? Which kind of work is done by running streams ? 
 Which is done by waves? Which is done by frost? Is there 
 any important difference between the wearing done by rains and 
 that done by streams? Is it running water which has made the 
 valleys in a country completely drift covered ? Why have the 
 
 FIG. 27. COLUMNS IN MONUMENT PARK, COLORADO. (HAYDEN.) 
 
 valleys such sloping banks? Has floating ice any influence on 
 the work of running waters? Explain a possible origin of a 
 natural bridge. Explain a possible origin of the Mammoth Cave 
 of Kentucky. What effect has erosion on the farmer's soils? 
 Does any of his soil go where no one can find it again? What 
 effect has erosion on the height of the hills? 
 
AT THE ROCKY LEDGE. 95 
 
 EXCURSION XVIIL At the Rocky Ledge. 
 Strata and Systems of Strata. 
 
 You have seen the brooks and rivers at work wearing 
 down the land. You have seen the waves corroding 
 the beach. You. have thought on the slow disintegration 
 of all the surface rocks by rains and frosts, and have seen 
 the waters carrying away the sediments to the sea. In 
 thought you have followed those sediments in their distri- 
 bution over the ocean's bottom. You have seen them 
 lying and accumulating there, while dead shells and bits of 
 coral and bones of fishes have been mingled with the grow- 
 ing deposit. What appearance must these sediments present 
 in case a few acres of sea bottom could be taken out bodily 
 and inspected ? The sediments would consist of layers 
 parallel with each other, one above another. These layers 
 would be distinguished by different colors and by different 
 degrees of fineness. Imbedded in the substance of the 
 layers would bo the relics of the animals which have lived 
 in the sea. Is this a correct statement of what you would 
 see ? Think about it. The depth of the accumulated sedi- 
 ments would correspond to the time spent in their accumu- 
 lation. You might look at them and reflect: "These layers 
 of mud and sand were once far inland. They were once 
 part of the soil of cornfields and gardens. Crops grew on 
 them. The gully in the road was made by the removal of 
 them. They came down the rivers. Some started on the 
 slopes of distant mountains. The Missouri brought some 
 from the gorges and summits of the Rocky Mountains. 
 
96 GEOLOGICAL EXCURSIONS. 
 
 Some came out of the deep, dim canyons of the Colorado. 
 Some came from the storm-torn bluffs at Long Branch or 
 Coney Island or Gay Head. Some was yielded by the slowly 
 dissolving promontories of Nahant and Marblehead." 
 
 That is what you might think. Now suppose the layers 
 of sediments pressed by thousands of tons of weight. They 
 would be pressed into a solid state, like the paper pulp 
 which is manufactured into car-wheels. They would be a 
 rock. The rock would be composed of strata. The thin 
 layers would be called laminae. The shells and corals 
 pressed in the rock would be fossils. This is almost 
 exactly what we have in the majority of the rocks under- 
 lying the country. All our limestones, sandstones and 
 shales were once just such sea-sediments. The limestones, 
 however, contain a very large proportion of matters con- 
 tributed by the decay of shell-bearing animals. 
 
 In most of New England, however, and along the north- 
 ern border of our country, the ledges of rocks which we 
 find are hard and crystalline. From these have come most 
 of the boulders which are scattered over the surface of all 
 the northern states. In places where these crystalline rocks 
 come in contact with the uncrystalline, we find the uncrys- 
 talline overlying the others. (See Figure 28.) But there 
 are almost always some traces of stratification even in the 
 
 
 b a be 
 
 FIG. 28. CRYSTALLINE AND UNCRYSTALLINE ROCKS, a, Granite; b, Gneiss; 
 
 c, Sandstone. 
 
AT THE KOCKY LEDGE. 97 
 
 crystalline rocks. You remember the gneisses and schists. 
 Well, this is the way they lie over the granite and beneath 
 the sandstones. They have been rendered less distinctly 
 stratified by some action called metamorphism. What are 
 the particulars of that action cannot now be explained; but 
 you may understand that great pressure, great heat and 
 chemical operations have had much to do with metamor- 
 phism. If, then, even the hard crystalline rocks were also 
 once sea sediments, they must have been laid down before 
 the sediments which formed the uncrystalline rocks. That 
 is, older rocks are below, and newer rocks are above. 
 
 In the crystalline rocks it is a very extraordinary thing 
 to find any fossils. In the uncrystalline rocks it is a com- 
 mon thing. So this is another particular in which they 
 differ. 
 
 But now let me tell you something very important about 
 the uncrystalline rocks. We do not find the same kinds of 
 fossils in all of them. Those at the bottom contain many 
 relics of very strange creatures, and they are all marine. 
 There are none which lived on the land. There are 
 none which had back-bones. That is, they were all in- 
 vertebrate. In strata which overlie these we find the 
 teeth and bones of fishes; but still the fossils are all marine. 
 Still higher, we find strata with the remains of creatures 
 which dwelt on the land; but they were sluggish, salaman- 
 der-like creatures. When we come to rocks overlying 
 these, we find in them the bones of an astonishing number 
 of reptiles. Still higher we find bones of quadrupeds. This 
 is all very curious; but it shows that the rocks may be 
 
98 GEOLOGICAL EXCURSIONS. 
 
 classified according to the fossil remains which they con- 
 tain. Let us repeat the succession: 1. Rocks almost with- 
 out fossils. These are at the bottom. 2. Rocks containing 
 only marine invertebrates. 3. Rocks containing marine ver- 
 tebrates. 4. Rocks containing the lowest terrestrial verte- 
 brates. 5. Rocks containing the remains of reptiles and 
 birds. 6. Rocks containing the remains of mammals. 
 
 Now, the reason why the rocks containing marine inver- 
 tebrates do not contain also marine vertebrates, or land 
 animals of any kind, is because these other animals were 
 not in existence when the lower rocks were accumulating as 
 sediments. And so we learn that the different ranks of 
 animals were called into existence at different times. There 
 has been a succession and a progress in the history of life 
 on the earth. 
 
 These are some of the most important facts in geology. 
 Each of these series of rocks is called a system / and each 
 system has received a name. It is extremely important 
 to commit these names to memory. Here in this diagram 
 (Fig. 29) they are all arranged in order, with the char- 
 acteristic fossils indicated. All this must be well studied. 
 
 Take notice. You are learning now only the order of 
 superposition of strata, and the systems in which they are 
 classified. Do not think all these rocks can be found piled 
 up in every place. You shall learn next time we meet how 
 the various strata are distributed over the country. 
 
GREAT SYSTEMS, 
 
 OR 
 ERAS. 
 
 C.ENOZOIC. 
 
 MESOZOIC. 
 
 SYSTEMS, 
 
 OR 
 AGES. 
 
 QUATERNAKY. 
 
 TERTIARY. 
 
 CRETACEOUS. 
 
 JURASSIC. 
 TRIASSIC. 
 
 UPPER CAR- 
 BONIFEROUS. 
 
 LOWER CAR- 
 BONIFEROUS. 
 
 PALAEOZOIC. DEVONIAN. 
 
 Eozoic. 
 
 UPPER SILU- 
 RIAN 
 
 (OR SILURIAN). 
 
 LOWER SILU- 
 RIAN 
 (OR CAMBRIAN). 
 
 HURONIAN. 
 
 LAURENTIAN. 
 
 Star Peak Group. 
 Koipato Group. 
 Permian. 
 
 HIGHEST 
 FOSSILS. 
 
 Carbonif. Limestone. 
 
 Catskill Group. 
 Chemung Group. 
 Hamilton Group. 
 Comijerous Group. 
 Oriskany Sandstone. 
 Helderberg Group. 
 Salina Group. 
 Niagara Group. 
 
 Trenton Group. 
 
 Canadian Group. 
 Primordial Group. 
 
 W M 
 
 FIG. 29. THE GEOLOGICAL COLUMN. 
 
100 GEOLOGICAL EXCURSIONS. 
 
 EXERCISES. 
 
 What two systems are included in the Eozoic Great System ? 
 What are included in the Palaeozoic Great System ? What in the 
 Mesozoic ? What in the Caenozoic ? Which are the oldest strata, 
 the Devonian or the Cretaceous ? Do we find any fossil men in 
 the Silurian ? Were there any snakes in the Eozoic ? Are there 
 any snakes' remains in the Caenozoic ? Are whales marine verte- 
 brates ? Are there any whales' remains in the Devonian ? What 
 do you understand by the Devonian Age ? What is meant by 
 the Cretaceous Age ? Which was the longest, an Era or an 
 Age ? What are the Ages of the Palaeozoic Era ? Did the 
 continent of America exist during the Palaeozoic Era? Which 
 are the hardest, Palaeozoic or Caenozoic rocks ? Which were 
 hardest when first laid down as sea-sediments ? What do we 
 call that process by which the Eozoic rocks became crystalline ? 
 Mention several kinds of Eozoic rocks. Are most of our boul- 
 ders derived from Eozoic or from newer rocks ? Why do the 
 Eozoic rocks appear less distinctly stratified than the Palaeozoic ? 
 Suppose we find a shale in contact with mica schist, which do 
 you think the oldest rock ? Which would lie above the other ? 
 Could you expect to find a chalk under a granite ? Why not ? 
 Would it be possible for mud in the bar of the Mississippi ever 
 to become solid rock ? What kind of a rock do you imagine it 
 would make ? Could it possibly become chalk ? Could it possi- 
 bly become granite ? Could that mud be changed to limestone 
 by any means ? Was the Mississippi mud ever solid rock ? Were 
 the solid rocks ever mud? What is the use of making rocks and 
 then wearing them into mud to make rocks of again ? 
 
TO THE DIAGRAMS. 
 
 V101 
 
 EXCURSION XIX. To the Diagrams. J 
 How the Strata Enwrap the Earth. 
 
 FIG. 30. THE SYSTEMS OF STRATA NOT LIKE THIS. 
 
 If yon cut an onion through the middle in such a direc- 
 tion that the top is on one half and the root on the other, 
 the layers of the onion will be seen surrounding each other 
 somewhat like the bands A, B, C, D, in this figure. But 
 this does not represent the way the different systems of 
 strata enwrap the earth. You have learned that all the 
 rocks have been sea-sediments at some time. You know 
 from this that wherever the rocks are, there has been the 
 sea. As there is some kind of rocks that is, some system 
 of rocks at every place, we may be certain that the sea 
 has covered every place at some time. But it is not true 
 
102 
 
 GEOLOGICAL EXCURSIONS. 
 
 that all the Systems of rocks are present under every place. 
 If they were we should have everywhere the Csenozoic rocks 
 at the surface, and under these would be the Mesozoic, and 
 then would follow downward the Palaeozoic and the Eozoic. 
 The fact is that any system of rocks may be at the surface. 
 Sometimes even the Eozoic rocks are at the surface; and, in 
 fact, we sometimes find them thousands of feet above the 
 
 FIG. 31. THE SYSTEMS OF STRATA MORE LIKE THIS. 
 
 level of the sea. This state of things it is very important 
 to understand. 
 
 It appears that the earth has, at various times in the 
 past, been a little distorted in shape, as you may see in 
 
TO THE DIAGRAMS. 103 
 
 Figure 31; though you must not think the earth has been 
 squeezed into such a shape. It has not been distorted one- 
 hundredth so much as this. Such a figure is given to make 
 it easier for you to see the effects of distortion. In this 
 figure we may suppose the bands A, B, C, d to represent 
 the different systems of rocks as they would appear if the 
 earth were cut through, through the middle. All these 
 bands are near the surface. We cannot show anything in 
 the interior of the earth, because we do not know what is 
 there. We can guess something about it; but we must 
 confine ourselves now to that part of the earth which is very 
 near the surface. That part which we know to be composed 
 of solid, rocky material is called the earth's Crust. In this 
 we have the various systems marked A, B, C, d, the names 
 of which you learned in the last lesson. The figure shows a 
 section through the crust, and shows how one system of 
 rocks overlies another. Where any stratum goes down 
 under another, we say it dips under it. When it comes out 
 from under another, we say it outcrops. 
 
 You will notice that the only system which completely 
 surrounds the earth is the Eozoic, A. In some places the 
 Eozoic comes quite to the surface; in others, as at #, #, #, #, 
 it is overlaid by all the other systems. In other places, as 
 at 5, , 5, it is overlaid only by the Palaeozoic. In still 
 other places, as at 0, c, 0, <?, it is overlaid by both Palaeozoic, 
 B, and Mesozoic, C. There are only a few places, like d, d', 
 d", where any Csenozoic can be seen except Drift or other 
 Post-Tertiary, which covers nearly all the earth's surface, 
 and is not represented in this diagram. In some places, 
 
104 GEOLOGICAL EXCURSIONS. 
 
 like ft', the Tertiary (Caenozoic) rests directly upon the Pa- 
 laeozoic, or even the Eozoic. 
 
 If you look closely at this diagram you notice an appear- 
 ance as if the Palaeozoic and Mesozoic strata had at some 
 former time extended much further than at present. For 
 instance, the dotted line c' c' shows what may have been at 
 some time the upper surface of the Mesozoic. If so, then 
 the dotted line below this shows what may have been at 
 the same time the upper surface of the Palaeozoic. In fact, 
 on all sides the arrangement of the strata looks as if they 
 had been once wrinkled up, and then the higher places 
 removed. That is something like the truth. But we must 
 not suppose the Palaeozoic and Mesozoic ever extended 
 quite over all the Eozoic which is now at the surface. We 
 cannot say precisely how far they ever covered the Eozoic. 
 We are certain, however, that they have been eroded to a 
 great extent. And we can understand that the sediment 
 produced by such erosions went partly into the sea, and was 
 made over in the patches of Tertiary which we see at <#, d, 
 d, d". 
 
 If the dotted circle s s s represents the level of the 
 ocean, you see that some parts of the crust rise above it and 
 form the continents ; and those parts which rise highest are 
 mountains. You see, also, that all the systems of strata lie 
 under the sea. 
 
 Now fix your attention on the d near the lower side of 
 the diagram, a little to the left of the middle. The rocks 
 there are Caenozoic; and you see a section or cut right 
 through them and the rocks under them. This section 
 
TO THE DIAGRAMS. 
 
 105 
 
 FIG. 32. MAP OF THE REGION 
 AROUND b d c, FIG. 31. 
 
 shows what is the surface extent of the Caenozoic area there 
 in one direction. Here it is, the 
 distance from m to n in this lit- 
 tle cut (Figure 32). We do not 
 know how broad this Caenozoic 
 area is in the other direction ; 
 but let us suppose it a little ob- 
 long; then its other diameter will 
 be o p, and m p n o will be a 
 map of the Csenozoic area of 
 which a section is shown in Fig- 
 ure 31 at d, near the lower side 
 of the figure. 
 
 But then, on one side of this 
 Csenozoic section is a section of 
 Mesozoic strata. Let us take the length of this Mesozoic 
 section and lay it off from m to r on the side of the map, 
 Figure 32. As the Mesozoic on the other side is covered by 
 the sea, we may represent the sea as bordering the Cseno- 
 zoic, and may lay down as much of it as we please, say 
 from n to , on the other side of the map; and may assume 
 that the sea-shore leaves the Caenozoic area at , s. Then 
 the distance from r across to n is the whole diameter of the 
 Mesozoic area, to the sea, including the portion covered 
 by the Caenozoic. The breadth in the other direction is not 
 known; but we may assume it as extending from t to u. 
 The whole size of the Mesozoic area not covered by the sea 
 will therefore be shown by v t r u w. Lastly, the Palaeo- 
 zoic, when laid down on a map, will give a belt surrounding 
 
106 
 
 GEOLOGICAL EXCUKSIONS. 
 
 the Mesozoic, as shown in x y z. So this is a geological 
 map showing three systems of strata; and Figure 33 shows 
 the appearance of a section across it. 
 
 Now, once more. Fix your atten- 
 tion on the point G in Figure 31. If 
 ^^L\-^/' -y/vj^^ we proceed to make a map of the 
 FIG. 33. SECTION ALONG region around this point, it will look 
 THE LINE y q, FIGURE some thing like Figure 34. Here you 
 see the Eozoic in the middle and the 
 newest strata around the bor- 
 der. Here, also, the ocean 
 bounds the area on one side. 
 Notice particularly the differ- 
 ence between this map and 
 the other. There the strata 
 dipped from all sides toward 
 the centre; here they dip from 
 the centre toward all the sides. 
 This is shown in the section, 
 Figure 35, where the Meso- 
 zoic c dips under the ocean 
 on one side ; the Palaeozoic b 
 dips under the Csenozoic, and 
 
 FIG. 
 
 34. MAP OF THE REGION 
 AROUND G, FIG. 31. 
 
 FIG. 35. SECTION ALONG THE LINE 
 d s, FIG. 34. 
 
 extends on one side under 
 the ocean ; and the Eozoic G- 
 dips in both directions under 
 the Palaeozoic. 
 
 Now, before we pass on to 
 the study of the geological 
 
LAVA, 
 
 TRACHYTE 
 
 BASALT 
 
 GRANITE 
 
 GRANITE 
 VEIN 
 
 FIG. 36. IDEAL SECTION OF THE EARTH'S CRUST. 
 
108 GEOLOGICAL EXCURSIONS. 
 
 map, look at this more extensive section through the rocks 
 of the earth's crust. This is not intended to show what 
 would be seen in any particular region, but would be seen 
 in a good many different regions. The various geological 
 phenomena which would be seen in many different regions 
 are here all brought together. So this is not a Teal but an 
 ideal section. Still everything shown is real somewhere. 
 This section will bear a great deal of study. You cannot 
 learn all about it now. I intend that you shall turn back to 
 it a great many times. But you may now ask as many 
 questions about it as you please. 
 
 EXERCISES. 
 
 In Figure 32, if we travel from the centre to the circumfer- 
 ence, do we pass from newer to older rocks, or from older to 
 newer ? If we stand near the circumference, which way do the 
 strata dip ? Do they dip toward and under newer strata, or away 
 from them ? If we bore a deep hole at the centre of Figure 32, 
 what systems of rocks will we pass through ? If we stand near 
 the circumference of Figure 34, which way do the rocks dip ? 
 Do they dip toward the older rocks, or away from them ? Must 
 strata always dip TOWAED NEWER rocks and AWAY FKOM OLDEK 
 rocks ? Suppose you bore a deep hole near the margin of Figure 
 34, what systems of strata would be passed through ? Suppose 
 you bore at the middle of Figure 34, what rocks will be passed 
 through ? Must a geological area necessarily be circular ? Sup- 
 pose the ocean should wear away two-thirds from the area mapped 
 in Figure 34, could you then make a geological map of the 
 region ? Try it. Point out places where the Palaeozoic outcrops 
 in Figure 31. Show where the Eozoic outcrops. What system 
 of rocks least completely enwraps the earth ? How could it be 
 that Casnozoic rocks should rest on Eozoic, with no Palaeozoic or 
 Mesozoic between them ? Make a geological map of the region 
 
TO THE GEOLOGICAL MAP. 109 
 
 extending from G toward the left, through c, d and s, to b, in 
 Figure 31. 
 
 EXCURSION" XX. To the Geological Map. 
 How to Understand a Geological Map. 
 
 I will now help you to understand a geological map of 
 the United States., Here, in Figure 37, is such a map ex- 
 tended as far west as the Black Hills. This is a real map 
 which attempts to represent things as they are. In the cor- 
 ner of the map is a "legend," which indicates what sys- 
 tems of strata are mapped. These are the same as the 
 "Systems" in the "Geological Column," Figure 29, with 
 three exceptions : The Laurentian and Huronian are here 
 thrown together as Eozoic ; the Triassic and Jurassic are 
 thrown together as Jura-Trias, and the Post Tertiary is dis- 
 regarded, since this is understood to be everywhere present, 
 covering all other formations. 
 
 First, fix your attention on the areas marked Eozoic. One 
 large area lies north of the Great Lakes and the St. Law- 
 rence Eiver; another lies along the eastern flanks of the 
 Appalachian chain of mountains extending from Penn- 
 sylvania through Maryland, Virginia, North and South 
 Carolina and Georgia into Alabama. These two Eozoic 
 masses pass under all the intervening strata and meet to- 
 gether. As the Eozoic strata are the oldest known, the 
 strata on both sides of an Eozoic area must be newer than 
 Eozoic, and must overlie the Eozoic. As the dips are 
 always away from the older rocks, it must be that the rocks 
 
TO THE GEOLOGICAL MAP. Ill 
 
 along the eastern side of the Appalachian Eozoic dip toward 
 the southeast, and those along the western side toward the 
 northwest. And so the rocks along the border of the 
 Canadian Eozoic must dip directly away from it. That is, 
 along the valley of the St. Lawrence River, the rocks next 
 the Eozoic must dip southeast ; in the region north of Lakes 
 Ontario and Huron, the dip must be south ; in eastern Wis- 
 consin, the dip is southeast, and in western Wisconsin, it is 
 southwest. 
 
 Southeast from the Appalachian Eozoic we have very 
 little except Tertiary strata. These then overlie the border 
 of the Eozoic, and dip southeastward, extending to the 
 Atlantic Ocean. Northwest of the Appalachian Eozoic we 
 find strata indicated by full oblique lines in one direction 
 and broken oblique lines in the other direction. These are 
 explained in the u legend" to mean that the rocks are 
 either Cambrian or Silurian (Lower Silurian or Upper Silu- 
 rian, as some geologists prefer to say), but we have not yet 
 ascertained which. These must dip northwesterly, away 
 from the older Eozoic, and toward the newer Upper Carbo- 
 niferous. Passing under all the Carboniferous, they come 
 to the surface again in Tennessee, Kentucky, Ohio and 
 Indiana, where we have learned them well enough to dis- 
 tinguish both Cambrian and Silurian (or, as some say, Lower 
 and Upper Silurian). On the north, Cambrian and Silurian 
 corne up along the two shores of Lake Ontario. From this 
 region the dip is southward all the time until we reach cen- 
 tral Pennsylvania. In southwestern Ohio, the Cambrian 
 which comes up from the southeast soon dips down again 
 
112 GEOLOGICAL EXCURSIONS. 
 
 toward the northwest, and passing under Michigan and Lake 
 Michigan, comes up again in eastern Wisconsin. Now try 
 and follow the Cambrian and Silurian up and down all the 
 way from the Appalachian Eozoic. 
 
 You must not be content to simply read these descrip- 
 tions. You must, by all means, follow the systems of strata 
 on the map. When they go under, your thoughts must fol- 
 low them. When they appear in view again, your thought 
 must see them coming from under the newer strata. You 
 must look under the surface of the map and see the solid, 
 thick crust of the earth with its various strata curved and 
 overlapping, and discontinuing and beginning again, disap- 
 pearing arid outcropping just as I describe them. If you do 
 this, and perform plenty of such exercises as will be given 
 you, the study will soon be easy and delightful. If you do 
 not, you will never have a good knowledge of geology. 
 
 Now let us continue the explanation of the map. On the 
 southwestern border of the Wisconsin Eozoic, you see the 
 Cambrian overlying it, and thence dipping southwesterly 
 under Silurian, Devonian, Lower Carboniferous and Upper 
 Carboniferous. We can trace it, in thought, under all these 
 systems into Missouri and Kansas. We might reasonably 
 expect the Eozoic to come to the surface again in the region 
 farther southwest, but it scarcely succeeds in revealing itself. 
 You will notice one patch in the Indian Territory, and one 
 in southern Texas ; but nearly all that region has been cov- 
 ered by Jura-Trias, and then most of that has been covered 
 by Cretaceous. Even upon the top of the Cretaceous are 
 some patches of Tertiary. 
 
TO THE GEOLOGICAL MAP. 113 
 
 In New England you will notice considerable areas 
 marked Eozoic ; but in some cases we only know that the 
 rocks are crystalline like Eozoic, while they may be in 
 reality only later rocks hardened and crystallized by meta- 
 morphism. You observe, however, a patch of Upper Car- 
 boniferous in Rhode Island, and a belt of Jura-Trias running 
 through Connecticut and Massachusetts. Farther north you 
 will notice that the valley of the Connecticut is underlaid by 
 Cambro-Silurian rocks that is, rocks either Cambrian or 
 Silurian. 
 
 In the Adirondac region of New York is an interesting 
 Eozoic area. This connects with the Canadian Eozoic by a 
 narrow neck across the St. Lawrence River. The strata all 
 around this Adirondac area dip away from it. This is a case 
 somewhat like the Eozoic area in Wisconsin. On the other 
 hand, the centre of Michigan is an area of Upper Carbonif- 
 erous, and since the surrounding strata are all older, they all 
 dip toward the centre of Michigan. 
 
 Now let us vary the method of study. Suppose we stand 
 on the southern side of Lake Ontario, the map shows that 
 the dip of the rocks is south ; for at that point we have Silu- 
 rian, while to the south are the (newer) Devonian and Lower 
 and Upper Carboniferous ; and, according to the rule, the 
 dip is toward the newer and away from the older in Canada. 
 
 If we stand at Milwaukee, the dip is eastward, for Mil- 
 waukee is on the Silurian, and eastward we have the Devon- 
 ian and Lower and Upper Carboniferous in Michigan. Lake 
 Michigan must also cover a portion of the Silurian and 
 much of the Devonian. If, on the contrary, we stand at 
 
114 GEOLOGICAL EXCURSIONS. 
 
 the St. Clair River, the dip is westward on the same 
 principle. 
 
 Again, if we stand at Sandusky, Ohio, we are on the Silu- 
 rian ; and if we walk straight to Cincinnati, we walk a long 
 distance on Silurian, and then come to Cambrian. Then if 
 we continue our travel to Nashville, Tennessee, we pass 
 again over Silurian, a narrow belt of Devonian, a broad belt 
 of Lower Carboniferous, and then come to a very narrow 
 streak of Silurian again (too narrow to show on the map at 
 this place, though it can be seen south of the Cumberland 
 River), and end our journey on the Cambrian. Should 
 we continue southward to Mobile, we should pass off 
 the Cambrian directly upon the Lower Carboniferous, 
 which extends into Alabama. Then, in the neighborhood 
 of Tuscaloosa, we should pass upon the Upper Carbonifer- 
 ous and beyond this to the overlying Cretaceous, and should 
 find Mobile on the Tertiary. 
 
 If we should travel from Albany to Boston, we should 
 start on Cambrian rocks and pass to Silurian rocks. Before 
 reaching central Massachusetts we should pass to rocks 
 which are not fully determined perhaps Cambro-Silurian, 
 and perhaps also an outcrop of Eozoic. Crossing the 
 valley of the Connecticut, would be found Jura-Trias rocks 
 resting horizontally in a trough excavated in the older 
 rocks. Those on the map are not extended far enough 
 north. Beyond this valley we should find again rocks 
 which are perhaps Cambro-Silurian. Beyond these we 
 should have Eozoic rocks for the greater part (all Eozoic 
 
TO THE GEOLOGICAL MAP. 115 
 
 on the map) until reaching Boston. All these things and 
 a thousand others may be studied out on the map. 
 
 EXERCISES. 
 
 If you travel in a straight line from Detroit to Milwaukee, 
 what systems of strata will you pass over? What, if you travel 
 from Mackinac to Cincinnati? What, between Oswego and 
 Plattsburg? What, between Charleston and Nashville? State 
 the dip of every system of strata passed between St. Louis and 
 Chicago. Between Duluth and Lake Michigan. Between Sagi- 
 naw and Springfield, Illinois. Between Springfield and Cincin- 
 nati. Between Cleveland and Pittsburgh. What is the dip of 
 the strata at Cleveland ? What, at Green Bay ? What, at Bing- 
 hamton, New York ? What, at Utica, New York ? Suppose you 
 bore an artesian well at Lansing, Michigan, what systems of 
 strata will be passed through ? What, if you bore at Charleston, 
 South Carolina ? What, if you bore at Hartford, Connecticut ? 
 What, if you bore at Peoria, Illinois? What, if you bore at 
 Galveston, Texas ? What, if you bore at Montreal, Canada ? 
 Would an artesian well bored at Cincinnati pass through the Silu- 
 rian ? Or the Devonian ? How could you travel from Albany, 
 New York, to St. Paul without passing off the Cambro-Silu- 
 rian? How from Cairo to Cape May without passing off the 
 Tertiary? How many great patches of Upper Carboniferous 
 (Coal Measures) are shown on the map? Into what states does 
 the Appalachian coal area reach ? Into what states, the Illinois 
 coal area ? Into what, the Kansas coal area ? Into what, the 
 Michigan? Into what, the Rhode Island? Which state has the 
 largest area of Eozoic rocks? Which next? Which has the 
 largest area of Tertiary? Which state contains the greatest 
 number of different systems ? Which contains the fewest dif- 
 ferent systems? What states have the largest amount of soft 
 rocks ? What ones have most Palaeozoic rocks? Give the names 
 of the cities indicated by black dots on the map, and state what 
 system of rocks each is located on. 
 
116 GEOLOGICAL EXCURSIONS. 
 
 EXCURSION XXI. To the Geological Map. 
 Geological Sections. 
 
 One of the most useful things for a student of geology 
 is to take exercises on the geological map. One object 
 of the study is to learn the geology of various parts of 
 the country. You must not look merely upon the flat 
 surface of the map. It is not enough even to learn the 
 location of the different colors lying on the surface. You 
 must think of each color or system of markings as an 
 outcropping of something which goes down beneath the 
 surface. You must try to follow it beneath the surface to 
 some other region where it outcrops again. You must 
 think which way it goes beneath the surface that is, what 
 is its dip. The rule already given determines that. So, 
 when you look on the geological map you will learn to 
 look into it, and far beneath the surface. You will then 
 see the whole solid framework of the rocks which underlie 
 a country. 
 
 Now we shall undertake some exercises which will 
 give us the power of penetrating into the depths of the 
 solid crust. With the geological map before us, we will 
 try to construct some geological sections. That is, if we 
 could cut straight down along the line between two points 
 which may be selected, to the depth of some thousands of 
 feet, and then look at the cut edges of the strata, what 
 form and arrangement would they present to us ? 
 
 To begin with a simple case, let us construct a section 
 across the State of Michigan from Detroit to Grand Haven. 
 
TO THE GEOLOGICAL MAP. 117 
 
 We will first draw a line G D, Figure 38, to represent 
 the distance along the surface between 
 
 __ G(jc b a D 
 
 the two points. We suppose ourselves "- ' 
 
 FiG.38. PREPARING FOB 
 
 facing north. We notice that Detroit A GEOLOGICAL SEC- 
 stands on the Devonian. Take the 
 distance from Detroit to the western border of the Devo- 
 nian, and lay it off from D on the line G D. This distance 
 extends to a. Next, lay off from a the distance which 
 corresponds to the breadth of the Lower Carboniferous in 
 the direction from Detroit to Grand Haven. This stretches 
 to b. Thirdly, lay off the distance which our route passes 
 over the Upper Carboniferous. This takes us to c. 
 Fourthly, lay off the distance to the western border of 
 the Lower Carboniferous ; this takes us to d. Finally, 
 lay off the short distance to Grand Haven on the border 
 of Lake Michigan. This takes us to G. 
 
 Next, we have to consider what is the dip of the strata 
 at each point. On our principles, the dip is toward the 
 Upper Carboniferous from both ends of the line. Draw 
 lines down obliquely, according to the 
 dip, from , , c and d, Figure 39, the 
 boundary points between the forma- 
 
 FIG. 39. PROGRESSING 
 
 tions. Then, knowing that the Lower WITH A GEOLOGICAL 
 
 SECTION. 
 
 Carboniferous, which dips down west- 
 ward in the eastern part of the state, is the same which 
 comes up to the surface from the eastward, in the western 
 part of the state, we can connect the lines representing 
 the lower and upper surfaces of this system. That is, 
 the upper line will extend from b to <?, passing down under 
 
118 GEOLOGICAL EXCURSIONS. 
 
 the Upper Carboniferous; and the lower line will extend 
 from a to d, passing under both Upper and Lower Car- 
 boniferous. The dip of the strata from D must pass in the 
 same direction as from a and . But notice that Detroit 
 is not on the eastern limit of the Devonian. The line from 
 the eastern limit wherever it is will pass some distance 
 under Detroit, as at e. We need not know where it comes 
 up to the surface. It is somewhere to the eastward, but 
 we may cut it off at 6, as we are only required to construct 
 the section to Detroit. That line, then, ending at 0, shows 
 the bottom of the Devonian. Passing westward it will 
 come up at the west side of the Devonian, wherever that is. 
 But the first system west of Lake Michigan is the Silurian, 
 and the place for the bottom of the Devonian is between 
 it and d, near Grand Haven. The western outcrop of the 
 bottom of the Devonian seems to be in the bottom of Lake 
 Michigan. This belief is confirmed by observing that on 
 the map, the outcrop of the Devonian strikes the south 
 end of Lake Michigan and seems to pass under the lake. 
 It comes mostly from under the lake again in the region 
 of Grand Traverse and Little Traverse Bays and Mackinac. 
 We will therefore assume that the western outcrop of the 
 Devonian is under the lake. We will also draw a little 
 depression to represent the bed of the lake. 
 
 So far we have assumed that the surface is a dead level 
 from Detroit to Grand Haven ; but if we happen to know 
 that the centre of the state swells up a little, we should 
 so represent it. We ought, indeed, to know this ; because 
 if you look on any map of Michigan you see the streams 
 
TO THE GEOLOGICAL MAP. 
 
 119 
 
 all flowing from the interior into the surrounding lakes. 
 If, then, we show the surface configuration, our section 
 will be a geological profile. Here it is, in Figure 40, but 
 
 FIG. 40. COMPLETED GEOLOGICAL SECTION BETWEEN DETROIT AND 
 
 HAVEN, MICH. 
 
 on a scale twice as large. In completing the section we 
 may bear in mind that the Silurian which outcrops at 
 Milwaukee passes under Lake Michigan and the state of 
 Michigan, and we may so represent it, though a section 
 across Michigan does not require this. It would be 
 proper also to represent the Cambrian under the Silu- 
 rian, since we see from the map that on the west of Mil- 
 waukee it passes eastward under the Silurian. And, 
 finally, we notice that in central Wisconsin the Eozoic 
 passes southward under the Cambrian ; and we may fairly 
 assume that it would appear beneath the Cambrian under 
 Michigan' if we were able to make actual examination. So 
 we fill in the lower left-hand corner of our section with the 
 marks indicating Eozoic. Now the section is complete. 
 
 We have, in fact, extended the section farther west than 
 was required. We might have cut it off at Grand Haven. 
 Also, we have carried it deeper than necessary. All that 
 is essential in a section from Detroit to Grand Haven is 
 shown by the broken lines. 
 
120 GEOLOGICAL EXCUKSIONS. 
 
 Next, let us construct a geological section from the 
 
 Eozoic north of Lake Ontario to William sport on the Coal 
 
 Measures of Pennsylvania ; and let us suppose ourselves 
 
 facing east. Draw a line E W, Figure 41, to represent the 
 
 length of the section. Then, allowing a 
 
 1-4 ' H ~ l '~^ H little space to the right of E for the 
 
 FIG. 41 .PREPARING FOR 
 
 A GEOLOGICAL SEC- distance to the southern margin of the 
 Eozoic, fix on a point a, for the border 
 of the Cambrian. The dividing line between the Cam- 
 brian and Silurian is under the lake ; let us locate it under 
 . The southern limit of the Silurian will be at c. The 
 southern limit of the Devonian will be at d\ and here the 
 Lower Carboniferous begins. The southern limit of the 
 Lower Carboniferous, which is the northern limit of the 
 Upper Carboniferous, will be at e. Then the southern 
 extremity of our section will be at W, just over the border 
 of the Coal Measures. 
 
 Now, we understand that all these rocks dip southward. 
 So we draw lines from the points #, 5, 
 
 KxAJ^ VjX^j c -> d-> e -> Figure 42, to represent the dip, 
 
 -^x| and terminate them at such points as to 
 
 FIG. 42. PROGRESSING n 
 
 WITH A GEOLOGICAL produce a neat ngure showing all that 
 is required. Then we may fill in with 
 the lines and characters chosen to represent the various 
 systems. 
 
 Notice that it is customary to represent the dip some- 
 what greater than the reality, especially when the real dip 
 is but slight. Notice, also, that this makes the thicknesses 
 of the formations too great to be in due proportion to the 
 
TO THE GEOLOGICAL MAP. 
 
 121 
 
 distances along the surface. All this is only for con- 
 venience. 
 
 We have constructed this section thus far on the 
 assumption of a dead level from end to end. But we 
 ought always to represent the relative elevations of dif- 
 ferent points as well as we- can. In fact, geologists often 
 take very great pains to ascertain the levels of different 
 points. If the region where E is located is somewhat ele- 
 vated, we should so represent it. And if we know that a 
 high bluff of strata extends along the south shore of Lake 
 Ontario, we should so represent that. An improved sec- 
 tion between the two points would be as shown, Figure 
 43. This is made on a scale four times as large as the 
 other, which is too small for convenience. Here we notice 
 a slope from north and from south toward Lake Ontario. 
 
 E 
 
 FIG. 43. COMPLETED GEOLOGICAL SECTION. 
 E, Canadian Eozoic. Co, Coburg. R, Rochester. C, Corning. W, Williamsport. 
 
 Also a slope from both directions toward the Chemung 
 Kiver. These things are not all shown by the map; but 
 if you can, in any way, obtain information about the con- 
 figuration of the surface, that should be introduced into 
 your section. You will often have to refer to your geo- 
 graphical atlas to learn where places mentioned are 
 located. The directions in which the streams run will 
 
122 GEOLOGICAL EXCURSIONS. 
 
 also show you what regions are more elevated, and what 
 are less elevated. 
 
 The following is the way we complete the geological 
 profile. Having laid down the necessary points along a 
 horizontal line A B, draw vertical lines from these points, 
 as shown, Figure 43, and draw as exactly as you can a 
 line E P, to represent the surface of the earth. The points 
 a, c, d, e, where this line intersects the vertical lines, indi- 
 cate the bounds of the different formations. From these 
 points we may draw lines to represent the dip and the 
 thickness of each formation. 
 
 You ought to take a great deal of exercise on the Geo- 
 logical Map, and especially in the construction of sections. 
 No matter if it requires two or three days to finish one 
 Excursion. 
 
 Let us construct a section from Nashville to Savannah. 
 Here it is (Figure 44). You will notice that the Cambrian 
 
 FIG. 44. SECTION FROM NASHVILLE TO SAVANNAH AND TH-E ATLANTIC 
 
 OCEAN. 
 
 east of Nashville is not known to be overlaid by Silurian; 
 and when we trace it to the east of the Appalachians it 
 is so metamorphosed that we are unable to say whether 
 it is Cambrian or Silurian, and so it is simply put down 
 on the map as Cambro-Silurian. After passing the dome 
 of Eozoic we find it overlaid directly by Tertiary strata, 
 
TO THE WHITE MOUNTAINS. 123 
 
 and we must so represent. Not unlikely, however, some 
 strata intermediate in age between Eozoic and Tertiary 
 would be found beneath the Tertiary if we could make 
 exploration. The Tertiary passes under the waters of the 
 Atlantic. 
 
 EXERCISES. 
 
 Construct sections as follows: From Madison, Wis., to Chi- 
 cago. From Chicago to St. Louis. From Sandusky, Ohio, to 
 Nashville, Tenn. From Mackinac to Cincinnati. From Montreal 
 to Albany. From New York City to Oswego. From St. Louis 
 to Cincinnati. From Cincinnati to Newbern, N. C. From St. 
 Paul to Chicago. From Cairo, 111., to Cincinnati. From Kings- 
 ton, Out., to Chicago. From Detroit to Fortress Monroe. From 
 Cleveland to Cincinnati, and thence down the Ohio to its mouth. 
 
 EXCURSION XXII. To the White Mountains. 
 The Eozoic Bocks. 
 
 You ought now to study a little more particularly the 
 different systems of rocks which you see indicated on the 
 geological map of the country. We will begin with the 
 Eozoic. Glancing at the map, you perceive that the largest 
 region where Eozoic rocks come to the surface is north of 
 the United States, but sending extensions southward into 
 Wisconsin and New York.' You see also indications of 
 the Eozoic in Maine, N"ew Hampshire, Massachusetts and 
 Rhode Island. There is also an extensive area along the 
 eastern flanks of the Appalachians. There are smaller 
 areas at New York City, in Dakota, Missouri, the Indian 
 
124 GEOLOGICAL EXCURSION'S. 
 
 Territory and Texas. In the western part of the country 
 are many other patches large and small ; but these are not 
 included in our map. 
 
 We could obtain good views of the Eozoic rocks by 
 visiting any of these regions. The most convenient for 
 most of us are the Eozoic rocks lying to the north. From 
 these came the boulders which overstrew all the region 
 south of the Eozoic down to the latitude of Cincinnati 
 the boulders whose different sorts we have so much studied. 
 If we visit the Eozoic regions, we shall find the same kinds 
 of rocks as bed-rocks ; and we shall find them exposed at 
 the surface in very many places. 
 
 Suppose ourselves in the region of the White Mount- 
 ains. We visit the Glen House on the east of Mt. Wash- 
 ington, and on each side of us rise the lofty rounded forms 
 which are characteristic of the Eozoic. In front is the 
 stupendous "Presidential Range," with the bald summits 
 of Mts. Madison, Adams, Jefferson, Clay, Washington, 
 Monroe, Franklin, Pleasant, Clinton and Webster rising 
 before us most of them in sight together. In the rear 
 of the Glen House rise the similarly bald and rounded 
 summits of the " Carter Range." If we go to the top of 
 Mt. Washington and look down on the country for fifty 
 miles in every direction, it seems to be a dark swelling 
 mass of mountain tops, nearly all of like shape. This is a 
 good illustration of the style of weathering which crystalline 
 rocks undergo. Granitic and gneissic regions seldom pre- 
 sent the pointed or angular features often shown by strata 
 belonging to some of the other systems. 
 
TO THE WHITE MOUNTAINS. 
 
 Here is a view of Mt. Kearsarge, one of the White 
 Mountains, showing the rounded forms of the summits. 
 (Figure 45.) There are some large boulders in the fore- 
 ground. In contrast with this I present you next a view of 
 pinnacled mountains, such as exist when their summits are 
 formed of schists turned up on edge. The summits formed 
 
 FIG, 45. MT. KEARSARGE AMONG THE WHITE MOUNTAINS, SHOWING ROUNDED 
 SUMMITS. BOULDERS IN THE FOREGROUND. (Photograph.) 
 
 of massive rocks like granite are evenly eroded by weather- 
 ing, and result generally in smoothly rounded forms, while 
 summits formed of schists turned on edge are eroded deep- 
 est in the spaces between the hardest strata, and this leaves 
 the hardest strata projecting. Such summits are called 
 " needles" in Switzerland. (See Figure 46.) Some of the 
 
126 
 
 GEOLOGICAL EXCURSIONS. 
 
 "White Mountain summits present pinnacled forms for a 
 similar reason. Mt. Chocorua is a pretty good example. 
 
 FIG. 46. THE NEEDLES OF CHARMOZ AND THE MER DE GLACE. 
 
 Now let us view these massive and schistose rocks a 
 little more closely. You will be amazed to see how they 
 have been upturned and folded. Often the strata stand 
 almost vertically on their edges ; and they are often crum- 
 
 FIG. 47. SECTION THROUGH MT. KEARSARGE, N. H. 
 
 Wilmot. W H, Wilmot House. Wh H, White House. P, Plumbago Pt. a, Porphy- 
 ritic Gneiss. 6, Andalusite Mica Schist, c 1 , Granite. 
 
TO THE WHITE MOUNTAINS. 
 
 127 
 
 Ss 
 
 pled like a pocket handkerchief. 
 You see this constantly in ascend- 
 ing Mt. Washington. I would be . g 
 
 o 
 
 glad to show you a section through 
 
 this mountain, but it has not yet g ^ 
 
 been thoroughly worked out by * g 
 
 geologists. Here (Figure 47) is ^ fe ,; 
 
 a section, however, through Mt. g ^ \\ 
 Kearsarge, the same whose summit 
 contour you have seen. It rises 
 
 in southeastern New Hampshire, gf | 
 
 and has been carefully studied by |^ | 
 
 Professor C. H. Hitchcock. It f | 
 
 shows how wonderfully the great o g 
 
 masses of the rocks have been 1 1 ^ - 
 
 folded, and afterward worn down. | g 
 
 P* <* 
 
 The dotted lines indicate the sup- ^ a & 
 
 A J~ *^ O 
 
 posed former extent of the strata. | 3 o ** 
 Next, in Figure 48, you have 
 
 <D 3 
 
 a carefully investigated section |. o 
 
 through the Eozoic rocks of Can- ^ g 
 
 ada, worked out by Sir William g ^ 
 
 Logan. The first thing which K 5 
 
 impresses you is the wonderfully f -^ 
 
 o o 
 
 wrinkled condition of the strata. . ^ 
 
 The dotted lines are intended to ^ g 
 
 show the connections of strata. | 
 
 So you see also evidence of a vast 
 
 amount of erosion. Notice here further the great limestone 
 
 ^^ Porphyry 
 
128 GEOLOGICAL EXCUKSIONS. 
 
 masses. In the upper one of these are found relics of the 
 first animals which ever lived on our planet. 
 
 Next follows a section through the Eozoic rocks of 
 Wisconsin. Here you see the two u systems" into which 
 
 Laurentian Huronian Cambrian 
 
 FIG. 49. SECTION ACROSS THE ROCKS OF WISCONSIN. (Chamberlin.) 
 
 1. Potsdam Sandstone. 2. Lower Magnesian Limestone. 3. St. Peter's Sandstone. 4. 
 Trenton Limestone. 5. Galena Limestone. 6, Cincinnati Shales. 7. Niagara 
 Limestone. 8. Lower Helderberg Limestone. 9. Hamilton Limestone. 
 
 the Eozoic is divided the Laurentian below and the 
 Huronian above. This section extends, toward the right, 
 through the other rocks of Wisconsin, which we shall 
 speak of hereafter. The Laurentian here and elsewhere 
 shown is composed of great masses of granites, gneisses 
 and schists, and in some regions includes great beds of 
 crystalline limestone, or marble. Much of the marble 
 of this continent is from the Laurentian. The Huronian 
 System of Rocks is composed chiefly of diorites, dia- 
 bases, quartzites, slates and conglomerates. Great beds 
 of iron ore are found both in the Laurentian and the 
 Huronian. They occur in masses between beds of other 
 rocks, and generally swell out to greatest thickness in the 
 middle, and taper off at each extremity. This may be 
 distinctly seen in the Marquette Iron Region. At Pilot 
 Knob in Missouri, however, in the Penokie Range of 
 Wisconsin, and many other regions, the iron ore forms 
 thick strata, which present a structure similar to that of the 
 
TO THE WHITE MOUNTAINS. 
 
 129 
 
 strata above and below. Figure 50 is a section across the 
 eastern portion of the Penokie Eange. Here the massive 
 Laurentian granites, gneisses and schists, L, are unconform- 
 ably overlaid by the Huronian slates, iron-schists, quartz- 
 ites and diorites, H. These are succeeded by the " South 
 Range" of copper-bearing rocks (Kewenian), C, consisting 
 of various bedded dolerites, with alternating beds of sand- 
 stones and conglomerates. Still farther north are the hori- 
 zontal sandstones of Cambrian age. The iron ores of 
 Northern JSTew York, and of many other parts of the world, 
 are found in rocks belonging to the Eozoic System. 
 
 FIG. 50. SECTION THROUGH AN IRON RANGE IN WESTERN MICHIGAN, BE- 
 TWEEN LAKE GOGEBIC AND MONTREAL RIVER, SHOWING POSITION OF THE 
 IRON ORE, AND THE RELATIONS OF FOUR SYSTEMS OF ROCKS. (Pumpelly 
 and Brooks.) 
 
 As these Eozoic rocks are seen everywhere to pass 
 under all the other rocks, they must have been formed 
 before the others. The Eozoic rocks are thought to be 
 not less than fifty thousand feet in thickness. And we hold 
 that they were originally sediments in the bottom of the 
 sea. All this indicates that a vast length of time must 
 have been occupied in laying down sufficient sediments to 
 form the Eozoic and all the other rocks. It would seem, 
 then, that this world has had a history, and a very long 
 
130 GEOLOGICAL EXCURSIONS. 
 
 history. We have to think, therefore, of the periods of 
 time spent, as well as of the work done. As the whole 
 work is divided into Systems and Great Systems of strata, 
 so the whole time is divided into Ages and Eras of time. 
 This is indicated in the Geological Column, Figure 29. 
 
 If the racks which make the White Mountains were at 
 first sediments in the bottom of the ocean, and are now 
 five or six thousand feet above the surface of the ocean, 
 it is plain that the old sediments must have been upraised 
 to the extent of a mile or two. Who can imagine the 
 power necessary to lift up the whole mass of the White 
 Mountains? Then consider the attitudes in which the 
 strata stand. Look again at the section of Mt. Kearsarge 
 and trace the dotted lines. They are intended to show 
 how the different strata seem to have been once connected 
 together. The solid rocks have been folded and over- 
 lapped, as if soft as molasses candy. What power could 
 mould the substance of mountains into such shape ? Look 
 again, also, at the Canada and Wisconsin sections, and note 
 the wonderful crumpling of the strata. These rocks are 
 solid and massive granites, syenites, quartzites, diabases 
 and schists. Plainly, the forces which could do such work 
 are inconceivably vast. These things lead us to cast our 
 thoughts backward over the world's long history. What 
 changes have taken place since the White Mountains were 
 soft mud in the bottom of the sea! Indeed, we are just 
 getting glimpses of the world's grand history. It is the 
 business of geology to study these things, and find out, as 
 
TO THE UPPER MISSISSIPPI. 131 
 
 far as possible, what has been the nature of the events 
 which have made up the history of our planet. 
 
 EXERCISES. 
 
 Is there any connection between the Eozoic of Wisconsin 
 and the Eozoic of Missouri ? Has it ever been proved that the 
 Eozoic exists underground in regions where it does not appear at 
 the surface ? In boring to a great depth, how would we know 
 when Eozoic rocks are reached? Do you think an artesian well 
 likely to be found in Eozoic rocks? If not, why not? Were 
 the first animals land or water animals ? Were they fresh-water 
 or marine animals? Would you expect them to be high or low 
 in rank ? What is the reason why the Adirondack mountains 
 have no Cambrian strata over them? When you find Eozoic 
 rocks exposed, can you feel certain that no strata ever covered 
 them? Look at the Eozoic in Georgia; is there any reason to 
 suppose the Cambro-Silurian ever extended any farther south- 
 east ? How is it possible that Cambro-Silurian rocks ever lay 
 between the Eozoic and the Tertiary in Georgia? Could such 
 rocks have been swept away in some age before the Tertiary 
 were laid down ? What system of rocks appears on Manhattan 
 island? Are the artesian wells in Brooklyn bored into Eozoic 
 rocks ? 
 
 EXCURSION XXIII. To the Upper Mississippi. 
 Cambrian (or Lower Silurian) Rocks and History. 
 
 By looking over our little geological map, you notice 
 several regions covered by the lines which indicate Cam- 
 brian or Lower Silurian. One of the largest of these 
 regions covers much of Wisconsin and Minnesota on both 
 sides of the Mississippi River, and stretches eastward through 
 northern Michigan and the Manitoulin islands. Another 
 
132 
 
 GEOLOGICAL EXCURSIONS. 
 
 stretches along the north side of Lake Ontario, and across 
 northern New York into Vermont, New Hampshire and 
 Massachusetts. Another region is in southern Ohio and 
 northern Kentucky ; and within this are the cities of 
 Cincinnati, Lebanon, Madison and Richmond, Ind., and 
 Frankfort and Lexington, Ky. Another region is in Ten- 
 nessee, and this embraces Nashville, Lebanon, Columbia 
 and Franklin. Still another extensive region stretches 
 
 FIG. 51. BLUFFS ON THE UPPER MISSISSIPPI. 
 (D. D. Owen.) 
 
 CAMBRIAN ROCKS. 
 
 along the east side of the Appalachian mountains. You 
 should trace out the boundaries of each of these Cambrian 
 regions, and see what states and provinces they partly cover, 
 and what cities are included in them. To do this you will 
 have to study also the common school-atlas ; but it will be 
 very interesting and profitable. 
 
 You would be delighted to visit any of these regions and 
 see what kind of rocks the Cambrian rocks are how much 
 
TO THE UPPER MISSISSIPPI. 133 
 
 less hard they are than the Eozoic rocks, and how much less 
 tilted and crumpled. You would wonder also at the strange 
 forms of the fossils in the rocks that is, the shells and 
 other remains of animals which lived in the sea when these 
 rocks were soft sediments accumulating on the bottom. Let 
 us first go to the Upper Mississippi. If we ascend the 
 river by steamer to St. Paul, we shall see high rocky bluffs 
 
 FIG. 52. "HORNETS' NEST," Wis. EROSION OF CAMBRIAN ROCKS. 
 (Chamberlin.) 
 
 rising along one shore or the other, and sometimes on both 
 shores, most of the way from Prairie du Chien. The 
 upper portion of the bluff is generally a rusty irregular 
 magnesian limestone, while below this lies a great sandstone 
 formation. Figure 51 shows the appearance of these bluffs 
 at many places. Here are evidently two ledges or forma- 
 tions of strata, and a great amount of earth has accumulated 
 
134 
 
 GEOLOGICAL EXCURSION'S. 
 
 at the foot of eacli ledge, almost? burying it out of sight. 
 This earth has resulted largely from the disintegration of 
 the rocks. The lower ledge here is the great sandstone, and 
 the next is the magnesian limestone. In many places these 
 formations are less buried, and we have high vertical cliffs 
 of buff sandstone and limestone as shown in Figure 23. 
 The strata shown in Figure 22 are sandstone of the 
 same age. 
 
 The weathering of these rocks in Wisconsin and Minne- 
 sota has resulted in many remarkable forms. Figure 24 is 
 an example ; and Figure 52 is another. Here the underlying 
 sandstone weathers away, and leaves the more durable 
 magnesian limestone overhanging. In other cases, enor- 
 mous towers are left 
 standing in the midst of 
 a plain, showing how ex- 
 tensively formations have 
 been swept away. Fig. 
 53 is an example of this 
 kind in Dakota county, 
 Minn. Here the isolated 
 column is over 19 feet 
 high above the base, 
 which is itself 25 feet 
 
 FIG. 53. "CASTLE ROCK," MINN. OUT- high? making the whole 
 LIER OF CAMBRIAN ROCKS. (Photo- outlier 44 feet 7 inches 
 graph.) . 
 
 above the sandy plain. 
 
 As we ascend the river, these formations gradually lower. 
 "When we reach Fort Snelling near St. Paul, we see a white 
 
TO THE UPPEK MISSISSIPPI. 135 
 
 sandstone formation on the top of the magnesian limestone, 
 and rising vertically from the water. It may really be found 
 at the top of the bluff most of the way from Mac Gregor. 
 In Figure 51 is an indication of it in a third terrace. This 
 sandstone \& friable ^ that is, it easily crumbles to pieces. It 
 is called the St. Peter's Sandstone, while the lower one is 
 the Potsdam Sandstone. 
 
 When we go back from the river to the Falls of Minne- 
 haha near Fort Snelling, we find a limestone formation still 
 higher in the series. This extends to St. Paul, and makes 
 the high limestone bluff there and at Minneapolis. It is 
 called the Trenton Limestone. The Falls of St. Anthony at 
 Minneapolis are caused by a precipice in the Trenton Lime- 
 stone. All these great formations together make up what is 
 called the Cambrian or Lower Silurian. Here are the names 
 in regular order above the Eozoic : 
 
 f Trenton Limestone. 
 
 St. Peter's Sandstone. 
 CAMBRIAN SYSTEM \ 
 
 | Lower Magnesian Limestone. 
 
 [ Potsdam Sandstone. 
 Eozoic GREAT SYSTEM. 
 
 a a a b 
 
 FIG. 54. SECTION ALONG THE VALLEY OF THE UPPER MISSISSIPPI. CAMBRIAN 
 ROCKS, a. Eozoic rocks, b. Potsdam Sandstone, c. Lower Magnesian 
 Limestone, d. St. Peter's Sandstone, e. Trenton Limestone. 
 
 And here is a diagram or ideal section along the Upper 
 Mississippi showing how these formations succeed each 
 
136 
 
 GEOLOGICAL EXCURSIONS. 
 
 other. Notice the Eozoic system of rocks at the bottom. 
 They are much more disturbed than the Cambrian above, 
 and are much contorted. A difference in the dip between 
 two formations, such as you see here, is called an uncon- 
 formability. This is illustrated also in Figures 49 and 50. 
 Notice also, the irregularity of the surface of the Eozoic 
 rocks. It looks as if they had been extensively worn away 
 before the Potsdam Sandstone was deposited upon them. 
 This shows that a long interval of time passed after the 
 Eozoic rocks were formed and disturbed, before the epoch 
 of the Potsdam began. Then the Potsdam sands were laid 
 down in nearly horizontal beds, accumulating most deeply in 
 the hollows of the Eozoic. In this way the thickness of the 
 Potsdam Sandstone is very variable. Figure 49, across 
 the rocks of Wisconsin, shows some of the same things. 
 
 Notice also, how the upper surface of the Magnesian 
 Limestone is worn down irregularly. Here also, the over- 
 lying sandstone presents a very variable thickness. So 
 there is a ~break also between these two formations, though 
 we discover no discordance in their dips. 
 
 Now I will show you another section through these rocks 
 
 FIG. 55. SECTION IN SAUK Co., Wis. (Chamberlin.) B. Baraboo River. 
 D. Devil's Nose. W. Wisconsin River, separating Sank from Columbia 
 Co. a. North Quartzite Range, b. South Quartzite Range, d. Pots- 
 dam Sandstone, e. /. Upper portions of Potsdam Sandstone, g. Low- 
 er Magnesian Limestone, h. Drift. 
 
TO THE UPPER MISSISSIPPI. 137 
 
 a real section, studied out by the geologists of Wisconsin. 
 It is very remarkable. See Figure 55. The Eozoic beds 
 here exposed are Huronian quartzite. How surprisingly 
 irregular their upper surface! How the knobs of quartzite 
 protrude! On this wasted knobby surface the sands were 
 deposited which make the Potsdam formation. Toward the 
 right (south) we cannot see the bottom of the Potsdam. In 
 other places the Eozoic rises quite above the upper surface 
 of the Potsdam. But the Potsdam itself has also been 
 enormously eroded, or worn away, since the time when it 
 was first completed. See how it clings to the slopes of the 
 South Quartzite Range. These clinging masses seem to be 
 the ends of strata which once extended a great distance. 
 These same strata are preserved also, in the lower portions 
 of the singular towers which appear at the right of the 
 section. These, like the tower in Figure 53, are remnants 
 of vast sheets of sandstone and limestone which were once 
 unbroken and continuous over a large part of Wisconsin 
 and Minnesota. Such outlying remnants of a formation are 
 called outliers. So it appears that the present surface has 
 been extensively eroded. How precisely it resembles those 
 ancient surfaces at the top of the Lower Magnesian Lime- 
 stone and the top of the Eozoic. How plainly these things 
 teach us that after the close of the Eozoic there was a land 
 surface for a long time, which wasted away quite like our 
 present surface, and then the ocean overflowed again and 
 deposited the sands which afterward became consolidated in 
 the Potsdam Sandstone. And the ocean continued till 
 the Magnesian Limestone was deposited. Then the surface 
 
138 GEOLOGICAL EXCURSIONS. 
 
 of this was dry land again, and another long period of 
 erosion followed. Then the ocean came still again and 
 deposited the clean sand which became the St. Peter's Sand- 
 stone. And the ocean's work continued till the Trenton 
 Limestone was laid down. Then dry land was there again, 
 and other erosions began. The land surface seems to have 
 continued to our times and here we stand, beings of a day, 
 looking on it as the outcome of almost an eternity of years. 
 This is a little glimpse of the grand history of the world. 
 
 There are many interesting things about these Cambrian 
 strata, both in the Upper Mississippi region and elsewhere, 
 which must be passed over now, because I only expect you 
 to obtain some very simple ideas in this first course of study. 
 But you must learn something about these strata in the 
 Cincinnati region. If you look upon the little map, you 
 will notice that this region has coal measures upon the east 
 and upon the west. So, according to our law of dip, the 
 Cambrian rocks dip from the region of Cincinnati toward 
 the east on one side, and toward the west on the other. You 
 will notice, too, that rocks newer than Cambrian exist on the 
 north and south also. So the Cincinnati rocks dip north- 
 ward on the north, and southward on the south. You must 
 try to picture that arrangement to your mind's eye. When 
 you go to Cincinnati, you will see the high hills surrounding 
 the city on three sides. From the tops of the hills the 
 country extends somewhat level as far as you can see. 
 When you visit the hills you will notice the out-cropping 
 edges of limestones and shales and clay strata. From these 
 outcrops these strata pass into the hills, under the country 
 
TO THE UPPER MISSISSIPPI. 
 
 139 
 
 on all sides. If we were to construct a section across this 
 region from east to west, it would look somewhat like this 
 diagram, Figure 56. The Potsdam Sandstone is underneath 
 
 h fedcb a bcdeg 
 
 FIG. 56. SECTION ACROSS THE CINCINNATI SWELL. C. Cincinnati, a. b. 
 Cambrian, c. Silurian, d. Devonian, e. Waverly. /. Carboniferous 
 Limestone, g. Equivalent of Carboniferous Limestone on the easterly 
 side. h. Illinois Coal Field, i. Appalachian Coal Field. 
 
 the Trenton Group, which is the only Cambrian here 
 exposed. We find nothing here called St. Peter's Sandstone, 
 but geologists believe that the rocks immediately below the 
 Trenton, before we come down to the Potsdam proper, 
 correspond to the St. Peter's Sandstone and the Lower 
 Magnesian Limestone. 
 
 The Potsdam Sandstone is not everywhere the formation 
 which rests immediately on the Eozoic. In Nova Scotia, 
 in eastern Massachusetts and northwestern Vermont, and 
 in many other regions, are slaty strata older than the Pots- 
 dam and called Acadian. So in different regions are other 
 differences in the kinds of rocks. But geologists have 
 agreed to arrange all the Cambrian strata, in all parts of the 
 country, in three groups ; and here are their names : 
 
 CAMBRIAN SYSTEM * 
 
 Trenton Group. Same as described in Wisconsin and 
 
 at Cincinnati. 
 Canadian Group. Includes St., Peter's Sandstone 
 
 and Lower Magnesian Limestone. 
 Primordial Group. Includes Potsdam Sandstone and 
 
 Acadian Slates. 
 
140 GEOLOGICAL EXCURSIONS. 
 
 EXERCISES. 
 
 What system of rocks occupies the surface between Cincinnati 
 and Frankfort, Ky. ? Which way do these rocks dip at Frank- 
 fort ? How far in that direction do they continue under newer 
 rocks? Where do they come to the surface again? What 
 rocks are at the surface in central Tennessee ? Which way do they 
 dip ? Under what rocks do they disappear in southern Ten- 
 nessee ? How far do they continue their dip to the south of 
 Tennessee? Do the Cambrian strata pass under Mobile ? What 
 rocks are at the surface at Mobile ? What system of rocks must 
 be bored through at Mobile before reaching the Potsdam for- 
 mation ? Put yourself at the city of Green Bay, Wis., and walk 
 along the outcropping edge of the formation ; in what direction 
 do you travel ? Which side of Green Bay will you travel to 
 keep on the Cambrian strata? How far can you travel along 
 those strata, and what places will you pass ? Name some places 
 in New York which are on Cambrian strata. Mention all 
 the Cambrian regions in the United States. 
 
 EXCUKSION XXIY. To Niagara Falls. 
 Silurian Hocks and History. 
 
 When we stand by the brink of the world-renowned 
 Falls of Niagara, we see an enormous mass of water pour- 
 ing over a precipice into a deep and fearful gorge. The 
 sublimity of the scene absorbs all our attention and all our 
 interest. Still, we must present ourselves at Niagara in a 
 mood to study the causes of this stupendous cataract. It 
 is an excellent place for one who wishes to get some insight 
 into the great facts and teachings of geology. 
 
 First, there is the great gorge a hundred and fifty feet 
 deep down to the water; and then at least a hundred and 
 
TO NIAGARA FALLS. 
 
 141 
 
 fifty feet still deeper beneath the surface of the rushing 
 river. Look along the walls of the gorge. There are 
 numerous distinct beds or strata of rock divided from each 
 
 FIG. 57. TABLE ROCK AS IT WAS. 
 
 other by joints or seams. Your eye can trace them a long 
 distance down the stream toward the old railway suspension 
 bridge. Notice that they all continue to rise slowly nearer 
 the surface as they extend northward down the stream. 
 Walk down to the bridge. You can trace these strata 
 all the way. You see, however, that they gradually rise. 
 You may take the railway which runs along the bank of the 
 gorge on the American side to its termination, about five 
 miles below. Here, if you look east or west, you see a 
 high bluff of rocks facing north toward Lake Ontario. 
 This great Niagara gorge looks as if it had been worn 
 out by the river. We think it has. 
 
 If you return to the Falls, you see that the rock at 
 the surface there is a limestone. The Falls pour over the 
 
142 
 
 ' GEOLOGICAL EXCURSIONS. 
 
 235ft. 
 
 broken edge of it. This 
 is the Niagara Limestone. 
 You can trace it along the 
 upper part of the gorge 
 all the way to Lewiston. 
 Different strata of it keep 
 coming to the surface and 
 terminating. It must be 
 much thinner, therefore, 
 at Lewiston than it is at 
 the Falls. Above the 
 Falls it may be traced to 
 the head of the "Kapids." 
 There is a way by which 
 curious and adventurous 
 people may go behind the 
 Falls, so that the mighty 
 cataract pours down in 
 front of them. It is a wet 
 and slippery place, but we 
 can learn some geology 
 there. Above us is the 
 great Niagara Limestone 
 here we are, underneath 
 it. We see that it rests 
 on a thick mass of shale. 
 This shale is a part of the 
 series of strata, and may 
 be traced along the gorge 
 
 38 ft. above L. Erie 
 
TO NIAGARA FALLS. 143 
 
 all the way to Lewiston. It is the so-called Niagara Shale. 
 At this place it is worn away from under the limestone, 
 and makes the shelter where we stand. It is continually 
 crumbling down, and making the shelter deeper. Some- 
 times it gets so deep that the overhanging limestone is not 
 strong enough to bear its own weight and the weight of the 
 water over it. Then great blocks of the limestone break 
 off, and fall down into the abyss of foaming water. Thus 
 the brink of the precipice is moved a little farther up 
 stream, and the brink of the Falls is also moved. This is 
 the "recession of the Falls." Now it may be that this 
 shows how the whole gorge has been made all the way 
 from Lewiston. But the extension of the gorge by such 
 means would be slow, you say. Well, it has been shown 
 that the Falls have receded one hundred feet in thirty-three 
 years. That is considerable. 
 
 In Figure 57 is shown a remarkable projecting table of 
 the Niagara Limestone on the Canadian side. This was 
 formerly a striking feature of the spot, but it exists no 
 more. People used to enjoy the excitement of standing 
 upon it. But eventually "Table Rock" broke off by frag- 
 ments, and fell to the bottom of the gorge. Goat Island 
 is disappearing in a similar way. So the work of erosion 
 goes on before our eyes. 
 
 Underneath the Niagara Shale may be traced a thin 
 band of limestone, with a thin band of shale under it. 
 These represent the Clinton formation, which in some 
 regions is much more important than here, and contains 
 beds of iron ore, but quite different from that of the 
 
144 GEOLOGICAL EXCUESIONS. 
 
 Eozoic. Below these strata, in the lower part of the gorge, 
 may be seen strata of red, gray and variegated sandstone. 
 This is the Medina Sandstone, and it passes downward 
 into the Oneida Conglomerate. The Medina Sandstone is 
 quarried near Eochester quite extensively, for sidewalks, 
 pavements and building purposes. All these formations 
 together make up the so-called Niagara Group of rocks. 
 
 If you look on our little geological map, you will trace 
 the Silurian System of rocks eastward from the Niagara 
 Kiver through central New York. In Onondaga and Cayuga 
 counties we have fine opportunities to see the formation 
 which lies next above the Niagara Group. It consists of 
 shales, clays and impure limestones, with abundance of 
 brine and considerable beds of gypsum. The latter is often 
 ground into plaster to spread on farming lands, or to burn 
 till all the water is driven off, and then employ in plastering 
 the walls of houses. The brine oozes out of the formation, 
 and saturates the marshes at Syracuse. In these wells are 
 dug, and the brine is pumped out for boiling away to make 
 salt. This is the Salina Group. Its outcrops extend west 
 from Syracuse to the Niagara Eiver above the Falls (see 
 Figure 58), and thence through Canada to Lake Huron. 
 You can trace it on the map. Its place is south of the 
 middle of the Silurian belt everywhere. At Goderich, on 
 Lake Huron, wells are bored till they reach the Salina 
 Group, and rock salt is actually found. At Alpena, in 
 Michigan, the same has been done. Well, if rock salt can 
 be found in this formation in Canada and Michigan, why 
 not in New York? So queried some New York gentlemen, 
 
TO NIAGARA FALLS. 145 
 
 encouraged by the geologist, and, by boring in western 
 New York, they also found rock salt. And now the regions 
 about Warsaw and Le Roy, in Wyoming and Genesee 
 counties, are new centres of great activity in salt produc- 
 tion. Why should they not bore south of Syracuse and 
 find rock salt? 
 
 Now, if we try to trace the Niagara and Salina groups 
 eastward toward the Hudson River, we find them growing 
 thinner, and becoming lost to observation. But, on the 
 other hand, some limestone beds above the Salina, which 
 are thin in western and central New York, become much 
 thicker in eastern New York, and form the basal portion 
 of the Helderberg Mountains, which may be seen to the 
 south of the Central railroad when traveling a few miles 
 west of Albany. These limestones, together with some 
 shales, form the Helderberg Group. This can be traced 
 westward from Buffalo to the islands in the western end 
 of Lake Erie, and thence south through central Ohio, 
 covering a broad belt just off the western border of the 
 Devonian. It is found also in Indiana, Illinois and Mis- 
 souri; as also in Massachusetts, New Hampshire and Maine; 
 and very extensively in the provinces of Quebec, New 
 Brunswick and Nova Scotia. So the Silurian System is 
 made up of these groups as follows: 
 
 f Helderberg Group. 
 SILURIAN SYSTEM -j Salina Group. 
 [ Niagara Group, 
 
146 GEOLOGICAL EXCURSIONS. 
 
 EXERCISES. 
 
 What part of Ontario has Silurian rocks at the surface? Of 
 what age are the cliffs along the east side of Green Bay? Of 
 what age are those on the west side ? Suppose a deep well is 
 bored at Cincinnati, would it ever reach Silurian rocks? Explain 
 this. Mention some other city geologically situated like Cincin- 
 nati. Name all the important cities built on Silurian rocks. 
 Of what age is the limestone quarried near Chicago ? Can you 
 name towns near Chicago which are famous for their fine quar- 
 ries? Are there any Silurian quarries in Massachusetts? The 
 Manitoulin Islands are Cambrian on one border and Silurian on 
 the other; which border should be Silurian ? Which way do the 
 strata dip at Madison, Wis. ? Are there any Niagara Limestone 
 quarries in the Lower Peninsula of Michigan ? Could there be 
 any limestone quarries at Milwaukee? If there are any limestone 
 quarries at Rochester, N. Y., what is the name of the limestone ? 
 Are there any limestone quarries at Potsdam, N. Y.? Should an 
 artesian well be bored at Chicago, what is the first sandstone 
 formation which would be reached ? Where does that sandstone 
 come to the surface? Where do the rains go which fall on that 
 sandstone in the region of its outcrop ? 
 
 EXCURSION XXV. To MacUnac. 
 Devonian Bocks. 
 
 In the straits connecting Lake Michigan with Lake 
 Huron is a small island, which you can hardly find on the 
 map, called Mackinac Island. But when you pass that way 
 on a steamer, you see it rising 318 feet above the water, and 
 bounded on all sides except the south by a perpendicular 
 wall of limestone. This island is a delightful place of sum- 
 mer resort. 
 
TO MACKINAC. 147 
 
 On the west, on the main land of the Upper Peninsula, 
 and south, on the main land of the Lower Peninsula, rise 
 high bluffs of the same kind of limestone, though not so 
 high. One cannot help believing these bluffs were once 
 connected with Mackinac Island. Here, in Figure 59, is a 
 a section through the island. 
 You see the same flinty con- 
 glomerate at the base of the 
 island and at the base of Kab- FlGURE 59.-s ECT ioN SOUTHEAST AND 
 
 NORTHWEST THROUGH MACKINAC ISL- 
 
 bit's Back On the main land. AND. DEVONIAN ROCKS, a, Old Fort 
 
 Holmes; &, Sugar Loaf; c, Robinson's 
 
 You also see the same broken Foiiy, a, Rabbits Back on the upper 
 
 ,. , , , Peninsula; e. Round Island; f, Con- 
 
 limestone above the COngloiTl- gi om eritic Stratum; m, Surface of the 
 
 erate at both places. The Lake ' 
 
 deep valleys between the island and the main land, and 
 between the island and Round Island, have been dug out 
 of the solid limestone, and into the Niagara limestone, 
 which lies below, by some agency of wonderful power. 
 The valleys are now occupied by the water of the straits. 
 In fact, these limestones have been dug away through the 
 whole width of the straits, and only Mackinac Island 
 remains near the narrowest part, to show us how high the 
 rocks were once piled. This is another case of vast erosion, 
 which reminds us of what can be seen at Niagara gorge. 
 But there is no reason to think it was done by a river. And 
 yet, let us consider a moment. The water from Lake Michi- 
 gan flows through these straits and Lake Huron. Suppose 
 the straits not yet dug through. Suppose the solid lime- 
 stone stretches across from Old Mackinac, on the Lower 
 Peninsula, to Rabbit's Back. Lake Michigan would then 
 
148 
 
 GEOLOGICAL EXCURSIONS. 
 
 be dammed up. The rivers flowing into it would fill the 
 lake till the water would be high enough to flow over the 
 Mackinac barrier ; and then a river would exist there. Per- 
 haps a great waterfall once existed there, and dug a gorge 
 like Niagara, and the gorge receded till the limestone bar- 
 rier was cut through. Then Lake Michigan was drained to 
 the level of Lake Huron. Now, I do not say all this has 
 happened, but you can understand that it may have hap- 
 pened. Such reasoning as to how things have been made 
 as they are, belongs to geological theory. I do not intend 
 to offer you theories in connection with these Excursions, 
 but you ought to know what we mean by theories. 
 
 The principal mass of Mackinac Island rises only about 
 150 feet above the lake, and forms 
 a plain, covered by a forest growth. 
 At one point rises a cone-shaped 
 remnant of the higher limestone, 
 134 feet above this plain. The 
 higher limestone forms a smaller 
 or upper plateau, 294 feet feet 
 above the lake. (See Figure 60.) 
 
 On one of the sides of the island 
 the waves have worn through the 
 bounding cliffs, and dug under 
 
 the upper strata of the limestone, leaving a real natural 
 bridge. Both these works of geological erosion are great 
 natural curiosities. There are also overhanging cliffs and 
 caverns which always interest the visitor. The Indians 
 had many romantic tales connected with these localities. 
 
 FIG. 60. VIEW OF "SUGAR 
 LOAF," MACKINAC ISLAND. 
 Devonian Limestone. 
 
TO MACKI2STAC. 
 
 149 
 
 A cavern in the west escarpment is connected with tradi- 
 tions as thrilling and probably as mythical as those about 
 the "Dragon's Cave" on the Drachenfels. 
 
 The limestone of this island and 
 vicinity is called the Corniferous 
 Limestone, and it belongs to the 
 lower part of the Devonian System. 
 You will please turn frequently to 
 the "Geological Column," page 
 99, so as to keep track of the for- 
 mations about which you learn. 
 Now, if you examine the Geolog- 
 ical Map, you will see that the 
 Devonian extends westward from 
 Old Mackinac to Little Traverse 
 Bay. As the dip of the strata is 
 southward, you perceive that Little 
 
 Traverse Bay must be excavated in the higher strata of the 
 Devonian System. In fact, when we get to the head of 
 Little Traverse Bay, we find a cliff of a different kind of 
 limestone ; and. as we follow around the coast toward 
 Grand Traverse Bay, we see still other strata coming in 
 higher up the series. They consist of limestones, shales 
 and clays, and are packed full of fossil shells and corals. 
 The highest formation in this series is a black shale charged 
 with carbonaceous and bituminous matter. This series of 
 strata forms the "Hamilton Group." The high bluffs 
 which the Hamilton Limestones form on Little Traverse 
 Bay afford sightly and delightful situations for summer 
 
 FIG. 61. "ARCHED ROCK," 
 MACKINAC ISLAND. Devo- 
 nian Limestone. 
 
150 GEOLOGICAL EXCUKSIONS. 
 
 resorts. Here, and near here, are Petoskey, Bay Yiew and 
 Charlevoix. 
 
 A little farther toward the centre of the Peninsula we 
 find beds of shales and clays next in order above the Ham- 
 ilton Group. They attain a thickness of seven or eight 
 hundred feet, and constitute the Chemuny Group. They 
 contain here very few fossils. 
 
 Now, look again at the Geological Map, and trace the 
 Devonian System eastward. You see it passes under Lake 
 Huron, and comes to light again on the southeast shore. 
 Goderich stands on the Corniferous Limestone ; so do Lon- 
 don, Ingersoll and Woodstock. The system also passes 
 under a large part of Lake Erie. In New York you see 
 Buffalo on the lower part of the system. Near Buffalo are 
 found many fine Hamilton fossils. Farther east, we have 
 Caledonia, Le Roy and the higher part of Syracuse on the 
 Corniferous Limestone. This limestone forms prominent 
 ridges throughout its whole extent from Mackinac. You 
 see it strike east and west through central New York. At 
 Syracuse it rises in a lofty ridge, which is cut through by 
 Onondaga Creek. This runs north into Onondaga Lake. 
 On each side of the valley of that creek are high lime- 
 stone bluffs which present much fine scenery. Here is the 
 old settlement of Onondaga Hill on the west side. On the 
 east is Syracuse University. 
 
 Under the Corniferous Limestone, we find along this val- 
 ley a coarse, decomposing conglomeritic sandstone contain- 
 ing fossils quite unlike those of the Corniferous. This is 
 the Oriskany Sandstone. It is not a very important forma- 
 
TO MACKINAC. 151 
 
 tion, though we find it at intervals from Missouri to the 
 Gulf of St. Lawrence. I incline to regard the Oriskany as 
 the base of the Devonian, though some geologists prefer to 
 consider it the top of the Silurian. 
 
 The dip of the strata in central New York, as you will 
 observe, is toward the south. Hence, as you travel south 
 toward Cortland, you find the Hamilton limestones and 
 shales coining in above the Corniferous, and, in fact, piling 
 up the strata to a still higher level. These shales are full 
 of fossil shells, very well preserved. If we go on from 
 Cortland still farther south, we find the same kinds of 
 strata occurring above the Hamilton as have been mentioned 
 in Michigan only they are more sandy and harder, and 
 attain a greater thickness. These Chemung strata stretch 
 east and west through all the southern counties of New 
 York. They give rise to much picturesque scenery, fine 
 examples of which may be seen at Panama, in Chautauqua 
 county, and again at Ithaca, and in the vicinity of Cornell 
 University. At Watkins' Glen, at the south end of Seneca 
 Lake, the magnificent gorge before mentioned (Figure 21) 
 occurs in this formation. 
 
 Another glance at the Geological Map will show that 
 much of the central part of Ohio is also on the Devonian 
 System of strata. The cities of Columbus and Delaware 
 stand on the Corniferous Limestone. The Chemung shales 
 stretch all the way from southern New York, along the 
 south shore of Lake Erie, nearly to Sandusky, and thence 
 bend southward across Ohio to the Ohio River. Their posi- 
 tion on the map is along the east side of the Devonian belt. 
 
152 GEOLOGICAL EXCURSIONS. 
 
 Through Indiana, their place is on the west side of the 
 Devonian belt. 
 
 So we have four groups of rocks to make up the Devon- 
 ian System, and they are as follows: 
 
 fChemung Group. 
 
 DEVONIAN SYSTEM ^amilton Group. 
 
 Cormferous Group. 
 , 1^ Oriskany Sandstone. 
 
 EXERCISES. 
 
 Now explain why the Chemung should be along the western 
 border of the Devonian in Indiana, but along the eastern border 
 of it in Ohio. An artesian well was bored at Columbus, Ohio; 
 please state what groups of strata must have been passed through. 
 Is there any water-bearing formation underneath Columbus ? 
 Does it outcrop in any of the surrounding states ? What is the 
 nearest outcrop of the Potsdam Sandstone ? What do you judge 
 would be the prospect of getting water in an artesian boring at 
 Columbus ? Would the prospect be any better at Chicago ? 
 What is the age of the limestone at the Falls of the Ohio, at 
 Louisville ? What would be the first limestone struck in sinking 
 a shaft at Detroit? Would there be any prospect of striking 
 rock salt by boring at Rochester, New York ? Which way do 
 the strata dip at Lexington, Kentucky? Why are there no 
 Cambrian, Silurian or Devonian strata over the Adirondack 
 region ? Do you think any Silurian rocks ever covered the site 
 of Cincinnati ? What reason can you give for thinking as you do ? 
 
TO BURLINGTON, IOWA. 
 
 153 
 
 EXCUKSIOJST XXVI. To Burlington, Iowa. 
 The Lower Carboniferous Rocks, 
 
 We wish now to extend our survey of the rocks of our 
 country to the formations above the Devonian. Perhaps 
 the most favorable region for studying the Lower Car- 
 boniferous is the valley of the Mississippi Kiver from 
 near Davenport nearly to Cairo. 
 Let us stop at Burlington. 
 Here we find a bluff 175 feet 
 high. All the upper part be- 
 neath 25 feet of loose materials 
 is of limestone. The lower 
 portion, however, is composed 
 chiefly of beds of yellowish sand- 
 stone. These at the bottom are 
 quite shaly, and are know r n to 
 extend 65 feet beneath "the surface 
 of the river. A study of the fos- 
 sils in the two beds of limestone, 
 7 and 8, Figure 62, shows some 
 fossils not found anywhere else, 
 and teaches us that those lime- 
 stones ought to be reckoned as a 
 formation quite distinct from the 
 sandstones below. The upper 
 formations, made of limestones 7 
 and 8, we call the Carboniferous 
 
 T . ^ T , to 8, Carboniferous Limestone. 9, 
 
 Limestone Group. It amounts here D rift . R, Mean Height of River. 
 
 FIG. 62. SECTION OF THE 
 BLUFF AT BURLINGTON, 
 IOWA. LOWER CARBONIF- 
 EROUS ROCKS. (C. A.White.) 
 
 1 to 6, "Yellow Sandstones." 7 
 
154 GEOLOGICAL EXCURSIONS. 
 
 to seventy feet. The lower formation, made of the yel- 
 low sandstones, we designate the ' ' Waverly Group. " The 
 limestone is full of the fragments of " stone lilies." Some 
 beds, from two to four feet thick, are almost completely 
 formed of the little round disc-like segments of the stems 
 of those creatures. Many very beautiful and perfect 
 specimens have been collected here; and this has been a 
 favorite collecting ground for geologists for a good many 
 years. "We note some layers of limestone below these and 
 above the sandstones which are oolitic that is, they abound 
 in little round white globules about the size of homoeopathic 
 pills. But oolitic limestones are found also in formations 
 both older and younger. They, therefore, do not indicate 
 any particular u group " of rocks. If we inspect the sand- 
 'stones, we see that they are fine and rather soft and fri- 
 able ; but as to their fossils, there are no stone lilies. 
 Instead of them we find a great abundance of bivalve 
 shells. The oolitic limestone layers are like them in this 
 particular, and hence belong* in the same group. 
 
 This great difference in the fossils of two formations 
 shows one means by which we are able to distinguish for- 
 mations. We know, of course, without regard to the fos- 
 sils, that the sandstones are older than the limestones, 
 because they underlie the limestones. Also, if the upper 
 surface of the sandstones were eroded and irregular, we 
 should know that some important changes took place after 
 the deposition of the sandstones, before the deposition of 
 the limestones. This is what we see dividing the Eozoic 
 from the Cambrian rocks in the section shown in Figures 
 
TO BURLINGTON, IOWA. 155 
 
 54, 55, and 49. The same is seen at the top of the Lower 
 Magnesian Limestone in Figure 54. Still further, if the 
 lower strata should show a steeper dip than the upper, that 
 would prove that the lower, after their formation, were 
 tilted before the upper were laid down. In the same 
 Figure 54. you see that the dip of the Cambrian strata is 
 not conformable with the dip and crumpling of the Eozoic. 
 Unconformability is shown also in Figure 50, between the 
 systems L and H, and between the systems C and S. But 
 when strata like those at Burlington are entirely conform- 
 able, witliout any intervening erosions, then there is no 
 way to ascertain whether they were formed in periods quite 
 distinct or not, except by comparing the fossils in the two. 
 Yery often such comparison shows two formations distinct 
 when they are not only conformable and not separated by 
 erosion, but also, are both of the same kind of rock. This, 
 for instance, is the only means of separating the Hamilton 
 limestones in Ohio and Michigan from the Corniferous 
 Limestone immediately below. Even at Burlington, the 
 oolitic limestones belong in the lower group and not in the 
 upper. 
 
 By examining the Map you will notice that the Lower 
 Carboniferous covers a large area west of the Mississippi 
 Kiver. From northwestern Indiana, also, a belt passes 
 south to the Ohio River. Most of this is Carboniferous 
 Limestone. At Crawfordsville, in Indiana, is another 
 locality wonderfully rich in stone lilies. A large part of 
 central Kentucky is underlaid by this limestone. The 
 celebrated Mammoth Cave is formed in it. This cave was 
 
156 GEOLOGICAL EXCURSIONS. 
 
 once merely a fissure in the limestone. "Water circulated 
 through the fissure, and by degrees made it larger. This 
 was done partly by wearing the rock, but chiefly by dis- 
 solving it. So, in the course of time, the fissure grew to 
 a cavern several miles long, with dozens of branches and 
 tortuous passages, and ceilings in some places a hundred 
 feet high, and glistening by torch-light with thousands of 
 crystals. This formation abounds in caves in southern 
 Kentucky. Wyandotte cave, in southern Indiana, is also 
 in it. 
 
 You must have heard of the "knobs" and the u knob 
 regions " of Kentucky and Tennessee. These are regions 
 underlaid by the Carboniferous Limestone. But the same 
 fissured condition of the rock which has led to its wasting 
 away in caverns underground has here led to similar, but 
 greater, wasting above ground ; and so the whole surface 
 is gashed and gullied in every direction by running waters 
 some permanent, and some merely storm waters and 
 the portions un wasted by the gullies stand out as rock- 
 covered knobs. The unequal wasting is due partly to much 
 silica in portions of the limestone. 
 
 If we follow these Lower Carboniferous Limestones from 
 northern Alabama along the east side of the Devonian 
 toward northwestern and northern Pennsylvania,, we find 
 the limestone giving out. In place of limestone are soft 
 red shales with some sandstones. So the upper group of 
 the Lower Carboniferous begins to look somewhat like the 
 lower, or Waverly Group in the Mississippi Yalley. 
 
 In Michigan you see the Lower Carboniferous forming 
 
TO BURLINGTON, IOWA. 157 
 
 a circular belt around the border of the Lower Peninsula. 
 What answers to the Carboniferous Limestone is, of course, 
 the inner portion of this belt. But the limestone proper 
 is only 70 feet thick. It appears that the lower portion 
 of this group consists of quite a different sort of rocks. 
 They are shales, clays and gypsum, with a great amount 
 of brine. This brine and gypsum deposit is not found in 
 any other state. But it is found in New Brunswick and 
 Nova Scotia. Now how do we know this Michigan Salt 
 Group is really a part of the Carboniferous Limestone 
 Group ? Simply because we find in it the same species 
 of fossils. The gypsum is extensively worked near Grand 
 Eapids, and also, on the opposite side of the state, at Ala- 
 baster, on the north side of Saginaw Bay. The brine 
 settles down into the sandstones of the Waverly Group 
 and saturates them. Most of the salt wells of the Saginaw 
 valley are supplied by borings which extend down into 
 that sandstone. 
 
 I suppose you have seen the beautiful blue and gray 
 freestones used for building purposes in Cleveland, Toledo, 
 Detroit and other cities of the West. A freestone is simply 
 a sandstone which is soft enough to be easily worked by 
 the stone cutter. This beautiful stone is the u Waverly 
 sandstone," and gets its name from Waverly, in southern 
 Ohio. The best Ohio quarries, however, are at Berea, and 
 near Cleveland. The same stone, and equally valuable, is 
 quarried also in Michigan, in Huron county, on the shore 
 between Saginaw Bay and Lake Huron. The place is 
 called Grindstone City, because the world-famous "Huron 
 
158 GEOLOGICAL EXCURSIONS. 
 
 grindstones" are made there. Similar grindstones are 
 made at Berea. Now this fine stone is only an eastward 
 continuation of the yellow sandstones which we saw at 
 Burlington. They are, indeed, yellow and red in southern 
 Michigan, especially in Hillsdale county. Without doubt 
 some of the olive sandstones of northwestern Pennsylvania 
 belong to this group, if even some similar sandstones in 
 southwestern New York are not the same. 
 
 In eastern Pennsylvania the Waverly strata have be- 
 come coarse, grayish conglomerates and sandstones, with 
 red sandstones beneath. The red sandstones are generally 
 thought to belong in the Devonian, and to constitute a 
 different group, called the Catskill Group; but I feel doubt- 
 ful about the correctness of this opinion. If the Catskill 
 and Waverly belong to the same group, then the name 
 which we must apply to it is Catskill, for that name was 
 first proposed. These red Catskill sandstones extend 
 northward, and form a large part of the Catskill Moun- 
 tains. 
 
 In some parts of Pennsylvania and Virginia the lower 
 group contains beds of coal, forming what is sometimes 
 called False Coal Measures. In eastern Kentucky and 
 Tennessee, at the top of the Lower Carboniferous, are 
 found thick beds of shale containing valuable deposits of 
 coal ; and these are also sometimes called False Coal 
 Measures. They are also called subconglomerate measures. 
 
 So we have in the Lower Carboniferous System two 
 
 groups of strata: 
 
 ( Carboniferous Limestone Group. 
 LOWER CARBONIFEROUS SYSTEM j Waverly Group> 
 
TO BURLINGTON, IOWA. 159 
 
 EXERCISES. 
 
 Mention places in Illinois which are on the Lower Carbonifer- 
 ous. Mention places in the knob region of Kentucky. Which 
 way is the dip of the Carboniferous Limestone at St. Louis? 
 Which way at Grand Rapids, Michigan ? Which way on Sagi- 
 naw Bay? Does the Carboniferous Limestone pass under Cin- 
 cinnati? Which is next the Devonian in Ohio, the Waverly 
 Group or the Carboniferous Limestone Group? Which way 
 does the Lower Carboniferous dip in Indiana ? Which way does 
 it dip in northern Pennsylvania ? Is there any Lower Carbonif- 
 erous in New York? If so, would you expect it to be a limestone 
 or a sandstone ? If you start from Louisville to sail down the 
 Ohio River, do you approach newer or older rocks ? If you start 
 from Wheeling down the Ohio, do you reach older or newer 
 rocks ? Why is this difference on the upper and lower portions 
 of the Ohio? Where is the dividing line? What are the newest 
 rocks found in the province of Ontario ? What formations does 
 Lake Michigan overlie? Does the axis of the lake cross the 
 boundaries of the formations or run parallel with them ? Point 
 out other lakes or bays which also conform in trend to the strikes 
 of the formations under them and around them. Point out some 
 lakes or bays which trend across the boundaries of the forma- 
 tions. How is it with the long lakes in central New York? If 
 a deep artesian well is bored at Grand Haven, what formation 
 will be passed through ? Would the Potsdam Sandstone be 
 reached ? Would fresh water rise to the surface ? 
 
160 
 
 GEOLOGICAL EXCURSIONS. 
 
 EXCURSION" XXYII. To the Coal Mines. 
 The Coal Measures. 
 
 It is immaterial what great coal-mining region we visit. 
 We may go to Wilkesbarre, Pennsylvania, to Brazil, Indi- 
 ana, to La Salle or Jonesboro, Illinois, or to any of the coal 
 regions in Kansas, Missouri, Ohio, Kentucky, Tennessee or 
 Alabama. We shall see huge piles of black shale rubbish 
 lying around, and great heaps of coal ready for shipment, 
 and great numbers of small cars running on tramways 
 which lead through dark yawning openings into the recesses 
 of the earth. We shall see men and mules going under- 
 ground for long distances, and if we follow them, we shall 
 find extensive passage ways excavated, like the streets of a 
 city, sometimes aggregating several miles in length. The 
 plan in mining is to get upon a coal bed, and then work 
 it out in all directions. Sometimes the coal is found out- 
 cropping on a hillside, as in Figure 63, and then it is only 
 
 FIG. 63. DRIFTING IN ON A COAL BED. a, Mouth of the Drift. 
 
 necessary to "drift" in. There is generally water under 
 ground, and hence the drift should enter at a place where a 
 slight ascent will be necessary in following the bed. The 
 
TO THE COAL MIKES. 
 
 161 
 
 water then flows toward the entrance to the mine, and 
 escapes. Sometimes mines are opened in places where the 
 coal beds are far beneath the surface. Then a "shaft" is 
 sunk, as is shown in Figure 64 at S, and when a coal bed, 
 
 Surface 
 
 FIG. 64. GENERAL SECTION IN THE UPPER COAL REGIONS OF PENNSYLVANIA. 
 
 W, Waynesburg Seam. P, Pittsburgh Seam. S, a Mining Shaft, a a, Down Cast. 
 
 6, Up Cast. w, Sump. 
 
 W, is reached, excavations are made on both sides. Often 
 the same shaft is sunk to a second coal bed, P, and occa- 
 sionally even to a third one. The passages or gangways 
 are generally extended in straight lines as far as the coal 
 continues satisfactory, and other passages are opened at 
 right angles with these. On each side of these gangways 
 large rooms are excavated, but with walls of coal left stand- 
 
162 
 
 GEOLOGICAL EXCURSIONS. 
 
 ing between them for the support of the roof. In the course 
 of time all the coal is mined out, except large columns and 
 walls left for support. In some mines these are also finally 
 removed. 
 
 Illbt 
 
 B A 
 
 FIG. 65. PLAN OF THE MINES OF THE BLOSSBURG COAL COMPANY AT ARNOT, 
 PA. Scale, 400 ft. to the inch. A, the Main Gangway. B, the Return 
 Air Course and Ventilating Shaft. The light portions represent the 
 ground worked over to 1872. (After Macfarlane.) 
 
TO THE COAL MIKES. 163 
 
 In Figure 65 is presented a plan of the workings in the 
 Blossburg mines of Pennsylvania in 1872. This is a por- 
 tion of a coal bed, about 1,500 feet broad and 1,900 feet 
 long, showing where the gangways have been dug out for 
 travel and for ventilation, and also the rooms or u breasts" 
 from which the coal has been taken. It shows also the 
 large amount of coal left for supporting the roof. These 
 supports will ultimately be taken out also. In some regions 
 the roof rock is so fragile that the gangways have to be 
 timbered. Even then, the enormous weight sometimes 
 crushes the supports, and occasional disasters happen in 
 this way. The same plan of mining is pursued, whether 
 the mine is approached by an adit, as shown in Figure 63, 
 or by a shaft, as shown in Figure 64. 
 
 The strata which make up the so-called Coal Measures 
 consist largely of shales and sandstones. Besides these we 
 find beds of clay, and generally some limestones. All this 
 is shown in Figure 64. Sometimes the whole thickness of 
 the Coal Measures is only one or two hundred feet; and 
 then we find but one or two beds of coal thick enough to 
 pay for mining. In other regions the Coal Measures are 
 several hundred feet in thickness, and then they contain, 
 probably, three or four workable beds. Besides the work- 
 able beds, there are many too thin to pay for working. 
 When we take a piece of the coal shales and split it open, 
 we are apt to find the surfaces beautifully marked by the 
 impressions of ferns. All the delicate outlines and vein- 
 ings are as perfect as if pressed in a modern herbarium. 
 In Figure 66 are shown some fern remains from Illinois. 
 
164 
 
 GEOLOGICAL EXCURSIONS. 
 
 Sometimes we find fern impressions on the coal itself. In 
 the shales we find also the flattened stems of the trees which 
 bore the fern fronds arid other foliage. Sometimes, in the 
 
 FIG. 66. IMPRESSIONS OF FERNS ON COAL SHALE. Alethopteris Mazoniana, 
 
 Lesquereux. 
 a, Enlarged Pinnules showing the Nervation. 
 
 sandstones, the tree trunks remain unflattened, and even 
 stand vertically in the midst of the rock. It is curious to 
 think that these tree trunks may exist several hundred feet 
 under ground. There they stand where they grew, and the 
 sand has been accumulated around them. Figure 67 gives 
 a view of one of these trees restored that is, completed as 
 we think it originally appeared. By the side are some por- 
 tions represented on a larger scale. Figure 68 is a restora- 
 
TO THE COAL MINES. 
 
 165 
 
 tion of another sort of tree whose remains are very abundant 
 in the Coal Measures. 
 
 In the western states the strata of the Coal Measures are 
 
 FIG. 67. LEPIDODENDRON. A TREE 
 OF COAL MEASURE TIMES. SEPA- 
 RATE PARTS ON A LARGER SCALE. 
 (Zittel.) 
 
 FIG. 68. SIGILLARIA. A TREE OF 
 COAL MEASURE TIMES. SEPA- 
 RATE PARTS ON A LARGER 
 SCALE. (Zittel.) 
 
 pretty evenly laid down. Figure 69 presents a general view 
 of the coal-bearing strata of Illinois. You see the shales, 
 
 FIG. 69. SECTION IN THE COAL MEASURES OF ILLINOIS. 
 
166 
 
 GEOLOGICAL EXCURSIONS. 
 
 sandstones and coal beds are flat and nearly horizontal, and 
 parallel with each other. But now look at this section 
 through the Coal Measures of Pennsylvania, shown in 
 Figure TO. The different strata are nearly parallel with each 
 
 FIG. 70. SECTION IN THE APPALACHIANS Six MILES IN LENGTH, SHOWING 
 PLICATIONS OF THE COAL MEASURES AND OLDER STRATA. (Rogers.) 
 
 other, but notice how they are all bent and broken. This 
 is also remarkably shown in Figure 26. Sometimes at the 
 place where a break occurs, we find the strata let down on 
 one side below the level of the stratum on the other side 
 of the break. This is called a Fault. The downthrow 
 may be any distance. In some cases it amounts to twenty 
 thousand feet, and even more. Faults occur in all forma- 
 tions especially those as old as the Coal or older. Here, 
 in Figure 71, is a series of remarkable faultings in the 
 
 Faults Jrvm 600 to 1, 700 feet 
 
 WASATCH PLATEAU 
 11, 000 ft. high 
 
 W 
 
 c b c c b 
 
 FIG. 71. SECTION EAST AND WEST IN CENTRAL UTAH, SHOWING NUMEROUS 
 
 FAULTS. (Button.) 
 a, Triassic. ft, Jurassic, c, Cretaceous, d, Laramie. 0, /, Tertiary. 
 
 Mesozoic and Caenozoic strata of central Utah. You will 
 understand that a fault results from an enormous break 
 through the whole thickness of the solid rocks. What an 
 
TO THE COAL MINES. 167 
 
 enormous power is required to break a pile of strata a mile 
 or more thick ! 
 
 The lowest stratum of the proper Coal Measures is 
 almost everywhere a conglomerate or pebbly sandstone, 
 called the Millstone Grit. It is often so thick as to consist 
 of several strata. It contains a good many remains of 
 sticks, roots and foliage. Beneath this there are generally 
 some shales, and in Kentucky and Tennessee excellent beds 
 of coal. The Coal Measures, when traced westward, are 
 found to contain less coal and more limestone. But higher 
 up, we find in our western territories, as well as in Europe, 
 some strata which much resemble the Coal Measures. But 
 the fossil remains are diiferent, and these strata are set 
 clown as forming the Permian Group. 
 
 So the Upper Carboniferous System is composed of two 
 groups : 
 
 { Permian Group. 
 UPPER CARBONIFEROUS SYSTEM \ _, . , r 
 
 | Coal Measures. 
 
 EXERCISES. 
 
 Have you ever seen a coal mine? If so, what did you 
 consider the most interesting thing about it ? If not, what 
 would you expect to be most interested in? Where does the 
 water come from which we generally find in coal mines ? In 
 what part of the country are the strata of the Coal Measures 
 most folded and disturbed? How would the coal beds lie in 
 Michigan ? Are there any coal beds in any New England state ? 
 Do you notice any connection between a disturbed condition of 
 the strata and a mountainous condition of the surface ? Name 
 the states east of the Mississippi through which the mountains 
 extend. Would you expect the coal strata to be folded in all 
 those states? Would they be equally folded in western Penn- 
 
168 GEOLOGICAL EXCURSIONS. 
 
 sylvania ? Is there any mineral coal in New York ? If you 
 should see any person digging for coal in that state, what would 
 you think of his knowledge of geology? Name any other 
 states which contain no coal. What was the coal formed from ? 
 Did those coal plants grow on land or in the water ? Where was 
 the land when they were growing ? Was the Millstone Grit 
 formed on the land ? Can you think how tree trunks came to 
 stand erect in the midst of sandstone? Where might New 
 Orleans send to get coal by water? Which must send farthest 
 for coal, New Orleans or Mobile ? Are there any building stones 
 in Alabama? 
 
 EXCUKSION XXVIII. To Selma, Alabama. 
 The Mesozoic Rocks. 
 
 If you cast your eyes once more on our little geological 
 map you will notice the city of Selma located on the Ala- 
 bama Kiver in the midst of a broad belt of Cretaceous rocks 
 stretching east and west across the state of Alabama. A 
 little to the north are Silurian and Cambrian rocks, and, to 
 the south of this belt, the Tertiary strata stretch to the 
 Gulf of Mexico. At Selma the Alabama River has exca- 
 vated a deep channel through a whitish chalky limestone 
 known as the " rotten limestone." The city stands eighty 
 feet above the river at low water. It is supplied with fresh 
 water by a large number of artesian wells. 
 
 The "rotten limestone" is near the upper part of the 
 Cretaceous System, and is about 300 feet thick. It dips 
 southward beneath the Tertiary rocks. Under this lime- 
 stone is a vast series of sandstones, sands and shales. These 
 outcrop at various distances to the north of Selrna all 
 
TO SELMA, ALABAMA. 
 
 169 
 
 dipping southward under ^| 
 the "rotten limestone." 
 Farther west, this belt of & 5 ^ 
 
 O 
 
 Cretaceous rocks bends 1 1 ^ 
 
 = "' * 
 northward, and the dips g ^ 'j 
 
 are first southwest, and g <; | 
 farther north they are |- 1 
 
 ^ o 
 
 west. You see this Cre- gl| 
 taceous belt extends even 5 ^ 
 to the mouth of the Ohio f 1 | 
 
 on p >> 
 
 River. In Alabama, the ? | 
 
 lower strata outcrop at '^ | * 
 
 higher levels than the 1 3 
 
 upper strata. The rains q 
 
 which fall on these lower | | 
 
 p o .3 
 
 sandy strata are carried | ^ w 
 
 down under Selma and g. M g 
 
 M 52 
 all other localities on the J_ | c 
 
 "rotten limestone." So Sjq 
 when a well is bored || | 
 at these localities deep 
 enough to reacli the deep 
 water-bearing strata, the I | ,$ * 
 water rises to the surface. 
 Now here is a section 
 naming south from Tus- 
 caloosa to St. Stephens 
 on the Tombigbee River 
 and thence to Mobile. 
 
 |M^ 
 
 Iff) Coal'Mines 
 i TUSCALOOSA 
 
 Foster's Ferry 
 
 Carthage 
 
 I Havana 
 Bridgeville 
 
 / 
 
 k Clinton 
 EUTAW 
 'Finch's Ferry 
 
 Hamburg 
 
 ICHOCT AW BLUFF 
 
 A'eivbern 
 
 SELMA 
 
 J Pleasant Ridge 
 * Bogue Cliillo Creek 
 
 PRAIRIE BLUFF 
 
 ' Camden 
 
 'Black's Bluff 
 ' Bell's Landing 
 
 CLAIBORNE 
 
 'stave Creek 
 iSuggsville 
 1 Jackson 
 
 ! MOBILE 
 Mobile Bay 
 
170 GEOLOGICAL EXCURSIONS. 
 
 Numerous localities are named on it, but many of them do 
 not concern us at present. You see plainly how all the 
 strata dip southward. Here are several artesian wells indi- 
 cated. Among them are two at Selrna. Notice how they 
 extend into the lower Cretaceous formations, which contain 
 sandy strata. Here then, you have a good explanation of 
 artesian wells. Notice the elevation of Eutaw. It is 
 higher than the place of outcrop of any of the underlying 
 Cretaceous rocks ; therefore the water does not rise to the 
 surface, though the well is very deep. There are hundreds 
 of artesian wells bored through the rotten limestone in Ala- 
 bama and Mississippi. In some of them the water contains 
 much sulphur gas (^hydrogen sulphide), and others yield salt 
 water. 
 
 Now, if you glance westward on the map, you notice a 
 vast area in Texas underlaid by Cretaceous strata. Then, 
 farther north is a still larger area stretching through Kansas, 
 Nebraska, Iowa, Minnesota and Dakota. All these strata, 
 like those in Alabama, are comparatively unconsolidated. 
 There are, indeed, some very compact sandstones, but the 
 rocks are, throughout, very much more easily broken or 
 crushed than the rocks of the Palaeozoic formations. Many 
 of the strata, especially the limestones, abound in fossil 
 shells ; and there are many remains of fishes and reptiles. 
 In Europe, the Cretaceous System contains the great Chalk 
 formation. It is probable the rotten limestone of the 
 Southern States corresponds to the European Chalk. 
 
 The Cretaceous is the uppermost system of the Mesozoic : 
 but you have seen from the diagram, Figure 72, as well as 
 
TO SELMA, ALABAMA. 171 
 
 from the Map, that in Alabama, no other Mesozoic forma- 
 tion cornes between the Cretaceous and the Coal Measures, 
 which are Palaeozoic. Probably, if we could go down and 
 explore the rocks under the Cretaceous, all the way to the 
 Gulf of Mexico, we might find the other Mesozoic Systems 
 actually existing. In Texas, you will see from the Geologi- 
 cal Map, is a system called Jura- Trias, which covers a large 
 area. These strata pass under the Cretaceous in Texas and 
 Kansas. They consist mostly of shales and sandstones. 
 This Jura-Trias System is really composed of two systems, 
 the Jurassic and Triassic. In some regions, in consequence 
 of the absence of fossils, it is impossible to locate the 
 dividing line between them, or to say positively whether a 
 formation is really Jurassic or Triassic. That is the reason 
 why we say Jura-Trias. But in the far Northwest and 
 West, the two systems are more readily separated, and we 
 find that the Jurassic contains nearly five thousand feet of 
 shales and sandstones, and one thousand feet of limestone. 
 In Montana these limestones contain many bones and teeth 
 of monstrous extinct reptiles ; but we must postpone the 
 study of these for a more advanced course. The Triassic 
 in the Far West contains over eleven thousand feet of shales 
 and sandstones many of the latter being very hard and 
 quartzose and about 4,500 feet of limestone. 
 
 In the valley of the Connecticut River, is a red sandstone 
 formation called Jura-Trias, which is extensively quarried 
 for building stones. At Portland, Connecticut, are quarries 
 from which stone is taken to New York to be built into the 
 so-called brown-stone fronts. On the slabs of this sandstone 
 
172 GEOLOGICAL EXCURSIONS. 
 
 may be seen many footprints of ancient reptiles. Some of 
 these were three-toed, like birds, and walked on two feet like 
 birds. The same sandstone extends to New Haven, and 
 also appears on the west of the Hudson River in New Jersey. 
 In fact, there are small patches of it at various localities in 
 North Carolina and Virginia resting horizontally in the 
 depressions in the old Eozoic rocks. Near Richmond is a 
 valuable bituminous coal deposit which we have to designate 
 Jura-Trias. 
 
 Thus, the Mesozoic Great System is made up of three 
 Systems, as follows (see also "The Geological Column," 
 Excursion XVIII) : 
 
 f Cretaceous System. 
 MESOZOIC GREAT SYSTEM j Jurassic System, > j^^rp,^ 
 
 '^Triassic System, ) 
 
 EXERCISES. 
 
 Do the Mesozoic strata of the Atlantic and Gulf regions dip 
 toward the ocean or away from it ? Explain why this is so. 
 Do you imagine Mesozoic strata extend under the ocean ? In 
 Kansas, which way do the Cretaceous strata dip ? Did they ever 
 dip toward a large body of water? In Dakota which way do 
 Cretaceous strata dip ? On the east side of the Black Hills, 
 which way do they dip ? Suppose you bore an artesian well at 
 the " big bend " of the Missouri River, would you ever strike 
 Eozoic rocks ? What Palaeozoic rocks are exposed nearest to 
 that point ? Are they higher or lower than the surface at the 
 " big bend " ? Would your artesian well at the " big bend " 
 bring water to the surface ? Would an artesian boring succeed 
 at Charleston, S. C. ? Mention other places on the Mesozoic 
 at which artesian wells might succeed ? Are any human remains 
 found in the Cretaceous strata ? Are any reptilian remains found 
 in the Silurian strata ? Where was the seashore in Alabama 
 
TO CLAIBOR1S T E, ALABAMA. 173 
 
 when the Cretaceous sediments were accumulating ? Follow the 
 shore line through other states east and west. Where was the 
 greater part of the American land at the beginning of Mesozoic 
 Time ? Do you think there were rivers and lakes on that land ? 
 Into what water did the Ohio River then empty ? Where was 
 then the mouth of the Mississippi? Mention some rivers which 
 did not exist in Mesozoic Time 
 
 EXCURSION XXIX. To Clailorne, Alabama. 
 The Tertiary Formations. 
 
 I took you to Alabama for a good view of Mesozoic rocks, 
 Now we cannot do better than remain here to examine the 
 Tertiary rocks. These, in order, come next above the 
 Cretaceous, and we can use the same section, Figure T2, as 
 I gave you on the last Excursion. 
 
 Claiborne, on the Alabama River, is one of the most in- 
 teresting geological localities in the country. The town is 
 built on a bluff 180 feet above the river, and here is one of 
 those wonderful southern chutes for sliding cotton down to 
 the decks of steamboats. The upper part of the bluff is 
 nearly perpendicular, and consists of chalky limestone known 
 as the "White Limestone." The middle portion of the bluff 
 is formed of a loose, rusty-colored sand which crumbles down 
 and forms a slope overgrown with vegetation. The lower 
 part of the bluff consists of bedded, compact, sandy clay, 
 containing large oyster shells, of a different species from the 
 modern oyster. The sandy beds are densely packed with 
 fossil shells in a fine state of preservation. They also con- 
 tain the teeth and vertebrae of ancient sharks. The white 
 
174 GEOLOGICAL EXCURSIONS. 
 
 limestone seen at the top stretches east and west across the 
 state. It forms the high, white bluff at St. Stephens on the 
 Tombigbee River. It contains many fossil shells, and 
 occasionally the bones of a whale-like dweller in the sea, 
 which was long and slender like the fabled sea-serpent. 
 Many years ago a pretty complete skeleton of this extinct 
 monster was dug out of the rock in Clarke county. These 
 strata all belong to the Eocene, or oldest division of the 
 Tertiary. 
 
 You will notice particularly three things about these Terti- 
 ary strata: 1. They are not hard rocks like those of the 
 Palaeozoic formations. They are not even hard as the Cre- 
 taceous strata. 2. The fossils are much more like the 
 remains of beings which live in human times, and they come 
 out of the strata in a more perfect condition. 3. The Terti- 
 ary strata lie next the seacoast. 
 
 This last point is made clear when you understand that 
 the Tertiary strata extend west from Alabama through 
 Mississippi, Louisiana and Texas, and east through all the 
 Gulf and Atlantic states to New Jersey. Look on our little 
 map again and see what an immense country is underlaid by 
 Tertiary strata in the valley of the Mississippi. Then 
 toward the north notice that half of New Jersey is Tertiary. 
 Long Island is also thought to be underlaid by Tertiary. It 
 certainly has the level and sandy appearance of a Tertiary 
 region. Also the two islands, Nantucket and Martha's 
 Vineyard are Tertiary. All these islands are so covered by 
 sand that it is almost impossible to examine the underlying 
 strata. But the southwest point of Martha's Vineyard rises 
 
TO CLAIBOK^E, ALABAMA. 175 
 
 high above the water, and brings plainly to view the strata 
 which form the body of the islands. This promontory is 
 called Gay Head. It is a favorite excursion for the summer 
 sojourners on Martha's Yineyard to make a steamboat trip 
 to Gay Head. The strata here are mostly clay, and they 
 are gaily diversified in color. Some strata are blue or white, 
 others are red or yellow or black ; and all are crumpled in 
 fantastic fashion, and worn in almost vertical cliffs by the 
 action of the sea and the weather. We know these are 
 Tertiary beds because we find in them sharks' teeth and 
 whales' vertebrae, and a few sea shells which elsewhere are 
 found in the Miocene Tertiary. 
 
 Now notice the great Tertiary expanse shown on the 
 western part of our map. There are, indeed, two of them. 
 If this map embraced the whole region to the Pacific Ocean, 
 we should see several other Tertiary areas. Now, when 
 you remember that the Tertiary strata are the last laid down, 
 and must, therefore, overlie all the others, you can under- 
 stand that while the sediments were forming which have 
 hardened into these patches of Tertiary strata, there must 
 have existed seas or lakes in the interior of the continent ; 
 and you can understand that these Tertiary areas are the 
 sites of dried up seas or lakes. Just so the Atlantic and 
 Gulf-border Tertiary marks the site of the ancient ocean, 
 which in this case, has not dried up, but shrunken away. 
 The retreat of the ocean, however, has probably been 
 caused more by an uplift of the land than by a diminution 
 of the ocean's water ; and so the interior seas were partly 
 drained by the same elevation of the land. 
 
176 GEOLOGICAL EXCURSIONS. 
 
 When those interior seas existed, the land was populated 
 by many species of quadrupeds which, in the earlier times, 
 were very different from the quadrupeds which now live. 
 In later Tertiary times, other species lived which showed a 
 growing approach toward our modern animals. But it is 
 not best to try to learn much about those strange extinct 
 animals until you have advanced farther. 
 
 The sediments which accumulated in the bottoms of those 
 seas are rocks now. They consist mostly of clays, sands 
 and incoherent sandstones. They are made of stuff washed 
 in from the surrounding land. Who can say how much of 
 the land was worn out to furnish the material for the Terti- 
 ary strata ? So, in every age, the work of previous ages has 
 wasted away, and the old materials have been rebuilt in the 
 monuments of the passing time. 
 
 But it is long sinfce these ancient seas were thus partly 
 filled and completely drained. The strata then new-made 
 have in turn become the broken and decaying formations of 
 the age now passing. The rains and the streams have ever 
 since been doing the same kind of work upon these last 
 formed strata, as they did in the older time to get the stuff 
 to make these strata. These rocks are so incoherent that 
 nature's erosive agencies have wrought vast destruction 
 among them. In some regions immense basins have been 
 dug out right in the midst of a Tertiary region, and the 
 edges of the undestroyed strata expose themselves all 
 around the border of the basin. Then the rains running 
 down the slopes have worn them into forms resembling 
 columns and pinnacles. These regions are generally sterile, 
 
TO CLAIBORXE, ALABAMA. 177 
 
 and the first explorers of them named them "bad lands." 
 
 FIG. 73. VIEW IN THE BAD LANDS OF NEW MEXICO. (Cope.) 
 
 Here in Figure 73 is a view of some isolated columns stand- 
 ing in one of the " bad lands " of New Mexico. 
 
 EXERCISES. 
 
 What states are completely covered by Tertiary ? What ones 
 are more than half covered ? What ones containing Tertiary are 
 less than half covered? What states afford no good quarry 
 stones ? What are the nearest good building stones for use in 
 Florida? What is that singular material sometimes used for 
 building at St. Augustine, Florida ? Would the " White Lime- 
 stone " of Alabama make a good building stone ? Could New 
 Orleans obtain granite by the Mississippi River ? Where would 
 that city send to get granite by ocean navigation ? Where does 
 New Orleans obtain lime ? Can you think of any mineral pro- 
 ductions more convenient to Mobile than to Boston ? What 
 formations were worn down to furnish Tertiary material in South 
 Carolina? Which way did the rivers run in South Carolina 
 when the Tertiary beds were forming ? State what rivers along 
 the Atlantic coast existed in whole or in part during Tertiary 
 time. State what rivers along the Gulf coast did not exist in 
 Tertiary time. Trace the shore of the Gulf and Atlantic during 
 Tertiary time. What states did not then exist as dry land ? 
 
178 GEOLOGICAL EXCURSIONS. 
 
 What states were then partly sea bottom ? Is it supposable that 
 the Atlantic Tertiary border ever extended beyond New Jersey 
 so as to form a border to New England ? If so, what has become 
 of those Tertiary deposits ? Does the Tertiary on Martha's Vine- 
 yard throw any light on this question ? Why do we find no 
 Tertiary in Ohio ? Should there not be Tertiary around the 
 border of the " Great Lakes," as well as along the Atlantic 
 border? Where was the mouth of the Mississippi in Tertiary 
 time? Why is it so much further south at present? What 
 rivers flow across the great Tertiary areas of the Northwest ? 
 Did those rivers exist in Tertiary time? Did any of them partly 
 exist ? Did any water escape from the Tertiary inland seas into 
 the Atlantic Ocean ? Point out the course it may have pursued. 
 Are there any mountains in the Tertiary regions of the United 
 States ? Why are Tertiary rocks less hard than Palaeozoic rocks? 
 
 EXCUBSION XXX. To the River Valley. 
 Quaternary Formations. 
 
 The great Drift formation is almost everywhere present. 
 We began with a study of the rocks of the Drift, and now, 
 having learned something of the deeper-lying formations, 
 we come back to the Drift, to study it in a more general 
 way. Most other formations began as sediments deposited 
 in bodies of water; the Drift generally could not have had 
 such an origin, though moving water undoubtedly has done 
 much in the arrangement of the materials. 
 
 Now look around us. Every field is covered with a 
 mass of subsoil material. In some cases we know that it 
 is only a few feet to hard rocks below ; but in most places 
 we are sure it is many feet. All our cellars and wells are 
 
TO THE RIVER VALLEY. 179 
 
 dug in this unconsolidated subsoil deposit. In some places 
 we find it quite clayey ; in others it is sandy ; in some 
 others it is gravelly. Almost everywhere, if we dig deep, 
 we shall find sand and gravel and clay. Almost everywhere, 
 also, we shall see cobble stones and larger boulders lying 
 on the surface or buried beneath it. Fine examples are 
 shown in the cuts, Figures 3 and 2, while the large boulder 
 of Figure 1 may here be recalled to mind. These deposits 
 belong to the Drift formation. The kinds of rocks and 
 minerals to be found in the boulders we have already 
 studied sufficiently for the present. 
 
 Suppose we travel from Canada to the Gulf of Mexico, 
 and study the Drift all the way. We shall observe two 
 particulars in which the northern Drift differs from the 
 southern. 1. The northern Drift abounds in boulders ; the 
 southern Drift has none. 2. The northern Drift ends 
 abruptly downward, and rests on a smooth hard surface 
 of bed-rock, as a rule ; the southern Drift passes by gradual 
 transition from its sandy or gravelly condition to a decaying 
 condition of the underlying strata. That is, in the south, 
 the lower part of the surface deposits seems to have resulted 
 from the decay of the underlying strata, and one can trace 
 the stratification upward from the unaltered rock into the 
 overlying, unconsolidated beds. These lower portions have 
 ~been formed where they lie ; only the higher, gravelly por- 
 tions have been brought from some other region. The 
 lower portions, therefore, are not .properly any part of 
 the Drift. The upper, transported sand and gravel are 
 much less abundant than the proper Drift of the north ; 
 
180 
 
 GEOLOGICAL EXCUKSIOKS. 
 
 but yet, in some localities are one or two hundred feet 
 deep. 
 
 Now look at the bottom of the Drift in the northern 
 states. The underlying strata are not seen partially decayed 
 and passing upward into the condition of soft loam. They 
 show a well defined upper surface. It is a hard surface. 
 If ever there were any decayed portions, they have been 
 removed. But the most striking fact is the smoothed con- 
 dition of this rock surface. It looks as if it had been planed 
 down by some mighty power. It has not only been levelled 
 and smoothed; it lias been scratched and grooved along 
 straight lines running in a general north and south direc- 
 tion. There is no rock so hard as to have resisted this 
 action. In New England and in the Canadian regions we 
 
 FIG. 74. A STRIATED DOME OF QUARTZITE, FRAZER BAY, LAKE HURON. 
 (Photograph furnished by Dr. E. Andrews.) 
 
TO THE RIVER VALLEY. 181 
 
 find the most flinty rocks as perfectly smoothed and striated 
 as the softer limestones of other regions. Dr. E. Andrews, 
 of Chicago, has photographed an interesting example, which 
 you see reproduced in Figure 74. A dome-like protrusion 
 of quartzite, rising above the level of the water at Frazer 
 Bay, north of Lake Huron, has been planed and striated 
 by some tremendous power. The smoothed rock can be 
 traced, extending down under the water a great distance. 
 Such phenomena are common along the Eozoic shores of 
 the upper lakes. Another striking example may be seen 
 at Marquette. These facts are very impressive and very 
 important. They seem to be connected with the history 
 of the Drift. 
 
 In the Northern States we can everwhere notice in the 
 Drift a distinction of another kind. Nearly all the surface 
 portion of the Drift is partially stratified. This is shown 
 in Figures 5 and 6. This confused stratification must have 
 resulted from the action of water in motion. The deeper 
 portions of the Drift are unstratified. They consist of a 
 great mass of blue clay with imbedded boulders. The semi- 
 stratified portion is called Modified Drift, and the deeper, 
 unstratified portion is sometimes called Till. 
 
 All around the shores of the Great Lakes we find still 
 another condition of the surface deposits. They are dis- 
 tinctly and evenly stratified, as if laid down in standing 
 water. They consist of fine sand and clay, without cobble- 
 stones or large boulders. These stratified deposits extend 
 inland from the lake shore far enough to attain an elevation 
 of one or two hundred feet above the lakes. There they 
 
182 GEOLOGICAL EXCURSIONS. 
 
 terminate, and the surface beyond consists of the usual 
 Modified Drift. It looks as if the water of the lakes had 
 once stood high enough to cover these low border deposits, 
 and had laid them down in the usual method of sedimenta- 
 tion. These beds, therefore, are not properly a part of the 
 Drift. The several strata descend gradually toward the 
 lake, and apparently pass under the lake. As their out- 
 crops are at higher levels than any part of the surface 
 nearer the lake, it happens that artesian wells are some- 
 times attained by boring into them. 
 
 When the lakes stood at the high levels indicated by 
 these lacustrine deposits, they formed gravel beaches around 
 their borders. Beaches were formed at various elevations 
 during the progress of the lowering of the lakes. These 
 beaches still exist, and may be traced around nearly all the 
 lake borders. We call them Lake Terraces. 
 
 Terraces also border many of our rivers. They seem 
 to have been formed when the rivers flowed at higher levels 
 than at present. Here, in Figure 75, is a section across a 
 
 FIG. 75. SECTION ACROSS A TERRACED RIVER VALLEY. 
 
 river valley, showing terraces at three different levels on 
 one side, and four different levels on the other. The main 
 valley is seen excavated in 4he underlying solid rocks. 
 Then, when the river flowed at the height ^yand e' f , it 
 
TO THE RIVER VALLEY. 183 
 
 formed the upper terrace. This may be one, two or three 
 hundred feet above the present river level. At a later 
 time, when the river level had subsided, it formed the 
 lower terraces c d and c' d f . The intermediate terrace /, 
 on one side, has been destroyed on the other side. At 
 the present time the river has shrunken so as only to till 
 the channel R, and when it overflows its banks, it throws 
 its sediment down on the flood plains a b and a' b f . 
 
 There must have been some powerful cause for the 
 former high level of the lakes and rivers. The rivers could 
 have been flooded by a former greater abundance of water. 
 The lake-levels would have been raised also, to a limited 
 extent, by the same cause ; but to raise the Great Lakes 
 one, two or three hundred feet, there must have been some 
 great barrier at the outlet of the lakes, which dammed the 
 waters. One barrier, I think, was at the termination of 
 the Niagara gorge, as shown in Figure 58, page 142. The 
 dotted lines there show the former level of the lakes. 
 
 If the Great Lakes have fallen as much as the high 
 terraces indicate, it is easy to understand that small lakes 
 may have been completely drained, or completely filled up 
 with sediments. Figure 20 shows this filling in progress. 
 This would take place during the same period when the 
 terraces were forming. 
 
 Some other conditions of the surface formations exist 
 in some regions, but these principal ones are all which we 
 need study at present. All these modified states of the 
 transported Drift materials have been called Champlain 
 
184 GEOLOGICAL EXCURSIONS. 
 
 Deposits, and the period of their formation, the Champlain 
 Period. 
 
 Now let us summarize the succession of surface mate- 
 rials, as far as described : 
 
 QUATERNARY FORMATIONS. 
 Unconsolidated Surface Materials. 
 Northern States. Southern States. 
 
 Terrace Formation, including Beds Terrace Formation [including 
 of Marl and Peat [also L5ss, Loss, Orange Sand, etc], 
 
 etc]. 
 Lacustrine Deposits. 
 
 Modified Drift, Modified Drift, 
 
 with Boulders. without Boulders. 
 
 Till. [No Till.] 
 
 Striations on Rock-surfaces. [No Striations on Rock-surfaces.] 
 
 [Decaying Strata removed.] Decaying Strata in place. 
 
 Unaltered Rocks. Unaltered Rocks. 
 
 EXERCISES. 
 
 How does the Drift formation differ from a Sandstone forma- 
 tion ? Is the Drift a proper sediment ? How is it unlike a sedi- 
 ment ? What has water had to do with this formation ? Was it 
 still water, or water in motion ? Did the action of this water 
 extend over the Southern States as well as the Northern ? Did 
 the action of this water affect the whole thickness of the Drift in 
 the Northern States? Why do you give this answer? Did the 
 action of the water affect the whole thickness of the Drift in the 
 Southern States? What portion of the Drift has been trans- 
 ported? Mention some kinds of rocks found in the Drift. Are 
 such rocks Mesozoic or Palaeozoic ? Do we have crystalline rocks 
 in the Mesozoic or Palaeozoic ? Do we have them in the Eozoic ? 
 Where may we find Eozoic rocks existing as the bed-rocks? 
 In what direction are the Eozoic rocks from the Middle States ? 
 From what direction, then, have our boulders been transported ? 
 Do the scratches on the rock surfaces under the Drift indicate 
 
TO SWITZERLAND. 185 
 
 transportation from the direction which you last mentioned ? 
 Is there any reason for concluding that our boulders have not 
 all come from New England ? Are there none but hard and 
 crystalline rocks north of the Middle States ? Why are there so 
 few sandstones and limestones among the boulders ? What sorts 
 of rocks would be slowly dissolved in the soil? Would that 
 result in a benefit or an injury to the soil ? Did the Connecticut 
 River exist before the Drift was laid down ? How did it compare 
 in size with the present Connecticut? Can you think of any 
 evidence that the land once extended farther south at New York 
 than it does at present? Look on the Geological Map, and 
 notice the dotted lines off the mouth of the Hudson River, and 
 try to think what they signify. Why are they so notched north- 
 ward? If the Great Lakes ever stood 200 feet higher than at 
 present, what are some of the cities whose sites were covered by 
 the water? Could the lakes then have had any other outlet than 
 the present one? 
 
 EXCURSION XXXI. To Switzerland. 
 About Glaciers. 
 
 You have learned the main facts about the Quaternary 
 deposits. We cannot attempt now to study very thoroughly 
 the way in which these results have been produced. Let me 
 only say that geologists are of the opinion that the whole 
 country was once covered by a great glacier, as far south as 
 the boulders extend. It is likely the surface was already 
 deeply covered with decayed rock-material, such as still 
 exists in the Southern States. As all glaciers move, this 
 great glacier moved southward. It shoved along much of 
 the loose decayed material, and, in doing so, smoothed and 
 striated the sound rock-surface underneath. The glacier 
 
186 GEOLOGICAL EXCURSIONS. 
 
 only extended south as far as the Ohio River, except in the 
 elevated, cooler region of the Appalachians. After some 
 ages, there was another change of climate, and the ice was 
 melted. Great floods carried sand and gravel over the 
 Southern States. At a later epoch, the water still flooded 
 the rivers, and at this time the high river terraces were 
 formed. By degrees the ice disappeared ; the lower terraces 
 were formed ; small lakes were becoming drained; beds of 
 marl and peat were forming, and the conditions of modern 
 times approached. So we stand just at the outcome of great 
 events which, in remoter times, transformed the surface of 
 the whole country. 
 
 Geologists think a good deal of light is thrown on the 
 origin of boulders and Drift by what may be seen in countries 
 where glaciers still exist. A glacier is a mass of ice which 
 has resulted from the softening and change of snows which 
 have lain a long time. You have seen the ice on the side- 
 walk or in the gutters, which has resulted from partially 
 melted snow especially when spring is approaching. Such 
 ice is glacier-like in character and origin. The great 
 glaciers last all summer, and continue from year to year. 
 So they can only exist in regions with a cool climate and 
 plenty of snow fall. The best known glaciers in our time 
 are those which occupy the valleys of the Alps. In the cut, 
 Figure 76, are two glaciers seen flowing along valleys which 
 lead upward toward the summit of Mont Blanc. The one 
 in the middle of the view is called Glacier des Bossons 
 (Glacier of Bossons, a little village at its foot), and the one 
 on the right is the Glacier de Taconnay. Every glacier in 
 
TO SWITZEKLAKD, 
 
 187 
 
 its course gathers up a great amount of rock rubbish, and 
 deposits it in a long ridge each side. These ridges are 
 called lateral moraines. Another mass is deposited at the 
 
 FIG. 76. VIEW OF A COUPLE OF GLACIERS FLOWING DOWN FROM MONT BLANC. 
 
 termination of the glacier. This is the terminal moraine. 
 In this cut you can see something of the terminal moraine 
 about the foot of both glaciers. It is made up of boulders 
 and clay. 
 
 But a more remarkable sight is shown in the cut, Figure 
 77, which is a vast boulder-strewn area at the foot of Glacier 
 des Bois, which is only the lower part of the Mer de Glace 
 or Sea of Ice. (Bois is the name of a little village at its 
 foot.) On the extreme right is a portion of the vast moraine 
 which borders the left side of the glacier, and continues 
 
188 
 
 GEOLOGICAL EXCURSION'S. 
 
 around to form part of the terminal moraine in the same 
 way as seen in Figure 76. Beyond this appears the white 
 termination of the glacier, with some boulders resting on its 
 back. The terminal face of the glacier is turned toward 
 us, and a large arch opens at its base into a dark passage, 
 from which a roaring, muddy stream of water rushes. There 
 
 PIG. 77. BOULDER-STREWN AREA AT THE FOOT OP THE MER DE GLACE, 
 VALLEY OF CHAMONIX. Compare the Boulder Field shown in Figure 8. 
 
 are in fact two streams, and these unite to form the Arvey- 
 ron, which, a little further on, unites with the Arve. The 
 glacier extends toward the right far up to the same snow- 
 covered summit of Mont Blanc from which we see the two 
 other glaciers proceeding in the last cut. At the very ter- 
 mination of this glacier, it is therefore, turned suddenly to 
 the left. This is to avoid the enormous mass of rock which 
 lies exactly in the main course of the glacier. This rock is 
 shown next beyond. It is a dome of porphyry, smoothed 
 and striated much like the quartzite dome shown in Figure 
 
TO SWITZERLAND. 189 
 
 74. The glacier, some years ago, was nearly a thousand 
 feet higher than at present, and flowed completely over this 
 porphyry obstacle. It was the glacier which smoothed and 
 striated its surface. This convinces us that the quartzite 
 dome on the north shore of Lake Huron may have been 
 smoothed and striated by a glacier. But glancing again at 
 Figure 77, you can see beyond the porphyry mass, the great 
 lateral moraine rising up. This continues down and con- 
 nects with the vast terminal moraine shown at the left of 
 our cut. 
 
 There are men living at that place who remember when 
 the glacier was 984 feet higher than at present, and extended 
 1640 feet farther, and at that time made the great terminal 
 moraine which still remains, and rises 80 feet high. The 
 moraine has pushed close to the little village of Bois, which 
 still stands close at its foot. Some of the huge boulders 
 rolled down among the houses and the people were greatly 
 terrified. It was in 1826 that the glacier was so much larger 
 than at present. Since that time the glacier has retreated 
 across the boulder-strewn area which we see, and has pro- 
 duced a scene which reminds us strongly of the boulder field 
 shown in Figure 3. 
 
 If this glacier should continue to melt away until it dis- 
 appears, the great moraines would remain. Now, we find 
 in America many ridges of gravel and boulders so much like 
 the Alpine moraines that we call them real moraines, and 
 believe that there were once glaciers which formed them. In 
 fact we often find them stretching across the foot of a valley 
 which could have been once filled with glacier ice. But 
 
190 GEOLOGICAL EXCURSIONS. 
 
 there are so many which extend for long distances that the 
 only explanation seems to be that the whole country was 
 once covered by glaciers. If this theory is correct, 
 then we are to think of these beautiful fields and valleys, 
 which are now the home of a busy and happy population, as 
 once covered by a sheet of ice as deep, as bleak and ver- 
 dureless as that which in our times covers the whole of 
 Greenland. 
 
 EXERCISES. 
 
 Is there any part of the world where the snow does not dis- 
 appear in summer ? Why does it not disappear on high moun- 
 tains ? Is there no thawing on high mountains in summer ? Does 
 it ever thaw in the Arctic regions ? Is it conceivable there might 
 be so little snow in any Arctic region, as to all melt in the summer? 
 What is meant by the limit of perpetual snow ? In what zone is 
 this limit highest ? Why may it be higher on some mountains 
 than on other mountains in the same latitude ? Is the climate 
 always too cold for farm crops in the neighborhood of Alpine 
 glaciers ? How close to the foot of a glacier may gardens be 
 planted ? Why is there a cold stream of air descending from the 
 surface of a glacier ? Are all the glaciers of the Alps retreating 
 like the Glacier des Bois ? How much further down the valley 
 of the Alps may the Alpine glaciers have extended formerly ? 
 Are there any glaciers in the United States ? If so, where are 
 they ? Is it supposable there were ever glaciers in the White 
 Mountains, the Green Mountains and the Alleghanies ? What 
 evidences of this would you expect ? Was the climate any colder 
 then, or were the glaciers simply caused by a greater amount of 
 snow fall ? How much of our country was covered with ice at 
 that time ? How far south did the ice extend ? How can we tell 
 how far south it extended ? What was the appearance of the 
 country at that time ? What distinguished scientist penetrated 
 to the centre of Greenland in 1883 ? 
 
THROUGH THE AGES. 191 
 
 EXCURSION XXXII. Through the Ages. 
 About the Plants and Animals of the Past. 
 
 Let us now, finally, in imagination travel down through 
 the Ages of the world's history, and note the appearances 
 from time to time assumed by our planet and its popula- 
 tions. Everything in geology indicates that the world is 
 very old, and has undergone many remarkable changes. 
 It is generally believed that it once existed in the form 
 of an intensely heated vapor, but we will say nothing about 
 that. We are pretty certain that it was once a globe of 
 melted mineral matter, and that after a long time, cooling 
 caused a crust to form over the surface. At a later period, 
 clouds of watery vapor first came into existence, and tor- 
 rents of rain poured down during many ages. "When the 
 clouds were exhausted, the earth was covered by a film of 
 water. It was a universal ocean. After many ages more, 
 sea weeds were in existence in the ocean. Whence they 
 came nobody knows. By and by some long ridges of sea 
 bottom rose above the ocean level, and became the begin- 
 nings of solid land. The sea weeds floated to the beach in 
 immense piles, and were buried beneath sediments which 
 resulted from the wear of the land and from chemical 
 precipitations. In course of time they were changed to 
 plumbago and here is some of that plumbago in the pencil 
 with which you write. 
 
 Ages later, the first animals appeared. Their origin is 
 another unsolved problem. They were simple gelatinous 
 forms, with scarcely any special organs ; but they existed in 
 
192 
 
 GEOLOGICAL EXCURSIONS. 
 
 cv 
 
 portion in a contracted state, c c, two pseudo- 
 pods closing around an infusorian ( Urocentrum). 
 a, diatoms within the animal. &, particle of 
 
 sawdust. 
 
 immense numbers, and 
 thousands, probably 
 millions, of them grew 
 in one mass, and secret- 
 ed great reefs of lime- 
 stone, much like coral 
 reefs. In Figure 78 
 are seen modern repre- 
 sentatives of these crea- 
 tures. They are not 
 
 grown together like the 
 FIG. 78. A LIVING REPRESENTATIVE OF THE 
 
 OLDEST ANIMAL. Amo&ba proteus (after ancient ones, and do 
 Leidy). not secrete any coral- 
 
 n, nucleus, c v, contractile vesicle, , posterior I--L "Kafon^n "R if 
 
 11KG 
 
 t h e i r iglly-like bodies 
 
 are believed to be sim- 
 Magnifled 100 diameters in the upper spe- - lar to the bod sub _ 
 cimen, and 125 in the lower. Found fre- 
 quently in fresh waters. stance of the ancient 
 
 ones. These earliest of 
 
 animals lived during the Eozoic Time. When Palaeozoic 
 Time began, considerable advance had been made in sea 
 weeds, and much more in animal life. We find in the 
 rocks many remains of creatures related to lobsters and 
 crabs, but very much lower in rank. We call them Trilo- 
 bites. (See Figure 79.) With them were many molluscs 
 related to the Pearly Nautilus, but most of them were 
 straight instead of coiled. Their shells were chambered. 
 The animal lived in the outer chambej?. Some of the 
 shells grew to a length of ten or fifteen feet. Figure 80 
 
THROUGH THE AGES. 
 
 193 
 
 shows one of these straight-chambered 
 shells. It belongs to the genus OrtkoOe- 
 ras (Orthoc'-e-ras). These rapacious beings 
 were the monarchs of the sea. There 
 were indeed other molluscs somewhat 
 like our modern bivalves and univalves, 
 but none of them was identical with 
 any living species. The older creatures 
 in all cases were simpler in their organi- 
 zation. 
 
 In the Devonian Age there was more 
 land. It supported forests of curious trees 
 which bore no flowers. Some of them 
 were much like modern Club Mosses. 
 We call this kind of tree Lepidodendron. 
 A view of one is presented in Figure 67. 
 Many coral-making animals flourished ; arid 
 the Trilobites and all the classes of mol- 
 luscs just mentioned continued to flourish. The most 
 important thing was the first appearance of vertebrated 
 animals that is, those having a back-bone. They were 
 fishes. Nature always begins with the lowest forms and 
 
 FIG. 79. A TRILO- 
 
 BITE FROM THE 
 
 SILURIAN. The 
 upper figure 
 shows the ani- 
 mal rolled up. 
 
 FIG. 80, RESTORATION OF AN ORTHOCERAS A STRAIGHT -CHAMBERED 
 
 SHELL OF PALAEOZOIC TIME. 
 a. arms ; /, funnel ; c, chamber ; s, siphuncle. 
 
194 
 
 GEOLOGICAL EXCUKSIONS. 
 
 FIG. 81. PTERICHTHYS 
 
 works upward. But they were 
 exceedingly singular fishes, and 
 one might almost call some of 
 them by other names. Figure 
 81 shows a specimen from the 
 Devonian rocks of Scotland, and 
 Figure 82 a specimen from the 
 Devonian strata of Ohio. Each 
 of these appears to have been 
 
 WINGED FISH (after Pan- twenty or thirty feet in length, 
 der). From the Devonian T j were ^ fc 
 
 of Scotland. 
 
 bony plates, instead of horny 
 
 scales. The Ohio fish had a head three feet long and two 
 feet broad. The jaws were armed with terrible teeth. 
 These fishes must have been in their time the cruel tyrants 
 of the Devonian Ocean. 
 
 So things went on in the sea during Carboniferous times. 
 But the straight-chambered shells dwindled away. So did 
 the Trilobites. But coiled-chambered shells gradually took 
 the place of the first, and higher crustaceans (like lobsters 
 and craw-fishes) the place of the latter. The fishes were 
 
 FIG. 82. DINICHTHYS OR TERRIBLE FISH (Newberry). From the Devonian 
 
 of Ohio. 
 
THKOUGH THE AGES. 
 
 195 
 
 much improved, but they were mostly after the fashion of 
 the bony-scaled gar-pikes. The great characteristic of the 
 Carboniferous age was the increase of land vegetation. But 
 it was still flowerless, and most of it resembled vegetation 
 which had begun to nourish in the Devonian. Views of 
 some kinds may be seen in Figures 66, 67 and 68. It 
 luxuriated over vast expanses which were little above sea- 
 level, and were many times submerged by the frequent 
 changes in the elevation of the land. The forests thus sub- 
 merged did not go to decay, but were changed into the coal 
 which we burn in our fires. There were no men to use the 
 timber when it grew ; therefore it was laid away to wait till 
 mankind should arrive. 
 
 After the coal was laid away, the Appalachian Mountains 
 were uplifted, and nature now introduced a great many 
 changes. This was now 
 
 the Mesozoic Time. JlKMRl " fill' 
 Flowering plants now 
 first appeared. The 
 coiled-chambered shells 
 became more beautiful 
 and more complicated. 
 Most of them belonged 
 to the type of Ammon- 
 ites. Here is one in 
 Figure 83. Notice that 
 the interior is divided into chambers by cross partitions or 
 septa which are very much folded. The old kinds of bi- 
 valves belonging to the type of lamp-shells called BracM- 
 
 FIG. 83. AN AMMONITE OF MESOZOIC 
 
 TIME. Ammonites serpentinus, Schl. 
 
 a, Side view. 6, Edgewise view c, Plan of septa 
 
 lobes. 
 
196 
 
 GEOLOGICAL EXCURSIONS. 
 
 opods disappeared, and only the modern kinds remained. 
 Fishes with bony skeletons and horny scales came into 
 existence. This is the type of our common fishes. Most 
 important of all, air-breathing animals dwelt on the land 
 and in the water. They had begun to exist during Coal 
 Measure times, but the vertebrates were related to Amphib- 
 ians. These vertebrates were Reptiles. They were the 
 
 FIG. 84. REPTILES OF MESOZOIC TIMES. (Hawkins.) 
 
 highest in existence on the earth. They presented a won- 
 derful amount of diversification among themselves. They 
 were suited to live in the ocean, the river, on the land or in 
 the air. They could walk or crawl, swim or fly. Some 
 went on four legs, some could walk on two. In Figure 84 
 some of these strange types are shown. Figure 85 shows 
 the skeleton of a reptile which could walk like a bird on 
 two feet, and had also foot and ankle bones closely resem- 
 bling those of birds. At the same time there were birds 
 which resembled reptiles in some respects. One European 
 
THItOUGH THE AGES. 
 
 197 
 
 bird had a long vertebrated tail 
 like that of a lizard, but quills 
 projected from each side. Other 
 birds in America resembled rep- 
 tiles by having teeth in their 
 jaws. In fact, the European bird 
 probably had teeth also. All 
 through this time, the ocean 
 stretched in America from the 
 Gulf of Mexico through the 
 centre of the continent to the 
 Arctic Ocean. 
 
 Next, nature introduced an- FIG. 85. A BIPEDAL REPTILE 
 
 other great change. The central 
 regions of the continent were up- 
 lifted. The great central ocean 
 
 parted. One branch shrank to the Gulf of Mexico and 
 the other to the Arctic Ocean. Some of those great 
 interior seas remained, whose places are now marked by 
 the "Bad Lands" of the Far West. This was the Ter- 
 tiary Age of Ceenozoic Time. But the most important 
 changes were among the animals. Now mammals became 
 very abundant. These are vertebrates which give milk. 
 There had indeed been a very few mammals in Mesozoic 
 Time ; but now they swarmed. Like the fishes when they 
 first appeared, the mammals were very peculiar, and many 
 of them were large. We could say that they bore remote 
 resemblances to modern mammals; but the striking pecu- 
 liarity was that the same animal bore resemblances to two. 
 
 OF MESOZOIC TIME. Had- 
 rosaurus. (After Haw- 
 kins.) 
 
198 GEOLOGICAL EXCURSIONS. 
 
 three, four or five modern mammals. Such animals we 
 call comprehensive types. They all had small brains, and 
 there was a preponderance, in the earliest epoch, of five- 
 
 FIG. 86. A MESOZOIC BIRD WITH A REPTILIAN TAIL. Archceopteryx. 
 (After Owen.) 
 
 toed quadrupeds, and many of these walked with the whole 
 length of the foot on the ground, like the bear, the kangaroo 
 and man. Figure 87 shows one of the earlier Tertiary 
 
 FIG. 87. SKELETON OF AN EARLY TERTIARY MAMMAL OF AMERICA. (After 
 Marsh.) Length, eleven feet. Dinoceras mirabile, Marsh. 
 
THKOUGH THE AGES. 
 
 199 
 
 forms. In the course of ages the comprehensive types dis- 
 appeared, and new types took their place, in which the 
 different characteristics were divided among different orders. 
 For instance, those having gnawing teeth, like rats, no 
 
 FIG. 88. A QUATERNARY MAMMAL OF AMERICA IMMEDIATELY BEFORE THE 
 GREAT GLACIER. (After Riou.) Megatherium Cuvieri, Desmarest. 
 Sometimes eighteen feet in length. 
 
 longer had hind teeth, like the tapir or the horse. Those 
 having five hoofed toes no longer had canine teeth like a 
 dog. Figure 88 shows a form closely related to the Eden- 
 tates of South America. The Megatherium lived just after 
 
200 GEOLOGICAL EXCURSIONS. 
 
 the close of the Tertiary. So the aspects of the animals 
 continued to approach nearer to modern animals ; and as 
 the interior seas became filled, the face of the continent 
 assumed the appearance it was destined to have in human 
 times. But there was no man yet. 
 
 Next came that increase of cold which caused the won- 
 derful glacier visitation of which you have learned. One 
 of its effects was to renew the surface of the earth to 
 obliterate the old scars and gullies caused by the long 
 continued erosions of the Tertiary Age ; to supply material 
 for a new subsoil, and make everything ready for man, who 
 was to appear in the next act of the drama. The great 
 glaciers were not half dissolved when man appeared in 
 Europe. Perhaps he was in America quite as early. It is 
 my own opinion that dark-skinned men had been in exist- 
 ence in the tropical regions during the whole glacial period, 
 and perhaps much longer. But you are not to consider this 
 settled. It is also my opinion that the first people in 
 Europe, as well as America and Asia, were yellow-skinned, 
 and that the white race appeared later. But, whatever may 
 be the truth about these things, it is quite certain that the 
 first colonists in Europe were rude, and that civilization has 
 grown up through the long struggle of man's intelligence 
 and better nature against the obstacles presented by his 
 own savage disposition, and the lack of inventions to aid 
 him in the subjugation of the earth. 
 
 After thousands of years, the white race has attained a 
 wonderful stage of improvement; and we should feel 
 thankful that our own lot has been cast in these later times, 
 
THKOUGH THE AGES. 201 
 
 when we can enjoy so many opportunities for acquiring 
 knowledge of the past and present, the distant and the 
 near, and for attaining the highest culture of our own social 
 and moral faculties. 
 
 Now, my dear pupils, I think it will be best to make 
 this the end of our series of Geological Excursions. There 
 are many things still which might be presented in a very 
 simple way, but we must postpone them all for the present. 
 I hope you have enjoyed these Excursions ; and I hope you 
 already feel eager to take a new start, and go with me over 
 a more thorough course in geology. 
 
 EXERCISES. 
 
 Can you mention any animal which belongs to the class of 
 Amphibians? In what age were Amphibians the highest type 
 of animals ? To what class of vertebrates does the salamander 
 belong? What is the difference between a salamander and a 
 lizard ? When did flowers first appear on the earth ? Was most 
 of the coal formed from flowering plants or from flowerless 
 plants? Mention several flowerless plants now living on the 
 earth. Why were not trees the first plants to exist ? Which 
 are highest, marine plants or terrestrial plants? On the 
 whole, was there an improvement of organization as the ages 
 passed by, or was there not ? What has been the best age in 
 the history of the world for man to live in ? What has been the 
 best period since man appeared in Europe ? What houses did 
 the first European people inhabit ? What implements did they 
 use ? What metals were they ignorant of ? What crops did 
 they neglect to raise ? Do you think they were as comfortable 
 as our own people ? Do you think they were as happy ? How 
 have education and civilization improved the condition of man- 
 kind? 
 
202 GEOLOGICAL EXCURSIONS. 
 
 QUESTIONS ON THE TEXT. 
 
 With Additional Exercises Interspersed. 
 
 [The following questions maybe used in a general review 
 of the whole subject. They may also be employed by the 
 teacher in connection with the daily Excursion ; but it will 
 be better for the teacher to acquire such familiarity with the 
 subject treated in the Excursion as to ask questions suggested 
 by the special circumstances. In no case are the Exercises 
 to be omitted, as these are not questions on the text, but 
 more in the nature of applications and inferences from the 
 facts presented in the text. ] 
 
 I. 
 
 1. What objects in the garden do not grow ? 2. In what par- 
 ticulars do plants differ from stones ? 3. How do plants take 
 nourishment ? 4. In what respect is an animal like a plant ? 
 5. In what respect does he differ from a plant ? 6. What is an 
 organic body ? 7. What is an organ ? 8. What is a function ? 
 9. Name some organs of a tree. 10. What are the functions of 
 the organs named ? 11. What objects in the garden have no 
 organs ? 12. Can a plant or an animal perform functions without 
 organs ? 13. Which has more organs, a bird or a plant ? 14. 
 Which has more, an apple tree or a mushroom ? 15. What is an 
 inorganic body ? 16. Do inorganic bodies perform any functions? 
 17. What is a mineral substance ? 18. Name some mineral 
 substances. 19. Are organic bodies composed of mineral sub- 
 stances ? 20. If so, how do they differ from inorganic bodies ? 
 21. Is a dead dog organic? 22. What is an organic product? 
 23. What would you call a tear? 24. Is a "living spring" or- 
 ganic ? 25. If not, why not ? 26. Why is it called living ? 
 
QUESTIONS ON THE TEXT. 203 
 
 II. 
 
 1. What is the soil in the garden composed of ? 2. What is 
 the difference between a pebble and a grain of sand ? 3. What 
 is a cobble stone ? 4. How does it differ from a stone broken 
 out of a quarry ? 5. What use is sometimes made of cobble 
 stones ? 6. What use is made of pebbles and gravel ? 7. How 
 could gravel be used to purify water ? 8. What is a boulder ? 
 9. How does it differ from a pebble ? 10. Are pebbles and 
 cobble stones boulders? 11. What colors can we detect in grains 
 of sand? 12. What are pebbles made up of? 13. What dif- 
 ferent colors can you detect in the grains of a pebble ? 14. What 
 is each different-colored portion of a pebble or cobble stone 
 called? 15. Is a grain of sand ever composed of more than one 
 mineral? 16. What is the indication of this? 17. What dif- 
 ferent colors of minerals may be detected in pebbles and larger 
 boulders ? 18. What colors have you yourself seen ? 19. What 
 is the shape of the separate minerals in a cobble stone ? 20. 
 Are the separate minerals quite distinct from each other, or do 
 they blend together? 21. Are they always the same in this 
 respect ? 22. Are all loose stones boulders ? 23. Mention some 
 which are not boulders. 24. How can you tell a boulder from 
 any other loose stone ? 25. What is a ledge of rocks ? 26. 
 What parts of our country are destitute of boulders ? 27. Men- 
 tion some uses for boulders. 28. What is the weight of the 
 great Gilsum boulder in N. H. ? 29. Can you mention any other 
 boulders of enormous size ? 30. What parts of our country are 
 well supplied with boulders? 31. Explain how to assort the 
 materials in the soil. 32. What is the soil principally composed 
 of ? 33. What is mud ? 34. Can you make mud out of stones? 
 35. If so, how would this mud differ from garden soil ? 
 
 III. 
 
 1. Where can we probably find a bank or bed of gravel ? 2. 
 What uses are made of gravel? 3. What uses are made of 
 sand ? 4. Are gravel and sand mostly deep in the earth or near 
 
204 GEOLOGICAL EXCURSIONS. 
 
 the surface? 5. What different kinds of materials may we 
 probably find in a gravel bank ? 6. What is sub-soil ? 7. Are 
 the different parts of a gravel bank stratified or unstratified ? 8. 
 What is meant by stratified ? 9. Are any parts of a gravel bank 
 perfectly stratified ? 10. What are laminae? 11. When is a bed 
 of sand said to be laminated? 12. What makes stratification 
 visible in a sand bank? 13. What is a talus? 14. What is 
 the origin of the cobble stones along the foot of a gravel bluff ? 
 
 15. What is it which sometimes cements gravel stones together ? 
 
 16. What is the color of the iron cement ? 17. How deep do we 
 sometimes find the Drift materials ? 18. Can the bed-rock 
 always be found at some depth ? 19. Is the Drift always par- 
 tially stratified throughout its entire depth ? 20. Is any part of 
 the Drift ever quite unstratified ? 21. Which is uppermost, the 
 stratified or the unstratified Drift ? 22. Correct this sentence: 
 " The well-digger came to a strata of clay." 23. How is a bed 
 of coarse pebbles produced ? 24. Mention some places where 
 coarse pebbles abound. 25. Have these pebbles been thrown 
 upon the beach or washed out of the bank ? 26. Did you ever 
 find a bed of pebbles cemented into a solid mass ? 27. Would 
 such a mass in the midst of the Drift be still a part of the Drift ? 
 28. Is the Drift always composed of incoherent materials ? 29. 
 How are sandy capes formed ? 30. What are sand dunes ? 31. 
 Name some regions noted for sand dunes. 32. Have you ever 
 seen the sand drifting like snow before the wind ? 
 
 IV. 
 
 1. Do any water currents exist beneath the surface of the 
 earth ? 2. What is the evidence of this ? 3. What prevents 
 the underground stream from soaking into the earth ? 4. How 
 are underground water basins formed ? 5. Suppose no clay beds 
 existed in the Drift, how deep would the water sink ? 6. How 
 deep should we then have to dig to obtain wells? 7. Where 
 does the water of the river come from ? 8. What would become 
 of the river if there were no clay beds for it to flow over ? 9. 
 
QUESTION'S OK THE TEXT. 205 
 
 Did you ever hear of rivers which soaked into the underlying 
 sand and disappeared ? 10. What makes a sandy desert so dry 
 and unproductive ? 11. In digging a well, what kind of a 
 stratum must be reached? 12. What kind of a stratum is water 
 always found in? 13. Suppose you find water above a clay 
 stratum and then make a hole through the clay, what will become 
 of the water ? 14. Explain how two wells very near each other 
 may be of very different depths. 15. Explain how a well on a 
 hill may be shallower than one at the foot of the hill. 16. What 
 is meant by a solution of limestone ? 17. Name some substances 
 which may be found dissolved in spring or well water ? 18. Why 
 does spring water often deposit something ? 19. How is traver- 
 tin formed ? 20. How is calcareous tufa formed ? 21. What 
 is so-called " petrified moss " ? 22. How is marl formed ? 23. 
 What is shell marl ? 24. What makes certain waters hard ? 25. 
 Name some part of the country where the waters are sometimes 
 soft. 26. What is a chalybeate spring ? 27. What substance 
 do chalybeate waters deposit ? 28. What is its usual color ? 29. 
 What other substance is often deposited with iron oxide ? 30. Is 
 the deposit of iron oxide ever sufficiently abundant to have any 
 value ? 31. What is made of it ? 32. What is yellow ochre ? 
 33. What is the rusty cement which sometimes holds pebbles 
 together? 34. Mention a locality where rusted pebbles are 
 plentiful ? 
 
 V. 
 
 1. Of what are rocks composed? 2. Of what are minerals 
 composed ? 3. What is a chemical element ? 4. What experi- 
 ment may be performed with chalk and vinegar? 5. What other 
 substances might be used to produce the same effect ? 6. What 
 experiments might be performed with limewater? 7. What is 
 the substance which clouds the limewater? 8. What acid is in 
 it ? 9. Where did this acid come from ? 10. What is a chemical 
 precipitate? 11. When the fine mud from the soil settled in our 
 glass vessel (Figure 4) was that a chemical precipitate ? 12. What 
 are atoms ? 13. What substances are composed of atoms ? 14. 
 
206 GEOLOGICAL EXCURSIONS. 
 
 Give an illustration to show the minuteness of atoms. 15. How 
 many different kinds of atoms are known ? 16. What is chemi- 
 cal affinity ? 17. What is a chemical compound ? 18. Name 
 some substances which contain only one chemical element. 19. 
 Name some which contain more than one chemical element. 20. 
 Where may all the chemical elements be found ? 21. Which is 
 the most abundant of the elements? 22. Which are the three 
 next most abundant ? 23. Name the other elements which make 
 an important part of the earth. 24. What elements exist abun- 
 dantly in the atmosphere and water ? 25. Which element has an 
 affinity for the greatest number of other elements ? 26. What is 
 an oxide ? 27. What is a chloride ? 28. Name an oxide and a 
 chloride. 29. What is an acid-forming oxide ? 30. How is it 
 converted into an acid? 31. What is a basic oxide ? 32. Name 
 some acids and bases. 33. How are acids and bases disposed 
 toward each other? 34. What is the termination of the name 
 of a strong acid? 35. What are salts? 36. When does the 
 name of a salt end in ate? 37. Can carbonic acid remain in 
 combination with lime when sulphuric acid is present ? 38. Why 
 is this? 39. What appearance is presented when the carbonic 
 acid is driven off ? 40. Where does it go ? 41. After the lime- 
 water in the bottle is covered with a white crust, suppose we pour 
 on a little dilute acid, what happens to the crust ? 42. If sul- 
 phuric acid was poured on, what new substance was formed ? 43. 
 Where is it ? 44. What is precipitated chalk ? 
 
 VI. 
 
 1. What is the need of a hammer in studying geology? 2. 
 Describe a suitable style of hammer. 3. How do we determine 
 the hardness of minerals? 4. What is the hardest mineral 
 likely to be found ? 5. Is it very abundant or somewhat rare ? 
 6. What different colors may quartz present ? 7. What is the 
 color of pure quartz ? 8. What lustre has quartz ? 9. What is 
 flint ? 10. What is red jasper ? 11. What causes the colors of 
 the different varieties of quartz? 12. What gems are nothing 
 
QUESTIONS ON THE TEXT. 207 
 
 but quartz? 13. Of what chemical substance is quartz com- 
 posed? 14. How many elements in this substance ? 15. What 
 is the color of quartz when pure ? 16. What is its crystalline 
 form ? 17. What proportion of ordinary sand is composed of 
 quartz ? 18. To what uses may ordinary sand be applied ? 19. 
 What varieties of quartz have you in your collection ? 
 
 VII. 
 
 1. What can you say of the abundance of quartz ? 2. How 
 many pounds in every hundred of ordinary rocks are quartz ? 3. 
 How does the hardness of feldspar compare with that of quartz ? 
 4. How does its lustre compare ? 5. How does its crystalline 
 form differ? 6. Can you distinguish any flat, crystalline faces 
 in fragments of feldspar ? 7. Do they look like the rough frac- 
 tures of quartz ? 8. What angle do they sometimes make with 
 each other? 9. Do you mean that all the angles of feldspar are 
 right angles ? 10. Are there any right angles in a crystal of 
 quartz? 11. What is the commonest color of feldspar? 12. 
 What other color does it present? J3. Is feldspar ever glassy 
 like quartz ? 14. How does the crystalline form of a glassy 
 feldspar differ from quartz ? 15. What peculiar markings on 
 the surface of some feldspars? 16. Is the common feldspar so 
 striated? 17. What three substances in the composition of a 
 feldspar? 18. What are the elements in each of these sub- 
 stances ? 19. What is silicate of alumina composed of ? 20. If 
 silicic acid, alumina and an alkali combine, what is the chemical 
 name of the compound ? 21. What mineral does it form ? 22. 
 Mention several alkaline substances. 23. Which of these is the 
 alkali in common feldspar? 24. What other feldspars are there ? 
 25. What is the prevailing color of soda-feldspar ? 26. What is 
 the composition of a glassy feldspar? 27. What feldspar is 
 most apt to be dark-colored ? 28. What is the name of common 
 feldspar ? 29. What name is applied in common to all the other 
 feldspars mentioned ? 30. What causes the colors of the feld- 
 spars mentioned ? 31. In 100 pounds of orthoclase, how many 
 
208 GEOLOGICAL EXCURSIONS. 
 
 pounds of silica ? 32. How many pounds of each of the other 
 constituents ? 33. Of what is common clay chiefly composed ? 
 34. What is kaolin ? 35. What are some uses of feldspar ? 36. 
 In what kind of rocks do feldspars occur most abundantly? 37. 
 What are the best states for the collection of feldspars? 38. 
 What states do not contain rocks with crystalline feldspars? 
 39. Do you mean that none of these states have boulders con- 
 taining feldspars? 40. Were your specimens of feldspar ob- 
 tained from boulders or from rocks in place ? 
 
 VIII. 
 
 1. What is the third light-colored mineral studied ? 2, How 
 does calcite compare in hardness with quartz ? 3. How with 
 feldspar ? 4. Can you often find calcite in boulders ? 5. Is 
 calcite as glassy as quartz ? 6. Has calcite any smooth faces 
 like feldspar? 7. How then can you distinguish it from feld- 
 spar ? 8. Do you find any right angles in calcite ? 9. How do 
 the angles of calcite differ from those of feldspar ? 10. What 
 are cleavage lines? 11. Is calcite ever transparent like quartz? 
 12. How, then, can you distinguish it from quartz ? 13. What 
 is the name of a common variety of calcite ? 14. What is the 
 crystalline form of dog-tooth spar? 15. What is the chemical 
 name of calcite? 16. How does it compare in composition 
 with chalk ? 17. How many grains of carbonic acid in 100 
 grains of calcite? 18. How many grains of lime? 19. What 
 is the chemical composition of carbonic acid? 20. What, of 
 lime ? 21. Represent these compounds with your chemical 
 cards. 22. What are the different elements present in carbon- 
 ate of lime ? 23. If magnesia is put in place of lime, what does 
 the mineral become ? 24. If magnesia is added to the lime, 
 what does it become? 25. What is magnesite? 26. What is 
 dolomite ? 27. Now, what are the chief means for distinguish- 
 ing calcite from quartz and feldspar? 28. Which of these will 
 effervesce with acids? 29. Which is hardest? 30. Which 
 softest? 31. Which most pearly? 32. Which most glassy? 
 
QUESTIONS OK THE TEXT. 209 
 
 33. Which has right angles ? 34. Which sometimes has striated 
 faces ? 
 
 IX. 
 
 1. What is the prevailing color of common mica ? 2. Under 
 what form does it exist ? 3. What is mica sometimes ignorant- 
 ly called? 4. Are the leaves of mica elastic or inelastic? 5. 
 How are they in some lustreless conditions of mica ? 6. What 
 is the degree of hardness of mica ? 7. What are the colors of 
 mica ? 8. Where may large plates of mica be obtained ? 9. 
 What is meant by saying that mica is the name of a family of 
 minerals? 10. What constituents are present in all micas ? 11. 
 What are the chemical elements in each of these constituents ? 
 12. What is the name of common mica ? 13. What renders it 
 generally dark-colored ? 14. What constituent causes the dull 
 lustre of some micas? 15. What are such micas called? 16. 
 What other dark mineral can you name? 17. What is the 
 color of hornblende? 18. Is this a common or a scarce min- 
 eral? 19. What is its hardness? 20. What crystalline form 
 does it have ? 21. Is this form like quartz ? 22. When lamel- 
 lar, how is it known from mica ? 23. Can you see the crystal- 
 line form of hornblende in a rock ? 24. What chemical con- 
 stituents in hornblende? 25. What colors do the varieties of 
 hornblende present? 26. What other mineral similar to horn- 
 blende? 27. What color does augite incline to? 28. What 
 other mineral occurs in thin scales? 29. How distinguished 
 from mica ? 30. What are the prevailing colors of talc ? 31. 
 What is its composition? 32. What is the feel of talc? 33. 
 What is soapstone ? 34. What are some uses of soapstone ? 
 
 X. 
 
 1. Of what are rocks generally composed? 2. Of what 
 minerals are most of the rocks formed? 3. How can we have so 
 many rocks formed from so few minerals ? 4. Of what is quartzite 
 composed ? 5. Is it as hard as quartz ? 6. What is a common 
 
210 GEOLOGICAL EXCURSIONS. 
 
 color for quartzite? 7. What is a common name for quartz 
 boulders ? 8. What is a vitreous quartzite ? 9. When is a 
 quartzite conglomeritic ? 10. What is a jaspery quartzite? 11. 
 What is a quartzose conglomerate ? 12. What is a granular 
 quartzite ? 13. What is a grit ? 14. What is a sandstone ? 
 15. Name some fine sandstones used for building. 16. Have 
 you ever seen the New York Brownstone? 17. Where does it 
 come from ? 18. Have you ever noticed the Ohio Freestones ? 
 19. Where are many grindstones obtained? 20. What differ- 
 ent colors does the Waverly Sandstone present ? 21. What 
 impurities are sandstones likely to contain ? 22. What is a 
 micaceous sandstone ? 23. How many kinds of quartzose rocks 
 can you now name ? 
 
 XI. 
 
 1. Why is it more convenient to study boulders than rocks 
 in ledges ? 2. Why, otherwise, is it better to do so ? 3. What 
 is one of Nature's methods for sticking together grains of sand ? 
 4. How can you ascertain whether a rock contains calcium car- 
 bonate ? 5. Are all rocks stuck together with calcium carbon- 
 ate ? 6. What mineral has great fondness for the company of 
 quartz ? 7. What other mineral is generally found in company 
 with these two ? 8. How can you distinguish feldspar from 
 calcite ? 9. What is the composition of granite ? 10. Is this 
 rock stratified or unstratified? 11. What is the coarseness of 
 granite ? 12. Which is most valuable, a coarse granite or a fine 
 one ? 13. What is a porphyritic granite ? 14. When is any 
 rock called porphyritic ? 15. What is the color of the quartz in 
 granite? 16. What, of the feldspar? 17. What, the mica? 
 18. What makes the reddish spots in granite ? 19. How many 
 kinds of quartz in granite? 20. How many of feldspar? 21. 
 How many of mica ? 22. How much mica in granite ? 23. What 
 gives granite sometimes a dark complexion ? 24. What gives it 
 a reddish complexion ? 25. When does granite have a grayish 
 hue? 26. What is a granulite? 27. What is a felsite ? 28. 
 What is a petrosilex ? 29. What are the uses of granite? 30. 
 
QUESTIONS ON THE TEXT. 211 
 
 What is a mica schist ? 31. Which contains most feldspar, 
 gneiss or mica schist ? 32. What is a hydromica schist ? 33. 
 Are schists stratified or unstratified ? 34. How can you tell a 
 mica schist from a gneiss? 35. What is greisen? 36. What 
 must be added to greisen to make it granite ? 37. What must 
 be added to a granular felsite to make it granite? 38. What 
 must be added to granulite to make it granite ? 
 
 XII. 
 
 1. What uses are sometimes made of boulders ? 2. What 
 opportunity is furnished the geological student at the building 
 of a boulder house ? 3. What colors of rocks may be seen at 
 a stone-cutter's yard ? 4. What is the general appearance of a 
 hornblendic rock ? 5. What minerals are apt to be associated 
 with hornblende ? 6. What is syenite composed of ? 7. What 
 is the origin of the name ? 8. What other rock does syenite 
 resemble ? 9. What is so called " Scotch Granite "? 10. What 
 is " Quincy Granite "? 11. Mention some buildings constructed 
 of syenite. 12. Where may syenite be found besides in bould- 
 ers ? 13. How does syenite compare with granite in durability ? 
 14. What is a micaceous syenite ? 15. What is a hornblendic 
 granite? 16. What is a hyposyenite? 17. What is diorite? 
 18. How does it differ from hyposyenite? 19. What is diabase? 
 20. What is a plagioclase feldspar? 21. What is syenitic 
 gneiss ? 22. Wh&t is dioritic gneiss ? 23. What is diabasic 
 gneiss? 24. What is hornblende schist? 25. What is horn- 
 blende rock? 26. What feldspar is dark- colored ? 27. When 
 is a rock said to be phanerocrystalline ? 28. When is it said to 
 be cryptocrystalline ? 29. Define "massive," "gneissoid" and 
 " schistose." 30. What is protogine ? 31. What is protogine 
 gneiss ? 32. What is talcose schist ? 33. What is talc rock ? 
 34. What is steatite ? 35. What massive rocks contain quartz ? 
 36. What ones contain no quartz ? 37. What rocks contain 
 hornblende ? 38. What must be added to greisen to make gran- 
 ite ? 39. What to hyposyenite to make syenite ? 
 
212 GEOLOGICAL EXCURSIONS. 
 
 XIII. 
 
 1. When is a rock said to be calciferous ? 2. What is a cal- 
 careous rock ? 3. What degree of hardness have marbles ? 4. 
 What is the effect of acid on them? 5. What is a dolomitic 
 marble ? 6. How may it be made to effervesce ? 7. Of what 
 mineral are marbles composed? 8. Are the separate crystals 
 visible ? 9. What is saccharoidal marble ? 10. What is statuary 
 marble? 11. Mention different varieties of marbles. 12. What 
 causes reddish colors in marbles? 13. What blackish colors? 
 14. What bluish colors? 15. What is a pudding-stone marble? 
 16. What is a shell marble? 17. State where different kinds of 
 marbles are quarried. 18. What is common limestone ? 19. 
 How does its composition compare with that of marble ? 20. 
 How does its stratification compare with that of marble ? 21. In 
 what three ways may limestones be distinguished from most 
 other rocks ? 22. What is ob'litic limestone ? 23. How are the 
 following words used: silicious, argillaceous, arenaceous, ferru- 
 ginous, carbonaceous, bituminous, petroliferous ? 24. What 
 distinction may be made between argillaceous and aluminous ? 
 25. How does chalk differ from common limestone ? 26. Where 
 does marl originate ? 27. What is it ? 28. What is travertin ? 
 29. What is calcareous tufa? 30. What is a stalactite? 31. 
 What is stalagmite ? 32. How does it compare with travertin ? 
 33. Which is the most durable material, marble or granite ? 
 
 XIV. 
 
 1. What is graphic slate? 2. How does the hardness of 
 slate compare with that of quartzite? 3. Why does slate not 
 effervesce with acid ? 4. What does slate become when pulver- 
 ized and moistened ? 5. Of what are bricks made ? 6. Is there 
 any fine sand in clay ? 7. How may it be separated ? 8. What 
 is the characteristic substance in clay ? 9. When is a substance 
 said to be aluminous ? 10. What is the difference between slate 
 and shale ? 11. What is argillite ? 12. How does it compare in 
 hardness with shale and slate ? 13. Of what is argillite com- 
 
QUESTIONS ON THE TEXT. 
 
 posed ? 14. What is kaolin ? 15. From what is kaolin formed ? 
 16. What has become of the alkali in the feldspar ? 17. What 
 is the use of kaolin ? 18. What effect has remaining alkali upon 
 the porcelain? 19. What is sometimes used in porcelain-making 
 besides kaolin? 20. What is the cause of the red color of 
 bricks? 21. What are the groups of fragmental rocks? 22. 
 What are the four conditions in which fragmental rocks exist ? 
 23. Name some indurated silicious rocks. 24. Name some in- 
 durated calcareous rocks. 25. Name an incoherent calcareous 
 rock. 26. Name a crystalline calcareous rock. 27. Which is 
 the commonest class of bed rocks? 28. What class of rocks 
 furnishes the greatest number of species and varieties ? 29. In 
 what parts of our country are the bed rocks mostly fragmental ? 
 30. Where are they mostly crystalline ? 31. What is a mica- 
 ceous slate ? 32. What is a calcareous sandstone ? 
 
 XV. 
 
 1. What are the two principal divisions of crystalline rocks ? 
 
 2. What are the two divisions of phanero-crystalline rocks ? 
 
 3. Which division embraces the greatest number of species? 
 
 4. What is the only phanero-crystalline rock which effervesces 
 with acids ? 5. If a rock is composed wholly of quartz, what is 
 its name ? 6. What, if of quartz and feldspar in crystalline 
 grains ? 7. What, if composed of quartz and mica ? 8. What, 
 if of quartz, feldspar and mica ? 9. What rock is made from the 
 union of hydromica and quartz ? 10. Hornblende and quartz ? 
 11. Hornblende and orthoclase ? 12. Hornblende and plagio- 
 clase? 13. Augite and quartz? 14. Augite and plagioclase ? 
 15. Talc and quartz? 16. Talc, quartz and orthoclase? 17. 
 Talc alone? 18. Hornblende alone? 19. Augite alone? 20. 
 What are some cryptocrystalline rocks ? 21. What is felsite ? 
 22. What is aphanite ? 23. What is hyposyenite ? 24. What is 
 diorite ? 25. How does diorite differ from diabase ? 26. How 
 does felsite differ from granulite ? 
 
214 GEOLOGICAL EXCURSIONS. 
 
 XVI. 
 
 1. How does water assort the materials which it moves ? 2. 
 Would any assortment take place if all the water continued to 
 have the same motion ? 3. When a torrent flows down a slope, 
 where are the coarser materials deposited ? 4. Where are the 
 finer deposited ? 5. What is alluvium ? 6. What is the origin 
 of the shells found in some alluvium ? 7. In what kind of water 
 do flags and rushes grow ? 8. On which side of a pond may 
 we find them? 9. What is the origin of peat? 10. What 
 caused the marsh and meadow flat upon the border of the pond ? 
 11. Is there any danger that the pond may become completely 
 filled ? 12. What would be in its place after that ? 13. Why 
 does the peat form on one side of the pond, and not on all sides ? 
 
 14. What is the prevailing direction of the wind in our region? 
 
 15. Then on which side of the pond should the peat marsh be ? 
 
 16. What is contributed to the pond from the surrounding hill 
 slopes? 17. How is the matter transferred to the pond? 18. 
 Where are the coarse portions of it deposited ? 19. Have you 
 ever seen a spot where there was once a lakelet which has been 
 filled? 20. What are bivalves and univalves? 21. Where do 
 they get the material for their shells? 22. What becomes of 
 the shells when the animals die? 23. What is the origin of 
 rnarl ? 24. Where does the mud in the stream come from ? 
 25. Where is it going ? 26. How does the sediment get in the 
 sea ? 27. How does the Mississippi become so muddy ? 28. 
 What does it do with its mud? 29. What is the bar of the 
 Mississippi? 30. Do other rivers also have bars? 31. What is 
 a river delta? 32. What becomes of the sediment carried far 
 beyond the mouth of a river ? 33. What is river sediment form- 
 ing in the bottom of the ocean? 34. What effects do ocean 
 waves produce upon the shores? 35. What becomes of the 
 material of the crumbling shore ? 
 
QUESTIONS ON THE TEXT. 215 
 
 XVII. 
 
 1. What is the source of the sediment in the roadside stream ? 
 2. What is erosion ? 3. How has the ravine been produced ? 4. 
 Why is the bed of the brook so stony ? 5. Where have the 
 sand and loam gone ? 6. By what means does the stream widen 
 its valley ? 7. How do we know its valley was once narrower ? 
 8. Mention a fine example of a rock-worn gorge. 9. Where has 
 the sediment gone from Watkins' Glen ? 10. Mention a fine 
 case of river erosion in Wisconsin. 11. What great river has 
 performed a vast amount of erosion ? 12. In what states may 
 examples of it be seen ? 13. What river in the Far West has 
 worn very deep gorges ? 14. Where, besides in the river gorges, 
 are the rocks wearing away ? 15. By what means are the rocks 
 everywhere destroyed ? 16. Where may be seen a great thick- 
 ness of decayed rocks ? 17. What is the evidence that the rocks 
 are decayed ? 18. Have the rocks decayed similarly in the 
 Northern States ? 19. What has become of the decayed material ? 
 20. How may a natural bridge be caused? 21. What grand 
 examples of erosion may be seen in Tennessee ? 22. What is 
 the basin of middle Tennessee ? 23. What is the valley of east 
 Tennessee ? 24. What enormous example of erosion may be 
 mentioned in Pennsylvania? 25. How high a mountain has 
 been worn down ? 26. In what part of Pennsylvania may this 
 result be seen ? 27. How do we know such a mountain was ever 
 there ? 28. How do rock columns come into existence ? 29. 
 Where may rock columns be seen? 
 
 XVIII. 
 
 1. How would the sea sediments appear if we could bring up 
 an acre and inspect them ? 2. How would the different layers be 
 distinguished ? 3. What relics would they contain ? 4. On 
 what would the depth of the sediments depend ? 5. Where could 
 you say the sediments came from ? 6. How might the sea sedi- 
 ments be converted to rock ? 7. What would make the rock a 
 stratified one ? 8. What would be the laminae in the rock ? 9. 
 
216 GEOLOGICAL EXCURSIONS. 
 
 What would make fossils in the rock ? 10. Are there really any 
 rocks such as these sea sediments would be under the circum- 
 stances stated ? 11. What rocks are they ? 12. What besides 
 sediments do limestones contain ? 13. In what parts of the 
 country are the rocks mostly crystalline? 14. In what 
 parts are they mostly uncrystalline ? 15. Which kind 
 contain most fossils ? 16. From which kind are most of the 
 boulders derived ? 17. Which kind are uppermost ? 18. How is 
 their age indicated by their relative position ? 19. What is 
 metamorphism ? 20. What three kinds of action had much to 
 do with metamorphism ? 21. What is the position of the older 
 rocks ? 22. How do the fossils differ among the uncrystalline 
 rocks. 23. Which existed first, marine animals, or terrestrial ? 
 
 24. State the order of appearance of different types of animals. 
 
 25. What are said to be some of the most important facts in 
 geology ? 26. Give the names of the Great Systems in their 
 order. 27. Give the names of the Systems in their order. 28. 
 Now recite them in the opposite order. 29. What Systems 
 belong to the Mesozoic? 30. What to the Palaeozoic ? 31. 
 What to the Eozoic ? 
 
 XIX. 
 
 1. How can you illustrate the systems of strata with an 
 onion ? 2. Is this a good illustration ? 3. In what respect is it 
 incorrect ? 4. Are Caenozoic rocks everywhere at the surface ? 
 5. Are Mesozoic rocks always the next under Caenozoic? 6. 
 What system of rocks may be found at the surface ? 7. Is the 
 earth's surface completely undistorted ? 8. What does Figure 
 31 represent ? 9. In what respect is this figure incorrect ? 10. 
 Why is nothing represented in the interior? 11. What is the 
 earth's crust ? 12. When is one formation said to overlie 
 another ? 13. What is the dip of a formation ? 14. When is a 
 rock said to outcrop ? 15. What system of rocks completely 
 surrounds the earth ? 16. Is this system everywhere covered by 
 later formations ? 17. Is it anywhere covered by all the later 
 formations ? 18. Which system of rocks has least extent on the 
 
QUESTIONS ON THE TEXT. 217 
 
 earth's surface ? 19. Why do not Mesozoic and Palaeozoic strata 
 cover all the earth ? 20. Why do they not have as great an 
 extent as formerly ? 21. Is it to be supposed they ever covered 
 the whole earth like the Eozoic ? 22. What were the Caenozoic 
 rocks formed from ? 23. How is it that some portions of the 
 Eozoic rocks are now above sea level ? 24. How are they higher 
 than some Mesozoic and Caenozoic strata ? 25. Explain how to 
 make a little map of the region about d near the lower side of 
 Figure 31. 26. Please make a map of the region about G, Fig- 
 ure 31. 27. What is the difference in the dip of the strata in 
 these two maps ? 28. Which way do rocks always dip in respect 
 to newer and older strata ? 
 
 XX. 
 
 I. What is shown by a geological map? 2. In what part of 
 the United States are the newer rocks ? 3. In what part are the 
 older rocks ? 4. What are the principal Eozoic areas shown on 
 our geological map ? 5. What system of strata is generally seen 
 next to Eozoic rocks ? 6. What is the law of the dip of strata ? 
 7. If Devonian rocks pass under Coal Measures, may the same 
 Devonian rise anywhere to a greater height than the Coal Meas- 
 ures ? 8. Explain how this can be. 9. Draw a diagram illus- 
 trating it. 10. What systems belong between the Cambrian and 
 the Lower Carboniferous? 11. Now look at the Cambrian 
 region in Tennessee along its eastern border; what system of 
 rocks joins it ? 12. Why are there no Silurian and Devonian ? 
 13. Can you find any Jura-Trias in Connecticut ? 14. What 
 system of rocks does it rest on ? 15. What systems are wanting 
 between the two ? 16. Why are they not there ? 17. Where is 
 the most elevated region in Wisconsin ? 18. On the line from 
 that region to Chicago, which way do the rocks dip ? 19. If 
 there is a sandstone at the bottom of the Cambrian, would that 
 be found under Chicago ? 20. Would the outcrop of that sand- 
 stone in Wisconsin be higher or lower than the surface at Chi- 
 cago? 21. If rain should fall on that elevated Wisconsin 
 outcrop, how far would it flow through the sandstone ? 22. Do 
 
218 GEOLOGICAL EXCURSIONS. 
 
 you imagine it would ever get as far as under Chicago ? 23. 
 Then if you should bore down at Chicago, into that sandstone, 
 what would rise out from the hole ? 24. Would this be an 
 artesian well ? 25. Now please make a drawing explaining it 
 all. 
 
 XXI. 
 
 1. What is a geological map? 2. Does a geological map 
 teach anything more than what appears on the surface of the 
 earth? 3. What must we attempt to do in studying such a 
 map ? 4. What is a geological section ? 5. In constructing a 
 section from Detroit to Grand Haven, what is the first thing to 
 do ? 6. Is it necessary to lay off precisely the distances shown 
 on the map ? 7. Will the section be correct if we take any mul- 
 tiple of the map distances ? 8. What is a multiple ? 9. How 
 do we know in what direction to draw the lines of dip from the 
 points determined ? 10. Why do we not draw lines of dip down 
 from Detroit and from Grand Haven ? 11. Where, on the west, 
 is the boundary between the Devonian and Silurian ? 12. What 
 is a geological profile ? 13. How, from the study of a common 
 map, can we get an idea of the surface configuration of a region ? 
 14. How is it shown that the centre of Michigan is somewhat 
 elevated ? 15. What right have we to represent Cambrian and 
 Eozoic in a section from Detroit to Grand Haven ? 16. Explain 
 how to construct a section from Canada to the Coal region of 
 Pennsylvania. 17. What may we infer about the surface con- 
 figuration along this line ? 18. Why do we generally represent 
 dips steeper than they really are ? 19. What effect has this on 
 the apparent thickness of the formations ? 20. In representing 
 the elevations and depressions of the surface, can we conveniently 
 use the same scale as in the distances along the surface ? 21. 
 Explain how to complete the section when the surface features 
 are to be shown. 22. Construct a profile section from St. Louis, 
 Missouri, to Columbus, Ohio. 
 
QUESTIONS ON THE TEXT. 219 
 
 XXII. 
 
 1. Name all the states in which any Eozoic rocks appear. 2. 
 Name all in which none appear. 3. What state has the greatest 
 area of Eozoic rocks? 4. What areas in the United States are 
 connected with the Canadian Eozoic ? 5. By what means may 
 we easily become acquainted with the kinds of rocks in the 
 Eozoic ? 6. What New England mountains are mostly composed 
 of Eozoic rocks ? 7. Mention some separate mountain summits 
 of the White Mountain chain. 8. What forms does weathering 
 most commonly produce in granitic and gneissic rocks ? 9. How 
 are pinnacled mountains produced ? 10. In what mountains are 
 such summits common? 11. What is the arrangement of the 
 strata in Mt. Kearsarge? 12. What evidences are shown of 
 extensive weathering ? 13. What is the appearance of a section 
 through the Canadian Eozoic ? 14. Where have been found the 
 remains of the oldest animals that ever lived on the earth? 15. 
 What is the appearance of a section through the Wisconsin 
 Eozoic? 16. Into what two systems is the Eozoic divided ? 17. 
 What kinds of rocks occur in the Laurentian ? 18. What occur 
 in the Huronian ? 19. What is the geological position of the 
 oldest iron ores? 20. Does the Huronian produce iron? 21. 
 Where ? 22. How does the iron occur in some cases, as, for 
 instance, at Marquette? 23. How does it occur at Pilot Knob? 
 24. How in the Penokie Iron Range ? 25. Point out some 
 locality where the Laurentian and Huronian are uncomformable. 
 26. What overlies the Huronian in the Penokie Range ? 27. 
 What useful metal is afforded by the Kewenian rocks ? 28. How 
 do we know the Eozoic rocks to be older than any others ? 29. 
 What is the thickness of the Eozoic rocks? 30. What indica- 
 tions have we of the vast age of the world ? 31. What do Ages 
 and Eras correspond to? 32. What evidences of the exertion of 
 immense forces are revealed in the Eozoic rocks ? 33. What is 
 the aim of the science of geology ? 
 
220 GEOLOGICAL EXCURSIONS. 
 
 XXIII. 
 
 1. What northwestern states contain Cambrian rocks? 2. 
 What parts of Canada contain them ? 3. What interior states 
 contain them? 4. What sea-board states? 5. What large 
 cities are located on Cambrian strata ? 6. In what respect 
 do Cambrian strata differ from Eozoic ? 7. How are the bluffs 
 of the upper Mississippi formed ? 8. What has caused the burial 
 of the bases of those bluffs ? 9. Explain how the " Hornet's 
 Nest " has been formed. 10. How has " Castle Rock," in Min- 
 nesota, been formed? 11. What is meant by an outlier? 12. 
 What is the name of the lowest sandstone ? 13. What is the 
 formation next above ? 14. What is the St. Peter's Sandstone ? 
 15. On what formation does the city of St. Paul stand ? 16. 
 What produces the " Falls of St. Anthony " ? 17. State the four 
 formations which make up the Cambrian system in Wisconsin 
 and Minnesota. 18. State why the St. Peter's Sandstone is at 
 the river level at Fort Snelling, and not so at McGregor. 19. 
 Describe the condition of the upper surface of the Eozoic in 
 Wisconsin. 20. Is extensive erosion shown by any other mem- 
 ber of the Cambrian system ? 21. What do these eroded surfaces 
 indicate ? 22. What great changes took place while these for- 
 mations were accumulating ? 23. Why is the Potsdam Sandstone 
 in Minnesota of such varying thickness ? 24. Describe the sec- 
 tion in Sauk county, Wisconsin. 25. Explain how the columns 
 shown have been caused. 26. What are the indications of a 
 break between the Eozoic and Cambrian ? 27. Describe the 
 Cambrian strata in the Cincinnati region. 28. Describe the dips 
 about Cincinnati. 29. How do the rocks here differ from the 
 Wisconsin Cambrian ? 30. What three groups, in general, con- 
 stitute the Cambrian? 
 
 XXIV. 
 
 1. What is the depth of the gorge at Niagara Falls? 2. 
 Which way do the formations dip along the Niagara River ? 3. 
 Where does the gorge of Niagara terminate on the north ? 4. 
 
QUESTIONS ON THE TEXT. 221 
 
 What is the upper formation of the Falls ? 5. In which direction 
 does the Niagara Limestone grow thinner ? 6. What forms the 
 rapids above Niagara Falls ? 7. What may be seen under the 
 Falls ? 8. How is space made there for standing ? 9. What 
 causes the recession of the Falls? 10. How rapidly do they 
 recede? 11. What was Table Rock? 12. What formations 
 may be traced below the Niagara Shale ? 13. What ore is found 
 in the Clinton Group ? 14. Where is the Medina Sandstone ? 
 15. What is its appearance ? 16. What are its uses ? 17. What 
 group next above the Niagara Group ? 18. Where may the 
 Silurian rocks be studied ? 19. Of what do they consist ? 20. 
 What valuable products are found in the Salina? 21. How is 
 brine obtained at Syracuse ? 22. Is any rock salt found in the 
 Salina Group ? 23. At what places ? 24. What new salt dis- 
 trict has recently been developed ? 25. Is there any prospect of 
 getting brine by boring at any other points in New York ? 26. 
 What change do the Niagara and Salina groups undergo when 
 traced eastward ? 27. What group above the Salina ? 28. 
 Where is it extensively developed ? 29. In what western states 
 is the Helderberg known ? 30. In what eastern states ? 31. In 
 what British Provinces ? 32. Name now the groups which make 
 up the Silurian system. 33. Name the groups of the Cambrian 
 and Silurian from below upward. 34. Name them from above 
 downward. 
 
 XXV. 
 
 1. What is the elevation of Mackinac Island? 2. Of what 
 rocks composed ? 3. How do they compare with the rocks on 
 the main land ? 4. Through what formations have the Straits 
 been excavated ? 5. By what agency does the excavation seem 
 to have been made ? 6. Describe " Sugar Loaf " at Mackinac. 
 7. Describe " Arched Rock." 8. What is the name of this lime- 
 stone. 9. To what region westward may the Devonian be traced ? 
 10. What is the age of the rocks at Little Traverse Bay? 11. 
 In what direction from Little Traverse Bay are Chemung rocks 
 to be found ? 12. What is their character in Michigan ? 13. To 
 
222 GEOLOGICAL EXCURSIONS. 
 
 what regions may the Devonian rocks be traced eastward ? 14. 
 What Canadian cities are located on the Corniferous Limestone ? 
 15. What New York cities are on the Devonian ? 16. What is 
 the geological position of Syracuse? 17. In what formation is 
 the valley of Onondaga Creek excavated? 18. What is the 
 Oriskany Sandstone ? 19. From Syracuse, which way must we 
 travel to find newer rocks ? 20. What group of rocks overlies 
 the Corniferous ? 21. What overlies the Hamilton ? 22. Men- 
 tion localities of the Chemung. 23. What Ohio cities are on the 
 Devonian ? 24. In what part of Ohio are the Chemung strata ? 
 25. Recite the names of the groups of Devonian strata. 26. 
 Enumerate all the groups from the top of the Devonian to the 
 bottom of the Cambrian. 
 
 XXVI. 
 
 1. What is the height of the bluff at Burlington, Iowa? 2. 
 What kind of rocks at the top of the bluff ? 3. What kind of 
 rocks at the bottom ? 4. How many different groups are found 
 here ? 5. What is the name of the upper group ? 6. What the 
 name of the lower group ? 7. How do we know it is proper to 
 divide these rocks into two groups? 8. What interesting fossils 
 in the upper group ? 9. What kind of limestone at the top of 
 the lower group ? 10. How do we know it belongs to the lower 
 group rather than the upper ? 11. By what other means than 
 the fossils may two groups be distinguished ? 12. Mention a 
 case where an eroded surface separates two groups. 13. Mention 
 a case where difference of dip separates two groups. 14. May 
 two groups be truly distinct without any appearance of uncon- 
 formability or intervening erosion ? 15. How then, can we know 
 they are distinct? 16. Suppose there are no fossils, can we then 
 prove them distinct ? 17. Point out regions covered by Lower 
 Carboniferous. 18. In what formation is Mammoth Cave ? 19. 
 How was the cave produced ? 20. What is the knob region ? 
 21. How are its features caused ? 22. What change takes place 
 as we follow the Carboniferous Limestone into Pennsylvania ? 
 23. How is the Lower Carboniferous located in Michigan ? 24. 
 
QUESTIONS ON THE TEXT. 223 
 
 What is the character of the lower part of the Carboniferous 
 Limestone Group in Michigan ? 26. How do we know the 
 gypsum formation is a part of that group ? 26. What other 
 region has a salt-and-gypsum deposit in the Lower Carboniferous ? 
 27. How is brine obtained along the Saginaw Valley? 28. Does 
 this brine come from the same formation as the brine at Syra- 
 cuse and Warsaw, N. Y. ? 29. What uses are made of the 
 Waverly Sandstone ? 30. Mention localities where it is quarried. 
 31. What is the character of the Waverly in eastern Pennsyl- 
 vania ? 32. What underlies the Waverly ? 33. If the Catskill 
 Sandstones should prove to belong to the Waverly Group, what 
 name must we apply to the Group ? 34. What is the position of 
 the False Coal Measures ? 
 
 XXVII. 
 
 1. Name some towns where coal-mining is carried on. 2. 
 What is the method of mining when the coal bed outcrops ? 3. 
 What is the method when the coal bed is deep beneath the 
 surface ? 4. Define the terms drift and shaft. 5. How is the 
 work in a coal mine laid out ? 6. Why are two drifts or two 
 shafts necessary ? 7. Of what kinds of rocks are the Coal 
 Measures composed ? 8. What is the thickness of the Coal 
 Measures ? 9. How many beds of coal may there be ? 10. 
 What fossils are found in coal mines? 11. How do the strata of 
 the western Coal Measures differ from those of Pennsylvania ? 
 12. What is the cause of the difference? 13. What is a, fault in 
 geology ? 14. What is a downthrow f 15. How extensive are 
 faults in some cases ? 16. What is the cause of faults ? 17. 
 What is the lowest stratum of the Coal Measures ? 18. What 
 is sometimes found beneath the Millstone Grit ? 19. What for- 
 mation in some regions rests on the Coal Measures ? 20. What 
 are the two groups of the Upper Carboniferous? 21. Enumerate 
 now all the groups of the Carboniferous. 
 
224 GEOLOGICAL EXCUES1OXS. 
 
 XXVIII. 
 
 1. What is the geological position of Selma, Alabama? 2. 
 What systems of strata north and south of Selma ? 3. What is 
 the " rotten limestone " ? 4. Trace the Cretaceous belt westward 
 from Selma. 5. Explain the numerous artesian wells of Ala- 
 bama. 6. Explain the section, Figure 72. 7. What is the 
 source of the water in the artesian wells ? 8. Why would not 
 artesian water rise to the surface at Eutaw ? 9. Name the 
 states which are partly underlaid by Cretaceous strata. 10. 
 What is the character of the Cretaceous rocks ? 11. How do 
 they compare with Palaeozoic rocks ? 12. What formations in 
 Alabama between the Cretaceous and the Coal Measures ? 13. 
 Explain this absence of formations. 14. What is meant by Jura- 
 Trias ? 15. Where do we find the Jurassic System distinctly 
 exposed? 16. What System underneath the Jurassic? 17. 
 Where is it in America, and how thick are the rocks ? 18. 
 What formation in the valley of the Connecticut River ? 19. 
 What footprints on the layers of the stone ? 20. What use is 
 made of this sandstone? 21. Mention other states in which the 
 same sandstone occurs. 22. Now give the names of the three sys- 
 tems embraced in the Mesozoic Great System. 23. Enumerate 
 all the systems of the Palaeozoic Great System. 24. Enumerate 
 all the groups of the Palaeozoic Great System. 
 
 XXIX. 
 
 1. In what part of Alabama are the Tertiary rocks ? 2. 
 What of geological interest may be seen at Claiborne ? 3. Of 
 what is the Claiborne bluff composed ? 4. Where else may the 
 " White Limestone " be seen ? 5. What interesting fossil 
 remains have been found in it ? 6. In what three particulars do 
 the Tertiary rocks differ from the Palaeozoic ? 7. To what 
 regions does the Tertiary extend ? 8. What islands on the 
 northern Atlantic border are probably underlaid by Tertiary ? 9. 
 What sort of rocks is to be seen at Gay Head? 10. What 
 fossils have been found there ? 11. What great Tertiary areas 
 
QUESTIONS ON THE TEXT. 225 
 
 west of the Mississippi River ? 12. In what territories do they 
 lie ? 13. How do we know that great lakes or seas once rested 
 there ? 14. Why have those lakes or seas disappeared ? 15. 
 Why has the Atlantic retreated from the eastern border Tertiary ? 
 16. How did the earlier and later Tertiary quadrupeds differ from 
 each other? 17. What was formed from the sediments which 
 accumulated in the interior lakes ? 18. Where did the sediments 
 come from ? 19. What has since happened to the rocks made 
 from those sediments ? 20. What is the nature of our western 
 " Bad Lands " ? 21. How have their columnar forms come into 
 existence ? 
 
 XXX. 
 
 1. Where may the Drift be found? 2. Why could not this 
 formation have originated in a marine sediment? 3. Of what 
 sorts of materials is the Drift composed ? 4. In what two par- 
 ticulars does southern Drift differ from northern ? 5. What is 
 the nature of the lower portion of the surface materials in the 
 Southern States ? 6. In which region is the true transported 
 Drift most abundant? 7. What is the character of the rock 
 surface under the northern Drift ? 8. In which region do we find 
 decayed strata still remaining in place ? 9. In what direction do 
 the grooves and scratches of the northern Drift extend? 10. 
 Mention localities where they may be seen. 11. Have you ever 
 seen any smoothed or striated rock surfaces ? 12. Do you think 
 they exist in the neighborhood of your home ? 13. Explain 
 what is meant by " Modified Drift." 14. What is " Till" ? 15. 
 What is the condition of the Drift around the shores of the 
 Great Lakes ? 16. What is a lacustrine deposit ? 17. What are 
 lake terraces ? 18. How have several river terraces been pro- 
 duced along one river ? 19. What is the proof of former higher 
 water in our lakes and rivers ? 20. How may the water of our 
 lakes have been dammed up ? 21. What are Champlain deposits ? 
 22. Enumerate now, in regular order, the surface materials of 
 the Northern States. 23. Enumerate the surface materials of 
 the Southern States. 24. What Quaternary phenomena exist at 
 
226 GEOLOGICAL EXCURSIONS. 
 
 the North and not at the South ? 25. What exist at the South, 
 but not at the North ? 
 
 XXXI. 
 
 1. What is the theory of geologists about a former great 
 glacier in America? 2. What became of the decayed rock 
 material which once covered the surface? 3. How could the 
 rock-smoothing and striation have been produced? 4. What 
 could have caused the continental glacier to disappear? 5. 
 From what source may we obtain light on these questions ? 6. 
 What is a glacier ? 7. Does a glacier imply constant, extreme 
 cold? 8. Would a glacier exist in a region where no thawing 
 ever took place ? 9. Would a glacier exist where but very little 
 snow fell? 10. What would you say is requisite that a glacier 
 may come into existence ? 11. Where are the best known glaciers 
 of modern times ? 12. What is a lateral moraine ? 13. What is 
 a terminal moraine ? 14. Of what are moraines composed ? 15. 
 What striking scene is displayed at the foot of the Glacier des 
 Bois ? 16. What is the source of the stream issuing from the 
 foot of a glacier ? 17. Has the Glacier des Bois been increasing 
 or decreasing? 18. What are the evidences of this? 19. How 
 much has it lowered? 20. How much has it retreated? 21. 
 What records of its former action may be seen? 22. When 
 was the glacier close to the village of Bois ? 23. How have the 
 boulders been strewn over the area at present intervening ? 24. 
 What do we find in America to remind us of this moraine ? 25. 
 How is it supposed the gravel ridges of America were produced? 
 26. How extensive must have been the American glacier ? 27. 
 What country presents a real picture of glaciated America ? 
 
 XXXII. 
 
 1. What does geology intimate respecting the age of the 
 world ? 2. What is thought to have been the earth's primitive 
 condition ? 3. How did the ocean originate ? 4. What was the 
 beginning of solid land ? 5. What were the first living things ? 
 6. What is the origin of plumbago ? 7. Give some description 
 
QUESTIONS ON THE TEXT. 227 
 
 of the first kind of animals ? 8. In what time did they begin to 
 live ? 9. What animals appeared in Palaeozoic Time ? 10. What 
 is a straight-chambered shell? 11. What changes were intro- 
 duced with the Devonian Age ? 12. What can you say about 
 Lepidodendron ? 13. What can you say about Pterichthys f 
 14. What about Dinichthys ? 15. What animal types dwindled 
 away in the Carboniferous Age ? 16. What was the character of 
 the vegetation in the Carboniferous Age ? 17. How were beds 
 of coal produced ? 18. When were the Appalachian Mountains 
 uplifted? 19. What can you say about A mm onites f 20. How 
 did the Devonian fishes differ from modern fishes? 21. When 
 did the modern types of fishes first become abundant? 2$. 
 What were the first air-breathing vertebrates ? 23. What were 
 the highest vertebrates during Mesozoic Time? 24. Mention 
 some of the different kinds of reptiles. 25. Which of these 
 kinds no longer live on the earth ? 26. In what respect were 
 some Mesozoic birds reptilian ? 27. What part of North America 
 was under water during the Mesozoic ? 28. How is this shown 
 on the geological map ? 29. What change took place in the 
 land at the end of the Mesozoic ? 30. What were the highest 
 animals during the Tertiary? 31. What is meant by compre- 
 hensive types f 32. What peculiarities about the brains of the 
 oldest mammals ? 33. What about their feet ? 34. What was 
 the use of the continental glacier to man ? 35. What was the 
 condition of the people who first inhabited Europe ? 36. How 
 have European people become so greatly improved ? 37. How 
 can knowledge make people happier? 
 
Il^DEX. 
 
 This index serves also as a glossary. The star denotes subjects illus- 
 trated by cuts. 
 
 Acadian formation, 139. 
 
 Acid-forming oxides, 33. 
 
 Acids, 33. 
 
 Actinolite, 51. 
 
 Adirondacks, 113. 
 
 Affinity, 32, 33, 34. 
 
 Ages, 130. 
 
 Alabama, 109, 114, 160, 168, 170, 
 171, 173, 174. 
 
 Alabaster, 157. 
 
 Albany, 114. 
 
 Albite, 44. 
 
 Alleghenies, 78. 93*. 
 
 Alluvium, 82. 
 
 Alpena, 144. 
 
 Aluminous, 75. 
 
 Ammonites, 195*. 
 
 Amoeba, 192*. 
 
 Amphibians, 196. 
 
 Animals, first advent of, 191. 
 
 Animals, fossilized, 191. See, also, 
 "Fossils." 
 
 Anorthite, 44. 
 
 Appalachians, 78, 92, 93* 109, 111, 
 112, 123, 132, 186, 195. 
 
 Archaeopteryx, 198. 
 
 Arched Rock, Mackinac, 149*. 
 
 Arctic Ocean, 197. 
 
 Argillaceous rocks, 74. 
 
 Argillite, 75. 
 
 Arnot, Penn., 162. 
 
 Artesian wells, 168, 169*. 
 
 Arve, 188. 
 
 Arveyron, 188. 
 
 Asbestus, 51. 
 
 Assortment of soil, 20*; of sedi- 
 ments, 81. 
 
 Atlantic Ocean, 111, 123. 
 
 Atoms, 31. 
 Augite, 51. 
 
 Bad-lands, 177*, 197. 
 
 Bay View, 150. 
 
 Berea, Ohio, 157. 
 
 Biotite, 50. 
 
 Birds of Mesozoic Time, 198. 
 
 Biscuit, 76. 
 
 Bivalves, 84, 195. 
 
 Black Hills, 109. 
 
 Blossburg mines, 163. 
 
 Bluffs on the Upper Mississippi, 
 
 132*. 
 
 Bog iron ore, 29. 
 Bois, glacier of, 187, 188*. 
 Bossons, glacier of, 186, 187*. 
 Boston, 114, 115. 
 Boulders, 17; large examples of, 17, 
 
 18* ; where wanting, 19. 
 Boulders and sand, 15, 179, 188. 
 Boulder-strewn areas, 19*, 188*, 189. 
 Brachiopods, 196. 
 Brazil, Ind., 160. 
 Break, geological, 136*. 
 Bricks, 74, 76. 
 Buffalo, 150. 
 Burlington, Iowa, 153. 
 
 Cairo, 111., 153. 
 Calcareous rocks,'J>9. 
 Calciferous, 69. 
 Calcite, 34*, 35*. 
 Caledonia, N. Y., 150. 
 Cambrian rocks and history, 131. 
 Cambrian groups, 135, 139. 
 Cambro-Silurian, 113, 114, 122. 
 Canada, 111, 113, 127, 144, 150, 180. 
 
230 
 
 INDEX. 
 
 Carboniferous limestone, 153. 
 
 Carboniferous rocks, 153, 160; 
 groups, 158, 161. 
 
 Castle rock, Minn., 134*. 
 
 Catskill group, 158. 
 
 Caves, origin of, 94. 
 
 Chalk, experiment with, 30; precip- 
 itated, 34; French, 77. 
 
 Chalk formation, 170. 
 
 Chalybeate water, 29. 
 
 Champlain deposits and epoch, 184. 
 
 Charlevoix, 150. 
 
 Charmoz, needles of, 126. 
 
 Chemical elements, 32. 
 
 Chemical principles, 30. 
 
 Chemung group, 150. 
 
 Chert, 74. 
 
 Chlorides, 33. 
 
 Chocorua, Mt., 126. 
 
 Cincinnati, 114, 132, 138, 139. 
 
 Claiborne, Ala., 173. 
 
 Cleavage, 47. 
 
 Cleveland, 157. 
 
 Clinton formation, 143. 
 
 Club-mosses, 165, 193. 
 
 Coal Measures, 160. 
 
 Coal mines, 160, 161; of Blossburg 
 company, 162. 
 
 Cobble stones, 15; mineral substan- 
 ces in, 16. 
 
 Colorado, 92. 
 
 Colorado River, 90. 
 
 Colors in pebbles and cobble stones, 17 
 
 Columbia, Tenn., 132. 
 
 Columbus, Ohio, 151. 
 
 Columns, geological, 99*, 176, 177*. 
 
 Composition of minerals, 53; of 
 rocks, 68. 
 
 Compound substances, 32. 
 
 Comprehensive types, 198. 
 
 Conglomerate, 55, 70. 
 
 Connecticut, 19, 45, 55, 71, 113, 171. 
 
 Connecticut River, 113, 171. 
 
 Corniferous limestone, 149. 
 
 Cortland, N. Y., 151. 
 
 Crawfordsville, Ind., 155. 
 
 Cretaceous system, 168. 
 
 Crust of the earth, 103. 
 
 Cryptocrystalline, 66. 
 
 Crystalline form, 42. 
 
 Crystalline rocks, 77, 96*. 
 
 Cumberland Mountains, 92; River, 
 114. 
 
 Dakota, 123, 170. 
 
 Dalles of the Wisconsin, 89*. 
 
 Davenport, Iowa, 153. 
 
 Decay of rocks, 87, 91. 
 
 Delaware, Ohio, 151. 
 
 Delta of Mississippi, 86. 
 
 Detroit, 116, 119, 157. 
 
 Devonian rocks, 146. 
 
 Devonian groups, 152. 
 
 Diabase, 65. 
 
 Dinichthys, 194*. 
 
 Dinoceras, 198. 
 
 Diorite, 65. 
 
 Dip of rocks, 103; law of, 108, 109, 
 113, 116. . 
 
 Dog-tooth spar, 47*. 
 
 Dolomite, 48. 
 
 Downcast in a mine, 161. 
 
 Downs, 25. 
 
 Downthrow, 166. 
 
 Drift, 21, 24, 178; northern and 
 southern distinguished, 179, 184; 
 modified, 181 ; connection of gla- 
 ciers with, 186. 
 
 Drifting in a mine, 160. 
 
 Dunes, 25. 
 
 Effervescence, 34, 69. 
 
 Egyptian marble, 70. 
 
 Element, 32. 
 
 Elements, chemical, 32. 
 
 Eozoic areas of U. S., 109, 123. 
 
 Eozoic rocks, 123; weathering of, 
 125*, 126*; folding of, 126*, 127*. 
 
 Eras, 130. 
 
 Erie, Lake, 145, 151. 
 
 Erosion of rocks, 87, 103, 104, 176; 
 at Watkins' Glen, 88*; at Dalles of 
 the Wisconsin, 89* ; near Trempea- 
 leau, 90*; in Wisconsin, 91*; in 
 Tennessee, 92*; in the Appalachi- 
 ans, 93*; in Colorado, 92, 94*; de- 
 termining forms of mountains, 124, 
 125* ; of Cambrian rocks, 133*, 
 134*; of general surface, 137; at 
 Mackinac, 147*. 
 
 Eutaw, Ala., 170. 
 
 Falls, of Niagara, 140, 141*, 142*; 
 
 of St. Anthony, 135. 
 False Coal Measures, 158. > 
 Face of crystal, 42. 
 
INDEX. 
 
 Faults, 166*. 
 
 Feel of a rock, 52. 
 
 Feldspar, angles of, 41*; crystal of, 
 42 ; composition of, 44. 
 
 Feldspars, 40. 
 
 Felsite, 60. 
 
 Ferns as fossils, 163. 
 
 Flint, 38. 
 
 Flint rock, 54. 
 
 Formations, how distinguished, 154. 
 
 Folding of strata, 126-130*. 
 
 Forces in geology, 130. 
 
 Forms of mountains, 124, 125*, 126*. 
 
 Fort Snelling, 134, 135. 
 
 Fossils, 28, 96, 191 ; distribution of, 
 in the rocks, 97, 98; in Cambrian 
 rocks, 133; in Hamilton rocks, 151, 
 in Coal Measures, 163, 164*, 165* ; 
 in Tertiary, 175. 
 
 Franklin, Tenn., 132. 
 
 Frazer Bay, 181. 
 
 Gangways, 161. 
 
 Gay Head, 175. 
 
 Geological column, 99. 
 
 Georgia, 109. 
 
 fjilsum boulder, 18. 
 
 Glacial epoch, 186, 200. 
 
 Glaciers, 185; in the Alps, 186, 187*, 
 
 diminution of, 189. 
 Gloucester boulder field, 19. 
 Gneiss, 60 ; syenitic, 65 ; dioritic, 65 ; 
 
 diabasic, 65. 
 Gneissoid, 66. 
 Goat Island, 143. 
 Goderich, 144, 150. 
 Grand Haven, 116. 
 Grand Rapids, 157. 
 Grand Traverse Bay, 118, 149. 
 Granite, 59; porphyritic, 59*; horn- 
 
 blendic, 64. 
 Granulite, 60. 
 Granular quartzite, 55. 
 Graphic slate, 74. 
 Gravel bank, 21, 22, 23*, 26. 
 Great Lakes, 24, 109, 181, 183. 
 Greisen, 61. 
 Grindstone City, 157. 
 Grit, 55. 
 Gypsum, where found, 157. 
 
 Hamilton group, 149. 
 
 Hammers, 36*. 
 
 Hard water, 28. 
 
 Hardness-tester, 37*. 
 
 Helderberg group, 145. 
 
 Hexagonal prism, 38. 
 
 Hornblende, 50, 51*. 
 
 Hornblende, schist, 65; rock, 65. 
 
 Hornblendic rocks, 62. 
 
 Hornets' Nest, Wis., 133*. 
 
 Hudson River, 145, 172. 
 
 Huron grindstones, 157. 
 
 Huron, Lake, 111, 144, 146, 148, 157, 
 
 180, 189. 
 
 Huronian system, 99, 109, 128. 
 Hydromica, 51. 
 Hyposyenite, 65. 
 
 Identifications, exercises in, 78. 
 
 Illinois, 64, 145, 160, 163, 165. 
 
 Indiana, 25, 64, 145, 152. 
 
 Indian Territory, 124. 
 
 Indurated and semi-indurated, 77. 
 
 Ingersoll, Ont., 150. 
 
 Inorganic, 14. 
 
 Invertebrate, 97. 
 
 Iowa, 56, 170. 
 
 Iron ores, where found, 128. 
 
 Iron range, section through, 129*. 
 
 Iron rust, 33. 
 
 Ithaca, N. Y., 151. 
 
 Jasper, 38. 
 
 Jurassic, 109, 113, 114, 171. 
 
 Jura-Trias, 171. 
 
 Kansas, 112, 160, 170, 171. 
 Kaolin, 45, 76. 
 
 Kearsarge, ML, 125*, 126*, 127, 130. 
 Kentucky 19, 111, 132, 155, 156, 160, 
 
 160, 167. 
 
 Kewenian rocks, 129*. 
 Knobs, 156. 
 
 Labradorite, 44. 
 
 Lacustrine deposits, 182. 
 
 Lake barriers, 183. 
 
 Lakelet filling, 83*. 
 
 Lake terraces, 182. 
 
 Lamellae, 43. 
 
 Laminae, 22, 96. 
 
 LaSalle, 111., 160. 
 
 Laurentian system, 99, 109, 128, 129. 
 
232 
 
 INDEX. 
 
 Lebanon, 132. 
 
 Lepidodendron, 165*, 193. 
 
 Lewiston, 142. 
 
 Lexington, Ky., 132. 
 
 Lime, 72. 
 
 Limestone, 71 ; oolitic, 72 ; varieties 
 
 of, 72, 78. 
 
 Limewater, experiment with, 30. 
 Little Traverse Bay, 118, 149. 
 London, Ont., 150. 
 Louisiana, 174. 
 Lustre, glassy, 38, 43, 48 ; pearly, 41, 
 
 43. 
 
 Mac Gregor, Iowa, 135. 
 
 Mackinac, 118, 146, 147, 148. 
 
 Madison, Ind., 132. 
 
 Magnesian limestone formation, 135. 
 
 Magnesite, 48. 
 
 Magnifying glasses, 43. 
 
 Maine, 64, 123, 145. 
 
 Mammals, 197; in the Tertiary Age, 
 
 197, 198*; in the Post Tertiary, 
 
 199*. 
 
 Mammoth Cave, 155. 
 Man in geology, 200. 
 Manitoulin Islands, 131. 
 Map constructed from a section, 105*, 
 
 106*. 
 Map, geological, explained, 109, 110*; 
 
 exercises on, 113, 114, 115. 
 Marbles, 69; saccharoidal, 70; statu- 
 ary, 70; argillaceous veinings in, 
 
 70 ; where found, 128. 
 Margarodite, 51. 
 Marl, 28, 72. 
 
 Marquette iron region, 128, 181, 188*. 
 Marsh, how formed, 82*, 84. 
 Martha's Vineyard, 24, 29, 174. 
 Maryland, 71, 109. 
 Massachusetts, 19, 45, 64, 71, 113, 114, 
 
 123, 132, 139, 145. 
 Medina sandstone, 144. 
 Megatherium, 199. 
 Merde Glace, 187. 
 Mesozoic rocks, 168; systems, 172. 
 Metamorphism, 97, 113. 
 Mexican gulf, 86, 168, 171, 197. 
 Micaceous rocks, 57. 
 Micas, 50. 
 Mica-schist, 61. 
 Michigan, 17, 18, 23, 56, 64, 71, 112, 
 
 113, 116, 118, 119, 129, 131, 146, 
 
 155, 156. 
 
 Michigan, Lake, 112, 117, 118, 146, 
 
 148. 
 
 Millstone grit, 167. 
 Milwaukee, 113, 119. 
 Mineral, 14, 16. 
 Minerals, composition of, 53. 
 Minneapolis, 35. 
 Minnehaha Falls, 135. 
 Minnesota, 64, 78, 90, 131, 134, 137, 
 
 170. 
 Mississippi Eiver, 85, 86, 90, 133, 135, 
 
 153. 
 Missouri, 19, 112, 123, 128. 145, 151, 
 
 160. 
 
 Missouri River, 85, 95. 
 Mobile, 114, 169. 
 Modified Drift, 181. 
 Montana, 171. 
 Mont Blanc, 186, 188. 
 Monument Park, Colorado, 94*. 
 Moraines, 187*, 188*. 
 Moss, "petrified, "28* 
 
 Nantucket, 174. 
 
 Nashville, 114, 122, 132. 
 
 Nebraska, 170. 
 
 New Brunswick, 145, 157. 
 
 New England, 19, 71, 77, 96, 113, 
 
 180. 
 New Hampshire, 17, 50, 123, 127, 131, 
 
 145. 
 
 New Haven, 172. 
 New Jersey, 55, 96, 172, 174. 
 New Mexico, 177. 
 New York, 28, 48, 55, 71, 78, 88, 89, 
 
 113, 123, 132, 140, 144, 151, 158. 
 Niagara Falls and gorge, 140, 141*, 
 
 142*. 
 Niagara limestone, 142; shale, 143; 
 
 group, 145. 
 
 North Carolina, 64, 109, 172. 
 Nova Scotia, 139, 145. 
 
 Ochre, 29. 
 
 Ohio, 55, 64, 111, 114, 132, 145, 151, 
 
 155, 160. 
 Ohio River, 151, 155, 157, 169, 186, 
 
 194. 
 
 Oneida conglomerate, 144. 
 Ontario, Lake, 111, 113, 120, 121, 
 
 132, 141. 
 Oolitic limestones, 154. 
 
INDEX. 
 
 233 
 
 Organic and inorganic, 13. 
 
 Organic products, 14. 
 
 Organs, 13. 
 
 Oriskany sandstone, 150. 
 
 Orthoceras, 193; restoration of , 193*. 
 
 Orthoclase, 42*, 44. 
 
 Outcrop of strata, 103. 
 
 Outliers of Cambrian rocks, 134*, 
 
 137. 
 
 Overlying formations, 103. 
 Oxides, 32, 33. 
 
 Panama, N. Y., 151. 
 
 Parian marble, 76. 
 
 Peat, 82 ; formation of, 83*. 
 
 Pebbles, 15, 16; colors and grains in, 
 
 16. 
 Pennsylvania, 55, 93, 111, 120, 156, 
 
 158, 166. 
 
 Penokie range, 128, 129. 
 Permian group, 167. 
 Petoskey, 150. 
 Petrosilex, 60. 
 Phanerocrystalline, 66. 
 Pilot Knob, 128. 
 Plagioclase, 44. 
 
 Plants in the rocks, 163, 164*, 165*. 
 Porcelain, 45, 76. 
 Porphyritic, 59. 
 Portland, Conn., 171. 
 Post Tertiary, 109. 
 Potomac marble, 70. 
 Potsdam sandstone, 135, 137, 139. 
 Pottery, 76. 
 Prairie du Chien, 133. 
 Profile, geological, 119. 
 Protogine, 66. 
 Pterichthys, 194*. 
 Pudding stone, 70. 
 
 Quartz, 36, 37, 39*. 
 Quartzite, 54 ; striated dome of, 180*. 
 Quartzose rocks, 54. 
 Quaternary formations, 178; classi- 
 fied, 184. 
 Quebec, 145. 
 
 Questions on the Text, 202. 
 Quincy granite, 64. 
 
 Recession of Niagara Falls, 143. 
 Reptiles, 196*; bipedal, 197*. 
 Rhode Island, 113, 123. 
 
 Richmond, Ind., 132. 
 Rock salt, 144. 
 Rocky Mts., 95. 
 Rotten limestone, 168. 
 
 Saginaw Bay, 157. 
 
 Salina group, 144. 
 
 Salt in Salina group, 144; in Car- 
 boniferous limestone group, 157. 
 
 Salt wells, 144, 145. 
 
 Salts; 33. 
 
 Sandstone, 55 ; varieties of, 78. 
 
 Sandusky, 114, 151. 
 
 Savannah, 122. 
 
 Scenery of Chemung rocks, 151. 
 
 Schist, mica, 61; hydromica, 61; 
 hornblende, 65; talcose, 66. 
 
 Schistose, 66. 
 
 Scotch granite, 64. 
 
 Section constructed from a map, 106*, 
 116, 117-122*. 
 
 Section of the earth's crust, 107*. 
 
 Section from Detroit to Grand Haven, 
 116-119*; from Canada to Will- 
 iamsport, 120-121*; from Nash- 
 ville to Savannah, 122*; through 
 Mt. Kearsarge, 126*, 130; in Can- 
 ada, 127*; in Wisconsin, 128*; 
 through an iron range, 129* ; along 
 the Upper Mississippi, 135* ; across 
 the Cincinnati swell, 139*; across 
 Mackinac Island, 147*; at Burling- 
 ton, Iowa, 153* ; in Coal Measures 
 of 111., 165*; in Coal Measures of 
 Penn., 166*; in Alabama, 169*. 
 
 Sediments, 81, 85, 86. 
 
 Selma, Ala., 168, 169, 170. 
 
 Septa of chambered shells, 195. 
 
 Soapstone, 52, 66. 
 
 Soft water. 29. 
 
 Soil, what composed of, 20. 
 
 Solution, 27. 
 
 South Carolina, 109. 
 
 Springs and wells, 26*. 
 
 Stalactite, 72. 
 
 Stalagmite, 72. 
 
 St. Anthony Falls, 135. 
 
 Steatite, 52, 66. 
 
 St. Ignace boulders, 18. 
 
 St. Lawrence River, 109, 111,113; 
 Gulf, 151. 
 
 Stone lilies, 154, 155. 
 
234 
 
 INDEX. 
 
 St. Paul, Minn., 133, 134, 135. 
 
 St. Peter's sandstone, 135, 137. 
 
 Strata, 24, 85, 96; systems of, 95; 
 enwrapping the earth, 101, 102*; 
 folding of, 126-130*; of Coal 
 Measures, 163, 165*, 166*. 
 
 Stratification, 22, 59. 
 
 Strise on feldspars, 43. 
 
 Striated rock-surfaces, 180*. 
 
 Structure, below the surface, import- 
 ant, 112, 116; of Mt. Kearsarge, 
 126*. 
 
 St. Stephens, Ala, 169, 174. 
 
 Sugar loaf, Mackinac, 148*. 
 
 Superposition of rocks, rule of, 97,98. 
 
 Switzerland, 125, 185. 
 
 Syenite, 63; micaceous, 64. 
 
 Syracuse, N. Y., 150. 
 
 Systems of strata, 95, 98, 99*, 102*. 
 
 Table of, samples of rocks and min- 
 erals, 11 ; elements, 32 ; composition 
 of minerals, 53; composition of 
 rocks, 68; fragmental rocks, 77; 
 for rock-determination, 79; geo- 
 logical formations, 99*; quater- 
 nary formations, 184. 
 
 Table-rock, 141*, 143. 
 
 Taconnay, glacier of, 186, 187* 
 
 Talc, 50, 52. 
 
 Talcose, 66. 
 
 Talus. 22. 
 
 Tennessee, 70, 91, 92, 111, 114, 160, 
 167. 
 
 Tennessee, great erosion in, 92*. 
 
 Terminations of crystals, 39*. 
 
 Terrace formation, 184. 
 
 Terraces, 182. 
 
 Terrible fish, 194*. 
 
 Tertiary formations, 173. 
 
 Tertiary lakes or seas, 176. 
 
 Texas, 112, 170, 171, 174. 
 j Theory, specimen of, 147. 
 Till, 181. 
 Toledo, 157. 
 
 Tombigbee River, 169, 174. 
 Tourmaline, 56. 
 Travertin, 28, 72. 
 Tremolite, 51. 
 Trempealeau, cliffs at, 90*. 
 Triassic system, 171. 
 Trilobites, 192. 
 Tufa, 28*, 72. 
 Tuscaloosa, 169. 
 
 Unaka Range, 91. 
 Unconformability, 136*. 
 Univalves, 84. 
 Utah, 166. 
 
 Vein, 40, 42, 57. 
 Vermont, 17, 70, 71, 131, 139. 
 Virginia, 19, 109, 158, 172. 
 Vitreous quartzite, 55. 
 
 Warsaw, N. Y., 145. 
 Washington, Mt., 124, 127. 
 Watkins' Glen, 88*. 
 Waverly group, 154; sandstone, 157. 
 Weathering of rocks, 124; see also 
 
 "Erosion." 
 Western states, 28. 
 White limestone in Ala., 173. 
 White Mountains, 124, 130. 
 Wilkesbarre, 160. 
 Williamsport, Penn., 120. 
 Winged fish, 194*. 
 Wisconsin, 64, 89, 90, 91, 111, 112, 
 
 113, 119, 123, 128, 131, 134, 136 r 
 
 137. 
 
 Wyandotte cave, 156. 
 Wyoming, 145. 
 
YC 49599 
 
 
 5^*1810 
 
 UNIVERSITY OF CALIFORNIA LIBRARY