J. Milter t 
 
 THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 OF CALIFORNIA 
 
 LOS ANGELES 
 
 Ik RALPH D. iEB LffiRAKY 
 
 0'A*TMENT OF GEOLOGY 
 
 UNIVERSITY of CALIFORNIA 
 
 ' < ANiiJ-XES. CALIF. 
 
Shtff 
 
PRACTICAL EXERCISES IN 
 PHYSICAL GEOGRAPHY 
 
 BY 
 
 WILLIAM MORRIS DAVIS 
 
 PROFESSOR OF GEOLOGY IN HARVARD UNIVERSITY 
 
 GINN & COMPANY 
 
 BOSTON NEW YORK CHICAGO LONDON 
 
COPYRIGHT, 1908, BY 
 WILLIAM MOREIS DAVIS 
 
 ALL RIGHTS RESERVED 
 88.5 
 
 Cfte gtfctnaum ffrtfl* 
 
 GINN & COMPANY PRO- 
 PRIETORS BOSTON U.S.A. 
 
Library 
 
 PREFACE 
 
 The object of this Text and the accompanying Atlas is to provide 
 in as compact a form as possible a series of disciplinary exercises 
 which may be assigned as " laboratory work " in connection with any 
 of the modern text-books on Physical Geography. 
 
 The need of such exercises is generally recognized. Experience 
 has shown that a student may fail to acquire a clear understand- 
 ing of the facts and problems of Physical Geography if they are 
 presented only through the text of a printed page ; and that even 
 the ornamentation of the page by pertinent illustrations does not 
 always suffice to ensure a full comprehension of essential points. 
 The student's attention must be directed to and detained upon each 
 feature of a complicated fact, each step of a large problem, in order 
 that the facts and problems may reach his understanding and remain 
 in his memory ; hence the desirability of combining the performance 
 of a series of systematic exercises with the study of a text. 
 
 The topics selected for the Exercises here presented are such as 
 are treated in greater or less fullness in all modern text-books. The 
 Exercises may be taken up in such order as the teacher shall deter- 
 mine : those on the atmosphere and the ocean may follow or precede 
 those on the lands ; those on the lands may be rearranged if desired, 
 except that it is well to place Exercise I early in the series because 
 of its many applications, and to place Exercises VII and VIII late 
 in the series because of the greater detail of their problems. 
 
 The method recommended for performing the Exercises is stated 
 in the General Instructions (pp. 1 and 2). It may be here added 
 that it will be found useful to allow students to read the Text and 
 to examine the Atlas in a preliminary study period, and thus to 
 
 754289 
 
iv EXERCISES IN PHYSICAL GEOGRAPHY 
 
 construct mental answers and imaginary diagrams in preparation 
 for oral answers in a recitation or for written and graphic answers 
 in a laboratory period. 
 
 The Exercises are not divided into separate lessons ; they are left 
 like the chapters of a text-book, to be divided by the teacher accord- 
 ing to the time assigned for laboratory work and to the advance- 
 ment of the pupils. The Exercises are, moreover, planned so that 
 they may be used for a shorter or a longer course, according to the 
 time allotted to Physical Geography in a programme of studies. 
 In a short course all the bracketed questions and sections may be 
 omitted without lessening the continuity of the work. For still more 
 abbreviation, written answers in the pupil's notebook may be replaced 
 by oral answers recited in succession by different members of a class ; 
 but it is recommended that after such a recitation the teacher should 
 indicate certain questions for which the answers should be carefully 
 written by all members of the class in order to secure a clear under- 
 standing of the most important points. 
 
 The Exercises may be profitably extended through a longer course 
 by requiring written answers, carefully phrased, for all questions 
 in the Text. Additional questions, which every teacher will inevi- 
 tably invent for himself as the work progresses, may be frequently 
 introduced. Questions concerning opportunity for human settle- 
 ment and movement, conditions of human occupations, etc., may 
 be greatly increased. Some examples of such questions are given, 
 as in Exercise V, 3 and 12 ; but it has been necessary to exclude 
 them, as a rule, in order to save space. Still further extension of a 
 very profitable kind may be made by having the pupil draw temper- 
 ature and pressure gradients and generalize wind movements on 
 selected governmental weather maps, following the methods of Exer- 
 cise XII ; or by calling for the preparation of maps, in hachures or 
 contours, of selected parts of the land forms shown in the block 
 diagrams of the Atlas ; or by assigning certain parts of selected 
 topographical maps published by governmental surveys for careful 
 description and explanation. But in all cases, whether the work 
 
PREFACE v 
 
 makes part of a long or of a short course, it is advised that minute 
 accuracy is not to be expected in the answers to questions regarding 
 distances, altitudes, and locations, and that, in general, the answers 
 to questions should be simple rather than elaborate. 
 
 The plates in the Atlas on which the Exercises are largely based 
 are in most cases ideal designs and not copies of actual occurrences ; 
 but the charts of mean temperatures, prevailing winds, and ocean 
 currents are exceptions to this statement. The reason for giving 
 ideal examples of weather maps and of land forms is, that only in 
 this way can the systematic progress of teaching be secured. In 
 the daily weather maps and on the large-scale topographical maps 
 published by our governmental bureaus, the illustrations of typical 
 features are nearly always complicated by the addition of irrele- 
 vant details, which are distracting to the beginner. Moreover, these 
 official maps do not and should not attempt to emphasize certain 
 typical features and to subordinate unessential details ; they are 
 prepared for adult experts ; they must present the facts of nature 
 in all the complications of their actual occurrence. But to use such 
 maps in the first lessons on Physical Geography would be much the 
 same as to use pages of actual accounts taken from the books of a 
 large commercial establishment in the first lessons in arithmetic, 
 and thus to introduce division, interest, addition, fractions, and so 
 on, in the haphazard order of their daily occurrence in business, 
 instead of in a well-arranged, systematic order appropriate for a 
 beginner's study in school. 
 
 The author is, however, aware of various imperfections in the 
 ideal diagrams of the Atlas. Effort was made to find a professional 
 draftsman who would prepare thoroughly satisfactory drawings, but 
 no one could be discovered who possessed at once a sufficient knowl- 
 edge of the subject and a trained proficiency of handiwork. Among 
 the shortcomings which a redrawing might lessen are certain errors 
 of perspective in some of the block diagrams ; some unintentional 
 disagreement of scales among the successive members of a single 
 series of diagrams ; an insufficient depth in the gorge between lakes 
 
vi EXERCISES IN PHYSICAL GEOGRAPHY 
 
 A and C, in 17 2 (for manner of reference to Plates and Figures see 
 p. 1), and a lack of expressive emphasis in the shading of the sea 
 cliffs in 35 1. It is hoped that these subordinate defects will not 
 seriously interfere with the usefulness of the diagrams for the pur- 
 poses of teaching. 
 
 The importance of associating actual phenomena, as they occur 
 in nature, with the ideal types given in the Atlas is fully recognized. 
 A step towards such association is made by introducing in Plates 
 35-39 a number of maps, reproduced with more or less simplification 
 from parts of selected topographical sheets of different areas in the 
 United States, published by the National Geological Survey (see 
 explanation of plates, page 3 of Atlas), and by calling for the location 
 of these actual examples, as well as of a number of other examples 
 indicated by name in the Text, on the outline maps of the United 
 States and the continents, Plates 40-45. All these actual examples 
 should be carefully learned by name and location in order to give 
 reality to the Exercises. Just as the condensed statements of a 
 text-book should be elaborated by the teacher and illustrated by the 
 exhibition of appropriate maps, pictures, and specimens, so this 
 Text and its Atlas may be profitably supplemented by the exhi- 
 bition of selected weather maps, published by the Weather Bureau, 
 Department of Agriculture ; by the study of full-sized topographical 
 maps published by various governmental bureaus ; and by the exami- 
 nation of such photographs and lantern slides as may be available to 
 illustrate the problems in hand. If experimental illustrations of the 
 formation of valleys, deltas, shore cliffs, volcanoes, etc., can be given 
 in what has been called the " wet laboratory," following the sugges- 
 tions that have recently been made by some expert teachers, so much 
 the better. 
 
 Field excursions are also to be strongly recommended as a means 
 of giving reality to problems that might otherwise be regarded as 
 abstractions. It is particularly urged that the Exercises here pre- 
 sented should not be taken to replace field excursions ; but rather 
 that the principles illustrated in the Exercises should, as far as 
 
PREFACE vii 
 
 possible, be given additional illustration by systematic excursions in 
 the school district. It is in connection with such excursions that 
 the teacher may to best advantage first teach something of different 
 kinds of rocks, taken from their actual outcrops and selected to 
 illustrate varying degrees of resistance to weathering. Alluvial 
 deposits of gravel, sand, and clay should also be examined in field 
 study. Similarly, local weather observations should be undertaken 
 for the determination of temperatures, wind directions, changes 
 from clear to cloudy sky, rainfall, and so on. It will be of decided 
 advantage if the chief facts concerning the sun's seasonal change 
 of altitude and the associated changes in the points of sunrise and 
 sunset, and of the length of day and night, can be introduced in an 
 earlier year than the one in which these Exercises are studied. If 
 this is not conveniently possible, then the most important observa- 
 tions on the sun, as referred to in Exercise X, 4, 5, should be 
 made while the Exercises on land forms are studied ; and the Exer- 
 cises on the atmosphere should come near the close of the year. 
 
 It would truly be vastly better if, in the study of land forms, 
 actvial examples of all typical features could be made the subject 
 of systematic observation and description in the field by every 
 pupil, and if in the study of the temperatures, winds, and ocean cur- 
 rents of different parts of the world, the class could visit the regions 
 where the actual phenomena are observable ; but this is manifestly 
 impossible. Even the most favored school district does not include 
 a complete and well-ordered series of all the different kinds of land 
 forms which every student of Physical Geography should learn to 
 know ; indeed, such forms as it includes are often imperfect or com- 
 plicated examples of their kind, and it is not always possible for a 
 class to visit them on the day and hour when they are reached in the 
 regular progress of class work. Hence the necessity of presenting 
 the facts of our science largely through descriptions and imitative 
 illustrations. Nevertheless, so great is the power of the construct- 
 ive imagination on the part of young students that no serious 
 difficulty should be found in giving sufficient reality to the charts 
 
viii EXERCISES IN PHYSICAL GEOGRAPHY 
 
 of temperatures, winds, and currents, which graphically represent 
 average values of observed phenomena in Exercises X, XI, and 
 XIII ; or to block diagrams such as illustrate the series of volcanic 
 forms in Exercise VI ; or to maps such as illustrate the series of 
 shore-line forms in Exercise IX. 
 
 It is believed that great progress can be made when imitative 
 ideal illustrations are used as the basis of practical work under the 
 direction of a good teacher and in association with an appropriate 
 text-book. It goes without saying that, as already noted above, sup- 
 plementary illustrations are useful and helpful ; but the effort has 
 been made to provide so much of the essential material in this 
 Text and its Atlas that the labor of the teacher in supplementing 
 it shall be as light as possible. The careful performance of the 
 Exercises will lead the pxipil to observe, to describe, and to general- 
 ize ; to make inferences, to invent explanations, and to test theories ; 
 to express new ideas verbally and graphically. If the teacher is 
 patient and does not infringe too often on the pupil's right of dis- 
 covery, the pupil may make so much progress in these various 
 processes, and at the same time acquire so good a knowledge of a 
 great group of natural phenomena, that he will really be led to 
 make a beginning in the formation of scientific habits of thought. 
 
 The value of practical exercises in association with text-book 
 lessons may be illustrated by comparing the impression made upon 
 a student by the study of the important generalization, found ready- 
 made on a printed page, concerning the slopes of rivers and the 
 accordant junctions of branch and main streams, with the impres- 
 sion made upon him by having to develop the generalization himself 
 on the basis of a diagram of river profiles that he has constructed 
 with his own hands, as in Exercise I, 4. There can be little ques- 
 tion that the reality of the facts involved, and the truth of the 
 generalization that represents the relations of the facts, are best 
 apprehended through practical exercises ; but at the same time it 
 may well be that the wording of the generalization is not so clearly 
 given in the student's notebook as in the text-book, where it should 
 
PREFACE ix 
 
 therefore be carefully learned. Again, compare the strength of con- 
 viction regarding the features and relations of antecedent rivers, 
 according as they are studied in the paragraph of a text-book or 
 worked out by some such method as is offered in Exercise V, 8 ; 
 yet the paragraph in the text-book is a valuable supplement to the 
 results of the practical exercise. Compare the clearness and fullness 
 of conception of the phenomena of river capture and the associated 
 features, according as they are learned in a text-book or worked out 
 by means of illustrative diagrams showing the successive stages of 
 the processes involved, in some such way as is suggested in Exer- 
 cise IX, 4, 5, 6. Furthermore, the value of the careful analysis 
 of a problem and of the successive presentation of its parts in 
 systematically arranged diagrams is illustrated in Exercise XII. 
 There can be little question that such weather maps as those of 
 Plate 33, even though they are only ideal diagrams, will introduce 
 the problem of weather changes much better than can be done by 
 basing the work immediately on governmental weather maps. 
 
 Large generalizations must be given abundant and repeated oppor- 
 tunity to establish themselves in the mind. It is for this reason 
 that so many returns are made in Exercises I-IX to the problem 
 of the Geographical Cycle and to the systematic succession in the 
 development of land forms that it embodies. The explanatory 
 method that has long been employed in the study of the air and 
 the oceans is here introduced in the treatment of the lands as well, 
 where its thoroughgoing application constitutes the greatest advance 
 made in Physical Geography in the last century. But it is important 
 to remember that in all cases where land forms are described in 
 terms of the processes involved in producing them, the attention of 
 the geographer should be held primarily to the forms thus produced, 
 and given only secondarily to the processes to which they are due. 
 The systematic advance in the development of these forms, involved 
 in the scheme of the Geographical Cycle, has in recent years sug- 
 gested the use of such terms as young, mature, and old. The 
 scheme of the Cycle once being known, a valley and its stream may 
 
x EXERCISES IN PHYSICAL GEOGRAPHY 
 
 be described as " young " ; and the student is thereby most easily 
 led to apprehend all the characteristic features of the valley in 
 their natural occurrence. A group of mountains may be described 
 as approaching old age, and thus their essential features are most 
 easily brought to mind. A shore line may be described as mature, 
 because in this way the natural association of its parts is most con- 
 cisely indicated. There can be no question that the figurative use of 
 these organic terms has contributed greatly to the understanding 
 and the enlivenment of Geography. 
 
 The preference and experience of the teachers who use this Text 
 may be called upon to decide whether the Exercises shall, step by 
 step, precede or follow the study of a text-book. Good work may 
 be done in either order. References are frequently inserted in the 
 Text to several recent text-books, whereby the pupil is led at once 
 to explanations or definitions needed ; but, in general, the Exercises 
 are presented in so great detail that they are largely self-explana- 
 tory ; hence it is relatively immaterial whether they are used before 
 or after a text, as far as the difficulty of the work is concerned ; but 
 it is the belief of the author that the more scientific procedure is 
 to perform the Exercises first and to study the corresponding parts 
 of a text afterwards. In no case, however, is it intended that the 
 performance of the Exercises should replace the careful study of 
 a text- book, where many subjects for which no space can be found 
 in a laboratory manual are introduced and concisely explained and 
 defined. 
 
 > The author desires to thank his friends, Professor D. W. Johnson 
 of Harvard University, Mr. Charles R. Allen of the New Bedford 
 High School, Mr. Sumner W. Gushing of the Salem Normal School, 
 and Mr. W. L. W. Field of Milton Academy, who have patiently 
 and critically read the proof of the Text, with the result of con- 
 tributing many practical suggestions, greatly to the improvement of 
 the Exercises. The preparation of the Text and the Atlas has truly 
 been a long and laborious task ; but it is hoped that the labor thus 
 expended may not be without its reward in the way of giving some 
 
PREFACE xi 
 
 understanding and enjoyment of a great and delightful subject to 
 the many students who may not pursue it beyond an elementary 
 course in school or college, but who will frequently encounter it in 
 the world at large ; and in the way of providing a good foundation 
 for further work by those who wish to gain a scholarly acquaintance 
 with Geography in more advanced courses of study. 
 
 W. M. D. 
 HARVARD UNIVERSITY 
 
CONTENTS 
 
 PAGE 
 
 GENERAL INSTRUCTIONS 1 
 
 EXERCISES 
 
 I. THE VALLEY SYSTEMS OF THE LANDS 3 
 
 II. A COASTAL PLAIN 13 
 
 III. VALLEYS IN A COASTAL PLAIN 18 
 
 IV. PLATEAUS AND CANYONS 29 
 
 V. THE SCULPTURE OF MOUNTAINS 45 
 
 VI. VOLCANOES AND LAVA FLOWS 66 
 
 VII. THE RIVER CYCLE: WATERFALLS, RAPIDS, AND GRADED 
 
 RIVERS 80 
 
 VIII. THE RIVER CYCLE : RIDGES, VALLEYS, AND RIVER CAP- 
 TURES 88 
 
 IX. SHORE LINES 96 
 
 X. THE DISTRIBUTION OF TEMPERATURE 115 
 
 XI. THE PREVAILING WINDS OF THE WORLD 121 
 
 XII. WEATHER MAPS 129 
 
 XIII. OCEAN CURRENTS . 138 
 
 xii 
 
EXERCISES IN PHYSICAL 
 GEOGRAPHY 
 
 GENERAL INSTRUCTIONS 
 
 In performing the exercises here presented, each pupil should 
 have this Manual, the accompanying Atlas, and an ordinary Note- 
 book on his desk. 
 
 The Manual gives directions and questions. The answers to the 
 questions are to be found by studying the figures in the Atlas, and 
 then they are to be written in the Notebook. The directions usu- 
 ally require some simple drawing in the Atlas or Notebook. 
 
 References to the plates and figures of the Atlas are made by 
 two numbers ; the first number, in smaller type, refers to the 
 plate ; the second number, in larger type, refers to the figure. For 
 example, 6 12 means Plate 6, Figure 12. When a plate is referred 
 to without mention of any figure, the plate number is preceded by 
 the word Plate. 
 
 References to certain text-books, where explanations of various 
 topics may be found, are made by initial letters, followed by num- 
 bers which indicate the page and fraction (ninths) of a page in- 
 tended A dash after a page number indicates a longer reference 
 than usual. DE refers to Davis's Elementary Physical Geog- 
 raphy; DP, to Davis's Physical Geography; G, to Gilbert and 
 Brigham's Introduction to Physical Geography ; T, to Tarr's New 
 Physical Geography. U.S.G.S. means United States Geological 
 Survey. 
 
 General explanations within a section are often preceded by 
 the word NOTE. Explanatory phrases or words are inclosed in 
 
 1 
 
2 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 parentheses ( ). Bracketed [ ] sections and questions may be 
 omitted in a short course : [blue] and [red] suggest the use of 
 colored crayons, but they are not essential. 
 
 Scientific terms, when first used, are printed in italics ; they are 
 repeated in the final section of each exercise for review. 
 
 The letters N., E., S., W., meaning north, east, south, west, are 
 always followed by a period. Italic capital letters without a period 
 refer to the same letters in the figures of the Atlas. Such refer- 
 ences as DI-DI mean D l} Z> 2 , D 3 , -D 4 . Further explanation of the 
 figures is given at the beginning of the Atlas. 
 
 At the opening of a day's exercise write in the Notebook the 
 number and name of the exercise, and also the number of the sec- 
 tion at which work is begun. Enter the number of each question 
 before its answer. When a new section is begun, enter its number. 
 
 Head each question or direction carefully. Then turn to the 
 proper figure in the Atlas and study out the answer. Prepare the 
 answer clearly in the mind before writing it down ; then write it 
 accurately in the Notebook, and turn promptly to the next question. 
 
 When the directions require drawing in the Atlas or Notebook, 
 consider carefully what is to be done before doing it. See that 
 your pencil is sharp, or your pen clean, before drawing any lines. 
 
 Note that in Exercise V the plates are used in the following 
 order : 11, 12, 14, 13, 16 ; in Exercise VI, in order 17, 18, 20, 19, 15 ; in 
 Exercise VII, in order 21, 22, 23, 24, 26 ; in Exercise VIII, in order 
 27, 25, 28, 29. This arrangement is made so that the plates may be 
 easily compared with each other. By following the references to 
 plates and figures as given in the text there will be no difficulty in 
 finding the proper figure. 
 
EXERCISE I. THE VALLEY SYSTEMS OF THE LANDS 
 
 OBJECT. To explain the general effect of rain and rivers on the lands. 
 
 Preliminary. 1 1 is a bird's-eye view of a " block" of land, as if it 
 had been cut out of the earth's crust. North is toward the far end 
 of the block. The NW. and SE. corners of the block are trimmed 
 off to save space. A mountain range, M-^M^ rises in the middle 
 distance ; the land slopes from the mountain crest southward to the 
 seashore in the foreground, and northward to an elevated interior 
 basin in the background, from which no rivers escape to the sea. 
 A scale of miles is marked on the S. baseline of the block. The 
 scale of heights, on the W. side of the block, is exaggerated about 
 ten times as compared with the front horizontal scale. Numbers 
 (in large type) to the left of large dots on the rivers indicate 
 distances from the sea in miles; numbers (in smaller type) "to the 
 right of the dots and on the mountains indicate altitudes in feet. 
 This exercise uses 1, 2, 1-6. 
 
 1. 1. How high is the highest peak of the mountain range in 1 1? 
 About how far is it from the ocean ? In what direction does the 
 range extend ? In what general direction does river Y flow ? 
 2. Mark in light [blue] lines the path that rain water would fol- 
 low from A to the ocean; from B-, from C; from D t . 3. Does 
 the greater part of each path lie on a hillside (or mountain-side) 
 slope or along a valley bottom ? 4. Which paths unite on the 
 way to the ocean ? Draw similar lines to the ocean from D 2 -D 5 ; 
 from E^-Es. 5. Suppose a great many such lines were drawn ; in 
 what part of their paths would they be separate? in what part 
 united ? 6. How are streams formed ? 7. What is meant by 
 ground water, and how is it related to rain and to streams ? (DE, 
 234.3, 236.3 ; DP, 224.4, 226.8; G, 100.7, 103.6; T, 39.1, 59.5.) 
 
 3 
 
4 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 2. 1. Where two streams (or rivers) unite (as near E or E 5 ), do 
 they approach their junction at the same level, as in i 2, or at dif- 
 ferent levels, as in i 3 ? 2. In which one of 1 2 and 1 3 may the two 
 valley floors (and streams) be described as " joining at accordant 
 levels " (or as making an " accordant junction ") ? in which one 
 as "making a discordant junction" (or a "hanging junction") ? 
 3. Do the valleys of 1 1 generally show accordant junctions or dis- 
 cordant (hanging) junctions ? 4. Mark [blue] lines along all the 
 streams which unite in 1 1 to form river V. 5. What name is given 
 to a system of water courses consisting of a river with all its 
 branches and side streams ? (DE, 241.5 ; DP, 230.3 ; G, 36.4.) 
 6. What similar name may be given to all the valleys from which 
 the streams unite to form a single river ? 7. How many large 
 valley systems are completely shown S. of the mountain crest in 
 1 1 ? 8. Which system is the largest ? How long is its longest 
 river ? 
 
 3. 1. Begin at F in 1 1 and draw a broken [red] line to inclose 
 all the land surface from which the rainfall is discharged or drained 
 by the large river V. 2. Over how many prominent peaks (more than 
 4000' high) does the inclosing line pass ? 3. Where does it follow 
 a sharp-crested ridge ? abroad, rounded ridge? a narrower rounded 
 ridge ? Draw a similar line for the smaller river F. 4. What name 
 is given to the drainage areas thus inclosed? to the line sepa- 
 rating the drainage areas ? (DE, 241.9 ; DP, 230.6 ; G, 36.3-5.) 
 5. Draw a dotted [red] line inclosing the valley or stream basin A ; 
 inclosing B ; Z> 3 . 6. Such lines, where they do not follow the main 
 divides, may be called subdivides. Why ? 7. Do spurs (branches 
 of the larger ridges) usually form divides or subdivides ? 
 
 4. 1. What is the altitude of river F 4 mi. from its mouth ? 
 At what distance from its mouth is the altitude of river F 160' ? 
 What is the altitude of the NE. branch of river V at 14 mi. from 
 its mouth ? 2. In 2 4 the baseline represents sea level ; the spaces 
 between the vertical lines represent distances of two miles ; how are 
 altitudes indicated ? 3. Mark on these vertical lines (beginning at 
 
THE VALLEY SYSTEMS OF THE LANDS 5 
 
 the right) the altitudes for successive points on river VC. 4. Draw 
 a curve through the points thus marked. 5. What does this curve 
 represent ? It may be called the profile of river VC. 6. Does the 
 profile show the true slope of the river or an exaggerated slope ? 
 Why? 7. Mark a cross (x) on this profile where stream B joins 
 river VC. From this cross construct the profile of stream B. 8. Do 
 the same for river E 2 ; for stream A. 9. What part of each profile 
 is steepest ? least steep ? 10. In what part of the river system 
 (near headwaters or mouth) do the streams make most of their de- 
 scent (OT fair) toward sea level? 11. What is (roughly) the descent 
 or fall of the headwater streams in feet per mile ? of the lower 
 course of river V? NOTE: Large rivers, like the Mississippi, flow 
 in their lower course with a fall of only an inch or two in a mile. 
 
 12. In what part of 1 1 will the streams run fastest ? slowest ? Why ? 
 
 13. Where are the streams of smallest volume ? the rivers of great- 
 est volume ? Explain. 
 
 5. 1. What effect is (usually) produced on stream (or river) beds 
 by the action of running water ? Explain (DE, 136.2, 245.7 ; DP, 
 103.7 ; G, 32.1, 35.2 ; T, 52.7). 2. What change will this action 
 gradually produce in the stream and river profiles of 1 1 ? (See 2 4.) 
 3. What change has it already produced ? 4. How does it happen 
 that the slope of each river leads it so accurately to sea level at the 
 river mouth ? 5. In this connection, how can use be made of the 
 phrase river erosion? of the term baselevel? NOTE : The ocean sur- 
 face may be called the general baselevel of erosion for the continents, 
 because it is the " level base," closer and closer to which the proc- 
 esses of erosion tend to wear down or degrade the land. 6. In what 
 part of the V river system can the valleys still be most worn down 
 or degraded ? Why ? 7. Will long-continued river action tend to 
 change 1 2 to i 3, or 1 3 to 1 2 ? 8. By what process do you think the 
 accurate accordance of the branching valleys with each other, and 
 of the main valley with sea level, in 1 1 has been brought about ? 
 9. Has the production of the valley system, with its accordant ar- 
 rangement of parts, probably required a very long or a short time ? 
 
6 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 6. 1. What is the effect of weather changes, acting for a long 
 time, on a land surface ? Explain briefly. (DE, 134.8 ; DP, 99.8 ; 
 G, 78.8; T, 38.6.) 2. How may the terms weathering, rock ivaste 
 (or land waste), and soil be used in connection with valley A (or 
 other parts) of i 1 ? 3. Rain water runs down hillside slopes in wet 
 weather, forming little rills. 4. How will the wet-weather rills act 
 on the hillside waste (or soil) ? 5. What change will thus be made 
 in the size of the hills ? 6. Will this change take place rapidly or 
 slowly ? 7. What is the chief source of the water in the streams 
 during dry weather ? 8. Why do most streams and rivers become 
 (comparatively) clear when running slowly at times of low water 
 in dry weather, and muddy or turbid when running rapidly at 
 times of flood in wet weather ? NOTE : The destructive processes 
 caused by weather changes and stream (river) action may together 
 be given the general name erosion. 9. State some of the effects 
 already produced by erosion in 1 1 near A ; near D l near E z . 
 10. State some effects yet to be produced near the same points. 
 
 7. 1. Is a greater or less stream velocity needed, to wash along, 
 or transport, coarse waste (bowlders and gravel) than fine waste 
 (sand, in small grains ; silt, in very small particles) ? 2. In what 
 part of its system can a river transport both coarse and fine waste ? 
 only the finer waste ? 3. Is a river a better transporter at time of 
 flood or of low water ? 4. What happens to coarse, angular waste 
 as it is rolled along the bed of a rapid stream ? 5. To what part 
 of 1 1 will the waste from the V valley system be transported ? 
 of the F valley system ? 6. Why is some of the waste laid down, 
 or deposited, near the river mouths ? 7. What is the form of the 
 land that has been made of rock waste deposited by rivers near 
 their mouths ? 8. What name is given to such forms ? Mark them 
 with [blue] dots in 1 1. 9. Do these forms contain all the waste 
 that has been brought to the river mouths from the headwaters 
 and slopes of the valley systems ? 10. Where is the rest of 
 the waste deposited ? [11. How is some of this deposit indicated 
 in the S. block face of 1 1 ? 12. How has it been spread out ? 
 
THE VALLEY SYSTEMS OF THE LANDS 7 
 
 13. Why is it deposited in layers or strata? 14. Has each layer 
 or stratum a smooth or a rough surface ? 15. Why does the sea- 
 bottom deposit vary in thickness, as shown on the S. face of the 
 block ?] 16. State the general principle thus illustrated concern- 
 ing the removal of land waste. (DE, 136.1 ; DP, 103.6 ; G, 59.8 ; 
 T, 52.5.) 
 
 8. [1. Suppose that the processes of erosion, transportation, and 
 deposition continue many hundred thousand years. 2. Draw in 2 4 
 a broken line to show the profile which would then be followed 
 by river VC (begin the river head at 2600') ; a dotted line to show 
 the profile at a still later time (begin the river head at 1800'). 
 XOTE : The river profile must have a seaward slope, less steep 
 toward the mouth than toward the head; it must not be drawn 
 beneath sea level. 3. Which part of the river shows the greatest 
 change in these profiles ? the least change ? Why ? 4. Will the 
 river then run faster or slower than now ? transport more or less 
 waste than now? Why ? 5. Imagine that the processes of erosion, 
 transportation, and deposition have already been at work many 
 hundred thousand years before the hills and valleys gained the 
 form shown in 1 1. 6. Draw in 2 4 a profile for an early stage of 
 river VC ; for a still earlier stage. (The dot-and-dash line in 2 4 
 may be taken to represent the original profile of the land, before 
 the valleys were eroded. Some early river profiles are partly indi- 
 cated by three-dot lines.) 7. Compare the profile for 1 1 with the 
 earlier profiles, as to the slope of the main river (near middle 
 course) ; as to the slope of headwaters. Explain the differences. 
 8. On which profile would the main river (middle course) flow 
 fastest ? slowest ? erode its bed fastest ? slowest ? [9. Explain 
 as fully as you can.] 10. Answer the same (four) questions for 
 the headwaters. [11. Explain.] 12. As the river profiles are 
 worn lower and lower, what happens to the hillsides and hilltops ?] 
 
 9. If 8 is omitted, 9, 10 should also be omitted. [1. In 2 6 MM 
 is a profile (on a larger scale than 1 1) across one valley and two 
 ridges about ten miles from the sea. A similar cross profile of the 
 
8 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 same valley for an earlier stage of its history is indicated by YY; 
 for a later stage by 00. Draw a profile for a stage between Y and 
 M ; another, between M and 0. 2. In which stage has the valley 
 the narrowest floor and the steepest sides ? Why ? 3. In which 
 stage the widest floor with the most gently sloping sides ? Why ? 
 4. Draw several additional profiles (one earlier than YY, one later 
 than OO). 5. Describe the form that the district would have when 
 all its valleys come to have cross profiles like the latest profile. 
 6. Why may such a district be called a peneplain ? What is the 
 relation of a peneplain to its baselevel ? (DE, 206.2 ; DP, 152.5 ; 
 G, 161.4 ; T, 58.5.) 7. In which stage are the valleys deepened 
 faster than the hills are worn down ? In which stage are the hills 
 worn down faster than the valleys are deepened ? [8. Explain as 
 fully as you can.] 9. In which stage are the hills worn down 
 most slowly ? Why ? 10. Why are the hills worn down faster in 
 this stage than the valleys are then deepened ?] 
 
 10. If 9 is omitted, omit 10 also. [1. In which profile of 
 2 4 might the river be appropriately called young ? old ? 2. In 
 which cross profiles of 2 6 might the valley be called young ? old ? 
 3. What term (indicating stage of development) might be as appro- 
 priately applied to the cross profile of the valley MM, 2 6 ? to the 
 river VC,il? (DE, 269.8 ; DP, 250.6 ; G, 58.3 ; T, 57.3.) 4. If an 
 old land surface or peneplain were very slowly given a greater 
 altitude by a broad uplift of its region, what change would take 
 place in the behavior of its rivers ? 5. Why might the rivers then 
 be described as " made young again " ? or as rejuvenated ? or as 
 revived ? 6. What event presumably took place in the region of 1 1, 
 before young valleys could be eroded ? Why ? NOTE : The long 
 period of time in which the general processes of erosion will wear 
 down any uplifted region to a low peneplain may be called a cycle 
 of erosion. The features of the land surface in the early, inter- 
 mediate, and late stages of a cycle may be spoken of as young, 
 mature, and old. 7. Compare young and old rivers, as to slope ; as 
 to velocity ; as to the power of transportation ; as to rate of valley 
 
THE VALLEY SYSTEMS OF THE LANDS 9 
 
 deepening. 8. Compare the rivers of 1 1 with young rivers and 
 with old rivers, as to form of profile (see 24); as to depth of 
 valleys (see 2 6) ; as to rate of valley deepening ; as to amount 
 of waste, or load, received from the valley sides ; as to texture 
 (coarseness or fineness) of waste received. 9. Compare the valleys 
 of a river system in its young, mature, and old stages, as to depth 
 (below the neighboring hills) ; as to narrowness or openness ; as 
 to slope of valley sides. NOTE : The relief of a land surface 
 is the general difference of altitude between the valleys and the 
 neighboring hilltops, or the height of the hills above the neighbor- 
 ing valleys. 10. In what stages of a cycle of erosion is the relief 
 of moderate measure (see 26) ? of greatest measure ? 11. In what 
 stage of a cycle of erosion might the rivers be imagined as saying 
 to one another, "Our work is before us"? "Our work is well 
 advanced"? "Our work is (nearly) done"? 12. Describe briefly 
 the " life history of a river system."] 
 
 11. 1. Describe the form of the land margin at N and N lf 1 1. 
 Compare it with the margin near the river mouths. 2. How have 
 the cliffs at N and ^ been produced ? (DE, 136.8 ; DP, 104.3 ; G, 
 309.9 ; T, 211.3.) 3. Why do the sea cliffs not extend all along the 
 shore ? 4. Why are they higher in some places than in others ? 
 5. Why are some of the cliffs not now at the shore line ? 6. What 
 becomes of the land waste that is weathered from the cliff face 
 or worn from the cliff base ? NOTE : The destructive processes 
 going on along the cliff base and on the shallow sea bottom near 
 shore may be called marine erosion, in contrast to the general 
 erosion of the land surface, which may be called subaerial erosion 
 (the work of weathering, and of rills, streams, and rivers being 
 here included). 7. Which process, marine erosion or subaerial 
 erosion, works on the greatest amount of land surface in 1 1 ? 
 8. Which process probably gives the greatest amount of waste to 
 the sea ? 
 
 12. 1. Draw a [red] line in 1 1 dividing the surface that is 
 drained to the ocean from that drained to the interior lake. 2. The 
 
10 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 lake occupies the lowest part of an inclosed or interior basin. Has 
 the lake an outlet ? 3. What is the (local) baselevel for the streams 
 that flow into the lake ? 4. Where do these streams deposit the waste 
 that they bring from their upper valleys ? 5. As time passes, will 
 the waste-covered plain bordering the lake be worn lower (degraded) 
 or built higher (aggraded)? 6. How will this change affect the base- 
 level of the interior basin ? 7. How does the water, supplied by the 
 inflowing streams, escape from the lake? (DE, 284.1; DP, 305.1 ; 
 T, 163.7.) 8. If you were in camp on the lake shore near a stream 
 mouth, where would you get your drinking water ? Explain. 
 
 13. 1. 2 5 is a map (roughly) representing the SW. part of 1 1, 
 from the mountain crest to the shore line. Print the letters V and 
 Y on 2 5 in places corresponding to V and F in 1 1 ; also the let- 
 ters C, M s , M 1} D 1} D 3 , Dr , N. 2. In 25 how are the streams rep- 
 resented ? the main divides and the subdivides ? the borders of the 
 flat valley floors ? 3. Draw a broken [red] line inclosing the drain- 
 age basin of river F. 4. What is (about) the length of river F? the 
 breadth of the ridge between the upper parts of valleys Y and V? 
 
 5. In what direction would wet-weather rills flow at A ? at B ? 
 
 6. What relation exists between the direction of rill flow and the 
 direction of the numerous lines near A and B ? NOTE : These lines 
 may be called " down-slope lines," or hachures (pron. hashures). 
 They are drawn in belts around the slopes ; they should be long and 
 light on gentle slopes, shorter and darker on steep slopes. [Hachures 
 should seldom be drawn perfectly straight or precisely parallel to 
 each other ; they should usually be a little curved, and more or less 
 divergent or convergent downhill. In the upper part of 2 5 the 
 hachures are drawn somewhat darker and closer together on the E. 
 and SE. slopes, so as to give more effect of relief.] 7. What is the 
 arrangement of the hachures at the head of a valley ? around the 
 end of a spur ? 8. What process, described in 6, takes place along 
 the down-slope lines represented by the hachures ? [9. Shade with 
 carefully drawn hachures the upper part of the valley in which D 3 
 or D 5 lies ; one of the spurs between D 3 and Z> 5 . (The three-dot lines 
 
THE VALLEY SYSTEMS OF THE LANDS 11 
 
 may be used to guide the hachure belts.) 10. Draw additional 
 hachures in the NW., SW., or NE. parts of 2 5.] 
 
 14. 1. How many miles are shown on the scale at the bottom of 
 25? 2. How can you measure distances on the map, 2 5, by this 
 scale ? 3. Why may such a scale be called a linear scale ? 4. Be- 
 ginning at on the linear scale, mark points an inch apart along 
 the scale ; how many miles are represented by an inch on the scale ? 
 5. Complete the sentences : " The scale of 2 5 is - miles to an 
 
 inch"; "In the front scale of 1 1, (fraction) of an inch 
 
 represents a mile." 6. How many inches make a mile ? 7. What 
 fraction of an actual distance would represent it on a map of which 
 the scale is a mile to an inch ? on a map with a scale of two miles 
 to an inch ? [half a mile to an inch (or two inches to a mile) ? ten 
 miles to an inch?] on 25? 8. About what scale is represented by 
 the fraction * ? - ? r ' 9 ' ? ' ? l ?"| q Wh v mav 
 
 U i;LVil ' 125,000 ' L250,IKH) " 1,<ICU,UUU ' 30,<IOO ' 10,000 ' J "' Y * J Ud V 
 
 any one of these fractions be called a fractional scale ? 
 
 15. [1. Over a century ago John Playfair, of Edinburgh, Scot- 
 land, wrote as follows : " Every river appears to consist of a main 
 trunk, fed from a variety of branches, each running in a valley pro- 
 portionate to its size, and all of them together forming a system of 
 valleys, communicating with one another and having such a nice 
 [accurate] adjustment of their declivities that none of them join the 
 principal valley either on too high or too low a level ; a circum- 
 stance which would be infinitely improbable.if each of these valleys 
 were not the work of the stream that flows in it. ... When the 
 usual form of a river is considered, the trunk divided into many 
 branches which rise at a great distance from one another, ... it 
 becomes strongly impressed upon the mind that all these channels 
 [valleys] have been cut by the waters themselves ; that they have 
 been slowly dug out by the washing and erosion of the land ; and 
 that it is by the repeated touches of the same instrument that this 
 curious assemblage of lines [valleys] has been engraved so deeply 
 on the surface of the globe." (Quoted from Illustrations of the 
 Huttonian Theory of the Earth, Edinburgh, 1802, pp. 102, 103.) 
 
12 
 
 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 2. What facts, mentioned in the above quotation, are illustrated in 
 this exercise ? 3. What suppositions or theories presented in the 
 quotation are supported by this exercise?] [4. The illustration be- 
 low represents a model which shows mountains bordering the sea. 
 Name some features there represented which have been studied in 
 this exercise.] 
 
 16. Define the following terms : 1, ground water ; 2, river 
 system, valley system, accordant and discordant (or hanging) valley 
 junctions ; 3, drainage area, ridge, peak, spur, river basin, divide 
 or water parting, subdivide ; 4, river profile ; 5, river erosion, 
 baselevel of erosion, degrade; 6, weathering, rock waste, land waste, 
 soil, rill ; 7, bowlders, gravel, sand, silt, transport, deposit, delta, 
 [stratum, strata] ; [ 9, peneplain ; 10, revived river, cycle of ero- 
 sion, texture of river load, relief ;] 11, sea cliff, marine erosion, 
 subaerial erosion ; 12, interior basin, aggrade ; 13, hachures ; 
 14, linear scale, fractional scale. 
 
EXERCISE II. A COASTAL PLAIN 
 
 OBJECT. To represent part of a coastal plain on a map, and to describe 
 the form thus represented. 
 
 Preliminary. The numbers on si show the altitude or height 
 above sea level, in feet, of many points (dots near the numbers) in 
 a district bordering the sea. The numbers preceded by a negative 
 sign (as 15) indicate a negative altitude ; that is, a depth below 
 sea level. This exercise uses 3 1, 3 2 (and 4 8) ; [also 6 15 and 35 1]. 
 
 1. 1. Draw a light (pencil) line in 3 1 separating all parts of 
 the surface that are higher than 100' from all parts that are lower 
 than 100'. This line must pass through all points marked 100 ; mid- 
 way between points equally above and below 100, such as 105 and 
 95 ; nearer to 95 than to 110 ; nearer to 105 than to 90. 2. Ex- 
 plain the preceding rules. 3. Draw similar lines separating parts 
 higher and lower than 200'; than 300'; than 0'. Mark the last 
 line heavier than the others. What does this line represent ? 4. Do 
 the same for 400', 500', 600'. [Intermediate lines for 50', 150', 
 250', etc., may also be drawn.] 
 
 2. 1. Would you ascend or descend (go uphill or downhill, up- 
 slope or down-slope) in walking from K to A ? from G to H ? from 
 H to F? from C to E ? along the 100' line ? along any of the lines 
 that you have drawn ? 2. Do the (pencil) lines follow slanting or 
 level paths ? Lines of this kind are called contour lines, or contours. 
 3. What is the (estimated) difference of altitude between H and G ? 
 between B and A ? between two adjoining contour lines ? 4. The 
 last difference is called the contour interval. W T hy ? 
 
 3. 1. Lay a strip of paper on 3 1 along the line AB ; mark short 
 lines on the edge of the strip opposite A and B and print these let- 
 ters +1 'ere; mark dots on the strip edge at the contours of 0', 100', 
 
 13 
 
14 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 200', [250'], 300', and 600', and indicate by figures the altitude at 
 each contour dot. 2. Now place the strip along the baseline of 3 2 ; 
 lay off the contour dots between A' and B', and indicate the alti- 
 tudes to which the dots refer. 3. Copy the vertical scale at A' on 
 the edge of a slip of paper ; lay the slip square across the baseline 
 A'B' at the successive contour dots, and mark off points at the alti- 
 tudes of the corresponding contours above A'B'. 4. Draw a line 
 through the points thus determined, and prolong it to the right of 
 B'. 5. What does this line represent ? It is called a profile line, or 
 profile. 
 
 4. 1. If you followed the path of the profile AB (or any similar 
 path) across 3 1, on what part of it would you find a steep slope ? 
 a gentle slope ? 2. How is the difference of slope indicated by the 
 contour lines ? Explain. 3. Make a general rule to show how the 
 spacing of contour lines indicates steep and gentle slopes. 4. Draw 
 some short lines (about " long) to show the direction of slope 
 (downhill) near G ; some fainter and longer lines (about " long) 
 to show the slope near H\ near C. 5. The down-slope lines may 
 be called hachures (pron. hashures). 6. What is the relative direc- 
 tion of contours and hachures ? 7. Draw a dotted line in 3 1 sep- 
 arating the part of gentle slope from the part of steeper slope. 
 NOTE : In the district here represented all the land higher than 
 the dotted line is supposed to be made of resistant rocks covered 
 with a stony soil ; all the land of less altitude, of layers or strata 
 of sand, gravel, clay, etc. ; each layer or stratum slants gently sea- 
 ward with the slope of the surface, and contains shells of marine 
 animals similar to those living in the neighboring ocean. 
 
 5, 1. Describe the general form of the district in 3 1. 2. What 
 is the origin of the gently sloping plain? (DE, 145.2; DP, 119.9; 
 G, 151.8 ; T, 72.7.) What statements in 4 indicate this origin ? 
 3. Which part of the plain first rose above the sea? 4. What is 
 the present altitude of the former shore line ? the breadth of the 
 plain ? the slope (or fall) of the plain in a mile ? the direction of 
 the slope (north is at the top of the map) ? 5. Print carefully on 
 
A COASTAL PLAIN 15 
 
 the proper parts of si the words : COASTAL PLAIN, OLDLAND, 
 OCEAN, [FORMER SHORE LINE, NEW SHORE LINE]. 6. Draw in 32 a hori- 
 zontal line showing the sea level as it formerly appeared. 7. What 
 was then the altitude of A ? of G ? the depth of F? of L ? 8. How 
 great an uplift of the land with respect to the sea has taken place in 
 laying bare the coastal plain of 3 1 ? 9. What would have been the 
 breadth of the plain if the uplift had been 150' (see 3 2) ? 300' ? 
 10. Make a general statement showing the relation between the 
 amount of uplift along the border of a continent and the breadth 
 of the resulting coastal plain. [11. Expand this statement so as 
 to include also the effect of greater or less slope of the sea bottom 
 before uplift.] 12. What can you say as to the cause of such 
 regional " uplifts " as are here considered ? (DE, 158.4 ; DP, 
 132.2.) NOTE : It is important to remember that such movements 
 of the earth's crust as are here considered take place very slowly, 
 and require thousands and thousands of years. 
 
 6. 1. Imagine that the region of 3 1 had not been uplifted, and 
 that you stood at G. The view before you might then have been 
 described as follows : " I see a rather steep hillside sloping south- 
 ward to the seashore, which extends about east and west." 2. If 
 you were at G after the uplift of the region, how would you describe 
 the view ? [3. Examine 4 7 of the next exercise. What is its con- 
 tour interval ? 4. In what direction does its coastal plain slope ? 
 5. How wide is it at the E. end of the map ? at the W. end ? 6. What 
 is the greatest altitude of the oldland there shown ? 7. What is the 
 altitude of the former shore line at the E. end of the map ? at the 
 W. end ? 8. In which part of this plain was the uplift greatest ? 
 9. Why does the breadth of the plain vary ? 10. What would be 
 its probable breadth 30 mi. farther E. ? 30 mi. farther W. ? 11. In 
 which direction, and how far, would you have to go to find the 
 breadth of the plain reduced to nothing ? Explain.] 
 
 7. 1. Describe the forms shown in 4 8, using the terms that 
 you have printed on 3 1. NOTE : 4 8 is from a photograph of a 
 narrow coastal plain (looking NE.) in a bay on the W. coast of 
 
16 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 Scotland ; it shows the natural appearance of a small example of 
 such forms as are drawn in the outline maps and diagrams of this 
 exercise. 2. The inner border of this coastal plain is 25' above 
 sea level. How much elevation of the land (or depression of the 
 sea) must have taken place when the plain was laid bare ? [3. Draw 
 a map, in hachures or contours, of the district shown in 4 8. 
 (Assume such heights and distances as seem appropriate, and 
 choose your own scale for the map.)] [4. Examine 6 15. What 
 part of what state is there shown ? What ocean bounds it on the W. ? 
 5. Locate it on Plate 40. NOTE : The map, 6 15, is copied from 
 parts of two contour maps published by the United States Geolog- 
 ical Survey in Washington, D.C. It exhibits the natural irregular- 
 ities of the oldland hills and the coastal-plain rivers which are 
 shown in simplified form in these exercises. 6. From what original 
 maps is 6 15 taken ? 7. What is its scale ? its contour interval ? 
 8. What length of the coastal plain is there shown ? what breadth ? 
 what is the altitude of its inner border ? the average slope (feet 
 per mile) to the sea? the direction of the slope? 9. How many 
 streams run from the oldland toward the ocean ? NOTE : Several 
 streams cannot reach the ocean directly, because of a long sand 
 reef that has been formed along part of the shore by the sea waves 
 and currents. 10. Mark a point (x) on the oldland from which 
 you could get a good view of the plain. What is the altitude of the 
 point ? its distance from the inner border of the plain ? from the 
 ocean? 11. Describe the view from this point, looking W., NW., 
 and SW.] 
 
 8. [1. The lowering of lake waters may produce a lacustrine 
 coastal plain, similar in many respects to the marine coastal plains 
 thus far described. Explain. 2. The land next S. of lake Erie pre- 
 sents an example of a lacustrine coastal plain, part of which is 
 shown in 35.1. 3. In what state does this example occur? Locate 
 it on Plate 40. 4. The base of the gently sloping oldland is at 
 an altitude of (about) 790'; shade the oldland lightly (in pencil). 
 5. How broad is the plain ? What is its average fall in feet per 
 
A COASTAL PLAIN 
 
 17 
 
 mile ? (Do not include the fall of the shore-line cliff.)] [6. Draw 
 on a scale of 10 mi. to an inch, with 50' contour interval, a contour 
 map of part of a coastal plain, about 25 mi. wide, sloping a little N. 
 of E., with the former shore line at (about) 250' altitude and the 
 oldland reaching 650', 5 or 6 mi. W. of the former shore line. 
 7. What is the average fall of the coastal plain? of the oldland?] 
 [8. The illustration below represents a model which shows a dis- 
 trict bordering on the sea. What features, there represented, have 
 been studied in this exercise?] 
 
 9. Define the following terms : 2, contour line, contour inter- 
 val j 3, profile ; 4, stratum, strata ; 5, coastal plain, oldland ; 
 [ 8, lacustrine coastal plain]. 
 
EXERCISE III. VALLEYS IN A COASTAL PLAIN 
 
 OBJECT. To learn the forms produced in coastal plains by rivers and 
 streams. 
 
 Preliminary. If a coastal plain, like the one shown in 3 1 of the 
 preceding exercise, were followed for a few miles parallel to the 
 shore line, a river might be found flowing from a deep valley 
 in the oldland and crossing the plain in a shallow valley to the 
 sea. 4 1 is a block diagram (bird's-eye view) of such a river cross- 
 ing a narrow coastal plain. (The NW. and SE. corners of the block 
 are cut off to save space.) Level lines, like contours, are drawn on 
 the plain, slanting lines on the oldland and on the valley side. 
 The numbered lines show the altitude of different parts of the 
 plain, valley, and oldland. The heights are much exaggerated com- 
 pared to the horizontal distances. The smooth valley floor may be 
 covered with water when the river is in flood, and hence may be 
 called the river flood plain. NOTE : The more natural appearance 
 of part of such a plain and valley is shown in 4 1 a : here the up- 
 land is divided into cultivated fields, and the valley side is covered 
 with trees. This exercise uses 4, 5, c, 1-15 (and 3 6) ; [also 35 1-4]. 
 
 1. 1. Which is higher, the coastal plain or the flood plain in 
 4 1 ? How much higher at G ? at // ? at F ? 2. What is the height 
 interval between the numbered contour lines ? 3. Look at the 10' 
 contour line at G. Does it turn N. or S. in passing from the E. 
 part of the coastal plain to the E. side of the valley ? 4. Why does 
 it turn in this way ? 5. How does it turn at // from the valley side 
 to the valley floor ? 6. How do you suppose it turns from the val- 
 ley floor to the W. valley side ? from the W. valley side to the 
 W. part of the plain at K? 1. Complete the 20' contour on the 
 E. valley side. 
 
 18 
 
VALLEYS IN A COASTAL PLAIN 19 
 
 2. 1. 4 2 is a map of the same coastal plain. The top and bottom 
 of the valley sides are marked with dotted lines. 2. Complete the 
 10' and 20' contours on the W. side of the valley ; draw some hachures 
 on the valley side ; draw the 15' and 25' contours. 3. Notice that the 
 contours bend as they pass from the plain to the valley sides. Com- 
 pare the direction of this contour bend with the direction of slope 
 of the plain ; with the direction of river flow. 4. Notice that the 
 contours make a loop in crossing the valley. Is the loop open up- 
 stream or downstream ? 5. Does the space within the loop become 
 wider upstream or downstream ? [6. Why ?] 7. What is the altitude 
 of the plain at C ? at D ? of the valley floor at E ? at F ? 8. What 
 point on the river is at the same altitude as point K (or G) on the 
 plain ? as point B ? 9. What points on the plain are of (about) 
 the same altitude as F on the river ? as E ? 10. How deep below 
 the coastal plain is the valley floor at E ? at F? 11. If a village 
 were at F, its people might speak of the neighboring coastal plain 
 as "the upland." Why ? [12. Describe the view from A, looking 
 W. ; looking SW. ; from B, looking E. ; looking N.] 
 
 3. 1. Compare the direction in which the plain slopes with the 
 general direction in which the river flows. 2. What reason can you 
 give for thinking that the direction of river flow is a consequence 
 of (or is consequent upon) the slope of the plain ? NOTE : Rivers 
 whose general course has been determined by the original (or initial) 
 slope of the land, as given by uplift, may be classed as consequent 
 rivers; the valleys of such rivers may be classed as consequent val- 
 leys. 3. 4 3 is a profile across the plain from the oldland to the 
 sea. The broken line L'R'F' indicates parts of the river (and valley 
 floor) of 4 2 (or 4 1). 4. Complete the broken line by a [blue] line, 
 and prolong it to the sea. 5. Why is the valley deeper at F' than 
 at E' ? 6. How do you suppose the valley was formed ? 7. What 
 controls the depth to which the valley can be eroded ? (DE, 145.8, 
 254.1-7; DP, 120.5; T, 55.8.) (Use the term baselevel in your 
 answer.) 8. How is the baselevel of the plain indicated in 43? 
 9. Was the valley formerly deeper or less deep than now ? 10. Can 
 
20 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 the depth of the valley be much more increased at E' ? at V ? 
 11. What is the average fall per mile of the oldland slope ? of 
 the coastal plain ? of the river from .F to the sea ? 12. Which is 
 the steepest ? least steep ? Why ? NOTE : Most coastal plains are 
 much broader than those here shown ; the slope of their surface 
 toward the ocean is often extremely gentle and may be less regular 
 than it is indicated in the diagrams of this exercise. 13. What 
 effect would this have on the straightness or crookedness of conse- 
 quent rivers across such plains ? 14. To what class do the streams 
 on the coastal plain of 6 15 belong ? 15. Is their direction of flow 
 as regular as that of the stream in 4 2 ? Explain. 
 
 4. [1. What reason can be found in 4 1 or 42 for saying, "The 
 river has (practically) ceased deepening its valley from F to the 
 ocean " ? in 4 2 (or 6 14) for saying, " The river is still (actively) 
 deepening its valley in the part upstream from F"? 2. Why has 
 the river not worn down its course between F and the ocean to a 
 gentler slope, and thus given that part of its valley a greater depth? 
 [The following questions, 3-8, will aid in answering the preceding 
 one. 3. If a river has no slope, what velocity can it have ? 4. If 
 it has no velocity, how much rainfall can it discharge from its drain- 
 age basin, and how much land waste (gravel, sand, silt) can it sweep 
 along or transport ? 5. The river here considered may have head- 
 waters like those of 1 1. Will it or will it not have some rainfall to 
 discharge, and some load to transport in its lower course ? 6. Must 
 it then still have some slope near its mouth ? 7. Explain the state- 
 ments : "When a river has a greater velocity than is needed in 
 transporting its load of waste, it will erode its bed (valley bottom) 
 and thus lessen its slope and decrease its velocity"; "A river can- 
 not erode its bed to so small a slope as to lose the velocity needed 
 in transporting its load of waste." 8. To what parts of 4 2 do these 
 statements apply ?] 9. How can the term graded river be used in 
 this connection ? (DE, 254.1 ; DP, 237.6 ; T, 56.9.) 10. Which parts 
 of the river in 42 are already graded ? not yet graded? 11. Answer 
 the same questions (as well as you can) for the rivers V and F, 1 1. J 
 
VALLEYS IN A COASTAL PLAIN 21 
 
 5. [1. When the valley sides are examined closely near the inner 
 border of a coastal plain, such as is shown in the small block dia- 
 gram, 6 14 (larger scale than 4 1), the hard rocks of the oldland 
 are seen to extend a moderate distance down the valley, under the 
 overlapping layers, or strata, of the coastal plain. 2. Draw a [red] 
 line on the valley side of 6 14 separating the coastal-plain strata 
 from the underlying extension of the oldland rocks. 3. Is this 
 line horizontal or sloping ? 4. Compare its slope with the slope of 
 the river ; of the coastal plain. NOTE : The underground exten- 
 sion of the oldland rocks usually has a surface of much less 
 slope than is here shown. 5. Draw broken [red] lines along the 
 valley side to show the edges, or outcrops, of the coastal-plain 
 strata there exposed. 6. Do the coastal-plain strata slope toward 
 the oldland or toward the ocean ? 7. Does their total thickness 
 increase toward the oldland or toward the ocean ? 8. Can the 
 sfriu-ture (arrangement and composition of layers, etc.) of a coastal 
 plain be better studied in a district without valleys, like 3 1 of 
 Exercise II, or along the valley sides of a district like that of 4 2 (or 
 6 14) of this exercise ? Why ? 9. What is the structure of a coastal 
 plain ? 10. What is the relation of the uppermost layer to the 
 original siirface of the plain ? 11. Draw in 6 14 some [red] hachure 
 lines on the E. side of the valley at A, B, and C. 12. Which ones of 
 these lines have a steeper slope near the bottom than near the top ? 
 Why ? 13. Why is the valley so much narrower and less deep at 
 A than at B ? 14. In 4 3 what is the average fall per mile of the 
 river from F' to the mouth ? from V to F' ? 15. Which part is 
 steeper ? Why ? 16. In which part do cascades and rapids occur ? 
 17. Which part could be most easily followed by boats ? 18. Sup- 
 pose that all the rivers which cross this coastal plain are like the 
 river of 4 2, and imagine a line drawn through all the points hav- 
 ing a position similar to R. 19. Will this line lie near the inner 
 or the outer border of the plain ? 20. Why may it be called the 
 fall line ? (DE, 157.1 ; DP, 127.8 ; G, 70.8 ; T, 75.1.) 21. What 
 is the relative direction of the fall line and the shore line? 
 
22 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 22. How is the fall line related to the "head of navigation" (the 
 point farthest upstream which can be reached by boats from the 
 sea) ? to the situation of villages or cities that make use of water 
 power in manufacturing ? 23. Name several cities of this kind in 
 the eastern United States. (DE, 158.2 ; DP, 128.9 ; T, 75.6.) 
 [24. Examine Rocky river, 35 1, near Berea. At what point does 
 it show a rapid fall ? What is the (probable) origin of this fall ? 
 What use may be made of it in Berea? 25. What evidence does the 
 river give of being graded from the fall to lake Erie ? What is 
 its slope in its graded course ? How much does it fall at Berea ? 
 26. Compare the depth of the valley beneath the plain, upstream 
 and downstream from the fall ; explain the difference.] 
 
 6. If 5 is omitted, omit 6 also. [1. Suppose that a deep well 
 at D, 4 2, reaches hard rocks, like those of the oldland, at a depth 
 of 25' ; a well at C reaches them at 35' ; one at M, at 50' below 
 the surface of the plain. 2. What does this indicate as to the gen- 
 eral slope of the ancient sea bottom on which the coastal-plain strata 
 were laid down ? 3. Draw a (gently undulating) line in 4 3 to repre- 
 sent the profile of the ancient sea bottom. 4. At what depth below 
 the surface of the plain at K, 4 2, would the hard rocks probably 
 be reached in a well? 5. How a-re the hard rocks of the oldland 
 and the strata of the coastal plain represented on the W. and S. 
 faces of the block diagram, 6 14 ? 6. Why are the coastal-plain 
 strata drawn slanting on the left side of the block and horizontal 
 on the front face ? 7. What facts, observed on the valley sides, 
 or discovered in deep wells, give reason for shading the block 
 faces in this way ? 8. State the relation of the facts presented in 
 this section to artesian wells. (DE, 238.1 ; DP, 126.8 ; G, 154.3 ; 
 T, 72.9.) NOTE : The relation of artesian wells to the Atlantic 
 coastal plain of the United States is fully treated by N. H. Darton, 
 Bulletin 138, U. S. G. S.] 
 
 7. 1. Mark the river [red] where it is flowing against the valley 
 sides in 4 1 ? in 4 1 a ? in 4 2 ? in 5 8 ? 2. At such places the base 
 of the valley side is worn away by the river, and as a result the 
 
VALLEYS IN A COASTAL PLAIN 23 
 
 loose waste on the valley side slips down into the river and is 
 washed away. 3. What effect will this have on the width of the 
 valley floor ? Explain by the left slope of 4 4. (This figure is a 
 cross profile of a valley ; it is on a larger scale than 4 2.) 4. Where 
 is the waste from the valley sides finally deposited ? 5. The river 
 slowly changes its course, now undercutting this part, now that 
 part, of the valley sides. What effect will this have on the width 
 of the valley as a whole ? 6. Was the valley formerly narrower or 
 wider than now ? 7. What relation must exist between the altitude 
 of the plain (as determined by amount of uplift) and the depth of 
 its valleys ? between the age of the plain (time since its slow 
 uplift) and the width of its valleys ? 8. Mark x on 5 8 and on 
 4 1, where cities might be built on the upland close to the river, so 
 as to have the advantage of trade by river boats, and to avoid the 
 danger of river floods. 9. What cities are thus situated with 
 respect to the Mississippi river? (See 5 8 a, 5 8ft.) On which side of 
 the river and in what states are these cities ? 
 
 8. 1. Draw in 4 5 an E.-W. profile across the valley of 4 2 at DFD'. 
 (Determine the altitude of the plain and of the valley floor on the 
 line DFD' in 4 2 ; mark on edge of paper slip the breadth of valley 
 at top and at bottom of the side slopes ; transfer to 4 5.) 2. Add 
 dotted lines to 4 5 to show two earlier cross profiles and two later 
 cross profiles. 3. Which will be greater in future, the deepening 
 or the widening of the valley? Why ? 4. Part of a similar valley 
 is mapped in 3 6d : the valley sides are shaded with down-slope lines 
 or hachures ; the unworn upland is dotted. 5. Complete 3 6 c and 
 3 6 e, to show earlier and later stages of valley form ; complete the 
 other figures of this series. 6. What does the series show as to 
 change in curvature of river ? in breadth of valley floor? in upland 
 area ? 7. On which is erosion more rapid, a steep valley side or a 
 nearly level upland plain ? Why ? 8. A valley in the stage of 
 development shown ins6a may be called young; in the stage of 
 36d, mature. 9. Why are these terms appropriate? 10. In what 
 stage of development is the valley of 42 at H? 11. The upland 
 
24 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 plain bordering the valley of 3 6 d has been very little changed ; 
 such a plain may therefore be described as in a young stage of 
 development, although its river and valley are mature. 12. In 
 what stage is the plain mapped in 4 7 ? 13. In what stage are the 
 valleys of 4 7 ? 14. What are the most important elements or 
 parts of a young coastal plain ? of a mature valley in a young 
 coastal plain ? [15. What are the variable elements of a young coastal 
 plain ? NOTE : The form of the oldland may vary greatly in differ- 
 ent examples ; it is sometimes less, sometimes more hilly or moun- 
 tainous ; its border may be nearly straight, moderately curved, or 
 very irregular, etc.] 
 
 9. 1. Heavy rain may wear channels or gulleys in valley sides. 
 Why ? 2. What becomes of the waste that is washed from the 
 gulleys ? 3. As time passes, the gulleys are worn back farther and 
 farther into the plain. Why ? 4. As the gulleys grow to a length 
 of a few hundred feet or more, they may be called ravines. 5. How 
 many ravines are shown in the block diagram, 58? (Scale much 
 larger than in 4 1.) 6. Draw in 5 8 [red] lines along the 100' and 
 150' contours on the farther side of the valley. 7. Why do the con- 
 tours turn from the valley side into the ravine ? 8. How do the 
 contours turn where they cross the ravine stream (or rivulet)? 9. 5 9 
 is a map (on still a larger scale). Which part of 5 8 does it show ? 
 Draw the 100' and 150' contours in the ravine. 10. How do the 
 contour lines of a main-valley side turn when they come to a side 
 ravine ? 
 
 10. 1. 5 10, 5 11, 5 12, are contour-line maps (except that ravine 
 H is hachured) representing three stages in the development of a 
 valley and its ravines in a coastal plain ; the scale is the same as 
 in 4 2. The top and bottom of the valley-side slopes are shown by 
 dotted lines. 2. What is the contour interval ? the altitude of the 
 upland and the depth of the main valley at the N. border of 5 10 ? 
 the breadth of the main valley floor ? 3. How can you tell which 
 figure represents the earliest of the three stages ? the latest of the 
 three ? 4. Draw the stream for ravine R, 5 10 ; draw the contours 
 
VALLEYS IN A COASTAL PLAIN 25 
 
 for ravine Q. 5. How does ravine T differ from ravine R as to 
 length ? as to branches (or forks) ? 6. Add a line on the left side 
 of the valley in 4 4 to show the profile of a short ravine stream. 
 7. Which has the steeper fall, a ravine stream or the river that it 
 flows into ? Why? 8. Compare ravine T in 5 10, 5 11, and 5 12 as 
 to length ; as to branches. 9. How are the changes produced ? 
 10. Compare the direction in which the ravine is lengthened with 
 the direction of its stream flow. Explain. 11. How can the term 
 hedward erosion [or retrogressive erosion] be used in this connec- 
 tion ? 12. As the ravines gain the length of a mile or two they may 
 be called side valleys ; the parts of the upland that enter between 
 ravine or valley branches may be called spurs. 13. By what letter 
 are some of the spurs E. of the main valley indicated in 5 11 and 5 12? 
 Print the same letter on four other spurs. 14. In which figure are 
 upland spurs most numerous ? Why ? 15. Draw in 5 11 and 5 12 
 the contoiirs for ravine Q, beginning with the 50' contour. Draw the 
 stream (and its branches) for ravine R. 16. Add to the left side of 
 4 4 two side-stream profiles later than the one previously drawn ; 
 on the latest profile draw also the profile of a branching rivulet. 
 17. Which valley, 5 10, a 11, or 5 12, most nearly corresponds in 
 stage of development to the valley of Rocky river, 35 1. [18. Many 
 of the side streams and valleys in 5 12 are somewhat irregular in 
 direction, but most of the larger ones (almost) agree in direction 
 with the general slope of the plain. Why do they thus (almost) 
 agree ? 19. To what class do they belong ? (See 3 of this exercise.) 
 Why? 20. The streams and valleys whose direction is less regular 
 may be called insequent, because they do not follow the general 
 slope of the plain. Print I N near some insequent ravines in 5 12. 
 21. The fainter the initial slope of the plain the more numerous 
 and irregular will be the insequent streams. Why ?] 
 
 11. 1. What is the width of the main valley floor in 5 10, 5 11, 
 and 5 12? What change is shown? How has it been produced? 
 [2. Why has the depth of the main valley not changed ? 3. In 
 what direction (compared to the general direction of the river) has 
 
26 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 the bend W in the main river shifted its position in the change 
 from 5 10 to 5 11? from 5 11 to 5 12 ? 4. Have the other bends 
 shifted in the same way ?] 5. Why may the river and valley of 
 5 11 be called mature ? 6. Suppose that the next river valley E. 
 of 5 12 to be a mile away ; describe the features that you would 
 pass in walking from one river to the other. 7. Which parts of the 
 upland plain might be described as dissected by ravines ? Which 
 part as undissected, or as not yet dissected? 8. What becomes of the 
 rain which falls on the undissected parts ? 9. In which of these 
 parts would roads be straight ? crooked ? Why ? In which parts 
 would plowing and reaping be easiest ? Why ? 10. Which parts 
 would probably be cultivated? Which parts left to be overgrown 
 with bushes and trees ? 11. Which parts of a coastal plain (in re- 
 lation to its main consequent rivers) will be earliest dissected ? 
 latest dissected ? 12. Upon what factors will the depth of dissec- 
 tion (strength of relief) depend ? 13. When so many branching 
 side valleys have been formed that little of the plain remains undis- 
 sected, why may it be described as maturely dissected, or as hav- 
 ing reached a mature stage in its cycle of erosion? 14. Which 
 reaches maturity first, the upland of a coastal plain or a large con- 
 sequent river which crosses it ? W T hy ? 15. Why may the upland 
 surface of a young coastal plain be described as undivided, or as 
 indistinctly divided as to stream basins ? 16. Why may the up- 
 land surface of a mature coastal plain be described as thoroughly 
 subdivided as to stream basins ? [17. Describe the appearance of a 
 district 80 mi. inland in a mature coastal plain in which the initial 
 surface had a seaward slope of 5' in a mile, this district extending 
 between two large consequent rivers, 10 mi. apart, each having a 
 fall of 6" in a mile. 18. W T hat changes in relief would be noted in 
 crossing this district from one of the rivers to the other ? in going 
 from the middle of the district to the seashore ?] 
 
 12. 1. In what direction does the coastal plain of 6 13 slope ? 
 About how wide is it ? About how high along its inner border? What 
 is its slope in feet per mile? [2. Draw in o!3a a cross profile of 
 
27 
 
 this plain, and indicate the extension of the oldland rocks beneath 
 the strata of the plain.] 3. How many consequent rivers cross the 
 plain from, the oldland ? 4. What is their average fall per mile ? 
 5. Draw several branching streams, as indicated by the contour 
 lines. [6. Are the branch streams mostly consequent or insequent ?] 
 7. Mark S on some spurs between the stream valleys. 8. Is this 
 plain in an earlier or a later stage of development than the plain 
 of 4 7 ? How can you tell ? 9. In what stage is each plain ? 
 State your answers in such terms as early youth, late youth, early 
 maturity, full maturity, late maturity. 10. Suppose the region 
 of 6 13 to be lowered, or depressed, 110' ; draw a [blue] line to 
 show the shore line after depression. 11. Why is the new shore 
 line irregular? 12. What is the relation of valleys and spurs of 
 the plain before depression to bays and land-points of the shore 
 line after depression ? 13. Why do some bays reach farther inland 
 than others ? 14. Why may these narrow bays be described as 
 partly drowned valleys ? 15. Why may the shore line be described 
 as embayed? 16. Would the water in the bays be salt or brack- 
 ish ? NOTE : At the head of a long narrow bay, into which a large 
 river flows, the water may be partly salt or brackish. 17. Narrow 
 bays of this kind are sometimes called " rivers." How do such 
 "rivers" differ from ordinary rivers ? 18. May the name "river" 
 be properly given to the water that occupies a (partly) drowned 
 valley? [19. Suppose the region of 5 12 to be depressed 75' ; draw 
 the new shore line [blue], and shade lightly [blue] the submerged 
 or drowned parts. 20. About how deep would the chief bay be at 
 Y ?] [21. If an explorer came upon a coastal plain, what features 
 should he examine in order to give a good account of it ?] 
 
 13. [1. Part of the Atlantic coastal plain of the Eastern United 
 States is shown in 352. Locate it on Plate 40. 2. What is the 
 scale of the map ? the contour interval ? the altitude of the upland 
 above sea level ? the depth of Trent river valley below the upland 
 plain ? 3. This part of the plain is 25 mi. inland from (W. of) the 
 Atlantic shore line. What is the average slope of the plain ? the 
 
28 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 average fall of Trent river (distance along river course to mouth 
 about 38 mi.) ? 4. With which figure of 3 6a-6ff does the Trent 
 valley best correspond ? 5. In what stage of development is this 
 valley ? 6. Is the plain much dissected or little dissected ? In what 
 stage of development is the plain ? 7. Another part of the Atlantic 
 coastal plain in North Carolina is shown in 35 3. What is the scale ? 
 the contour interval ? 8. What is the general altitude of the up- 
 land above sea level ? the general depth of the valleys below the 
 upland? 9. About how wide are the valley floors or flood plains? 
 10. What features of this district show it to be in a more or less 
 advanced stage of development than the preceding example ? 11. In 
 what stage of development are the streams and valleys ? the 
 uplands ? 12. A third part of the Atlantic coastal plain is shown 
 in 35 4. Locate it. What is the scale of the map ? the contour 
 interval ? 13. What is the general altitude of the uplands ? the 
 depth of the valleys ? 14. In what stage of development is this 
 part of the coastal plain ? 15. What movement (elevation or 
 depression) appears to have taken place since the dissection of the 
 plain ? 16. How wide is Wicdmico " river " ? 17. How do you sup- 
 pose it gained so great a width ? 18. Do you think that the water 
 of this "river" is fresh, salt, or brackish? 19. Is the Wicdmico 
 properly a river or a narrow bay ? 20. Compare the location of 
 the villages, Wicdmico and Chaptico. 
 
 14. Define the following terms : Preliminary , flood plain ; 
 3, consequent river, consequent valley, baselevel ; [ 4, graded 
 river ; 5, outcrop, structure, fall line ; 6, artesian well ;] 8, young 
 valley, mature valley, young coastal plain ; 9, gulley, ravine ; 
 10, side valleys, headward erosion [retrogressive erosion], spur, 
 [insequent stream] ; 11, late mature valley, dissected plain, 
 maturely dissected plain; 12, drowned valley, embayed shore 
 line. 
 
EXEECISE IV. PLATEAUS AND CANYONS 
 
 OBJECT. To study the forms produced by the erosion of a plateau. 
 
 Preliminary. 7 1 is drawn as if a block of the earth's crust had 
 been cut out from a plateau, through which a river flows at the 
 bottom of a canyon, or deep and narrow valley. The block shows 
 a vertical front face, as MNRQ. The figure is drawn as if in a 
 desert, free from vegetation, so as to show its forms better. Hori- 
 zontal and vertical scales are the same. North is toward the back 
 of the block ; the back is (about) two miles from the front. The 
 base of the block represents sea level. Distances E. and W. (right 
 and left) may be measured on the scale of miles at the front base 
 of the block; altitudes, on the vertical scales (broken lines) that 
 rise through the river in the foreground and background. The left 
 front profile is omitted, so that it may be drawn by the pupil. 
 The plateau must be thought of as extending a long distance in 
 all directions. The beginning of the canyon is many miles N. ; the 
 end, many miles S. of the part here drawn. This exercise uses 
 7, 8, 9, 10, 1-10 ; [also 36 1-5]. 
 
 1. 1. How many vertical rock faces or cliffs are seen in 7 1 on the 
 E. side of the canyon ? on the W. side ? 2. How many inclined 
 slopes on each side ? 3. Compare the cliffs on the two sides as 
 to height ; compare the slopes on the two sides as to down-slope 
 length. 4. What is the altitude (above sea level) of the top of 
 cliff D in the foreground (use the foreground vertical scale) ? in 
 the background (use the background vertical scale) ? of the top 
 of cliff B in the foreground and background ? 5. Where on the W. 
 side of the canyon do you see a group of rock layers, or strata, cor- 
 responding to the group which appears or outcrops in cliff D on the 
 E. side ? in cliff B ? 6. Compare the altitude of the corresponding 
 
 29 
 
30 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 cliff tops on the two sides of the canyon. [Make a rough imitation 
 of a plateau and canyon with two piles of books.] 7. Are the strata 
 of cliff D in a horizontal or a slanting (inclined) attitude ? of 
 cliff B ? 8. Draw some light lines on the front face of 7 1 to show 
 the attitude of the slope-making strata. 9. Describe the structure 
 (arrangement and composition of the strata) of the plateau. (DE, 
 162.8; DP, 141.2; G, 175.2; T, 82.9.) 
 
 2. 1. Suppose that, at time of rain, a small stream ran forward 
 past X, 7 1, to the rim of the plateau and fell from the cliff ; draw 
 a [blue] line to show its path down to the river. 2. Compare this 
 line with the profile of the E. canyon wall on the front face of the 
 block. 3. What is the (vertical) thickness of the group of strata, or 
 formation, which determine cliff D ? cliff B ? slope C ? NOTE : Weak 
 strata crumble away, forming slopes ; strong or resistant strata pre- 
 serve steep cliff faces for a long time. 4. Complete the front profile 
 on the W. side of the canyon (making it correspond to the E. side) ; 
 shade lightly [or tint with crayons] the strong formations, or cliff 
 makers, for an inch or more to the left of the W. profile. 5. Print 
 letters on the cliff-making and slope-making formations, in the front 
 section, E. and W. of the canyon, corresponding to the letters AD 
 on the canyon wall. 6. What is the relation between the height of 
 a cliff face (from bottom to top) and the thickness of the cliff-making 
 formation ? between the length of a slope (measured along its 
 incline) and the vertical thickness of its weak formation ? 7. Is 
 the uppermost formation E strong or weak? 
 
 3. 1. What is the general altitude of the plateau surface in 7 1 ? 
 2. Fossils of marine animals are often found in the strata of which 
 plateaus, such as the one here figured, are built. Under what con- 
 ditions must such strata have been deposited ? 3. What movement 
 of the earth's crust must be supposed in the plateau region, since 
 the strata were deposited ? 4. What is the depth of the canyon 
 beneath the plateau surface at the back of 7 1 ? at the front ? 
 5. Which way does the river flow ? 6. On what formation is the 
 river flowing in the background ? In what formation is it flowing 
 
PLATEAUS AND CANYONS 31 
 
 for most of its length in 7 1 ? 7. To what parts of 7 1 do the rapids, 
 falls, and lower course of the river in 7 la correspond ? 8. Draw in 
 7 1 a the profile of the rapids and falls when the cliff of the falls 
 stood 1000' farther S. (use the horizontal scale of 7 1) ; when the 
 cliff comes to stand 500' farther 1ST. 9. Describe how the retreat 
 or recession of the falls is brought about. (DE, 251.8 ; DP, 144.2, 
 235.8; (,', 41.2; 7', 54.2.) 10. How do you suppose the canyon was 
 formed? (DK, 162.7; DP, 141.9; G, 32.1; T, 81.4.) 11. What is 
 the width of the river ? of the canyon at the level of the river in 
 the foreground ? of the canyon at the level of the plateau (top of 
 cliff Z>) in the foreground ? 12. Why is the canyon wider at the 
 top than at the bottom ? 13. Draw two vertical lines in the front 
 of 7 1 to show the form that the canyon would have had if the 
 strata in its walls had not weathered and crumbled (that is, as if 
 the canyon had been cut only by the river). 14. In the canyon 
 as drawn in 7 1, has the greater amount of rock been eroded by the 
 direct action of the river or by the action of weather on the walls ? 
 4. 1. What effect will the (relatively) rapid weathering and 
 wasting of formation C, 1 1, have on its sloping face ? on the face 
 of the slow-weathering cliff D ? Answer the same questions for 
 formations A and B. 2. How may the term retreat or recession 
 be used in this connection ? 3. Draw a line W. of the canyon, 
 showing the profile of its wall after cliff D has retreated 200'. 
 4. What becomes of the large rock blocks that, from time to time, 
 may be loosened by the weathering of cliff D ? 5. Why is not the 
 bottom of the canyon heavily filled with waste that has fallen from 
 its walls ? 6. What relation must exist between the supply of waste 
 from the walls and the load of waste that the river can transport ? 
 7. In order to wash away or transport the waste that falls from the 
 canyon walls, must the river have a rapid or a slow current ? a 
 strong or faint slope ? NOTE : Some of the waste from each cliff 
 remains on the slope below it, and (with the finer waste from the 
 slope-making formation) makes a cover or talus on the slope. 
 Weathering causes the talus fragments to creep slowly down the 
 
32 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 slope ; washing hastens their movement. 8. What becomes of the 
 talus waste in 7 1 when it reaches the foot of slope C ? of slope 
 A ? 9. Which parts of the walls show the greatest amount of bare 
 rock outcrops ? Which parts, the least ? Why ? 10. Do the weak 
 or strong formations show the best outcrops ? 
 
 5. 1. How does the cross profile of the canyon in the background 
 of 7 1 differ in depth and width from the cross profile in the fore- 
 ground? 2. Draw in the background (see dotted line f/f/) a cross 
 profile, as if to show the canyon some miles upstream ; another cross 
 profile (see dotted line VV") still farther upstream. How do the 
 depth and width of the canyon change, as it is followed upstream ? 
 3. What will be the position of the river, still farther upstream, 
 in relation to formation D ? 4. Draw a profile along that part of 
 the river to show this relation (part of formation D on the left front 
 face of 7 1 may be used in drawing this profile). 5. In the back- 
 ground of 7 1 draw a profile across the river beyond (N/. of) the point 
 where it falls from formation D. 6. How is that part of the river 
 course related to the plateau surface ? 7. Why do the strong (or 
 resistant) formations deserve the name of " cliff makers " in relation 
 to the canyon walls, and " fall makers " in relation to the river 
 course ? 8. In which kind of formation, strong or weak (resistant 
 or yielding), does the greater part of the river course lie ? 9. In 
 which kind of formation has the river course a gentle fall ? a steep 
 fall ? [10. Estimate the fall of the river (feet per mile) from the 
 foot of the B falls to the foreground.] 
 
 6. 1. Suppose you were at Q, 1 1, and wished to go to M without 
 descending into and climbing out of the canyon ; describe the route 
 you might follow. 2. Draw in the foreground a cross profile (see 
 dotted line W, E. of canyon) of the canyon for a point some miles 
 downstream (assuming the altitude of the plateau to continue un- 
 changed). 3. How does profile W differ in depth and width from 
 the foreground profile of 7 1 ? How does profile W differ from 
 profile F? 4. How do the depth and width of a canyon vary as it 
 is followed downstream ? Explain. [5. What limits the depth to 
 
PLATEAUS AND CANYONS 33 
 
 which a canyon can be cut ? (Consider, in your answer, altitude of 
 plateau, slope of river, and distance from the river mouth.)] G. What 
 changes in depth and breadth would you expect at the front profile 
 of 7 1 if weathering and river action continued for a long time ? 
 Why have these changes not already taken place ? 7. Would you 
 describe the river and canyon as young, mature, or old? Why? 
 8. What stage in the cycle of erosion do you think the plateau has 
 reached ? 9. What are the chief characteristics of a young plateau ? 
 [10. The Zambezi river in the interior of South Africa (locate the 
 river on Plate 45) flows in a broad channel with a moderate current 
 on a plateau (altitude, 3500'), following a broad and shallow valley 
 for many miles ; it then suddenly plunges down 300' at Victoria 
 Falls into a narrow and steep-walled gorge or canyon, through which 
 it rushes rapidly in a narrow channel. The canyon continues 40 
 mi. ; it deepens and widens (and its side canyons increase in 
 length) as it is followed downstream from the falls. 11. What is 
 the origin of the canyon ? of the falls ? (See (London) Geograph- 
 ical Journal, Vol. XXV, 1905 ; Vol. XXIX, 1907; excellent plates.)] 
 7. 1. 8 2 is a diagram of another plateau and canyon drawn in 
 the same way as 7 1. How does it differ from 7 1 as to altitude of 
 plateau ? altitude of river in foreground ? depth of canyon below 
 plateau surface ? breadth of canyon at plateau level ? amount of 
 original plateau uplift? number of cliffs and of slopes in canyon 
 wall ? height of waterfall in river (near B) ? 2. Complete the front 
 profile W. of the river in 8 2 and draw lines separating the cliff- 
 making and slope-making formations ; shade lightly the cliff-making 
 formations W. of the canyon; print letters on the several forma- 
 tions corresponding to the letters on the canyon wall. 3. Has the 
 plateau mass a horizontal or an inclined structure ? 4. Draw two 
 canyon-wall profiles, W, X, as if for points farther downstream, in 
 the E. foreground ; two, U, V, as if for points farther upstream, in 
 the E. background. 5. Mark Q at a point where you would go to 
 get a good view up the canyon if you were on the E. part of the 
 plateau ; Q'> on the W. part for a view down the canyon. [6. Do 
 
34 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 the dots in these circles represent (about) the size of a man or of 
 a house ?] 7. What is the width of the canyon at the level of layer 
 H in the foreground ? in the background ? at the place of greatest 
 width ? 8. Why does the width vary ? 9. Why does the E. side 
 canyon fork near its head (F), while the W. side canyon does not 
 fork at its head (Z)? 10. At what time in its history (earlier or 
 later than now) would the E. side canyon resemble the present form 
 of the W. side canyon ? When would the W. side canyon resemble 
 the present form of the E. side canyon ? Explain. 
 
 8. 1. Why is cliff face D, 8 2, higher (from bottom to top of cliff) 
 than cliff face F ? cliff face F than // ? [2. Why is slope G less steep 
 than slope C ?] 3. Why do falls occur in the river near the fore- 
 ground ? 4. If you could follow up the river, would the next fall 
 probably be of greater or of less height than the one here shown ? 
 Why ? 5. How many falls occur on the (wet-weather) stream of 
 the E. side canyon ? of the W. side canyon ? Why ? (DE, 252.2 ; 
 DP, 144.2; G, 38.8; T, 54.1.) 6. Counting down from the plateau, 
 which fall on the side streams will be the highest ? 7. Draw on 
 the W. front face of 8 2 a line (beginning at the river) to represent 
 the profile of the W. side stream. 8. AVhich has the (average) 
 steeper descent, a side stream or the wall of the main canyon ? a 
 side stream or the main river ? Explain. [9. If you wished to de- 
 scend from the plateau to the river, where would you try to find a 
 way? Why? In which part of such a way would the greatest dif- 
 ficulty be found? Why?] [10. Draw (short) horizontal lines to 
 separate the strong and weak formations corresponding to the profiles 
 in s2# (the profiles, which show only the surface, are thus changed 
 into sections, which show also the internal structure). Shade (lightly) 
 the cliff makers in one of the sections. 11. Which section has two 
 thick resistant formations ? many thin resistant formations ? a 
 great thickness of weak strata in its lower part ? How can you 
 tell ?] [12. The weaker formations are sometimes weathered back 
 a few feet under the overlying cliff-making formation, which there- 
 fore "overhangs," forming natural "cliff caves." 8 2 a. is a sketch 
 
PLATEAUS AND CANYOXS 35 
 
 of such a cave, in which a rough wall has been built to give 
 better protection. Many such "cliff dwellings," now more or less 
 broken down, are known in the canyons of Colorado, New Mexico, 
 and Arizona, but they are no longer occupied by the Indians who 
 formerly (before the coming of the white men) lived in them.] 
 
 9. 1.93 shows part of still another plateau and canyon ; compare 
 it witli 8 2 as to general altitude of the plateau ; depth of the can- 
 yon ; number of cliffs and slopes ; width of canyon at plateau level ; 
 amount of plateau uplift. 2. In which example, 7 1, 82, or 93, do 
 you think a longer time has passed since uplift aud erosion began ? 
 How can you tell ? 3. Complete in 9 3 the profile and section on 
 the W. side of the canyon. How far has cliff J retreated westward 
 since it was first cut through by the river? 4. Which cliff has re- 
 treated the most, / or G ? G or E ? Why? 5. Is the retreat of 
 cliff E more affected by the retreat of slope F or of slope D ? Why ? 
 6. Above which cliffs is there a nearly level bench or platform (from 
 top of cliff to base of next higher slope) ? [7. Explain the origin of 
 the platform over cliff E ; over cliff G. (DE, 163.9 ; DP, 143.9.) 
 8. Why is one of these platforms broader than the other ? 9. Why 
 is there no platform over cliff C ? 10. What becomes of the talus 
 on slope B ? on slope D ? on slope F? on slope H? (DP, 144.1.) 
 
 11. Draw another W. wall profile, as if the river had worn down 
 its channel 100' deeper and the main cliff had retreated 500'. 
 
 12. About how much additional retreat of the top cliff is thus 
 shown ? 13. What change in the width of the platform on E is 
 thus shown ? 
 
 10. [1. The canyon of the Colorado river has been eroded in a 
 plateau ; part of it is mapped in 36 1. Locate on Plate 40. A 
 cliff is shown where two or more contours are close together ; 
 a platform, by wide-spaced contours. What is the altitude of the 
 plateau ? of the river ? the depth of the canyon ? How far is 
 the plateau rim S. of the river ? 2. How many cliffs, slopes, and 
 platforms are shown ? 3. Which cliff, counting down from the top, 
 seems to be highest ? (See Powell's Explorations of the Colorado 
 
36 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 River of the West, Washington, 1875 ; a remarkable narrative of 
 an adventurous journey down the river in boats (see especially 
 p. 100); many plates. Button's Tertiary History of the Grand 
 Canyon District. U. S. G. S., Monogr. II (see the excellent plates in 
 atlas of this report, especially VI); an abridgment of Button's 
 work is given in the Second Annual Report of the U. S. G. S. The 
 large contour map, Bright Angel quadrangle, Arizona, by F. E. 
 Matthes (from which the map 36 1 is taken), is an extraordinary 
 example of topographic surveying.)] 
 
 11. 1. If you walked along the edge or " rim " of the plateau, 9 3, 
 would your path be straight or irregular ? more or less irregular 
 than the course of the river? Why? 2. Why is the edge of the 
 plateau in 8 2 more irregular than that in 7 1 ? in 9 3 more irregu- 
 lar than in 8 2 ? 3. Why is the edge of the uppermost cliff /, 9 3, 
 more irregular than that of the second cliff G, and so on down to 
 cliff C ? 4. Draw a line (so far as there is room) on the front face 
 of 9 3, beginning at the river, to represent the profile of the E. side- 
 stream. 5. How does this differ from the corresponding profile 
 drawn in 8 2, as to average slope ? as to number of falls ? [6. In 
 9 3 b the formations with odd numbers are resistant cliff makers. 
 Draw profiles of canyon walls corresponding to the several posi- 
 tions of the river, A,B, C,D (as if the profiles were in succession 
 farther and farther downstream).] [7. Where in 9 3 is some of the 
 coarser waste from the side canyons deposited ? (See 9 3 a, drawn on 
 a larger scale.) 8. What is the form of these deposits ? What name 
 is given to them ? (DE, 197.4; DP, 275.9; G, 38.4 ; T, 66.5.) Why 
 are they not seen in 7 1 ? NOTE : When unusually heavy rains 
 occur, a violent flood may rush down a side canyon and sweep great 
 bowlders into the river ; before another flood occurs, the river may 
 gradually roll most of the bowlders downstream. 9. What effect 
 has a " fan " on the width of the river at the fan front ? next up- 
 stream from the fan ? on the slope of the river ? on the river cur- 
 rent ? on the river bank opposite the fan ? on the passage of boats 
 or rafts down the river ?] [10. Imagine that several rivers, like the 
 
PLATEAUS AXD CANYONS 37 
 
 one shown in 9 3, crossed the plateau, 20 to 50 mi. apart ; describe 
 the general appearance of the region. 11. Would most of the region 
 be occupied by undissected plateau surface or by canyons ? 12. When 
 the cycle of erosion is complete, the plateaus would be worn down 
 to a lowland. Does 9 3 represent an early or a late stage of a com- 
 plete cycle ? 13. May the plateau in 9 3 be described as young, 
 mature, or old? 14. Compare the depth to which the river has 
 eroded its canyon in the plateau with the depth to be eroded in 
 future. 15. Has the river in this part of its course developed a 
 rather evenly graded course, or is it still interrupted by steep 
 waterfalls ? NOTE : A river with many waterfalls in a narrow 
 valley might be called young ; with an evenly graded course but 
 without a flood plain, early mature ; with an evenly graded course 
 and an open flood plain, late mature. 16. In which of these stages 
 is the river in 9 3 ?] 
 
 12. 1. 10 4 is intended to represent a later stage (many thousand 
 years later) in the erosion of the plateau which is shown in 9 3. 
 Complete the W. front section in 10 4 and add letters corresponding 
 to those of 9 3. 2. Compare 9 3 and 10 4 as to altitude of plateau 
 (the plateau surface in 10 4 is seen only in the far right-hand (NE.) 
 corner. Why ?) ; amount of uplift ; depth of canyon ; altitude of 
 river in foreground. 3. Compare the two figures as to amount of 
 load received by river from canyon walls (the steeper the walls, the 
 more waste falls from them) ; from side canyons (the longer the side 
 canyons, the more waste they supply) ; fall of river in feet per 
 mile (length of river here shown in each figure, 2 mi.) ; width of 
 canyon bottom or floor (from talus to talus) ; width of canyon at 
 level of plateau. (In 10 4 the width is (about) twice the distance 
 from background vertical scale to back profile of cliff / in NE. corner. 
 "Why ?). 4. Compare the two figures as to length of side canyons ; 
 number of cliffs and slopes shown E. of river. Why are fewer 
 cliffs seen in 10 4 on W. than on E. ? 5. Compare the two figures as 
 to breadth of platforms; average slope of canyon walls (in io4, 
 slant of straight line drawn at back of block from top of cliff J 
 
38 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 to base of lowest talus). 6. Where these comparisons show differ- 
 ences, explain them. 7. In the change from 9 3 to 10 4, why has the 
 widening of the canyon at the top been greater than the deepening 
 at the bottom ? [8. Is the retreat of cliff E more affected by the 
 weathering of slope D or of slope F? Why? 9. Which cliff face 
 tends to retreat more rapidly, C or E ? Why ? 10. Why is cliff 
 face C less distinct than E ? less distinct than C in 9 3 ? 11. Ex- 
 plain the origin of the flat canyon floor in 10 4. How does it differ 
 in origin from the platforms ?] 
 
 13. 1. If the plateau of io4 were seen in a still later stage of 
 erosion, what change would you expect to find in the altitude of 
 the river ? in its fall per mile ? in the depth of the canyon ? in 
 the width of the canyon floor ? of the canyon top ? 2. What 
 change would you expect in the length of the side canyons ? in the 
 breadth of the platforms ? in the number of cliffs, slopes, and plat- 
 forms ? in the irregularity of the plateau rim ? 3. As the plateau is 
 more and more eroded, will the term canyon be more appropriate 
 or less appropriate as a name for its valleys ? 4. Estimate (roughly, 
 in miles) the whole length of the E. side canyon of 10 4. 5. Imagine 
 other rivers and canyons like those of 104, 20 to 50 mi. apart. 
 Would traveling be easy or difficult along a line about midway 
 between two such rivers ? Why ? 6. Imagine that the side canyons 
 have increased to lengths of from 12 to 30 mi. What effect would 
 be produced on the plateau where the heads of two side canyons 
 meet ? 7. Describe a route of travel under such conditions about 
 midway between two rivers ? NOTE : When wide belts of undis- 
 sected plateau surface remain between the river canyons, the 
 plateau may be called young ; if the main canyons are very nar- 
 row and the side canyons are very short, the plateau is very 
 young ; as the main canyons widen and the side canyons lengthen, 
 so that the belts of plateau surface are narrowed (but still retain 
 an even surface along the divides between the rivers), the dissec- 
 tion of the plateau may be called early mature; when the side 
 canyons of neighboring rivers meet at their heads, the plateau 
 
PLATEAUS AND CANYOXS 39 
 
 reaches a late mature stage of dissection. 8. In what stage is the 
 plateau of question 5, above ? of question 6 ? of 8 2 ? of 7 1 ? In 
 what stage of development is the river of io4? (See Note, end of 
 11.) Explain. 9. What are the characteristic features of a 
 young plateau ? of a late mature plateau ? of a very young plateau ? 
 of an early mature plateau? [10. 10 4 b represents cliff and talus 
 slopes of another plateau in greater detail than 10 4. Draw lines to 
 the left of the profile (in the air) to represent the internal struc- 
 ture that is indicated by the external form ; shade lightly the harder 
 formations. 11. Where do some strata of intermediate resistance 
 occur (neither good cliff makers nor good slope makers) ?] 
 
 14. [1. 7 5 is an outline map of part of a river system in a dis- 
 sected plateau. How does the scale of this map compare with the 
 scale of 7 1 and 10 4 ? 2. Let there be only one cliff-making forma- 
 tion in the structure of this plateau, and let the line aa, 1 5, 
 represent the edge of the cliff E. of the river in an early stage of 
 dissection. (Neglect the lines bb, cc, for the present.) 3. Why 
 does the cliff line turn into the plateau (away from the main river) 
 in several sharp angles or reentrants ? turn toward the river in 
 several curves ? 4. What is the relation of the reentrants and curves 
 to the side streams ? 5. Why do the reentrants extend to different 
 distances from the main river? 6. Draw a similar line a'a' (be- 
 ginning at N. end), to show the corresponding cliff W. of the river. 
 7. The line bb may now be taken to show the same cliff at a later 
 stage of erosion. Is the cliff now less or more irregular than before ? 
 Why ? 8. Draw a corresponding line b'b' W. of the river. The 
 side ravines are now long enough to be called side canyons. The 
 line cc shows a still later position of the same cliff : what peculiar 
 feature does it show at R? 9. How has this part of the plateau 
 surface come to be separated from (or to " lie out " from) the rest of 
 the plateau ? Such an isolated part is called an outlier. 10. Draw 
 a third cliff line W. of the river, corresponding to cc. How many 
 outliers does it show ? Explain their origin. 11. W T ill these out- 
 liers increase or decrease in size as erosion continues ? Why ? 
 
40 EXERCISES IX PHYSICAL GEOGRAPHY 
 
 12. Are outliers likely to increase or to decrease in number as 
 erosion progresses ? Why ?] 
 
 15. XOTE : If 14 is omitted, omit 15 also. [1. Another use 
 may now be made of 7 5 : it may be taken to represent a well- 
 dissected plateau, with three cliff makers, a, b, c, separated by 
 slope makers. 2. Which cliff maker stands highest in the plateau 
 structure ? How can you tell ? 3. A section along the line A/TV, 
 7 5, is given in 7 6. Complete, in 7 7, a section along the line QS, 
 7 5. (Measure distances in 7 5 on a strip of paper, from Q to 
 cliffs and streams, and transfer the distances to 7 7.) 4. A 
 hachured map of a similar plateau is shown in 7 9. How are the 
 steep cliff faces indicated ? the talus slopes ? the nearly level 
 plateau surface and the narrow platform over the middle cliff? 
 5. Draw hachures for the rest of the figure. 6. 7 8 is a contour 
 map of part of a similar dissected plateau. Why are the contours 
 so crowded on the cliff faces ? What is the contour interval ? 
 7. What is the altitude of the plateau surface ? About how deep 
 is the main canyon ? 8. Draw contours for the rest of 7 8. 9. From 
 which figure can you gain the best idea of the plateau forms, 
 the outline map (7 5), the profiles (7 6 and 7 7), the hachured map 
 (7 9), or the contoured map (7 8) ? Why ? 10. From which map, 7 5, 
 7 8, or 7 9, can an accurate cross section be best drawn ? Why ? 
 11. Which kind of a map would you prefer in finding your way 
 across a dissected plateau ? Why ?] 
 
 16. [1. Consider a broad plateau hundreds of miles across. 
 What general effect will the branching rivers and [frequently in- 
 sequent] side streams of a large river system (or of several river 
 systems) have, as time passes, on the form of such a plateau ? 
 2. The line cccc, 8 10, shows a profile across part of such a plateau. 
 How many cliff-making formations are represented ? How far 
 apart are the two rivers r, r' ? 3. With which one of the plateaus, 
 7 1 to 10 4, does the profile cc, 8 10, most nearly correspond as to 
 stage of erosion ? 4. Draw profiles (beginning at the right) for 
 two earlier stages, b and a, in 8 10 ; for two later stages, d and e. 
 
PLATEAUS AND CANYONS 41 
 
 5. When the profile has reached the stage d, which part of it 
 represents a mesa ? in stage e, which part represents a butte ? 
 (DE, 171.3; DP, 150.6; G, 91.9 -; T, 82.8.) 6. What features 
 occupy the greatest area in stage e ? What features are most 
 conspicuous in the landscape of stage e ? 1. Draw profiles for still 
 later stages, /and g. 8. What has become of the butte (stage e) in 
 stage f? 9. To what form has the lower cliff maker been reduced 
 in stage f? in stage g ? 10. What feature occupies the greatest 
 area in stage g ? What is then the most conspicuous feature ? 
 11. Draw a profile for stage h. What name might be given to the 
 region in this stage ? 12. Describe the general appearance of the 
 district in stage ; in stage e ; in stage g ; in stage A-.] 
 
 17. NOTE : If 1G is omitted, omit 17 also. [1. In which of 
 the various stages, a to h, 8 10, might the district there repre- 
 sented in profile be called a young plateau ? an old lowland ? a 
 maturely dissected plateau ? 2. Explain the altitude of the low- 
 land or peneplain r'/ir in relation to baselevel ? 3. In which stage 
 (young, mature, or old) of erosion of the plateau would its val- 
 leys be called canyons ? would roads and settlements be found 
 chiefly on the highlands ? on the lowlands ? 4. In which, stage 
 would outliers be common ? would the lower cliff maker be reduced 
 to isolated buttes ? 5. AVhere would such buttes stand in relation 
 to the main rivers ? 6. How is the term cycle of erosion illus- 
 trated by 8 10 ? 7. Suppose that when stage g had been reached, 
 a general uplift of the region occurred ; draw a [red] line in 8 10 
 to show the profile of the district when the stage of youth had been 
 reached in the new cycle of erosion (introduced by the new uplift) ; 
 when the stage of maturity had been reached in the cycle.] 
 
 18. [1. 36 2 represents a plateau dissected by canyons. Locate it 
 on Plate 40. In what part of what state is it ? 2. State the scale ; 
 the contour interval ; the general altitude of the plateau ; the depth 
 and breadth of the main canyons ; the length of the side canyons. 
 3. Is the cycle of erosion half accomplished, nearly completed, or 
 only well begun ? 4. In what stage of dissection is the plateau ? 
 
42 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 5. 36 3 is another part of the same plateau, about 50 mi. NE. of 
 36 2 ; the same river is shown in both figures. 6. In what part of 
 36 3 is part of the undissected plateau surface seen ? What is its 
 altitude ? [7. Can you explain why Purgatoire river flows NE. ? 
 To what class does it seem to belong ?] 8. Print on 36 3 PLATEAU, 
 CLIFF, PLATFORM, SIDE CANYON, VALLEY FLOOR, in their 
 proper places. 9. How many cliff-making formations are here ex- 
 posed ? How wide is the platform between the two cliffs ? How 
 high is each cliff ? How long (about) are the side canyons ? How 
 wide is the valley floor ? 10. In what stage of dissection is the 
 plateau? 11. Compare the canyon of Purgatoire river in 36 2 and 
 36 3 (in each case measure canyon width from plateau rim). 
 12. What general rule of canyon form is here illustrated? (See 
 question 4, 6.) 13. Locate the district shown in 364 on Plate 40. 
 In what part of the Allegheny plateau does it occur ? (See DE, 
 Fig. 78 ; DP, Fig. 92.) State 'the scale and contour interval. 
 14. What is the altitude of the plateau ? of the valley floors ? the 
 relief of the district ? 15. What is the width of the upland belt 
 (between the side-valley heads) E. of Battle Creek valley ? How 
 long and wide are the upland spurs (to W.)? Which occupy the 
 greater area, the plateau surfaces or the valleys (from rim to rim 
 of plateaus) ? 16. In what stage of dissection is the plateau in 
 this district ? (See Note following question 7, 13.) 17. In what 
 stage of development are the main streams ? 18. Where do water- 
 falls occur ? In what stage of development are the upper parts of 
 the side streams ? 19. Locate the district shown in 36 5, on Plate 40. 
 What is the scale ? the contour interval ? 20. What is the altitude 
 of the valley floor (or flood plain) of Blackford creek ? the altitude 
 of the hilltops ? the relief of the district ? 21. Which occupy the 
 greater area, the hilltops or the valley floors ? 22. This region 
 was once an even upland (or plateau of moderate altitude). In what 
 stage of dissection is it now ? 23. In what stage of development 
 is Blackford creek ? 24 If this creek is here 700' above sea level, 
 why does it not wear its valley floor down lower? 25. To what 
 
PLATEAUS AXD CANYONS 43 
 
 class do the side streams in 36 2-5 apparently belong ? (See Exer- 
 cise III, 10, question 20.) Why ? 
 
 19. [1. Locate 9 3 c and 9 3 d on Plate 40. In what part of the Alle- 
 gheny plateau are they ? (See DE, Fig. 78 ; DP, Fig. 92.) 2. What is 
 the scale of these maps ? the contour interval ? 3. What river is 
 shown in 9 3c ? How deep is its valley beneath the neighboring up- 
 lands ? 4. How wide is the river ? the valley floor ? 5. Draw a [red] 
 line around the strip of valley floor NW. of the river, and around 
 the strips of valley floor SE. of the river (neglect the valley floor 
 of the branch stream on NE.) ; a [blue] line where the river touches 
 the base of the steep valley side. 6. As you follow down the river, 
 how are the successive valley-floor strips arranged ? 7. Compare the 
 course of Purgatoire river, 36 2, with the course of the Ohio river, 
 93c, and of Captina creek, 93cZ. Which of these streams might be 
 described as nearly straight ? moderately curved (or sinuous) ? 
 strongly curved (or serpentine, or meandering} ? 8. Which of 
 these streams has eroded a meandering valley ? (DE, 271.7- ; DP, 
 253.4 ; G, 51.8 ; T, Fig. 143.) 9. As a meandering valley is widened, 
 is the valley floor normally on the inside or outside of the stream 
 curves ? On which side of the stream curve is the steeper valley 
 side ? (DE, 258.9.) 10. Shade [blue] the normal valley floors and 
 [red] the normal steep valley sides of 93d. 11. Do any abnormal 
 cases occur ? If the stream there followed the broken-line curve, 
 would these cases be normal or abnormal ? 12. What change of 
 stream course has probably taken place there ? 13. Which meander 
 curve is entered by a spur with a low, narrow neck ? 14. Locate 
 10 4 c on Plate 40. Of what plateau is it a part? 15. What is the 
 altitude of the plateau in io4c? the depth and breadth of Cheat 
 river canyon ? 16. In what stage of development are the river and 
 its canyon? 17. Are the side canyons long or short? Are their 
 streams of strong or gentle fall ? 18. Locate 10 4d on Plate 40. In 
 what state is it ? What is the altitude of the highest and lowest 
 parts ? 19. Begin near the NW. corner and draw a [red] line east- 
 ward along the divide between the NE. and the SE. streams. NOTE : 
 
44 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 The streams are drawn in broken lines to indicate that they cease 
 flowing in dry weather. 20. Does the divide follow a uniform alti- 
 tude ? 21. All this district was once a plateau of at least 5000' 
 altitude. To which profile in 8 10 does it now correspond ? What 
 stage of dissection has it now reached ? 22. How many buttes are 
 shown? Explain their origin. 23. To what features in 10 4d does 
 10 4 a correspond ? 24. What is the origin of the plain in io4a ? To 
 which profile in 8 10 does it correspond ? 25. In what stage of the 
 cycle of erosion is the district of the Enchanted Mesa? (DE, 172.3 ; 
 DP, 151.5.) 26. In what part of the United States is it ? 27. Locate 
 (roughly) on Plate 40 the canyon of Kanawha river, shown in the 
 figure at the bottom of this page. Compare this canyon with the 
 canyon of Cheat river, io4c. 28. In what stage of development is 
 the Kanawha canyon ? 
 
 20. Define : Preliminary , canyon ; 1, cliff, outcrop, structure ; 
 2, formation, cliff-making formation, slope-making formation ; 3, 
 retreat or recession of waterfalls ; 4, retreat or recession of cliffs, 
 talus ; [ 8, profiles and sections;] 9, platform; [ 11, alluvial 
 fan, young river, early mature river, late mature river ; 13, young 
 plateau, maturely dissected plateau ; 14, outlier ; 1(5, mesa, butte ;] 
 17, cycle of erosion ; [ 19, meandering river, meandering valley]. 
 
EXERCISE V. THE SCULPTURE OF MOUNTAINS 
 
 OBJECT. To explain various features of mountain ranges. 
 
 Preliminary. 11 1 gives a general view over a rolling district of 
 low hills and shallow valleys, all covered with a deep weathered 
 soil. The district is drained by a large river and many smaller 
 streams, all flowing quietly and smoothly through their flood plains. 
 The soils vary from place to place, as if the underlying rocks were 
 of different kinds. Some low mountains rise in the E. and NW. ; 
 there the soil is thinner and more stony. The view is cut off in 
 front by a vertical section, the baseline of which is at sea level. 
 Altitudes are marked at various points ; a scale of altitudes is 
 drawn near the NE. corner, and a scale of miles along the front 
 baseline. This exercise uses 11, 12, 14, 1:3, 1C, 1-22 [also 37 1-5]. Note 
 that Plate 14 is to be used before Plate 13. 
 
 1. 1. The distance along the winding river A to E, 11 1, being 
 30 mi., what is the average fall of the river in feet per mile ? 2. If 
 E is 600 mi. from the river mouth, what is the average fall from E 
 to the sea ? 3. What is (about) the width of the main river flood 
 plain ? 4. The altitudes on stream (or small river) F (SE. corner of 
 11 1) are indicated for points two miles apart. What is its average 
 fall ? the width of its flood plain ? 5. Why may the streams of this 
 district be described as " thoroughly graded with respect to their 
 general baselevel " (the ocean) ? 6. What is the general altitude of 
 the interf uves, or spaces between the small rivers (see foreground 
 profile) ? their relief ? 7. What is the altitude of the highest moun- 
 tain on the N. border ? the general relief in that mountain group ? 
 NOTE : To find (roughly) the height of the mountain above the sur- 
 rounding district, draw a straight line between the parts of the N. 
 border marked 900', and measure the mountain height above this line. 
 
 45 
 
46 EXERCISES IX PHYSICAL GEOGRAPHY 
 
 2. 1. If you should walk eastward from IF to W', how many 
 times would you go uphill and downhill ? about how many feet 
 would you ascend and descend in each case ? 2. Print D at points 
 where you cross divides between the small rivers /, H, G, F; print 
 d where you cross subdivides between side streams. 3. Draw a 
 line up and down hill, eastward from X to A'', and answer the same 
 questions as in question 1. 4. Draw an E.-W. line through Y (W. 
 center of figure) and print D where the line crosses the divide be- 
 tween the two streams there shown. 5. Draw similar lines through 
 Z, Z, Z, an.d mark the divides on them. 6. Draw a broken [red] 
 line southward from Q, on the 1ST. border, through Y to the S. border 
 of the figure, dividing the drainage area of the main river from 
 that of the W.-flowing rivers. 7. Draw a broken [red] line west- 
 ward from M, on the E. border, to M' near main river, dividing the 
 drainage area of the main river AE from that of the small rivers 
 F, G, H, J. 8. Should the various divides and subdivides that you 
 have marked be described as " high, sharp, and well denned " or as 
 " low, gently rounded, and ill denned " ? 
 
 3. 1. Draw a line along stream F and its NW. branch, over the 
 divide at its head, and down stream R ; mark D at the divide. 
 NOTE : In 16 15 the small crosses ( x X ) represent the altitudes 
 of the two-mile points on streams F and R of 11 1 ; and the dots 
 in the small circles represent the altitudes of the low hills on the 
 neighboring interfluves. (The vertical scale in 16 15 is the same as 
 in 11 1 ; the horizontal scale is smaller.) 2. Draw a line through 
 the crosses ; through the dots. What do these lines represent ? 
 Print F and R near these lines ; draw a short vertical line at the 
 divide between streams .F and R. [3. Suppose the district of 11 1 
 to be inhabited in this stage of its history ; locate a city and some 
 villages in the SE., central, and NW. parts of the district ; connect 
 some of them by a railroad (heavy line) and by several roads 
 (light lines). NOTE : The railroad should not have grades of more 
 than 100' in a mile ; the roads seldom more than 500' in a mile. 
 4. What are the chief difficulties that would be met in making the 
 
THE SCULPTURE OF MOUNTAINS 47 
 
 roads and the railroad ? 5. Which parts of the district are well 
 adapted to farming? Which parts will probably remain forested 
 while the rest is cultivated? 6. Which parts are liable to over- 
 flow by river floods ? How much of the main river appears to be 
 navigable for river boats ?] 
 
 4. 1. 12 2 shows another stage in the history of the same dis- 
 trict, uncounted thousands of years later than the stage shown in 
 11 1. 2. Look at the middle W. part of 12 2. Follow the broken 
 line O O'O" from W. to E. and note the altitudes along it ; note that 
 this part of the district may be described as "arched" or "up- 
 warped." 3. Begin in the SE. corner of the district and follow 
 the line NN', noting the change of altitude along it. What has 
 happened in this part of the district ? 4. Begin at the middle of 
 the E. side, and follow the line MM'Q'Q to the N. border ; this line 
 may be described as " following the crest of the arch," or the " crest 
 of the upwarping." 5. What directions does the crest line follow ? 
 
 6. Is the amount of upwarping uniform all along the crest line ? 
 
 7. Near the head of which stream is it least ? NOTE : The upwarp- 
 ing of the surface, as here shown, is much stronger than ordinarily 
 occurs in mountain ranges. The upwarping is exaggerated in these 
 figures, so as to bring well-developed forms into a small district 
 for easy study. The origin of the forces which slowly warp the 
 earth's heavy crust is not well understood, but the great strength 
 and long-continued action of the forces cannot be doubted; they do 
 not seem to be related to volcanic action. 8. In 16 15 the dots in 
 the larger circles represent several points on the line NN', 122. 
 Draw a curve through the dots. What does this curve represent ? 
 9. Draw, beneath this curve, the profiles of streams F and R (see 
 small crosses + +). Print F and R near these profiles ; draw a 
 short vertical line at the divide. 10. How many feet beneath the 
 upland is the deepest part of each valley ? 11. Why is stream F 
 shorter, and why is R longer than in the corresponding profiles 
 previously drawn in 16 15 ? [12. Why may F be described as "be- 
 headed by warping"? R, as "extended by warping"?] 13. What 
 
48 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 is now the average fall of F ? 14. In so steep a stream there will 
 be many falls and rapids ; the water will flow swiftly in a narrow 
 channel, plunging and foaming ; at times of flood the rushing stream 
 or torrent will sweep along large bowlders. In what stage of devel- 
 opment is such a stream ? 
 
 5. 1. If you went E. along line WW, 12 2, how many times would 
 you go up and down hill ? 2. Draw a similar line XX'. 3. Stream 
 G has three forks, east, middle, and west; compare profiles WW 
 and XX' where they cross the valley of the E. fork of G ; the W. 
 fork. [4. Draw in 16 7 the cross profile (1) of the W. fork of G, 
 on line WW in 12 2; (2) of the small E. branch of H on line XX' ; 
 (3) of J on WW; (4) of F on WW' ; (5) of the three forks of G on 
 A'A"; (6) of H on VV'. 5. How does cross profile (3) differ from 
 (1) and (2) ; (4) and (5) from (3)? (6) from (4) and (5)?] 6. Why 
 are the valleys of F, G, H, etc., in 12 2 unlike the corresponding 
 valleys in ill? 7. Why may the streams of 12 2 be described as 
 revived or rejuvenated ? 8. What has caused their revival ? 9. Why 
 may the new valleys be described (in cross profile) as sharp ^ -shaped 
 valleys ? 10. Why did not the streams in 11 1 erode sharp V-shaped 
 valleys ? 11. Which parts of the valleys in 122 most nearly resem- 
 ble the valleys of 11 1 ? Why ? [12. Compare the steep valley sides 
 in 122 with the neighboring uplands, as to depth of soil ; as to 
 amount of bare rock ledge exposed.] 
 
 6. [1. A small part of the Sierra Nevada mountains is shown 
 in 37 1. Locate this district on Plate 40. In what part of what 
 state is it ? What is the scale of the map (miles to an inch) ? the 
 contour interval ? 2. What is the altitude of the upper valley of 
 Turnback creek ? 3. Is the valley floor there narrow or broad ? 
 4. How much higher than this valley floor are the hills 2 mi. to the 
 W. ? 5. How deep are the valleys of Tuolumne river and its north 
 fork? Are they broad or narrow floored? Are the valley sides 
 steep or gently inclined ? 6. By what sort of a valley is the open 
 upland valley of upper Turnback creek connected with the deep 
 and narrow valley of Tuolumne river ? 7. How many other creeks 
 
THE SCULPTURE OF MOUNTAINS 49 
 
 show similar features ? 8. Compare the uplands, the upland hills 
 (or mountains), the deep main valleys, and the side valleys of this 
 district in the Sierra Nevada with corresponding features in 12 2. 
 9. Why may Tuolumne river be described as "revived"? 10. Ex- 
 plain the origin of the deep valleys of this district. 11. A small part 
 of the Front range of the Eocky mountains is shown in 37 2. Locate 
 this district on Plate 40. In what part of what state is it? What 
 is the scale (miles to an inch) ? the contour interval ? 12. In this 
 part of the Kocky mountains do the highest summits rise in sharp 
 peaks and ridges, or in a broad rolling highland ? 13. What is the 
 general altitude of the highland area ? 14. How deep are the valleys 
 below the highland? 15. What is the general altitude of the val- 
 ley floors ? 16. Do you think the valleys may be worn much deeper 
 in future ? Explain. 17. What is the probable origin of the forms 
 here shown ?] 
 
 7. 1. In 12 2 which parts of the main river (indicate by letters 
 A, B, etc.) flow in steep, rock-walled gorges or canyons? on plains? 
 2. What is the average fall of the river in the farther gorge (length 
 here shown, 4 mi.) ? in the nearer gorge (length, 11 mi.) ? on the 
 farther plain (river length, 11 mi.) ? on the nearer plain (river 
 length here shown, 4 mi.) ? 3. Will the river current be faster or 
 slower in gorge CD than in the corresponding part of ill? 4. Com- 
 pare the breadth of this part of the river in the two figures ; explain 
 the difference. 5. In 16 9 a profile along the main river of 11 1 is 
 shown (looking E.) by the line A'E' ; the main river of 12 2, by A"E". 
 Lay a ruler (or straight edge of sheet of paper) along the part A "B", 
 and compare its slope with that of the other parts. 6. How is the 
 depth of the gorge CD indicated in 16 9 ? What is the depth in feet ? 
 (See the vertical scale in 16 9.) 7. What relation exists between 
 depth of gorge and amount of upwarping ? 8. Where would you 
 go in 122 to get the best view of the deep rock structures that 
 underlie the upwarped uplands ? NOTE : The complicated disorder 
 of rock structure in such districts as are here considered is illus- 
 trated in the front corner sections of 16 13, and (less distinctly) in 
 
50 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 the shading of the canyon walls in that figure ; see also the front 
 section of 16 20. 
 
 8. 1. Why may the dotted area B-C, 12 2, be described as a basin 
 plain? 2. Where have the layers of gravel and sand, or alluvial 
 deposits, which cover this plain, come from? 3. The thickness of 
 these alluvial deposits, determined by deep wells bored at various 
 points, is shown by vertical lines beneath the river profile B"C", 
 16 9 ; draw a curve through the lower end of these vertical lines. 
 4. What does this curve represent? Compare it with the curve 
 C"D" in the same figure. 5. Why may the inclosed district occupied 
 by the basin plain be described as having been bent down, or down- 
 warped? 6. Why have layers of gravel and sand been deposited in 
 the down-warped area? What is their greatest total thickness? 
 [7. What mountains inclose the great plain of the " valley of Cali- 
 fornia" on the E. and W. ? (DE, 265.4, 267.2 ; DP, 288.5, 291.1- ; 
 G, 161.1 ; T, 68.2.) 8. The mountain valleys decrease in depth 
 toward the great plain; there the streams flow out on nearly flat 
 alluvial fans, which unite to form the great alluvial plain of 
 the "valley" (over 300 mi. long, about 50 mi. wide). 9. Point 
 out similar features in 122. 10. What is the probable origin of 
 the "valley of California"? 11. By what two chief rivers is it 
 drained? Through what "drowned valley" (or bay) do the river 
 waters reach the Pacific ocean ?] 
 
 9. 1. If the warping in the region of 11 1 had taken place very 
 rapidly, and raised the high-crested barrier MM'Q'Q, 12 2, across the 
 main river course, and the river had been stopped for a time, where 
 would a large lake have been formed ? 2. Where would the rising 
 waters of such a lake have found an outlet ? Why ? (The upwarp- 
 ing of the region NE. of the district here shown is supposed to be 
 higher than the line MM'Q'Q.) 3. There is no sign of a lake (except 
 the small oxbow lakes, made by the river) in the basin plain ; and 
 the gorge CD has been eroded along the course that the river fol- 
 lowed previous to (or antecedent to) the warping. 4. Then what 
 must be concluded as to the rapidity of the warping in this region ? 
 
THE SCULPTURE OF MOUNTAINS 51 
 
 5. What must be concluded as to the rate of upwarping of the arch 
 MM'Q'Q, 12 2, as compared to the rate of down-cutting by the river 
 in the gorge CD ? 6. Why may the river in the gorge CD be classed 
 as an antecedent river ? (DP, 258.2.) [7. The Sacramento river has 
 its upper course on the broad basin plains of NE. California. Locate 
 it on Plate 40. 8. Through what mountains does it then flow west- 
 ward ? What is the origin of these mountains? (See 6, above.) 
 
 9. In these mountains the upper Sacramento river follows a deep, 
 steep-sided, narrow gorge. To what class does this river belong ? 
 
 10. The river Meuse flows N. from the open country of N. France, 
 through a deep, narrow gorge in the arched Ardennes highlands to 
 the lowlands of Belgium ; locate the Ardennes on Plate 43. (See also 
 DP, Fig. 160.) The highlands have a gently rolling surface ; their 
 broad crest extends E.-W. at an altitude of (about) 300-400 meters. 
 The walls of the Meuse gorge and its side gorges show greatly 
 disordered rocks. 11. Point out similar features in 122. (NOTE: 
 There is nothing in N. France to correspond to the basin plain 
 BC, 12 2.) 12. What do you think is the origin of the Ardennes ? 
 13. To what class, does the Meuse river probably belong ? 14. Do 
 you think that the uplift of the Sierra Nevada and the Ardennes 
 was sudden or gradual ? Why ?] 
 
 10. 1. Draw tn 12 2 a broken [red] line from Q' (W. of gorge CD) 
 northward along the divide between the E.-sloping drainage area of 
 the main river and the W.-sloping drainage area of several smaller 
 rivers. 2. Where is the greatest change in this divide from the 
 corresponding divide in 11 1 ? 3. Why may stream K', 12 2, be de- 
 scribed as having been beheaded by warping ? stream K, 12 2, as 
 diverted by warping ? 4. Why has part of stream K been diverted 
 by warping, while the main river A E has held its antecedent course 
 in spite of the warping ? 5. What sort of rivers (as to size) would 
 most likely preserve their antecedent courses in a slowly warping 
 region ? 6. Draw broken and dotted [red] lines to mark some of 
 the divides and subdivides of the small rivers F, G, H, in 12 2. 
 7. Are the divides and subdivides sharp and definite, or broadly 
 
52 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 rounded and indefinite ? [8. Draw similar [red] divides and sub- 
 divides in 37 1 and 37 2. Are the divides sharp or rounded ?] 
 
 11. 1. What is the form of the waste (alluvial) deposits laid 
 down in 12 2 by the rivers and streams at the base of the upwarped 
 S. and W. slopes ? (DE, 265.2 ; DP, 288.3 ; G, 42.8 ; T, 66.5.) 
 2. How many such forms can you count in 12 2 ? 3. Were these 
 deposits made because of down-warping of the foreground (com- 
 pare front borders of 11 1 and 12 2), or because of increase in the 
 load of the streams ? 4. Which of these fans may be described as 
 independent ? which as laterally confluent ? [5. Draw a [red] line 
 to represent a road running E.-W. about a mile N. of the front 
 border of 12 2 . Would it ascend or descend as it approaches the 
 rivers F, G, If, J, DE ? Explain. 6. Draw [blue] lines to represent 
 each of these rivers in a new course on its fan. What difficulties 
 would these river changes impose on road construction ? 7. Draw 
 a similar E.-W. road in 11 1. How does its relation to the streams 
 differ from that of the road in 12 2 ?] [8. Why may the surface of 
 a fan be described as aggraded, in contrast to that of a valley, which 
 is said to be degraded ? 9. What effect may the aggradation of a 
 fan have in diverting rivers from their former courses (compare 
 the lower courses of F, G, H, DE, in 11 1 and 12 2) ? in changing 
 the courses of small streams (examine the small streams E. and 
 W- of river DE, 122, and compare them with the corresponding 
 streams in 11 1) ? 10. How may a small stream be turned across a 
 former divide by the fan of a large river (examine the first stream 
 W. of D, in 122 and compare it with ill)? 11. Which parts 
 of the large river may be said to have a braided course (many 
 islands of gravel and sand, dividing it into several channels) ? a 
 free meandering course in a plain (flowing in large curves, suit- 
 able to its large volume) ? 12. Compare the fall of the river in its 
 braided and its meandering course.] [13. The Hwang-Ho, a great 
 river of China, flows out from a gorge in the mountains upon a great 
 fan of gentle slope, where the river course has repeatedly changed. 
 Locate the river on Plate 44. 14. Why is the river known as 
 
THE SCULPTURE OF "MOUNTAINS 53 
 
 " China's Sorrow " ? What are the dimensions (height and radius) 
 of its fan? (DE, 265.9-; DP, 289.2-; T, 67.6.)] 
 
 12. 1. Which parts of 122 present forms due to revived erosion 
 following upwarping ? forms due to aggradation following down- 
 warping ? forms little changed from 11 1, except for warping ? 
 2. Where can parts of the former flood plain of the main river now 
 be seen in 12 2 ? 3. Why is more of the flood plain preserved near 
 the upper and the lower ends of gorge CD than about its middle ? 
 4. Where (near head, middle course, or lower course) are the best 
 preserved former flood plains of the smaller rivers and branch 
 streams ? Why ? 5. In what part of these streams are the deepest 
 new-cut valleys ? 6. Why are the new-cut valleys less deep near 
 the base of the sloping (upwarped) upland than in the mid-slope 
 of the upland ? deeper at mid-slope than farther upstream in the 
 highland ? [7. Why have the small tributaries of the main river in 
 gorge CD cut new valleys (side gorges) of so much greater depth 
 than the new-cut valleys of streams F, G, etc. ? 8. Examine 16 13. 
 To what part of 12 2 does it (in a general way) correspond ? 9. Do 
 the side streams in 16 13 make accordant or discordant (hanging) 
 junctions with the main river ? 10. Examine 16'14. To what part 
 of 12 2 does it (in a general way) correspond ? 11. Are the stream 
 junctions here accordant or discordant (hanging) ? 12. Explain 
 why accordant junctions prevail in one case and discordant junc- 
 tions in the other. 13. If a large tributary joined the main river in 
 the gorge CD, 122, would the junction be accordant or hanging? 
 Why?] 
 
 13. [1. Locate a city on the SW. lowland of 12 2 ; another on the 
 basin plain; some villages in the NW. and in the SE. corners ; give 
 a name to each city and village. 2. Which settlements may be most 
 easily connected by roads and railroads ? Why ? 3. Mark dotted 
 [red] lines to indicate roads from the city on the basin plain to the 
 other settlements. (Avoid new-cut valleys as far as possible ; if they 
 are crossed, the road should be laid obliquely on the valley sides, 
 as in 16 14.) 4. Draw a [red] line to show a railroad connecting 
 
54 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 the two cities, and passing over the arched highland. (The rail- 
 road must ascend the slope obliquely. Why? If it crosses new- 
 cut valleys, imitate the route shown in 16 14.) 5. Where would this 
 railroad cross the crest of the highland in 12 2 to best advantage ? 
 Why? C. Draw another [red] line to show a railroad connecting 
 the two cities by running through the river gorge. (Part of such a 
 railroad is illustrated in 16 13.) 7. State some of the difficulties and 
 some of the advantages of each railroad route. 8. Which parts of 
 12 2 might be cultivated for lowland crops ? for highland crops 
 (hardy grains) ? 9. Which parts would probably remain forested ? 
 10. Which parts are exposed to floods ? 11. Is the main river 
 navigable ? 12. Which parts of it are obstructed by many shoals ? 
 by rapids and low falls? (See 16 13.) 13. The first Pacific railroad 
 that was built (1866) to connect the cities of the eastern and cen- 
 tral United States with those on the Pacific slope crosses the high- 
 lands of the Sierra Nevada in California ; its irregular route over the 
 crest of the highland is shown on the Colfax, California, map, U. S. 
 G. S. 14. A railroad in Colorado follows the Arkansas river through 
 the deep, narrow, steep-walled gorge that it has cut through the Front 
 range of the Rocky mountains. (See Canyon City, Colorado, map, 
 
 14. 1. Note that Plate 13 is passed by for the present. Plate 14 is 
 in two parts, a SE. part (14 3) and a NW. part (14 4), representing 
 a third and a fourth stage in the history of the district, of which the 
 first and second stages are shown in 11 1 and 12 2. For the present 
 disregard 14 4. 2. Compare the three-fork valleys of river G in 12 2 
 and 14 3, as to altitude of highland above headwaters ; depth of 
 new-cut valleys (valleys of revived erosion); sharpness of dividing 
 ridges ; amount of neighboring uncut upland or highland. [3. Shade 
 lightly [red] some of the uncut uplands or highlands in 143.] 
 4. What has happened since 122 as to upwarping? as to erosion 
 of valleys ? as to destruction of highland surface ? as to growth 
 of alluvial fans,? 5. Which differences between 122 and 143 
 have been produced by upwarping ? by erosion ? by deposition ? 
 
THE SCULPTURE OF MOUNTAINS 55 
 
 6. Follow line WW, 143, and compare its course with the corre- 
 sponding line in 12 2. 7. Draw a similar line XX,' 14 3. 8. Why does 
 so little uncut highland remain along this line ? 9. Why are the 
 ridges sharp-crested for most of their length ? 10. Draw in 16 8 
 cross profiles for the branching valleys of river G, 14 3, a little S. of 
 line WW, and along line A'A". 11. Compare the low mountains near 
 the E. border of 11 1 with the corresponding parts of 12 2 and 14 3, as 
 to change of altitude ; as to change of form. [12. Draw profiles 
 in 1616 to illustrate the original (xxx) and the present (+ ++) 
 form of these mountains.] 
 
 15. 1. The altitudes of points on the line NN', 14 3, are indicated 
 in 16 15 by dots in squares ; of points on neighboring streams by 
 double dots. 2. Draw in 16 15 the curve of the upwarped surface 
 (as if it were uncut) along the line NN', 14 3 ; draw the profile of the 
 neighboring streams. 3. AY hat is the average fall of the S.-flowing 
 stream ? Why may it be called a torrent ? 4. Draw a light [red] 
 line MM', 14 3, along the divide between the N.-flowing and the 
 S.-flowing streams. AYhich part of the divide is sharply defined ? 
 AYhich part is somewhat indefinite ? Explain. 5. Compare this divide 
 with the corresponding divide in 12 2 as to sharpness ; as to num- 
 ber and steepness of its ascents and descents. 6. Draw broken and 
 dotted [red] lines along some of the divides and subdivides of rivers 
 F, G, and H, 14 3, and compare them with the corresponding divides 
 in 11 1 and 12 2, as to sharpness. 7. Why are some of the ridges and 
 mountains of 14 3 flat-topped ? [8. Certain ranges of the Tian Shan 
 mountains in central Asia (locate on Plate 44) have flat tops at alti- 
 tudes of from 10,000 to 12,000 feet ; they are dissected by deep val- 
 leys with steep walls, in which the disordered structure of the mass 
 is clearly shown. A small part of such a range is shown in 14 3 a. 
 
 9. AYhat two processes have probably produced such mountains ? 
 
 10. The dissected slope between the plateau of central France (NAY.) 
 and the lowlands near the Mediterranean (SE.) is called the Ce- 
 vennes mountains ; locate on Plate 43. Their structure is greatly 
 disordered; their ridges and spurs decrease in height, and their 
 
56 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 valleys decrease in depth to the SE.; most of the ridges have sharp 
 and narrow crests, between steep-sided, sharp-V valleys, but some 
 of the ridges are topped with even uplands, resembling the surface of 
 the (as yet) undissected plateau farther NW. 11. What shares have 
 warping and erosion had in producing the Cevennes ?] 
 
 16. 1. Why may the name pass be given to some of the depres- 
 sions in the mountain crest line MM', 14 3 ? 2. How are the passes 
 related to the neighboring valleys ? 3. Is a pass found at the head of 
 each small branch of the middle fork of river G ? Explain. 4. Of 
 several neighboring passes, which one would be most used ? Why ? 
 [5. Draw a line (light on first trial, heavy afterwards) to show a road 
 (or trail) from the southern lowland, 14 3, over the lowest pass in 
 the crest line MM' to the inner basin BC. (Where the valley slopes 
 are very steep, the road (or trail) may have to zigzag, as in 1622.) 
 
 6. Draw a stronger line (light, at first) showing a railroad (see 
 16 22) from the fan of stream H, 14 3, obliquely ascending the slope 
 W. of valley H, and then making its way to the inner basin BC. 
 
 7. Draw a dotted line to show the path by which cattle might be 
 driven in summer from villages on fan F to highland pastures 
 (HP). 8. What peculiar feature is seen in the valley next NW. of 
 the highland pastures ? 9. How may it be related to a lake ? 
 10. What disaster may happen when the lake overflows ? (DE, 
 193.5- ; DP, 181.5- ; (7,107.2; T, 97.4.)] [11. Excellent roads of 
 moderate grade have been built over many passes in the Alps, where 
 there is much travel (G, Fig. 250; T, 185); but in most mountains 
 the roads are steep and rough. Many ranges are crossed only by nar- 
 row trails. A railroad tunnel (Great Northern R. K.) passes under 
 the crest of the Cascade mountains in Washington, between the 
 upper parts of two opposite valleys. When the railroad was first 
 built it ascended over the pass ; the tunnel was made afterwards 
 to lessen the ascent. (See Skykomish, Washington, map, U. S. G. S.) 
 Another line (Northern Pacific R. R.) tunnels through two of the 
 Rocky mountain ranges in western Montana, and through the Cas- 
 cade mountains in Washington. (See Livingston, Montana, and 
 
THE SCULPTURE OF MOUNTAINS 57 
 
 Snoqualmie, Washington, map, U. S. G. S.) Three long tunnels have 
 been cut under passes in the Alps, for the passage of important 
 railroads from Switzerland or SE. France to N. Italy (see T, Fig. 
 186); one of these tunnels (the Simplon tunnel) is 11.9 mi. long; 
 seven years (1898-1905) were spent in cutting it, and it cost over 
 $16,000,000.] 
 
 17. 1. Now examine 14 4 (the basin plain stands about 1000' 
 higher in 14 4 than in 14 3) and state the chief differences between 
 its mountain range QQ' and the corresponding parts of 122, as to 
 height ; as to form ; as to depth of valleys ; as to ease of travel. 
 
 2. By what two processes have these differences been produced ? 
 
 3. To what process do the mountains of 14 4 owe their altitude ? 
 their form ? 4. Why is the term sculpture appropriate in connec- 
 tion with the form of such mountains ? 5. What relation exists 
 between amount of uplift and depth of sculpture ? 6. Draw a [red] 
 line along the mountain crest from Q to Q', 144. 7. Why are none 
 of the mountains flat-topped, like some of the summits in 14 3 ? 
 8. Are the passes in the range QQ', 14 4, easier or more difficult to 
 cross than the passes in the range MM', 14 3 ? Explain. 9. Draw a 
 [red] line in 14 4 from O at the W. base of the range, up the spur 
 ridge, over the peak 0', and down the spur ridge to O" at the E. base. 
 10. Where, on this line, are parts of the original upwarped surface 
 least eroded? Why? 11. Draw a curved [red] line from O to O" 
 to represent the arched profile that the upwarped highland might 
 have had if no erosion had taken place. (Let the crest of the arched 
 profile be 1000' or 2000' higher than 0' ; see 1620.) 12. How much 
 upwarping has taken place here since 11 1 ? since 12 2 ? 13. Com- 
 pare the mountain profile O'O", 14 4, with the (supposed) arched 
 highland profile, as to height ; as to form. 14. Make a statement 
 regarding the mountains of 14 4, similar to this : " A statue is 
 smaller than the block of marble from which it has been carved." 
 15. Compare the ridges NN 1 , 143, and O'O", 144. Make a state- 
 ment regarding these ridges, similar to this : " After a knife blade 
 is sharpened it is smaller than when it was dull." 
 
58 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 18. [1. Why is much bare rock exposed on the peaks, ridges, and 
 spurs of 14 4 ? 2. Why does much coarse angular rock waste lie on 
 the slopes below the rock ledges ? 3. Whence and how is the waste 
 supplied to the slopes? 4. Why is it coarse and angular? 5. What 
 becomes of it ? 6. Draw in 16 20 [red] lines along the divides and 
 subdivides, and [blue lines] along the streams. 7. How are the 
 divides and subdivides arranged with respect to the stream and its 
 branches ? 8. Where are the streams steepest ? 9. Are the stream 
 junctions in 1620 and in 144 accordant or hanging? Why? 10. The 
 dotted parts of i<> 20 represent waste-covered slopes. Why may the 
 waste be described as " slowly streaming"? 11. Select in 144 a 
 spur extending from a mountain peak to the mountain base ; shade 
 [red] the parts where bare ledges prevail (see 16 20) ; select an- 
 other spur, and shade [blue] the waste-covered slopes. 12. Where 
 is a landslide represented in 14 4 ? Why did the landslide take 
 place? (DE, 193.6; DP, 181.5 ; G, 107.2 ; 7', 97.4.) 13. What lias 
 happened since the slide took place ? 14. How high are the walls 
 of the scar that was left by the slide ? About how long is the 
 slide ? How deep is the trench cut in the slide ? How much higher 
 has the lake (back of the slide) been than it is now ?] 
 
 19. 1. The profile of the main river, 14 4, is shown by line A iv E iv , 
 169. In what parts of 144 has the river the strongest slope (lay a 
 rule, or straight edge of paper, along the profile ^4 iv B iv , 16 9) ? the 
 most rapid current ? 2. How thick is the great fan of the main 
 river at the front of 144? 3. Why does the river now flow on a 
 higher profile than in 12 2? (Compare profiles A"E" and A iv E iv , 16 9.) 
 [4. If the river is at a greater altitude than before, why is the 
 gorge of 14 4 deeper than that of 12 2 ? 5. What relation exists 
 between the depth to which the gorge CD, 144, has been eroded, 
 and the height to which the original surface has there been up- 
 warped ? Explain.] 6. Are the junctions of side streams and 
 river, in the gorge, 144, accordant or hanging ? [7. Compare with 
 12 2 and 16 13, and explain. 8. What does this suggest as to the rate 
 of upwarping at the time of 14 4, as compared to rate at time of 
 
THE SCULPTURE OF MOUNTAINS 59 
 
 12 2 ?] 9. Estimate the thickness of the gravel and sand deposits 
 in the basin EC (see 16 9). 10. Compare the size of the fan S. of 
 the mountains in 14 4 and 12 2. 11. In which figure may all the fans 
 be described as "laterally confluent"? Why? 12. In which figure 
 may the lowland surface bordering the mountains be described as a 
 " piedmont deposit of mountain waste " ? [13. Compare the oppor- 
 tunity for intercourse and trade between the people of the W. plain 
 and the inner basin plain in 12 2 and 14 4. 14. Draw a dotted [red] 
 line in 14 4 to show (as much as can be seen of) a trail over the 
 mountains, connecting the two plains. (Avoid crossing the larger 
 streams, if you can ; see the broken line, 16 20.) 15. Describe a 
 trip on foot over the range.] 
 
 20. [1. 37 3 is a small part of the Rocky mountains ; locate it on 
 Plate 40. In what state is it ? What is the scale (miles to an inch)? 
 the contour interval? 2. Mark H on the highest summit. What is 
 its altitude ? What are the altitudes of several other summits? of 
 Conundrum creek? 3. How high are the summits above the creek? 
 4. Are the peaks and ridges flat-topped or sharp ? 5. What is the 
 usual difference between peak and pass altitudes in the mountain 
 crests? 6. Draw a [red] line along the crest of each mountain 
 ridge in this figure; broken [red] lines from the crest down several 
 spurs. 7. Mark S on a short spur that ends between the forks 
 of a branch of Conundrum creek ; L on a long spur that extends 
 without dividing from the mountain crest to Conundrum creek ; D 
 on the separate lower ends (or spurlets) of a spur that is divided 
 by short branches of Conundrum creek. 8. Print 5 on a spur that 
 divides into five spurlets; print 6 on a slope that is divided into 
 six short spurs between the forks of one branch of Conundrum 
 creek. 9. Draw a dotted [red] line to show a trail from some 
 point on Conundrum creek to the W. border of the map. 10. How 
 did you determine where the trail should cross the W. range ? 11. Is 
 the sculpture of these ranges farther advanced than the sculpture 
 of the mountains in 37 1 and 372? How can you tell? 12. Of 
 these three mountains, which would you describe as maturely 
 
60 EXERCISES IX PHYSICAL GEOGRAPHY 
 
 dissected ? which as in an early (young) stage of its cycle of ero- 
 sion ? 13. 374 is part of the San Antonio mountains; locate on 
 Plate 40. In what part of what state is it? What is the scale? 
 the contour interval ? 14. What is the greatest altitude shown ? 
 15. Is the dissection immature or mature ? 16. Compare in 37 3 and 
 37 4 the pattern of the contours ; the size of the spurlets. In which 
 of these two maps might the dissection of the mountains be 
 described as of finer texture ? 17. Describe the form of the S. part 
 of 37 4. Explain its origin. What name is given to such forms ? 
 Where does a similar form occur in 14 4 ? 18. The basin plain or 
 " vale " of Kashmir lies between the outer and the inner ranges 
 of the lofty Himalaya mountains in NW. India; locate it on 
 Plate 44. It is 100 mi. long by 50 mi. wide, and 5000' above sea 
 level ; the passes in the inclosing mountain range have an altitude 
 of over 10,000'. The vale is occupied by a people who differ in 
 various ways from the people of the outer piedmont plains. 19. The 
 river Jhelam flows from the inner basin plain through a deep, nar- 
 row, steep-walle'd gorge in the inclosing mountains to the outer 
 plains ; the native people have therefore crossed the inclosing 
 range for centuries only by a high pass ; in recent years British 
 engineers have built a road part way through the gorge. (DP, 
 284.6-.) 20. Point out some similar features in 14 4.] 
 
 21. Now turn to Plate 13. NOTE : 13 5 and 13 6 represent later 
 stages of the district already studied in 11 1 to 14 4; for the present do 
 not consider 136. 1. Compare the W. range in 144 and 135 as to 
 height ; as to sharpness of peaks, ridge crests, and spurs ; as to slope 
 of valley sides ; as to steepness of stream profiles. Explain the dif- 
 ferences. 2. Which one of these two ranges has the greater amount 
 of bare ledges? of waste-covered surface? (See 16 19 and 1620, in 
 which the waste-covered surface is dotted.) 3. By what process 
 can you account for the differences ? 4. When did the greater 
 amount of upwarping take place, between 12 2 and 14 4 or between 
 14 4 and 13 5 ? 5. Why may the waste-covered slopes in is 5 be 
 described as " graded " ? the bare rock ledges as "not yet graded"? 
 
THE SCULPTURE OF MOUNTAINS 61 
 
 the rounded summits, crests, and spurs as " subdued " ? (DE, 204.8- ; 
 DP, 187. 1-.) 6. Draw in the upper part of 16 17 a cross profile of 
 the spurs and valleys on the line XX', 13 5. 7. Compare it with pro- 
 file A' A*', 16 8, and explain the differences. 8. Compare the main 
 river in 14 4 and 13 5 as to altitude at ^4 and E ; as to fall and 
 velocity from A to E ; as to amount and texture of waste received 
 from tributaries. 9. In a river of given volume what relation exists 
 between its load (amount and texture of waste) and the slope to 
 which it may wear down its profile ? (DE, 254.9 ; DP, 243.2.) 
 10. Why have the rivers of 13 5 begun to degrade the alluvial fans 
 and plains that they previously aggraded ? NOTE : The remaining 
 parts of the fans and plains (dotted in 12 2, 14 3, and 14 4) are 
 unshaded in 135. 11. What features in the valley CD, is 5, indi- 
 cate whether the river is or is not still deepening its valley ? 
 Explain. 12. Why was not the widening of the valley bottom 
 begun at an earlier stage (as in 12 2 or 14 4) ? 13. What can you 
 infer from this as to whether the warping and uplift of the region 
 is still going on or not ? [14. The Black mountains of North Caro- 
 lina possess many of the features here described. Their summits, 
 ridges, and spurs are rounded ; their slopes are graded, with few 
 cliffs or ledges ; their valleys are usually open ; their streams 
 commonly, have narrow flood plains.] 
 
 22. [1. What features in 16 10 indicate that the river has been 
 cutting laterally (sideways) as well as downwards during the 
 erosion of its gorge ? 2. Draw a full [or red] line along the outer 
 bank of each river curve (or meander) in 1C 10, 11, 12 ; draw a 
 dotted [or blue] line along the inner bank of each curve. 3. Are 
 the dotted [or blue] lines all on the same side of the river ? How 
 are they arranged ? 4. Let the steeper parts of the gorge wall be 
 called the undercut slopes, or undercut amphitheaters; shade them 
 lightly [red]. 5. Call the less steep parts the slip-off slopes, or slip- 
 off spurs ; dot them [blue]. 6. Explain why the preceding terms 
 are appropriate. 7. What relation exists in 16 10 between the outer 
 bank of a river curve and the undercut slopes ? between the inner 
 
62 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 bank and the slip-off slopes ? 8. In which one of 16 10, 11, 12, is 
 the river bordered by narrow flood-plain scrolls ? by wider flood- 
 plain scrolls? 9. Where are the flood-plain scrolls situated with 
 respect to the inner and outer banks of the river curves (or 
 meanders) ? with respect to the undercut slopes ? to the slip-off 
 slopes? 10. In 1G 10, 11, 12, draw a nearly straight line touching 
 the river curves on the right ; another on the left. 11. The space 
 included between each pair of lines may be called the meander belt. 
 How does its width change? 12. During the erosion of the gorge, 
 16 10, which was greater, downward river erosion or lateral river 
 erosion ? 13. During the development of the flood-plain scrolls, 
 16 11, 16 12, which was greater, downward or lateral river erosion ? 
 14. If the downward erosion (or deepening) of the gorge resulted 
 from the revival of river erosion by the upwarping of its district, 
 does the upwarping still continue or has it ceased, now that flood 
 plains are developing ?] 
 
 23. [1. Shade [light red] three undercut slopes on the W. side 
 of the main river gorge CD, 13 5 ; three on the E. side. 2. Mark 
 with [light blue] dots three slip-off slopes, or spurs, on each side of 
 the gorge. 3. Shade [light red] three flood-plain scrolls on each 
 side of the river in the gorge. 4. Are the flood-plain scrolls on the 
 up-valley side or the down-valley side of the spurs ? 5. Why may the 
 spurs that adjoin the flood-plain scrolls be described as "trimmed 
 on the up-valley side " ? (See also 16 21, looking across a valley.) 
 6. Why may the spurs on the farther side of the valley, 16 18, be de- 
 scribed as " nearly consumed " ? 7. With which stage of flood- 
 plain development, as shown in 16 11 (narrow flood-plain scrolls), 
 16 12 or 21 (broad flood-plain scrolls), and 16 18 (broad flood-plain 
 lobes}, do the flood plains in the gorge of 13 5 best correspond ? 
 8. With which stage of spur erosion, as shown in 1611 (little- 
 trimmed spurs), 16 12 or 21 (well-trimmed spurs), and 16 18 (nearly 
 consumed spurs), do the spurs in the gorge of 13 5 best correspond ?] 
 [9. Draw in 13 5 a broken [red] line to show a road, and a full [red] 
 line to show a railroad, crossing the W. mountain range. (See 
 
THE SCULPTURE OF MOUNTAINS 63 
 
 16 19 ; the road is here a single line, the railroad a double line.) 
 10. Draw a [red] line to show a railroad following one side of the 
 valley CD, 135. 11. What part of this railroad would have to be 
 built on steep slopes ? 12. A railroad of this kind follows the deep 
 meandering valley of the N. branch of the Susquehanna river in 
 Pennsylvania ; another follows the similar valley of the Mosel river 
 in W. Germany. (DP, 254.5.)] 
 
 24. 1. Examine 13 6 and compare it with 13 5, as to altitude ; as 
 to relief ; as to steepness of hillside (or valley-side) slopes ; as to 
 breadth of flood plains along small streams. 2. Explain the differ- 
 ences. 3. Which has been the more important, warping or erosion, 
 in causing the change from 11 1 to 12 2 ? from 13 5 to 13 6 ? [4. In 
 14 3 and 14 4 which is the more rapid, the deepening of the valleys 
 or the wearing down of the peaks ? 5. Answer the same question 
 for 13 5 and 13 6. 6. Explain the difference between the answers to 
 these two questions. 7. Is the wearing down of the summits faster 
 in 14 4 or in 13 6 ? 8. What conclusion is suggested by answers to 
 questions 5 and 7, as to the rate of valley deepening in 13 6 ? 
 9. Would you expect bare rock, thin soil, or deep soil on the sharp 
 divides of 14 4 ? on the rounded divides of 13 5 ? on the low divides 
 of 13 6 ?] 10. Draw in the middle of 16 17 a profile on XX', 13 6 ; 
 draw below this another profile representing a later stage of ero- 
 sion than 13 6 ; below this again a still later stage. 11. In what 
 way do these three profiles differ? 12. Would the change from 
 one to the other be quickly or slowly produced ? Why ? 13. When 
 the district here studied reaches a later stage of erosion than is 
 shown in 13 6, which one of the figures 11 1 to 13 5 will it most 
 resemble ? 14. What, then, is the probable explanation of the forms 
 shown in ill? 15. Such a district may be called a peneplain (that 
 is, almost plain). 16. What relation has a peneplain to baselevel ? 
 to the underlying rock structures (such as are shown in the front 
 sections of 16 13 and 16 20) ? 17. Suppose that part of a district like 
 the one here considered consisted of much more resistant rocks 
 than the rest. What features would you expect to survive in the 
 
64 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 area of the very resistant rocks, when the less resistant parts were 
 worn down to a peneplain ? 18. In which figure of this series 
 are such features represented ? NOTE : Such residual hills or low 
 mountains may be classed as monadnocks. (DE, 207.6 ; DP, 190.1; 
 G, 87.9 ; T, 298.6.) 19. If a seventli figure were drawn, represent- 
 ing a later stage than 13 6, where would you expect to see a group 
 of monadnocks ? [20. How do the monadnocks in 12 2 differ from 
 those in 11 1 ? 21. A large area in W. Siberia around Omsk is a 
 peneplain of small relief, with occasional monadnocks. Between 
 what mountains does this peneplain lie? by what river is it drained? 
 (See Plate 44.)] 
 
 25. [1. What two unlike processes are concerned in a "cycle of 
 erosion " ? NOTE : Let the successive stages of a cycle of erosion 
 be called "early youth," "youth," "early maturity," "full matur- 
 ity," " late maturity," " early old age," " late old age." 2. Which 
 of these terms may be used in describing the figures, 12 2 to 13 6 ? 
 3. Does 11 1 belong in the same cycle of erosion with the following 
 figures ? 4. What sort of movement interrupted the cycle of the 
 first figure and introduced the cycle of the later figures ? 5. In 
 what stage was ill when its cycle of erosion was interrupted? 
 6. In the early youth of a new cycle which parts of the surface 
 preserve forms little changed from the old age (peneplain) of a 
 previous cycle ? 7. In the stage of full maturity (strongest relief 
 and greatest variety of form), how would the divides differ from 
 their form in youth ? from their form in old age ? 8. How would 
 the load of the rivers differ in maturity and in old age ? 9. How 
 would the streams of youth differ from those of old age as to 
 slope ? as to the occurrence of falls and rapids ? 10. Which stage, 
 youth, maturity, or old age, occupies the longest time in a com- 
 pleted cycle of erosion ? 11. Is it necessary that a cycle of erosion 
 should continue without interruption (by uplift, warping, or depres- 
 sion) until late old age ? 12. Suppose that interruption by uplift 
 occurred at the stage of 13 5 ; describe the forms of the district 
 in a young stage of the new cycle of erosion thus introduced. 
 
THE SCULPTURE OF MOUNTAINS 65 
 
 13. What features would you expect in a region that had been 
 worn down to a peneplain (with a few monaduocks) in a long, 
 undisturbed cycle of erosion, and that had then reached early ma- 
 turity in a new cycle introduced by a broad uplift of GOO' or 800' ? 
 
 14. The Appalachian Piedmont belt of Virginia, the Carolinas, and 
 Georgia (locate it ; see DE, Fig. 100 ; DP, Fig. 117) is such a region ; 
 many other examples of peneplains, upwarped and more or less dis- 
 sected, might be mentioned. 15. Locate 37 5 on Plate 40. 16. What 
 is the general altitude of the uplands ? 17. How much higher is 
 Stone mountain than the uplands ? 18. How deep are the valleys 
 below the uplands ? 19. The uplands are part of the uplifted Appa- 
 lachian Piedmont peneplain. How many cycles of erosion are here 
 represented ? 20. What stage had the first cycle reached when it 
 was interrupted by regional uplift ? How can you tell ? 21. What 
 stage has now been reached in the new cycle of erosion ? How 
 can you tell ? 22. What term already used would apply appropri- 
 ately to Stone mountain ? 23. Make a list of the features which 
 characterize the youthful stage in a cycle of erosion ; the mature 
 stage ; the old stage.] 
 
 26. Define : 1, interfluve ; 2, well-defined divides, ill-defined 
 divides ; 4, an arched or upwarped district, [river beheaded by 
 warping,] torrent ; 5, revived or rejuvenated stream, sharp V- 
 shaped valley ; 8, basin plain, bent-down or down-warped basin ; 
 9, antecedent river ; 10, river diverted by warping, beheaded 
 by warping ; 11, alluvial fans, laterally confluent (alluvial) fans, 
 aggrade, aggradation, degrade, degradation, braided river coarse, 
 meandering river course ; 16, pass ; 17, mountain sculpture ; 
 [ 18, landslide ;] 21, subdued mountains ; [ 22, undercut slopes, 
 slip-off slopes, flood-plain scrolls, meander belt ; 23, trimmed spurs, 
 flood-plain lobes ;] 24, peneplain, residual mountain, inonadnock ; 
 [ 25, interruption of a cycle of erosion]. 
 
EXERCISE VI. VOLCANOES AND LAVA FLOWS 
 
 OBJECT. To illustrate the various forms of volcanoes and lava flows, 
 and the effects that they produce on land sculpture by rivers. 
 
 Preliminary. 17 1 to 19 8 of this exercise represent the same piece 
 of country (shown as a block, cut out from its surroundings), at 
 different stages in the history of a group of volcanoes and their 
 associated features. The NW. and SE. corners of the figures are 
 cut off to save space. The complete block would measure about 
 4 mi. N.-S. by 5 mi. E.-W. Scales of miles are marked on the S. 
 and W. baselines ; a scale of altitudes (feet) is given on the SW. 
 corner. The numbers on the upland indicate altitudes in feet above 
 sea level. Plates 17, 18, 20, 19, and 15 are used in this exercise [also 
 38 3]. Note that Plate 20 is to be used before Plate 19. 
 
 1. 1. What is the general altitude of the upland in 17 1 ? its gen- 
 eral measure of relief (general height of uplands over valley floors) ? 
 (The uplands are not level, but slope gently toward the valley sides, 
 as shown on the S. border of the block.) 2. What is the average 
 fall of river UV in feet per mile ? (Use scale on W. baseline for 
 river length.) 3. What is the altitude of the pass A' between the 
 valleys of river UV and of river YY'? 4. Draw a dotted [red] 
 line along the divide between the V and the Y river systems. 
 5. Draw a [pencil] line on a direct path from C to C"; from D to 
 D'. (Follow the heavy hachure lines downhill and uphill.) 6. Draw 
 to scale in 15 9 a cross profile of UV valley at CC' and DD'. 
 
 2. 1. What are the three chief events that have taken place in the 
 change from 17 1 to 17 2 ? 2. What is the height of the volcano sum- 
 mit above sea level in 17 2 ? above the neighboring upland ? the 
 diameter of its base (use scale on S. baseline) ? of its crater ? 
 [3. What is (roughly) the volume of the volcano ? NOTE : The 
 
 66 
 
VOLCANOES AND LAVA FLOWS 67 
 
 volume of a cone = area of base x -J- height ; the area of the (circu- 
 lar) base = 2>\ x square of radius.] 4. Why did the lava flow turn 
 S. in UV valley? 5. Is the lava flow higher along its middle or 
 along its sides ? 6. What effect has the flow had upon the position 
 of the junction of river ZZ with river UV? 7. What is the length 
 of the flow (use scale on W. baseline) ? average breadth of flow (use 
 scale on S. baseline)? thickness of flow at mid-length? (In an- 
 swering the last question compare altitude of flow surface in 17 2 
 with altitude of corresponding points in valley floor, 17 1.) [8. What 
 is (roughly) the volume of the flow ? NOTE : Multiply length x 
 average breadth x \ average thickness along valley line. 9. Which 
 has the greater volume, the cone or the flow ?] 
 
 3. 1. Why have several lakes been formed in 17 2 ? 2. Determine 
 the length, breadth, and greatest depth of lake A. 3. Why is the 
 outlet of lake A along the W. side (instead of the E. side) of the 
 lava flow ? 4. If the altitude of lake C is 1900', what is the aver- 
 age fall of river 7Fin feet per mile from the lake to the end of the 
 flow ? 5. Why is this average fall greater than that of river UV in 
 17 1 ? G. Why has a narrow gorge been cut along the W. side of 
 the lava flow of 17 2 between lakes A and C ? Why has a gorge 
 been cut on each side of this lava flow near its end ? 7. Why is 
 there no gorge along the E. side of the lava flow near F 1 ? 8. Esti- 
 mate the breadth and depth of each gorge. 9. Draw a [pencil] line 
 on a direct path from E to E', crossing lake A and going over the 
 volcano; from F to F'; from G to G'. [10. In 15 10 draw cross sec- 
 tions for the three profiles, showing in EE' the bottom of the lake, 
 the base of the volcano, and the passage or pipe up through which 
 the lava neck rose from its deep source ; in FF' the base of the lava 
 flow, and the old and new course of river UV; in GG 1 the base of 
 the flow, and the larger and smaller gorges.] 
 
 4. [1. A small volcano called Monte Nuovo (New Mountain) was 
 formed by sudden eruption on the N. border of the gulf of Naples 
 in 1538. (DE, 218.6; DP, 202.G ; T, Fig. 207.) 2. To what does 
 Monte Nuovo correspond in 172? In what part of Italy is it? 
 
68 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 (See Plate 43.) 3. A smooth cinder cone in California is believed to 
 have been erupted about 200 years ago ; a younger lava flow near 
 the cone produced Snag lake, so called because the dead trunks of 
 trees that grew before the eruption are still to be seen there. (DE, 
 219.8; DP, 203.8; also J. S. Diller, Bull. 79, U.S.G.S.; good de- 
 scription and many excellent plates.) 4. To what do these features 
 correspond in 17 2 ? In what part of California is Snag lake ? (See 
 Plate 40.) How far and in what direction from Mt. Shasta ? 5. In 
 1759 the volcano Jorullo (pron. Ho-rul-yo), in Mexico, was rapidly 
 built of lava and cinders, its crater rim rising about 700' over the lava 
 flows around its base ; fine cinders or ashes and dust were showered 
 on the cone, the flows, and the surrounding country. 6. Locate 
 Jorullo on Plate 41. How far and in what direction is Jorullo from 
 Popocatapetl ? The cone, lava, and ashes of Jorullo were barren for 
 many years, but they are now more or less covered with vegetation. 
 (DE, 219.1; DP, 203.1.) 7. Lava flows, cascading down high cliffs 
 in Arizona, are shown in Atlas, sheet V, of U.S.G.S., Monogr. II 
 (copied (in part) in DE, Fig. 113; DP, Fig. 129). 8. Where was 
 a lava cascade formed in change of 17 1 to 17 2 ?] 
 
 5. 1. 15 11 is a map, partly in 100' contours, partly in hachures, of 
 a volcano, its lava flows and a portion of the surrounding country ; 
 the contours are dotted on the non-volcanic surface ; the scale is 
 1 : 62,500. 2. What is the diameter of the cone at its base ? the 
 height of the cone above the hilly upland ? [the angle of slope 
 of its sides ?] 3. Draw [red] lines along the middle of each flow, 
 and shade lightly [red] the surface of the cone and flows. 4. Why 
 does the E. flow widen where its mid-line is 1650'? 5. About how 
 much higher is the mid-line of the E. flow than its N. border ? than 
 its S. border ? 6. What is the average fall along the mid-line ? 
 NOTE : The lava of flows as steep as those here shown must have 
 been viscous when erupted ; the more fluid the lava, the less the 
 slope of the flows when they solidify. 7. Draw dotted [blue] lines 
 to represent the (probable) stream courses before the volcano was 
 formed. 8. Shade [light blue] the four small lakes. Why were they 
 
VOLCANOES AND LAVA FLOWS 69 
 
 formed ? 9. Mark O at the lake outlets. 10. What is the altitude 
 of the outlets ? 11. Draw full [blue] lines to represent the present 
 streams, and darken the lines where gorges will be cut. 12. Why 
 is a single former stream now represented by two streams for part 
 of its length ? [13. Estimate the thickness of the E. flow where its 
 mid-line is 1400', 1700', 1800', and 2000'. 14. In what part of the 
 flow is its thickness greatest, close to base of cone, midway along 
 the flow, or near end? Why ?] [15. Draw in is 12, scale, 1 : 62,500, 
 with 100' contours, a volcano 2100' altitude at r, with lava flows 
 extending E. and SW. (The numbers by crosses (x) indicate alti- 
 tudes at middle and side of the flows.) 16. Indicate, as above, the 
 drainage before and after eruption. 17. Mark O at the outlets of 
 the several lakes. (Some of the outlets are close along the lava 
 flows ; one is across a divide between former streams, like X, n 2.) 
 18. Shade the lakes [light blue], and draw dark [blue] lines where 
 gorges will be cut. 19. What is the angle of slope of cone ? length, 
 breadth, greatest thickness, and fall per mile of mid-line of each 
 flow? length, breadth, and greatest depth of each lake? 20. Draw 
 lines to show the former [dotted red] and the present [full red] 
 divide between the NE. and the SW. river systems.] 
 
 6. 1. What are three chief differences between 17 2 and 18 3 
 directly due to volcanic eruption? 2. What has happened in 183 
 to lake B of 17 2 ? Explain. 3. What is the altitude of the W. 
 border of the large new lava flow near H, 18 3 ? 4. How much 
 higher is the surface of lake A in 183 than in 172? Why is it 
 higher ? 5. To what river does lake A overflow in 18 3 ? 6. Ex- 
 plain this change from 17 2. 7. How much higher has lake A been 
 than it is now ? (See X, 17 2.) 8. What new feature has been 
 produced along the outlet of lake A in 18 3 ? Explain. 9. Draw a 
 [blue] line along the outlet stream of the two small lakes W. of 
 the lava flow in is 3. 10. Why does the outlet stream follow this 
 course? 11. Draw a [red] line in 18 3 along the divide between 
 river systems VZ and Y'. 12. Why does this line differ from the 
 corresponding line in 17 1 ? 13. Compare the volume of river V at 
 
70 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 the S. border of 17 1, 172, 183; of river Y' at E. border of each 
 figure. Explain the changes. 14. In 18 3 why is the gorge of river 
 Z deeper than the gorge of river F? 15. Draw a [pencil] profile 
 line in 18 3 from H directly across the newer lava flow, over both 
 volcano summits, to //'; from -/ across both lava flows to ./'; from 
 K to K'. [16. In 15 10 draw cross sections corresponding to these 
 profiles, and show in section ////' the bottom of the newer lava flow, 
 the base of both volcanoes, and the pipes by which the lava has 
 risen ; in sections .7.7' and KK', the surface and bottom of each flow, 
 the newer one burying the gorge previously eroded along the W. 
 border of the older one (see 17 2).] [17. AVhat large lake in Central 
 America is due to a volcanic barrier? (DE, 231. 9-.) Locate this 
 lake on Plate 41. 18. What river has thus been made to flow across 
 the former " continental divide " between the Atlantic and Pacific 
 oceans ? Explain.] 
 
 7. 1. What are the chief changes from 18 3 to 184 as to vol- 
 canoes ? as to lava flows ? as to lakes ? as to lake outlets ? (Lake 
 Y and river Y' are separated by a divide, 2900', on the NE. 
 border of the NE. lava flow.) 2. What is the height of the great 
 volcano above the uplands around its base ? the diameter of its 
 base ? [its volume, compared to that of the volcano in 17 2 ?] 
 3. What change has taken place in the form of the larger vol- 
 cano of 18 3 ? 4. Explain why it may now be called a " dissected 
 volcano." 5. What has become of the smaller volcano of 18 3 ? 
 6. Why are the ravines of so moderate a depth on the slopes of the 
 great volcano, 18 4 ? (Many ravines, eroded to a considerable depth 
 while the volcano was smaller, may have been filled with lava and 
 ashes by later eruptions.) [7. Fujiyama, a great volcano in Japan 
 (between Tokyo and Kyoto ; locate on Plate 44) is a nearly symmet- 
 rical cone rising about 14,000' close to the seacoast ; its slopes are 
 but moderately dissected by radiating ravines. In what part of 
 what island is this volcano ? 8. Mt. Shasta is a large volcano of 
 similar height in California. (DE, 229.9- ; DP, 214.1 ; G, 211.9 ; T, 
 121.5 ; also J. S. Diller, Nat. Geogr. Monogr. No. 8.) 9. In what 
 
VOLCANOES AND LAVA FLOWS 71 
 
 part of California is Mt. Shasta ? (See Plate 40.) What is its alti- 
 tude ? Compare its dissection with that of the larger and smaller 
 volcanoes of 18 4.] 
 
 8. 1. How many lava flows are shown in is 4 around the base of 
 the great volcano? 2. What is the relative age of the SW., S., 
 and SE. flows ? Explain. 3. How many different lava flows are 
 shown on 17 2, 18 3, and 18 4 ? (Include the two small flows in the 
 center of is 3, and the several larger flows shown in section on the 
 S. face of 18 4.) 4. What is the total thickness of the four flows 
 shown in section on the S. face of 18 4 ? 5. Why is the under sur- 
 face of these flows uneven ? [6. How can you estimate (roughly) 
 the relative duration of the time intervals between the outpouring 
 of these four flows ? 7. Were they about equal or very unequal ?] 
 NOTE : The flows that issue from the flanks of a volcano (as here 
 or SW., S., and SE.) are probably supplied through great under- 
 ground fissures, splitting the earth's crust outward from the cen- 
 tral pipe of the cone. The lava that solidifies underground in such 
 fissures forms dikes. [8. Numerous barren lava flows are found 
 around the volcanoes of Mexico. The surface of the lava is often 
 so rough as to be nearly impassable. Why ? (DE, 227.7 ; DP, 
 209.8 ; G, 198.7.) 9. Such flows are called malpais (bad country). 
 A large malpais near (S. of) the City of Mexico was formerly 
 the resort of robbers and outlaws, who, knowing their way over 
 it, found refuge from pursuit in its caverns. In what part of 
 Mexico is this malpais ? (See Plate 41.)] 
 
 9. 1. About how far W. of its course in 17 1 is river V in 18 4 ? 
 2. Was the displacement made all at once ? In how many partial 
 displacements ? (Examine 17 2, 18 3, and 18 4.) 3. Draw a [red] 
 line in is 4 along the divide (as far as you can see it) between 
 river Y' and the other rivers. 4. Compare in 17 2, 18 3, and 18 4 the 
 volume of river Y' ; of river V; explain the changes. 5. Where 
 do rivers V and Z now (probably) unite? 6. How much wider 
 than now was the large SW. lava flow when it was poured out ? 
 Explain. [7. Draw in is 13 a cross section of valley V, 18 4, at LL'; 
 
72 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 of valley Z at MM'. Why are these two valleys not of the same 
 shape ? 8. Indicate (dotted lines.) in sections LL' and MM' the 
 original upland surface and the original border of the lava flows. 
 9. What relation exists between the original border of the lava 
 flows and the present river courses ? 10. Draw in 15 14 a cross 
 section from N to N', 18 4, showing the original upland and valley 
 profile, and the pipes, cones, and flows that are crossed by the sec- 
 tion. 11. Which lava flows of 18 3 and 18 4 are shown in this NN' 
 section ? How many volcanic pipes are shown ?] 
 
 10. Turn to Plate 20. (Plate 19 is passed by for the present.) 
 1. Does 20 5 show any signs of volcanic action later than the latest 
 lava flow of 18 4 ? 2. What changes has the great volcano suffered ? 
 Why may it be called a dissected volcano ? 3. Why do its valleys 
 radiate from its center ? How many such valleys do you think 
 there are in the larger volcano ? in the smaller volcano ? 4. To 
 what class do these valleys belong ? [5. How many feet has the 
 height of each volcano been decreased ? (Lay a piece of tracing 
 paper, about 6x7 inches, on 18 3 ; mark the SE. and S W. corners 
 of the block base and the summit of the W. volcano ; lay the trac- 
 ing paper in the same position on 18 4, and mark the summit of the 
 great (E.) volcano. Lay the paper in the same way on 20 5, and 
 mark the summit of each volcano ; measure decrease of height by 
 vertical scale on SW. block corner.) 6. How many feet has the 
 upland, not covered by lava, as at the SE. corner of the block, 20 5, 
 been worn down ? (Use the same tracing paper and trace the 
 front profile of upland near SE. corner from n 1 and 2, 18 3 and 4, 
 and 20 5.) 7. Why has the upland not been worn down so much 
 as the volcanoes ? 8. How many feet has river V cut down its 
 present valley near the SW. corner of the district ? (Trace front 
 profiles of valley, from 18 3 and 4 and 20 5.) 9. How much has the 
 general surface of the large lava flows been worn down since their 
 eruption ? (Compare front border sections of SW. flow in 18 4 and 
 20 5.) 10. Compare the amount of erosion of volcano summits, gen- 
 eral upland surface, general lava-flow surface, and river valley F.] 
 
VOLCANOES AND LAVA FLOWS 73 
 
 11. 1. About how many feet has the (uppermost) SW. lava flow 
 in 20 5 been narrowed ? 2. Has it lost more on the W. or on the E. 
 side ? Why ? 3. Why has erosion been greater (more rapid) on the 
 W. side than on the general surface of the flow? 4. Name some 
 other parts of 20 5 where similar changes have taken place. 5. If 
 you ascended from river V, first to the upland on the W., then to 
 the lava flow on the E., what difference would you find in the rock 
 waste on the valley sides ? 6. Where would corresponding kinds 
 of rock waste be found in valley Z ? 7. How can the term talus 
 be used here ? 8. Why do the streams of two southwestern val- 
 leys of the great volcano unite before reaching river Z ? 9. Why 
 is the gorge of the united stream narrower than the valley of Z? 
 
 10. In what other part of 20 5 is a similar gorge shown? Why? 
 
 11. About how many feet has the valley on the N. side of the 
 smaller volcano been deepened ? 12. Why do the streams on the 
 N. and S. sides of this volcano unite before reaching river UV? 
 (Examine 184.) 13. Why are there no lakes in 20 5? 14. Draw 
 a line in 20 5 across valley UV from Q to Q'; across valley Z from 
 R to R'. [15. Draw sections in 15 13 corresponding to the profiles 
 QQ', RR', 20 5.] 16. Name, describe, explain, and indicate by appro- 
 priate letters the features shown in is 16 (scale, about 1 : 62,500), 
 which resemble certain features of 20 5. [17. Complete the contours 
 in the NE. part of 15 16.] 
 
 12. [1. A large volcano on Tahiti, one of the Society islands in the 
 S. Pacific ocean, has been so greatly dissected that it is now hardly 
 more than a skeleton of radiating ridges. (See Dana, Revised Text- 
 book of Geology, p. 130 ; or Manual of Geology, fourth edition, p. 180.) 
 2. The Cantal is a deeply dissected volcano in France ; it is esti- 
 mated to have lost about a mile of its original height. A road and 
 a railroad, following up one valley, tunneling through a ridge and 
 then following down another valley, pass almost through the center 
 of the volcano. 3. In what part of France is the Cantal ? (See Plate 
 43.) 4. Enormous lava flows form extensive plains in Idaho, Oregon, 
 and Washington. 5. What parts of each state does the lava cover ? 
 
74 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 (DE, Fig. 114 ; DP, Fig. 130.) 6. The level borders of the most 
 recent flows contour around the inclosing mountains, as the ocean 
 contours around the continents ; ridges stand forth in the lava 
 plain like promontories ; the lava plain enters valleys between the 
 promontories, forming " bays "; outlying mountains rise like islands 
 over the plain ; deep canyons, cut by Snake river and its branches, 
 disclose lower mountains buried under the heavy lava sheets. 
 (DE, 228.9 ; DP, 211.4 ; G, 213.8 ; T, 125.9 ; see also I. C. Rus- 
 sell, Water-supply paper, No. 4, U. 8. G. S., especially pp. 36, 38, 
 34 ; also, by same author, Bulls. 199, 217, 252, U. S. G. S. ; many 
 excellent plates ; also, by same a,uihor i Volcanoes of North America.') 
 1. Smaller lava flows form a plateau (the Mesa de Maya) in Colo- 
 rado. In what part of the state are these flows ? (See Plate 40.) 
 In what stage of dissection is this lava plateau ? (See 36 2 and 3.)] 
 13. 1. The variable succession of events in a volcanic district 
 may be illustrated as follows : Instead of passing from 18 4 to 20 5, 
 let 15 17 follow 18 4. 2. What appears to have happened to the great 
 volcano of 18 4 in 15 17 ? 3. The large cavity in the cone is called 
 a caldera; compare the caldera of 15 17 with the crater of the great 
 volcano in 18 4, as to diameter ; as to depth. [4. Can the caldera 
 have been formed, like a valley, by ordinary stream erosion? Ex- 
 plain. 5. Do the lava flows appear to be covered with the products 
 of an explosive eruption, or do they remain as they were in 18 4 ? 
 6. How can such a caldera be best explained ? (DE, 221.2; DP, 
 218.8; G, 217.6; T, 122.1.) 7. Compare 184, 1517, and 20 5 as to 
 opportunity of examining the internal structure of a volcano.] 8. If 
 eruptions begin again, a new cone and new flows may be formed, 
 burying earlier forms. Describe 15 18 as to the forms there shown ; 
 as to the succession of events there indicated. 9. If an outflow of 
 lava occurs after a cone of " ashes " has been built, a great cavity, or 
 breach, may be opened in the side of the cone ; if the cone is enlarged 
 by eruptions of ashes after the flows have ceased, the form of the 
 cone is more regular. 10. Compare the cones of 17 2, 18 3 and 4, and 
 15 18 in these respects. 11. Which of the lava flows in these figures 
 
VOLCANOES AND LAVA FLOWS 75 
 
 appears roughest ? [12. An extremely ragged lava flow breaches 
 the N. side of the cone of Jorullo. 13. " Crater lake " occupies a 
 great caldera in a broken-down volcano in Oregon, mapped in 38 2. 
 (DE, 222; DP, 215.9-; G, 217.6; T, 121.8. See J. S. Diller, Nat. 
 Geoff r. Mag., VIII (1897), 33-48.) 14. In what part of Oregon is 
 Crater lake ? (See Plate 40.) How far N. of Mt. Shasta ? 15. What 
 are the dimensions of this caldera ? How is its origin best ex- 
 plained ? 16. What reasons can you give for describing Vesuvius 
 (locate on Plate 43) as " a large cone built over the western rim of 
 a great caldera " ? (DE, 221.8 ; DP, 213.3 ; T, 117.3.) What is 
 the name of the E. rim of this caldera ? 17. If a breached caldera 
 stood in the ocean, describe the shape of the island that it would 
 form ? 18. Name and locate such an island. (DE, 221.5 ; DP, 
 213.2; in S. Shetland islands, Plate 42.) What is its diameter?] 
 
 14. 1. Why have some dissected volcanoes a central peak or neck, 
 as in 20 6 ? 2. Examine the side slopes of the spurs of this great 
 volcano, and note a difference of shading above and below a certain 
 level. Draw a [pencil] line along this level on several spur sides ; 
 the altitude of this line is about 3100'. 3. What is thus indicated as 
 to the depth now reached in the dissection of the volcano ? (Exam- 
 ine 17 1 and 18 3 as to altitude of the central uplands.) [4. How 
 much loss of altitude has taken place on the central summit of the 
 great volcano in the change from 20 5 to 20 6 (use the same trac- 
 ing paper as in 10)? on the even surface of the SE. upland ? on 
 the general surface of the SW. lava flow (away from streams)? on 
 the valley floor of river Z? of river V ? 5. Why has valley V not 
 been as much deepened by its large river as the volcano summit 
 has been lowered by weather and small streams?] [6. Why does 
 a row of sharp knobs occur on the SW. spur of the great volcano, 
 20 6 ? (See note following question 7, 8.) Where do similar knobs 
 occur ? Why? 7. Draw in 15 15 a section crossing the SW., SSW., 
 and S. spurs of the great dissected volcano of 20 6, and show the 
 features referred to in question 6. 8. Why has the middle spur a 
 different cross profile from the other two ?] 
 
76 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 15. 1. Why are the borders of the lava flows in 20 6 more irregu- 
 lar or " ragged " than 20 5 ? 2. Has the change of form occurred 
 chiefly on their upper surface or around their borders ? Why ? 
 3. Why are the borders marked by a vertical cliff above a steep, 
 talus-covered slope ? 4. How can the term retreat be used in con- 
 nection with the changes of the bordering cliffs ? 5. How can the 
 term sapping or undermining be used in connection with the retreat 
 of the cliffs ? 6. Which is the more resistant, the country rock of the 
 district or the lava of the flows ? 7. Why do the lava flows now 
 form table mountains? 8. Explain the relation of the several table 
 mountains of 20 6 to the valleys of 17 2 and to the lava flows of 
 184. 9. Where are the river gravels of the original valley UV, 
 17 1, now preserved ? 10. Suppose that the gravels contained grains 
 of gold, how could the gravels be best mined? [11. What is the 
 origin of the small knobs E. of valley V near the SW. corner of 
 20 6 ? 12. In 15 13 redraw sections QQ' and RR' so as to make them 
 correspond with 206 instead of with 20 5. (The proper depth of 
 valleys V and Z, 20 6, is indicated in 15 13 by dots below sections 
 QQ,' and RR'.) Draw in 15 16 the outline of the middle table 
 mountain when its length, NE.-SW., is reduced by half ; of the E. 
 table mountain when it is reduced to a butte.] 
 
 16. [1. Many volcanic knobs or necks occur near Mt. Taylor, a 
 deeply dissected volcano in New Mexico. (See article by Button, 
 6th Ann. Rep., U.S.G.S., p. 164.) Locate Mt. Taylor on Plate 40. 
 
 2. Is volcanic action in that district recent or ancient ? Why ? 
 
 3. A fine table mountain, called Raton mesa (pron. may-sa; Spanish 
 for "table"), surmounts the plains adjoining the Rocky mountains, 
 W. of Mesa de Maya in Colorado ; part of it is mapped in 38 3 ; 
 locate it on Plate 40. 4. What is the scale of 38 3 ? The contour 
 interval is 250'. The altitude of the mesa is 9250'; of the plains on 
 the north (beyond the map), 5500'. 5. Number the contour lines. By 
 how many feet have the plains been worn down since the lava flow 
 of the mesa was erupted ? 6. In the Sierra Nevada, California, gold 
 is found in gravel deposits under the lava cap of Table mountain ; 
 
VOLCANOES AND LAVA FLOWS 77 
 
 the narrow valleys on each side of Table mountain are much 
 lower than the gravel deposits. (See Placerville folio, U. S. G. S.) 
 
 1. Draw a cross section to illustrate these features. [8. In what 
 stage of the history of the Sierra Nevada (see Exercise V, 5) was 
 the lava flow of Table mountain erupted?] 9. A number of ex- 
 traordinary wall-like dike ridges occur near the lower slopes of the 
 greatly dissected volcano, Spanish peaks (about 100 mi. S. of Pikes 
 peak), Colorado; locate this volcano on Plate 40. 10. What do the 
 dike ridges indicate as to the stage of erosion of this volcano ? 
 (See Spanish peaks folio, U. S. G. )] 
 
 17. Now turn back to Plate 19. 1. Which lava flow of 18 4 has 
 been completely worn away in 19 7 ? What was its form in 20 6 ? 
 
 2. Compare the N W. (lava flow) table mountain in 20 6 and 19 7. 
 Has it changed chiefly in height or in area? Why? 3. By what 
 forms is the NE. table mountain of 20 6 represented in 19 7 ? 
 Explain the change. 4. In what part of the SW. table mountain 
 has a similar change occurred ? 5. How can the terms head- 
 ward erosion or retrogressive erosion be used in this connection ? 
 6. Why has the retreat of the lava cliffs by sapping been greater 
 than the deepening of the valleys by river erosion, in the change 
 from 20 6 to 19 7 ? 7. In a still later stage of erosion, which of the 
 volcanic features of 19 7 would disappear ? which would remain ? 
 Explain. [8. About how many square miles of surface are covered 
 with lava flows in 18 4 ? in 19 7 ? (Draw on the tracing paper, already 
 used and placed as before, a series of lines parallel to the S. base- 
 line, through the half-mile points on the W. baseline ; another series 
 parallel to the W. baseline, through the half-mile points on the S. 
 baseline. What is the area of each "diamond" thus marked? 
 Place the tracing paper on 184 and 197 and estimate the desired 
 areas.) 9. About what fraction of the original lava-flow areas 
 remains in 19 7 ?] 
 
 18. 1. In 198, what is the altitude of the central neck of the 
 great volcano ? 2. Estimate the altitude of the radiating ridges 
 in the E. center of the district, and compare their altitude with 
 
78 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 that of the corresponding part of the upland in 17 1. 3. How 
 completely has the great volcano been worn away ? What parts 
 of it remain ? Why might these parts be spoken of as the 
 " roots " ? 4. How many necks and dikes are shown ? To what 
 are they related in the earlier figures of this series ? Why are 
 they better shown in 19 8 than in 20 5 or 20 6 ? 5. What forms 
 are now seen Avhere the table mountains of 20 6 and 19 7 stood ? 
 Explain. 6. Why may 19 8 be described as a district of " lost vol- 
 canoes"? [7. Add a profile to 15 14 showing the three necks as they 
 appear in 19 8.] [8. Several large knobs or necks of volcanic rock 
 (lava) occur in the St. Lawrence valley ; one of them gives name 
 to the chief city of Canada. (DP, 217.1.) Volcanic necks are not 
 uncommon in S. Scotland. No " table mountains " occur in either 
 of these districts. 9. What supposition may be made as to the 
 amount of erosion that has taken place in those districts ?] 
 
 19. [1. Describe in a general way the changes commonly made 
 by volcanoes and lava flows in forming lakes ; in displacing rivers 
 to one side of their former courses ; in turning part of one river 
 across a divide to another river system. 2. What effect may vol- 
 canoes and lava flows have in shifting the point of junction of two 
 streams ? in replacing a single stream by two nearly parallel streams? 
 in originating groups of radiating streams ? 3. What is the length 
 of river UV in 17 1 and in 19 8 ? (Lay a thread or a narrow strip of 
 paper along the turns of the river and measure its length.) 4. Com- 
 pare the fall of UV (feet per mile) in 17 1 and 198, and explain 
 the difference. 5. Use tracing paper as before, and copy rivers UV, 
 Z, YY' from 17 1. 6. Lay the tracing paper on 19 8. Why is the 
 displacement of river UV in 198 least near the N. border of the 
 district ? Why has it been displaced westward ? About how far 
 has it been displaced in its middle course ? 7. Why does a stream 
 run W. across former mid-courSe of UV? Why do the next down- 
 stream branches of UV (on E. side) run away from the original 
 course of UV? 8. Why does the K part of river YY', 17 1, flow 
 to river U V in 19 8 ? Why is the original lower part of YY' now 
 
VOLCANOES AND LAVA FLOWS 79 
 
 represented by two streams ? 9. Why is river Z more crooked in 
 198 than in 17 1 ?] 
 
 20. [1. A line about 9" long is drawn on the side of Plate 19. 
 Let this line represent a very long period of time. (The line may be 
 imagined as extending indefinitely in each direction, thus represent- 
 ing earlier time without beginning, and later time without end.) 
 2. Turn the Atlas so that the line is horizontal. Mark small crosses 
 on the line at 0, , 1, and 3 inches from its left end ; number these 
 crosses 1 , 3, 4, 6, and let them represent the dates of 17 1, 18 3, 18 4, 
 and 20 6 in the series of volcanic figures here studied. 3. Indicate 
 by other crosses, properly placed and numbered, the dates of 17 2, 
 20 5, 19 7, and 19 8. 4. Print F, to show the estimated date of the 
 first volcanic eruption ; L, to show the last eruption. 5. How far 
 to the left of the first cross would you place a mark A, to indicate 
 the date of the general uplift of the region, as a result of which 
 the mature valleys of 17 1 were eroded ? (Note that the valley SE. 
 of the lava flows in 20 5 has a narrower floor than the corresponding 
 valley in 17 1.) 6. How far to the right of cross 8 would you place 
 another cross Z, to represent so late a stage in the cycle of erosion 
 that the hills of 19 8 shall have been worn down almost flat, that is, 
 to a peneplain ? (Erosion proceeds more and more slowly as hill 
 slopes are worn to less and less declivity.) 7. During what part of 
 the cycle AZ did the volcanic eruptions FL occur ? 8. Through (about) 
 what fraction of the cycle did the lava flows (table mountains) 
 endure ? 9. If the whole cycle were something like 10,000,000 or 
 30,000,000 years long, how many years were required for building 
 the volcanoes ? for wearing away the lava flows ? 10. Has the du- 
 ration of the cycle of erosion been lengthened or shortened by the 
 occurrence of volcanic action ? 11. Why may the volcanic phenomena 
 be referred to as " accidents in the normal cycle of erosion " ?] 
 
 21. Define : 2, volcano, crater, lava flow ; 3, volcanic lake, 
 gorge, pipe ; 4, volcanic cinders, ashes, and dust ; 6, volcanic 
 pipe and neck ; 8, dike, [malpais] ; 13, caldera, breached vol- 
 cano or cone ; 15, table mountain ; 16, mesa, dike ridge. 
 
EXERCISE VII. THE RIVER CYCLE : WATERFALLS, 
 RAPIDS, AND GRADED RIVERS 
 
 OBJECT. To study various problems in connection with the devel- 
 opment of rivers. 
 
 Preliminary. 21 1 is a block diagram of part of a lowland 
 crossed by a number of low E.-W. ridges and drained by two S.- 
 flowing rivers, R and Q. The lowland is so nearly level that much 
 of the rainfall sinks into the soil or dries off from the surface; 
 hence the number of branch streams is small. Each block is about 
 4 mi. wide. A scale of miles is marked along the W. baseline of 
 the block. The shore of the ocean is shown near the S. end of the 
 block. The dotted line on the W. block face indicates sea level ; 
 the short vertical lines rising from it show altitudes of 100'. (The 
 vertical scale is much exaggerated.) The following figures, 21 2, 22 3 
 and 4, etc., illustrate later stages in the history of the same district 
 as 21 1, as it is uplifted and dissected. This exercise uses 21, 22, 23, 
 
 24, 26, 1-12. 
 
 1. 1. What is (about) the altitude of the lowland at the N. end 
 of 21 1 ? What is the fall of river R per mile ? 2. About how high 
 are the ridges over the lowland ? 3. The lowland has a fine deep 
 soil ; the low ridges have a thin stony soil. What can you infer as 
 to the resistance of the rocks under the low ridges, as compared to 
 that of the rocks under the lowland? 4. In what stage of a cycle 
 of erosion does this district seem to be ? [5. Draw a IST.-S. pro- 
 file in 21 1 b across belts E, D, C, along the middle N.-S. line of 
 21 1. 6. Draw an E.-W. profile in 21 2 b along belt E.] 7. 21 2 
 shows a later stage in the history of the district. (Altitudes of 0', 
 200', 400', and 600' are shown by dotted lines, and the profile of 21 1 
 is drawn in a broken line on the W. block face of 21 2.) 8. Compare 
 
 80 
 
THE RIVER CYCLE 81 
 
 the altitudes of 21 1 and 21 2 in the NE. corner ; NW. corner ; at 
 W. and E. ends of belt L ; of belt H ; of belt E ; along the shore 
 line of 21 1. 9. Has the district been evenly or unevenly uplifted ? 
 10. Why do lakes S and T occur ? NOTE : It is not usual to find 
 lakes produced by uneven uplift or warping of the earth's crust, 
 because the basins thus formed are usually filled with inwashed 
 waste (as well as cut down at the point of river overflow) while 
 the warping goes on. 11. What may be inferred from this as to 
 the rate at which warping usually takes place ? [12. What other 
 illustration of the rate of crustal warping have you had in these 
 exercises ?] 
 
 2. 1. Where has the waste from the head waters of rivers R and 
 Q, 21 2, been deposited? 2. Why may lakes be regarded as "river 
 filters"? 3. Mark [blue] the shore line that lake T would have had 
 if the head streams of Q had not formed a delta in it. 4. About 
 how much has the outlet of lake T been cut down in ridge J? 
 5. Draw a broken [blue] line to show the shore line that you think 
 lake T would have had if its outlet had not been cut down by stream 
 Q in ridge ,/. 6. Why is the delta in lake S larger than the delta 
 in lake T ? 7. If -R had been a much larger river than it is, what 
 effect might it have had on the occurrence of a lake in basin S ? 
 [8. Compare the altitudes of the W. part of ridge J, lake S, and 
 the land between lakes S and T. 9. Where would the outlet 
 (overflow) of lake S be, if river R had not been able to cut a notch 
 in ridge / during the warping of the district ? 10. Compare the 
 direction of general land slope in 21 1 with the direction of land 
 slope from ridge / to lake S in 21 2. 11. Why was river R not 
 turned eastward to lake T while this local northward slope was 
 upwarped across its course ? 12. What name is given to rivers of 
 this class ? (Exercise V, 9.) 13. In what part of their courses 
 are rivers R and Q antecedent ?] 
 
 3. 1. Determine the average fall in 21 2 of river R from the 
 notch in ridge J (altitude, 400') to the sea, and compare it with the 
 average fall of .R in 21 1. 2. What effect has the increase of fall had 
 
82 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 on the behavior of the river ? 3. What term may be applied to rivers 
 whose activity is thus increased ? (Exercise V, 5.) 4. How many 
 waterfalls occur on R in 21 2 ? 5. Does the location of the four 
 larger falls on R confirm the inference already made ( 1, ques- 
 tion 3) as to the occurrence of resistant rocks under the low ridges 
 of 21 1 ? Explain. 6. How are the waterfalls related to the resist- 
 ant and weak rocks? (DE, 252.2; DP, 236.1; &, 38.8 ; T, 54.1.) 
 
 7. How may the six small falls on river R, 21 2 (marked by short 
 lines across the river), in the weaker rocks B, D, F, H, be accounted 
 for ? 8. In what parts of a district like 21 2 would you look to find 
 the attitude (horizontal, slanting upstream or downstream, vertical) 
 of the rock layers ? 9. What is the attitude of the rock layers in 
 22 3 c ? in 22 4 a? 10. To what parts of 21 2 might the larger-scale 
 22 3 c correspond ? [11. Draw a [red] line in 22 3 c, separating the 
 resistant strata from the weaker strata.] NOTE : The steep walls 
 of a river gorge show many rock outcrops from which the structure 
 of the district may be determined. 12. How is the structure of the 
 district here studied represented on the W. block-face of the figures 
 in this exercise ? 13. What is the general attitude of the groups 
 of strata, or formations, there represented ? 
 
 4. 1. What determines the depth to which the valley of river R, 
 21 2, has been eroded upstream from formation J? 2. Why may 
 the notch in each resistant formation be regarded as the local base- 
 level with respect to which the next upstream weaker formation is 
 worn down ? 3. Why is the valley of river R, 21 2, deeper in forma- 
 tion B than in formation A" ? 4. Why are the falls from formation 
 J higher than from formation G? 5. A river flowing through a 
 narrow gorge usually has certain parts of even flow (reaches'), cer- 
 tain parts of hurried, uneven flow (rapids), and certain parts of 
 steep or vertical plunge (falls'). 6. Mark in 22 3 c and 22 4 a a full 
 [blue] line on the reaches, a broken [blue] line on the rapids, and 
 a dotted [blue] line on the falls. 7. How are reaches, rapids, and 
 falls related to the occurrence of resistant and weak formations ? 
 
 8. How many reaches separated by how many falls occur on river 
 
THE RIVER CYCLE 83 
 
 R, 21 2 ? (The rapids in the notches are too small to be shown in 
 this figure ; they are indicated in 22 3 c.) [9. Draw in 21 1 c a N.-S. 
 profile across belts E, D, f, as they are seen on the W. border of 
 21 2 ; and in 21 1 d, a profile across the same belts along river R, 21 2. 
 
 10. Indicate the underground structure beneath these profiles. 
 
 11. Draw in 21 2 c an E.-W. profile along belt E, 21 2 ; and in 21 2d, 
 an E.-W. profile along belt />; add lines to the last profile to 
 represent the side streams in belt />.] 
 
 5. NOTK : 22 3 shows a greater amount of up-warping than 21 2. 
 (The profiles of 21 1 and 21 2 are marked in broken lines on the W. 
 block-face of 223.) 1. About how much uplift has occurred from 
 21 2 to 22 3 in the 1ST. part of the district ? in the center ? in the 
 southern part ? 2. What has happened in 22 3 to lakes S and T of 
 21 2 ? 3. Describe the course of river R as to reaches, rapids, and 
 falls in 22 3. 4. Where has a new fall been formed ? Why ? 
 
 5. Where have some small falls been destroyed ? How and why ? 
 
 6. How are the reaches, formerly separated by the small falls, now 
 related ? 7. Compare the height of the falls from C and E (the 
 C and E falls) in 21 2 and 22 3. 8. Why have the falls decreased 
 in height at one place, and increased at the other ? [9. Answer 
 similar questions for the G and J falls.] 10. Why is the valley of 
 /.' deeper in formation B than in formation M? in D than in F ? 
 in // than in F ? 11. Why is the valley of Q in general less deep 
 than the valley of R ? [12. Draw E.-W. profiles in 22 3 ab on belts 
 ./ and //, 22 3.] 
 
 6. 1. Compare the altitudes of E, J, and L on the W. profile of 22 3 
 and 22 4. 2. Has 22 4 been uplifted as compared with 22 3 ? 3. What 
 general change has taken place in the depth of the R and Q valleys ? 
 in their width ? 4. Has the number of falls on R changed ? Ex- 
 plain. 5. Has the number of reaches changed ? Explain. 6. The 
 uppermost line of 26 9 shows the profile of the W. border of the up- 
 land of 22 3. (The vertical scale is here exaggerated over the hori- 
 zontal about 16 times.) The line in 269 marked 3, 3, 3 shows 
 part of the profile of river R for 22 3. 7. Complete the profile in 
 
84 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 formations D and B. 8. Several short lines marked 4 indicate parts 
 of the profile of R in 22 4. Complete this profile. 9. Compare 
 the number of falls and reaches in 22 4 (or profile 4) and in 21 2. 
 10. What change has taken place in the number of falls ? in the 
 number and length of the reaches ? Explain. 11. What would 
 you expect as to the number and length of separate reaches at 
 an earlier stage of gorge erosion than 21 2 ? at a later stage than 
 22 4 ? Explain. 12. On what sort of strata are the falls earliest 
 worn down ? latest worn down ? 13. On what sort of strata are 
 uninterrupted reaches soonest developed ? 14. How may the term 
 grade be used in this connection? (See Exercise III, 4 ; DE, 254.4; 
 DP, 237.5 ; T, 5G.8.) [NOTE : Several streams in NE. Pennsylvania 
 flow across an inclined series of strong and weak formations. 
 Waterfalls occur where the streams pass from the strong to the 
 weak formations. 15. Which figure in Plate 22 gives best illus- 
 tration of these falls? 16. Explain their origin. 17. Where do 
 graded reaches probably occur on these streams ?] 
 
 7. 1. Draw in 26 9, through the lines marked 5, the profile of R 
 for 23 5. 2. Which falls are now almost reduced to rapids ? Why ? 
 3. Draw profile 6 in 26 9. 4. Why have the E falls decreased in 
 height ? 5. Why are the C and G rapids almost obliterated ? 
 
 6. Compare the amount of erosion on C and L between profiles 5 
 and 6. Which has been eroded by the greater amount ? Why ? 
 
 7. Why have the C falls been decreased and the L falls been in- 
 creased in height during this interval ? 8. Draw profiles 7 and 8 
 in 26 9. 9. Compare profiles 3 and 8 as to number of falls ; height 
 of falls; number and length of reaches. 10. Why are the /rapids 
 longer but less steep in profile 8 than in profile 3 ? [11. Examine 
 the upper profile of 24 8 a. Are the resistant formations odd-num- 
 bered or even-numbered ? 12. Complete the river profiles m, m 
 and n, n. 13. Draw some additional river profiles. 14. Which fall- 
 making formations will have been worn downward (nearly verti- 
 cally) when their falls are extinguished (or obliterated) ? Which 
 will have been worn backward (upstream nearly horizontally) ? 
 
THE RIVER CYCLE 85 
 
 Why ? 15. Examine the river profiles in 24 7 a, b, c. What is the 
 attitude of the strata in each figure ? 16. Print F on each fall- 
 making formation. 17. Let the lower broken line in each figure 
 represent the profile that the river will have when it is graded 
 across the fall maker (as in profile 8, of 269); prolong this graded 
 profile upstream. 18. In which figure must the fall maker be 
 eroded by the greatest amount before the fall is obliterated ? 
 by the least amount ? Why ?] [19. Several rivers flowing E. 
 from the highlands of the Transvaal, S. Africa (locate on Plate 45), 
 have worn deep valleys across inclined strata (slanting W.). To 
 what ocean do these rivers flow ? Elands river, in the S. part of 
 Portuguese East Africa, still has two falls where it crosses the 
 most resistant formations of its course. With which falls in 235 
 do these two falls correspond ? 20. The Potomac river has eroded 
 a deep, narrow notch in the inclined, resistant strata of the Blue 
 ridge at Harpers Ferry ; there the river flows in shallow rapids 
 across the edges of the rock layers. Locate Harpers Ferry in rela- 
 tion to the neighboring states. (See Plate 40.) What effect have 
 the rapids on the navigation of the Potomac? 21. On what for- 
 mation are similar rapids shown in 24 7 ?] 
 
 8. [1. Compare the position of the falls on formations C and L 
 in profiles 3, 5, and 8 of 26 9, as to distance from river mouth. (Meas- 
 ure the distances on the scale of miles at base of 26 9 ; the forward 
 growth of R delta in the sea may be neglected in this connection.) 
 2. Why are the falls or rapids on these formations farther from 
 the river mouth in profile 5 than in profile 3 ? 3. Why has the 
 increase of distance from river mouth in the L falls been greater 
 than in the C falls ? 4. Why may the L falls be described as 
 having been worn back, or as having retreated, while those from 
 C have been mostly worn down ? 5. How far have the L falls re- 
 treated between profiles 6 and 8 ?] [6. Compare the slope of the 
 graded reaches in profiles 3 and 8 of 26 9. Explain the difference. 
 (Consider in this connection the amount of waste received by the 
 river from its valley sides and its side streams in these two stages. 
 
86 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 Examine 22 3 and 24 8.) 7. If the N. extension of formation L 
 be horizontal, how far must its waterfall retreat before it is obliter- 
 ated or extinguished (the grade of the river remaining as in profile 
 8 of 26 9)? 8. Suppose that, during the retreat of the L falls, the 
 rapids on J are worn down lower than profile 8 ; what effect will 
 this have on the retreat needed for the obliteration of the L falls ? 
 9. Suppose that, during the retreat of the L falls and the re- 
 duction of the ./ rapids, the slope of the graded reaches in river 
 R is lessened (because the load to be carried is lessened) ; what 
 effect will this have on the amount of retreat of the L falls before 
 they are obliterated ? 10. Which are longer lasting, falls from 
 vertical, from inclined, or from horizontal strata of the same 
 resistance ?] 
 
 9. [1. Assume the amount of water that is discharged by river 
 R to be the same in all the chief figures of this exercise. Does the 
 river flow faster in 21 1 or 22 3 ? 2. Then in which figure, 21 1 or 
 22 3, should the river be broader ? (If a slow-flowing and a fast- 
 flowing river discharge the same amount of water, the fast-flowing 
 river will be narrower than the other. Explain.) 3. In what part 
 of the river in 22 3 would you expect it to be narrowest ? broadest ? 
 (See 21 2 a, 22 3 c, and 22 4 a.) Why ? 4. In what part deepest ? 
 shallowest? (The plunge of a large river from high falls scours 
 out a deep pool in the weak strata below the falls ; the rush of 
 flood waters wears the weak strata of graded reaches somewhat 
 deeper than the hard strata of rapids.) 5. If river R should cease 
 running in a dry season, where would pools remain in its channel ? 
 6. What sort of a lake is shown near the S. part of river R in 
 24 8 ? Compare it as to origin, size, and stage of river develop- 
 ment with the two lakes of 21 2. 7. In which of the chief figures 
 of the exercise would river R be most easily followed by boats or 
 rafts ? 8. If an Indian came down river .R of 23 5 in a canoe, how 
 many " carries " would he have to make ? (A carry or portage 
 must be made where the falls or rapids are so steep that the canoe 
 has to be carried along the river bank.)] 
 
THE RIVER CYCLE 87 
 
 10. 1. The occurrence of many falls and rapids in the course 
 of a river indicate that it is in an early stage of development ; the 
 river is then young. As the falls and rapids are obliterated and 
 the separate reaches unite in a long-continuous graded course, the 
 river is mature. When the valley floor has been widened and the 
 graded course worn down to a very gentle slope, the river is old. 
 2. In which of the chief figures of this exercise is river R young ? 
 in which one is it mature ? old ? [3. Other indications of the stage 
 of development of a river are to be found in its velocity, in the quan- 
 tity and texture of its load, in the breadth of its flood plain, etc. 
 4. State some of these indications.] 5. Through what changes do 
 you think R had passed before it reached the condition shown in 
 21 1 ? [6. Let the chief figures of this exercise illustrate a " cycle of 
 river development," in which the stages of 21 1, 22 3, 23 6, and 24 8 
 are indicated by corresponding numbers over the time line of 26 10. 
 
 7. Add other numbers to show the stages of 21 2, 22 4, 23 5, and 24 7. 
 
 8. Print PERIOD OF UPLIFT under the proper part of the time 
 line. 9. With what stage of river development is the period of 
 uplift associated ? Why ? 10. Are the processes of erosion more 
 active on the steep slopes of youth or on the faint slopes of old 
 age ? 11. In view of this, about how far to the right of stage 8 in 
 26 10 should a ninth stage, with slopes and relief as small as in 
 21 1, be placed ? 12. Which is of longer duration, youth, maturity, 
 or old age of a river ? 13. What stage of river development had 
 been reached in the cycle during which 21 1 was developed, when it 
 was interrupted by the warping uplift which introduced the cycle 
 here studied ?] 
 
 11. Define : 3, formation ; 4, local baselevel, reach, rapids, 
 falls ; 6, grade ; 8, retreating waterfalls, worn-down waterfalls, 
 obliterated waterfalls ; [ 9, portage or carry ;] 10, cycle of river 
 development, youth, maturity, and old age of a river. 
 
EXEECISE VIII. THE EIVEE CYCLE: EIDGES, 
 VALLEYS, AND EIVER CAPTUEES 
 
 OBJECT. To study the origin of longitudinal ridges and valleys, and 
 the rearrangement of river courses associated with these features. 
 
 Preliminary. The figures used in the previous exercise serve for 
 this exercise also. 
 
 1. 1. In 21 2, why are the notches cut by rivers R and Q in the 
 harder formations C, E, etc., V-shaped, instead of having vertical 
 walls ? 2. Draw a [red] line along the top of the valley sides of 
 rivers R and Q in formations E, F, and G. (Neglect the E. and 
 W. side ravines for the present.) [3. 21 1 a is a contour map of 
 belts E, F, G; complete the contours W. of river R. 4. 21 2 a is a 
 hachure map of belts C, D, E ; complete the hachures W. of river 
 R. Mark a [red] line in 21 2 a along the top of the valley sides of 
 valleys R and Q.] 5. In which belts is valley R wider (at level of 
 upland) ? In which belts is it narrower ? 6. Why does its width 
 vary ? 7. Make a general rule, stating the relation between the 
 width of a young valley and the resistance of the formations in 
 which it is eroded. 8. By how many instances is this rule sup- 
 ported in 21 2 ? 9. If the valley of river R is wider in formation F 
 than in formation E, why is it not also eroded to a lower level in 
 F than in E ? 10. Examine the R valley in 22 3 and 4 with regard 
 to the relation between rock resistance and valley form, and then 
 complete the following statement : The width of a young valley 
 that is eroded across a weak formation is independent of, and is 
 usually greater than, the width of the valley notches eroded in 
 neighboring strong formations ; but the depth to which a young 
 valley can be eroded across a weak formation . . . 11. What 
 effect has the revival of R and Q had on their branch streams ? 
 
 88 
 
THE RIVER CYCLE 89 
 
 12. Do the branches join the main rivers in accordant or in hang- 
 ing fashion ? Why ? 
 
 2. 1. In 22 3 draw a light [red] line along the divide between the 
 drainage areas of rivers R and Q. Why may the divide be called 
 ill defined? 2. Compare the cross (E.-W.) profiles of R valley in 
 formation J, 21 2 and 22 3. [Complete the profiles in 21 2 c and 22 3 a.] 
 Do the same for R valley in formation H. [Complete the profiles 
 in 21 2 d and 23 3 b.~\ Explain the changes. 3. Complete in 22 4 b the 
 E.-W. profiles on formations // and J, 22 4. (See J 4 and 7/ 4 .) 4. How 
 have they changed from the corresponding profiles for 22 3 (J 3 and 
 H s in 22 4 i) ? 5. In 22 4, how many side streams join river R from 
 the east in formation //? How many join river Q from the east in 
 formation A'? 6. Draw a light [red] line along the divide between 
 the drainage areas of rivers R and Q in 22 4 ; make the line heavier 
 on the well-defined parts of the divide than on the rest. 7. Why 
 are some parts of the divide better defined than others ? 8. Why 
 are the head-water ravines of river Q longer in 22 3 than in 21 2 ? 
 (Use the terms head-ward erosion or retrogressive erosion in answering 
 the preceding question.) 9. Why does (most of) the divide between 
 the two head branches of river Q follow a sharp-crested, notched 
 (serrate) ridge, while the divide between rivers Q and R on forma- 
 tion M lies on a smooth-sloping upland ? 
 
 3. 1. Draw in 23 5 a [red] line along the divide between rivers 
 R and Q. 2. What parts of the divide are still ill defined ? Why ? 
 3. 23 5 b shows (on a somewhat larger scale) unfinished E.-W. pro- 
 files across the divide on formation H for several stages of this 
 exercise. Complete the profile for stage 5. Is the divide definite or 
 indefinite ? 4. Which part (E. or W.) of formation H was most up- 
 lifted in 22 3 ? 5. Then why is river R at a lower level than river Q 
 in stage 5, 23 5 b ? 6. Why is the divide not halfway between R and 
 Q ? 7. At a stage of erosion between the stages of 23 5 and 23 6 the 
 channels of rivers R and Q in formation H are shown on line 5-6 in 
 23 5 b. Why has jR deepened its valley more than Q ? 8. Complete 
 the E.-W. profile for the stage between stages 5 and 6. 9. How has 
 
90 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 the divide (in 23 5 b) between R and Q been changed as to form ? as 
 to altitude ? 10. How has it been shifted with respect to R and Q ? 
 11. Which river (R or Q} is gaining and which is losing drainage 
 area in formation //? Why? 12. Which side streams (of R or 
 of Q) are most effective in shifting (by headward erosion) the posi- 
 tion of the divide ? 13. What advantage have these side streams, 
 that makes them more effective ? 14. How does the length of the 
 side streams change as the divide shifts or migrates? 15. Fill in 
 the blanks in the following statement : When a smooth lowland 
 is uplifted the ..... divides between the rivers are gradu- 
 ally made by the erosion of the side streams ; and 
 
 then as the divides are slowly they are also slowly 
 
 toward the rivers ; and thus the rivers slowly 
 
 gain a larger drainage area. 16. Mark a [blue] 2^ 1IS sign (+) in 
 23 5 at several points where river R has recently gained drainage 
 area by the shifting of the R-Q divide ; and a [red] minus sign ( ) 
 at points where Q is losing drainage area. 
 
 4. 1. With what part of 235 does the enlarged sketch in 26 11 
 correspond ? 2. What river receives the drainage from surfaces 
 b, b, 2611? from surfaces a, a? 3. Draw a [red] line in 2611 
 along the divide between the side branches of Q and R (R is not 
 shown). 4. What is the general altitude of the foreground low- 
 land (a) on formation H ? of the same formation near river Q ? 
 5. What has caused this difference in altitude ? 6. What effect will 
 continued erosion have on the length of streams h l and h 2 ? on the 
 position of the R-Q divide ? 7. Draw a broken [red] line to show 
 the R-Q divide at a somewhat later stage (when its distance from 
 river Q is halved). 8. Draw in 23 55 an E.-W. profile for the same 
 later stage (between stages 5-6 and 6). 9. If changes of this kind 
 go on, what will happen to river Q ? 10. Draw a [blue] line in 
 26 11 to show what you expect. 11. Illustrate the same change by 
 drawing a new profile in 23 5 b. 12. Why may the expected change 
 be described as river capture or river diversion ? NOTE : As the 
 divide is shifted close to river Q, more and more of its water 
 
THE RIVER CYCLE 91 
 
 will pass underground and enlarge the springs that feed the head 
 waters of streams h 1 , 2611. 13. When the expected change has 
 happened, which river may be called captured or diverted? Which 
 stream may be called the di verier? 14. Why may the lower part 
 of river Q then be described as beheaded? (See Q', 26 12.) 15. How 
 Avill the volume of the beheaded river be affected ? 16. To what 
 river will the upper part of river Q (see Q", 26 12) then flow ? 
 
 5. 1. Draw a [red] line in 26 12 and 23 6 along the divide between 
 rivers R and Q'. 2. In what important respect has the divide been 
 changed from the divide in 2611 and 23 5? 3. Has the greatest 
 part of this change taken place slowly or (relatively) rapidly? 
 4. If the shifting or migration of the divide between stages 4, 5, 
 and 5-6, in 2:5 5 b, be described as creeping, what part of the shift- 
 ing may be described as leaping ? 5. Why may the point where the 
 capture was made be called- the elbow of capture ? 6. Print W at 
 this point in 26 12. 7. Why lias river Q"-h l deepened its valley 
 downstream from the elbow of capture ? and also upstream from 
 the elbow ? 8. Why is the valley of Q" in formation K not 
 deepened in 26 12 ? 9. Which waterfall is higher as a result of 
 this river capture ? 10. What has happened in 26 12 (since the 
 leaping of the divide around the upper part of river Q) as to 
 erosion along stream 7/ 2 ? along streams h 3 and h* ? 11. Explain 
 these happenings. 12. What changes may be expected to take 
 place (in the not distant future) in stream h 5 ? in stream h 6 ? 
 13. What part of these last changes is made by creeping ? by leap- 
 ing ? What is the relative importance of creeping and leaping in 
 these changes of the divide ? 14. W T hat change will take place 
 at the same time in the volume of the G waterfall of stream Q' ? 
 in the volume of h 1 ? 15. Draw in 26 12 broken [blue] lines to 
 show the future courses of streams h 5 and 7i 6 ; a broken [red] line 
 to show the divide between Q"-h l and Q', when these changes have 
 gone on as far as they can. 16. 23 5 a shows on a larger scale a 
 part of river Q, on formation F of 23 5. Compare the size of the 
 stream curves with the size of the valley curves. How have the 
 
92 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 valley curves been produced ? 17. 23 6 b shows the same district 
 for 23 6. Compare the valley curves in 23 5 a and 6 b ; the stream 
 curves. 18. Explain the ' changes. 19. Why may the stream of 
 23 6 b be described as a misfit for its valley ? 
 
 6. 1. At what other points in 23 6 may stream captures take 
 place in the future ? 2. How many captures (besides the one 
 shown in 23 6) have taken place during the development of 24 7 ? 
 
 3. Print W at all the "elbows of capture " that you can find in 24 7. 
 
 4. Print X at points of capture where " no elbow " was made (as 
 will be the case with streams h 5 and h 6 , 2612). 5. Draw a [red] 
 line in 247 along the divide between the drainage areas of rivers 
 R and Q'. 6. What other capture may be predicted ? 7. Draw a 
 broken [red] line along the divide between R and Q', 24 8. 8. What 
 other capture may still be expected ? 9. Draw a full [red] line 
 along the R-Q' divide after this capture has happened. 10. Com- 
 pare in 22 3 and 24 8 the drainage area of river R ; the length of 
 the eastern branches of river R ; the number of notches in which 
 streams run through hard-rock ridges. 11. Explain (briefly) the 
 changes. NOTE : When a stream runs through a notch or " gap " 
 in a ridge, the notch may be called a water gap ; when no stream 
 runs through the notch, it may be called a u-ind gap. 12. Print T 
 at the water gaps and N at the wind gaps in 24 7. 13. What 
 is the origin of the chief wind gaps ? 14. Compare in 22 4 and 
 248 the sharpness of the divides (or "subdivides") between the 
 branch streams ; for example, the subdivides of the E. branches of 
 R on formations A and B. 15. In view of this comparison, what 
 additional statement regarding divides may be made, following 
 that of 3, question 15 ? NOTE : In 21 1 the drainage (by rivers 
 R and Q) is chiefly transverse (at right angles to the general trend 
 of the ridges); in 24 8 there is only one long transverse river, and 
 the rest of the streams are for the most part longitudinal (parallel 
 to the trend of the ridges). 16. Explain (briefly) how the change 
 from transverse to longitudinal drainage has been brought about. 
 17. Of the two originally transverse rivers, R and Q, 21 1, why 
 
THE RIVER CYCLE 93 
 
 has R survived ? [18. A stream which increases in length by 
 headward erosion along a belt of weak strata may be classed as 
 subsequent. 19. Mark S by several subsequent streams in 24 7 or 
 24 8. 20. Why do no longitudinal streams run along the resistant 
 formations ?] [21. The Allegheny mountains of Pennsylvania 
 and Virginia offer many examples of longitudinal and transverse 
 drainage, similar to that of 23 6, 24 7, and 24 8. 22. Locate 38 1 on 
 Plate 40. What river is there shown ? Is its course longitudinal 
 or transverse ? 23. How many longitudinal streams are shown ? 
 To what class do they belong? 24. The lowest contour line is 
 400' ; the contour interval is 100'. Print altitude numbers on the 
 contour lines, beginning at the middle of the S. border and passing 
 N. to the N. border. 25. How deep are the valleys below the 
 ridge crests ?] 
 
 7. 1. Compare the hard-rock ridges in 21 1 and 23 5 as to altitude ; 
 as to relief. 2. What has caused the change in altitude ? in relief ? 
 3. Which change has made the other change possible ? [4. Draw 
 a K. S. profile across belts C to G of 24 8 in 23 6 c ; draw the same 
 profile at a still later stage of erosion.] 5. Compare the ridges 
 of 23 5 -and 248 as to altitude; as to relief. 6. What has caused 
 the change in altitude? in relief? [7. In 23 6 a the uppermost 
 profile shows the form of ridges E and C, and of the intermediate 
 valley D for 23 5, about a mile E. of river R ; complete the profiles 
 for 23 6 and 24 7. 8. Draw earlier profiles for stages 21 2, 22 3 and 4.] 
 9. Explain (briefly) how the wider parts (on the weaker forma- 
 tions) of the transverse valley R in 21 2 and 22 3 have grown into 
 longitudinal valleys in 23 6, 24 7 and 8. 10. How is the altitude of 
 a longitudinal valley floor related to the altitude of the next 
 downstream water gap in the inclosing longitudinal ridge ? Ex- 
 plain. 11. How are the altitudes of several neighboring longitud- 
 inal valley floors of the same river system (as D, F, H, K, 247) 
 related to each other ? Explain. 12. Is there a corresponding rela- 
 tion in the altitudes of the several longitudinal ridges (as E, G, J, 
 24 7) between the longitudinal valleys ? Explain. [13. Complete 
 
94 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 ridge-and-valley profile k, 24 8 a. Draw an earlier ridge-and-valley 
 profile corresponding to stream profile n ; draw a later profile.] 
 
 8. [1. 38 1 shows several longitudinal ridges and valleys. In 
 what part of what state are they ? To what mountains do they be- 
 long ? 2. How high are the ridges ? (See 6, question 25.) 3. Are 
 the ridge crests even or serrate (sawlike) ? 4. How many belts of 
 strong and weak strata are here included ? 5. What is the origin 
 of the notches in the ridges ? 6. What is the origin of the longi- 
 tudinal valleys ? 7. Which figure of this exercise, Plates 21-24, most 
 nearly exhibits the features of 38 1 ? 8. What general explanation 
 can you give for the ridges, valleys, and notches of the Allegheny 
 mountains ? 9. A fertile longitudinal valley in Virginia (Shen- 
 andoah valley) lies next ISTW. of the Blue ridge, and is drained 
 through the transverse notch or gap eroded by the Potomac river 
 in the Bine ridge: Explain the origin of the longitudinal valley in 
 relation to the Blue ridge and the Potomac gap.] 
 
 9. [1. What is the attitude (vertical, steep slanting, gently slant- 
 ing) of the ridge-making formation in 247 d? in 7 e ? in 7 f? 
 2. Draw in these figures a [red] profile for each ridge after its 
 height is reduced by half (the level of the neighboring longitudinal 
 valleys remaining little changed). 3. In which figure has the ridge 
 crest changed its position (to right or left) by the greatest distance ? 
 by the least distance ? Why ? 4. Draw a broken [red] line along 
 the ridge crests C, G, L in 23 5 and 6, 24 7 and 8. 5. Why may 
 these lines be called longitudinal divides (or subdivides) ? 6. Why 
 do the more important longitudinal divides follow the strong for- 
 mations ? 7. Draw vertical lines in the same figures from the W. 
 end of the C, G, and L ridge crests (or longitudinal divides) to the 
 sea-level line (see 235, ridges Oand (7); mark off on a strip of 
 paper the distance from the SE. corner of the block to these verti- 
 cal lines. 8. As the divides are lowered, in which direction has 
 their position been shifted ? Why ? 9. Which one has changed 
 most ? Why ? 10. Make a general rule, showing how the shift of 
 a wasting ridge crest is related in direction and amount to the 
 
THE RIVER CYCLE 95 
 
 attitude of the ridge-making formation. 11. Compare the cause of 
 this kind of migrating divide with that of the kind described in 
 3 and 4.] 
 
 10. [1. In the cycle of erosion of a district made of inclined 
 formations, resistant and weak, which of the formations will be 
 soonest worn down to an " old " appearance (small relief, little 
 above sea level) ? 2. How much may the resistant formations be 
 worn down after the surface form of the weak formations is "old " ? 
 3. What will the surface form of the weak formations be, when 
 the resistant formations are worn down to small relief ? 4. In the 
 early stages of a cycle of erosion, which are worn down the faster, 
 the weak formations or the main river channels ? Explain. Illus- 
 trate by one of the figures of this exercise. 5. In the early stages 
 of a cycle, which formations axe worn down faster, the resistant or 
 the weak ? Illustrate, as above. 6. In the late stages of a cycle, 
 which formations are worn down the faster ? Explain. Illustrate, 
 as above. 7. In the late stages of a cycle, which are worn down 
 faster, the resistant formations or the river channels ? Explain. 
 Illustrate, as above. 8. If you should find a lowland of tilted or 
 disordered strata (like 21 1), in what stage of a cycle of erosion 
 would you suppose it to be ? 9. If you found a rather even high- 
 land (of disordered structure) trenched by narrow, steep-sided 
 valleys, what stages of two cycles of erosion would be there 
 represented? 10. What movement of the earth's crust would be 
 supposed to have taken place after the even surface of the region 
 had been produced ? Explain.] 
 
 11. Define : 3, shift or migration of a divide ; 4, river cap- 
 ture, river diversion, captured river, diverted river, diverter, be- 
 headed river ; 5, creeping divide, leaping divide, elbow of capture, 
 misfit stream ; 6, water gap, wind gap, subsequent stream ; 7, 
 transverse valley, longitudinal valley ; [ 9, longitudinal divide]. 
 
EXERCISE IX. SHORE LINES 
 
 OBJECT. To study the headlands, cliffs, bays, and other features of a 
 hilly or mountainous coast. 
 
 Preliminary. The series of eight maps in this exercise, on 
 Plates 27-29, are all on the scale of 1 : 80,000. The first map, 27 1, 
 shows a district of low mountains and hills, bordering the sea, in 
 part shaded with hachures, in part drawn with contours (50' in- 
 terval). The small crosses ( x x ) in the water area represent low 
 rocky ledges or reefs. Depth of water (in feet) is indicated at sev- 
 eral points. (The broken lines in the water area will be explained 
 later.) In the E. part of the map the rocks are resistant and the 
 mountains are late mature or subdued ; in the N. part the rocks 
 are weaker, and early old age is indicated by the low rounded 
 hills and open lowlands. The later maps, drawn in the same style, 
 illustrate changes due to the work of shore waves and currents, 
 and to movements of elevation and depression. This exercise uses 
 
 Plates 25, 27, 28, 29, 39. 
 
 1. 1. Suppose the land in 27 1 to sink, or the sea to rise, nearly 
 100' ; draw a [blue] line in the contoured area, to show the new 
 shore line thus produced. 2. What effect has the change of level 
 on bays A and B as to size ? as to general shape ? on the length 
 of the streams entering the bays ? on the contoured island as to 
 size ? 3. How many headlands or peninsulas are converted into 
 islands ? Why ? 4. Why are three hills, between bays A and B, 
 converted into small low islands ? 5. Where are new peninsulas 
 formed, each connected with the mainland by a narrow isthmus ? 
 6. Why is each isthmus narrower than its peninsula ? 7. If the 
 land had been submerged 150', why would each of these penin- 
 sulas have become an island? each isthmus a strait (or narrow 
 
SHORE LINES 97 
 
 water passage) ? [8. Add contours and hachures to some of the 
 unshaded hills and valleys in 27 1. 9. The scale being 1 : 80,000, 
 construct a linear scale 5 mi. long in the lower part of 27 1.] 
 
 2. 1. Suppose the land in 27 1 to rise, or the sea to sink, about 
 70' ; mark in the SE. part of the map a dotted [blue] line to show 
 (as well as you can) the new shore line. (This new line may be 
 drawn about A" from the present shore line.) 2. What effect is 
 thus produced on the length of the headlands ? of the bays ? of 
 the streams ? on the breadth of the isthmus between bays C and 
 D ? 3. Why are two islands converted into peninsulas ? two 
 straits into isthmuses ? some rocky reefs added to the mainland ? 
 4. Suppose the land in 27 1 once to have stood 200' higher (or the 
 sea 200' lower) than now ; only a small space in the SW. corner of 
 the map would then have been under the sea. 5. Draw in broken 
 [blue] lines (see the broken guide-lines in 27 1) the extended rivers 
 along the troughs of the bays. 6. Which river, A, B, C, or D, was 
 largest ? [7. Draw (roughly) the 50', 100', and 150' contours for 
 the valley of river AB.~\ 8. In view of all this, explain the origin 
 of the shore line, as it is drawn in 27 1. [9. State the stage 
 young, mature, or old reached in the cycle of erosion before the 
 change of level which produced the present shore line; the nature 
 of the change of level (rising or sinking of land). 10. Estimate 
 the amount of the change.] 
 
 3. 1. In the change of level by which the shore line of 27 1 was 
 produced, what preexistent forms have been changed into large 
 bays ? into small bays (or coves) ? wide bays ? narrow bays ? 
 headlands ? peninsulas ? isthmuses ? straits ? islands ? rocky 
 reefs? 2. Why was river C more shortened than rivers A, B, 
 or D? 3. Why may the various rivers and streams as drawn in 
 27 1 be described as dismembered by submergence ? 4. Why may such 
 a coast be classed as embayed ? 5. Why may such a district be 
 described as partly drowned? 6. Why do the dismembered streams 
 all flow into bay heads ? 7. Draw a [red] line along the divide 
 between bays C and D; between bays A and B. Why do these 
 
98 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 divides run to headlands ? 8. Why are some headlands round 
 (as on NW. side of bay C) ? and some sharp (either side of bay D) ? 
 
 4. 1. During the slow submergence (hundreds of thousands of 
 years) by which a coastal district is more or less drowned and an 
 embayed shore line is produced, the shore waves attack the sinking 
 land, sweeping away the previously weathered soil and loosened 
 rock. 2. When the submergence has ceased, the attack of the waves 
 continues at the level then reached. 3. The attack is especially 
 strong on the more exposed parts of the coast. Why ? 4. What new 
 features will be thus carved ? (DE, 310.7 ; DP, 360.7 ; G, 309.9 ; 
 T, 211.3.) 5. Draw a [red] line in 27 1 close along the shore where 
 small features of this kind have already been produced. (See the 
 darker, ragged parts of the shore line.) 6. What features will in 
 time be produced by the streams at the bay heads ? [7. Has the 
 land stood in its present position as long as it stood in its former 
 position (before submergence) ? Explain.] [8. In what part of 
 what state is the coast shown in 39 1 ? To what class does this 
 coast belong ? What is its origin ? 9. Mark a [red] line across 
 three isthmuses. 10. The rocks of this district are in great dis- 
 order. In what stage of erosion was the district just before sub- 
 mergence took place ? 11. Why are some of the bays called 
 harbors ? Which strait is called a river ? Which upper bay is 
 called a river ? 12. Draw a [blue] line through each of three 
 straits. What would these lines have represented before the sub- 
 mergence of the region ? 13. If the submergence had been almost 
 100' greater, into how many islands would South port (island) have 
 been divided ? Draw its shore line [blue] in that condition. 
 14. Draw [in blue] as well as you can the stream system of Booth- 
 bay harbor before submergence.] 
 
 5. 1. 25 1 is a block diagram (larger scale and more detailed 
 than 27 1) showing a low sea cliff BE, and a rock bench EC, cut by 
 strong waves on a sloping coast, like that SE. of bay D, 27 1. 
 2. What different conditions of tide and weather are shown in the 
 three parts of 25 1 ? (DE, 119.8 ; DP, 83.4 ; G, 290.2 ; T, 187.3.) 
 
SHORE LINES 99 
 
 3. About how high is the cliff (see scale at right corner) ? 4. What 
 is the tidal range (in feet) here indicated ? 5. How wide is the 
 rock bench EC between the cliff base and the low-water shore line? 
 G. What is the relation of the sea level at high tide to the cliff ? 
 [7. Prolong the profile line AB to low-water level a little outside 
 of C ; from the intersection of the profile and the low-water line 
 draw a [red] line (about parallel to the block front, outside of the 
 rock bench) to show the initial shore line (as if the sea had not cut 
 any cliff in the land slope). 8. Which is the more irregular, the 
 initial shore line or the present shore line ? Explain.] 9. Why is 
 there so little rock waste at the base of the sea cliff? 10. Where 
 has much of the coarser waste been deposited ? 11. Where has most 
 of the fine waste been deposited ? NOTE : On the narrow, wave- 
 cut rock bench of a bold, exposed coast, little rock waste is carried 
 by waves and currents along the shore, because the waste is soon 
 swept off into comparatively deep water. 12. In calm weather the 
 sea water on a rocky coast is very clear. Why does it become some- 
 what turbid in stormy weather ? [13. Explain the origin of the 
 two sea caves in the cliff of the low-tide part of 25 1 ; of the rock 
 a r <'li in the high-tide part; of the little cove (just beyond the rock 
 arch) ; of the narrow chasm (this side of the rock arch) ; of the out- 
 standing stack (in the farther part, showing storm waves) ; of the 
 skerries (small rocks or minute islands in the high-tide part) ; of 
 the heap of rock waste (where high-tide and low-tide parts join).] 
 14. Where is the rock structure indicated ? Is it horizontal or dis- 
 ordered ? !.">. Why may the district of which 25 1 is a part be 
 described as " well-subdued mountains with a very young shore 
 line." 16. What change will the sea cliff suffer if the storm waves 
 continue to cut away its base ? 
 
 6. 1. Draw, on the near end of 25 1, a profile at M, parallel to 
 BE, to show the position of the sea cliff after it has been worn 
 farther back. 2. From the base of cliff M draw a rock-bench profile 
 parallel to EC. [3. How high is the new cliff M ? How wide is 
 its rock bench ? How far has cliff M retreated from cliff B ? 
 
100 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 4. Indicate between C and D a new deposit of rock waste (about 
 as much as is shown at D}. 5. What effect has this deposit on the 
 depth of the water between C and D ? NOTE : During storms the 
 loose material on the sea bottom is agitated at depths of 100' 
 or more. 6. What effect will this agitation have on the texture of 
 the sea-bottom waste ? 7. What will become of the " grindings " ?] 
 8. Draw the profile for the cliff, bench, and bottom deposit for 
 point N? 9. As the cliff is cut back, what change takes place in 
 its height ? in the width of the rock bench ? 10. What effect will 
 the new height of the cliff have on the amount of rock waste 
 weathered from it? 11. What effect will the new width of the 
 bench have on the strength of the waves at the cliff base ? NOTE : 
 As these changes go on along the shore, there comes a time when 
 so much waste is supplied from the weather-beaten cliffs that it 
 cannot all be quickly swept away into deeper water by the weak- 
 ened waves ; a sheet of coarse and fine waste .thus comes to spread 
 over more or less of the rock bench. That part of the waste sheet 
 which is bare at low tide is called a beach. 
 
 7. 1. 252 is a general view of a shore line on a smaller scale 
 than 25 1, but on a larger scale than 27 1. 2. How high is the cliff 
 QR in 25 2 ? How wide is the beach-covered rock bench RL ? How 
 thick is the beach deposit at L ? 3. Does 25 2 represent a more or 
 a less advanced stage of shore development than 25 1 ? Explain. 
 4. The rock bench is now so wide that some of the beach material 
 (cobbles, gravel, sand), when agitated by storm waves, is slowly 
 shifted along shore by the local current. 5. Does the beach mate- 
 rial come from the shore cliffs or from the inland valleys ? Ex- 
 plain. 6. In which direction in 252 has the beach material been 
 shifted? How can you tell? 7. Why may ST be described as a 
 barrier beach (or sand and gravel reef) inclosing part of an initial 
 embayment ? 8. Has the barrier beach (or reef) been built up from 
 the bottom or forward from one end? (See 25 3, a cross section 
 showing lines of reef growth.) [9. In which part of the barrier 
 beach is it thickest ? 10. How deep was the water originally at 
 
SHORE LINES 101 
 
 the mid-point of the reef ? (Join the hill slopes QS and UT by a 
 curved line to show the original depth of the bay between the hills ; 
 estimate the depth of the curve below the high-tide shore line.) 
 NOTE : The height of the reef is increased by the action of storm 
 waves, which may throw up cobbles and pebbles in a ridge 10' or 
 20' above high tide. 11. Estimate the thickness of the reef ST at 
 its middle.] 
 
 8. 1. At which end of the reef ST in 25 2 is a passage or inlet kept 
 open ? 2. What does the position of the inlet indicate as to the 
 general direction of the longshore currents ? 3. In what direction 
 will a tidal current flow through the inlet while the tide is slowly 
 " falling" on (withdrawing from) the beach? while the tide is 
 slowly " rising " (advancing) on the beach ? 4. What name is given 
 to these tidal currents ? For about how many hours does each 
 current run? (DE, 119.9; DP, 83.8; T, 187.7.) 5. What sort of 
 material will be carried into the inclosed bay or lagoon by the inflow- 
 ing current when the sea water is turbid during storms ? 6. What 
 will become of this material in the quiet water of the lagoon ? 
 7. What effect will be thus produced on the size of the lagoon ? 
 NOTE : A deposit of fine silt, mixed with decaying plant material, 
 is formed on the bottom and around the border of a lagoon ; when 
 it is built up to high-tide level and has salt grass growing on it, 
 it is called a tide marsh. 8. Shade [light red] the sand and gravel 
 reef ST, and [light blue] the lagoon A ; dot [blue] the tide marsh 
 TM. 9. Draw a [blue] line around the original shore of the 
 inclosed bay ; prolong this line seaward from S and T. 10. Draw 
 a similar [blue] line around the original shore of bay B ; draw a 
 [blue] line to indicate the original shore line of hill U. (See the 
 dotted line, showing the original sea bottom, in front section.) 
 11. How was the original shore line produced ? [12. In what stage 
 of erosion was the region before the original shore line was thus 
 formed?] 
 
 9. 1. When a reef extends only part way across a bay, it is 
 called a spit. Where is a spit shown in 25 2 ? Why may it be 
 
102 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 called a hooked spit ? 2. Does much, waste from cliff U now go 
 to the beach of cliff A' ? from cliff Q to the spit of bay B ? (Beach 
 material may be swept past a narrow tidal inlet on the shallow 
 bottom formed by the extension of the beach material offshore.) 
 [3. What accident has happened along the face of cliff U ? 4. Did it 
 take place lately or a long time ago ? Why ? (Extensive landslides 
 of this kind took place on the S. coast of England in 1839.)] 
 5. What part of 25 2 best indicates the general outline which the 
 shore had before the cliff, spits, and reefs were formed ? 6. Was 
 the original outline more or less irregular than the present outline ? 
 7. When a shore line is in the stage represented by 25 1, is its 
 irregularity greater or less than in the initial stage ? than in the 
 stage of 25 2 ? [8. When the cliffs Q, U, X in 25 2 have been cut 
 back about 200' farther, what will have happened to the reef ST? 
 to the hooked spit of the bay B ? 9. Draw the shore line and 
 the cliff crests [red] in that stage ; shade [red] the cliff faces. 
 10. Draw the shore line and the cliff crests [blue] when the shore 
 has been cut back to W; shade the cliffs [blue].] 11. Will the later 
 changes in 25 2 make the shore line more or less irregular than 
 now ? 12. Will the extent of shore line bordered by cliffs increase 
 or decrease ? 13. Let the term fully mature be applied to a shore 
 line that has been cut back of all the initial bay heads. Do cliffs 
 form a greater fraction of the shore line in such a stage than in 
 the stage of 25 2 ? 14. Compare in a general way the shore-line 
 features of the initial stage, of early youth (25 1), of early maturity 
 (25 2), and full maturity. [15. Which is greatest, the retreat of a 
 cliff or the wearing down of the rock bench in front of it ? Why ? 
 16. How is the depth of the sea in deep water offshore from a cliff 
 affected by the cutting of the shore cliffs ?] 
 
 10. 1. In 27 2 sea cliffs are indicated by heavy hachures along the 
 more exposed parts of the coast (the cliffs are given more breadth 
 than they should have, in order to make them distinct) ; spits and 
 reefs, by dotted belts at bay mouths ; deltas and tidal marshes, by 
 dotted spaces at bay heads and on bay sides. The high-water shore 
 
SHORE LINES 103 
 
 is a heavy line ; the low-water shore is a lighter line (omitted where 
 the ragged rock bench has no beach). 2. Compare 27 1 and 2, 
 beginning at SE. corner, and state how 27 2 differs from 27 1 along 
 the outer coast SE. of bay D at the entrance to the two E. branches 
 of bay Z>; in the larger island on the NW. side of bay D; in the 
 outer island between bays D and C ; in the peninsula between bays 
 D and C ; along the NW. side of the isthmus of this peninsula ; in' 
 the island between bays C and B ; in the two small bays NE. of 
 this island ; between the inner and outer parts of bay B and of 
 bay A ; in all the bay heads. 3. Is the shore line of the spits and 
 reefs at the bay mouths convex or concave to the sea? 4. Shade 
 [light blue] in 27 2 the space where the sea has cut away the land. 
 (The initial shore line of 27 1 is partly indicated by dotted lines 
 in 27 2.) 5. Shade [light red] in 27 2 the reefs, inclosed lagoons, 
 deltas, and tidal marsh. 
 
 11. 1. Why may the island on the NW. side of bay D, 27 1, be 
 described in 27 2 as a land-tied island remnant ? 2. Compare its 
 isthmus with that of the DC peninsula, in 27 1, as to origin and 
 material ; with the isthmus of the land-tied island between bays 
 C and B, 27 2, as to shape. 3. There is a small land-tied island at 
 the head of bay C, 27 2 ; compare the manner of its becoming tied 
 to the mainland with that of the other land-tied islands. [4. Part 
 of the original NE. branch of bay C, 27 1, is now inclosed ; com- 
 pare the method of its inclosure with that of the small inclosed bay 
 heads (lagoons) on the NW. side of the entrance to bay C. NOTE : 
 Lagoons that are not entirely inclosed receive the salt water of 
 flood tide through their inlets. Lagoons that are inclosed usually 
 become fresh, as the original salt water slowly flows out through 
 the sand reef and is replaced by water from the land. 5. Mark 
 in 27 2 two salt lagoons, S ; two fresh lagoons, F. 6. Show by [blue] 
 arrows the direction in which reef material has been drifted by 
 waves and currents in the spits on the E. side of bay D ; in the 
 spits between the outer and inner parts of bay B, and of bay A ; 
 in the reefs back of the land-tied island remnant between bays C 
 
104 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 and B. 7. Has the coarser waste generally been drifted landward 
 or seaward ? Why ?] 
 
 12. [1. Complete 27 2 a (with hachures, etc.), so that it shall 
 show three reef-inclosed lagoons, one double-tied island remnant 
 with a lagoon behind it, and one vanishing island with a spit 
 behind it. 2. Complete 27 2 b (in contours, etc.), so as to show two 
 reef-inclosed lagoons, with small deltas at their heads, and a 200' 
 cliff at the end of the middle headland. What is the contour in- 
 terval ? 3. Complete 27 2 c, so as to show the initial bay heads and 
 the new-formed deltas in proper relation to the streams, and two 
 spits nearly inclosing the bay ; also (in broken lines) the former river 
 system here dismembered by drowning. 4. Complete 27 2 d, showing 
 two delta-tied islands and two delta-inclosed lakes. 5. Tidal cur- 
 rents are stronger in bays than on the outer shore line. The inflow- 
 ing tidal current, or flood tide, of bay C, 27 2, is indicated by curved 
 dotted lines. 6. The finer shore waste, when agitated by waves, is 
 slowly drifted inward by the flood current ; spits pointing inland 
 may be thus formed. Print T by three such spits in bay C, 27 2.] 
 [7. In what part of what state is the district of 39 2 ? 8. Mark 
 [red] lines along the outside of five barrier beaches, inclosing 
 lagoons. 9. Do the lagoons behind these beaches occupy all of the 
 original bay heads ? Explain. 10. Mark short [red] hachures (as 
 in 27 2) where you think sea cliffs have been cut. 11. What name 
 is given to a land-tied island ? 12. Draw a heavy [blue] line to 
 show the remaining parts of the original shore line. 13. Is the 
 present shore line on the whole more or less irregular than the 
 original shore line ? 14. How was the original shore line pro- 
 duced ? 15. What was the previous general form of the hills and 
 valleys in this district ? 16. Draw in 39 2 the original outline of 
 the shore line.] 
 
 13. 1. What is the chief difference between the shore lines of 
 27 2 and 28 3 ? 2. In the change from 27 2 to 28 3, why has the 
 SE. cliff increased in height ? 3. Why have two lagoons of bay D 
 been changed to tidal rivers ? NOTE : Tidal rivers are very broad 
 
SHORE LINES 105 
 
 in proportion to their length, because their volume is supplied by 
 flood tide from the ocean, instead of by rainfall on the land ; their 
 current changes direction with the ebb and flow of the tide. 
 4. Why has the third lagoon of bay D disappeared? 5. What has 
 happened to the land-tied island remnant and to the vanishing pen- 
 insula N. of bay D, 27 2 ? to the three islands in the upper part 
 of bay C, 27 2 ? to the delta of river C ? to the three lagoons of 
 the CB headland ? to the upper parts of bays B and A ? 
 
 14. [1. What reason may be found in the form of 27 1 to suggest 
 that the rocks around the bay heads A and B are much weaker than 
 those about bay D ? and that the rocks of the hilly peninsulas in- 
 closing bay B are of intermediate hardness ? 2. As long as pebbles 
 and sand are supplied from the cliffs of the peninsulas, what forms 
 will be built farther up bays B and A ? (See 27 2.) 3. When the 
 peninsulas are consumed (as in 28 3) and the weak rocks then ex- 
 posed yield only fine waste to the cliff-cutting waves, where will 
 (most of) the fine waste be swept ? 4. In the absence of protect- 
 ing barrier beaches, will the bay mouths be narrowed or widened 
 by wave action ? Will the bay heads be enlarged by wave action or 
 filled with tide marsh ? 5. How wide are the low-tide mud flats 
 at the head of bays A and B, 28 3 ? 6. Compare these changes of 
 bay heads A and B with those of the two small branch bays on 
 the E. side of bay D. 7. What is the origin of the small island 
 between bays A and B, 283?] 8. How far back have some of the 
 headlands been cut in 28 3 ? (The initial shore line is- indicated in 
 28 3 by single dots ; the shore line of 27 2 by double dots.) 9. How 
 far has the delta of river C been built forward ? 10. How many 
 islands have been tied to the mainland thereabouts ? 11. Compare 
 the shore lines of 27 1, 27 2, and 28 3 as to length, height, and con- 
 tinuity of cliffs ; as to length and continuity of beaches ; as to num- 
 ber of islands ; of lagoons ; as to length of headlands (from bay 
 heads) ; as to general irregularity of outline ; as to the number of 
 natural harbors for large vessels (drawing 20' or more) and for 
 small vessels (drawing not more than 5'). 
 
106 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 15. [1. Locate a city near the mouth of river C, 28 3. Where 
 would you place a lighthouse near the entrance to bay C ? Mark 
 it LH. 2. Draw in 28 3 a the shore lines for three successive stages 
 (see the guide lines ; draw the first shore line dotted ; the second, 
 broken ; the third, full) ; for the third outline indicate the cliffs, 
 sand reefs, etc., as in 27 2 and 28 3. 3. In the first outline, how 
 many small bays are partly inclosed by spits ? wholly inclosed by 
 reefs ? 4. In the second outline, how many lagoons have been 
 filled ? how many destroyed by retreat of cliffs to lagoon head ? 
 
 5. In the third outline, how many bays have disappeared entirely ? 
 how many remain as lagoons more or less filled with tide marsh ? 
 
 6. In 28 3 b draw a new shore line showing changes such as have 
 happened to bays A and B in 28 3. Indicate the shore cliffs and the 
 low-tide line. How wide are the low-tide mud flats ? 7. In 28 3 c 
 note that the largest river enters the W. branch of the N. bay ; let 
 these bay heads be many miles from the exposed outer shore line. 
 Draw three successive delta outlines for the seven streams. In the 
 third outline, what has happened as to island tying ? as to bay 
 closing ? as to river lengthening (for the largest river) ?] 
 
 16. 1. Compare 28 3 and 4, as to irregularity of shore line. 2. In 
 what part of 28 4 has the shore line been most simplified in the 
 change from 28 3 ? (The outline in 28 3 is indicated in 28 4 by 
 three-dot lines.) 3. Are the beaches more or less continuous than 
 before ? Explain. 4. Where are the beaches still interrupted ? 
 Why ? 5. Where is the broadest space between high- and low- 
 water lines ? Why ? 6. Why has the first SE. cliff retreated more 
 than the second SE. cliff ? the fifth less than the fourth ? 7. Are 
 the cliffs of 28 4 generally higher or lower than the cliffs of 28 3 ? of 
 27 2 ? of 27 1 ? Why ? 8. In 28 4 a, will further retreat of the cliffs 
 give them a greater or a less height ? Explain. 9. Are any cliffs of 
 decreasing height shown in 28 4 ? Mark in front of them ; mark 
 -fin front of the cliffs of increasing height. 10. In which of the 
 four stages of shore-line development 27 1, 2, 28 3, 4, are protected 
 harbors most common ? Why ? [11. The coast of California for 
 
SHORE LIXES 107 
 
 many miles K. and S. of the Golden Gate is about as harborless 
 as the coast of 28 4.J 
 
 17. [1. Imagine some wet-weather streams flowing W. between 
 the foreground hills of 28 4 a. Why may they be described as be- 
 headed by cliff retreat ? 2. Draw some dotted [blue] lines in 28 4 
 to show similarly beheaded wet-weather streams. 3. Examine 28 4 b. 
 Is the small stream that comes down from the background hills as 
 long as it used to be ? Explain. 4. Why may such a stream be 
 described as betrunked by cliff retreat ? 5. Mark BC at the mouth 
 of such a stream in the NW. part of 28 4. 6. Does the stream of 
 2846 enter the sea at grade (in accordant fashion), or by a hanging 
 mouth (in discordant fashion) ? 7. Are the streams of such hang- 
 ing valleys likely to be large or small ? ^Explain. 8. Compare this 
 case with that of the side streams in the mountain gorge, Exercise 
 V, 12, question 9. 9. Mark H by the mouth of a hanging valley 
 in the E. part of 28 4 ; in 1 1. 10. The dotted lines on the sea 
 surface of 28 4 a represent the crests of successive waves driven 
 by an E. wind. Where do they first break on the beach ? Why ? 
 11. How does the breaking wave then advance along the beach ? 
 Why ? 12. Why would a man standing on the cliff top hear a con- 
 tinuous " roar " from a series of wind-driven waves ? Compare the 
 regular advance of such wind-driven waves along the beach in 28 4 a, 
 with the arrival of a wave on the coast of 25 2. NOTE : In calm 
 weather the advancing swell of a distant storm adjusts itself to 
 the curves of a mature shore line, and falls over in surf almost 
 simultaneously for distances of half a mile or more. 13. How 
 does the sound of such surf differ from that of the wind-driven 
 waves of question 12?] 
 
 18. [1. Compare the sea cliffs of 28 4 with the cliffs in the 
 canyon of Exercise IV, as to relation to baselevel (sea level) ; as 
 to relation to structure (the structure of the land mass in 28 4 may 
 be taken to be similar to that of 25 1) ; as to uniformity of height 
 (from base to top) ; as to occurrence of talus (the active attack of 
 the waves at the base of a sea cliff prevents the accumulation of 
 
108 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 much talus along the shore line) ; as to change in height of cliff 
 face with advancing development ; as to change in plan or pattern 
 (as seen on a map) with advancing development.] 
 
 19. 1. Compare the shore line of 29 5 and 28 4 as to regularity 
 (or simplicity) of outline ; as to continuity of cliff front ; as to con- 
 tinuity of beaches. 2. Explain the differences. 3. In what re- 
 spects may the shore line of 29 5 be called " more fully mature " 
 than that of 28 4 ? [4. Mark H opposite the mouths of two hanging 
 valleys in 29 5.] 5. Compare the hilltop heights along the N. 
 borders of 28 4 and 29 5. (The contour interval is 50'.) 6. Which 
 is more rapid, marine erosion along the shore line, or subaerial 
 weathering of the hills ? 7. In 29 5 a stream flows SE. (in NW. 
 part of figure) ; compare in 27 1 and 29 5 its fall (feet per mile), 
 and the form (openness) of its valley. 8. Explain the differences. 
 
 9. Shade [light blue] the area of lost land in the SE. part of 29 5. 
 
 10. While the hills have been (slowly) worn down by weathering, 
 and the shore line has been (more rapidly) worn back by the waves, 
 what has happened to the rock bench offshore ? NOTE : The down- 
 wearing of a rock bench, a mile or more offshore, cannot be very 
 rapid ; but it must proceed as long as storm waves effectively 
 jostle and grind the waste that lies on it. [11. Why will the outer 
 (offshore) part of a rock bench be worn deepest ? 12. The depth 
 of the water in 29 5 along the original outer shore line, SE. of bay 
 D, 27 1, may now be about 80' ; at the original headland between 
 the two E. branches of bay D, 27 1, 50'. The drowned valley of 
 river Z), 27 1, may now be partly filled with land waste, so that its 
 depth at the inner and outer ends of the broken line in 29 5 is 60' 
 and 80'. 13. Enter these depths on 29 5 (several depths are already 
 indicated there). 14. Draw sea-bottom contours in SE. part of 29 5 
 for 50' and 100'. 15. Do these contours indicate that the surface 
 there is smoother or rougher than the corresponding surface of 
 2Tl? Explain.] 
 
 20. 1. In what respects does 29 6 resemble 29 5 ? 2. Draw in 
 29 6 a [blue] line corresponding to the mature cliff line of 29 5. 
 
SHORE LINES 109 
 
 3. The broken lines in 206 are contours for 50', 100', and 150'. 
 What movement (elevation or depression of the region with respect 
 to sea level) has taken place since 295? 4. Did the movement 
 occur soon after or long after the stage of shore-line development 
 shown in 29 5 ? 5. What is the present altitude of the former 
 shore line in the SE. part of 29 6 ? in the NW. part ? 6. Was the 
 movement by which 29 5 was changed to 29 6, of uniform amount 
 in all parts ? 7. How did it vary ? 8. What name may the new 
 land area be given ? 9. In what exercise have land forms of this 
 kind been already studied ? 10. In what stage of development is 
 the new land form of 29 6 ? Why ? 11. Print B, C, D on the rivers 
 of 29 6 corresponding to three bays of 27 1. 12. Why does such corre- 
 spondence exist? 13. AVhy may the rivers. on the coastal plain of 
 29 6 be classed as consequent ? 14. Why may they be described as 
 extended by emergence (or elevation) ? 15. How many streams of 
 29 5 are now united in river D ? 16. Why may these streams be 
 described as engrafted by emergence (or elevation} ? 17. What con- 
 trasted description was suggested for the streams of 27 1 ? (See 
 3.) [18. To what class of land forms does the land of 29 5 
 belong ? (The structure of the land may be taken as similar to 
 that shown in 25 1 and 2.) 19. In what stage of development is 
 the land area of 29 5 ? of 27 1 ? of the NE. part of 29 6 ? (As to 29 6, 
 note whether the inland area is still in the same cycle of erosion 
 with the two preceding figures, or whether that cycle has been in- 
 terrupted by elevation and a new cycle thus introduced.) 20. Com- 
 pare the sea cliff of 29 5 with the elevated sea cliff of 29 6, as to 
 altitude of baseline ; as to amount of talus at the base ; as to steep- 
 ness of cliff face. 21. Elevated sea cliffs occur at several different 
 levels around the E. end of Cuba. What does this indicate ?] 
 
 21. NOTE : 29 5 a, b, c, d, represent, in block diagrams, the 
 changes in the shore line of a low coastal plain of weak (imperfectly 
 consolidated) strata, fronting on a shallow ocean margin. The 
 initial profile of the land and sea bottom is shown by a full (or 
 broken) line. Slopes are much exaggerated. 1. While a very low 
 
110 EXERCISES IX PHYSICAL GEOGRAPHY 
 
 "cliff" is worn at k, 29 5 a, what has taken place at n ? at m ? 
 NOTE : In a shore of this kind the water is so shallow that little 
 of the storm-wave strength is spent on the land border ; more of 
 it is spent in agitating the loosened material at a moderate dis- 
 tance offshore, as about n. The coarser material is slowly shifted 
 landward and forms a shoal, as at m ; eventually the shoal is built 
 up above sea level, forming a reef, and inclosing a lagoon ; sand 
 is blown from the reef beach into the lagoon, and the reef is 
 broadened. 2. Draw the outline of a narrow reef on the sea sur- 
 face of 29 5 a, and mark it R ; mark the inclosed lagoon L. 3. The 
 finer material shifted from n is carried seaward and deposited some 
 distance offshore, beyond q. 4. Where is the sea bottom thus deep- 
 ened ? where made less deep ? 5. How does the reef in 2<) 5 b differ 
 from the reef drawn in 29 5 a ? 6. Where has the material for the 
 widened reef come from ? 7. How has it been carried ? 8. How 
 has the depth changed at n ? at q ? Why ? 9. How has the 
 width of the lagoon been changed from 29 5 a to 5 b ? 10. How is 
 the tide marsh of the lagoon shown in the front section of 29 5 b ? 
 11. Compare in 29 5 b and 5 c the breadth of the reef ; the distance 
 of the reef (outside) from the border of the mainland ; the depth 
 of the sea at n ; at q. NOTE : The depth at q and n has been so 
 much increased that the reef front is now attacked by the waves, 
 and the reef retreats. 12. W T hy does some of the reef in 29 5 c lie 
 on the tide marsh ? 13. In some cases tide-marsh mud is found to 
 " outcrop " on the outer beach of a reef. Draw a [red] profile in 
 29 5 c so as to represent this condition. Explain it. 14. As the re- 
 treat of the reef continues, what becomes of the lagoon ? 15. Ex- 
 plain 29 5 d. 
 
 22. 1. Which part of the coastal plain, 29 6, has the strongest 
 seaward slope ? the weakest seaward slope ? 2. Has an offshore 
 sand reef been built opposite the part of stronger or of weaker 
 slope ? 3. Which part of the plain has been cut back in a low 
 sea cliff ? 4. Why has a reef been formed along one part of the 
 shore line while a cliff has been cut along a neighboring part ? 
 
SHORE LIXES 111 
 
 5. Where has most of the material for the reef come from ? 
 
 6. Describe the change along the shore from the reef to the cliff. 
 Explain it. 7. Why does the reef bend outward at a certain point ? 
 8. Where is the reef interrupted by a tidal inlet ? 9. On which 
 side of the inlet is the reef set off (or offset) farther from the main- 
 land ? 10. From which direction does the prevalent longshore 
 current come (see broken-line arrows) ? 11. Make a rule, showing 
 the relation between the offset of a sand reef at an inlet and the 
 direction of the prevalent longshore current. 12. Which has the 
 smoother outline, the outside or the inside of a sand reef? Why ? 
 [13. At times of heavy storm the waves may wash over the reef at 
 certain points ; the sand thus carried into the lagoon forms what 
 maybe called a hurricane delta. 14. Where does such a delta occur 
 in 29 6 ? Compare its position with that of one of the small stream- 
 made deltas.] 15. The sand, drifted along the beach reef, is swept 
 at each inlet somewhat offshore by the ebb tide, and is carried into 
 the lagoon by the flood tide. Why may such deposits be spoken 
 of as tidal deltas? 16. Why is the tidal current stronger in the 
 inlets than elsewhere ? 17. What effect will the strong tidal current 
 have on the depth of the inlet ? NOTE : The outer tidal delta is 
 commonly called a bar. 18. How will the depth of water on a bar 
 at high tide affect the trade and growth of a village on the main- 
 land shore of a neighboring lagoon ? [19. A large part of the coast 
 line of the Atlantic and Gulf coastal plain in the southeastern 
 United States is fronted by sand reefs, broken by relatively shallow 
 inlets. 20. What effect will this have on the growth of commercial 
 cities along the coast? 21. In southern Texas a sand reef incloses 
 a lagoon for 90 mi. without a break. What effect will this have on 
 the growth of cities on that part of the coast ?] 
 
 23. 1. To what part of 29 6 does 29 7 correspond ? Compare 29 6 
 and 7 as to number of rivers and branches ; as to fall of river D in 
 feet per mile ; as to prominence of the main river delta ; as to area 
 of tide marsh and lagoon ; as to position of tidal inlet (measure 
 distance alongshore from W. border) ; as to reef offset at the inlet ; 
 
112 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 as to length of cliffed shore line. 2. Explain the changes. 3. Sup- 
 pose that the cliffed shore continues to retreat in 29 7, that the 
 main delta continues to grow outward, and that the reef near the 
 W. border of the figure is now retreating (see 29 5 c). Draw a 
 [blue] line in 29 7 to show the shore line thus changed (" or " 
 retreat at each end of shore line) ; another [blue] line to show a 
 later change (in this line let the delta front be worn a little back) ; 
 a third [blue] line to show a still later change (the whole shore 
 line retreating). 4. On the third line is any of the original shore 
 line of the coastal plain preserved ? Where, and why ? 5. What 
 fraction of the total shore-line length is then cliffed ? In what 
 stage of development is the shore line so drawn ? [6. Examine 
 the E. branches of river D. Where is their fall most rapid ? Why ? 
 
 7. Draw a [red] line connecting these parts of most rapid fall. 
 W 7 hat may such a line be called ? (See Exercise III, 5.) 8. If 
 29 7 showed as much of the coastal plain as 29 6, what would be the 
 general position of the fall line with respect to the coastal plain ? 
 to the oldland ? 9. What peculiar feature appears in the oldland 
 valleys of 29 7 ? Explain it. 10. Why may that part of the district 
 be described as having " young valleys in the bottom of its older 
 valleys " ? 11. Draw a cross profile of these valleys.] 
 
 24. 1. By what process has 29 7 been transformed in 29 8 ? 
 2. What amount of regional movement has occurred ? 3. Does the 
 movement appear to have been uniform or of unlike amount in 
 different parts ? 4. Did the movement begin immediately after 
 the stage reached in 29 7 ? How can you tell ? 5. In what stage of 
 erosion was the coastal plain when the movement began ? 6. Does 
 29 8 represent a stage immediately after the movement ceased, or 
 has some time passed since the movement ended ? How can you 
 tell ? 7. Draw a [red] line to show the shore line of 29 8 as it 
 was when the movement ceased. How does that shore line differ 
 from the shore line printed in 29 8 ? 8. Why are some of the bays 
 longer than others ? Why do the bays branch ? 9. In 27 1, 29 6 and 
 
 8, which one has a- shore line of (lancT) elevation ? a shore line of 
 
SHORE LINES 113 
 
 (land) depression? 10. Which one has a simpler outline, a shore 
 line of elevation or a shore line of depression ? Why ? 11. About 
 how high are the little cliffs of 29 8 ? 12. How many bays (lagoons) 
 are entirely inclosed by sand reefs? partly inclosed? 13. Which 
 bays have fresh water ? salt water ? Why ? 14. Locate a city in 
 29 8 so that it shall have a good harbor for ocean-going vessels and 
 a convenient relation to the interior country. Explain the advan- 
 tages of the point you select. 15. What is the present stage of 
 shore-line development in 29 8 ? 16. Draw a [blue] line in 29 8 
 to show the shore line in a later stage of development (retreat 
 of J-^ mile). 17. Draw a [red] line to show the fall line of 298. 
 18. Which parts of the streams may be called revived? [19. I.n 
 what part of what state is the district shown in 27 1 a ? 20. With 
 which diagram in this exercise does it best correspond ? 21. How 
 many partial cycles of erosion are represented ? (Remember that 
 a movement of elevation or depression interrupts the preceding 
 cycle at whatever stage it has reached, and introduces a new cycle.) 
 
 22. In what stage was the earlier cycle when it was interrupted ? 
 
 23. Was it interrupted by a land movement of elevation or of 
 depression ? 24. What has happened since the new cycle was intro- 
 duced ? What stage has it now reached ? 25. Draw a [red] line 
 to show the shore line at the beginning of the new cycle. About 
 how far have the shore cliffs retreated ? 26. In what part of what 
 state is 27 2 e ? (It lies about 80 mi. EXE. of 35 1.) 27. How high is 
 the shore cliff ? In what stage of development is the shore line ? 
 
 28. In what stage of development is the lacustrine coastal plain ? 
 
 29. In what stage is the stream near the left end of the map ? 
 
 30. Do the stages of development of the plain, the stream and 
 valley, and the shore line agree or differ? Explain. 31. What op- 
 portunity for harborage is offered by such a shore line ?] [32. Com- 
 pare the first picture on the next page with the picture on page 17. 
 In which case has the region recently been elevated ? in which, de- 
 pressed ? How can you tell ? 33. With Avhich map of this exercise 
 may the second picture on the next page be compared ?] 
 
114 
 
 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 25. 1. Define : 3, rivers dismembered by submergence, embayed 
 coast, half-drowned district ; 5, sea cliff, initial shore line, rock 
 beach, high tide, low tide, tidal range, sea cave, rock arch, cove, 
 chasm, stack, skerry, young shore line ; 6, beach ; 7, barrier 
 beach, sand reef; 8, tidal inlet, flood tide, ebb tide, lagoon, tide 
 marsh ; 9, spit, hooked spit, initial (or original) shore line, young 
 shore line, early mature shore line, fully mature shore line ; 11, 
 land- tied island remnant; [ 12, delta-tied island, delta-inclosed 
 lakes;] 17, streams betrunked by cliff retreat; 20, rivers ex- 
 tended by emergence, rivers engrafted by emergence, elevated 
 sea cliffs ; [ 22, hurricane delta ;] 24, shore line of elevation, 
 shore line of depression. 
 
EXERCISE X. THE DISTRIBUTION OF TEMPERATURE 
 
 OBJECT. To learn the distribution of temperature over the world and 
 its changes with the seasons. 
 
 Preliminary. This exercise treats of the temperature of the lower 
 air, near the surface of the land or sea. The temperature of the 
 air is determined by the thermometer, placed where it is open to 
 the wind but sheltered from sunshine and rain. The Fahrenheit 
 scale is here used. Observations of temperature have been regu- 
 larly taken, day after day, in many parts of the world for many 
 years, and the results have been charted, as explained below; so 
 that the distribution of temperature is easily studied by means of 
 maps. This exercise uses Plates 30 and 31. 
 
 1. 1. The figures in 30 1 are records of temperature, such as 
 might be determined by observations taken at the same hour in 
 various parts of the central United States. In what states there 
 shown do temperatures higher than 60 prevail at this time ? tem- 
 peratures lower than 10 ? 2. Complete the line separating the part 
 of the map where the temperature is over 40 from the part where 
 the temperature is under 40. What is the temperature of places on 
 this line ? NOTE : Such a line is called a line of equal temperature, 
 or isotherm. 3. Print 40 at each end of the isotherm. 4. Draw 
 the isotherms for 50, 60 ; for 30, 20, 10, 0. Print the proper 
 numbers at each end of these isotherms. 5. Why is the distribution 
 of temperature more clearly shown by the isotherms than by. the 
 separate observations ? 6. Draw a line from SE. Texas across the 
 map, to show the path you would follow in order to find the most 
 rapid decrease of temperature ; draw similar lines from S. Illinois ; 
 from SW. Tennessee. 7. Are these lines parallel ? Are they straight? 
 8. What is the relative direction of the lines of temperature decrease, 
 
 115 
 
116 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 or lines of temperature gradient, and the isotherms ? 9. In what 
 part of what state is the most rapid decrease of temperature, or 
 the strongest temperature gradient, found? 10. In what part of 
 the map is the decrease of temperature least rapid, or the tempera- 
 ture gradient weakest ? 11. How is the strength or weakness of the 
 temperature gradient indicated by the spacing of the isotherms ? 
 
 12. How much stronger is the temperature gradient in E. Kansas 
 than in Arkansas ? How can you tell ? 13. Draw three more tem- 
 perature gradient lines across the map. What is their general direc- 
 tion ? 14. If temperatures remain as in 30 1, in what directions 
 might one travel from SW. Missouri to find no change of tempera- 
 ture ? Would the path of travel be straight or curved ? 
 
 2. 1. What is meant by the mean annual temperature of a 
 place ? (DE, 34.7.) How is it determined ? 2. What does 30 2 
 show ? 3. Shade lightly [red] all the space in so 2 where the 
 mean annual temperature is over 70 ; [blue] under 30. 4. Print 
 ArCtic Cold Cap, N. Temperate Belt, Torrid Belt, S. Temperate 
 Belt, AntarCtic Cold Cap on the five belts indicated by the shading 
 and blank spaces on 30 2. 5. Why are two of these spaces called 
 " caps," and the other three " belts " ? 6. What countries of N. and 
 S. America are in the several belts? of Europe and Africa? of Asia 
 and Australia? 7. Which grand division of land (N. America, S. 
 America, Europe, Asia, etc.) has the largest area in the Arctic cold 
 cap ? in the torrid belt ? 8. In what belt is your school ? 9. Draw 
 a [blue] line along the isotherm of 50 in each hemisphere. In 
 which belt is the 50 isotherm more regular ? 10. Draw lines to 
 show parallels of latitude 60 N. and S. (nearly halfway from the 
 parallel of 40 to that of 80). 11. Estimate the successive highest 
 and lowest temperatures through which these lines pass. Print the 
 figures indicating these temperatures in their proper places. 12. On 
 which of these lines is the greatest temperature variation found ? 
 
 13. Shade with vertical lines the areas of more than 80 mean annual 
 temperature. 14. Do these areas lie chiefly on land or on water ? 
 15. Shade in the same way the area of less than 10. 16. Does it 
 
117 
 
 extend farther toward the equator on land or on water ? 17. Is the 
 poleward decrease of temperature (poleward temperature gradient) 
 in the N. temperate belt stronger on Asia or on the N. Atlantic? 
 on the N. Pacific or on 1ST. America ? on northern continents or on 
 northern oceans ? 
 
 3. 1. What do 31 1 and 2 show ? 2. On these maps shade the 
 areas under 30 [light blue] and over 70 [light red] ; shade more 
 heavily the areas under and over 80. 3. Where are the hot 
 regions (monthly mean over 80) in January ? in July ? 4. Where 
 are the very cold regions (monthly mean under 0) in January ? in 
 July ? 5. In what month have the hot regions the greatest area ? 
 the cold regions the greatest area ? Why ? (DE, 52.2 ; G, 245.3 ; 
 T, 238.2.) 6. In what direction from your school is the nearest 
 cold region in January ? the nearest hot region in July ? 7. Draw 
 on 31 1 and 2 lines of temperature gradient through your school for 
 January and July. What are the directions of these lines ? NOTE : 
 If the temperature maps extended farther south, a region of great 
 cold would be shown near the South Pole in July. 8. In what 
 parts of the world and in what month do the hot regions extend 
 farthest from the equator ? the very cold regions farthest towards 
 the equator ? Why ? 
 
 4. 1. Make a mark across each meridian in 31 1 where the high- 
 est temperature occurs. 2. How do you determine where to place 
 these marks ? 3. Draw several N.-S. lines across the areas of over 
 80 (or 90) ; place marks at the middle points of these lines. Draw 
 a curved line through all the marks. 4. Why may this curve be 
 called the heat equator for January ? 5. Estimate the highest and 
 lowest temperatures found on the January heat equator, and print 
 their values in 31 1. 6. Draw in 31 2 the heat equator for July in 
 the same way. 7. Copy the July heat equator (dotted line) on 
 31 1 ; shade with light vertical lines the belt between the two posi- 
 tions of the heat equator. What descriptive name can be given to 
 the belt thus shaded ? (Use the terms migration, heat equator, and 
 annual in your answer.) [8. Mark a strong [red] N.-S. line where 
 
118 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 the heat equator migrates from the geographic equator to 30 X. 
 lat. ; another where the migration is from 20 N. lat. to 20 S. lat. ; 
 from 15 K to 20 S.; from 10 N. to 25 N.; from 5 S. to 40 N. ; 
 from to 20 S. ; from 5 S. to 15 S.] 9. Where is the migration 
 of the heat equator of large value and about the same N. and S. of 
 the geographic equator ? Why ? 10. Where is the greatest northern 
 migration? Why? 11. Where does the belt of migration remain 
 N. of the equator all the year (DP, 40.4, 40.9) ? S. of the equator 
 all the year? Why? 12. Does the heat equator migrate farther 
 from the geographic equator on the continents or on the oceans ? 
 Why ? 13. Is the belt of migration wider on the continents or on 
 the oceans? Why? [14. Does the apparent annual migration of the 
 sun carry it the same distance N. and S. of the geographic equator? 
 How do you know ? 15. Is the annual migration of the heat equa- 
 tor symmetrical ? 16. Why do the two not agree ?] 
 
 5. 1. During what months is the heat equator migrating north- 
 ward ? 2. What general changes of temperature take place in the 
 N. hemisphere during these months ? in the S. hemisphere ? 
 3. What changes take place in these months in the slant of the 
 sun's rays in the N. hemisphere ? in the S. hemisphere ? 4. What 
 changes take place' during the same months in the length of the 
 days and nighta in the N. hemisphere ? in the S. hemisphere ? 
 (DE, 48.8-, 87.1- ; DP, 400.1- ; G, 21.3- ; T, 400-.) 5. During what 
 months does the heat equator migrate southward? Why? 6. What 
 general changes in temperature are taking place in the two hemi- 
 spheres during these months? Why? 7. Copy on 31 1 the isotherms 
 of 40 from both hemispheres of 31 2. Shade with light vertical 
 lines the belts thus indicated. 8. What names may be given to 
 these belts ? 9. Which is the wider and more irregular belt ? Is 
 it wider on the continents or on the oceans? Why? 10. Where is 
 your school located with respect to one of these belts ? 
 
 6. [1. Draw a meridian from top to bottom of 31 1 in 20 W. long. 
 Lay a strip of paper along the meridian ; mark on the edge 
 of the strip where the equator and the successive isotherms are 
 
THE DISTRIBUTION OF TEMPERATURE 119 
 
 crossed ; print the values of the isotherms near their marks. 
 2. Place the strip along any horizontal line in 30 4 a, with north to 
 right and the equator mark at EQ K . Transfer the isotherm marks 
 to the horizontal line, and indicate their values. 3. Make dots in 
 30 4 a at points above or below the transferred isotherm marks, so 
 as to represent the value of the isotherms on the vertical tempera- 
 ture scale of 30 4 a. Draw a curve through the dots. 4. Draw a 
 corresponding curve for July in so 4 a. 5. Print JANUARY on one 
 curve and JULY on the other. 6. What do these curves represent? 
 7. How is the migration of the heat equator indicated by the two 
 curves ? 8. Draw vertical lines in the space between the two 
 curves. What do these lines represent? 9. About how much does 
 the air temperature over the Atlantic change between January and 
 July in the torrid belt? in the N. temperate belt ? in the S. temper- 
 ate belt ? 10. Draw a meridian line of 20 E. long, from the S. 
 border of 31 1 to the S. point of Africa ; continue the line a little 
 E. of N. to central Arabia ; then NE. (through the small oval iso- 
 therm of 60) to the Arctic ocean, and thence N. to the N. border 
 of the map. 11. Mark EQ on the middle of a strip of paper; lay 
 the strip on 31 1, keeping EQ on the equator and moving the strip 
 parallel to the meridians ; mark on the strip the points where the 
 successive isotherms cross the line just drawn through Africa and 
 Asia ; indicate on the strip the values of the isotherms. 12. Trans- 
 fer, as before, the isotherm marks to 31 4 b, and draw the January 
 curve. 13. Do the same for July. 14. Print JANUARY and JULY 
 on the curves. What do they represent ? 15. How do they differ 
 from the curves of 31 4 a as to the temperature of the heat equator ? 
 as to the migration of the heat equator ? as to temperatures in far 
 S. latitudes ? in far N. latitudes ? 16. What difference is shown 
 by the two pairs of curves as to January-July temperature range 
 in the N. hemisphere? in the S. hemisphere? 17. Why are 
 these ranges greater in NE. Asia (31 4 i) than in the N. Atlantic 
 (31 4 a) ? 18. Draw vertical lines between the two curves of 31 4 1. 
 What do they represent ? 19. Mark arrowheads on the January end 
 
120 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 of the vertical lines. Why do some of the arrows point upwards, 
 some downwards ?] 
 
 7. [NOTE : Let the mean annual temperature range, or differ- 
 ence between the means of the warmest and coolest months (not 
 necessarily January or July near the equator) for many places be 
 entered on a map of the world ; let lines be drawn through points 
 having equal annual range. Such lines are shown in 30.3. 1. What 
 name may be given to this map ? NOTE : Temperatures in far 
 southern latitudes are not well known, but as far as 60 S. the 
 annual range over the oceans is probably less than 20. 2. Shade 
 in 30 3 with dots the regions of less than 20 annual range. 3. Shade 
 lightly with vertical lines the regions of more than 30 range ; 
 shade more heavily the regions of more than 60 range. 4. In what 
 general parts of the world is the annual range of temperature small 
 (under 20) ? large (over 60) ? 5_ How is your school situated 
 with respect to any one of these regions ? 6. How are the charac- 
 teristics of oceanic and of continental climates illustrated in 30 3 ? 
 (DE, 50.7; DP, 41.6; T, 277.3.) 7. Draw several temperature 
 gradient lines in different parts of 30 2 ; mark arrowheads on the 
 lines to show the direction of temperature decrease. 8. What is 
 the usual direction of temperature gradient lines in the N. hemi- 
 sphere ? in the S. hemisphere ? 9. What is the direction of the 
 January temperature gradient line (see 31 1) in Baffin bay (between 
 Labrador and Greenland) ? at North cape (N. point of Norway) ? 
 on NE. coast of Asia? 10. What is the direction of the July tem- 
 perature gradient line (see 31 2) in S. California ? in SE. Arabia ? 
 11. State the cause of the unusual direction of the temperature 
 gradient lines indicated in questions 9 and 10.] 
 
 8. Define : 1, line of temperature gradient ; 4, heat equator ; 
 [ 7, mean annual temperature range.] 
 
EXEECISE XI. THE PEEV AILING WINDS OF THE 
 
 WORLD 
 
 OBJECT. To learn the prevailing winds of various parts of the world, 
 their changes with the seasons, and the control that they exert over the 
 distribution of rainfall in different regions and in different seasons of 
 the year. 
 
 Preliminary. The prevailing winds for January and July are 
 charted in 32 1 and 2, as determined by observations made in many 
 different parts of the world on land and at sea. Winds are given 
 the name of the direction from which they blow. The arrows on 
 the charts fly with the winds: the heavier the arrow, the greater the 
 average strength of the wind ; the longer the arrow, the steadier 
 the wind. Little circles indicate light variable winds with frequent 
 calms. Windward means the direction from which the wind is 
 blowing ; leeward means the direction toward which the wind is 
 blowing. The winds are stronger and more regular over the oceans 
 than over the lands, where mountains and valleys affect their 
 velocity and direction. Many of the following questions refer 
 chiefly to the winds of the oceans. This exercise uses 32 1 and 2, 
 34 3 and 4. 
 
 1. 1. Examine the winds of the Atlantic ocean in 32l. Print 
 SW about the middle of the region where SW. winds prevail ; 
 NE, SE, NW, where corresponding winds prevail. 2. Draw a [blue] 
 line in the N. Atlantic separating the westerly (NW., W., SW.) 
 winds from the easterly (NE., E., SE.) winds. Prolong the line 
 westward through the Gulf of Mexico ; eastward across N. Africa 
 and S. Asia. (This line should run square across N. or S. winds.) 
 3. Draw a [blue] line in the equatorial Atlantic separating the 
 northerly (NE., N., NW.) winds from the southerly (SE., S., SW.) 
 
 121 
 
122 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 winds. 4. Draw a line in the S. Atlantic separating the easterly 
 (SK, E., NE.) winds from the westerly (NAY., W., SW.) winds. 
 
 5. Do the same for the Pacific ocean (omit the W. Pacific) ; for the 
 Indian ocean. 6. Print JAN. on the boundary lines that you have 
 thus drawn in each ocean. 7. Connect the [blue] lines across the 
 continents (omitting E. Asia), following the rules regarding wind 
 directions already given. 8. Treat 32 2 in the same way, printing 
 SW, NE, etc., in the several wind regions, and drawing [blue] 
 lines separating the regions of unlike winds. 9. Print JULY on 
 these lines. 
 
 2. 1. Around what part of the world, limited roughly by lati- 
 tude circles, do NW. (or WNW.) winds prevail in January and July ? 
 
 2. Why may this part of the world be spoken of as a wind belt? 
 
 3. Between what latitudes (roughly) do SE. winds for the most part 
 prevail? NE. winds ? SW. (or WSW.) winds ? NOTE : Although 
 the winds of these belts are somewhat irregular on the ocean (for 
 example, the SE. wind belt in the W. Pacific for January), and 
 are more or less interrupted on the continents, they are commonly 
 spoken of as if they extended all around the world. 4. What names 
 are ordinarily given to the several wind belts ? (DE, 39.5- ; DP, 
 30.1- ; G, 258.3- ; T, 259.4-.) 5. In which belts are the winds rela- 
 tively steady ? In which belts are winds less steady but stronger ? 
 
 6. Do light winds and frequent calms prevail within the wind 
 belts, or along the boundaries between them ? 7. How many such 
 belts of light winds and frequent calms are indicated ? What names 
 are given to them? (DE, 43.4, 44.5 ; DP, 32.5, 33.1; G, 260.1-4 ; 
 T, 259.2, 261.9.) 
 
 3. 1. In which ocean are the westerly winds most uniform? Why? 
 2. In which northern ocean are the westerly winds most deflected 
 from their usual WSW. direction in January? in July? 3. In 
 which ocean are the trafle winds most deflected from their usual 
 course in January ? in July ? 4. Around which grand division of 
 land (Europe, Asia, Africa, etc.) are the prevailing winds in July 
 most deflected from the wind-belt directions ? (Special account 6f 
 
THE PREVAILING WINDS OF THE WORLD 123 
 
 these deflected winds will be given in 8 and 9.) 5. Which wind 
 belt includes the greatest part of the United States ? G. On which 
 coast (Atlantic or Pacific) of the United States do the winds there- 
 fore blow prevailingly from sea to land ? from land to sea ? 
 7. In what wind belt do Mexico and Central America lie? On 
 which coast (northeast or southwest) do the winds there prevail- 
 ingly blow from sea to land ? from land to sea ? 8. What part 
 of S. America S. of the equator is covered by a belt of easterly 
 winds ? of westerly winds ? 9. What parts of the coast of S. Amer- 
 ica S. of the equator have winds prevailingly from sea to land? 
 from land to sea ? 10. Answer the same questions for Africa S. of 
 the equator. 11. What wind belt covers the greatest part of Africa 
 N. of the equator ? of Europe ? 12. Compare the E. coast of N. 
 America (Florida to Labrador) with the W. coast of Europe (Spain 
 to Norway), as to prevalence of winds from land or from sea. 
 
 4. 1. What kind of weather prevails in the doldrums at sea (DE, 
 43.6; DP, 32.6; G, 260.1 ; T, 279.9)? in the trade-wind belts at 
 sea (DE, 40.7; DP, 30.8, 52.7; G, 259.8)? in the horse latitudes at 
 sea (DE, 44.7; DP, 33.2)? in the belts of westerly winds at sea 
 (DE, 42.6 ; DP, 31.9 ; G, 258.7) ? 2. How does the weather in the 
 belt of westerly winds vary from winter to summer ? (DE, 54.8 ; 
 DP, 36.7.) 3. What kind of weather prevails in the Pacific ocean 
 just N. of the equator, 140 W. long.? in the torrid Atlantic where 
 you have printed NE and SE ? in the N. and S. Atlantic where you 
 have printed SW and NW ? 4. Would rainfall (rain and snow) be 
 more plentiful on coasts where the winds usually blow from sea to 
 land, or from land to sea ? 5. Shade [blue] in 32 2 the coasts (omit 
 E. Asia for the present) in the belts of westerly winds where plenti- 
 ful rainfall may be expected. 6. In what countries are these coasts ? 
 (Consult maps of continent, Plates 40-45, if necessary.) 
 
 5. 1. Would rainfall be more plentiful from winds that are blow- 
 ing (obliquely) towards the pole, and therefore cooling, or from 
 winds that are blowing (obliquely) towards the equator, and there- 
 fore warming? (DE, 40.4 ; DP, 30.6.) 2. Shade with [blue] lines the 
 
124 EXERCISES IX PHYSICAL GEOGRAPHY 
 
 coasts where the trade winds blow from sea to land (omit N. Africa ) ; 
 shade with [red] dots the coasts where the trade winds blow from 
 land to sea, or parallel to the shore line. 3. Which of these coasts 
 would have plentiful rainfall ? Which would be dry or desert ? 
 4. On which coast of Mexico and Central America would you expect 
 the heavier rainfall ? Why ? 5. Why is the W. coast of SW. Africa 
 a dry region, while the E. coast has a plentiful rainfall ? 6. When 
 moist winds blow across a high mountain range, ascending its 
 windward slope and descending its leeward slope, which slope of 
 the range will be rainy ? which slope dry ? (DE, 41.3 ; DP, 31.2.) 
 7. Would rainfall be plentiful or scanty on the interior lowlands 
 to the leeward of such a range ? 8. Consult the maps, Plates 40-45, 
 and 32 1 and 2, and name the coasts where the prevailing winds 
 encounter mountains as they blow from sea to land. 9. What can 
 you say as to the rainfall of E. and W. Oregon ? of California and 
 Nevada ? Explain. 10. Describe the relation of the Andes to the 
 wind belts which cross these mountains ; state the probable distri- 
 bution of forests on the slopes of the Andes. 11. In what countries 
 (see Plate 42) would the W. slope of the Andes be dry or desert ? 
 12. Compare the rainfall in different parts of Peru and of Patagonia, 
 with respect to the Andes and the prevailing winds. 13. What 
 amount of rainfall would you expect on the mountainous islands, 
 Sumatra and Borneo, between Asia and Australia? Explain. 14. 
 On which slope of the volcanic mountains of the Hawaiian 
 islands may the heavier rainfall be expected ? 15. Where trade 
 winds blow across nonmountainous interior regions and become 
 warmer as they advance, would you expect plentiful or scanty 
 rainfall? (DE, 41.1; DP, 30.8; G, 236.2; T, 281.8.) 16. Shade 
 [red] the interior parts of IS", and S. Africa and of Australia that 
 are crossed by the trade winds but not visited by the doldrum belt 
 or the horse-latitude belt. Would these regions be forested or 
 desert? 17. In what parts of each continent are these regions ? 
 
 6. [1. Copy [blue] on 32 1 the boundary lines of the wind belts 
 (or belts of frequent calms) from 322. (Place these lines carefully 
 
THE PREVAILING WINDS OF THE WORLD 125 
 
 with respect to latitude lines and to points on the coast.) 2. Print 
 JULY on the copied lines. 3. About what change of latitude takes 
 place in the position of the boundaries of the wind belts (omit the 
 Indian and W. Pacific ocean) from January to July ? from July to 
 January? 4. How does this change correspond with the change in 
 the position of the sun in the sky for the same periods ? 5. How 
 does the amount of change compare in the two cases ? 6. Compare 
 the position of the doldrums in January and July with the position 
 of the heat equator, 31 1 and 2, for the same months. 7. What seems 
 to be the relation of the doldrums and the trade winds to the heat 
 equator ? NOTE : The heat equator in January and July is a better 
 indication of the position of the doldrums on the lands in those 
 months than is given by the winds of 32 1 and 2. 8. Copy on 32 1 
 the heat equator of Africa and S. America, 31 1 and 2; print 
 JAN. and JULY on the copied lines, and let the migration of the 
 doldrums on those continents be thus defined. 9. Shade with light 
 vertical [blue] lines in 32 1 the belt across which the doldrums 
 migrate. This belt may be called the subequatorial belt. 10. Shade 
 in 32 1' the belts across which the calms of the horse latitudes 
 migrate. These belts may be called the N. and S. subtropical belts.'] 
 7. If 6 is omitted, omit 7 also. [1. What sort of weather will 
 prevail at a place on the N. side of the subequatorial belt in Jan- 
 uary ? in July ? 2. What sort of weather at a place on the S. side 
 of the same belt in January ? in July ? 3. What sort of weather 
 at a place in the middle of the same belt in January ? in April ? in 
 July ? in October ? 4. Draw a line around the area drained by the 
 river Nile in Plate 45 ; shade lightly the river basin thus inclosed. 
 Do the same for the Zambezi river in S. Africa. 5. In which month, 
 January or July, will you expect high water 'in the Nile ? in the 
 Zambezi ? Explain. (See the migration of the doldruin belt in 
 Africa, 32 1.) 6. In what parts of Africa would you expect to find 
 deserts ? grass and trees ? dense forests ? NOTE : The heavier 
 the rainfall of warm regions, the denser the tree growth. 7. The 
 plains of the interior of Venezuela, lat. 5 N., have abundant rains 
 
126 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 in July and August, but are dry in the opposite season ; the plains 
 of the interior of Brazil, lat. 10 S., have abundant rains from Decem- 
 ber to February, but are dry in the opposite season. Locate these 
 plains on Plate 42, and account for their rainy and dry seasons. 
 8. Bogota (locate on Plate 42) has abundant rainfall in April and 
 May and in October and November, and a less rainfall in the other 
 months. Account for these variations. 9. What sort of weather will 
 prevail at a place in the N. subtropical belt in January ? in July ? 
 10. What sort of weather will prevail in the S. subtropical belt 
 in January? in July? Explain. 11. In what months w6uld you 
 expect the rainy season in S. California ? in Morocco and Algiers ? 
 Locate the last two countries on Plate 45. 12. In what months 
 would you expect the rainy season in Chile, lat. 30 S. ? in Cape 
 Town, S. Africa? in S. Australia? in N. Australia?] 
 
 8. NOTE : The prevailing winds of the Indian ocean for Jan- 
 uary and July are shown in 34 3 and 4 on a larger scale than in 32 1 
 and 2. 1. In which month do the NE. trades of the Indian ocean 
 seem to extend across the equator ? 2. Why do they not stop at the 
 equator ? 3. What direction do they take after crossing the equator ? 
 4. Shade lightly the space occupied by these extended and deflected 
 trade winds in 34 3. 5. What is the direction of the winds in this 
 region in July ? (See 34 4.) 6. What name is given to winds that 
 thus reverse their directions in the opposite seasons ? (DE, 57.1 ; 
 DP, 43.5 ; G, 262.1 ; T, 256.9.) 7. In which month do the SE. 
 trades of the Indian ocean seem to cross the equator ? 8. What 
 direction do they take after crossing the equator ? 9. To about 
 what latitude are they then continued ? 10. AVhy do they go farther 
 N. than the extended NE. trades go S. of the equator ? 11. Shade 
 the region of the extended SE. trades in 34 4. 12. What is the direc- 
 tion of the prevailing winds in this region in January ? (See 34 3.) 
 13. What two regions of monsoon winds are thus shown in the 
 Indian ocean (and S. Asia) ? 14. How are they situated with 
 respect to the equator? 15. Which one is the larger? 16. What 
 is the relation of the heat equator to these monsoon regions ? 
 
THE PREVAILING WINDS OF THE WORLD 127 
 
 [17. Where else than in the Indian ocean do the NE. trades seem to 
 cross the equator in January and extend into the S. hemisphere ? 
 (See 32 1.) 18. What is the direction of the winds between the 
 equator and Australia in January ? in July ? 19. Why may these 
 winds be called the Australian monsoons ? 20. Shade [red] on 322 
 the region of these monsoons. 21. Where, besides in the Indian 
 ocean, do the SE. trades seem to cross the equator in July and ex- 
 tend into the N. hemisphere ? (See 32 2.) 22. In what small regions 
 do these extended winds show a deflection from SE. to SW. ? 23. 
 What is the direction of the January winds in these regions ? 24. 
 What name m'ay be given to the winds of these small regions ? 
 25. Shade [red] these regions in 32 2. NOTE : It is probable that 
 winds resembling monsoons, but less regular and less steady than 
 the monsoons of the Indian ocean, occur in torrid Africa and S. 
 America. 2G. How many monsoon regions of this kind may be 
 expected on these continents ? 27. Draw in 32 2 two arrows in each 
 of these monsoon regions, to show the expected wind directions in 
 January [blue] and in July [red].] 
 
 9. 1. In what month does the heat equator advance upon S. Asia? 
 2. Compare the displacement of the heat equator from the geo- 
 graphic equator, as there shown, with the displacement in other 
 parts of the world. 3. In what month does the air over Asia become 
 warmer than the air over the oceans on the SE. and N.? colder 
 than the air over the same oceans ? 4. What would you expect as 
 to the movement of the winds with respect to a region that is 
 warmer than its surrounding oceans ? colder than its surrounding 
 oceans ? (DE, 58.8- ; DP, 42.2- ; G, 262.2- ; T, 257.1-.) 5. Do 
 the winds of S., E., and N. Asia and the neighboring oceans, as 
 shown in 32 1 and 2, confirm the answers to the preceding question ? 
 6. What is the direction of the winds in China and on the neigh- 
 boring sea in January ? in July ? 7. What name may be given to 
 these winds ? 8. In what months would you expect most rainfall 
 in this region ? Why ? 9. In what months would you expect the 
 most rainfall in S. Asia? Why? 10. On which coast of India 
 
128 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 (SE. or SW.) would you expect most rainfall? Why? 11. What 
 reasons can you give for expecting an unusually heavy rainfall on 
 the S. slope of the Himalayas in July ? 12. To what great monsoon 
 system do the monsoons of the 1ST. Indian ocean and the NW. Pacific 
 ocean belong ? 13. What amount of rainfall would you expect in 
 central Asia in the colder half year ? Explain. 14. W T hat amount 
 would you expect in the warmer half year ? Explain. 15. What can 
 you say about central Asia as to its habitability ? 16. How is its 
 habitability affected by the size of the continent ? by the prevail- 
 ing winds ? by the distribution of mountains ? (See Plate 45.) 
 17. What desert occupies the central part of this continent ? What 
 mountain ranges border this desert ? 18. What smaller continent 
 than Asia illustrates the problems of question 4? 19. Why do the 
 plains of New Mexico and Colorado receive only a light rainfall ? 
 20. Why does Arizona receive only a very small rainfall ? 
 
 10. Define : Preliminary , windward, leeward ; 2, wind belt, 
 trade-wind belt, belts of prevailing westerly winds, doldrums, horse 
 latitudes ; 4, rainfall; [ 7, subequatorial belt, subtropical belts;] 
 8, monsoons. 
 
EXERCISE XII. WEATHER MAPS 
 
 OBJECT. To study the causes of weather changes. 
 
 Preliminary. The four figures of Plate 33 represent certain 
 weather elements, such as might be determined by observations 
 taken at the same hour at many different points in the central 
 and eastern United States on a first, second, third, and fifth day. 
 The chief weather elements are the temperature of the lower air 
 (DE, 28.3, 31.6, 74.8 ; DP, 27.1-, 48.5- ; G, 238.2, 246.3 ; T, 275.3, 
 420.3), pressure of the atmosphere (DE, 24.8-; DP, 23.4-; G, 
 225.6, 253.5- ; T, 231.1-, 255.3), direction and strength of the wind 
 (DE, 37.9- ; DP, 44.4 ; G, 256.9-), and state of the sky (clear, 
 cloudy, rain, or snow). Atmospheric pressure, as measured by the 
 barometer, is expressed in " inches of mercury " ; the values or 
 "readings" usually found are about 29 or 30 inches. These are 
 given in Plate 33 to tenths of an inch ; 30.2 is printed 0.2 ; 29.7, 
 as 9.7. On government weather maps pressure is given to hun- 
 dredths of an inch. The places or " stations " of observation are 
 represented on Plate 33 by the decimal points of the barometer 
 readings. The winds are named by the direction from which they 
 blow. Wind arrows fly with the wind ; the stronger the wind, the 
 longer the arrow. (See length of arrow for a wind of 20 mi. an 
 hour, in SE. corner of 33 1.) Isotherms (see Exercise X, 1) are 
 printed in fine dotted lines ; their values are indicated by numbers, 
 meaning Fahrenheit degrees, as 30, 40, 50, at their ends. The scale 
 of these weather maps may be taken as 320 mi. to an inch. This 
 exercise uses only Plate 33. 
 
 1. NOTE : The pressure of the atmosphere (the observations hav- 
 ing been reduced to a common standard, to make them comparable) 
 is indicated for various places in 33 1. 1. In what part of the map 
 
 129 
 
130 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 is the pressure more than 30.0 ? less than 30.0 ? 2. Complete the 
 line through points (0.0) where the pressure is 30.0. Such a line is 
 called an isobaric line, or isobar. Why ? 3. Draw full black lines 
 in 33 1 for the isobars of 30.1, 30.2, 30.3. 4. What is the form of the 
 isobar of 30.3 ? Draw in similar form but smaller size the isobar of 
 30.4. 5. Draw isobars for 29.9, 29.8, 29.7. 6. What is the form of 
 the isobar of 29.7 ? Draw in similar form but smaller size the iso- 
 bars for 29.6, 29.5, 29.4. 7. Print A in the center of highest pres- 
 sure ; C in the center of lowest pressure. 8. Shade lightly [red] the 
 area within the isobar of 30.3 ; and [blue] the area within the iso- 
 bar of 29.7. 9. Print HIGH and LOW in these areas. 10. Describe 
 briefly the dimensions and location of the areas of high and of low 
 pressure. 
 
 2. 1. Draw a gently curving [red] line from the center of high 
 pressure to the center of low pressure, crossing the isobars at right 
 angles. 2. Why may this line be called a line of pressure decrease, 
 or of pressure gradient, or of barometric, gradient ? 3. What is the 
 distance in miles between the centers of high and low pressure ? 
 4. How much decrease of pressure occurs along the line ? 5. What 
 is the average decrease of pressure in 100 mi. ? 6. In what part of 
 the map, with respect to the centers of high and low pressure, is 
 the pressure decrease gradual (or barometric gradient weak) ? 
 is the pressure decrease rapid (or barometric gradient strong) ? 
 How can you tell ? 7. Draw several other lines of barometric 
 gradient outward from the center of high pressure ; inward toward 
 the center of low pressure. 8. Are the barometric gradients rela- 
 tively strong or weak in the area of high pressure ? in the area of 
 low pressure ? 9. What is the general velocity of the wind in the 
 area of low pressure ? 10. What strength of wind is indicated 
 about the center of high pressure near the isobar of 30.4 ? near 
 the isobar of 30.3 ? 11. What general relation seems to obtain 
 between strength of barometric gradient and velocity of wind ? 
 12. What (apparent) exception to this rule is indicated within the 
 isobar of 29.4 ? 
 
WEATHER MAPS 131 
 
 3. 1. Draw several light [blue] curved lines prolonging the wind 
 arrows in 33 1, so as to indicate the general flow of the winds, espe- 
 cially about the areas of high and of low pressure. 2. Do the winds 
 blow directly outward from the center of high pressure ? directly 
 inward toward the center of low pressure ? 3. Turn the Atlas, so 
 as to look along one of the barometric gradient lines, in the direc- 
 tion of pressure decrease. Do the winds near this line blow par- 
 allel to it, to the right of it, or to the left of it? 4. Test the 
 answer to the previous question in several other parts of 33 1. 
 5. Make a general rule stating the relation of direction of wind to 
 direction of barometric gradient ; another stating the relation of 
 strength of wind to strength of barometric gradient. NOTE : The 
 winds in the area of high pressure may be described as "blow- 
 ing gently along outflowing clockwise spirals." (Clockwise means 
 " turning in the same direction as the hands of a clock " ; counter- 
 clockwise means "turning in the opposite direction.") 6. Make a 
 similar statement for the winds in the area of low pressure. 
 
 4. NOTE : A set of observations made a day (24 hours) later 
 than those in 33 1 is given in 332. 1. Prolong the wind arrows in 
 light [bine] curved lines in different parts of 332. -Draw similar 
 lines in intermediate spaces. 2. What indication do these curved 
 wind lines give of the occurrence of an area of low pressure ? of 
 an area of high pressure ? 3. Complete in 33 2 the large oval isobar 
 of 29.8, parts of which are printed in broken lines. 4. Complete 
 the smaller oval isobar of 29.5. 5. Draw intermediate isobars for 
 29.6, 29.7 ; draw the isobar of 29.4 (about as far inside of 29.5 as 
 29.6 is outside of it). 6. Is there room for an isobar of 29.3 ? If so, 
 draw it. 7. Shade lightly [blue] the area of low pressure, inside of 
 the isobar of 29.7. Print C' in the center of low pressure, and LOW 
 across the area of low pressure. 8. Complete the isobars for 30.1, 
 30.4. Draw isobars for 29.9, 30.0, 30.2, 30.3. 9. In what state 
 do you think an area of high pressure may have its center (out- 
 side of border of 33 2)? 10. Test in 33 2 the rules made in 3, ques- 
 tion 5, regarding the relations of wind and barometric gradient. 
 
132 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 11. Draw a line inclosing all the stations where rainfall (rain or 
 snow) is indicated in a3 2. In what states is rainfall indicated ? 
 (The rainfall dots should be somewhat larger inside the isobar of 
 29.6.) 12. What is the general position of the rainfall area with 
 respect to the center of low pressure ? 13. What general direc- 
 tions have the winds in the rainfall area? 14. Draw a line sepa- 
 rating the region where the sky is clear from that in which it is 
 cloudy or rainy. What is the general position of the clear region 
 with respect to the center of low pressure ? 15. In what general 
 directions are the winds blowing in the clear region ? 16. In what 
 part of 33 2 may the weather be described as stormy ? 
 
 5. 1. Examine the isotherms (fine dotted lines) in 332. What 
 season do you think this weather map represents ? 2. In what 
 states may snow be falling ? (DE, 70.2 ; DP, 45.5 ; G, 231.2 ; T, 
 249.6.) 3. Draw in light dotted [blue] lines the isotherms for every 
 ten degrees, spacing them proportionately between and outside of 
 the printed isotherms. (The isotherms of 80 should appear only 
 in a small SE. corner of the map.) Print their values in small 
 figures at their ends. 4. How much difference of temperature is 
 there between places in the NW. and the SE. parts of the map ? 
 
 5. Draw a [blue] dotted temperature gradient line across the map. 
 
 6. What is the' average decrease of temperature in 100 mi. ? 7. In 
 what states is the temperature gradient strongest ? What is the 
 temperature decrease in 100 mi. in that part of the map ? 8. What 
 is the general direction of the winds in 33 2 where temperatures are 
 above 40 ? below 20 ? 9. What relation seems to obtain between 
 wind direction and temperature ? 10. Prolong the southerly wind 
 arrows backward, outside of the map. From what region do they 
 come? 11. Answer the same question for the northerly winds. 
 
 12. How can you account for the unlike temperatures of these 
 winds ? (Examine 31 1.) 13. Now explain why the strongest tem- 
 perature gradients occur in a certain part of 33 2. 
 
 6. 1. On which side of the center of low pressure in 33 1 would 
 you expect relatively warm, cloudy, and wet weather ? cold, clear, 
 
WEATHER MAPS 133 
 
 and dry weather ? 2. Mark C in 33 2 to show the location of the 
 center of low pressure in 33 1. Draw a broken line in 33 2 connect- 
 ing C and C'. 3. Why may this line be called the track of the 
 low-pressure center, or the storm track ? Prolong the track to the 
 WSW. and ENE. 4. In what direction has the center of low pres- 
 sure moved ? How far has it moved in a day (24 hours) ? How far, 
 on the average, in an hour? 5. Draw in 33 1 a rainfall area some- 
 what smaller than that of 33 2, but in about the same position with 
 respect to the center of low pressure. Mark some rainfall dots in 
 this area (larger near C, smaller farther away). 6. Mark some 
 clear-weather signs E. of the isobar of 30.0. 7. Draw a light [blue] 
 dotted isotherm of 30 running NE.-SW. through the center of low 
 pressure in 33 1 ; curve it to E. across S. Lake Michigan ; SE. across 
 Ohio and Virginia. Draw isotherms of 70 and at about the same 
 distances from the isotherm of 30 as they are in 33 2. 8. Describe 
 the weather of SW. Missouri in 33 1 ; in 33 2. 9. How has the 
 weather there changed in 24 hours, as to temperature ? pressure? 
 wind ? sky ? rainfall ? 10. How are these changes related to the 
 movement of the low-pressure area? 11. Describe the weather 
 of SW. Pennsylvania in 33 1; in 332. 12. How has the weather 
 there changed in 24 hours as to temperature ? pressure ? wind ? 
 sky ? rainfall ? 13. How are these changes related to the move- 
 ment of the low-pressure area ? 14. Mark a cross on the track of 
 the low-pressure center, midway between its positions on the first 
 and second days. How has the weather changed at this cross in 
 24 hours ? 15. Is high pressure or low pressure associated with 
 fair weather ? with stormy weather ? 
 
 7. [1. Draw two lines parallel to the track of the low-pressure 
 center ; one about 200 mi. to the N., the other as far to the S. 
 Mark crosses on these lines opposite the cross at the midway point 
 of the track. 2. Determine the changes of wind direction at these 
 two crosses during the 24 hours from 33 1 to 33 2. 3. Compare these 
 wind changes with those occurring at the cross on the track. NOTE : 
 When the wind changes or shifts from E. through SE., S., SW., W., 
 
 '/ i 
 
134 EXERCISES IX PHYSICAL GEOGRAPHY 
 
 to NW., it is said to veer; when it shifts from E. through ISTE., N., 
 to NW., it is said to luck. 4. At which cross in 33 2 does the wind 
 veer, as the low-pressure center passes eastward ? At which cross 
 does the wind back ? 5. Where in the area of low pressure, 33 2, is 
 the air calm ? G. Where is a similar calm space indicated in 33 1 ? 
 NOTE : It happens not infrequently that a space of about 100 mi. 
 diameter at the center of low pressure, or storm center, has light 
 winds or calm air, and that the rainfall ceases there and the clouds 
 break; hence this space has been .called the eye of the storm. 7. In 
 what direction and with what velocity is the wind blowing about 
 70 mi. E. of the storm center in 33 1 or 33 2 ? N. of the center ? 
 W. of the center ? S. of the center ? 8. With these facts in mind, 
 correct, if necessary, your answer to question 14, 6, as to the 
 change in the winds as the storm center passes by.] 
 
 8. 1. Draw additional wind arrows in the E. part of 33 3, bearing 
 in mind the rules made in answer to question 5, 3. 2. Shade 
 lightly [red] the area of (moderately) high pressure within the 
 isobar of 30.1, and [blue] the area of low pressure within the isobar 
 of 29.7. 3. In what state do you think the center of low pressure 
 would be found ? 4. Mark C" to represent the center (near edge of 
 the Atlas page). Estimate the pressure at C". 5. Print C and C' 
 in 33 3 in the positions they had in 33 1 and 33 2. Connect C, C', C",. 
 by a storm-track line. 6. What is the direction of the storm track 
 on the second day ? 7. How far has the storm center moved on the 
 second day ? 8. What is its average hourly velocity for the second 
 day ? for the two days ? 9. Compare the size of the area of low 
 pressure (within isotherm of 29.7) and the pressure at the center on 
 the three days. 10. How has this area of low pressure changed as 
 it moved EN"E. ? 11. Do you think the area of high pressure in 33 3 
 represents a new position of the high-pressure area on 33 1, or of 
 the high-pressure area inferred to stand NW. of 33 2 ? Why ? 12. 
 What features, already learned regarding the high-pressure area in 
 33 1, are again illustrated by the high-pressure area of 33 3, as to bar- 
 ometric gradients (direction and strength) ? as to winds (direction, 
 
WEATHER MAPS 135 
 
 strength, and general movement) ? state of sky ? 13. All these 
 features of a high-pressure area, taken together, are given the name 
 anticyclone. Print ANTICYCLONE across the area of high pressure 
 in 333. 14. Compare the position of the isotherm of in 33 1, 2, 3. 
 How is its change of position related to the direction of the winds ? 
 to the movement of the center of low pressure ? NOTE : A fall of 
 temperature of 20 or more in 24 hours to a value below freezing 
 (32), accompanied by brisk or strong NW. winds, is called a cold 
 wave. 15. In (about) what part of 332 is a cold wave occurring? 
 In what part of :u 3 ? of 33 1 ? How can you tell ? 16. In what 
 direction does a cold wave advance over the central and eastern 
 United States ? 
 
 9. NOTE : The weather conditions of 33 4 are for the fifth day in 
 this series of observations (the fourth day is not here mapped). 
 1. Draw a number of wind arrows of appropriate direction and 
 length in 334. 2. In what direction and how far has the anti- 
 cyclone of 33 3 moved in the interval between 33 3 and 4 ? 3. What 
 is its average hourly velocity ? 4. Do you think the area of low 
 pressure on 33 4 corresponds with the one on the other maps ? 5. 
 What indications are found in 33 3 that a new area of low pres- 
 sure is approaching ? From what direction is it probably coming ? 
 6. What features already learned regarding low-pressure areas in 
 33 1 and 2 are again illustrated in 334, as to barometric gradients ? 
 as to winds ? as to state of sky ? 7. All these features of a low- 
 pressure area, taken together, are frequently given the name 
 cyclonic area or cyclone. Print CYCLONE in its proper position 
 in 334. 
 
 10. 1. Compare the position of the isotherm of 30 in 33 3 and 4. 
 How is its change of position related to the direction of the winds ? 
 to the movement of the center of low pressure ? 2. Why may the 
 change thus illustrated be called a warm wave ? 3. In what states 
 was a warm wave taking place in 33 1 ? in 33 2 ? 4. Where may two 
 warm waves be supposed to be taking place in connection with 33 3 ? 
 5. Where may a cold wave be inferred in 33 4 ? 6. Draw a cyclonic 
 
136 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 track ENE. from the cyclonic center in 33 4. 7. Supposing that the 
 progress of this cyclone is at about the same rate as that of 33 1, 2, 
 indicate in 33 4 the position of the cyclonic center on the sixth day. 
 8. What sort of weather (temperature, pressure, wind, sky) is indi- 
 cated for Chicago in 33 4 ? 9. What sort of weather will occur 
 probably at Chicago on the following day ? 10. What sort of weather 
 is indicated for Buffalo on 334? 11. What sort of weather will 
 probably occur at Buffalo one day later than 33 4 ? two days later ? 
 [12. In what part of 33 4 will the winds veer as the cyclonic area 
 moves eastward ? 13. Will veering or backing winds be more com- 
 mon in the United States in connection with this cyclonic storm ?] 
 11. NOTE : Cyclonic storms of the kind here described occur 
 chiefly in the belts of westerly winds, and are relatively rare in 
 the trade-wind belts ; they are more violent at sea than on land, 
 and in winter than in summer. 1. Are cyclonic weather changes 
 more common in Africa or in N. America ? in S. America or in 
 Asia? Why? 2. In what month would cyclones and anticy- 
 clones control the weather of the N. coast of Africa ? that of the S. 
 coast ? 3. What sort of weather would probably be encountered by 
 a vessel rounding Cape Horn (see Plate 42) in January ? in July ? 
 
 4. In what season would the change of temperature due to the pas- 
 sage of a cyclonic storm in the E. United States be greatest? 
 Why ? 5. Would the change of temperature due to the passage of 
 a cyclonic storm in January be greater in the E. United States or in 
 
 5. Europe ? Why ? 6. Why can weather predictions be made more 
 accurately for the E. United States than for W. Europe ? 7. In 32 1 
 represent by [blue] wind arrows a cyclonic storm of appropriate 
 size (see 33 2) in the N". Atlantic. (Place the center of low pres- 
 sure near 50 N. lat., 40 W. long.) 8. In 32 2 draw a similar cyclonic 
 storm in the S. Atlantic (on the same meridian but in 50 S. lat.). 
 NOTE : Cyclonic winds turn clockwise in the S. hemisphere. 9. 
 Draw in 32 2 an anticyclone of appropriate area (see 33 3) in the 
 N". Pacific (center of high pressure in 45 N. lat., 180 long.). 10. 
 Draw a similar anticyclone in 32 1 in the S. Pacific (on the same 
 
WEATHER MAPS 137 
 
 meridian but in 45 S. lat.). NOTE : The winds of anticyclones in 
 the S. hemisphere blow outward, in counter-clockwise spirals. 11. 
 What would be the direction of a warm inflowing wind in a cyclone 
 in the S. hemisphere ? of a cold inflowing wind ? [12. What Avould 
 be the succession of wind directions noted by an observer on the 
 track of a cyclone in the S. hemisphere ? on the equatorial side 
 of the track ? on the S. polar side of the track ? 13. When one 
 observer has cloudy and wet weather in a cyclonic area, what sort 
 of weather will be noted by another observer who is under a neigh- 
 boring anticyclone ? 14. As the phases of the moon are the same 
 for both these observers, what does your answer to the preceding 
 question suggest as to the control of weather by the moon ?] 
 
 12. Define : 1, isobaric line, isobar ; 2, line of pressure de- 
 crease, pressure gradient, barometric gradient ; 3, clockwise, 
 counter-clockwise ; 6, storm track ; 7, veer, back, storm center, 
 eye of the storm ; 8, anticyclone, cold wave ; 9, cyclonic area, 
 cyclone ; 10, warm wave. 
 
EXERCISE XIII. OCEAN CURRENTS 
 
 OBJECT. To learn the general system of ocean currents, the causes 
 to which they are due, and their effects in modifying the distribution of 
 atmospheric temperatures. 
 
 Preliminary. The surface waters in the greater part of the oceans, 
 to a depth of several hundred feet, are in slow movement at a rate 
 of from 10 to 20 or 30, occasionally 60 or 80, (nautical) miles a day. 
 The moving waters are called currents; but where a current is 
 narrow, deep, and rapid it is called a stream; where it is broad, 
 shallow, and slow it is called a drift. The prevailing direction of 
 ocean currents has been determined in many parts of the world by 
 the movement of floating objects, such as the wrecks of vessels, and 
 in various other ways. The direction of currents is stated in terms 
 of the point of the compass toward which they flow, as northward, 
 southeastward, etc. The currents as charted in Plate 34 are rep- 
 resented in simplified form, without the irregularities that might 
 be shown on a chart of larger scale. For the purposes of this exer- 
 cise the " polar oceans " will be taken to extend to latitude 55 N. 
 and S., and the other oceans will be sometimes spoken of as " non- 
 polar oceans." Distances in the nonpolar oceans on the charts here 
 referred to may be roughly measured by noting that 40 latitude 
 degrees equal 2400 nautical miles. This exercise uses Plate 34. 
 
 1. 1. What is the general direction of the ocean currents in 
 latitude 40 or 50 N. or S. ? of the currents near the equator or 
 the equatorial currents? (Do not consider for the present the 
 currents shown by waving lines near the equator.) 2. What is the 
 general direction of the currents near the eastern side of the non- 
 polar oceans ? near the western side ? (Use equatorward and pole- 
 ward, instead of northward and southward, in answering this 
 
 138 
 
OCEAN CURRENTS 139 
 
 question.) 3. Describe the general motion of the currents, when 
 taken together, in each N. nonpolar ocean ; in each S. nonpolar 
 ocean. (Omit the N. part of the Indian ocean for the present.) 4. 
 If you visited the central part of a nonpolar ocean and could see 
 the currents moving around you, in which oceans would they turn 
 clockwise (with the hands of a clock)? in which counter-clockwise? 
 [5. If you stood at the N. pole and could see the earth turning in 
 its daily rotation, would it appear to turn clockwise or the other 
 way ? 6. How would it appear to turn if you stood at the S. pole ? 
 7. Compare the turning of the earth, as seen from the N. pole, with 
 the turning of the currents in the two N. nonpolar oceans. 8. 
 Make the same comparison for the S. hemisphere.] 9. Draw in 
 the X. and S. nonpolar oceans of the ideal diagram, 342, some 
 circular lines, with arrowheads, to show the general movement of 
 currents appropriate to each ocean there mapped. In the center of 
 each ocean draw a small circle, imitating a clock face, and indicate 
 upon it direction of clockwise motion. NOTE : The general turning 
 movement of the currents in each ocean may be called eddies. [10. 
 About how long would it take a floating object to make a circuit of 
 the 1ST. Atlantic eddy ? See the velocities stated in the preliminary 
 section ; estimate length of circuit in terms of degrees of latitude, 
 and change degrees to nautical miles (60 to a degree).] 11. Should 
 the eddies be described as fast moving or as slow moving ? 
 
 2. 1. Examine the currents in 50 or 60 S. lat. in 34 1. (They 
 will be better understood if examined on a globe.) If these currents 
 were seen by an observer stationed at the S. Pole, how might he 
 describe their general movement ? [2. How does their movement 
 compare with the direction of the earth's rotation ?] 3. Why 
 may these currents taken together be called the Antarctic eddy ? 
 4. Do they seem to form a stream or a drift ? 5. How is the Ant- 
 arctic eddy related to the three eddies of the S. nonpolar oceans ? 
 6. Why is there not an Arctic eddy, corresponding in size to 
 the Antarctic eddy ? NOTE : There is believed to be a relatively 
 small Arctic eddy, flowing in a general way eastward around the 
 
140 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 Arctic ocean. 7. Draw a light pencil line around the general 
 course of the eddy in the N. Pacific ocean in 34 1. 8. Is the course 
 circular or oval ? 9. About how wide is it N.-S.? how wide E.-W. ? 
 
 10. The W. part of this eddy is called the Japanese current. Why ? 
 
 11. Describe the local currents in the NE. and NW. parts of the 
 N. Pacific, in their relation to the main eddy. 12. Draw a line 
 around the best defined eddy of the S. Pacific. What part of the 
 ocean does this eddy occupy ? 13. What are its rough dimensions 
 N.-S. ? E.-W. ? 14. The eastern part of this eddy is called the 
 Peruvian current. Why ? 15. What reasons can you suggest for 
 the occurrence of a smaller eddy in the W. part of this ocean ? 
 
 3. 1. Draw a pencil line around the eddy of the Indian ocean in 
 34 1. What are its rough dimensions ? 2. How is it connected with 
 the eddy of the Pacific ocean ? 3. How are its currents related to 
 Madagascar ? to the S. point of Africa ? 4. Draw a pencil line 
 around the S. Atlantic eddy. What are its rough dimensions ? 
 
 5. How does its shape differ from that of the Indian ocean eddy ? 
 
 6. Does it receive a branch from the Indian ocean ? 7. How does 
 its SW. part differ from the corresponding part of the S. Pacific 
 eddy ? 8. Draw a pencil line around the N. Atlantic eddy. What 
 are its rough dimensions ? 9. What islands, sea, and gulf are on 
 the SW. side of the N. Atlantic ? 10. How are the currents of 
 the N. Atlantic eddy related to these islands and seas ? 11. The 
 W. part of the N. Atlantic eddy, along the E. coast of the United 
 States, is called the Gulf stream. Why ? 12. Compare the breadth 
 of the Gulf stream with that of the currents W. of Europe. 
 13. Why may the last-named currents be appropriately called the 
 N. Atlantic drift? 14. How are the two Atlantic eddies connected ? 
 15. What influence have the outlines of the bordering continents 
 in causing the connecting current to cross the equator ? [16. Draw 
 in 34 2 a new [red] outline of the continents there shown, so that 
 the eddy of the N". ocean shall give out a cross-equator connecting 
 current to the eddy of the S. ocean ; indicate this branch by [blue] 
 arrows. In what direction does this connecting current flow ? In 
 
OCEAN CURRENTS 141 
 
 what direction does the actual connecting current flow across the 
 equator in the Atlantic ocean ?] 
 
 4. 1. Compare the currents N. of the N. Atlantic eddy with those 
 N. of the N. Pacific eddy, as to position ; as to direction ; as to 
 dimensions. 2. Which of these far-northern currents may be de- 
 scribed as an outgoing, poleward branch of the main eddy ? 
 
 3. Which may be described as wedging equatorward currents 
 between the main eddy and the neighboring continent? 4. Which 
 eddy of the S. oceans has an outgoing poleward branch ? Why does 
 it occur in this ocean and not in the others ? 5. Compare its di- 
 mensions and position with those of the outgoing branch of the 
 N. oceans. 6. Which ocean has the largest outgoing poleward 
 branch from its main eddy ? Why ? 7. How does this branch 
 seem to be connected with the eddy of the- neighboring polar 
 ocean ? 8. Which of the S. oceans receives an equatorward wedg- 
 ing current '.' 9. How is the wedging current related to S. America? 
 
 10. Why is such a current not found in the other S. oceans ? 
 
 11. Compare the breadth of open water connecting the N. Atlantic 
 and the Arctic with that connecting the N. Pacific and the Arctic. 
 
 12. What currents are indicated in 34 1 in Bering strait ? (Such 
 currents as occur there are small and unimportant in the general 
 system of ocean currents.) 13. Compare the eddies of the two polar 
 oceans as to size ; as to breadth of connection with the eddies 
 of neighboring oceans. 14. What influence has the S. end of 
 S. America on the eddies of the neighboring oceans ? Why ? 
 15. What influence has the E. point of S. America (Cape San 
 Roque) on the eddies of the Atlantic? 
 
 5. 1. Compare the general direction of the prevailing winds in 
 far S. latitudes, as shown in 32 1 and 2, with the general circulation 
 of the ocean currents in the S. polar (Antarctic) eddy. 2. Do the 
 same for the three S. oceans ; for the two N. oceans. 3. Mark 
 [blue] dots in 34 1 where the winds and currents have a general 
 agreement in direction ; mark small [red] crosses where they differ. 
 
 4. Do the winds and currents generally agree or differ in direction ? 
 
142 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 5. Which ordinarily has the greater velocity, the prevailing winds 
 or the ocean currents ? 6. What do the answers to questions 4 and 
 5 suggest as to the cause of the ocean currents ? 7. Examine the 
 small current of the Indian ocean, near the equator, for January, 
 as shown by waving lines in 34 5. Why may this current be called 
 an equatorial counter current ? 8. What is its position with respect 
 to the equator ? 9. What is the direction of the winds in the same 
 part of the ocean and in the same month ? (See 34 3.) 10. What are 
 the names of the two large N. embayments of the Indian ocean ? 
 (See Plate 44.) 11. In what month is the counter current of the 
 Indian ocean K. of the equator ? Describe its course. 12. How 
 do the winds blow in that part of the ocean at that time ? 13. How 
 do the facts just learned bear on the answer given to question 6 ? 
 
 6. [1. In what other oceans do equatorial counter currents occur ? 
 (See 34 7 and 8.) 2. Describe the counter current of the Atlantic 
 in January ; in July. 3. In which of these months are the SE. trade 
 winds extended over the greatest area K. of the equator ? (See 
 32 1 and 2.) 4. What connection appears to exist between these 
 extended trade winds and the counter current of the Atlantic ? 
 
 5. Describe the counter currents of the Pacific in January ; in July. 
 
 6. Where does the counter current in the Pacific, S. of the equator 
 in January, stand in relation to the extension of the NE. trade 
 winds S. of the equator ? 7. What are the directions of the winds 
 and currents in this part of the ocean in July? 8. Compare the 
 counter current of the Pacific N. of the equator in January and July. 
 In which month has this counter current its greatest development ? 
 9. What general relation appears to exist between the extension of 
 the trade winds across the equator, in the form of more or less 
 perfectly developed monsoon winds, and the occurrence of equa- 
 torial counter currents ? 10. In what parts of what oceans is this 
 relation found ? in what months ?] 
 
 7. 1. On which side of the various current eddies, E. or W., would 
 you expect to find relatively cool water ? relatively warm water ? 
 Why ? 2. Mark broken [or blue] arrows on the cool currents ; 
 
OCEAN CURRENTS 143 
 
 full-line [or red] arrows on the warm currents. 3. On which side, 
 E. or W., of the torrid oceans should the equatorial currents have 
 the highest temperature ? 4. Mark [red] arrows along the equato- 
 rial currents in that half of their course. NOTE : The mean annual 
 temperature of the ocean surface is shown by dotted isotherms 
 in 34 1. 5. Shade [red] the area over 80 and [blue] under 40. 
 6. Why do the isotherms of 70 turn towards the equator in the 
 N. and in the S. Atlantic ? in the N. and the S. Pacific ? 7. Why 
 is the 80 isotherm in the torrid Pacific limited to its W. part? 
 8. Why is the 40 isotherm deflected to an oblique course in the 
 N. Pacific ? 9. Why is the deflection of the 40 isotherm stronger 
 in the N. Atlantic than in the N. Pacific ? 
 
 8. 1. Examine the mean annual temperatures of the lower atmos- 
 phere in 30 2. Why are the isotherms of 80 nearer together on the 
 E. side than on the W. side of the torrid Atlantic ? ' 2. On which 
 side (E. or W.) of the nonpolar oceans are the isotherms of 70 
 deflected equatorward ? Why ? 3. Where is the deflection greatest ? 
 Why ? 4. Why is the 40 isotherm deflected to an oblique course 
 over the N. Pacific ? 5. Why is the deflection of this isotherm 
 greatest in the N. Atlantic ? 6. Over what ocean is the 30 isotherm 
 deflected to the greatest distance from the equator ? Why ? 7. Why 
 is there no corresponding deflection of the 30 isotherm over the 
 S. Atlantic ? 8. Why are the isotherms of 40 and 70 closer to- 
 gether on the W. side of the N. Pacific and N. Atlantic than on 
 the E. side of these oceans ? 9. Why are the corresponding iso- 
 therms over the Indian ocean so nearly parallel, instead of divergent, 
 as over the 1ST. oceans ? NOTE: The annual change of temperature 
 in the ocean surface is much less than in the atmosphere. 10. On 
 which side (E. or W.) of the N. continents is the annual range of 
 atmospheric temperature smallest? (See 30 3.) Why ? 
 
 9. 1. Examine 31 1. Why does the January isotherm of 20 
 occur N. of Norway in the same latitude as that of 30, N. of 
 Alaska? 2. Why is the January temperature gradient in Alaska 
 so much stronger than in Norway ? 3. Suppose a sailing vessel 
 
144 EXERCISES IX PHYSICAL GEOGRAPHY 
 
 from a X. Atlantic port is bound for an Australian port ; describe 
 its course, so that it may take best advantage of winds and currents 
 S. of lat. 30 S. Explain. 4. In what months might small sailing 
 vessels most easily make the voyage from India to equatorial 
 Africa ? the return voyage ? Why ? 5. If a sailing vessel made a 
 voyage from San Francisco to Japan and back, on which trip should 
 it follow a more northern course ? Why ? [6. If a sailing vessel, 
 bound from New York to Buenos Aires (see Plate 42), attempted to 
 cross the equator N". of Cape San Koque, what sort of winds might 
 it find on the heat equator ? 7. How might the vessel be drifted 
 by the currents in that part of the ocean ? 8. Would it thus be 
 helped or hindered on its voyage ? 9. Where should the equator be 
 crossed by such a vessel ?] 
 
 10. Define : Preliminary , currents, stream, drift ; 1, equato- 
 rial current, clockwise, counter-clockwise, eddy ; 3, Gulf stream, 
 N. Atlantic drift ; 5, equatorial counter current. 
 
INDEX 
 
 Africa, 33, 85, 116, 123- 
 
 125, 127, 144 
 aggradation, 10, 52 
 Alabama, 42 
 Alaska, 143 
 Algeria, 126 
 
 Allegheny mountains, 93 
 Allegheny plateau, 42, 43 
 alluvial deposits, 36, 50, 
 
 52 
 alluvial fans, 36, 52, 54, 
 
 59, 61 
 
 Alps, 56, 57 
 America. See North 
 
 America and South 
 
 America 
 amphitheater, 61 
 Andes, 124 
 
 Antarctic ocean, 139, 141 
 Antarctic regions, 116 
 anticyclone, 135-137 
 Arctic ocean, 139, 140 
 Arctic regions, 116 
 Ardennes, 51 
 areas of high and low 
 
 pressure, 130-137 
 Arizona, 35, 68, 128 
 Arkansas river, 54 
 artesian wells, 22 
 Asia, 55, 60, 116, 117, 
 
 122, 127 
 Atlantic ocean, 117, 121, 
 
 123,139,140,141,143 
 Australia, 116, 124, 126, 
 
 127, 144 
 
 Bar, 111 
 barometer, 129 
 barometric gradient, 130, 
 
 131 
 barrier beach, 100, 104 
 
 baselevel, 5, 19, 41, 45, 
 
 63, 107 
 local, 6, 82 
 
 basin, 50, 59 
 interior, 10 
 
 beach, 100, 106-108, 134 
 
 belt, subequatorial, 125 
 subtropical, 125, 126 
 trade-wind, 122, 123 
 westerly wind, 122, 123 
 
 Berea, 22 
 
 Bering strait, 141 
 
 Black mountains, 61 
 
 Blue ridge, 85, 94 
 
 Bogota, 126 
 
 Boothbay, 98 
 
 Borneo, 124 
 
 bowlders, 6, 36 
 
 Brazil, 126 
 
 Buenos Aires, 144 
 
 butte, 41 
 
 Caldera, 74, 75 
 California, 48, 50, 51, 54, 
 
 59, 68, 70, 76, 106, 
 
 124, 126 
 calms, 122, 124 
 Canada, 78 
 Cantal, 73 
 
 canyons, 29-44, 49, 107 
 Cape San Roque, 141, 144 
 Cape Town, 126 
 capture, river, 88-92 
 cascade, 21 
 
 Cascade mountains, 56 
 cave, 34, 35, 99 
 Central America, 70, 123, 
 
 124 
 
 Ce"vennes, 56 
 chasm, 99 
 Cheat river, 44 
 145 
 
 Chile, 126 
 China, 53, 127 
 cliff, 29, 34, 76, 107 
 cliff dwelling, 35 
 cliff maker, 32 
 cliffs, recession of, 31 
 
 retreat of, 31 
 
 sea, 98-113. 
 
 elevated sea, 119 
 clockwise, 131, 136, 139 
 coast, 9, 96-114, 124 
 
 embayed, 97 
 
 coastal plain, 13-17, 18- 
 28, 109-112 
 
 lacustrine, 22, 113 
 cold wave, 135 
 Colorado, 35, 41-43, 49, 
 54, 59, 74, 76, 77, 128 
 Colorado river, 35 
 contour, 13, 40, 97 
 contour line, 13 
 contour interval, 13 
 counter-clockwise, 131, 
 
 137, 139 
 
 counter currents, 142 
 country rock, 76 
 cove, 99 
 crater, 66, 74 
 Crater lake, 76 
 crest line, 56 
 Cuba, 109 
 currents, 111, 138-144 
 
 equatorial, 138 
 
 tidal, 101, 111 
 cycle of erosion, 8, 9, 46, 
 64, 65, 79, 87, 95, 97, 
 113 
 
 cyclone, 135-137 
 cyclonic areo,, 135 
 
 Deception island, 76 
 
146 
 
 EXERCISES IN PHYSICAL GEOGRAPHY 
 
 degradation, 5, 52 
 
 flood plain, 18, 45, 62, 
 
 January temperatures, 
 
 delta, 6, 102, 103, 106, 
 
 63 
 
 117-120 
 
 111, 112 
 
 formation, 30, 32, 82 
 
 January winds, 121-128 
 
 deposition, 6 
 
 fossils, 14, 30 
 
 Japan, 70, 144 
 
 depression of land, 109, 1 13 
 
 France, 51, 55-57, 73 
 
 Japanese current, 140 
 
 desert, 124, 128 
 
 Fujiyama, 70 
 
 Jhelam river, 60 
 
 dike, 71, 78 
 
 
 Jorullo, 68, 75 
 
 dissection, 26, 39, 70, 75 
 
 Georgia, 65 
 
 July temperatures, 117- 
 
 diversion, 90 
 
 Germany, 63 
 
 120 
 
 divide, -4, 26, 40, 51, 55, 
 
 Golden Gate, 106 
 
 July winds, 121-128 
 
 63, 64, 89, 92 
 
 gorge, 49, 53, 54, 58, 69, 
 
 junction of rivers, 4 
 
 creeping, 91 
 
 70, 82, 107 
 
 accordant, 4, 53, 58 
 
 definite, 55, 89 
 
 grade, 20, 60, 62, 84 
 
 hanging, 4, 53, 58 
 
 indefinite, 55, 89 
 
 gradient, pressure, 130 
 
 
 leaping, 91 
 
 temperature, 116 
 
 Kanawha river, 44 
 
 longitudinal, 94 
 
 gravel, 6, 76 
 
 Kashmir, 60 
 
 doldrums, 123, 125 
 
 gravel reef, 100 
 
 Kentucky, 42 
 
 drainage area, 92 
 
 Greenland, 120 
 
 
 drift, 138, 140 
 
 Gulf of Mexico, 121 
 
 Labrador, 120 
 
 
 Gulf stream, 140 
 
 lacustrine coastal plain, 
 
 Eddies, 139-142 
 
 gulley, 24 
 
 22, 113 
 
 Elands river, 85 
 
 
 lagoon, 101,103-105, 110- 
 
 elbow of capture, 91, 92 
 
 Hachures, 10, 40, 97 
 
 113 
 
 elevation of land, 109, 
 
 hanging valley, 4, 53, 58 
 
 lake, 10, 50, 56, 58, 67- 
 
 112, 113 
 
 harbor, 105, 106, 113 
 
 70, 81, 83, 86, 104 
 
 Enchanted Mesa, 44 
 
 Harpers Ferry, 85 
 
 landslide, 56, 58, 102 
 
 equatorial current, 138 
 
 Hawaii, 124 
 
 lava cascade, 68 
 
 equatorial counter cur- 
 
 headland, 96, 97, 104, 105 
 
 lava flows, 66-79 
 
 rent, 142 
 
 heat equator, 117-119, 
 
 leeward, 121 
 
 equatorward, 138 
 
 125-127 
 
 load of rivers, 9, 31, 61 
 
 Erie, lake, 16, 22, 113 
 
 high-pressure area, 130, 
 
 lobe of flood plain, 62 
 
 erosion, 5 
 
 131, 134 
 
 lowland, 95, 96 
 
 headward, 25, 77, 89 
 
 hill, 6, 8, 96, 108 
 
 low-pressure area, 130-1 37 
 
 lateral, 62 
 
 Himalayas, 60, 128 
 
 
 marine, 9, 98-113 
 
 horse latitudes, 123 
 
 Madagascar, 140 
 
 retrogressive, 25, 77, 89 
 
 hurricane delta, 111 
 
 Maine, 98 
 
 revived, 54, 82 
 
 Hwang-Ho, 52 
 
 malpais, 71 
 
 river, 5, 20, 80-87, 88- 
 
 
 map, 10 
 
 95 
 
 Idaho, 73 
 
 marsh, 101 
 
 Europe, 116, 123 
 
 India, 60, 127, 144 
 
 Maryland, 28 
 
 eye of a storm, 134 
 
 Indian ocean, 126, 128, 
 
 meander, 43, 61, 62 
 
 
 140, 142, 143 
 
 meander belt, 62 
 
 Fall line, 21, 112, 113 
 
 inlet, 101, 111 
 
 mesa, 41, 76 
 
 fall of a plain, 14 
 
 interfluve, 45, 46 
 
 Mesa de Maya, 76 
 
 of a river, 5, 32,45, 81, 
 
 island, 96 
 
 Meuse river, 51 
 
 111 
 
 land-tied, 103-105 
 
 Mexico, 68, 71, 123, 124 
 
 fall maker, 32, 82, 84, 85 
 
 isobar, 130, 132, 133 
 
 migrati on of divides, 90, 9 1 
 
 falls, 31, 33, 34, 80-87, 91 
 
 isotherm, 115, 129, 132, 
 
 of heat equator, 117-119 
 
 recession of, 31 , 76, 85 
 
 133, 143 
 
 Mississippi river, 23 
 
 retreat of, 31, 85 
 
 isthmus, 96, 97, 113 
 
 monadnock, 64 
 
 fan, 36, 52, 54, 59, 61 
 
 Italy, 67, 75 
 
 monsoons, 126, 127 
 
INDEX 
 
 147 
 
 Montana, 56 
 Monte Nuovo, 67 
 Morocco, 126 
 Mosel river, 63 
 mountains, 1-12, 45-65, 
 96, 124 
 
 flat-topped, 55, 57 
 
 subdued, 61 
 Mt. Shasta, 68, 70 
 Mt. Taylor, 76 
 mud flats, 105, 106 
 
 Neck, 67, 75-78 
 
 Nevada, 124 
 
 New Jersey, 113 
 
 New Mexico, 35, 44, 76, 
 
 128 
 
 Nicaragua, lake, 70 
 Nile, 125 
 North America, 116, 117, 
 
 123 
 
 North Carolina, 27, 28, 61 
 Norway, 120, 143 
 
 Ocean. See Atlantic, etc. 
 
 ocean currents, 111, 
 
 138-144 
 oceans, 138 
 
 nonpolar, 138 
 
 polar, 138 
 offset reef, 111 
 Ohio, 16, 22 
 Ohio river, 43, 113 
 oldland, 15, 21, 22, 24 
 Oregon, 16, 73, 75, 124 
 outcrop, 21, 29, 32 
 outlet, 67, 69, 81, 89 
 outlier, 39 
 
 Pacific ocean, 73, 117, 
 122, 123, 128, 140, 143 
 
 pass, 56 
 
 Patagonia, 124 
 
 peak, 4, 60, 75 
 
 peneplain, 8, 41, 63, 64, 65 
 
 peninsula, 96, 97, 103, 105 
 
 Pennsylvania, 63, 84; 93, 
 94 
 
 Pern, 124 
 
 piedmont deposits, 59 
 
 pipe, 67, 72 
 
 plain, basin, 50 
 
 coastal, 13-17, 18-28, 
 109-112 
 
 dissected, 26 
 
 lacustrine, 16, 22 
 plateaus, 29-44 
 platform, 35 
 poleward, 138 
 Potomac river, 85, 94 
 pressure gradient, 130 
 
 of atmosphere, 129 
 prevailing winds, 121-128 
 profile, 5, 14, 32, 34, 47, 
 
 49, 58, 83, 94, 99 
 Purgatoire river, 42 
 
 Railroad, 76 
 
 rainfall, 123, 124, 126, 
 
 132 
 range of mountains, 2 
 
 of temperature, 120 
 
 of tides, 99 
 rapids, 21, 31, 80, 87 
 Raton mesa, 76 
 ravine, 24, 70 
 reach, 82, 84, 86 
 recession of cliffs, 31, 76, 
 85, 112 
 
 of falls, 31, 76, 85 
 reef, 96, 97, 100-103, 1HT, 
 
 111, 113 
 relief, 9, 45 
 
 retreat of cliffs, 31, 76, 85, 
 112 
 
 of falls, 31, 76, 85 
 ridge, 4, 55, 57, 69, 60, 
 
 88-95 
 rill, 6 
 river, antecedent, 50, 81 
 
 beheaded, 61, 95, 106 
 
 betrunked, 106 
 
 braided, 53 
 
 captured, 88-92 
 
 consequent, 19, 109 
 
 dismembered, 97 
 
 engrafted, 109 
 
 extended, 109 
 
 graded, 20 
 
 insequent, 25 
 
 longitudinal, 92 
 
 mature, 8, 26, 37, 87 
 
 river, meanders, 43 
 
 misfit, 92 
 
 old, 8, 87 
 
 rejuvenated, 8, 48 
 
 revived, 8, 48, 113 
 
 subsequent, 92 
 
 tidal, 104 
 
 transverse, 92 
 
 young, 8, 37, 87 
 river basin, 4 
 river flood plain, 18, 45, 
 
 62,63 
 
 river junctions, 4, 53, 58 
 river mouth, 5, 106, 107 
 river system, 4 
 rivulet, 24 
 
 rock bench, 98-102, 108 
 rock waste, 6, 58, 100 
 Rocky mountains, 49, 54, 
 
 56, 59, 76 
 Rocky river, 22 
 
 Sacramento river, 51 
 San Antonio mountains, 
 
 69 
 
 sand, 6, 110 
 sand reef, 100, 106 
 sapping, 76, 77 
 scale of maps, 11, 97 
 Scotland, 16, 78 
 scroll, 62 
 sculpture of mountains, 
 
 57 
 
 sea cliff, 9, 98-113 
 section, 34 
 Shasta, Mt., 68, 70 
 Shenandoah river, 94 
 shifting divides, 90 
 shoal, 110 
 
 shore cliffs. See Sea cliffs 
 shore line, 9, 21, 96-114 
 
 embayed, 27, 97, 112 
 
 initial, 99 
 
 mature, 102, 107 
 
 of depression, 113 
 
 of elevation, 112 
 
 young, 99 
 Siberia, 64 
 Sierra Nevada, 48, 51, 54, 
 
 76 
 silt. 6 
 
148 
 
 EXERCISES IX PHYSICAL GEOGRAPHY 
 
 skerries, 99 
 
 slopes, 61 
 
 Snake river, 74 
 
 snow, 132 
 
 Society islands, 73 
 
 soil, 6, 63 
 
 South America, 116, 125, 
 
 127, 141 
 
 South Shetland islands, 75 
 Spanish peaks, 77 
 spit, 101-104, 106 
 spur, 4, 60, 61 
 stack, 99 
 storm, 100, 107, 108, 110, 
 
 132, 134, 136 
 storm center, 134 
 storm track, 133, 134 
 strait, 96, 97 
 stratum, 7, 21, 29 
 stream junctions, 4, 53, 58 
 streams, 4, 25, 30, 44, 46, 
 
 48, 138 
 
 structure, 21, 33, 40, 80 
 subdivide, 4, 46, 51, 92 
 subequatorial belt, 125 , 
 submergence, 97, 98 
 subtropical belt, 125 
 Sumatra, 124 
 summer, 118, 123 
 surf, 107 
 
 Susquehanna river, 63, 94 
 swell, 107 
 Switzerland, 57 
 
 Table mountain, 73, 76- 
 
 78 
 
 Tahiti, 73 
 talus, 31, 107, 109 
 Taylor, Mt., 76 
 
 temperature, 115, 129, 1 32, 
 
 136, 143 
 
 mean annual, 116, 143 
 temperature belts, 1 1 6 
 temperature gradient, 1 1 6, 
 
 132 
 temperature range, 120, 
 
 143 
 
 Texas, 111 
 texture of dissection, 60 
 
 of waste, 9 
 thermometer, 115 
 Tian Shan mountains, 55 
 tidal current, 111 
 tidal delta, 111 
 tidal inlet, 101, 111 
 tidal range, 99 
 tidal river, 104 
 tide. 98, 99, 101, 103, 104 
 tide marsh, 101, 103, 105, 
 
 106, 110, 111 
 torrent, 48 
 torrid belt, 116 
 trade winds, 122-127, 136 
 transportation, 6 
 Transvaal, 85 
 Trent river, 27 
 tributary, 53, 61 
 Tuolumne river, 48 
 
 Undermining;, 76 
 upland, 19, 23, 53, 54 
 uplift, 15, 41 
 upwarp, 47 
 
 Valley, 4, 7, 88-95 
 consequent, 19 
 drowned, 27,50, 97,108 
 hanging, 4, 53, 58, 107, 
 108 
 
 valley, insequent, 25 
 
 longitudinal, 88, 93 
 
 mature, 23, 26 
 
 meandering, 43 
 
 transverse, 93 
 
 young, 23,112 
 valley system, 4 
 Venezuela, 125 
 Vesuvius, 75 
 Victoria falls, 33 
 volcanoes, 66-79 
 
 dissected, 70, 73, 75 
 
 Warm wave, 135 
 
 warping:, 47, 50, 64, 81, 87 
 
 waste, 6, 31, 58, 61, 85, 
 100, 104 
 
 waterfalls. See Falls 
 
 water gap, 92 
 
 waves, 107, 108, 110 
 
 weather, 123, 129-137 
 
 weather maps, 129-237 
 
 weather elements, 129 
 
 weathering, 6, 31, 107 
 
 West Virginia, 44 
 
 westerly winds, 122-127, 
 136 
 
 Wicomico river, 28 
 
 wind belt, 122 
 
 wind gap, 92 
 
 winds, 121-128, 129-137 
 backing, 134, 136 
 trade, 122-127 
 veering, 134, 136 
 westerly, 122-1'?" 
 
 windward, 121 
 
 winter, 118, 123 
 
 Zambezi river, 33, 125 
 
UNIVERSITY OF CALIFORNIA LIBRARY 
 
 Los Angeles 
 This book is DUE on the last date stamped below. 
 
 Form L9-100m-9,'52(A3105)444 
 
 LOS 
 
!SSLSf9?!*t LIBRARY FACILITY 
 
 A 000 582 723 3 
 
 i: i 
 
 - vurORNU 
 
 S. CAUK,