oat SissSieet= tice “0681 (I10qTID Aq oJOYg) ‘sefIVjNqI1} ey} Jo ouO dn pus ooTjINS OY} SS019B SUJYOO] ‘19us109 ySBvoyyNos oY} WoT} ‘SySBlY ‘Iojoepy Inj Jo puosy Vit OP Wty >=. 7-2 eas te ae wa... a THE ICE AGE IN NORTH AMERICA AND ITS BEARINGS UPON THE ANTIQUITY OF MAN SY. G. FREDERICK WRIGHT, D.D., LL.D., res.a Late assistant on the Pennsylvania and United States Geological Surveys Author of ‘‘Logic of Christian Evidences,”’ ‘‘Greenland Ice Fields,”’ ‘‘ Asiatic Russia,” etc. peed etre? 32 ey Fifth edition with many new maps ‘pnd iliustrations, enlarged 4 and rewritten to incorporate the facts that bring i$ ap 40 date,» ee with chapters on Lake Agassiz and the, Preiysbl>> Cause’ "all Bed eae Glaciation, by Warren Upham, Sc.D., F.G.8.A.) lace Assistant?” on the Geological Surveys of New Harapshire, Minnesota, the United States, and Canada. B] ) > 2 ) ) i 532 5 52> i] > ) ey | B) OBERLIN, OHIO BIBLIOTHECA SACRA COMPANY 1911 . f B pS iow ¢ +f) LOsed BIBLIOTHECA SACRA C TO ELISHA GRAY _ CHEVALIER DE LA LEGION D’HONNEUR ” INVENTOR OF THE HARMONIC TELEGRAPH, THE TELEPHONE % AND THE TELAUTOGRAPH WHOSE INTELLIGENT INTEREST IN GLACIAL GEOLOGY AND WHOSE GENEROUS ‘APPRECIATION OF MY WORK ’ é _ HAVE BEEN A CONSTANT INSPIRATION ahs THIS VOLUME IS AFFECTIONATELY DEDICATED oe? PREFACE TO THE FIFTH EDITION. The twenty years which have elapsed since the publica- tion of the first edition have been exceedingly fruitful in glacial investigations, as will be seen by consulting the bibliog- raphy at the end of this volume. Nevertheless, as premised in the preface to the first edition, these later investigations have not seriously affected the main theories adopted twenty years ago; but “pertain mainly to the details of the subject.” In the present revision the new material added is especially abundant only upon a few subjects. Many existing glaciers have been discovered in the Rocky Mountain system in the United States and Canada—a region which was scarcely touched by explorers until the close of the last century. Explorations have also greatly extended our knowledge of Alaskan glaciers while the changes in the Muir Glacier have been so enormous as to be really startling, fully sustaining the theoretical conclusions which I had drawn from my stud- ies of the glacier in 1886. Much new material, also, has accumulated concerning the glaciers of Greenland, Central Asia, and the Antarctic Continent. As to the extent of the continental glaciers of the Pleisto- cene period, there has been little additional information since the publication of the first edition. Among the most important additions has been the rectification of the glacial boundary across New Jersey and Pennsylvania, where the “fringe,” or ‘‘attenuated border,” imperfectly apprehended by Lewis and Wright, has been carefully traced by Professor vi PREFACE TO FIFTH EDITION. E. H. Williams from the Atlantic Ocean to-Ohio and found to be from twenty to thirty miles south of their. terminal moraine. ~ The facts relating to this border, brought out by Professor Williams, have a most important bearing upon the discus- sion both of the cause and of the date of the Pleistocene glacial epoch. There has also been a great accumulation of evidence, collected pretty largely by Mr. Frank Leverett and the geolo- gists of.lowa, Minnesota, Dakota, and Canada, concerning the episodes of the Pleistocene glacial epoch, leading to the division into the Kansan, Illinoisan, Iowan, and Wisconsin periods of advance and retreat. The relative length of time occupied by these episodes is still a most interesting subject of investigation. | The question of the date of the Pleistocene glacial epochis still a subject of hot discussion, but a great accumulation of facts, relating to post-glacial erosion and sedimentation, are rapidly establishing a very moderate glacial chronology. Likewise a great accumulation of facts is limiting the the- ories concerning the cause of glaciation to changes in land elevation and in the direction of oceanic currents. The chap- ters upon the date and the cause of the epoch have been greatly enlarged and rewritten. The final chapters upon the discovery of human relics in deposits connected with the Glacial epoch in North America have also been thoroughly revised and enlarged, to take into consideration the more recent discoveries of facts bearing both for and against man’s existence here in glacial times. G. FREDERICK WRIGHT. OBERLIN, OuI0, December 22, 1910. PREFACE TO FIRST EDITION, Tue present treatise is the outcome of special studies upon glacial phenomena begun in the summer of 1874, in the eastern part of Massachusetts, the results of which were published in a communication to the Boston Society of Natural History in December, 1876. These first studies pertained to the origin of the gravel-ridges described in this volume under the name of “kames.” Fortunately, in the preparation of that paper, I was favored with an interview with Mr. Clarence King, who then gave me the information referred to in the following pages, concerning the terminal moraine south of New England, which has been so fruitful of suggestion to other investigators as well as to myself. Since that time the subject has never been out of mind, and my summer months have all been devoted, under favorable conditions, to the collection of field notes regarding it, and so it has seemed to others, as well as to myself, appropriate that I should endeavor to tring the facts within the reach of the general public. After having become, during the four following sea- sons, familiar with the glacial phenomena over the larger part of New England, I was invited by Professor Lesley to survey, in company with the late Professor H. Carvill Lewis, the boundary of the glaciated area across Pennsyl- vill PREFACE TO FIRST EDITION, vania (our report constitutes Vol. Z of the Second Geologi- cal Survey of that State). The summers of 1882 and 1883 were spent under the auspices of the Western Reserve His- torical Society of Cleveland, Ohio (whose secretary, Judge C. C. Baldwin, had the sagacity to recognize, at that eariy time in the investigations, the historical bearing of the work), in continuing the survey across Ohio, Kentucky, and Indiana (see my report to that society, 1884, and an article in the “ American Journal of Science,” July, 1883). Dur- ing the summers of 1884 and 1885 I was employed, as a member of the United States Geological Survey, in tracing the boundary across IJlinois, and in reviewing the field in Ohio and western Pennsylvania. The report of this work has not yet been made public, but permission to use the facts has been generously granted by the director of the survey, Major J. W. Powell. The summer of 1886 was spent in Washington Territory, and upon the Muir Glacier in Alaska. The two following ‘seasons were occupied in further exploration of Ohio, Dakota, and other portions of the Northwest. Thus I have personally been over a large part of the field containing the wonderful array of facts of which I am now permitted to write. In the autumn of 1887 I was invited to give a course of lectures upon the Ice Age in North America before the Lowell Institute in Boston, and in the following year be- fore the Peabody Institute in Baltimore. For the informa- tion of the audiences who heard those courses of lectures it is proper to say that the present treatise incorporates all the facts then presented, though in a different form. The volume covers, however, a much wider field than the lect- ures, and is more ample in its treatment of all the topics. But it is not to be supposed that a single person can PREFACE TO FIRST EDITION. 1X adequately survey so large a field. The writer is but one of many investigators who have been busily engaged for the past fifteen years (to say nothing of what had been previously accomplished) in collecting facts concerning the Glacial period in this country. My endeavor has been to make the present volume a pretty complete digest of all these investigations, and in carrying out that aim I have had the generous assistance of the great array of careful and eminent observers who have turned their attention to the subject. So far as possible I have, by their permission, given their results in their own language, and with due eredit. I hereby take occasion to express my obligations for the help which they have, one and all, so courteously rendered. The numerous maps accompanying the text have been compiled from the latest data, as indicated in the abundant foot-notes scattered throughout the volume. These render it unnecessary to make here any more specific acknowl- edgment of authorities. The volume is committed to the public in the belief that it will meet a widely felt want. The accumulation of facts for the past decade has been so rapid, and from so many sources, that few persons have been able to keep themselves informed of the progress made. And so great has this progress been that we may now safely assume that future discussions will pertain mainly to the details of the subject. We now know, from actual observation, the limits and prominent characteristics of the glaciated area on this continent. The Glacial age of North America is no longer a theory, but a well-defined and established fact. It will become apparent also that, though the title of the book is the “Ice Age in North America,” it is really x PREFACE TO FIRST EDITION. a treatise on the whole subject of the Glacial period; for, with the vast field open for investigation on this continent and the amount of attention recently given to its explo- ration, North America is now by far the most favorable place from which to approach the study of ice-action and ice periods. | The last chapters of the volume treat of man’s relation to the Ice age on this continent; and I need not disguise the fact that the bearing of the discoveries upon this ques- tion has all along given zest to my investigations. The facts with regard to this subject also are now so far in hand that they can be properly discussed in a treatise de- signed in part for the general public. While presenting as fully as is necessary the evidence of man’s occupancy of the continent during the great Ice age, and while accepting this as necessitating a considerable extension of man’s antiquity as usually estimated, I have not felt called upon in the present discussion to say any- thing about the method of reconciling this fact with the chronology of the human race supposed to be given in the sacred Scriptures; for I have elsewhere (in my “ Studies in Science and Religion,” W. F. Draper, Andover, 1882, and “Divine Authority of the Bible,” Congregational Pub- lication Society, Boston, 1884) said all that it seems at present necessary for me to say upon this point. I will only remark here that I see no reason why these views should seriously disturb the religious faith of any believer in the inspiration of the Bible. At all events, it is incum- bent on us to welcome the truth, from whatever source it may come. G. FRreperick WriGcHT. OBERLIN, On10, April 15, 1889. CONTENTS CHAPTER I. PAGE Wuat Is A GLACIER? : : 2 a : : 1-12 The Appearance of ice deceptive, 1 ; Discovery of its Real a 2 ; Motionofa Glacier, 2 ; Effect of Friction, 3 ; Cause of the Moticn, 4 ; Plasticity of fos 5 ; Rela- tion of Snow to Ice,6 ; Structure of a Glacier,7 ; Veins, 7 ; Fissures, 8 ;Ice-Pillars, 10 ; Terminal Moraines, 10 ; Kames, 11 ; Glacial Scratches and Groovings, 12. CHAPTER II. EXxIsTING GLACIERS ON THE Paciric Coast . : : 13-39 In Southern California, 13 ; in Northern California: Mount Shasta, 15 ; in Oregon, 19 ; in Washington Territory: Mount Tacoma, 19 ; British Columbiaand Alaska, 23 ; on the Stickeen River, 25 ; in Taku Inlet: Norris Glacier, 27; in Lynn Canal: Davidson Glacier, 27 ; north of Cross Sound, 29; on Mt. St. Elias, 30 ; in Yakutat Bay, 30 ;north of the Alaskan Peninsula, 36. CHAPTER III. A Monts WITH THE MuiIR GLACIER 2 d : : 40-74 Purposes of the Expedition, 40 ; Facilities for Observation, 41 ; Description of Glacier Bay and its Surroundings, 41 ; Muir Inlet, 43 ; Dimensions of the Muir Glacier, 43 ; Various Characteristics, 47 ; Moraines, 49 ; Indirect Evidences of Motion, 50; Formation of Icebergs, 51 ; Subglacial Streams, 51 ; Direct Measure- mentof Velocity, 52; Retreat of the Ice-front, 55; Former Extensionof the Glacier, 59 ;a Buried Forest, 61 ; Kamesand Kettle-holes, 66 ; Transportation and Waste by Water, 67 ; Temperature in August, 68 ; Floraof the Vicinity, 69 ; H. F. Reid’s Measurements, 71 ; F. E. and C. W. Wright’s Observations, 72. CHAPTER IV. GLACIERS OF GREENLAND ‘ : : 75-102 Extent of Greenland, 75 ; Nordenskiéld’s poeta rt 75 ; Amount of Coast Line already explored, 77 ; Number of First-class Glaciers in Danish Greenland, 78 ; Movementof Ice inthem, 78 ; Nunataks, 71 ; Former Extension oftheIce, 79 ; Helland’s Observations, 80 ; Whymper’s Description, 83 ; Explorations of Kane and Hayes, 86 ; Humboldt Glacier, 92 ; Glaciers on the Eastern Coast of Green- land, 97 ; Nansen’s Expedition, 98 ; Erichsen’s Expedition, 99 ; Holst’s Obser- vations on Frederickshaab Glacier, 100. xi X11 CONTENTS. CHAPTER V. PAGE GLACIERS IN OTHER PaRTS OF THE WORLD . : * 104-121 In the Alps, 104 ;in Scandinavia, 106 ;in Spitzbergen, Franz-Josef Land, and Ice- land, 107 ; in Asia, 107 ; in South America, 108 ; Darwin’s Account, 109 ; in New Zealand, 112 ; on the Antarctic Continent, 112 ; Icebergs of the Southern Ocean, 115 ; Croll’s Inferences from the Size of these Bergs, 118 ; Shackleton’s Expedition to the Antarctic, 120. CHAPTER VI. SIGNS OF GLACIATION. ; k = : 122-133 Introductory Remarks, 122 ; Groovesand Scratches, 123 ; Sir Charles Lyell’s Ob- servations in Nova Scotia, 126 ; the Ground Moraine, or ‘‘ Till,”’ 129 ; Cause of its being unstratified, 130 ; Sifting Power of Water, 131; Distribution of Bowl- ders, 132. CHAPTER VII. BOUNDARY OF THE GLACIATED AREA IN Norts AmeERiIcA 134-193 Confluent Character of the Ice-sheet, 134 ; Progress of Discovery, 134 ; Elements determining the Amount of Glacial Deposition, 135 ; Counteracting Influence of Subglacial Streams, 136 ; Influences determining the Amount of Marginal De- posits, 137 ; south of New England, 137 ; Interior Marginal Deposits, 139 ; Long Island a Moraine, 140 ; Marginal Deposits across New Jersey, 140 ; Rela- tion of Kettle-holes to the Moraines, 143 ; Marginal Deposits in Eastern Pennsyl- vania, 144 ; Western New York and Pennsylvania, 149. CHAPTER VII (contTINvUED). THE ATTENUATED BORDER . i ‘ s 2 3 151-166 Line of, 153 ; Lake Williams, 153 ; Character of Materialin, 154 ; Lake Lesley, 156 ; Lake Allegheny, 158 ; Changes of Land-level, 160 ; Valleys of the Allegheny River, Conewango Creek, and Ohio River, 161. CHAPTER VII (conciupEp). THE GuactIAL BouNDARY WEST OF PENNSYLVANIA ; 167-193 Marginal Deposits through Ohio, 167 ; Extension of the Ice into Kentucky, 170 ; Course of the Boundary in Indiana and Illinois, 170 ; Boundary west of the Miss- issippi, 172 ; west of the Rocky Mountains, 176 ; Ancient Glaciers in Southern California, 179; Glacial Boundary north of Puget Sound, 183 ; near the Head- waters of the Yukon, 190; Summary of Facts regarding the Pacific Coast, 190. CHAPTER VIII. . Depts or IcE DURING THE GLACIAL PERIOD : : 194-202 Means of Estimating it, 194 ; Mountain Summits covered in New England, New York, and Pennsylvania, 194 ; Depth estimated from the Distance moved, 199 ; Slope of a Glacier, 201. CONTENTS. xili CHAPTER IX. PAGE TERMINAL MORAINES x : 203-225 Indefiniteness of the Term, 203 ; Prominence of the Moraine south of New Eng- land, 204 ; Details respecting the Kettle-holes in this Part of the Moraine, 205 ; Submerged Portions of the Moraine, 206 ; Moraines of the Middle States, 207 ; President Chamberlin on the Moraines west of the Alleghanies, 207 ; Gilbert on the Moraines of the Maumee Valley, 207 ; the Kettle Moraine of Wisconsin, 211 ; Battle of the Glaciers in Minnesota and Wisconsin, 212 ; Moraines in Dakota,214 ; in Central British America, 217 ; Later Moraines in the White Mountains, 221 ; on the Sierra Nevada and Cascade Mountains, 222 ; Moraines of the Wisconsin Episode, 222 ; Ilinoisan Deposits, 223 ; Iowan Deposits, 223 ; Kansas Deposits, 224 ; the Aftonian Episode, 224. CHAPTER X. GLACIAL EROSION AND TRANSPORTATION i : ; 226-280 Erosive Action of Ice compared with that of Running Water, 226 ; Chemical Action of Water, 229 ; Danger of exaggerating the Erosive Action of Ice, 230; Glacial Erosion least near the Margin, 233 ; Analogy between the Glacial Front and Breakers in the Ocean, 234 ; Transportation of Bowlders on the Surface of a Glacier, 236 ; Details respecting, in Southern New England, 237 ; in Richmond, Mass., 239 ; in New Jersey and Pennsylvania, 241 ; in Ohio, 242; in Southern In- diana and Illinois, 243 ; in lowa and Dakota, 248 ;in British America, 244 ; Ele- vation of Bowlders in the Ice, 246 ; Explanation of, 248 ; Erosion of Subglacial Streams, 254 ; Erosion estimated by the Amount of Till, 257 ; Attemptsat Direct Measurement of Glacial Erosion near the Delaware Water-Gap, 260 ; affected by Preglacial Disintegration, 261 ; Evidence of, near Western End of Lake Erie, 262; in the Sierra Nevada, 267 ; Summary, 279. CHAPTER XI. DRUMLINS seater : : 4 : ‘ , : 281-297 Definition, 281 ; those in the Vicinity of Boston Enumerated, 281; Mr. Upham’s Description, 282 ; Series of, in Rockingham County, N. H., and Essex County, Mass., 284 ; Occurrence of, in the Interior of the Country, 285 ; Theory of their Formation, 287; Irregularities of Glacial Erosion and Deposition, 294. CHAPTER Xfi. PREGLACIAL DRAINAGE . : , 298-312 Length of Preglacial Time, 298 ; extent of melts ileal 299 ; the Trough of the Ohio preglacial, 300 ; Other Preglacial Valleys, 302 ; Preglacial Drainage of the Great Lakes, 304 ; Preglacial Drainage of the Upper Allegheny River into Lake Erie, 307. CHAPTER XIII. DRAINAGE OF THE GLACIAL PERIOD 2 7 : 313-337 Obstruction of Ice-barriers across the Red River of the Sad the St. Lawrence, and the Mohawk, 313 ; Closing Floods of the Glacial Period, 314 ; Terraces pro- duced by these Floods in the Trough of the Mississippi; in the Minnesota, 315 ; XiV CONTENTS. PAGE inthe Northern Tributaries of the Ohio, 323 ; in the Streams of Northern Pennsyl- vania, 325 ; Material composing the Glacial Terraces, 325 ; such Terraces absent from Streams wholly in the Unglaciated Region, 325 ; Terraces on the Ohio, 327 ; on Beaver Creek, Pa., 328 ; on the Delaware, 289 ; Relation of Pot-holes in Graf- ton, N. H., to Glacial Drainage, 330 ; Similar Phenomena in Lackawanna County, Pa., 331 ; Remarkable Evidence of Abnormal Glacial Drainage in Dakota, 332 ; Marginal Drainage in the Northwest, 334. CHAPTER XIV. KAMES. : ; : ; : ’ ; ‘ 339-354 In Andover, Mass., 339 ; Definitions, 339 ; Geikie’s Description, 339 ; Relations of Kames to Terminal Moraines, 340 ; Origin of, 341 ; indicate Lines of Temporary Glacial Drainage, 342 ; Lines of, in New England enumerated, 343 ; Questions respecting, inthe Connecticut River Valley,345 ; Possible Extent of Glacial Floods in this Valley, 346 ; Relation of Sandy Plains to Kames, 348 ; Existence of Kames foretold, 349 ; Overwash Gravel limited in Amount, 350 ; Abnormal Relation of Kames to the Slope, 351 ; Summary, 353. CHAPTER XV. GuactiaAL Dams, LAKES, AND WATERFALLS : ’ 355-406 Rock Basins eroded by Glaciers, 355 ; Theory of the Great Lakes, 356 ; Two Classes of Glacial Dams, 359 ; Kettle-holes, 359 ; Relation of, to Peat-bogs and to Terminal Moraines, 360 ; Lakes formed by Permanent Obstruction of Preglacial Channels, 362 ; the Formation of Waterfalls, 362 ; Temporary Lakes formed by Ice Barriers, 363 ; Supposed Glacial Dam in the Ohio, at Cincinnati, 366 ; Evi- dence that the Ice crossed the Ohio, 367 ; Consequences of such an Obstruction, 368 ; History of its Discovery, 370 ; Theory discussed by the American Associa- tion for the Advancement of Science, 371 ; Theory confirmed by the Absence of . Terraces in Brush Creek, Ohio, 372 ; by the Terrace at Bellevue, Pa., 375 ; Diffi- culty of Other Explanations, 376 ; the Occurrence of Vegetable Matter in the Terraces of the Monongahela support the Theory, 377; Teazes Valley, W. Va., ex- plained by the Theory, 379 ; Various Other Phenomena explained in a Similar Manner, 382 ; Objections considered, 383 ; Claypole on, 386 ; Glacial Dam in the Monongahela, 391 ; the Lake Ridges of Ohio and New York, 395 ; Glacial Dam aeross the Malawi: and the St. Lawrence, 398 ; Glacial Lake in the Red Reem Region of the North: Lake Agassiz, 401. CHAPTER XVI. THE LOEss : : P 3 : k 407-421 Extent of the Deposit in China and North America, 407 ; Richthofen’s Theory of Deposition by Wind, 408 ; Difficulties of the Theory, 410 ; Characteristics of, 412 ; Changes of Level Necessary, 413 ; Probable Connection with Glacial Floods, 415 ; Supplementary Theories, 417. CHAPTER XVII. FLicut oF PLANTS AND ANIMALS DURING THE GLACIAL PERIOD 422-444 Peculiar Distribution of Plants in the North Temperate Zone, 422 ; Professor Asa Gray’s Solution of the Problem, 424 ; more Detailed Statement by Professor Gray, 425 ; Comparison of the Pacific with the Atlantic Forests, 426 ; Comparison CONTENTS. XV PAGE of both with those of Japan, North China, and Europe, 427 ; Number of Pre- glacial Species now found in the Temperate Zone, 430 ; our Trees originated in the High Latitudes, 432 ; the Vicissitudes to which they have been subjected since the Approach of the Glacial Period, 433 ; Open Lines of Emigration in America, 434 ; Peculiar Influences upon the Pacific Coast, 435 ; Extinction of Animals in America by the Glacial Period, 436 ; Alpine Butterflies upon the White Moun- tains, 438 ; List of Plants common to the Okhotsk-Kamchatkan Region and North America, 441. CHAPTER XVIII. EUROPE DURING THE GLACIAL PERIOD ; ’ 445-459 Glaciated Area in Great Britain, 445; on the Continent, 447; Investigations of Professor Lewis, 448; Summary of Conditions in Great Britain by Dr. Harmer, 454; Investigations of Professor Salisbury, 456. CHAPTER XIX. Tue CAUSE OF THE GLACIAL PERIOD : Lite as / 461-494 Recent Astronomical Speculations, 461; the Combination of Conditions necessary to produce a Glacier, 461; Theories toaccount for the Glacial Period, 463; Decrease of the Original Heat of the Planet, 463; Shifting of the Earth’s Axis of Rotation, ~ 463; Theory of Progressive Desication, 464; Depletion of Carbon Dioxide in the Atmosphere, 464; Different Temperatures of Space, 465; Mr. Croll’s Theory: the Ellipticity of the Earth’s Orbit and the Precession of the Equinoxes, 466; Possible Effect of these upon the Climate, 467; Cause of the Gulf Stream, 469; Causes con- trolling the Distribution of the Heat from the Sun, 477; Woeikoff’s Objections to Croll’s Theory, 479; Supposed Evidence of Former Glacial Periods, 483; Carbon- iferous and Cambrian Glacial! Periods now established, 490. CHAPTER XIX (CONTINUED). THE CAUSE OF THE GLACIAL PERIOD A : ; s 495-531 Effect of Changes in the Distribution of Land and Water, 495; Theory of Changes of Level, 496; Supplementary Notes by Warren Upham, 520; produced by the Accumulation of Snow over Definite Centers, 525; Field for Mathematical Inves- tigation, 528; Summary, 529. CHAPTER XX. Tue DaTeE OF THE GLACIAL PERIOD : : : F 532-615 Uncertainty of As_ronomical Calculations, 532; Detect in Lyell’s Theory of Uni- formitarianism, 533; Post-glacial Erosion below Niagara Falls, 536; below Falls of St. Anthony, 552; in Ohio, 560; Freshness of the Glaciated Surfaces, 568; Post-gla- cial Erosion in Minnesota, 571; about Lake Michigan, 571; Post-glacial Deposition in Kettle-holes, 572; the Question of Two or More Post-tertiary Glacial Epochs, 575; Greater Oxidization of Material near the Glacial Boundary, 579; Freshness of In- terglacial Forest-beds, 592; Growth of Peat, 594; Extent of Forest-beds, 603; Former Extension of Lakes Bonneville and Lahontan, 607; Recentness of these Lakes, 610; Length of the Glacial Period, 613; Summary, 614. Xvi : CONTENTS. CHAPTER XXI. PAGE MAN AND THE GLACIAL PERIOD t : : ; : 616-668 Prominence given by Lyell to the Subject, 616; Artificislity of the Implements, 617; Professor Haynes ou, 619; Genuineness of, 622; Discoveries of Boucher de Perthes in France, 624; of other Investigators in England, 624; of Dr. Abbott in New Jersey, 625; Nature of the Gravel at Trenton, 630; Mode of Deposition, 634; Series of Events in the Delaware Valley, 639; Discoveriesin Ohio foretold, 640; Discoveries by Dr. Metz, in Ohio, 642; Deposit at Madisonville, Ohio, described, 644; Discovery by Mr. Mills at Newcomerstown, Ohio, 645; Discovery by Mr. Huston at Brilliant, Ohio, 648; Cresson’s Discoveries at Medora, Ind., 649; Win- chell’s Discoveries in Morrison County, Minn., 653; Miss Babbitt’s Discoveries at Little Falls, Minn., 654; Upham’s Discussion of the Deposits in Minne- sota, 654. CHAPTER XXII. MAN AND THE GLACIAL PERIOD (CONTINUED) , : 669-676 Cresson’s Discoveries at Claymont, Del., 669; Prehistoric Development in the Delaware Valley, 674. CHAPTER XXIII. MAN IN THE MissouRI VALLEY ! ; : ; : 678-686 Discovery at Lansing, Kan., 678; Nature of the Deposit at Lansing, Kan., 679; Nebraska Loess-Man, 683; Nature of Deposit in which found, 683; Discovery at St. Joseph, Mo. 685. CHAPTER XXIV. MAN AND THE LAVA Brps OF THE PaciIFic Coast ; P 687-709 Whitney’s Discoveries in California, 688; Le Conte on the Quaternary Deposits _of California, 689; Whitney’s Evidence in Detail, 692; Stone Mortars from under Table Mountain, 694; Criticism of Whitney, 697; the Nampa Image, 701; Conclu- sion, 706. BIBLIOGRAPHY : : : : : : : 711-741 EN DEX 3% ‘ : d : ‘ ‘ . 743-763 LIST OF ILLUSTRATIONS Front of Muir Glacier, Alaska, from the southeast corner, looking across the sur- face and up one of the tributaries ’ ? : : , . Frontispiece. FIG. ; i PAGE 1. Differential motion of ice : Bree ne , ‘ : . : vee 2, 3. Differential motion of ice s 2 zg : : . a : ‘ 3 4. Plasticity ofice . : 5 : 4 f . : 4 : ; Sai 5. Fissures and seracs 2 : : ; : ‘i ‘ a eet: 6, 7. Marginal fissures and ian é 8 8. Veined structure at the junction of Paes bainehen i i z £ é Pio!) 9. Mode of formation of ice-pillars . , ; ‘ , F Z ’ : we) 10. Moraines of the Mer de Glace Cte ee eee Ee gt nD 11. Glacial scorings = 5 : P eee é , : Se 12. West end of Samovar Gineier, Masks 2 é 2 : 3 F 5 ‘ yee! 13. Mount Shasta, California. (Russell.) a 3 A 4 a ty 14. Mount Tacoma, Washington State, looking wasted, (Chatios S. Fee.) . oa) 15. Mount Tacoma, Washington State, looking eastward. (CharlesS.Fee.) . ) aA M9 coming down to a gentler slope they close up again at Fic. 5.—c, ¢, show fissures and seracs where theglaciermoves the surface for down the steeper portion of its incline; s,s, show the a pees structure produced by pressure on the gentler their onward slopes. | i\ march. _ In addition to the crevasses or fissures, produced by the tension where the ice-stream passes over a steeper incline, a set of marginal fissures extend from the sides of the glacier toward the center, but pointing upward at an angle of about forty-five degrees. These, too, appear to be the result ( of tension. The motion of au the ice in the center, being ive more rapid than that to- ward the sides, producesa | / ! line of tension, or strain, ex- tending from the center di- 4 agonally downwar d toward Fies. 6, 7 eee the totais ae the sides at an angle of al fissures and veins. forty-tive degrees. The pressure upon these masses of ice, whose central point is being wheeled downward by the differ i Vere ae oes To 2 WHAT IS A GLACIER? 9 ential motion, produces also a veined structure in the masses themselves, at right angles to these marginal fissures. The surface of a glacier presents many interesting phe- nomena. When the ice-stream is of sufficient size, the sur- face is covered with a network of small streams of water, flowing through blue channels of ice sometimes many yards in depth and width. but these are destined eventually to encounter some crevasse, where a circular shaft, or moulin, as it is called, is formed, opening a way to a subglacial chan- nel, into which the streams plunge fe. 8.—tustrates the forma- with a loud roar, and the accumulated preeeeve aly the guhction ct waters may often be heard rushing Bis sta onward hundreds of feet below the surface. During the melting of a glacier, also, in the summer season, the surface of the ice is frequently dotted with bowl-shaped depressions, from one or two inches to many feet in depth, and filled with beautiful clear water. The cause of this can not well be conjectured. In Greenland, Nordenskidld attributed the initial melting to accumulations of meteoric dust which he named kryokonite. Glaciers in mountainous regions are also characterized by lateral and medial moraines. Where the ice stream passes by a mountain-peak, the falling rocks and the avalanches started by streams of water, form along the edge of the gla- cier a continuous line of débris, which is carried forward by the moving ice, and constitutes what is called a lateral mo- raine. If there be a current of ice on each side of the mount- ain-peak, two of the lateral moraines will become joined be- low the mountain, and will form what is called a medial moraine, which will be carried along the back of the ice as far as the motion continues. As the ice wastes away toward the front, several medial moraines sometimes coalesce. This, as will be seen, is finely shown in some glaciers of Alaska. A medial moraine, when of sufficient thickness, protects 10 THE ICH AGE IN NORTH AMERICA. the ice underneath it from melting; so that the moraine will often appear to be much larger than it really is: what seems to be a ridge of earthy material being in reality a long ridge of ice, thinly covered with earthy débrvs, sliding down the slanting sides as the ice slowly wastes away. Large blocks of stone in the same , manner protect the ice from melting un- Fie. 9._Mode of formation derneath, and are found standing on pe- ae destals of ice, where the general surface has been lowered sometimes several feet. An interesting feature of these blocks is that when the pedestal fails, the block uniformly falls to- ward the sun, since that is the side on which the melting has proceeded most rapidly. 3 All the material brought down upon the surface of the glacier in the medial moraines is deposited ‘at the front, forming a terminal mo- raine, which will vary in size according to the abundance of material transported by the ice, and in proportion to the length of time during which the front rests at a particular point. But, TT a e . e ON SS - 4 \ = ordinarily, for a consid- 1; Ari alg WS ° F My) ll WENA NS SS erable distance this mo- N at — raine material near the He NE Cal MEG front will rest upon ex- Fie. 10.—Mer de Glace. The parallel lines in the tensive Masses of 1c€ middle are medial moraines, The main ice- : stream on the right pushes the others to the wall, which only slowly melt and divides the terminal moraine above g. WHAT IS A GLACIER? 11 away. It is largely owing to this that a true terminal moraine is made up of knolls and bowl-shaped depressions ealied ettle-holes, and ot short tortuous ridges of bowlders and gravel. : Another result connected with the decay of a glacier is the production of kames—this being the Scotch word for sharp, narrow ridges of gravel, corresponding to what are called osars in Sweden and eskers in Ireland. The trend of these ridges is the same as that of the motion of the glacier, and is at right angles to the terminal moraine. Their for- mation can be witnessed on a large scale near the front of the Muir Glacier in Alaska. In certain localities a great amount of sand, gravel, and bowlders becomes spread out over the surface of the ice at a considerable elevation. Through some changes in the subglacial drainage a stream wears a long tunnel in the ice underneath this deposit, which at length proceeds so far that the roof caves in, and the earthy débris is gradually precipitated to the bottom of the tunnel, thus forming one class of kames. In other places, evidently, water-worn channels in the ice have been silted up by the stream, and then the line of drainage changed, so that, when the supporting walls of ice melted away, another class of kames, with what is called “ anticli- nal” stratification, is produced. It should be mentioned also that, after the analogy of a river, a glacier shoves sand and gravel and bowlders under- neath it along its bed; from which it can easily be seen that a glacier is a powerful eroding agency, rasping down the surface over which it moves, and by the firm grasp in which it holds the sand, gravel, and bowlders underneath it, pro- ducing grooves and scratches and polished surfaces on the rocks below, whiie these stones themselves will in turn be scratched and polished in a peculiar manner. Wherever the glaciers have receded, so that their bed can be examined, these phenomena, which we reason from the nature of the case must lave been produced, are found actually to occur, and a terminal moraine is sure to contain many pebbles and ii i =) im 12 THE ICH AGE IN NORTH AMERICA. bowlders bearing marks of the peculiar attrition to which they have been subjected in their motion underneath the ice. The rocks brought along upon the surface of the gla- cier of course are not thus striated, and ordinarily the mate- Fie. 11.—Glacial scorings (after Agassiz). rial of the kames has been so much rolled by water that if the pebbles ever were scratched, the marks have been erased. With this brief account of the physical characteristics of ice, and of the effects produced by its movement in a gla- cler, we are prepared to enter more understandingly upon a survey of the actual facts relating to the past and present extent of the ice-fields over the northern part of North America. Reserving the discussion of theories concerning the cause and date of the glacial period to the latter part of the treatise, we will first consider the facts concerning the glaciers still existing in America, and then briefly, by way of comparison, those concerning glaciers in other portions of the world; after which we will present in considerable detail the more recent discoveries concerning the extension and work of the great American ice-sheet during the so- called Glacial period. ee ne ee ye S ‘ = — s — = — 4 — 7 . a : . 0 - Y a - ae epee ae * ~ s] (‘Arredg Aq 004g) "(9893 00¢'9 ‘opnyiiy[e) exe] seyxVg Arey * (1003 0¢7'g) Yeog JYSISUND WO ddINOs 87] PIEMO}Y PICMYINOS SUIYOOT ‘vuviUOTW ‘1epovpy Alieodg—] ALVIgG ere ay eo | ‘ CHAPTER II. GLACIERS ON THE PACIFIC COAST. NOTWITHSTANDING the great height of the Rocky Moun- tains, they are, in the southern part, devoid of living glaciers. This lack is doubtless caused by the dryness of the atmos- phere, the winds from the Pacific having already, before reaching the interior, yielded their moisture to the solicita- tions of the lofty peaks of the Sierra Nevada and the Cascade Range. Still, a few small glaciers are found among the sum- mits of the Wind River Mountains of Wyoming, and near the sources of Flathead River in Montana. Farther north, how- ever, near the Canadian boundary, glaciers begin to appear in increasing number and size. The broad picturesque sum- mits of the Rocky Mountains forming the continental divide between the head-waters of the Flathead River in Montana and those of the Belly,a branch of the Saskatchewan, in Canada, support innumerable glaciers of small size and many that compare Well with those of the Alps. More than forty are found between Lake McDonald and the Canadian bound- ary. Of these the Sperry and Chaney glaciers are most conspicuous. Avalanche Lake, surrounded by glacier-cov- ered peaks, is one of the most picturesque localities on the continent. | In the Canadian Rockies and in the Selkirk Mountains, - north of the line, in Alberta and British Columbia, glaciers increase in numbers and size as higher latitudes are reached. Of these the Victoria, the Wenkchemna, the Yoho, the [llecille- waet and the Asulkan are so near stations on the Canadian 14 THE ICE AGE IN NORTH AMERICA. Pacific Railroad that they can be easily visited by tourists. The snow-fields of all these are from 9,000 to 10,000 feet above sea-level, but none of the glaciers descend much below 6,000 feet, except the Illecillewaet which reaches the level of 4,800 feet. cae Fie. 12.—West end of Samovar Glacier. Alaska. A wide arid space, of which few who have not traversed the region can have any conception, separates the Rocky Mountains from the Sierra Nevada nearer the Pacific coast. This latter range of mountains is, in some respects, favorably situated for the production of glaciers, since the peaks are lofty, rising in many places upward of 14,000 feet, and there is abundance of snowfall. Ordinarily, however, there is not breadth enough to the summit of the range to furnish ade- quate snow-fields for the production of first-class glaciers. The most southern collection of glaciers in the Sierra Nevada is found near the thirty-seventh parallel, a little east of the Yosemite Valley, in Tuolumne and Mono coun- ties, California. Here is a remarkable cluster of mount- GLACIERS ON THE PACIFIC COAST. 15 ain-peaks rising upward of 14,000 feet above the sea, and with breadth enough to support numerous snow-fields and glaciers. No less than sixteen glaciers of small’ size have been noted among these summits, of which those on Mount Dana, Mount Lyell, and in Parker Creek are the principal. None of them, however, are of great size, being in no case over a mile in length, and none of them descending much below the 11,000-foot line.* The continuation of the Sierra Nevada Mountains to the north of California is called the Cascade Range, and is largely composed of voleanic rocks. It is on Mount Shasta, in the extreme northern portion of California, that we next find glaciers of any considerable size. But from this point on, glaciers multiply and continue, in ever-increasing glory, through the Coast Range of British Columbia and southern Alaska to the islands of the Aleutian Archipelago. ' The glaciers upon Mount Shasta were first described by Mr. Clarence King in 1870. Previous explorers had as- cended the mountain upon the southern side, and reported it as free from glaciers, which are all upon the northern side. The most recent and detailed account of the glaciers on this mountain has been furnished by Mr. Gilbert Thompson, of the United States Geological Survey.t According to Thomp- son, Mount Shasta is a volcanic peak whose altitude above the sea is 14,511 feet. “It stands alone and has no connec- tion with neighboring mountains, none of which within a radius of forty miles attain two thirds its height.’ The mountain is a conspicuous object to attract attention for over a hundred miles. Five glaciers have been explored upon its northern flank, none of them, however, reaching lower than the 8,000-foot level, and none being more than three miles in length. The lower part of these glaciers is covered with vast quantities of earthy débrzs, so that it is difficult to tell where the ice-field now ends. It was from these half-buried edges * Russell, “ Existing Glaciers,” pp. 310-327. +t Ibid., pp. 832-534. 16 THE ICE AGE IN NORTH AMERICA. of the ice-front on the flanks of Shasta that Mr. King drew the anaiogies which first solved the problem of the irregular gravel deposits forming the so-called kames and kettle-holes in New England, as above described.* Mr. King gives a thrilling account of how he at one time started such a move- ment of earth into one of the ice-tunnels, and came near himself falling into the yawning ice-chasm.t The following are the principal portions of Mr. King’s clear and vivid description of the glaciers on the north side of Mount Shasta: We reached the rim of the cone, and looked down into a deep gorge lying between the secondary crater and the main mass of Shasta, and saw directly beneath us a fine glacier, which started almost at the very crest of the main mountain, flowing toward us, and curving around the circular base of our cone. Its entire length in view was not less than three miles, its width opposite our station about four thousand feet, the surface here and there terribly broken in ‘‘ cascades,” and presenting all the characteristic features of similar glaciers else- where. The region of the terminal moraine was more extended than is usual in the Alps. The piles of rubbish superimposed upon-the end of the ice indicated a much greater thickness of the glacier in former days. After finishing our observations upon the side crater, and spending a night upon the sharp edge of its rim, on the following morning we climbed over the divide to the main cone, and up the extreme summit of Shasta. ... From the crest I walked out to the northern edge of a prominent spur, and looked down upon the system of three considerable glaciers, the largest about four and a half miles in length,{ and two to three miles wide. On the next day we descended upon the south side of the cone, following the ordinary track by which earlier parties have made the climb. From the moment we left the summit we encountered * Russell, “ Existing Glaciers,” p. 11. + “ Proceedings of the Boston Society of Natural History,” vol. xix, p. 61. t These estimates prove to be somewhat exaggerated. Thompson gives the length of the Whitney Glacier, the longest on the mountain, as only 3,800 yards, less than two miles and a half. United States Geological Survey (Russell). rnia. Fi1a.. 13.—Mount Shasta, Califo 18 THE ICH AGE IN NORTH AMERICA. less and less snow, and at no part of the journey were able to see a glacier. An east-and-west line divides the mountain into glacier-bearing and non-glacier-bearing halves. The as- cent was formerly always made upon the south side, where, as stated, there are no glaciers, and this is why able scientific observers like Professor Whitney and his party should have scaled the mountain without discovering their existence. . . . Upon reaching the eastern side we found in a deep cafion a considerable glacier, having its origin in a broad néve which reaches to the very summit of the peak. The entire angle of this glacier can be hardly less than twenty-eight degrees. It is one series of cascades, the whole front of the ice being crevassed in the most interesting manner. Near the lower end, divided by a boss of lava, it forks into two distinct bodies, one ending in an abrupt rounded face no less than nine hundred feet in height. Below this the other branch extends down the cafion for a mile and a half, covered throughout almost this entire length with loads of stones which are constantly fall- ing in showers from the cafion-walls on either side. Indeed, for a full mile the ice is only visible in occasional spots, where cavities have been melted into its body and loads of stones have fallen in. From an archway under the end a consider- able stream flows out, milky, like the water of the Swiss glacier-streams, with suspended sand. Following around the eastern base of Shasta, we made our camps near the upper region of vegetation, where the forest and perpetual snow touch each other. A third glacier, of somewhat greater extent than the one just described, was found upon the northeast slope of the mountain, and upon the north slope one of much greater dimensions. The exploration of this latter proved of very great interest In more ways than one. Receiving the snows of the entire north slope of the cone, it falls in a great field, covering the slope of the mountain for a breadth of about three or fonr miles, reaching down the cafions between four and five miles, its lower edge dividing into a number of lesser ice- streams which occupy the beds of the cafions. This mass is sufficiently large to partake of the convexity of the cone, and, judging from the depth of the cafions upon the south and southeast slopes of the mountain, the thickness can not be less Puiate 1l—Geikie Glacier and Hanging Glacier on Mounts Fox and Dawson, British Columbia. (Photo by Canadian Topographical Survey.) GLACIERS ON THE PACIFIC CCAST. 19 than from eighteen to twenty-five hundred feet. It is cre- yassed in a series of immense chasms, some of them two thou- sand feet long by thirty and even fifty feet wide. In one or two places the whole surface is broken with concentric systems of fissures, and these are invaded by a set of radial breaks which shatter the ice into a confusion of immense blocks. Snow-bridges similar to those in the Swiss glaciers are the only means of crossing these chasms, and lend a spice of danger to the whole examination. The region of the terminal moraines is quite unlike that of the Alps, a larger portion of the glacier itself being covered by loads of angular dédris. The whole north face of the mountain is one great body of ice, interrupted by a few-sharp lava-ridges which project above its general level. The veins of blue ice, the planes of stratification, were distinctly observed, but neither moulins nor regular dirt-bands are present. Numerous streams, how- ever, flow over the surface of the ice, but they happen to pour into crevasses which are at present quite wide. * From Mount Shasta to the Columbia River the moun- tains support many glaciers of thethirdorder. Mount Jef- ferson, Diamond Peak, and the Three Sisters are reported by Mr. Diller and Professor Newberry as containing numer- ous glaciers, and “‘as affording the most interesting field for glacial studies in the United States, with the exception of Alaska.” The glaciers upon Mount Hood have been more fully explored, and are of great interest, though, owing to the moderate elevation (11,000 feet) and the limited snow- fields, they are small in size. The summit of this mountain is occupied by a volcanic crater about half a mile in diameter. This serves as a fountain out of which there flow three . streams of ice extending down the flanks, as glaciers, for a distance of about two miles, their subglacial streams form- ing the head-waters of the White Sandy, and the Little Sandy Rivers. In the State of Washington, a short distance northof the Columbia River, the Cascade Mountains culminate in a clus- * “American Journal of Science,’’ vol. ci, 1871, pp. 158-161. (aan 'S SoLIvyO jo Ag0j1n09 ou YSnoIy) posn a1B SMOTA 9Soy} WIOG) “JUW908B 1104) s}duwe}}8 oUO VAY AHI] PUB YSnor A[SUITAPPYAMIBAO DUODOq ‘adURISIP B WOAJ oSed ajIsoddo aq} UO MOIA OY] Ul Uses souod [NJoovls oy, ‘syvoed-ureyunoUt Jo suors -WOUIIP SBA OY} JO REPT ond] B SjJos UO JVY} SI) Sv SUOTIISOd TONS WO JJ 81 qT ‘AQ1OBLH IOAIY UOGIeD oY) puB ‘pley-Mous [Bnyjodied B IaAO Jo0J puRs -Noy} U0} JO UOLJBAV[a UL WOIJ PIBMJSOM SUIYOOT ‘VUIODR], JUNOW—'PT * ol GLACIERS ON THE PACIFIC COAST. 21 ter of peaks, with Mount Rainier, or, as it is coming to be ealled, Tacoma, as the center. This central peak is upward of 14,400 feet in height, and two or three neighboring peaks are upward of 10,000 feet. This great elevation, coupled with the higher latitude and the increasing moisture of the climate, favors the production of a most imposing series of glaciers. Even the passing traveler upon the railroad is made aware of their existence by the milky whiteness of the waters of the Cowlitz, the Nisqually, the Puyallup, and the White River, which are crossed on the way from Portland, Oregon, to Seattle in the State of Washington. All of these streams originate in glaciers far up on the flanks of the mountains to the east and south. Of this series, that on the north side of Mount Taco- ma, at the head of White River Valley, is the largest, and + : i Fie. 15.—Mount Tacoma, looking eastward toward the summit, from Crater Lake. reaches down to within 5,000 feet of the sea-level. This glacier is about ten miles long, and, though comparatively narrow in its lower portion, is in places as muchas four miles wide. The extreme summit of the mountain has been ascended only by two or three parties, and the task is beset with such difficulties that it is not likely to be ascended often. Above the 9,000-foot level it is wholly enveloped in snow; while just below that limit, and close up to the realm of perpetual ice and snow, flowers make the air fragrant with 992 THE ICE AGE IN NORTH AMERICA. their perfume, and the open spaces are gorgeous with their masses of brilliant color. The following is the description of the glaciers of this mountain cluster, as given by Mr. S. F. Emmons, of the United States Geological Survey, the first to ascend it: The main White River glacier, the grandest of the whole, pours straight down from the rim of the crater in a northeast- erly direction, and pushes its extremity farther out into the valley than any of the others. Its greatest width on the steep slope of the mountain must be four or five miles, narrowing toward its extremity to about a mile and a half; its length can be scarcely less than ten miles. The great eroding power of glacial ice is strikingly illustrated in this glacier, which seems to have cut down and carried away, on the northeastern side of the mountain, fully a third of its mass. The thickness of rock cut away—-as shown by the walls on either side—and the isolated peak at the head of the triangular spur . . . may be roughly estimated at somewhat over a mile. Of the thick- ness of the ice of the glacier I have no data for making esti- mates, though it may probably be reckoned in thousands of feet. It has two principal medial moraines, which, where crossed by us, formed little mountain-ridges, having peaks nearly one hundred feet high. The sources of these moraines are cliffs on the steeper mountain-slope, which seem mere black specks in the great white field above; between these are great cas- cades, and below, immense transverse crevasses, which we had no time or means to visit. The surface water flows in rills and brooks on the lower portion of the glacier, and moulins are of frequent occurrence. We visited one double moulin, | where two brooks poured into two circular wells, each about ten ieet in diameter, joined together at the surface but sepa- rated below ; we could not approach near enough the edge to see the bottom of either, but, as stones thrown in sent back no sound, judged they must be very deep. This glacier forks near the foot of the steeper mountain- slope, and sends off a branch to the northward, which forms a large stream flowing down to join the main stream fifteen or twenty miles below. Looking down on this from a high, over- GLACIERS ON THE PACIFIC COAST. 23 hanging peak, we could see, as it were, under our feet, a little lake of deep, blue water, about an eighth of a mile in diameter, standing in the brown, gravel-covered ice of the end of the giacier. On the back of the rocky spur which divides these two glaciers, a secondary glacier has scooped out a basin-shaped bed, and sends down an ice-stream, having all the characteris- tics of a true glacier, but its ice disappears several miles above the mouths of the large glaciers on either side. Were nothing known of the movement of glaciers, an instance like this would seem to afford sufficient evidence that such movement exists, and that gravity is the main motive-power. From our north- ern and southern points we could trace the beds of several large glaciers to the west of us, whose upper and lower portions only were visible, the main body of the ice lying hidden by tke high intervening spurs. Ten large glaciers observed by us, and at least half as many more hidden by the mountain from our view, proceeding thus from an isolated peak, form a most remarkable system, and one worthy of a careful and detailed study.* Still farther to the north, in the State of Washington, Mount Baker, rising to an elevation of 11,000 feet, is to a limited extent a center for the dispersion of glaciers of small size. The field, however, has been but imperfectly explored. Northward from the State of Washington the coast is everywhere very rugged, being formed by the lofty peaks of an extension of the Cascade Range; while the thousands of islands which fringe the coast of British Columbia and Alaska are but the partially submerged peaks of an extension of the Coast Range, from which the great glaciers of former times have scraped off nearly all the fertile soil. It is estimated that there are ten thousand islands between the State of Washington and Mount St. Elias, and all the larger of them bear snow-covered summits during the whole year. The water in the narrow channels separating these islands is ordinarily several hundred feet deep, affording, through nearly the whole distance, a protected channel for navigation. * Quoted by Clarence King, in the ‘“‘American Journal of Science,” vol. ci, pp. 164, 165. =i o Ly Sets ay td, FS iS dv ai TASS IF way) gj pat a aye SS unr TS) Ni ZT )F MILES SCALE OF 40 20 The arrow-points mark glaciers. Fic. 16.—Map of Southeastern Alaska. (“reJeeY MA 'O “V Aq OJOYd) “VIQUINTOH YSW1g_ ‘SplegMoug puY siopOB[H UBY[NSY PUB YoVAMOT[IOIT[] Jo MOTA—JI] ALvTg peg gg GLACIERS ON THE PACIFIC COAST. 20 Three great rivers interrupt the mountain barrier of British Columbia facing the Pacific—the Fraser, the Skeena, and the Stickeen—and the interior is penetrated for some distance by innumerable fiords. The Canadian Pacific Rail- road follows the course of the Fraser for a long distance, and passes within sight of glaciers of considerable extent, and every fiord receives the drainage of numerous decaying gla- ciers. But it is not until reaching the Stickeen River, in Alaska, in latitude 57°, that glaciers begin to appear which are both easily accessible and large enough to invite pro- tracted study. The water coming into the sound from the Stickeen River is heavily charged with glacial mud, which spreads itself out over a great expanse. An extensive celta, forming almost the only arable land in southeastern Alaska, has been built up by the deposit at the mouth of this river. The earliest accurate information obtained concerning these glaciers is that gathered by Mr. William P. Blake in 1863. According to him, “there are four large glaciers and several smaller ones visible within a distance of sixty or seventy miles from the mouth” of the river. The second of these larger ones has attracted most attention. This “sweeps grandly out into the valley from an opening between high mountains from a source that is not visible. It ends at the level of the river in an irregular bluff of ice, a mile and a half or two miles in length, and about one hundred and fifty feet high. Two or more terminal moraines protect it from the direct action of the stream. What at first appeared as a range of ordinary hills along the river, proved on landing to be an ancient terminal moraine, crescent-shaped, and covered with a forest. It extends the full length of the front of the glacier.” * This glacier presents many difficulties to explorers. A small party of Russian officers once attempted its explora- tion, and were never heard from again. Mr. Blake re- ports that, as usual with receding glaciers, a considerable * “American Journal of Science,’’ vol. xciv, 1867, pp. 96-101. - Casprayieg &q ydevisojoyg) *OpIM O[IU OUO JNOGB JO “JUOIJ OY} WOA JO VOYOIG AVY YVYY So10QooI SuIMOYS “BYSeLY “Jo[Ul NyVY, “OLOV[H SIMION—"LT “Ol GLACIERS ON THE PACIFIC COAST. m7 portion of the front as it spreads out in the valley is so coy- ered with bowlders, gravel, and mud that it is difficult to tell where the glacier really ends. But from the valley to the higher land it rises in precipitous, irregular, stair-like blocks, with smooth sides, and so large that it was impossible to sur- mount them with the ordinary equipment of explorers. The glacier is estimated to be about forty miles long. Another glacier, upon the opposite side of fhe river, of which Mr. Blake does not speak, was reported to me by those familiar with the country as coming down to within about two miles of the bank. The Indians are very likely correct in asserting that these two glaciers formerly met, compelling the Stickeen River to find its way to the sea through a vast tunnel. It would then have appeared simply as a subglacial! stream of great magnitude. North of the Stickeen River, glaciers of great size are of increasing frequency, and can be seen to good advantage from the excursion-steamer. The Auk and Patterson gla- ciers appear first, not far north of Fort Wrangel. On approaching Holkham Bay and Taku Inlet, about latitude 58°, the summer tourist has, in the numerous icebergs en- countered, pleasing evidence of the proximity of still greater glaciers coming down to the sea-level. Indeed, the glaciers of Taku Inlet are second only in interest to those of Glacier Bay, hereafter to be described more fully. In going from Juneau to Chilkat, at the head of Lynn Canal, a distance of about eighty miles, nineteen glaciers of large size are in full sight from the steamer’s deck, but none of them come down far enough to break off into the water and give birth to icebergs. The Davidson Glacier, however, comes down just to the water’s edge, and has there built up an immense terminal moraine all along its front. An illustration of the precipitous character of the south- eastern coast of Alaska is seen in the fact that it is only thirty-five miles from the head of Lynn Canal to the sources of the Yukon River, which then flows to the north and west for nearly three thousand miles before coming down to the sea- ie AN co \} a anti! ie mar Fig. 18.—Glacier Station, Selkir British Columbia. (Courtesy of the Canadian Pacific Railroad.) k Mountains, GLACIERS ON THE PACIFIC COAST. 29 level. Lieutenant Schwatka reports four glaciers of consider- able size in the course of this short portage between Chilkat and Lake Lindeman.* The vast region through which the Yukon flows to the north of these mountains is not known to contain any extensive glaciers. But the ground remains perpetually frozen at a short depth below the surface. Russell reports that in many places cliffs of ice abut upon the border of the Yukon on whose surface is a sufficient depth of soil Fie. 19.—Davidson Glacier, near Chilkat, Alaska, latitude 59° 45’. The mountains are from five thousand to seven thousand feet high ; the gorge about three quarters of a mile wide ; the front of the glacier, three miles; the ‘terminal moraine, about two hundred and fifty feet high. (View from two miles distant.) to support dense evergreen forests. Since the discovery of gold in the region a considerable population has entered, and certain forms of agriculture have begun to flourish. From Cross Sound, about latitude 58° and longitude 136° west from Greenwich, to the Alaskan Peninsula, the coast is bordered by a most magnificent semicircle of mountains, opening to the south, and extending for more than a thousand miles. Throughout this whole extent, glaciers of large size * “Science,” vol. iii (February 22, 1884), pp. 220-227. 30 THE ICE AGE IN NORTH AMERICA. are everywhere to be seen. Elliott estimates that, count- ing great and small, there can not be less than five thousand glaciers between Dixon’s Entrance and the extremity of the Alaskan Peninsula. The glaciers in the vicinity of Mt. St. Elias are the largest anywhere to be found on the continent. Numerous single glaciers, of which Seward is the largest, come down from the mountain range and, becoming confluent, unite to form the Malaspina glacier. This is a plateau of ice about 1,500 feet in height stretching all along the southern base of the St. Elias range for a distance of fifty miles, and covering an area of about a thousand square miles. In Icy Bay the gla- cier, comes down to sea-level, presenting a solid wall many miles in extent, which is continually breaking off into ice- bergs of great size. Far out upon the surface large forests occur surrounded by glacial ice. These are supported upon deep beds of gravel and sand which have been carried out by mountain streams whose channels have changed from time to time with the varying conditions of the surface of the ice. Lakes of considerable size are also found upon the surface at an altitude as high as 5,000 feet, with streams flowing between the ice and the mountain side, illustrating, possibly, the origin of many terraces of gravel on the flanks of moun- tains in the glaciated region of the United States. Such are to be noted on the flanks of both the Green and the Adiron- dack mountains, deposited originally on the sides of the mass of ice that filled the Champlain Valley. The glaciers of the St. Elias range are, however, mostly confined to the south side which is exposed to the sea breezes. Schwatka and Hayes who in 1892 made the tour of the range, coming out at Copper River, found the country free from glaciers and the climate so dry that they could comfort- ably sleep out of doors. The glaciers about the upper end of Yakutat Bay are of special interest because of the recent changes which have GLACIERS ON THE PACIFIC COAST. 31 taken place in them. The narrowing upper portion of the bay which is now bordered by the gravel deposits of the gla- cial streams pouring out from the southeastern portion of the Malaspina Glacier is called Disenchantment Bay. But above Haenke Island the depression turns at right angles sharply to the south and extends twenty-five miles between mountain ranges forming Russell Fiord. Into this fiord & “ — * Submerg *, « marking recent — _ =~ -great advance (?) — bea NX 2 q ae ‘ % ae , a Fa _— . ; SKETCH MAP OF GLACIER BAY AND MUIR GLACIER By HARRY FIELDING REID. a , A A ‘Gustavus F MILE SCALE 2 ILES Icy Strait 0 Svea 10 vir 136° 30’ 136° Hire, 22: the trees are of moderate size; but the islands and shores in the upper part of the bay are entirely devoid of forests. Willoughby Island, near the middle of the bay, is a bare rock, about two miles long and fifteen hundred feet high, showing glacial furrows and polishing from the bottom to the top. Several other smaller islands of similar character in this part of the bay show like signs of having been re- cently covered with glacial ice. The upper end of the bay is divided into two inlets of a “VT ee eS Lh ee i - — a eee a, ae ae a Se - A. MONTH WITH THE MUIR GLACIER. 45 unequal lengths, the western one being about four miles wide, and extending seven or eight miles (estimated) in the direction of the main axis of the bay to the northwest. The eastern, or Muir Inlet, is a little over three miles wide at its mouth, and extends to the north about the same distance, narrowing, at the upper end, to a little over one mile, where it is interrupted by the front of the Muir Glacier. The real opening between the mountains, however, is here a little over two miles wide, the upper part on the eastern side being oc- cupied with glacial débris covering a triangular space be- tween the water and the mountain about one mile wide at the ice-front and coming to a point three miles below, be- yond which a perpendicular wall of rock one thousand feet high rises directly from the water. The mountain on the west side of Muir Inlet, between it and the other fork of the bay, is 2,900 feet high. That on the east is 3,150 feet high, rising to about 5,000 feet two or three miles back. The base of these mountains consists of metamorphic slate, whose strata are very much contorted—so much so that it is difficult to ascertain their system of folds. Upon the summits of the mountains on both sides are remnants of blue crystalline limestone preserved in synclinal axes. In the terminal mo- raine deposited in front of the glacier on its eastern side are numerous bowlders of very pure white marble brought down in medial moraines from mountain valleys several miles to the east. Granitic bowlders are also abundant. The width of the ice where the glacier breaks through between the mountains is 10,664 feet—a little over two miles. But, as before remarked, the water-front is only about one mile. This front does not form a straight line, but terminates in an angle projecting about a quarter of a mile below the northeast and northwest corners of the inlet. The depth of the water three hundred yards south of the ice- front is (according to the measurement of Captain Hunter, of the steamer Idaho) 516 feet near the middle of the chan- nel; but it shoals rapidly toward the eastern shore. A meas- urement reported to me by Dr. Jackson, made in July, Q88T “JULISIP sojrur FT ‘oroys oy1s0ddo ’ 10 [OARIF PUL PULS POYT}eI}S FULP]IIOAO 99} PUT PUNOIFE10} UT OULEIOUT SurMoys ‘VyselV ‘JOPIVT) IMJ JO JUOIJ ss010e FUyYOOT—¢z “OT | ieee A MONTH WITH THE MUIR GLACIER. 47 1887, with the prow of the steamer within twenty feet of the ice-front, is one hundred and six fathoms (636 feet), and no bottom. According to my measurements, taken by level- ing up on the shore, the height of the ice at the extremity of the projecting angle in the middle of the inlet was 250 feet, and the front was perpendicular. Back a few hun- dred feet from the projecting point, and along the front nearer the shores, the perpendicular face of the ice was a lit- tle over 300 feet. A little farther back, on a line even with the shoulders of the mountains between which the glacier emerges to meet the water, the general height is 408 feet. From here the surface of the glacier rises toward the east and northeast about 100 feet to the mile. On going out in that direction on the ice seven miles (as near as I could estimate), I found myself, by the barometer, 1,050 feet above the bay. The main body of the glacier occupies a vast amphithea- tre, with diameters ranging from thirty to forty miles. This estimate was made from various views obtained from the _mountain-sunmits near its mouth, when points whose dis- tances were known in other directions were in sight. Nine main streams of ice unite to form the grand trunk of the glacier. These branches come from every direction north of the east-and-west line across the mouth of the glacier ; and no less than seventeen sub-branches can be seen coming in to join the main streams from the mountains near the rim of the amphitheatre, making twenty-six in all. Numerous rocky eminences also rise above the surface of the ice, like islands from the sea, corresponding to what are called nuna- taks in Greenland. The two of these visited, situated about four miles back from the front, showed that they had been recently covered with ice—their surfaces being smoothed and scored, and glacial débris being deposited everywhere upon them. Upon the side from which the ice approached . these islands (the stoss side) it rose, like breakers on the sea- shore, several hundred feet higher than it was immediately on the lee side. A short distance farther down on the lee side, however, the ice closes up to its normal height at that 48 THE ICE AGE IN NORTH AMERICA. point. In both instances, also, the lee side of these islands seemed to be the beginning of important subglacial streams of water—brooks running into them as into a funnel, and causing a backward movement of ice and moraine material, as where there is an eddy in water. In both these cases, however, the lee sides of these islands were those having greatest exposure to the sunshine. The surface of the ice immediately in front was depressed from one to two hun- dred feet below the general surface on the lee side. The ice in the eastern half of the amphitheatre is movy- ing much more slowly than that in the western half. Of this there are several indirect indications: First, the eastern surface is much smoother than the western. There is no difficulty in traversing the glacier for many miles to the east and northeast. Here and there the surface is interrupted by superficial streams of water occupying narrow, shallow chan- nels, running for a short distance and then plunging down into fissures, or, in technical language, mowlins, to swell the larger current, which may be heard rushing along in its im- petuous course far down beneath and out of sight. The ordinary light-colored bands in the ice parallel with its line of motion are everywhere conspicuous, and can be followed on the surface for long distances. When interrupted by cre- vasses they are seen to penetrate the ice for a depth of many feet, and sometimes to continue on the other side of a ere- vasse in a different line, as if having suffered a lateral fault. The color of the ice below the surface is an intense blue, and over the eastern portion this color characterized the most of the surface. Numerous holes in the ice, penetrating downward from an inch or two to several feet and filled with water, were encountered all over the eastern portion. Some- times there was a stone or a little dirt in the bottom of these, but frequently there was apparently nothing whatever in them but the purest of water. In the shallower inclosures on the surface, containing water and a little dirt, worms, about as large around as a small knitting-needle and an inch long, were abundant. —— ye A MONTH WITH THE MUIR GLACIER. 49 The character and course of the moraines on the eastern half of the glacier also attest its slower motion. There are seven medial moraines east of the north-and-south line, four of which come in to the main stream from the mountains to ~ the southeast (see Fig. 24). Near the rim of the glacial am- phitheatre these are long distances, in some cases miles, apart; but, as they approach the mouth of the amphitheatre, they are crowded closer and closer together near its eastern edge, until in the throat itself they are indistinguishably mingled. The three more southern moraines unite some dis- tance above the mouth. One of these contains a large amount of pure marble. This moraine gradually approaches the others on either side until the distance between them disappears, and its marble unites with the other material to form one common medial moraine. The fifth moraine from the south is about 150 yards in width, five miles back from the mouth. It is then certainly as much as five and prob- ably eight miles from the mountains from which the débris forming it is derived. All these moraines contain many large blocks of stone, some of which stand above the general mass on pedestals of ice, with a tendency always to fall over in the direction of the sun. One such block was twenty feet square and about the same height, standing on a pedestal of ice three or four feet high. It is the combination of these moraines, after they have been crowded together near the mouth, which forms the deposit now going on at the north- east angle of the inlet just in front of the ice. Of this more will be said in connection with the question of the recedence of the glacier. Similar phenomena, though on a smaller scale, appear near the southwest angle of the amphitheatre. The dominant streams of ice in the glacier come from the north and the northwest. These unite in the lower por- tion to form a main current, about one mile in width, which is moving toward the head of the inlet with great relative rapidity. Were not the water in the inlet deep enough to float the surplus ice away, there is no knowing how much farther down the valley the glacier would extend. The 50 THE ICE AGE IN NORTH AMERICA. streams of ice from the east and southwest have already spent the most of their force on reaching the head of the inlet; and, were it not for this central ice-stream, a natural equilibrium of forces would be established here independent — of the water, and no icebergs would be formed. The sur- face of this central current of motion is extremely rough, so that it is entirely out of the question to walk far out upon it. On approaching this portion of the glacier from the east the transverse crevasses diagonal to the line of motion increase in number and size until the whole surface is broken up into vast parallelograms, prisms, and towers of ice, sep- arated by yawning and impassable chasms scores and hun- dreds of feet in depth. Over this part of the ice the mo- raines are interrupted and drawn out into thinner lines, often appearing merely as patches of débris on separate masses of ice. This portion of the ice-current presents a lighter colored appearance than other portions, and the roughened lines.of motion can be followed, as far as the eye can reach, through distant openings in the mountains to the north and— the northwest. The comparative rapidity of the motion in this part of the ice is also manifest where it breaks off into the water at the head of the inlet. As already said, the perpendicular front of ice at the water’s edge is from 250 to 300 feet in height. From this front there is a constant succession of falls of ice into the water, accompanied by loud reports. Searcely ten minutes, either day or night, passed during the whole month without our being startled by such reports, and frequently they were like thunder-claps or the booming of cannon at the bombardment of a besieged city, and this, though our camp was two and a half miles below the ice- front. Sometimes this sound accompanied the actual fall of masses of ice from the front, while at other times it was merely from the formation of new crevasses or the enlarge- ment of old ones. Repeatedly I have seen vast columns of ice, extending up to the full height of the front, topple over and fall into the water. How far these columns extended A MONTH WITH THE MUIR GLACIER. ol below the water could not be told accurately, but I have seen bergs floating away which were certainly 500 feet in length. At other times masses would fall from near the summit breaking off part way down, and splashing the spray up to the very top of the ice, at least 250 feet. The total amount of ice thus falling off is enormous. Bergs several hundred feet long and nearly as broad, with a height of from twenty to sixty feet, were numerous and constantly floating out from the inlet. The steamer meets such bergs a hun- dred miles away. The smaller pieces of ice often so cover the water of the inlet two or three miles below the glacier that it is with great difficulty that a canoe can be pushed through them. One of the bergs measured, was sixty feet above water and about four hundred feet square. The por- tion above water was somewhat irregular, so that probably a symmetrical form thirty feet in height would have contained it. But even at this rate of calculation the total depth would be two hundred and forty feet. The cubical contents of the berg would then be almost 40,000,000 feet. Occa- sionally, when the tide and wind were favorable, the inlet would for a few hours be comparatively free from floating ice; at other times it would seem to be full. The movements of the glacier in its lower portions are probably facilitated by the subglacial streams issuing from the front. There are four of these of considerable size. Two emerge in the inlet itself, and come boiling up, one at each corner of the ice-front, making a perceptible current in the bay. There are also two emerging from under the ice where it passes the shoulders of the mountains forming the throat of the glacier. These spout up, like fountains, two or three feet, and make their way through a channel in the sand and gravel of the terminal moraine for about a mile, and enter the inlet 250 or 300 yards south of the ice- front. These streams are perhaps three feet deep and from twenty to forty feet wide, and the current is very strong, since they fall from 150 to 250 feet in their course of a mile. It is the action of the subglacial streams near the corners of 52 THE 1CE AGH IN NORTH AMERICA. the inlet which accounts for the more rapid recession of the glacier-front there than at the middle point projecting into the water south of the line joining the east and west corners. It was also noticeable that the falls of ice were much more frequent near these corners, and the main motion of the ice as afterward measured was, not toward the middle point projecting into the inlet, but toward these corners where the subglacial streams emerged below the water. No small dittculty was encountered in securing direct measurements of the motion; and, as the results may be questioned, I will give the data somewhat fuily. As it was impossible to cross the main current of the glacier, we were compelled to take our measurement by triangulation. But even then it seemed at first necessary to plant flags as far out on the ice as it was safe to venture. This was done on the second day of our stay, and a base-line was established on the eastern shore, about a mile above the mouth, and the necessary angles were taken. But, on returning to repeat the observations three or four days afterward, it was found that the ice was melting from the surface so fast that the stakes had fallen, and there were no means at command to make them secure. Besides, they were not far enough out to be of much service. It appeared also that the base-line was on a lateral moraine, which was, very likely, itself in motion. But by this time it had become evident that the masses of ice uniting to compose the main stream of motion retained their features so perfectly from day to day that there was no difficulty in recognizing many of them much farther out than it was possible to plant stakes. Accordingly, another base-line was established on the east side opposite the pro- jecting angle of ice in the inlet. From this position eight recognizable points in different portions of the ice-field were triangulated—the angles being taken with a sextant. Some of the points were triangulated on five different times, at inter- vals from the 11th of August to the 2d of September. Others were chosen later and triangulated a less number of times. The base-line finally chosen (marked B on Fig. 24) was at x —- es SS rl eS _— >». =. a ee a a es ee ee y= = 4 * | , » a i, il A MONTH WITH THE MUIR GLACIER. 53 the foot of the mountain exactly east by the compass from the projecting angle of ice in the inlet. The elevation of the base-line was 408 feet above tide—corresponding to that of the ice-front. The distance of this projecting point of ice (marked C on Fig. 24) from the base-line was 8,534 feet, and it remained very nearly stationary during the whole time—showing that the material breaking off from the ice- Sein? s, Drtet aote — beet (ite mas 9S! es =e i Mile ‘ Fie. 24.—Map of Muir Inlet, showing converging moraines, and form of front. Buried forest, A ; base of triangulation, B. 54 THE ICH AGE IN NORTH AMERICA. front was equal to that pushed along by the forward .move- ment. Satisfactory observations were made upon eight other points numbered and located on Fig. 24. No. 1 was a pinnacle of ice 1,476 feet north by 30° east from C. The movement from August 14th to August 24th was 1,653 feet east by 15° south. After this date the pinna- cle was no longer visible, having disappeared along the wast- ing line of front between C and the subglacial stream at the northeast corner of the inlet. This was so near the front as to be left out of the ordinary calculations. No. 2 was a conspicious pinnacle of ice 2,416 feet north by 16° east of C. Observations were continued upon this from August 11th to September 2d. The total distance moved during that time was 1,417 feet, or about sixty-five feet per day. From August 14th to August 24th the move- ment was 715 feet, or about seventy-one feet per day. The difference is, however, perhaps due to the neglect to record the hours of the day when the observations were taken. As these observations were wholly independent of each other, their substantial concordance demonstrates that there was no serious error in the observations themselves. The direction of movement of this point of ice was very nearly the same as that of the preceding, namely, east 16° south. This also is toward the subglacial stream emerging from the northeast corner of the inlet. No. 3 was observed only from August 20th to August 24th. It was situated 3,893 feet north by 62° east of C, and moved 105 feet in a westerly direction, about twenty-six feet per day. The westerly course of this movement probably arose from its being near where the easterly and northeast- erly currents joined the main movement. No. 4 was 5,115 feet north, 42° east of C, and moved from August 20th to August 24th 143 feet in a southeast- erly direction, or thirty-six feet per day. No. 5 was 5,580 feet north, 48° east of C, and moved 289 feet from August 20th to August 24th in a direction east by 39° south, or seventy-two feet per day. A MONTH WITH THE MUIR GLACIER. ay) No. 6 was 5,473 feet north, 70° east of C, and moved 232 feet from August 11th to September 2d in a direction south 66° east, or ten feet per day. No. 7 was 6.903 feet north, 59° east of C, and moved 89 feet between August 14th and August 24th, in a direction south 3° east, about nine feet per day. No. 8 was 7,507 feet north, 62° east of C, and moved 265 feet from August 14th to August 24th, in direction south 56° east. These last three points lay in one of the moraines on the east side of the line of greatest motion and parallel with it. These moraines are much interrupted in their course by gaps. It is observable that these points are all east of the center of the main line of most rapid motion, and are tending with varying velocity toward the northeast corner of the inlet, where the powerful subglacial stream emerges from below the water-level. Doubtless, on the other side of the center of motion, and at the same relative distance from the front, the ice would be found tending toward the northwest corner of the inlet, where a similar subglacial stream emerges. From these observations it would seem to follow that a stream of ice presenting a cross-section of about 5,000,000 square feet (5,000 feet wide by about 1,000 feet deep) is entering the inlet at an average rate of forty feet per day (seventy feet in the center and ten feet near the margin of movement), making about 200,000,000 of cubic feet per day during the month of August. The preceding remarks upon the many indirect evidences of rapid motion render the cal- culation perfectly credible. What the rate may be at other times of the year there are at present no means of knowing. The indications that the glacier is receding, and that its volume is diminishing, are indubitable and numerous. The islands of southern Alaska are ordinarily covered with forests of cedar, hemlock, and fir, up to the level of 1,500 or 2,000 feet above tide. But to this rule the shores and islands of the upper part of Glacier Bay are a striking exception. Near the mouth of the bay, forests continue to occur as in other : Cospinseg Aq ydeisojoyg) 9dr peloels YIM popunosms st OTPPIe oY} UT UreJUNOTE oy} t Ave sorrt AyUWOMy IR ae dT] Ul SULRJUNOUE 9Y} $ 4YSII oY) 0} SI JOIOBl[s ureuT oy) $ AIVINGIIy B SI YJoT OY OF TOOB[6 OY], “AULVIOUL [VIPIUL B PUB SAsSBAIIO [BUOSRIP OY] SUIMOYS ‘JUOIJ oY WOIJ Yowg ow B Jo toJIBUbD 9uUO “IIIV[H UNA Jo vovjaung—egy “oy K'N-02 ONT OL0Ha A MONTH WITH THE MUIR GLACIER. a7 parts, only on a diminished scale; but in the upper half of the bay all the shores and islands are perfectly bare of forests, and the rocks retain in the most exposed situations fresh grooves and striz of glacial origin. It would be impossible for rocks so exposed in such a climate to retain these for an indefinite length of time. Far up on the mountains, also, there are remnants of glacial débris in situations such that the material could not have resisted erosive agencies for any great length of time. The triangular-shaped terminal moraine on the eastern side, just below the ice-front, presents some interesting features bearing on the same point. This extends three miles below the glacier, and in its lower portions is thinly covered with vegetation. This covering becomes less and Jess abundant as the glacier is approached, until, over the last mile, scarcely any plants at all can be found. Apparently this is because there has not been time for vegetation to spread over the upper portion of the moraine since the ice withdrew, for on the mountains close by, where the exposure has been longer, there is a complete metting of grass, flower- ing plants, and shrubs. Again, in this triangular moraine- covered space there are five distinct transverse ridges, mark- ing as many stages in the recession of the ice-front (see Fig. 24). These moraines of retrocession run parallel with the ice-front on that side, and at about equal distances from each other, each one rising from the water’s edge to the foot of the mountain, where they are 408 feet above tide. An inspec- tion of the upper moraine-ridge shows the manner of its for- mation. ‘This transverse ridge is half a mile below the ice- front, and is still underlaid in some portions with masses of ice ninety feet or more in thickness, which are melting away on their sides and allowing the débris covering them to slide down about their bases. Kettle-holes are in all stages of for- mation along this ridge. The subglacial stream emerging from the southeast corner of the glacier next the mountain rushes along just in the rear of this moraine-ridge, and in front of a similar deposit in process of formation on the very edge of the ice where the medial moraines spoken of termi- 58 THE ICE AGE IN NORTH AMERICA. nate. Eventually this stream will break out in the rear of that deposit also, and leave another ridge similar to the one Fie. 26.—In the foreground on the right is a mass of ice, one half mile in front of the gla- cier, one hundred or more feet thick, covered with gravel, slowly sliding down to form the rim of a kettle-hole. The mountain back is 3,100 feet high. Near B, Fig. 22. now slowly settling down into position south of it. This first ridge south of the subglacial stream, with its ice still melting in exposed positions under its covering of gravel, can not be many years old. Still another sign of the recent date of this whole moraine appears at various places where water-courses, coming down from the mountain, are depositing superficial deltas of débris upon the edge of the glacial deposit. These deltas are very limited in extent, though the annual deposition is by no means insignificant. At the southern apex of the moraine, three miles below the ice-front, and but one hundred or two hundred yards from our camp, great quantities of débras came tearing down in repeated avalanches during a prolonged sea- son of rain. Twenty-five years would be more than ample for the formation of the cone of débris at the foot of this line of avalanches. Thus there can be no reasonable doubt that eS Se eC A MONTH WITH THE MUIR GLACIER. 99 during the earlier part of this century the ice filled the inlet several miles farther down than now. And there can be scarcely less doubt that recently the glacier filled the inlet, 2,500 feet above its present level near the front; for the elacial débris and striz are very marked and fresh on both mountains flanking the upper part of the inlet up to that height, and the evidences of an ice-movement in the direction of the axis of the bay are not wanting as high as 3,700 feet on the eastern mountain, where I found fresh striz running north by south, and directly past the summit, which rises 1,000 or 1,500 feet still higher, just to the east. To this circumstantial evidence may be added what seems to be an irresistible inference from the notes of Vancouver's party in 1794. This party entered Cross Sound in small boats, and penetrated as far as the head of Lynn Canal and Juneau. The following is the record. Weshould premise, how- ever, that the point referred to as seven miles from Point Dundas is probably that at the southeastern corner of Gla- cier Bay, and the “spacious inlet lying in an east-southeast ” direction is probably the channel extending toward Chatham Strait. But certainly, no one looking from that point at the present time would speak, as this report does, of this inlet as seeming to be “entirely occupied by one compact sheet of ice as far back as the eye could distinguish.” Nor would the observer at the present time say that, to the north and east, the two large open bays formed by the shores of the continent seemed to be “‘ terminated by compact solid mount- ains of ice rising perpendicular from the water’s edge.” The ice is now full twenty-five miles away from that point, and the ice-front is not sufficiently prominent to make such an impression as this. It is hence more than probable that, at that time, the ice extended down nearly to the mouth of the bay. The morning of the 12th [July], though unpleasant, was rather more favorable to their pursuit, which was still greatly led ‘ 60 THE ICE AGE IN NORTH AMERICA. impeded by the ice. From the east point of this branch, which I have called Point Dundas, situated in latitude 58° 21’, longitude 224° 1’, the coast takes an irregular east-northeast direction about seven miles to a point whence this branch of the [Cross] Sound appeared to be very extensive in an east- southeast point of view, and was upward of three leagues across. The party proceeded from Point Dundas to this station, through a channel from two to three miles in width, between the continental shore and an island about seven miles long and three miles broad, lying in a northeast and southwest di- rection. This spacious inlet presented to our party an ardu- ous task, as the space between the shores on the northern and southern sides seemed to be entirely occupied by one compact sheet of ice as far as the eye could distinguish. ... To the north and east of this point the shores of the continent form two large open bays, which were terminated by compact solid mountains of ice, rising perpendicularly from the water’s edge, and bounded to the north by a continuation of the united lofty frozen mountains that extend eastward from Mount Fair- weather. In these bays also were great quantities of broken ice, which, having been put in motion by the springing up of a northerly wind, was drifted to the southward, and, forcing the boats from the northern shore, obliged them to take shel- ter round the northeast point of the above island. ‘This made Mr. Whidbey apprehensive that the still apparent connected body of ice, from side to side, would at length oblige him to abandon his researches by this route, unless he should find it possible to force a passage through this formidable obstruc- tion. In attempting this, the party succeeded far beyond their expectations, for they gained an open navigation, and by four in the afternoon arrived at a low and nearly round island about two leagues in circuit, lying from the former island north 83° east, distant three leagues. This island is moder- ately elevated, its shores pleasant and easy of access, and well stocked with timber, mostly of the pine tribe. It presented a much more inviting appearance than they had been accustomed to behold, and the weather being more favorable than for some time past, they continued along the continental shore, A MONTH WITH THE MUIR GLACIER. 61 passing within some islets that lie about a league to the east- ward of the round island, until nine in the evening, when it became calm, and the party rested for the night at the entrance of a brook, ina bay on the northern or continental shore, which from the round island les south 82° east, distant ten miles. * If we understand this, the bay to the north is Glacier Bay, down which the ice must then have extended south of Willoughby Island and to within a few miles of Cross Sound. Otherwise no such description could have been given. The bay to the east is probably the extension of the sound toward the mouth of Lynn Canal, and very likely glaciers at that time came down toward the west from the White Mountains and produced the appearance described. From what has already been said of the evidence showing the present recession of the Muir Glacier, it is not at all incredible that glaciers nearly filled the whole bay a hundred years ago. All this is necessary to a comprehension of a most inter- esting problem presented by the buried forests near the south- west corner of the glacier (see A, Fig. 24). Below this corner, and extending for about a mile and a half, there is a gravel deposit, similar to that on the eastern side, except that it is not marked by transverse ridges, but is level-topped, rising gradually from about 100 feet at its southern termination to a little over 300 feet where it extends north and west of the ice-front (see Fig. 24). The subglacial stream entering the inlet just below the southwest corner of the ice emerges from the ice about a mile farther up, on the north side of the pro- jecting shoulder of the western mountain which forms that side of the gateway through which the glacier enters the in- let. This stream comes principally from the decaying western branch of the glacier before alluded to, and, after winding around the projecting shoulder of the mountain, which is 315 feet above tide, has worn a channel through the gravel * ““ Voyage of Discovery around the World,” vol. v, pp. 420-423. 62 THE ICE AGE IN NORTH AMERICA. deposit lying between the lower mile of the glacier and the mountain a short distance to the southwest. About half-way down, a small brook, coming from between this latter mount- ain and that whose shoulder forms the western part of the gateway just north of it, joins the main stream issuing from the glacier on this side. Where these streams unite, at A, they are now uncovering a forest of cedar-trees in perfect preservation, standing upright in the soil in which they Fic. 27—Buried Forest on the Muir Glacier, looking west. grew, with the Awmus still about their roots. An abundance of their cones, still preserving their shape, lies about their roots ; and the texture of the wood is still unimpaired. One of these upright trunks measured ten feet in cireumference about fifteen feet above the roots. Some of the smaller up- right trees have their branches and twigs still intact, pre- serving the normal conical appearance of a recently dead cedar-tree. These trees are in various stages of exposure. Some of ie } i 4 i d tig WR = A MONTH WITH THE MUIR GLACIER. 63 them are uncovered to the roots ; some are washed wholly out of the soil; while others are still buried and standing upright, in horizontal layers of fine sand and gravel, some with tops projecting from a depth of twenty or thirty feet, others being doubtless entirely covered. The roots of these trees are in a compact, stiff clay stratum, blue in color, without grit, inter- sected by numerous minute rootlets, and which is, in places, twenty feet thick. There is also, occasionaily, in this sub- Fie. 28.—Shows stumps of trees on east side of the glacial torrent. Note the line of sep- aration between the enveloping sand and the soil in which the roots are imbedded. A stump appears on the right, split in two, but one half standing. The gravel corre- sponds in height with that on the west side. The glacier appears in the background on the right. (From photograph, looking north.) stratum of clay, a small fragment of wood, as well as some smooth pebbles from an inch to two feet in diameter. The surface of this substratum is at this point 85 feet above the inlet. The deposit of sand and gravel covering the forest rises 115 feet higher, and is level-topped at that height, but rising toward the north till it reaches the shoulder of the mountain at an elevation of 300 feet. The trees are essen- tially like those now growing on the Alaskan mountains. Many of them have been violently broken off from five to 64. THE ICE AGE IN NORTH AMERICA. twenty feet above their roots. This has been done by some force that has battered them from the upper side at the point of fracture. Evidently cakes of ice brought down by the streams indicated in the map, when flowing at various high- er levels than now, have accomplished this result; for the trunks in the main stream were battered on the north side, while those in the gully worn by the lateral stream were bat- tered from the west side. From this description the explanation would seem to be evident. At some period, when the ice occupied only the upper part of the valley to the north of this point, forests: grew over all the space lying southwest of the present ice- front. As the ice advanced to near its present position, the streams carrying off the surplus water from the western half of the advancing glacier were suddenly turned into the pro- tected space occupied by this forest, where they deposited their loads of sand and gravel. A cause very likely com- bining to facilitate deposition in this spot has not yet been spoken of, but is evident from a glance at the maps. A trans- verse valley passes just below this point from Muir Inlet to the western inlet into which Glacier Bay divides. This transverse valley is at present occupied by a decaying glacier opening into both inlets, and sending a subglacial stream through a long, narrow series of moraines, into Muir Inlet about two miles to the south. Now, when a general advance of the ice was in progress, this transverse glacier probably pushed itself down into the inlet across the path of the ice moving from the north, and so formed an obstruction to the water running from the southwest corner of the main glacier, thus favoring the rapid deposition which so evidently took place. When this inclosed place was filled up, and the ad- vancing ice had risen above and surmounted the projecting shoulder of the mountain just to the north, that rocky barrier protected a portion of the forest from the force of the ice- movement, causing the ice to move some distance over the top of the superincumbent gravel before exerting its full downward force. Thus sealed up on the lee side of this pro- A MONTH WITH THE MUIR. GLACIER. 65 tecting ridge of rock, there would seem to be no limit to the length of time the forest might be preserved. I see no rea- son why this forest may not have existed before the Glacial period itself. | The existence of other forests similarly preserved in that vicinity is amply witnessed to by many facts. One upon the island near the west shore, four miles south, is now exposed in a similarly protected position. J*urthermore, the moraine, already described on the east side of the inlet, contains much wood ground up into slivers and fragments. Indeed, our whole dependence during the month for fuel was upon such fragments lying exposed in the moraine. Occasional chunks of peat or compact masses of sphagnum formed a part of the débris of this moraine. These also occurred on some of the pric rT Gia oar cae eae alc Peal ag, Fig. 29—Muir Glacier from an elevation of 1,800 feet. medial moraines on the eastern side. I did not go up them far enough to learn directly their origin ; but, as no forests 66 THE ICE AGE IN NORTH AMERICA. were visible anywhere in that direction, it is presumable that they had been recently excavated from preglacial forests simi- lar in situation to that now exposed on the west below the ice-front. The capacity of the ice to move, without disturbing them, over such gravel deposits as covered the forests, is seen also in the present condition of the southwestern corner of the glacier itself. As the ice-front has retreated along that shore, large masses of ice are still to be seen lapping over upon the gravel. These are portions of the glacier still sus- tained in place by the underlying gravel, while the water of the mlet has carried the ice from the perpendicular bank clear away. This phenomenon, and that of the general per- pendicular front presented by the ice at the water’s edge, accord with the well-known fact that the surface of the ice moves faster than the lower portions. Otherwise the ice- columns at the front would not fall over into the water as they do. The formation of kames, and of the knobs and kettle- holes characteristic both of kames and of terminal moraines, is illustrated in various places about the mouth of Muir Gla- cier, but especially near the southwest corner, just above the shoulder of the mountain where the last lateral branch comes in from the west. This branch is retreating, and has already begun to separate from the main glacier at its lower side, where the subglacial stream passing the buried forest etnerges. Here a vast amount of water-worn débris covers the ice, ex- tending up the glacier in the line of motion for a long dis- tance. It is evident from the situation that, when the ice- stream was a little fuller than now, and the subglacial stream emerged considerably farther down, a great mass of débras was spread out on the ice at an elevation considerably above the bottom. Now that the front is retreating, this subglacial stream occupies a long tunnel, twenty-five or thirty feet high, in a stratum of ice that is overlaid to a depth, in some places, of fifteen or twenty feet with water-worn glacial débris. In numerous places the roof of this tunnel has broken in, and —————————— Oe ~~ = = SS ? A MONTH WITH THE MUIR GLACIER. 67 the tunnel itself is now deserted for some distance by the stream, so that the debris is caving down into the bed of the old tunnel as the edges of ice melt away, thus forming a tortuous ridge, with projecting knolls where the funnels into the tunnel are oldest and largest. At the same time, the ice on the sides at some distance from the tunnel, where the superficial débrzs was thinner, has melted down much below the level of that which was protected by the thicker deposit ; and so the débr’s is sliding down the sides as well as into the tunnel through the center. Thus three ridges approximateiy parallel are simultaneously forming—one in the middle of the tunnel and one on each side. When the ice has fully melted away, this débris will present all the complications of interlacing ridges, with numerous kettle-holes and knobs characterizing the kames; and these will be approximately parallel with the line of glacial motion. The same condition of things exists about the head of the subglacial stream on the east side, also near the junction of the first branch glacier on the east with the main stream, as also about the mouth of the independent glacier shown on the map lower down on the west side of the inlet (see Fig. 24). The formation of kettle- holes in the terminal ridges has already been referred to. Considerable earthy material is carried out from the front by the bergs. Pebbles and dirt were frequently seen frozen into them as they were floating away. Just how many of the bergs were formed from ice that originally rested on the bot- tom of the inlet I have no means of telling. That some were so formed seems exceedingly probable, if for no other reasons because of the great amount of débris that was sometimes seen frozen into them. It is by no means certain that the subglacial streams boiling up near the upper corners of the inlet were beneath the lowest stratum of ice. Some small streams were seen pouring out from the face of the ice half- way up from the water. It seems likely that a great amount of sediment is conveyed into cavities in the center of the glacier through the action of these subglacial streams; and so is ready for transportation when the masses break loose. 6S THE ICE AGE IN NORTH AMERICA. My estimates concerning the amount of sediment carried out by subglacial streams are as follows: The amount of sedi- ment contained in each United States gallon (23i cubic inches) of water collected from the subglacial streams is, as deter- mined by the analysis of the late Professor H. OC. Foote, of Cleveland, 708-48 grains. Estimating the total area oceupied by the glacial amphitheatre to be 1,200 square miles, and the annual precipitation the same as that at Sitka (which is not far from ninety-six inches), the total amount of water which must in some form annually pass into the inlet from this area is 267,632,640,000 eubic feet. Of this amount I estimate that 77,088,000,000 cubic feet passes out as ice, or, reducing this to water, about 67,000,000,000 eubic feet of liquid water. (This part of the calculation is based on.the fact approximate- ly ascertained that a section of ice one mile wide and 1,000 feet deep is moving into the inlet at a rate of 40 feet per day.) Subtracting the ice from the total amount, and esti- mating that evaporation would probably diminish the amount one eighth, the total amount of water which must issue in all the subglacial streams from this glacier is 175,000,000,000 cubic feet. Estimating the specific gravity of the sediment (which is chiefly some compound of alumina and silica) at two and a half, we have, as the total amount of sediment transported thus, 33,274,804 cubic yards. This equals not far from one third of an inch per year eroded from the total © area (1,200 square miles) occupied by the glacier. This would furnish one inch of sediment per year to be spread by this single glacier over the bottom of Glacier Bay. This confirms the statements concerning the recent recession of the glacier from the lower portion of the bay, since otherwise it would now be full of sediment. Besides the Muir Glacier several others of large size, such as the Grand Pacific and Hugh Miller Glaciers, descend from the flanks of Mts. Crillon and Fairweather into Reid Inlet, which projects several miles to the northwest from Glacier Bay. These do not differ materially in appearance and behavior from the Muir Glacier. A MONTH WITH THE MUIR GLACIER. 69 I append the record of the thermometer from August 20th to August 31st, giving the mean of three readings each day taken at 84.m,2p.m,and8p.m. The temperature of the water in the upper part of the inlet was uniformly 40° Fahr. August 20, 49°4° Fabr. | August 24, 49°8° Fahr. | August 28, 50°5° Fahr. August 21, 48°9° Fahr. | August 25, 52°7° Fahr. | August 29, 45° Fahr. August 22, 46-1° Fahr. | August 26, 51-9° Fahr. | August 30, 54-8° Fahr. August 23, 44°6° Fahr. | August 27, 46-1° Fahr. | August 31, 50°5° Fabr. The following is the list of plants, as identified by Pro- fessor Asa Gray, found in bloom about Muir Inlet during the month of August. Where the altitude is not given, they were found near the tide: Arabis ambigua, Brong..........-..-.--- August 26, 1,600 A. T. Arxenaria peploides, L......-..22..22. .. August 28. pienrelas alpings, L.........2552.0. 20-5 August 7. Hedysarnm boreale, Nutt..............-. August 28. Sanguisorba Canadensis. ........... .... August 6. Lutkea sibbaldioides, Brong.............. August 27. Saxifraga Lyalli, Engl. .......... _...... August 26. 1,600 A. T. Saxifraga stellaris, L........ ethan ain. August 27, 3,000 A. T. Parnassia fimbriata, Smal]............... August 27, 3,000 A. T. BEM MMNOREATS, De. se te oe August 6. Epilobium latifolium, L.................- August 6, 1,600 A. T. Epilobium origanifolium Lam. (?)......... August 28. | Solidago multiradiata, Ait... .......-.... Augnst 27. Erigeron salsuginosus. Gray, arctic form.. August 27, 3,000 A. T. Antennaria margaritacea, arctic form... .. August 27. Achillea millefolium, L., arctic variety.... August 27. arms obtustiolin, Les.....00..-.-.-5 -- August 27, 1,200 A. T. Campanula rotundifolia, L., var. Alaskana. August 23. Gentiana platypetala (7)..... siete pean eat August 27. Gentiana Menviesi (7)... .......-.....-.- August 27. Mioreras ingrisiin: o.oo sb. 2 ele August 7. Castilleja parviflora, Brong.............- August 28. OTS ee a) a eo a Augnst 6. Habenaria hyperborea, R. Br............ August 27, 2,650 A. T. Luzula parviflora, Meyer. Poa alpina, variety vivipara.............- August 26, 1,500 A. T. RUMEN OS elle tite Siu wishin e o 4 o = = August 26, 1,600 A. T. So Sy Se Ee ee August 26, 1,500 A. T. 70 THE {CH AGE IN NORTH AMERICA. Phleum: alpinum Wis. ete enna. 8 a August 26, 1,600 A. 'I. Helyaus* ca ols. cide ocho nis | eect 3 August 6. Herdeumi, ssp: /()e sc steers esteieie es O06: 07s August 6. eel Fie. 30.—Blocks of stone supported on ice-pillars, showing how they fall toward the sun. See above, page 49. United States Geological Survey (Russell). A MONTH WITH THE MUIR GLACIER. 71 SUPPLEMENT TO CHAPTER III. For various reasons it is best to let this chapter stand as it was originally written. But it is necessary to append a summary of the results of subsequent observations by others, especially as they have a most important bearing on several questions of glacial theory. During the summers of 1890 and 1892 Professor Harry Fielding Reid with a corps of competent assistants carefully surveyed the region and made extensive additions to our knowledge, not only of this glacier, but of glacial movements in general. The main facts, as determined by Professor Reid, do not, however, differ materially from ours. Our estimate of twelve hundred square miles for the area of the Muir Glacier would, by his calculations, be brought down to a thousand square miles. He failed, however, to detect any motion in the glacier greater than about ten feet per day. But it should be noted that he did not measure the central, and consequently most rapidly moving portion of the ice, but limited himself to calculating the motion of those portions of the ice which he could traverse, and upon which he could plant flags of observation. Thus, not- withstanding his utmost efforts, in going out from both direc- tions, about a quarter of a mile in width, as he informs me, re- mained untraversed, and his attempts to take angles, after the method pursued by us, upon the masses of ice themselves, failed of success. This was probably due to the fact that his base- line (near B in our map on page 53) was eight hundred feet higher upon the mountain than ours, so that he did not have the advantage which we had of seeing the domes and pinnacles of the central and higher portion of the ice projected upon the sky and the dark background of the mountains beyond. Hence it does not appear that there is any occasion to question the ap- proximate correctness of our figures as given on page 64. If, how- ever, I were to revise the estimates of the average rate of move- ment in the mass of ice, I should not place it quite so high as I have done on page 585, especially since in that calculation no allowance was made for the decrease of velocity toward the bottom. Taking this into account, together with the com- 72 THE ICE AGE IN NORTH AMERICA. parative narrowness of the area of most rapid motion, the average movement of the mass is probably not over twenty feet per day, and this amount would perhaps account for the number of bergs floating away with the tide, especially — since now we must add to them the amount supplied by the recession of the front of the ice. With reference to the evidence of the recent recession of the glacier Professor Reid agrees entirely with me. By com- parison of his photographs with mine he found that in ‘‘the four years from 1886 to 1890 the western end of the ice front has receded. 1,200 yards and the eastern end 750 yards. The center also has receded about 1,000 yards, so that the average recession of the ice front is a little over 1,000 yards in the four years, or, say a mile in seven years . . . . It does not seem at all incredible that the ice from the various glaciers of Glacier Bay may have united to fill a large part of the bay 100 years ago.” But it is no longer necessary to depend on this evidence alone. In 1906 Messrs. F. E. and C. W. Wright made an official investigation of the region with the following startling results. On comparing their map with that of Professor Reid made in 1892 they write that: Beginning with Muir Glacier and its tributaries the ice front has receded a maximum distance of 33,000 feet; Dirt Glacier is no longer tidal; White and Adams Glaciers are supplying very little ice to the general ice field; Morse Glacier terminus is about one mile from tide water . . . . Girdled Glacier and Berg Lake have not changed materially in aspect. The length of the total ice front of Muir Glacier is now over 40,000 feet instead of 9,000 feet in 1892. The present ice front passes at its northern extremity at about the position of your 1,000 foot contour on the ice of 1892. This remarkable decrease in elevation is undoubtedly due not only to melting down but also to breaking down of the exposed ice masses. The ascent of the ice mass at this point is decidedly steep and the ice fairly cascades into the water. The present height of the ice fronts of all the tide water glaciers is about the same A MONTH WITH THE MUIR GLACIER. 73 as noted by you in 1892 (150-250 feet), and is a noteworthy fact in connection with these glaciers. Muir Inlet is at present choked by the ice pack which promises to remain. congested so long as its source of supply is so active. A considerable portion of the present front of Muir Glacier is in very shallow water and in a few years should decrease in size very materially unless new avenues and inlets for tidal currents are exposed by the receding ice. Dying Glacier is still creeping back and wasting away. Carroll Glacier has not changed much in aspect during the last fourteen years; its terminal cliff has receded about 2,000 feet and at present, apparently, is continuing to do so. It is discharging icebergs very slowly and Queen Inlet is nearly | free of ice. Rendu Glacier has also changed but little, and its front is about 2,000 feet back of its position in 1892. This inlet also is not impeded by any amount of ice. The small glacier cas- cading from the west near its terminus appears to have changed still less. In Reid Inlet the changes have been very great and things are still moving at arapid rate there. The inlet was congested with the ice pack last summer (1906) and on the south side near the large island the ice jam was completely frozen over and moved as one mass back and forth with the tides. Grand Pacific Glacier has receded and left the large granite island surrounded by water. It has receded nearly 20,000 feet; but judging from the amount of ice it is now discharging and the shape of its valley it will not recede so rapidly in the next few years, other conditions remaining the same. Johns Hopkins Glacier has receded about 11,000 feet and is still sending off icebergs at arapid rate. The unnamed glacier directly east has become detached from it and is much like Reid Glacier in character and appearance. Reid Glacier has receded perhaps 5,000 feet and still preserves its original aspect as indicated on yourmap . Hugh Miller Glacier no longer reaches tide water in Heid Inlet and at low tide is nearly a mile back from it. The tide flats are long and with only a slight grade. In Hugh Miller 74 THE ICE AGE IN NORTH AMERICA. Inlet this glacier was exposed to tide water only in the south- western bay, where its front is intercepted in its central part by a large promontory of light colored granite. Eight thou- sand feet is approximately its recession since 1892. Charpen- tier Glacier also receded about 9,000 feet and promises to con- tinue its recession rapidly, especially along its southern front, as its valley is opening out and allowing a greater exposure of ice front to the action of tide water. The small stagnant glacier east of Charpentier is simply melting away and will probably disappear in ten or twenty years. Favorite Glacier is still receding. Wood Glacier is no longer tidal and only a small part of Geikie Glacier ice front is exposed to salt water. Geikie Glacier has receded about 5,000 feet during the past fourteen years. On the whole, recession has been the rule for the glaciers of Glacier Bay. Those glaciers have receded most whose fronts have, on recession, increased appreciably in length. In the past fourteen years the combined ice front of all the glaciers exposed to the tide water has increased from 17,000 feet to over 40,000 feet and the amount of recession has in that time alone equalled that of the previous twenty years. To the west of Glacier Bay, Brady Glacier in Taylor Bay has receded considerably. In Lituya Bay, the glacier at the northwestern end of the bay has advanced about one-half mile since 1894; the central and southeastern glaciers have apparently remained unchanged although the latter may have advanced slightly.* *H.F. Reid: ‘Variation of Glaciers,’’ xii, ‘‘Journal of Geology,”’ Xvi, pp. 52, 53. 4 =) Puats V—Muir Glacier in 1909. CHAPTER IV. ‘THE GLACIERS OF GREENLAND. THE continental proportions of Greenland, and the ex- tent to which its area is covered by glacial ice, make it by far the most important accessible field for glacial observa- tions. The total area of Greenland can not be less than 500,- 060 square miles—equal in extent to the portion of the United States east of the Mississippi and north of the Ohio. It is now pretty evident that the whole of this area, except a narrow border about the southern end, is covered by one continuous sheet of moving ice, pressing outward on every side toward the open water of the surrounding seas. For a long time it was the belief of many that a large region in the interior of Greenland was free from ice, and was perhaps inhabited. It was in part to solve this problem that Baron Nordenskidld set out upon his expedition of 1883. Ascending the ice-sheet from Disco Bay, in latitude 69°, he proceeded eastward for eighteen days across a con- tinuous ice-field. Rivers were flowing in channels upon the surface like those cut on land in horizontal strata of shale or sandstone, only that the pure deep blue of the ice-walls were, by comparison, infinitely more beautiful. These rivers were not, however, perfectly continuous. After flowing for a dis- tance in channels on the surface, they, one and all, plunged with deafening roar into some yawning crevasse, to find their way to the sea through subglacial channels. Numerous lakes with shores of ice were also encountered. “On bending down the ear to the ice,” says this explorer, “we could hear on every side a peculiar subterranean hum, Length of the [ce-Sheet, 1500 milek, maximum width, 700 miles; area,about 574,000 eguare miles; altitude pf its central fragt, 6,000 to 10,000 feet ahove the sea. C8 PEARY, 1886 Godhavit\-4 Gtobshavn Disco es: Egedesmin® Aa |, ave nsSiOL A 183s ooo” ad &. Strim Fa.& SS. a . ? a Drona His Pcape aa ukkertoppen®, A HH | ‘Pinilik Fiord cP) Paton Ge a “Ne NATAKS * OMe sews se, — = = *, 30 —T00 200 300 Pr “Scale of Miles. 40 30 Fre. 31—Map of Greenland showing narrow margin free from ice. THE GLACIERS OF GREENLAND. 77 proceeding from rivers flowing within the ice; and occasion- ally a loud single report like that of a cannon gave notice of the formation of a new glacier-cleft. . . . In the afternoon - we saw at some distance from us a well-defined pillar of mist which, when we approached it, appeared to rise from a bot- tomless abyss, into which a mighty glacier-river fell. The vast roaring water-mass had bored for itself a vertical hole, probably down to the rock, certainly more than 2,000 feet beneath, on which the glacier rested.” * At the end of the eighteen days, Nordenskidld found himself about 150 miles from his starting-point, and about 5,000 feet above the sea. Here the party rested, and sent two Eskimos forward on skidor—a kind of long wooden skate, with which they could move rapidly over the ice, not- withstanding the numerous small circular holes which every- where pitted the surface. These Eskimos were gone fifty- seven hours, having slept only four hours of the period. It is estimated that they made about 75 miles, and attained an altitude of 6,000 feet. The ice is reported as rising in distinct terraces, and as seemingly boundless beyond. If this is the ease 225 miles from Disco Bay, there would seem little hope of finding in Greenland an interior freed from ice. So we may pretty confidently speak of that continental body of land as still enveloped in an ice-sheet. Up to about latitude 75°, however, the continent is fringed by a border of islands, over which there is no continnous covering of ice. In south Greenland the continuous ice-sheet is reached about thirty miles back from the shore. , In 1886 Dr. Rink wrote: We are now able to demonstrate that a movement of ice from the central regions of Greenland to the coast continually goes on, and must be supposed to act upon the ground over which it is pushed, so as to detach and transport fragments of it for such a distance. . . . The plainest idea of the ice-forma- tion here in question is given by comparing it with an inunda- * “Geological Magazine,” vol. ix, pp. 393, 399. 78 THE ICE AGE IN NORTH AMERICA. tion. . . . Only the marginal part shows irregularity ; toward the interior the surface grows more and more level, and passes into a plain very slightly rising in the same direction. It has been proved that, ascending its extreme verge, where it has spread like a lava-stream over the lower ground in front of it, the irregularities are chiefly met with up to a height of 2,000 feet, but the distance from the margin in which the height is reached varies much. While under 683° north latitude, it took twenty-four miles before this elevation was attained ; in 623° the same height was arrived at in half the distance. . . . A general movement of the whole mass from the central re- gions toward the sea is still continued, but it concentrates its force to comparatively few points in the most extraordinary degree. These points are represented by the ice-fiords, through which the annual surplus ice is carried off in the shape of bergs. . . - In Danish Greenland are found five of the first, four of the second, and eight of the third (or least productive) class, besides a number of inlets which only receive insignificant fragments. Direct measurements of the velocity have now been applied on three first-rate and one second-rate fiords, all situated between 69° and 71° north latitude. 'The measure- ments have been repeated during the coldest and the warmest season, and connected with surveying and other investigations © of the inlets and their environs. It is now proved that the glacier branches which produce the bergs proceed incessantly at a rate of thirty to fifty feet per diem ; this movement being not at all influenced by the seasons. .. . In the ice-fiord of Jakobshavn, which spreads its enormous bergs over Disco Bay, and probably far into the Atlantic, the — productive part of the glacier is 4,500 metres (about 24 miles) broad. The movement along its middle line, which is quicker than on the sides nearer the shores, can be rated at fifty feet per diem. The bulk of ice here annually forced into the sea would, if taken on the shore, make a mountain two miles long, two miles broad, and 1,000 feet high. The ice-fiord of Tor- sukatak receives four or five branches of the glacier ; the most productive of them is about 9,000 metres (five miles) broad, and moves between sixteen and thirty-two feet perdiem. The large Karajak Glacier, about 7,000 metres (four miles) broad, : a ee. ee — THE GLACIERS OF GREENLAND. 79 proceeds at a rate of from twenty-two to thirty-eight feet per diem. Finally, a glacier branch dipping into the fiord of Jtivdliarsuk, 5,800 metres (three miles) broad, moved between twenty-four and forty-six feet per diem.* Describing the “Isblink,” in latitude 623° north, Rink says : The whole surveyed area of the inland ice in this place is calculated at 450 square miles, and forms, by means of the tongued shape of its foremost part, in some measure a separate district, in which the principal changes of the whole margin, excepting the ice-fiords, are represented. Toward the interior it is bordered by a row of nunataks,t distant about forty miles from the seaward edge which our travelers had ascended as their starting-point. Here the origin of the ice over which they had passed was at once plainly visible; namely, that it could not have been formed on the spot, but was brought thither from the interior of the continent. The nunataks had been an obstacle to this movement ; on the east side, fac- ing the interior, the ice was broken and piled up several hun- dred feet against the rock, like breakers of an ocean, while to the south and north, and between the nunataks, it poured down like frozen waterfalls to be embodied in and leveled with the crust over which our explorers had traveled. .. . The recent explorations, as already mentioned, have proved that what now we designate as coast-land free from ice was for- merly covered with ice like the interior. This ancient ice-cov- ering reached, in the immediate vicinity of the present inland ice, a height of 3,000 to 4,000 feet, and, farther seaward, 2,000 to 3,000 feet above the sea. All the usual traces of ancient ice-action, the erratic blocks and the ground rocks, are the same here as in northern Europe. * See “Transactions of the Edinburgh Geological Society” for February 18, 1886, vol. v, part ii, pp. 286-293. + Nunataks are simply mountain-tops projecting above the surface of the ice-fields, such as were described in the account of the Muir Glacier in Alaska. Nordenskidld was the first to describe them in Greenland, and gave them this name. 80 THE ICE AGH IN NORTH AMERICA. Rink supposes the opening of new channels for the outlet of the ice through the fiords may have so relieved the interior as to account for this recedence of the ice.* Among the most important observations upon the rate of movement in the glaciers in Greenland are those made by the Norwegian geologist Helland, in the summer of 1875. During that season he nade a series of measurements on the glacier that enters the great Jakobshavn Fiord in the north- ern part of Disco Bay, about latitude 70°. The width of this glacier near its mouth he found to be about two miles and a half. The view from the peaks in the vicinity toward the east extended to a continuous ice-field on the distant horizon. The rate of motion reported by Helland was so great, that scientific men hesitated for some time to credit it. According to his measurements, the Jakobshavn Glacier, in the central portion of its current, was moving more than sixty feet per day, as compared with the three feet per day reported for Alpine glaciers. But the subsequent measure- ments of Steenstrup, given above, and those of my own upon the Muir Glacier in Alaska (made in 1886), amply sustain the conclusions of Helland. It is proper to observe here, again, that the movement of glacial ice is affected much less by the slope of its bottom than by the size of the stream itself. The friction of the ice upon the bottom and sides of its channel is so great, that, where the stream is both shallow and narrow, the motion must be almost completely retarded. On doubling the size * The list of explorers given by Rink is worthy of being honored, and is as follows: “Geologist K. J. V. Steenstrup (eight summers and two winters) ; Lieutenant G. Holm, of the Royal Navy (five summers and one winter); Lieu- tenant R. Hammer, of the Royal Navy (three summers and one winter); Lieuten- ant A. D. Jensen, of the Royal Navy (three summers); geologist Sylow (two summers); painter Groth (two summers); supernumerary officer Larsen (one summer) ; Lieutenant Garde, of the Royal Navy (two summers and one winter) ; geologist Knutsen, Norwegian (two summers and one winter); geologist Peter- sen (one summer); botanist Eberlin (two summers and one winter); painter Riis Carstersen (one summer). Steenstrup and Hammer did most.on the fiords.” THE GLACIERS OF GREENLAND. Sl of a semi-fluid stream, the relative amount of friction be- comes very much less, so that it will move more than twice Fig. 32.-_Map of Frederikshaab Glacier, between 62° and 63°, showing course of Lieuten- ant Jensen in 1878 (forty-seven and a half miles). The black part, ice ; white, land ; shaded, water ; J. N., Jensen’s nunataks ; D. N.. Dolager’s nunataks ; white lines on the black, crevasses ; arrows, glacier-flow. Five species of plants were found on the nunataks which still survive on the White Mountains (N. H.). Dana. as fast as before. This property of a semi-fluid is made suf- ficiently evident from a homely illustration. Molasses in eold weather will scarcely run at all through a gimlet-hole, while it will run with considerable freedom through an auger-hole. Now, the glaciers of the Alps, which were the subjects of Professor Tyndall’s measurements, were, in com- parison to those in Greenland and Alaska, about in the pro- portion of a small gimlet-hole to a large auger-hole, and the faster motion is really not surprising. 82 THE ICE AGE IN NORTH AMERICA. Helland’s observations as to the amount of ice floating away from the glacier in bergs amply confirm the direct cal- culation. The depth of the Jakobshavn Fiord is about 1,200 feet, so that icebergs cf vast size can float off upon its waters. The daily discharge of ice through this fiord was estimated by him to be 432,000,000 cubic feet—about three times the calculation I have made for the Muir Glacier in Alaska. In addition to the formation of large icebergs, the discharge of ice from such a glacier as that at Jakobshavn is doubtless accompanied by a continual cannonade of countless smaller fragments, keeping the heavens full of thundering sounds and the waters full of commotion. From this it fol- lows that the movement of the great glaciers must be rapid, to account for the enormous numbers of first-class icebergs which are encountered in the vicinity, and for the numerous and immense ice-floes composed of smaller fragments. While the attention is fixed on the movement of the gla- ciers, we should not fail to note the uniform presence of subglacial streams of water emerging from their fronts. Such streams are usually in proportion to the size of the gla- cier, and, as already remarked, are most powerful agencies in the transportation of earthy material. The amount of sedi- ment thus brought out by a single subglacial stream on the west coast of Greenland is estimated to be from 15,000 to 20,000 tons daily ; and the amount of water discharged in the stream is far larger than that which passes off as ice. The existence of such subglacial streams reveals much concerning the condition of the glaciers themselves. The question at once arises, Whence does the water come? The answer is found in the facts already mentioned by Norden- skidld concerning the superficial streams of water uniformly encountered on penetrating the glaciated interior of Green- land. Doubtless, also, much water arises from the melting of the lower strata of ice through the heat produced by the friction attendant upon the motion. Mr. Whymper’s descriptions add vividness to our knowl- edge of the Greenland Glacier in the latitude of Disco :. THE GLACIERS OF GREENLAND. 83 In 3 paper communicated to the “Alpine Journal” in 1870, I wrote in relation to this part of Greenland and the country to its north and south: The great ice-covered interior plateau of Greenland can be seen a long way off if the weather is clear. Its summit is ET TT ea ea TE Fic. 33.—Ikamiut Fjord, Greenland, showing hanging glaciers. Glaciers at head of the Fjord come to water’s edge. almost a dead level from north to south. But when one comes nearer to the coast it is concealed by the hills which are on its outskirts. The whole of the (outer) land on the (west) Greenland coast is mountainous, and although the hills scarcely ever, if ever, exceed a height of 8000 or 9000 feet, they effectually conceal the inner or glacier-covered land: This latter is at a distance from the coast varying from ten to sixty or more miles, and, when it is reached, there is an end to land—all is ice, as far as the eye can see. Great as the mass of ice is which still envelops Greenland, there were times when the land was even more completely cov- ered up by it; indeed, there is good reason to suppose that there was a time when every atom of the country was covered, and that life was hardly possible for man. . . . With the exception of places where the rocks are easy of disintegra- 84 THE ICE AGE IN NORTH AMERICA. tion, and the traces of glacier action have been to a great ex- tent destroyed, the whole country bears the marks of the grind- ing and polishing of ice; and, judging by the flatness of the curves of the roches moutonnées, and by the perfection of the polish which still remains upon the rocks, after they have sus- tained many centuries of extreme variations of temperature, the Glacial period during which such effects were produced must have vastly exceeded in duration, or severity, the Glacial period of Europe ; and the existing great interior ice-plateau of Greenland, enormous as it is, must be considered as but the remnant of a mass which was incalculably greater, and to which there is no parallel at the present time, excepting within the Antarctic Circle. And later on, in my book, ‘‘ Scrambles among the Alps,” 1871, pages 246, 247: The interior of Greenland appears to be absolutely covered | by a glacier between 68° 30’-70° north latitude. . . . On two occasions, in 1867, I saw, at a glance, at least 6,000 square miles of it from the summits of small mountains on its out-— skirts. Not a single peak or ridge was to be seen rising above, nor a single rock reposing upon the ice. The country was completely covered up by glaciers ; all was ice, as far as the eye - could see. . . . This vast ice-plateau, although smaller than it was in former times, is still so extensive that the whole of the glaciers of the Alps might be merged into it withnome its bulk being perceptibly increased. In 1872 I again traveled in northwestern Greenland, and by ascending various lofty mountains saw more of the “ inland ice” ; and in the ‘‘Alpine Journal” for 1873, page 220, I wrote : From all the principal summits you perceive the vast gla- cier-clad interior of the country, stretching from north to- south in an unbroken line, with a crest as straight as a sea- horizon. There are no marks upon it which enable one to cal- culate the altitude to which it rises, or the distance to which it extends. But having now seen it from several elevated and widely separated positions, as I find that its summit-line always appears lofty, even from the highest mountains which I have ascended, my impression is that its height is generally not less THE GLACIERS OF GREENLAND. 85 than 8,000 feet, and in some places, perhaps, surpasses 10,000 J?) eee On ascending hills on the outskirts I again had extensive views to the east, finding the land, as before, absoluteiy cov- ered by glaciers. From the nearest parts to the farthest dis- tance that could be seen, the whole of the ice was broken up into séracs. It was almost everywhere riven and fissured in a most extreme manner, and it was obviously totally impracti- cable for sledges. . .. From the repeated views of the interior which had been seen from the coast mountains, it was clear that all this part of Greenland, except the fringe of land on the Davis Strait side, was absolutely covered by snow and ice, and that the in- terior was not broken up in those latitudes as I had conjectured it might be... . This vast glacier is the largest continuous mass of ice at present known. All the glaciers of the Alps combined are as nothing to it, and the greatest of those in the Himalayas are mere dwarfs in comparison. At Jakobshavn the bergs floating away were often from 700 to 800 feet thick, and this is the only information at present possessed of its depth. The angle at which its surface rises toward the east is very slight, being seldom so much as 8°, and generally much less; while in some places there are considerable depressions, and lakes are formed In consequence. .. . | Mount Kelertingouit was 6,800 feet high, and there was a grand and most interesting view from its summit in all direc- tions. Southward it commanded the whole breadth of the Noursoak Peninsula, and extended over the Waigat Strait to the lofty island of Disco; westward it embraced the western part of the Noursoak Peninsula, with Davis Strait beyond ; northward it passed right over the Umenak Fiord (some thirty miles wide) to the Black Hook Peninsula; to the northeast it was occupied by the fiord, with its many imposing islands and islets, surrounded by innumerable icebergs streaming away from the inland ice ; and in the east, extending from north- east to southeast, over well-nigh 90° of the horizon, there was the inland ice itself—presenting the characteristic features which have been mentioned in the earlier papers. The south- 86 THE ICE AGE IN NORTH AMERICA. ern part of the view of the inland ice, as seen from Kelertin- gouit, overlapped the northern part of it as seen on former occasions, while northward it extended to at least 71° 15’ north latitude, so I had now viewed the section of the interior be- tween 68° 30’ and 71° 15’, equal to 190 English miles, and had everywhere found a straight, unbroken crest of snow-covered ice, concealing the land so absolutely that eo a single crag appeared above its surface. The height of this straight, unbroken crest of snow was now the object of attention—the principal object for which the ascent was made. On bringing the theodolite to-bear upon it, | found that it appeared to be slightly depressed below my station ; but, as it was distant more than one hundred miles, it was only lower im appearance and not in reality. On the assumption that it was no more than one hundred miles dis- tant, after making allowance for the refraction and curvature of the earth, its height was found to be considerably in excess of ten thousand feet.* Northward from this point explorations have been carried on incessantly since the middle of the last century begin- ning with the expeditions of Drs. Kane and Hayes between the years 1855 and 1862. These remarkable men were associated from 1853 to 1855, in the second Grinnell Expe- dition in search of Sir John Franklin, which succeeded in exploring the coast on the east side of Smith Sound from Cape Alexander, in latitude 78°, to Washington Land, in latitude 80°; while in 1861 and 1862 Dr. Hayes conducted an independent expedition to Lady Franklin Bay, in lati- tude 82°, and resurveyed portions of his former field. In the neighborhood of Cape Dudley Digges, about lati- tude 76°, Dr. Kane’s party encountered a glacier which he describes as follows: This glacier was about seven miles across at its ‘de- bouche” ; it sloped gradually upward for some five miles back, NR heh of the Geological Society of America,’’ vol xiv (1902), ong Published in ‘‘Am. Geol.,’’ vol. xviii, Dec. 1896, “Origin of the High Terrace Deposits of the Monongahela River.’ 392 THE ICE AGE IN NORTH AMERICA. abandoned water weirs at an elevation of approximately 1,100 feet above tide. These are just such channels or “cols” as would be cut by the escaping water impounded by an ice-dam which obstructed the northerly drainage of the Monongahela. The terrace deposits of clay, quicksand, sand and gravel, bor- dering the river valley for more than 100 miles below Weston in West Virginia, range from 1,020 to 1,068 feet above tide, while that at Pittsburg is 990 feet above tide. The present river falls 290 feet between Weston and Pittsburg, while the terrace falls only forty feet in 200 miles at Pittsburg, and eight feet at Geneva, 117 miles below Weston. In tabular form the facts are as follows. PRESENT RIVER TOP OF DEPOSITS MILES a A.T. 0 Weston 990 _ 1,030 40 Clarksburg 916 1,020 75 Fairmont 851 1,067 101 Morgantown 787 1,038 117 Geneva (2 1,022 206 Pittsburg 700 990 These terraces are specially prominent wherever a tributary comes into the main valley to form a delta at the level of the impounded water. Frequently the clay topping of the terrace is more than sixty feet thick, furnishing material for numerous pottery establishments. The following plants were identified by Dr. F. H. Knowl- ton, as occurring in these clay deposits. 1. Equisetum arvense L.; 2. Cyperus sp.; 3. Potamogeton robbinsi Oakes; 4. Liqui- dambar_ styracifolia L; 5. Platanus occidentalis L (sycamore) ; 6. Ulmus racemosa Thomas (the white elm); 7. Quercus falcata Michigan; 8. Betula nigra L. (black birch); 9. Fagus ferruginea Ait (beech) ; 10. Castanea pumila Mill (chinquapin). All of these are living species, and most of them are still found in the vicinity. But special interest attaches to Pota- mogeton robbinsit, of which a great number of fragments of GLACIAL DAMS, LAKES AND WATERFALLS. 393 stems and leaves were found. Its present distribution is from New Brunswick to New Jersey, north of Lake Superior and northward. The occurrence of this species in these beds is, as Professor White remarks, of special interest, since it practically demonstrates that there was during glacial times a movement of water from the edge of the ice near Beaver, Pennsylvania, southward along the Monongahela Valley, through the escape weirs just described, which brought with it this northern plant. Since as already shown the preglacial drainage of both the upper and the middle portions of the Ohio basin was to the north, it follows that vast sheets of water were ponded up in front of the advancing ice-sheet from the moment that those northern outlets were closed. One of the most prominent of these would be that occupying the basin drained in preglacial times by the Monongahela and Lower Allegheny rivers, which originally flowed off through Beaver Creek and the Grand River valleys into Lake Erie a little east of Ashtabula. This temporary lake would have its level regulated by the height of the col already referred to at New Martinsville, a little below Wheeling, West Virginia. It was in this glacial lake that the deep still water clay deposits described along the Middle Monongahela accumulated. But after a compara- tively short period the col at New Martinsville was worn down so that a permanent line of drainage was opened in that direc- tion and Lake White, as we may be permitted to name it, no longer existed in the Monongahela Valley. But as the ice-sheet continued to advance through central and southern Ohio the other lines of northerly drainage were obstructed and other temporary lakes formed which continued until the col, in the Muskingum above Zanesville, and that in the Ohio below the mouth of the Scioto were eroded suffi- ciently to permanently open present lines of drainage. Then, finally, when the ice reached the junction of Mill Creek Valley and the Great Miami at Hamilton, O., the whole drainage 394 THE ICE AGE IN NORTH AMERICA. which had been flowing in that direction was so obstructed that it was turned over the col which existed a little below Cincinnati, and the permanent channel was opened which is now followed by the Ohio River. During this period of erosion there was a temporary lake formed above Cincinnati, but of comparatively short duration, for the immense flow of water from the whole upper basin of the Ohio would work with great rapidity to cut down the col below the city. After this there followed in immediate succession, the Cincinnati ice-dam proper, of which an account has been given. For a distance of fifty miles the ice advanced into Kentucky to heights of land fully 500 feet above the present level of the river, and must have obstructed the drainage up ~ to that level. This was doubtless of comparatively short duration, but while it continued it would set the water in the whole valley above to that height, which would submerge Pittsburg to a depth of 300 feet, and reach far up both the Monongahela and the Allegheny rivers. The shortness of its duration, however, makes it difficult to distinguish its deposits from those which had been made during the con- tinuance of the earlier ice-dams. While admitting there- fore, that the ‘Cincinnati ice-dam”’ was at first somewhat overworked in accounting for the deposits in the Upper Ohio Valley, it is by no means ruled out of the problem. TheCin- cinnati ice-dam still remains a fact with which all students of the region are compelled to reckon. As already intimated, however, the existence of the Cin- cinnati dam would necessitate an overflow either into the Kentucky River or around the margin of the ice, and such a channel, if it ever existed, should be easily discovered. But though I have diligently searched for it, it has so far eluded observation. This has inclined me to account for the Kentucky deposits as results of annual ice gorges, dur- ing the climax of the period, in the narrow channel below the city. But even so the phenomenon is none the less impres- sive, and would involve the flooding of the upper Ohio and its tributaries to the extent stated. GLACIAL DAMS, LAKES, AND WATERFALLS. | 395 On coming to the region of the Great Lakes, the influence of ice-barriers is very conspicuous. South of Lake Erie there is an ascending series of what are called lake ridges. These are composed of sand and gravel, and consist largely of local material, and seem to maintain throughout their entire length a definite level with reference to the lake, though accurate measurements have not been made over the whole field. The approximation, however, is_ sufficiently per- fect to permit us to speak of them as maintaining a uniform level. These ridges can be traced for scores of miles in a continuous line, and in the early settlement of the country were largely utilized for roads. In Lorain county, Ohio, an ascending series of four ridges can be distinguished at different levels above the lake.* The highest is from 200 to 220 feet above it; the next is approximately 150 to 160 feet; the next lower is from 100 to 118 feet; and the next lower less than 100 feet, while some appear on the islands near Sandusky which are not over 70 feet above the water-level. Eastward from Buffalo portions of this series have been traced, according to Gilbert, until they disappear against the highlands near Alden, on the Erie Railroad. Lake Ontario is likewise bordered by similar ridges upon its southern and eastern sides, but the investigations in that region are not yet complete enough to be altogether satisfac- tory. From what has already been done it is evident that they do not maintain so nearly a uniform level as on the shores of Lake Erie. Mr. G. K. Gilbert, of the United States Geological Survey, informs me that, from the vicinity of Oneida Lake toward the northeast, the ridges rise rapidly with reference to the lake-level, and that to a less extent they rise in a westerly direction, showing that if they were water-deposits, there has been considerable oscillation of the land both northeast and southwest of an axis following the line of the Mohawk Valley. ‘That the ridges on Lake Erie mark toupee ary shore-lines * “ Geological Survey of Ohio,” vol. ii, p. 207. a de aenelaaliasd anime - : (,,'AJoID0g [VIISO[OaH YsinquIp” oq4 Jo suo ovsuv1L,,) ‘(efod ABD) oly oY] Jo a10ys ULOYINOS ay} Jo APUIOIA OY} 0} UMBIPYIIA PBY BOI aq} USYA ‘O1YO UeYJIOU UI s}o[OXBl Jo MONBULIOJ SuIMoYs dejy— ‘FIT “aL TL A Gi, iy AU Op *}UOJJ-99] JY} pue Pays-s9ayeM GAL NGaMiad Ca SLATAMVT TVIOVIO qHL SNIMOHS dVW GLACIAL DAMS, LAKES, AND WATERFALLS. 397 of the lakes can not well be doubted, for they are not related to any great natural lines of drainage, but follow the wind- ings ofa definite level, receding from the lake wherever there is a transverse valley, and forming in some cases parallel embankments on either side of such valley, running inland as far as to the general level of the series, and then return- ing on itself upon the other side, to strike off again par- allel with the shore at the same level. Their relation to the lake is also shown by the local character of the material. It is usually such as would wash up on the shore out of the roek in place. In the sandstone region the ridges are largely made up of sand, mingled with fragments from the general glacial deposit. Over the regions of outcropping shales the ridges are composed largely of the harder nodules which have suc- cessfully resisted the attrition of the waves. Other evidences that they are shore-deposits are their stratification, the rela- tive steepness of their sides toward the lake, and the frequent occurrence of fragments of wood buried at greater or less depths on their outer margin. It need not be said that there has been much speculation concerning the cause which maintained the waters of the lakes at the levels indicated by these ridges, and permitted them to fall from the level of one to that of another in suc- cessive stages, so suddenly as they seem to have done; for, from the absence of intermediate deposits, it is evident that the formation of one ridge had no sooner been completed, than the one at the next lower level began to form. In the earlier stages of glacial investigation, before the full power and flexibility of glacial ice were appreciated, and before the exact course of the southern boundary of the ice-sheet was known, the elevation of the water to produce these ridges was supposed to have resulted either from a general subsidence of the whole region to the ocean-level, or from the elevation of a rocky barrier across the outlet. Both these theories were attended with insuperable difficu!ties. In the first place, there is no such amount of collateral evi- dence to support the theory of general subsidence as there 398 THE ICH AGE IN NORTH AMERICA. should be if it really had occurred. The subsidence of the lake region to such an extent would have left countless other marks over a wide extent of country ; but such marks are not to be found. Especially is there an absence of evidences of marine life. The cause was evidently more local than that of a general subsidence. The theory of the elevation of a rocky barrier would also seem to be ruled out of the field by the fact that no other direct evidence can be found of such recent local disturbances. Such facts as we have point to a subsedence at the east rather than to an eleva- tion. But a glance at the course of the terminal moraine, and at the relation of the outlets of these lakes to the great ice- movements of the Glacial period, brings to view a most likely cause for this former enlargement and increase in height of the surface of the lower lakes. It will be no- ticed that the glacial front near New York city was about one hundred miles farther south than it was in the vicinity of Buffalo. Hence the natural outlet to the Great Lakes through the Mohawk Valley would not have been opened until the ice-front over New England and eastern New York ~ had retreated to the north well-nigh one hundred and fifty miles. A similar amount of retreat of the ice-front from its farthest extension in Cattaraugus county, in New York, would have carried it back thirty miles to the north of Lake Ontario, while a similar amount of retreat from eastern Ohio would have left nearly all the present bed of Lake Erie free from glacial ice. With little doubt, therefore, we have, in the lake ridges of Upper Canada, New York, and Ohio, evi- dence of the existence of an ice-barrier which continued to fill the valley of the Mohawk, and choke up the outlet through the St. Lawrence, long after the glacial front farther to the west had withdrawn itself to Canada soil. A study of these ridges may yet shed important light upon the length of time during which this ice-barrier continued across the valley of the Mohawk. | o 3 o! ae Q ol < y coe C7 N A ° 25 50 100 Mi Fr wayn€ Fia. 115—Lake Whittlesey, with correlative ice border. (Map by Leverett.) cae Rahat ak Seale ° UT 50 400 Mi faoelpe ect nap ape tWayn2 Fie. 116—Lake Warren, with probable correlative ice border. (Map by Leverett.) Nipissing GreatLakes with Isobases Scale oF, $075 so Mjleg Fic. 117—Nipissing Great Lakes and Champlain Sea. Numerous isobases give altitude above sea level of the highest exposed shore. Isobases of Michigan and Huron basins by Taylor and Goldthwaite. 75 76 @ ~e 79 80 PAGS: 81 B2 B —-~77, 81 83 ie Pea eD ads ef] Vy. BAY ‘Ea GY : Yi LOL G MIA Ys GY Be A Gri Wye Ui. YI 4 vi ‘Ys oY LMI, GJ (7 We Vl ae ZUygey a4 oN? , Z nN) ZG; QA: y KE AGG tj ( & Z 4 : 2 R yeliphos al R. soy t Y peas i ! eh xs) o 3 Ss G; U Le (f e YY : 86 P Channel 0. > 85 / 86 87 88 Ss 88. Fic. 118.—Ma still 45 he ice-front had withdrawn about one hundred and twenty miles, and while it let was then through the Wabash. Niagara was not yet born (Claypole). Pen p showin ill filled the vall (‘* Transactions Edinburgh Geological Society. . =— ~ -_ y F x ( ‘ | | r 4 . « d >) - { a : 7 y i 4 Fi { Ls t cr ‘ - } C & ; ' A i 1 \ J = - ; ay, } : Y Ee 3 i 2 t= 4 = ¢ Z the a ee : Ke 5 f E { ae ‘ i > 4 s + . A 1 < = na) = = re - ‘ a : ; - i ¥ a a - \. " te * ( a \ uf , iw Zz 2 ‘ =) . J - us é i ere £ al + te We x . 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As soon as the departing ice-sheet, which had enveloped the northern United States and British America during the glacial period, in its final melting off the land from south to north, receded beyond the water-shed dividing the basin of the Minnesota River from that of the Red River of the North, a lake, fed by the glacial melting, stood at the foot of the ice- fields, and extended northward as they withdrew along the valleys of the Red River to Lake Winnipeg, filling this valley and its branches to the heights of the lowest points over which an outlet could be found. Until the ice-barrier was melted away on the area now crossed by the Nelson River, thereby gradually draining this glacial lake, its outlet was along the present course of the Minnesota River. At first its overflow was upon the nearly level undulating surface of the drift, 1,050 to 1,125 feet above the sea, at the west side of Traverse and Big Stone counties, Minnesota; but in process of time this cut a channel there, called Brown’s Valley, 100 to 150 feet deep and about a mile wide, the highest point of which, on the present water divide between the Missis- sippi and Nelson river basins, is 975 feet above the sea-level. From this outlet the Red River valley plain extends 315 miles north to Lake Winnipeg, which is 710 feet above the sea. Along this entire distance there is a very uniform continuous descent of a little less than one foot per mile. Thefarmers and other residents of this fertile plain are well aware that they live on the area once occupied by a great lake; for its beaches, having the form of smoothly rounded ridges of gravel and sand, a few feet high, with a width of several rods, are observable extending almost horizontally long distances upon each of the slopes which rise east and west of the valley plain. Hundreds of farmers have located their 402 THE ICE AGE IN NORTH AMERICA. buildings on these beach ridges as the most dry and sightly spotson their lands, affording opportunity for perfectly drained cellars even in the wettest seasons, and also yielding to wells, dug through this sand and gravel, better water than is usually obtainable in wells on the adjacent clay areas. While each of these farmers, in fact every one living in the Red River Valley, recognizes that it is an old lake bed, few probably know that it has become for this reason a district of special interest to geologists, who have traced and mapped its upper shore along a distance of about 800 miles. Numerous explorers of this region, from Long and Keat- ing in 1823, to Gen. G. K. Warren in 1868 and Prof. N. H. Winchell in 1872, recognized the lacustrine features of the valley; and the last named geologist first gave what has been generally accepted as the true explanation of the existence of the lake, namely, that it was produced in the closing stage of the glacial period by the dam of the continental ice-sheet at the time of its melting away. As the border of the ice-sheet retreated northward along the Red River Valley, drainage from that area could not flow as now freely to the north through Lake Winnipeg and into the ocean at Hudson Bay, but was turned by the ice-barrier to flow south across the lowest place on the water-shed, dividing this basin from that of the Mississippi. This lowest point is found, as before noted, at Brown’s Valley on the western boundary of Minnesota, where an ancient water-course, about 125 feet deep and one mile to one and a half miles wide, extends from Lake Traverse, at the head of the Bois des Sioux, a tributary of the Red River, to Big Stone Lake, through which the head stream of the Min- nesota River passes in its course to the Mississippi and the Gulf of Mexico. Detailed exploration of the shore lines and area of this lake was begun by the present writer for the Minnesota Geological Survey in the years 1879 to 1881, under the direc- tion of Professor N. H. Winchell, the State geologist. In THE GLACIAL LAKE AGASSIZ. 403 subsequent years I was employed also in tracing the old lake shores through North Dakota for the United States Geological Survey, and in Southern Manitoba, to the distance of 100 miles north from the international boundary te Riding Mountain, for the Geological Survey of Canada. For the last named survey, Mr. J. B. Tyrrell extended the exploration of the lake shore lines more or less completely for 200 miles farther north along the Riding and Duck mountains and the Porcupine and Pasquia hills, west of Lakes Manitoba and Winnipegosis, to the Saskatchewan River. This glacial lake was named by me in the eighth annual report of the Minnesota Geological Survey, for the year 1879, in honor of Louis Agassiz, the first prominent advocate of the theory of the formation of the drift by land ice; and the outflowing river, whose channel is now occupied by Lakes Traverse and Big Stone and Brown’s Valley, was named also by me, in a paper read before the American Association for the Advancement of Science at its Minneapolis meeting in 1883, the River Warren, in commemoration of General War- ren’s admirable work in the United States Engineering Corps, in publishing maps and reports of the Minnesota and Missis- sippi River surveys. Descriptions of Lake Agassiz and the River Warren are somewhat fully given in the eighth and eleventh annual reports of the Minnesota Geological Survey, and in the first, second, and fourth volumes of its final report. Three other special re- ports of my explorations of Lake Agassiz were published; the first in 1887, as Bulletin No. 39, of 84 pages, with a map, by the Geological Survey of the United States; the second in 1890, by that of Canada, in its Annual Report, New Series, vol. iv, for 1888-89, forming Part E, 156 pages, with maps and sections; and last, this subject was most fully issued by the U. S. Geological Survey, as its Monograph XXV, 1895, a quarto volume of 658 pages and 38 plates (maps, views, and sections). 404 THE ICE AGE IN NORTH AMERICA. Several successive levels of the ancient lake are recorded by distinct and approximately parallel beaches, due to the gradual lowering of the outlet by the erosion of the channel at Brown’s Valley, and these are named principally from stations on the Breckenridge and Wahpeton line of the Great Northern Railway, in their descending order, the Herman, Norcross, Tintah, Campbell, and McCauleyville beaches, because they pass through or near these stations and towns. The highest or Herman beach is traced in Minnesota from the northern end of Lake Traverse eastward to Herman, and thence northward, passing a few miles east of Barnesville, through Muskoda, on the Northern Pacific Railway, and around the west and north sides of Maple Lake, which lies about twenty miles east—southeast of Crookston, beyond which it goes eastward to the south side of Red and Rainy lakes. In North Dakota the Herman shore lies about four miles west of Wheatland, on the Northern Pacific Railway, and the same distance west of Larimore, on the Pacific line of the Great Northern Railway. On the international boundary, in passing from North Dakota into Manitoba, this shore coin- cides with the escarpment or front of the Pembina Mountain plateau, and beyond passes northwest to Brandon on the Assiniboine River, and thence northeast to the Riding mountain. Leveling along this highest beach shows that Lake Agassiz, in its earliest and highest stage, was nearly 200 feet deep above Moorhead and Fargo; a little more than 300 feet deep above Grand Forks and Crookston; about 450 feet above Pembina, St. Vincent, and Emerson; more than 500 feet above the city of Winnipeg; and about 500 and 600 feet, respectively, above Lakes Manitoba and Winnipeg. ‘The length of Lake Agassiz is estimated to have been nearly 700 miles, and its area not less than 110,000 square miles, exceeding the com- bined areas of the five great lakes tributary to the St. Lawrence. THE GLACIAL LAKE AGASSIZ. 405 When the ice-barrier was so far melted back as to give out- lets northeastward lower than the River Warren, other beaches marking these lower levels of the glacial lake were formed; and finally, by the full departure of the ice, Lake Agassiz was drained away to its present representative, Lake Winnipeg. The rate of the northward ascent of the originally level highest beach, within the area of my leveling, varied from about six inches per mile near its southern end to about one foot per mile along the greater part of its extent to southern Manitoba. On the east side of the Red River Valley the old shores are higher than on its west side, the rate of ascent from west to east being about half as much as from south to north. The direction of maximum ascent of the planes of the former lake levels is therefore toward the north-northeast. Farther north several beaches of the seriesmapped by Tyrrell along the bases of the Riding and Duck mountains have a northward rise of two or three feet per mile. The changes of level were in progress and were nearly completed during the existence of Lake Agassiz, as is shown by the gradual diminution in the northward ascent of the successive lower beaches, until the latest and lowest differs only slightly from perfect hori- zontality. ; Gravitation of Lake Agassiz toward the ice-sheet accounts for a small part of the present inclination of the beaches. Changes in the temperature of the earth’s crust due to the glacial period and its termination produced a still smaller effect, but this tended to give the opposite slope, or a descent toward the north. Upward movement of this great land area, resulting from its being unburdened by the departure of the ice-sheet, was the chief element in the causes of the differential changes in the height of this basin. Flow of the plastic inner part of the earth’s mass, restoring its equilibrium or isostasy, uplifted first the southern half of the area of Lake Agassiz, from Lake Traverse to Gladstone in Manitoba; nextit raised 406 THE ICE AGE IN NORTH AMERICA. the northern half of the lake area, while the region at the south was almost at rest; and finally, during the recent epoch, after the whole basin of Lake Agassiz was passed by this wave like permanent uplift, it has been elevating the basin of Hudson Bay, where the movement appears to be still in progress. Pleistocene oscillations of the land in many other parts of the world have been independent of glaciation, or these have been combined with movements due to the accumulation of ice-sheets and to their removal; but the uplifting of the basins of Lake Agassiz and Hudson Bay is apparently attributable wholly to the departure of the ice-sheet. The entire duration of Lake Agassiz, estimated from the amount of its wave action in erosion and inthe accumulation of beach gravel and sand, appears to have been only about 1,000 years; and the time of its existence and of the end of the ice age is thought, from the rate of recession of the Falls of St. Anthony, cutting the post-glacial gorge of the Mississippi River from Fort Snelling to Minneapolis, to have been some- where between 6,000 and 10,000 years ago. CHAPTER XVI. THE LOESS. TuHE deposit called doess received its name in Germany, where it was first described. But its most remarkable devel- opments are in China and in America. The formation is one of great interest in every respect. It furnishes the most fruitful soil in the world, and is extensively used for the ex- eavation of houses in China and in some parts of America. At the same time it presents the scientific observer with a most attractive but puzzling problem. Professor Pumpelly, who has seen it in all parts of the world, gives the following lucid description of the deposit : This remarkable formation covers several hundred thousand square miles in northern China, and larger areas in the rest of Asia. It forms the soil also over an immense area in the west- ern United States. Its thickness varies in China up to two thousand feet, and to one hundred and fifty and two hundred feet in Europe and America. Loess is a calcareous loam. It is easily crushed in the hand to an almost impalpable powder, and yet its consistency is such that it will support itself for many years in vertical cliffs two hundred feet high. A close examination shows that it is filled with tubular pores branching downward like rootlets, and that these tubes are lined with carbonate of lime. It is to these that it owes its consistency and its vertical internal structure. It is wholly unstratified, and often where erosion has cut into it, whether one foot or one hundred yards, the walls are ab- solutely vertical. Its vertical internal structure causes it to break off in any vertical plane, but in no other. Hence, when 26 408 THE ICE AGE IN NORTH AMERICA. a cliff is undermined, the loess breaks off in immense vertical plates leaving again a perpendicular wall. It is divided into beds varying in thickness from one foot to two or three hundred, which thin out to nothing at the bor- ders and are separated by parting planes. These planes are marked by angular débris near the mountains, and by elon- gated upright calcareous concretions elsewhere. This remarkable combination of softness with great strength and stability of exposed surfaces is of inestimable value in a woodless country. In Asia, thousands of villages are excavated in a most systematic manner at the base of cliffs of loess. Doors and windows pierced through the natural front give light and air to suites of rooms which are separated by natural walls, and plastered with a cement made from the loess concre- tions. These are the comfortable dwellings of many millions of Chinese farmers, and correspond to the ruder dug-outs of Nebraska. ‘To the same qualities is due the fact that the loess districts of China are exceedingly fertile plains, in each of which a rap- idly progressing erosion has excavated the most labyrinthine valley systems, in which all the members, down to the smallest tributaries, are sunk with vertical walls to depths of from one hundred to several hundred feet. Even the wagon-roads be- come in time depressed to a depth of fifty feet and more by the removal of the dust by wind. There is one more peculiarity of the loess: it not only is wholly unstratified, but it contains the remains of only land- animals and especially of land-snails. Alexander Braun ex- amined 211,968 specimens of shells from the loess of the Rhine between Basle and Bonn, and found that all were land-snails except only thirty-three individuals, consisting of Limnea, Planorbis, and Vitrina, which came from three isolated points in the valley of the Rhine and Neckar. Baron Richthofen, after prolonged study of the loess of China, propounded the theory that it was a wind-deposit, consisting of material which had resulted from the slow dis- integration of the rocks in the arid regions of central Asia, from which the westerly winds have been continually blow- THE LOESS. 409 ing for an untold period. As applicable to China, Richt- hofen’s theory is perhaps adequate. Mr. Pumpelly is also inclined to accept the theory as applicable to Ameriea, re- marking that— No one can realize the capacity of wind as a transporter of fine material who has not lived through at least one great storm on a desert. In such a simoon the atmosphere is filled with a driving mass of dust and sand which hides the country under a mantle of impenetrable darkness, and penetrates every fabric ; it often destroys life by suffocation, and leaves in places a deposit several feet deep. The prevailing westerly wind, carrying sand, carves and pol- ishes the rocky crest of the Sierra Nevada, and, as Mr. King tells me, has formed long wind-stream deltas—if I may coin the term—in the form of lofty sand ranges stretching from each pass eastward, far out on the desert. The often cited instances of far-driven volcanic ashes show the ability of the wind to carry comparatively coarse dust through distances of several hundred miles, but it does not seem improbable that the finer particles may remain suspended while the wind makes a complete circuit of the globe. I wit- nessed on March 31st and April 1st, in 1863, a dust-fog at Nagasaki which lasted two days, and left only a just percepti- ble film of dust, observable only on the white, newly painted deck of a yacht. A similar fall occurred simultaneously at Shanghai, and both were contemporaneous with a terrific dust- storm which during two days shrouded the country about Tientsin in deep darkness. I am indebted again to Mr. Clarence King for the state- ment that dust-fogs occur on the coast of California with the prevailing west wind; and this may be, as he suggests, the finest residuum of the loess-dust of an Asiatic dust-storm.* Concerning the power of wind to transport dust, many other striking illustrations have been noted. Showers of red- dish dust occasionally fall upon ships far out at sea. Darwin describes one such storm encountered by him near the Cape * “ American Journal of Science,” vol. exvii, 1879, pp. 138, 134, 139. 410 THE ICE AGE IN NORTH AMERICA. Verds, which was estimated to be sixteen hundred miles broad. A similar shower which passed over the southern part of France in 1846 is estimated by Ehrenberg to have deposited nearly a million pounds of dust. On examination he found that about one eighth of it consisted of microscopic organisms, many of which belonged in South America, thus showing that the wind had blown the dust across the Atlan- tic. In 1835 volcanic dust was blown from Guatemala to Jamaica, a distance of eight hundred miles. The main difficulty of applying the wind theory to account for the loess of the Mississippi Valley and of Europe lies in its definite relation to water-levels. For example, in the Rhine Valley the loess rests in places upon elevations of eight hundred feet above the river, but does not occur at higher levels. This would clearly indicate that it is a water- deposit. The problem has been to conceive how the water could be maintained at that level in the valley of the Rhine; and the theory has been put forth, and ably defended by Geikie and others, that the Rhine and other rivers emptying into the North Sea were obstructed at their mouths by the Scandinavian glaciers, and so the water was ponded back toward the Alps to the level at which the loess ceases. The absence of fossils of aqueous origin in the loess may be accounted for in two ways: 1. If the deposit took place, as was supposed, in temporary glacial lakes, there may have been no species existing in them to have left their remains. This would be likely to be the case for three reasons: (1) the lakes were of only temporary continuance ; (2) the tem- perature of the water must have been abnormally low; and (3) the superabundance of silt might interfere with animal life. 2. Professor Hilgard has suggested that the porosity of the loess, which favors the continual presence and percola- tion of water charged with acids throughout its mass, renders it almost certain that any inclosed fossils would have been rapidly dissolved. As to why this oxidizing and dissolving process should have selected fossils of aqueous origin, and made an exception in favor of those of terrestrial animals, THE LOESS. 411 Professor Hilgard explains that the terrestrial fossils are, as a matter of fact, found near the marginal portion of the loess, where the destructive processes are least. Whether, also, there may not be a difference between the destruetibility of land- and fresh-water shells is also a question. The occur- rence of nodules of lime throughout the mass points to such a work of solution and redistribution by water. In regard to the frequent occurrence of the bones of the larger land-ani- mals, Professor Hilgard remarks: “That the phosphatic bones should not have dissolved as easily as the mere carbon- ate shells is readily intelligible; and as regards their mode of occurrence in the loess of the lower Mississippi they are Fic. 119.—Stratification of the loess in a railway cut at Plattsmouth, Nebraska, at a depth of Sek Sed feet from the surface. (From pioeran furnished by Dr. A. L. Child, of Kansas City, Mo.) (Chamberlin.) (United States Geological Survey.) always very much scattered, many bones belonging to the same individual being rarely found together, but seeming to have drifted widely apart. It is not easy to see how the cumbrous bones of the mammoth could have been widely separated in a subaérial deposit.” * * “ American Journal of Science,” vol. exviii, 1879, p. 110. 412 THE ICE AGE IN NORTH AMERICA. - It. is to President Chamberlin, again,* that we are in- debted for the most careful study of this problem in the Mis- sissippi Valley. According to him, the loess is limited pre- dominantly to the river valleys, and the belt is ordinarily not over forty miles in width. As a rule, also, it is thicker and slightly coarser in character near the banks of the great riy- ers, and there shows some signs of stratification. A comparison of loess with sand and clay reveals some interesting facts. The loess is intermediate in size and tine- ness. When the particles are suspended in water, the loess settles much more rapidly than clay—as much of the loess settling in four hours as of the clay in thirty-six hours. Out of 150,000 particles of loess examined under the microscope, 146,000, or about rinety-seven per cent, were less than -005 of a millimetre in diameter. A grain of sand one millimetre in diameter is considered fine. But this would make 200,000 particles of loess of the size mentioned, and 100,000 particles of the fineness of a large part of true clay. The size of the largest particles of loess noted by President Chamberlin was about one tenth of a millimetre in size, and consisted of seales of mica. The loess of Vicksburg is a little finer than that of Kansas City, and both a little finer than that from the Rhine. The particles of loess were found to be angular and irregular. “Sharp corners and rough surfaces are the rule, and any ap- proach to regularity or smoothness is the exception.” In the vicinity of the great rivers the grains are coarser than at points removed from them. In chemical composition the difference between loess and true residual clays is not very striking ; but, as compared with glacial clays, occurring in the till, there is a marked difference in several respects. The gla- cial clays have far less amount of silica and alumina, and a far larger amount of calcic and magnesian oxides and of carbonic dioxides. The glacial clays are evidently the result largely of mechanical abrasion; but the loess would seem to consist in larger proportion of material resulting from chemical dis- * “Driftless Area of the Upper Mississippi Valley,” pp. 278-307. THE LOESS. 413 integration. But the amount of kaolinized products is nearly four times as great in the residuary clays as in glacial clays or loess. } The altitude of the loess deposits in the Northwest is by no means uniform, and its variations present great theoretic difficulties. In the lower part of the Mississippi Valley it is limited to a height of about two hundred and fifty feet. In the upper Mississippi Valley, however, it rises to a height of seven hundred feet above the bed of the river. ‘To account for this, the first impulse would be to suppose a general de- pression of the northern region. But this theory is excluded by various irregularities in this region itself. For example, the loess rises much higher upon the west side of the upper Mississippi than upon the east side, especially in the vicinity of the driftless area of Wisconsin. To explain this it is necessary to resort to a rather com- plex theory. In part, perhaps, the peculiar distribution of loess is attributable to a period of general northerly depres- sion during the Glacial epoch. This apparent depression, however, was probably not caused wholly by an oscillation of the crust of the earth itself, since it is shown that it may be due in some degree. to the attraction of the ice which had accumulated to the north. Mr. R. S. Woodward, of the United States Geological Survey, has worked out the prob- lem of attraction and its influence in producing a higher level of water at the north, on the supposition that the ice-sheet was ten thousand feet thick, and covered an area to the north 2,600 miles in diameter, and finds that the possible influence of such attraction might change the water-level at the ice- margin thirty-eight degrees from its center as much as 573 feet. But the elevation of the loess attains a height in Iowa and Wisconsin of 1,285 feet. This theory of change of the water-level by glacial attraction, therefore, though not ade- quate, very evidently comes in for a part of the credit of pro- ducing the puzzling facts relating to the deposition of loess.* * “Driftless Area of the Upper Mississippi Valley,” pp. 291-301. 414 THE ICE AGE IN NORTH AMERICA. A noticeable phenomenon west of the driftless area in Wisconsin and Iowa is that the loess is thickest near the east- ern margin of the ice-lobe which passed southward through central Iowa. The distance from the driftless area to the Missouri River, or the width of this lobe in the latitude of Milwaukee, is not far from three hundred and forty miles. It is urged that the presence of an ice-lobe over that region may have had influence in elevating the loess deposits. Since attraction varies inversely as the square of the distance, such a mass of ice near at hand would slightly raise the water along its margin. The objection to this is that the wider ice-lobe to the east did not produce corresponding influence. Among the more fruitful supplementary hypotheses brought in to aid in the solution of this part of the prob- lem is to be mentioned that of glacial dams similar to those already alluded to in Europe. In this country the principal field in which they may have existed is where it is most needed, namely, west of the Mississippi. An examination of our map will at once suggest that it is possible for much of the loess in northeastern Kansas and eastern Nebraska to have accumulated in temporary lakes formed by glacial dams across the mouth of the Kansas and Platte Rivers, or even of the Missouri itself. How far this cause may have operated remains yet to be determined. So complicated are the facts pertaining to the loess as they now appear, that it is not likely that, for some time to come, investigators will arrive at a perfect agreement con- cerning its manner of deposition. Those, however. who have most attentively studied glacial phenomena may be par- doned if they work the glacial hypothesis for all that it is worth. The existence of the vast body of ice which covered the glaciated area introduces a very complicated and efficient cause which it is exceedingly difficult to eliminate from the problem; and it is as allowable for the glacialist to take refuge in supposed ice-dams, where their existence is possible and can not be disproved, as for the ordinary geologist to sup- pose vast orographic changes. The study of the loess has THE LOESS. 415 not come so much within my own field of observation as other glacial deposits have done. Still, in southern Indiana and Illinois, and in western Iowa and eastern Nebraska, I have been able to study many typical regions of this deposit ; and the more attention I have given to the subject, the more I have been led to magnify the agencies of the Ice period in producing the results both positive and negative. I have come, therefore, to set an increasingly high estimate upon the suggestions of Mr. Upham, made after he had concluded his survey of the terminal moraine in Minnesota, Lowa, and eastern Dakota : When the ice-sheet extended to the Coteau du Missouri, the Coteau des Prairies, and the Kettle-Moraine, the floods formed by its summer meltings were carried southward by the present avenues of drainage, the streams which occupied the areas between its great lobes in order from west to east being the Big Sioux, Mississippi, and Wisconsin Rivers. The vast glaciers which were gathered up on the Rocky Mountains, and the ice-fields which sloped downward to their termination at the coteaus and the moraine north and east in Minnesota and Wisconsin, supplied every summer immense floods laded with silt, sand, and gravel, that had been contained in the melting ice. Very extensive deposits of modified drift were thus spread along the course of the swollen Missouri and Mis- sissippi. The Orange sand and gravel, described by Professor E. W. Hilgard and others in the lower Mississippi Valley, ap- pear to have been deposited in this way, but during the earlier Glacial epoch, when an ice-sheet reached in Dakota beyond the Missouri River to a termination forty miles west and twenty miles southwest of Bismarck, into northeastern Kansas, half-way across the State of Missouri, and nearly to the Ohio River. In the closing stages of this epoch, and during the time succeeding, till the date of the terminal moraine of the coteaus, and especially at the final retreat of the ice-sheet of this later epoch, the deposition of the overlying, finely pulverized, are- naceous and calcareous silt, called the Bluff formation, or loess, took place. This covers considerable areas along the Mis- 416 THE ICE AGE IN NORTH AMERICA. sissippi from southeastern Minnesota to its mouth; but its greatest thickness and extent are found in the basin of the Missouri River from southern Dakota to its junction with the Mississippi, and upon the region crossed by the Platte or Nebraska River, its longest tributary from the west, which takes its head-waters from a large district of the Rocky Mount- ains. The continuity of this formation from the borders of © the ice-sheet and the glaciers of the Rocky Mountains to the shores of the Gulf of Mexico, the absence from it of marine shells, and the presence of land- and fresh-water shells, indicate that its deposition was by slowly descending floods, uplifted upon the surface of this sediment which was being accumu- lated during every summer through a long epoch, in the same manner that alluvium is now spread upon the bottom-lands of our rivers at their times of overflow. The occurrence of the loess in Guthrie, Carroll, Sac, and Buena Vista counties * in Iowa, covering the region next west of the terminal moraine, with its surface fifty feet above these drift-hills and one hundred above the undulating area of till adjoining their east side, proves that during the time of deposition of this part of the loess the ice- sheet extended to this limit, and was a barrier preventing the waters by which this sediment was brought from flowing over the lower area of till that reaches thence east to the Des Moines River. When the ice-sheet retreated beyond the water- shed of the Missouri basin, the principal source of these floods and their sediment was removed, and the subsequent work of the rivers which cross the area of the loess has been to excavate their present valleys or channels, bounded by bluffs of this formation. t A supplementary hypothesis to account for the subsidence assumed by some is, that a bodily depression of the crust of the earth was produced by the weight of the glacier. If one is inclined at first thought to reject this cause as moperative because of its relative insignificance, he should reflect that * “The Ninth Annual Report of the Geological and Natural History Survey of Minnesota,” p. 307 e¢ seq. + Ibid., pp. 337, 338. THE LOESS. 417 the forces maintaining the present contour of the earth’s sur- face may be very evenly balanced, so that a slight addition at one point, and subtraction from another, might be the de- cisive influence in turning the scale. It is now pretty gener- ally believed that the long-continued and steady periods of subsidence involved in the formation of extensive sediment- ary rocks was due to the constant accumulation of the silt, out of which the rocks are made. This silt was relieving the continents of its weight, and adding to the weight along the whole line of deposition. During the Glacial period the transference of water from the ocean to accumulate as ice upon land removed an immense pressure from the ocean- beds, and added an equal amount of weight to the glaciated area. How much influence this may have had in depressing temporarily this area and its margin, we are unable to tell. But it is one of those unknown causes in the field which may be supposed to have accomplished something. Professor Alexander Winchell has, in a recent interesting paper, suggested a correlation between this pressure of the ice over the glaciated region and the enormous outflows of lava along the Rocky Mountains and the Cascade Range on the Pacific slope.* The lava-beds of that region are enormous in extent and are certainly of very recent date, and seem to have poured out from long fissures instead of craters. Under- neath these beds there are, in California and Oregon, glacial deposits ; and it is in these lava-covered glacial deposits of southern California that human remains are supposed by Whitney to have been found. Professor Winchell’s theory connecting those lava outflows with the depression produced by the ice of the Glacial period in the east would relieve the subject of considerable embarrassment arising from the chronological difficulties that have been suggested. To the superficial objection that pressure over the Mississippi Valley would not produce volcanic eruptions at so great a distance * “Some Effect of Pressure of a Continental Glacier,” in “The American Geologist,” March, 1888, pp. 139-148. 418 THE ICE AGE IN NORTH AMERICA. as the Pacific coast, it is readily answered: “ The terrestrial globe in some of its behavior may be compared to an India- rubber ball filled with water. If indented by pressure in one place, there must be a protuberance equal in volume in another place. In a ball of uniform composition, the pro- tuberance would be spread over the entire surface beyond the region indented, and the effect in one particular spot might be insignificant. Should a small area of the caout- chouc be thinner than the rest, that part would be protruded to a greater extent than other parts of the surface. Should there be small holes or fissures through it, the water would escape and flow over the surface—that is, the protuberance resulting from local pressure would be chiefly on the outside of the shell. As we ordinarily conceive it, the water would be squeezed out like the juice of a squeezed orange.”* Another supplementary theory which has been invoked to account for the loess, is, that it has, in certain sections at least, been brought to the surface by the agency of earth- worms and other animals which burrow in the ground. The remarkable facts adduced by Mr. Darwin concerning the ac- tivity of these humble agents give respectability to the theory ; and, indeed, the power of these agencies can be seen by any observer who will take the pains to notice the count- less marks of angle-worms which frequently appear upon the surface of the soil after a rain. Mr. Darwin estimated that the amount of soil brought to the surface by worms was in one case at the rate of nearly two tenths of an inch a year. It is estimated, also, by competent authority, that the number of worms to an acre is as great as fifty-four thousand and that they would weigh three hundred and fifty-six pounds. Trustworthy estimates also show that these creatures some- times raise annually to the surface fourteen tons, and again eighteen tons, to the acre.t From this it is easily seen that the predominance of fine earth upon the surface is due to the * “Some Effect of Pressure of a Continental Glacier,” p. 139. + See Darwin, on “ Vegetable Mould and Earth-Worms,” chaps. iii and iv. THE LOESS. 419 work of such animals as worms, crayfish, and ants. But these creatures are limited in the depth to which they can pene- trate the soil and convey it to the surface. Still, it is not im- probable that in many places where the loess-like deposits are shallow it may be the result of these agencies. The twenty years which have elapsed since this chapter was written have been marked by continuous discussion of this puzzling problem of the loess. Butitssolution seems still about as far distant as ever. The Richthofen theory which accounts for its accumulation and distribution by wind has now more supporters than ever. But there is still a large residuum of facts that resist explanation on that theory alone. The loess of China has doubtless accumulated in the mountain- ous region bordering on Mongolia through the agency of wind, which has brought it in from the desert wastes which stretch westward to the “roof of the World” in Central Asia. But even so it is aquestion whether the material was not ultimately of glacial origin. In the revised edition of Geikie’s ‘“Great Ice Age’ it is rep- resented that an ice field covered eastern Mongolia which would presumably furnish the required glacial grist. But after the demonstration that eastern Mongolia never supported ice fields, the glacialists were compelled to resort to the theory that the wind had brought the material across the desert of Gobi, all the way from the base of the mountains, which on three sides surround the Tarim Valley. Here during the glacial period there was a great extension of glaciers in the Pamir and in the Tian Shan and the Himalaya mountains. It is to the floods pouring from the fronts of these glaciers that some would look for the supply of loess which the winds have brought into the mountain border of eastern Mongolia. It is difficult to say that this cause is not adequate to the effect, for the prevailing winds are westerly over this whole region and loess when once started could easily be driven at succes- sive stages for any requireddistance. I can add my personal 420 THE ICE AGE IN NORTH AMERICA. testimony to the extent and effects of the dust storms in east- ern Mongolia, where for a day at a time the dust raised by the wind was so dense that objects could not be distinguished half way acrosstheroad. And I have described immense drifts of loess near the summits of the mountains in that region five thousand feet above the sea, where it wasimpossibleto invoke the agency of water to account for the accumulation. __ But the investigations of Huntington and others seem to show that loess is not exclusively of glacial origin, but may be the finer product of subaérial disintegration, such as is going on all the while in desert regions such as exist in Central Asia and in the Rocky Mountain plateau. Still, whatever be the ultimate origin of the material, and however much influence we may attribute to the wind in transporting it from its original place of formation, water must be allowed a large share in its final distribution, and its accumulation belongs to a definite period corresponding to that of the glacial period. Itis perfectly evident to one who traverses the moun- tainous region of eastern Mongolia that loess is not now accumulating there through the agency of wind as fast as it is being removed by water, and carried down to the lower levels of the Yangtsi and Hoang rivers, and by them distrib- uted along the shores of the Chinese Sea. At the same time there are numerous level-topped areas of loess of great size all over northwestern China which indicate deposition by water. The same is true of the loess in the Mississippi and Mis- souri valleys. While it is doubtless true that in many places - the accumulations are due to wind, it is equally evident that there are many level-topped areas of loess along the borders of the Missouri which betoken the height reached by the overflowing floods of the stream when, as already shown, it was gorged by silt-laden water from the melting ice in the closing stages of the glacial period. Both wind and water had their share in the distribution. The absence of true ae THE LOESS. 421 water species of shells in the loess is what we should expect in an accumulation which took place in periodical or annual overflows. Land snails still love the flood-plains of variable streams. In the vicissitudes of the last stages of the glacial period we nave the temporary presence of water provided for to suit the habits of such shells as are found in the loess. Fie. 120.—Deep gulley in the loess at Helena, Arkansas. Courtesy of U.S. Geo. Sur- vey. Photo, by A, F, Crider, CHAPTER XVII. FLIGHT OF PLANTS AND ANIMALS DURING THE GLACIAL AGE. Awone the most interesting incidental effects of the Gla- cial period is that of its influence in distributing plants and animals over the lower latitudes. A glance at a polar pro- jection of the northern hemisphere shows to what a remark- able extent the land is clustered around the north pole, and how easy it would have been, under favorable conditions of climate, for plants and animals to spread from that vicinity along different meridians, till, in the lower latitudes, they should be on opposite sides of the earth. In conformity with these natural lines of emigration, it has long been known that both among plants and animals the species of _ the northern hemisphere are much more closely allied than those of the southern hémisphere, where no such land-con- nection exists; and, as we shall presently see, the problem presented by the hates of plants in the northern hemi- sphere is very complex and curious. For its solution we are largely indebted to the sagacity of the late Professor Asa Gray, who discovered the key in the influence of the Glacial period. In 1857, after he was already familiar, from private cor- respondence, with Darwin’s theory of the origin of species, Professor Gray was called upon to study the extensive botan- ical collections brought back from Japan by the expeditions of Commodores Perry and Rodgers. Comparison of these species with those in corresponding latitudes in other por- tions of the world brought out clearly—what had been FLIGHT OF PLANTS AND ANIMALS. 423 before but dimly perceived—that there was a remarkable resemblance between the existing plants of eastern Asia and those of eastern North America, that more species are com- mon to Japan and Europe than to Japan and western North iJ : " 9 5 F ia. 121.—Map showing how the land clusters about the North Pole. America, and that the resemblance is greatest of all between Japan and eastern North America. Out of three hundred species, common to the temperate regions of eastern Asia 424 THE ICE AGE IN NORTH AMERICA. and the corresponding region of North America, only one third is represented in western North America. The key applied by Professor Gray for the solution of this problem was suggested by the investigations of Heer and others, which had brought out the fact that, during the Ter- tiary period, just before the beginning of the Ice age, a tem- perate climate, corresponding to that of latitude 35° on the Atlantic coast, extended far up toward the north pole, per- mitting Greenland and Spitzbergen to be covered with trees and plants similar, in most respects, to those found at the present time in Virginia and North Carolina. Here, indeed, in close proximity to the north pole, were then residing, in harmony and contentment, the ancestors of nearly all the plants and animals which are now found in the north tem- perate zone, and here they would have continued to stay but for the cold breath of the approaching Ice age, which drove them from their homes, and compelled them to migrate to more hospitable latitudes. The picture of the flight and diapooul of these forests, and of their struggle to find, and adjust themselves to, other homes, is second in interest to that of no other migration. A single tree is helpless before such a force as an advancing glacier, since a tree alone can not migrate. But a forest of trees can. Trees can “take to the woods” when they can do nothing else, and so escape unfavorable conditions. There is a natural climatic belt to which the life of a forest is adjusted. In the present instance, as the favorable con- ditions near the poles were disturbed by the cooling influ- ences of the glacier approaching from the north, the indi- vidual trees on that side of the forest-belt gradually perished ; but, at the same time that the favorable conditions of life were contracting on the north, they were expanding on the south, so that along the southern belt the trees could gradu- ally advance into new territory, and so the whole forest-belt move southward, following the conditions favorable to its existence. It is therefore easy to conceive how, with the slow advance of the glacial conditions from the north, the FLIGHT OF PLANTS AND ANIMALS. 425 vegetation of Greenland and British America was transferred far down toward the torrid zone on both the Eastern and the Western Continent. Being once thus transferred, the forest would be compelled to remain there until the retreat of the ice began again to modify the conditions so as to compel a corresponding retreat of plants toward their original north- ern habitat. Thus it is that these descendants of the pre- glacial plants of Greenland, arrested in their northward march, have remained the characteristic flora of the latitudes near the glacial boundary. On the other hand, the arctic species, which can not endure even a temperate climate, and which must have accompanied the advancing glacier south- ward, found their natural conditions again in two ways: 1. By following closely upon the steps of the retreating ice to extreme northern latitudes; and, 2. To use Professor Gray’s happy expression, by “taking to the mountains,” and finding near their summits the necessary arctic conditions. It is thus that the mountains of New England and Labrador con- tain many species of plants nearly identical with those on the Alps in Europe. No better presentation of this subject can be given than that of Professor Gray himself, made in an address delivered in 1878, and which by the kindness of Mrs. Gray I am per- mitted in large part to reproduce in this connection : * The forests of the whole northern hemisphere in the tem- perate zone (those that we are concerned with) are mainly made up of the same or similar kinds. Not of the same spe- cies, for rarely do identical trees occur in any two or more widely separated regions; but all round the world in our zone the woods contain pines and firs and larches, cypresses and junipers, oaks and birches, willows and poplars, maples and ashes, and the like. Yet, with all these family likenesses throughout, each region has some peculiar features, some trees by which the country may at once be distinguished. * ““ Forest Geography and Archeology,” a lecture delivered before the Har- vard University Natural History Society, April 18, 1878, by Asa Gray. Printed in the “ American Journal of Science,” vol. cxvi, pp. 85-94, 183-196. 426 THE ICE AGH IN NORTH AMERICA. Beginning by a comparison of our Pacific with our Atlan- tic forests, it is to be noted that the greater part of the trees familiar on the Atlantic side of the continent are conspicu- ously absent from the Pacific forests. For example, the Pacific coast has no magnolias, no tulip- tree, no papaw, no linden or basswood, and is very poor in maples ; no locust-trees—neither flowering locust nor honey- locust—nor any leguminous tree; no cherry large enough for a timber-tree, like our wild black cherry ; no gum-trees (Wyssa nor Liquidambar), nor sorrel-tree, nor kalmia ; no persimmon, or bumelia; not a holly; only one ash that may be called a timber-tree ; no catalpa or sassafras; not a single elm, nor hackberry ; not a mulberry, nor planer-tree, nor maclura ; not a hickory, nor a beech, nor a true chestnut, nor a hornbeam ; barely one birch-tree, and that only far north, where the differ- ences are less striking. But as to coniferous trees, the only missing type is our bald cypress—the so-called cypress of our Southern swamps—and that deficiency is made up by other things. But as to ordinary trees, if you ask what takes the place in Oregon and California of all these missing kinds, which are familiar on our side of the continent, I must answer nothing, or nearly nothing. There is the madrofia (Arbutus) instead of our kalmia (both really trees in some places) ; and there is the California laurel instead of our Southern red bay- tree. Nor in any of the genera common to the two does the Pacific forest equal the Atlantic in species. It has not half as many maples, nor ashes, nor poplars, nor walnuts, nor birches, and those it has are of smaller size and of inferior quality ; it has not half as many oaks, and these and the ashes are of so inferior economic value that (as we are told) a passable wagon- wheel can not be made of California wood, nor a really good one in Oregon... . Now almost all these recur, in more or less similar but not identical species, in Japan, north China, etc. Some of them are likewise European, but more are not so. Extending the comparison to shrubs and herbs, it more and more appears that the forms and types which we count as peculiar to our Atlantic region, when we compare them, as we first naturally FLIGHT UF PLANTS AND ANIMALS. 427 do, with Europe and with our West, have their close counter- parts in Japan and north China; some in identical species (especially among the herbs), often in strikingly similar ones, not rarely as sole species of peculiar genera or in related ge- neric types. I was avery young botanist when I began to notice this, and I have from time to time made lists of such instances. Evidences of this remarkable relationship have multiplied year after year, until what was long a wonder has come to be so common that I should now not be greatly surprised if a Sarra- cenia or a Dionea, or their like, should turn up in eastern Asia. Very few such isolated types remain without counter- parts. It is as if Nature, when she had enough species of a genus to go round, dealt them fairly, one at least to each quar- ter of our zone; but when she had only two of some peculiar kind gave one to us and the other to Japan, Manchuria, or the Himalayas ; when she had only one, divided these between the two partners on the opposite side of the table. As to number of species generally, it can not be said that Europe and Pacific North America are at all in arrears ; but, as to trees, either the contrasted regions have been exceptionally favored or these have been hardly dealt with. There is, as I have intimated, some reason to adopt the latter alternative. We may take it for granted that the indigenous plants of any country, particularly the trees, have been selected by cli- mate. Whatever other influences or circumstances have been brought to bear upon them, or the trees have brought to bear on each other, no tree could hold its place as a member of any forest or flora which is not adapted to enduye even the extremes of the climate of the region or station. But the character of the climate will not explain the remarkable paucity of the trees which compose the indigenous European forest. That is proved by experiment, sufficiently prolonged in certain cases to justify the inference. Probably there is no tree of the north- ern temperate zone which will not flourish in some part of Europe. Great Britain alone can grow double or treble the number of trees that the Atlantic States can ; in all the latter we can grow hardly one tree of the Pacific coast. England supports all of them, and all our Atlantic trees also, and like- wise the Japanese and north Siberian species, which do thrive 428 THE ICE AGE IN NORTH AMERICA. here remarkably in some parts of the Atlantic coast, especially the cooler temperate ones. ‘The poverty of the European sylva is attributable to the absence of our Atlantic American types, to its having no magnolia, liriodendron, asimina, negundo, no Aischulus, none of that rich assemblage of leguminous trees represented by locusts, honey-locusts, gymnocladus, and cla- drastis (even its cercis, which is hardly European, is like the Californian one mainly a shrub) ; no Vyssa, nor Liquidambar ; no Hricacee rising to a tree; no bumelia, catalpa, sassafras, Osage orange, hickory, or walnut ; and, as to conifers, no hem- lock, spruce, arbor-vitz, taxodium, nor Torreya. As compared with northeastern Asia, Hurope wants most of these same types, also the ailantus, gingko, and a goodly number of conif- erous genera. I can not point to any types tending to make up the deficiency—that is, to any not either in east North America or in northeast Asia, or in both. Cedrus, the true cedar, which comes near to it, is only north African and Asian. I need not say that Kurope has no Sequoia, and shares no spe- cial type with California. Now, the capital fact is, that many and perhaps almost all of these genera of trees were well represented in Europe throughout the later Tertiary times. It had not only the same generic types, but in some cases even the same species, or what must pass as such, in the lack of recognizable distinctions be- tween fossil remains and living analogues. Probably the Eu- ropean Miocene forest was about as rich and various as is ours of the present day, and very like it. The Glacial period came - and passed, and these types have not survived there, nor re- turned. Hence the comparative poverty of the existing Eu- ropean sylva, or at least the probable explanation of the ab- sence of those kinds of trees which make the characteristic difference. Why did these trees perish out of Europe, but survive in America and Asia? Before we inquire how Europe lost them, it may be well to ask how it got them. How came these American trees to be in Europe? And among the rest, how came Europe to have Sequoias, now represented only by our two big trees of California? It actually possessed two species and more ; one so closely answering to the redwood of the Coast ——— FLIGHT OF PLANTS AND ANIMALS. 429 Ranges, and another so very like the Sequoia gigantea of the Sierra Nevada, that, if such fossil twigs with leaves and cones had been exhumed in California instead of Europe, it would confidently be affirmed that we had resurrected the veritable ancestors of our two giant trees. Indeed, so it may-probably be. Celum non animam mutant, etc., may be applicable even to such wide wanderings and such vast intervals of time. If the specific essence has not changed, and even if it has suffered some change, genealogical connection is to be inferred in all such cases. . . . I take it that the true explanation of the whole problem comes from a just general view, and not through piecemeal suppositions of chances. And I am clear that it is to be found by looking to the north, to the state of things at the arctic zone—first, as it now is, and then as it has been. North of our forest regions comes the zone unwooded from cold, the zone of arctic vegetation. In this, as a rule, the species are the same round the world ; as exceptions, some are restricted to a part of the circle. The polar projection of the earth down to the northern tropic shows to the eye—as our maps do not—how all the lands come together into one region, and how natural it may be for the same species, under homogeneous conditions, to spread over it. When we know, moreover, that sea and land have varied greatly since these species existed, we may well believe that any ocean-gaps, now in the way of equable distribution, may have been bridged over. There is now only one consid- erable gap. What would happen if a cold period were to come on from the north, and were very slowly to carry the present arctic cli- mate, or something like it, down far into the temperate zone ? Why, just what has happened in the Glacial period, when the refrigeration somehow pushed all these plants before it down to southern Europe, to middle Asia, to the middle and southern part of the United States ; and, at length receding, left some part of them stranded on the Pyrenees, the Alps, the Apennines, the Caucasus, on our White and Rocky Mountains, or wherever they could escape the increasing warmth as well by ascending mountains as by receding northward at lower levels. Those 430 THE ICE AGE IN NORTH AMERICA. that kept together at a low level, and made good their retreat, form the main body of present arctic vegetation. ‘Those that took to the mountains had their line of retreat cut off, and hold their positions on the mountain-tops under cover of the frigid climate due to elevation. ‘The conditions of these on different continents or different mountains are similar but not wholly alike. Some species proved better adapted to one, some to another, part of the world: where less adapted, or less adaptable, they have perished ; where better adapted, they con- tinue—with or without some change—and hence the diversifi- cation of Alpine plants as well as the general likeness through all the northern hemisphere. All this exactly applies to the temperate-zone vegetation, and to the trees that we are concerned with. ‘The clew was seized when the fossil botany of the high arctic regions came to light ; when it was demonstrated that in the times next pre- ceding the Glacial period—in the latest Tertiary—from Spitz- bergen and Iceland to Greenland and Kamchatka, a climate like that we now enjoy prevailed, and forests like those of New England and Virginia, and of California, clothed the land. We infer the climate from the trees; and the trees give sure ~ indications of the climate. I had divined and published the explanation long before I knew of the fossil plants. These, since made known, render the mference sure, and give us a clear idea of just what the climate was. At the time we speak of, Greenland, Spitzbergen, and our arctic sea-shore, had the climate of Pennsylvania and Virginia now. It would take too much time to enumerate the sorts of trees that have been identified by their leaves and fruits in the arctic later Tertiary deposits. I can only say, at large, that the same species have been found all round the world ; that the richest and most exten- sive finds are in Greenland ; that they comprise most of the sorts which I have spoken of, as American trees which once lived in EKurope—magnolias, sassafras, hickories, gum-trees, our identical Southern cypress (for all we can see of difference), and especially Seqguotas—not only the two which obviously answer to the two big trees now peculiar to California, but sev- eral others; that they equally comprise trees now peculiar to FLIGHT OF PLANTS AND ANIMALS. 431 Japan and China, three kinds of gingko-trees, for instance, one of them not evidently distinguishable from the Japan species which alone survives; that we have evidence not merely of pines and maples, poplars, birches, lindens, and whatever else characterize the temperate-zone forests of our era, but also of particular species of these, so hke those of our own time and country, that we may fairly reckon them as the ancestors of several of ours. Long genealogies always deal more or less in conjecture ; but we appear to be within the limits of scientific inference when we announce that our existing temperate trees came from the north, and within the bounds of high proba- bility when we claim not a few of them as the originals of present species. Remains of the same plants have been found fossil in our temperate region, as well as in Europe. Here, then, we have reached a fair answer to the question how the same or similar species of our trees came to be so dis- persed over such widely separated continents. The lands all diverge from a polar center, and their proximate portions— however different from their present configuration and extent, and however changed at different times—were once the home of those trees, when they flourished in a temperate climate. The cold period which followed, and which doubtless came on by very slow degrees during ages of time, must long before its culmination have brought down to our latitudes, with the similar climate, the forest they possess now, or rather the ancestors of it. During this long (and we may believe first) occupancy of Europe and the United States, were deposited in pools and shallow waters the cast leaves, fruits, and occasion- ally branches, which are imbedded in what are called Miocene Tertiary, or later deposits, most abundant in Europe, from which the American character of the vegetation of the period is inferred. Geologists give the same name to these beds in Greenland and southern Europe, because they contain the remains of identical and very similar species of plants; and they used to regard them as of the same age on account of this identity. But in fact this identity is good evidence that they can not besynchronous. The beds in the lower latitudes must be later. and were forming when Greenland probably had very nearly the climate which it has now. 432 THE ICE AGE IN NORTH AMERICA. Wherefore the high, and not the low, latitudes must be assumed as the birthplace of our present flora, and the present arctic vegetation is best regarded as derivative of the temperate. This flora, which, when circumpolar, was as nearly homogene- ous round the high latitudes as the arctic vegetation is now, when slowly translated into lower latitudes, would preserve its homogeneousness enough to account for the actual distribution of the same and similar species round the world, and for the original endowment of Kurope with what we now call Ameri- can types. It would also vary or be selected from by the in- creasing differentiation of climate in the divergent continents and on their different sides in a way which might well account for the present diversification. From an early period the sys- tem of the winds, the great ocean-currents (however they may have oscillated north and south), and the general proportions and features of the continents in our latitude (at least, of the American Continent), were much the same as now, so that species of plants, ever so little adapted or predisposed to cold winters and hot summers, would abide and be developed on the eastern side of continents, therefore in the Atlantic United States and in Japan and Manchuria: those with preference for milder winters would incline to the western sides; those disposed to tolerate dryness would tend to interiors or to re- gions lacking summer rain. So that, if the same thousand species were thrust promiscuously into these several districts, and carried slowly onward in the way supposed, they would inevitably be sifted in such a manner that the survival of the fittest for each district might explain the present diversity. Besides, there are resiftings to take into the account. The Glacial period or refrigeration from the north, which at its inception forced the temperate flora into our latitude, at its culmination must have carried much or most of it quite beyond. To what extent displaced, and how far superseded by the vege- tation which in our day borders the ice, or by ice itself, it is difficult to form more than general conjectures, so different and conflicting are the views of geologists upon the Glacial period. But upon any, or almost any, of these views it is safe to conclude that temperate vegetation, such as preceded the ~ refrigeration, and has now again succeeded it, was either thrust FLIGHT OF PLANTS AND ANIMALS. _ 433 out of northern Europe and the northern Atlantic States or was reduced to precarious existence and diminished forms. It also appears that, on our own continent at least, a milder cli- mate than the present, and a considerable submergence of land, transiently supervened at the north, to which the vegetation must have sensibly responded by a northward movement, from which it afterward receded. All these vicissitudes must have left their impress upon the actual vegetation, and particularly upon the trees. They furnish probable reason for the loss of American types sus- tained by Europe. _ I conceive that three things have conspired to this loss: 1. Europe, hardly extending south of latitude 40°, is all within the limits generally assigned to severe glacial action. 2. Its mountains trend east and west, from the Pyrenees to the Car- pathians and the Caucasus beyond, near its southern border ; and they had glaciers of their own, which must have begun their operations, and poured down the northward flanks, while the plains were still covered with forest on the retreat from the great ice-wave coming from the north. Attacked both on front and rear, much of the forest must have perished then and there. 3. Across the’line of retreat of those which may have flanked the mountain-ranges, or were stationed south of them, stretched the Mediterranean, an impassable barrier. Some hardy trees may have eked out their existence on the northern shore of the Mediterranean and the Atlantic coast. But, we doubt not, taxodium and Sequotias, magnolias, and Liquidambars, and even hickovies and the like, were among the missing. Escape by the east, and rehabilitation from that quarter until a very late period, was apparently prevented by - the prolongation of the Mediterranean to the Caspian, and thence to the Siberian Ocean. If we accept the supposition of Nordenskidld, that, anterior to the Glacial period, Europe was ‘‘bounded on the south by an ocean extending from the Atlantic over the present deserts of Sahara and central Asia to the Pacific,” all chance of these American types having escaped from or re-entered Europe from the south and east is excluded. Europe may thus be conceived to have been for a time somewhat in the condition in which Greenland 1s now, 434 THE ICH AGE IN NORTH AMERICA. and, indeed, to have been connected with Greenland in this or in earlier times. Such a junction, cutting off access of the Gulf Stream to the Polar Sea, would, as some think, other things remaining as they are, almost of itself give glaciation to Europe. Greenland may be referred to, by way of compari- son, as a country which, having undergone extreme glaciation, bears the marks of it in the extreme poverty of its flora, and in the absence of the plants to which its southern portion, extending six degrees below the Arctic Circle, might be entitled. It ought to have trees, and might support them. But, since destruction by glaciation, no way has been open for their re- turn. Europe fared much better, but suffered in its degree in a similar way. Turning for a moment to the American Continent for a contrast, we find the land unbroken and open down to the tropic, and the mountains running north and south. The trees, when touched on the north by the on-coming retrigera- tion, had only to move their southern border southward, along an open way, as far as the exigency required ; and there was no impediment to their due return. Then the more southern latitude of the United States gave great advantage over Ku- rope. On the Atlantic border, proper glaciation was felt only in the northern part, down to about latitude 40°. In the in- terior of the country, owing doubtless to greater dryness and summer heat, the limit receded greatly northward in the Mis- sissippi Valley, and gave only local glaciers to the Rocky Mountains ; and no volcanic outbreaks or violent changes of any kind have here occurred since the types of our present vegetation came to the land. So our lines have been cast in pleasant places, and the goodly heritage of forest-trees is one of the consequences. fs The still greater richness of northeastern Asia m arboreal vegetation may find explanation in the prevalence of particu- larly favorable conditions, both ante-glacial and recent. The trees of the Miocene circumpolar forest appear to have found there a secure home; and the Japanese Islands, to which most of these trees belong, must be remarkably adapted to them. The situation of these islands—analogous to that of Great Britain, but with the advantage of lower latitude and greater FLIGHT OF PLANTS AND ANIMALS. 435 sunshine—their ample extent north and south, their diversified configuration, their proximity to the great Pacific Gulf Stream, - by which a vast body of warm water sweeps along their accentu- ated shores, and the comparatively equable diffusion of rain throughout the year, all probably conspire to the preservation and development of an originally ample inheritance. The case of the Pacific forest is remarkable and paradoxi- cal. It is, as we know, the sole refuge of the most character- istic and wide-spread type of Miocene Conifere, the Sequovas ; it is rich in coniferous types beyond any country except Japan ; in its gold-bearing gravels are indications that it possessed, seemingly down to the very beginning of the Glacial period, Magnolias and beeches, a true chestnut, Liquidambar, elms, and other trees now wholly wanting to that side of the conti- nent, though common both to Japan and to Atlantic North America. Any attempted explanation of this extreme paucity of the usually major constituents of forest, along with a great development of the minor or coniferous element, would take us quite too far, and would bring us to mere conjectures. Much may be attributed to late glaciation ; something to the tremendous outpours of lava which, immediately before _the period of refrigeration, deeply covered a very large part of the forest area ; much to the narrowness of the forest-belt, to the want of summer rain, and to the most unequal and pre- carious distribution of that of winter. Upon all these topics questions open which we are not pre- pared to discuss. I have done all I could hope to do in one lecture if I have distinctly shown that the races of trees, like the races of men, have come down to us through a prehistoric (or pre-natural-historic) period ; and that the explanation of the present condition is to be sought in the past, and traced in vestiges, and remains, and survivals; that for the vegetable kingdom also there is a veritable archeology. As the truth of a theory needs to be tested by the meth- od of difference as well as of agreement, we turn to inquire if it be not true that all mountains which reach above the snow-line have an Alpine flora, and whether it be not the conditions themselves which determine the peculiarities ? 436 THE ICE AGE IN NORTH AMERICA. These questions are answered by an appeal to certain oceanic islands which were outside the influence of continental glacia- tion. According to Wallace, a striking proof of the theory presented by Professor Gray ‘is found on the Peak of Ten- eriffe, a mountain 12,000 feet high. In the uppermost 4,500 feet of this mountain above the limit of trees, Von Buch found only eleven species of plants, eight of which were peculiar; but the whole were allied to those found at lower elevations. On the Alps or Pyrenees, at this elevation, there would be a rich flora comprising hundreds of arctic plants ; and the absence of anything corresponding to them in this case, in which their ingress was cut off by the sea, is exactly what the theory leads us to expect.” * On both continents, at the close of the Tertiary period, there occurred a remarkable extinction of animals which is doubtless connected with the advance of the continental ice- sheet. Among these we may mention two species of the cat family as large as lions; four species of the dog family, some of them larger than wolves; two species of bears; a walrus, found in Virginia; three species of dolphins, found in the Eastern States; two species of the sea-cow, found in . Florida and South Carolina; six species of the horse; the existing South American tapir; a species of the South Amer- ican llama; a camel; two species of bison; three species of © sheep; two species of elephants and two of mastodons; a species of Megatherium, three of Megalonyx, and one of Mylodon—huge terrestial sloths as large as the rhinoceros, or even as large as elephants, which ranged over the Southern States to Pennsylvania, and the Mylodon as far as the Great Lakes and Oregon.t This wondrous assemblage of animals became extinct upon the approach of the Glacial period, as their remains are all found in post-Pliocene deposits. The intermingling of forms is remarkable. The horses, camels, and elephants which * “The Geographical Distribution of Animals,” vol. i, p. 43. + Ibid., p. 129. FLIGHT OF PLANTS AND ANIMALS. 437 lived in North America before the Glacial period were found subsequent to the Glacial period only in the Old World, while the llamas, tapirs, and gigantic Hdendata are South American types. The progress of events seems to Lave been about as follows: In the warm period preceding the Glacial epoch, when the vegetation of the temperate zone flourished about the north pole, there was land connection between the continents, permitting the larger species of the Old World to migrate to North America. At the same time the con- ditions in North America were favorable to the tropical spe- cies of animals which had developed and flourished in South America. The refrigeration of the climate on the approach of the Glacial period, and the advance of the ice from the north, cut off retreat to the Old World species, and gradually hemmed them in over the southern portion of the continent, where all forms of life were compelled to readjust themselves to new conditions. The struggle for existence probably re- sulted, first, in the extinction of those South American spe- cies which had invaded North America during the warmer climate of later Tertiary times; and the more hardy emi- grants from the north would have the advantage from the similarity in climate in the southern United States during the Glacial period to that about the poles, where they had flourished immediately before. With the withdrawal of ice to the north, the struggle of these animals with the condition of existence began anew, and the mammoth and some others found themselves unable to cope with the changes to which they were compelled to adjust themselves. From the abun- dance of remains of these animals found in the peat-bogs of kettle-holes and in the glacial terraces of gravel and loess, it is evident that they followed close upon the retreating ice- front, and some of them continued the retreat to the Arctic Circle, where they still live and flourish; while others, like the elephant and mastodon, perished. Few things are better calculated to impress the scientific imagination than this dispersion and final extinction in North America of so many large animals native to the Old World; 438 THE ICE AGE IN NORTH AMERICA. while some of them, like the horse, were admirably adapted to the present conditions, as is shown by their rapid increase since their introduction after the discovery of America by the whites. In a succeeding chapter we shall also see that man himself participated in this struggle with the new con- ditions introduced by the Glacial period on this continent, and that, in company with the mammoth, walrus, and other arctic species, he followed up the retreating ice both upon the Atlantic coast and in the Mississippi Valley. Whether, like some of his companions, he was unsuccessful in the con- test is not certain, though there is much to be said in favor of the theory that the Eskimos of the north are the lineal descendants of the preglacial men whose implements are found in New Jersey, Ohio, and Minnesota. Much also may be said to support the theory, alluded to by Professor Olay- pole, connecting the traditions of the destruction of large portions of the human race by a flood with the extermination of species naturally brought about by the conditions accom- panying the floods which closed the Glacial period. It is interesting to observe, also, that insects as well as plants and the larger animals were compelled to reckon with the Glacial period. They, too, participated in the southern migration enforced by the advancing ice, and also shared in the vicissitudes of its final retreat, compelling them to escape from the warmer belt of climate which again advanced upon them from the south. Like the forms of arctic and Alpine vegeta- tion, a portion of the insects also took to the mountains, where they still remain, as living witnesses to the reality of the Glacial period. The summits of the White Mountains are characterized by Alpine species of insects, one of which is thus described by Mr. Samuel Seudder : But even the narrow limit of the Alpine zone of the White Mountains claims for its own a single butterfly, which probably has a more restricted range than any other in the world. One may search the season through over the comparatively vast and almost equally barren elevations within the sub-Alpine district of the White Mountains and fail to discover more than here FLIGHT OF PLANTS AND ANIMALS. 439 and there a solitary individual whirled by fierce blasts down the mountain-slopes, while, a few hundred feet above, the but- terflies swarm in great numbers. Every passage of the sun from behind a cloud brings them out in scores, and they may often be captured as fast as they can be properly secured. The contrast between the occasional and unwilling visitor in the sub-Alpine region and the swarms which flutter about the upper plateaus is most significant. Yet the Carices, the food- plant of the caterpillar, are quite as abundant in the lower regions as in the upper, even to the species C. rigida, upon which I found the larva feeding. Now, this butterfly (@nevs semidea) belongs to a genus which is peculiar to Alpine and arctic regions ; in fact, it is the only genus of butterflies which is exclusively confined to them. It has numerous members, both in this country and in the Old World. One is confined to the Alps of Europe ; most of the European species, however, are found only in the extreme north. The genus extends across the whole continent of America, and several of its spe- cies occur on the highest elevations of the Rocky Mountains. Several species are common to Europe and America, and it is to one of these that @neis senndea is most closely allied. A few species descend into the Hudsonian fauna, but, as a whole, the genus has its metropolis farther north. So that, im ascend- ing Mount Washington, we pass, as it were, from New Hamp- shire to northern Labrador; on leaving the forests, we come first upon animals recalling those of the northern shores of the Gulf of St. Lawrence and the coast of Labrador opposite New- foundland ; and, when we have attained the summit, we find insects which represent the fauna of Atlantic Labrador and the southern extremity of Greenland.* Commenting upon these and similar facts connected with other species of butterflies and with several species of moths, Mr. A. R. Grote pertinently says : + The question comes up with regard to the White Mountain butterfly, as to the manner in which this species of Geis —— * “Geology of New Hampshire,” vol. i, pp. 340, 341. + “ American Journal of Science,” vol. cx, 1875, pp. 337, 338. 440 THE ICE AGH IN NORTH AMERICA. attained its present restricted geographical area. ... How did the White Mountain butterfly get up the White Mount- ains? Iam disposed to answer, by the action attendant on the decline of the Glacial period. . The main ice-sheet had nae ‘Hien insensibly before it, and, during the continuance of the Glacial period, the geo- graphical distribution of the genus Geis had been changed from a high northern region to one which may well have in- cluded portions of the Southern States. And, on its decline, the ice-sheet drew them back again after itself by easy stages ; yet not all of them. Some of these butterflies strayed by the way, detained by the physical nature of the country, and destined to plant colonies apart from their companions. When the main ice-sheet left the foot of the White Mountains, on its long march back to the pole, where it now seems to rest, some of these wayward, flitting Geis butterflies were left behind. These had strayed up behind the local glaciers on Mount Washington, and so became separated from the main body of their companions, which latter journeyed northward, follow- ing the course of the retirement of the main ice-sheet. They had found in elevation their congenial climate, and they have followed this gradually to the top of the mountain, which they have now attained, and from which they can not now retreat. Far off mm Labrador the descendants of their ancestral com- panions fly over wide stretches of country, while they appear to be in prison on the top of a mountain. I conceive that in this way the mountains may generally have secured their Alpine animals. The Glacial period can not be said strictly to have expired. It exists even now for high levels above the sea, while the Eskimos find it yet enduring in the far north. Had other conditions been favorable, we might now find arctic man living on snow-capped mountains within the temperate zone. At a height of from 5,600 to 6,200 feet above the level of the sea, and a mean temperature of about 48° during a short summer, the White Mountain butterflies (Geis semidea) yet enjoy a climate like that of Labrador within the limits of New Hampshire. And in the case of moths an analogous state of things exists. The species Anarta melanopa is four _on Mount FLIGHT OF PLANTS AND ANIMALS. 441 Washington, the Rocky Mountains, and in Labrador. > : Yip Ll 02 XN “4 G dr, 4 My MD Yj yy fy eed Y Te Sima tedy, AT ae iJ : VEST SAS THE CAUSE OF THE GLACIAL PERIOD. 475 occur in aphelion—that is, when the earth is farthest away from the sun, and are seven days longer than the summers. While admitting that there is not as yet enough known about the laws governing the absorption and retention of the sun’s heat upon the earth’s surface to permit us to say with confi- dence that the acknowledged glacial condition of the southern hemisphere is not produced by the astronomical cause under consideration, it must be added that we are also unable to prove the inadequacy of other causes to produce the same results. In assuming the reality of Mr. Croll’s cause, we are in danger of resting on a theoretical may be rather than on well-established premises. At any rate, Woeikoff, in the ablest review that has yet appeared upon the subject, thinks the glaciation of the southern hemisphere may readily enough be accounted for without the aid of Croll’s theory, and sums up the case thus: The extent and depth of the oceans of the southern hemi- sphere give a greater steadiness and force to the winds of that hemisphere, and the difference is even more marked if we com- pare the westerly winds of middle latitudes rather than the trades, though also well seen in the latter. Now, land acts in two ways on the trade-winds: it weakens them, first, by the increase of friction. But this is not all. The trades, few ocean regions excepted, are not strong winds; they are impor- tant on account of their extent and steadiness. The gradient which causes them is small. Now, in such cases, land, even if it is not a continent but only a cluster of small islands, has a great influence on trade-winds in causing local gradients which may have even an opposite direction to the general gradients, thus causing different and even opposing winds. ‘The land- and sea-breezes and the monsoons are cases in point. Even where the disturbances of the normal ocean gradients are not large enough to cause monsoons, we see generally the trades oftener interrupted in summer, when they are weaker and when local thunder-storms and rains are more frequent on land. For the two reasons given, the trades of the southern hemi- sphere must be more extensive and stronger than those of the northern. 476 THE ICE AGE IN NORTH AMERICA. . The relatively small extent of sea in middle latitudes of the northern hemisphere, in comparison with the southern, must tend to warm the seas of the former, even if the quantity of warm water from the tropical seas reaching them be equal. Thus, generally in the middle latitudes the evaporation goes on at a higher temperature from the seas of the northern than the southern hemisphere. Now, this has a very great influ- ence on the resulting precipitations; when the evaporation goes on at or near 32°, there is much more probability that the resulting precipitation will be snow and not rain, even on low lands ; the higher the temperature at which the evaporation takes place, the greater must be the height at which snow can fall, on account of cooling by expansion. Not all cold seas are favorable to glaciation. If they are surrounded by land on which the winters have a temperature considerably below 32°, they will be covered with ice, and thus evaporation will be checked just at the time when it is most favorable to snow-fall. The ice of the seas will be covered with snow, the temperature of the air over it may be very low, but the snow-fall will not be great, and thus the conditions not favorable to glaciation. Such is the condition of many seas of the northern hemisphere, as the Arctic Ocean north of Siberia, the Kara Sea, the bays and inlets north of the North American Continent, the Sea of Okhotsk, etc., which are covered with ice during many months. These conditions are favorable to cold of many months’ duration, but not to a large snow-fall and the resulting glaciation. The observations made at many points off the coasts of Siberia and the North American Archi- pelago have shown that the snow-fall is exceedingly light. The seas between 45° and 70° of southern latitnde are deep and not surrounded by land, and thus by far not so ice-bound, both on account of the absence of very low temperatures favorable to the formation of ice, and of the rupture of ice, when formed, by winds and currents. * Thus it is shown that the depth and relative extent of the southern ocean furnish a sufficient cause for its present glacial conditions. | * “ American Journal of Science,” vol. cxxxi, 1886, pp. 175, 176. THE CAUSE OF THE GLACIAL PERIOD. AT7 As already intimated, the weak point in Mr. Crol!l’s the- ory is the general state of uncertainty as to the laws regulat- ing the absorption, retention, and distribution of the sun’s heat upon the earth. It is evident that the heat upon. which the earth is dependent is that of the sun; since, as Professor Newcomb has shown, the total amount of heat received from the stars is probably not one-millionth part of that received from the sun.* Now, as all admit that the annual amount of heat received from the sun is not affected by changes either in the eccentricity of the earth’s orbit, or in the rela- tion of the poles to that eccentricity, it is only the question of the retention and distribution of heat with which we have to do. And here we come to a most obscure realm of sci- entific investigation, where ignorance is still profound. The reason why the summit of a mountain is cold is not because of lack of heat from the sun, but it arises rather from the facility with which the heat is dissipated by radiation. On the contrary, the reason why the atmosphere of a greenhouse is warmer than that upon the outside is not because it recewes more heat, but because it retazns more. The intenser heat- rays of the sun readily penetrate the glass cover, while the less intense rays of radiated heat from the earth are unable to do so inreturn. It is well known, also, that clouds pre- vent a frost by checking the radiation from the surface of the earth. The laws regulating the influence of the atmosphere and the floating particles contained in it, over the retention of the sun’s heat in its lower strata, are as yet but little un- derstood. There is here an almost unlimited field for inves- tigation and discovery. And this, as just remarked, is the weak point of Mr. Croll’s theory. Everything here depends upon the forces which distribute the heat and moisture over the land-sur- faces. It is by no means certain that, when the winters of the northern hemisphere occur in aphelion, they will be colder than now. Whether they would be so or not depends * “ American Journal of Science,” vol. cxi, 1876, p. 264; vol. cxxvii, 1884, p. 22. 478 THE ICE AGH IN NORTH AMERICA. upon the action of forces whose laws can not now be accurately calculated. As Woeikoff goes on to show, there are some very singular facts in the distribution of heat over the earth’s sur- face—proving that the equator is not so hot as theoretically it ought to be, and that the arctic regions are not so cold ; and this in places which could not be affected by oceanic currents. - For example, at Iquitos, on the Amazon, only three hundred feet above tide, three degrees and a half south of the equator, and more than a thousand miles from the Atlantic (so that ocean-currents can not abstract the heat from its vicinity), the mean yearly temperature is but 78° Fahr., while at Verkhojansk, in northeast Siberia, which is 67° north of the equator, and is situated where it is out of the reach of ocean- currents, and where the conditions for the radiation of heat are most favorable, and where, indeed, the winter is the coldest on the globe (January averaging —56° Fahr.) the mean yearly temperature is two degrees and a half above zero; so that the difference between the temperature upon the equator and that at the coldest point on the sixty-seventh parallel is only about 75° Fahr.; whereas, if temperature were in proportion to heat received from the sun, the difference ought to be 172°. Again, the difference between the actual January temperature on the fiftieth parallel and that upon the sixtieth is but 20° Fahr., whereas, the quantity of solar heat received on the fiftieth parallel during the month of January is three times that received upon the sixtieth, and the difference in temperature ought to be about 170° Fahr. upon any known law in the ease. But to be quite sure to get’ beyond the influence of ocean- currents, I will take the mean January temperature in the strictly continental climate of eastern Siberia, under 120° east. According to Ferrel’s tables : Under 50° north we have 0° Fahr. Under 60° north we have —30° Fahr. If the January temperature decreased from 50° to 60° north, - according to the hypothesis of Dr. Croll, it should be on the 60° north —155° Fahr. ; } t : : THE CAUSE OF THE GLACIAL PERIOD. 479 But to be quite sure of taking the most favorable case for the hypothesis of Dr. Croll, | take the highest January tem- perature on the 50° north in Ferrel’s tables, that is, that on 20° east =44° Fahr., and the coldest January temperature on the 60° north, that is, that of 120° and 130° east, = —30° Fahr. Yet in proportion to the quantity of heat received, the mean temperature of January on 60° north should be —140° Fahr. The following table gives the results of the three cases con- sidered : ieee TEMPERATURE, 60° N. Mean tem- | | Siok aS ~ | Difference. ou° N. =| On the hypothe-, sis of Dr-Croll, | Actual Mean January temperature of MOMHETICIANG.: 5. .)-cc cub ods ce 21°3 — 1479 al 149°6 Mean January temperature in 120° EK. (east Siberia)........ Ne — 155°3 —30 125°3 Mean January temperature of warmest meridian 50° N., and coldest meridian on 60° N.... 44:0 — 1400 —30 | 110:0* These facts, and many others like them, make it evident that we understand very little about the laws governing the distribution of heat over the surface of the earth. Other things besides ocean-currents are active in the matter, and some of them must be far more potent than any cause which we now clearly discern. We quote again the words of the same high authority: How can we judge of the change of temperature resulting from this or that distance from the sun, even if we knew accu- rately the temperature of space, when we do not know the dia- thermancy of the atmosphere under different conditions? We know only that it is exceedingly different, according to the different quantities of carbonic acid and aqueous vapor con- tained in it, and in a far higher degree, according to the ab- sence or presence in different quantities of suspended liquid and solid particles (clouds, dust, smoke, etc.). Thus, when * Woeikoff in “ American Journal ef Science,” vol. cxxxi, p. 166. 480 THE ICE AGE IN NORTH AMERICA. we do not know in how far the loss of heat is impeded, even an accurate knowledge of the temperature of space would be of small use in this matter. I will illustrate this by a homely example. Take a room where the fire is extinguished and the hearth or stove cold in the evening, and try to guess at the temperature the room will have in the morning. If we follow the method of Dr. Croll, we should inquire only about the out- side temperature, and not about the thickness of the walls, the windows, etc. I think that, taking the average construction of Russian, English, and Italian houses, if the inside tempera- ture was in all three cases 60° in the evening, and the outside temperature 20° in Russia, 32° in England, and 45° in Italy, the morning temperature in the room would not be very differ- ent, and probably even higher in the Russian room, owing to its thick walls, double windows, ete. Thus it is easy to see that the question how great will be the temperature of the air at a given place, say in midwinter, when the distance of the sun is greater or less than at present, can not be answered, even approximatively, especially in the exceedingly crude way it is put by Dr. Croll—that is, without distinguishing high and low latitudes, continent and ocean, ete. One thing is certain, that such a change will certainly have a greater influence on the temperatures in the interior of continents than on the oceans and their borders. The caloric capacity of water is so great, and the mobility of its particles so effectual in resisting a lowering of the surface temperature, by the convection currents it causes, that I doubt very much if, during a great eccentricity and winter in aphelion, the sur- face temperature of the oceans can be lower in winter than now ; the difference in the quantity of sun-heat is too small and too short-continued to give an appreciable difference in winter ; and, as in the year there is no difference in the quan- tity of heat received by the waters, I think there will be no difference in the temperature of the waters, and thus no influ- ence of great eccentricity with winter in aphelion on the ocean temperatures, and also no greater snow-fall than now. As to the continents, I admit that, though we are wnabdle to calculate the rate of decrease of temperature of the winter months in these conditions, there is no doubt that ¢¢ will be appreciable, and be THE CAUSE OF THE GLACIAL PERIOD. 481 the greater the less a given place is under the influence of the seas. * We may test the theory still further by an appeal to geo- logical facts. According to Mr. Croll, there must have been a succession of glacial periods in the past, and it would seem that numerous indications of such. epochs, if they occurred, must exist in the successive geological strata. If such indi- cations are not found in requisite amount, the advocates of Mr. Croll’s theory are bound to give a satisfactory explana- tion of the failure. To a consideration of this evidence Mr. Croll devotes the seventeenth and eighteenth chapters of his book on “ Climate and Time,” and at the outset confesses that “ the facts which have been recorded as evidence in favor of the action of ice in former geological epochs are very scanty indeed.” To ac-. count for this deficiency of evidence, he adduces, first, “ the imperfection of the geological records themselves; and, sec- ond, the little attention hitherto paid toward researches of this kind.” | Mr. Croll’s presentation of the reasons, from the nature of the case, why the evidence of glaciation in the earlier geo- logical periods should be in large degree obliterated, is prob- ably as strong as can be made. He argues that the present land-surfaces in nearly all cases represent former ocean-beds, hence sedimentary strata deposited during the Glacial age must consist of the water-worn material which had been car- ried out from glacial streams into the bordering seas and oceans, so that the most distinct signs of glacial action which we could expect to find in sedimentary strata would be de- posits of pebbles, forming conglomerate rocks, and the oceur- rence in these conglomerates of occasional angular fragments, such as could only be transported on ice. Mr. Croll, also, very naturally, dwells upon the extent to which the land-surfaces exposed between two geological epochs must have suffered from denudation. Erosive agen- * Woeikoff in “ American Journal of Science,” vol. cxxxi, pp. 169, 172. 482 THE ICE AGH IN NORTH AMERICA. cies would operate in the ordinary way during the whole period of elevation, the streams carrying down to the sea a large amount of material everyseason. But when the period of depression had proceeded so far as to bring the surface below the level of the sea, Mr. Croll believes the action of the waves would greatly hasten the operation, and would thoroughly sort out and roll the pebbles, washing the finer particles into deeper water. A careful consideration of the forces in operation, how- ever, does not seem wholly to justify this reasoning of Mr. Croll. In the first place, there must have been at various geological epochs, over the area now most studied, extensive land exposures, continuing through a long period of time. The Tertiary deposits contain many vegetable remains as well as animal, showing the existence of land areas of no small extent. The Carboniferous period reveals whole con- tinents maintaining, over a large portion of their extent, an elevation near the sea-level, in which there were continual but slight oscillations, tending, however, on the whole to subsidence. So that land-plants accumulated in sufficient quantity to form the coal-beds—the periods of depression being marked by sedimentary rocks formed by the consolida- tion of the wash that was spread over the whole region dur- ing the times of depression. Now, it does not seem possible that a glaciated area so ex- tensive as is that of North America, and so deeply covered with glacial débris, could be so completely removed by or- dinary denuding agencies that no more signs of it should appear than are found of such phenomena in the earlier geo- logical epochs; for the till, or ground-moraine, is not readily removed' by the action of water, even where subjected to the shore-waves of the ocean. The bowlders which are washed out of it form a protecting barricade around the base of the deposit, so that islands like those in Boston Harbor, com- posed wholly of till, are as nearly proof against the waves as are those of ordinary rocks. If there were in progress a sub- sidence of the glaciated area of North America, instead of THE CAUSE OF THE GLACIAL PERIOD. 483 having the waves wash the glaciated surfaces away gradually from the edges inward, we should find merely an encroaci- ment made here and there upon the border during a portion of the subsidence, until, finally, when the waters covered the whole, all but a very thin stratum of the upper portion would be protected from further disturbance. Especially must the till remain in the innumerable buried channels of the glaci- ated region, and over the extensive protected northern slopes. It is thus difficult to conceive how there should ever be any such complete removal of the ground-moraine from the im- mense glaciated area of North America as Mr. Croll sup- poses to have occurred several times over in preceding gla- cial epochs. The facts supposed to prove, by direct evidence, the ex- istence of glacial periods in the various successive geological epochs, can be briefly stated.* Beginning with some of the oldest sedimentary strata, Professor Archibald Geikie has discovered what he believes to be unmistakable signs of glacial action in the north of Scotland, in Sutherlandshire, on rocks of Cambrian age— that is, just below the base of the Silurian system. Here he reports extensive surfaces of gneiss rock worn into the char- acteristic “rounded bossy surface” of glaciated regions, and this evidently runs under an extensive deposit of breccia of glacial origin, made up of fragments eroded by ice at that early period of glaciation.t Some of the fragments of this overlying breccia are said to be from five to six feet long. A second instance of early glaciation, mentioned by Pro- fessor Ramsay, occurs in the south of Scotland, in Ayrshire and Wigtonshire, in the Lower Silurian formations of that region. Here are extensive sedimentary rocks, containing * On the whole, the best summary of the evidence upon this subject, and the one to which we are mainly indebted for the facts here presented, was given by Sir A. C. Ramsay, Director-General of the Geological Survey of the United King- dom, in his Presidential Address before the British Association of Swansea in 1880. (See “ Nature,” vol. xxii, p. 388 ef seq.) + See communication to “‘ Nature,” vol. xxii, pp. 400-403. 484: THE ICE AGE IN NORTH AMERICA. characteristic Lower Silurian fossils, in which are numerous erratic blocks of gneiss and granite, some of them as many as — nine feet in length. Both Dr. Ramsay and Mr. James Geikie — believe that the nearest source from which these fragments could come is one hundred miles or more to the north. Their theory is that, in the eariy Silurian times, the region oceu- pied by the Hebrides and the adjoining coast of northern Scotland consisted of an immense granitic mountain uplift, down which glaciers descended to the sea, sending off bowlder- laden icebergs, which wandered to the vicinity of Ayrshire and Wigtonshire, and there dropped their burdens. In India, also, according to Dr. Ramsay, Medlicott and Blanford describe “old slates supposed to be Silurian, con- taining bowlders in great numbers,” which these experienced authorities believe to be of glacial origin. They also de- scribe other very ancient transition beds which overlie rocks “marked by distinct glacial striations.” Again, Dr. Ramsay describes bowlder-beds in the south of Scotland, on the Lam- mermoor Hills, south of Dunbar, which “ contain what seem to be indistinctly ice-scratched stones.’ These beds lie “ un- conformably on Lower Silurian strata,” and are now gener- ally believed by the members of the Geological Survey of Scotland to be of glacial origin. Dr. Ramsay goes on to say: I know of no bowlder formations in the Carboniferous series, but they are well known as occurring on a large scale in the Permian brecciated conglomerates, where they consist of peb- bles and large blocks of stone, generally angular, imbedded in a marly paste; . . . the fragments have mostly traveled from a distance, apparently from the borders of Wales, and some of them are three feet in diameter. Some of the stones are as well scratched as those found in modern moraines or in the ordinary bowlder-clay of what is commonly called the Glacial epoch. In 1855 the old idea was still not unprevalent that during the Permian epoch, and for long after, the globe had not yet cooled sufficiently to allow of the climates of the exter- nal world being universally affected by the constant radiation of heat from its interior. For a long time, however, this idea THE CAUSE OF THE GLACIAL PERIOD. 4895 has almost entirely vanished, and now, in Britain at all events, it is little if at all attended to, and other glacial episodes in the history of the world have continued to be brought forward and are no longer looked upon as mere ill-judged conjectures, The same kind of brecciated bowlder-beds that are found in our Permian strata occur in the Rotheliegende of Germany, which I have visited in several places, and I believe them to have had a like glacial origin. Mr. G. W. Stow, of the Orange Free State, has - late years given most elaborate accounts of similar Permian bowlder-beds in South Africa. There great masses of moraine matter not only contain ice-scratched stones, but on the banks of rivers where the Permian rock has been removed by aqueous denuda- tion the underlying rocks, well rounded and mammillated, are covered by deeply incised glacier grooves pointing in a direction which at length leads the observer to the pre-Permian mount- ains whence the stones were derived that formed these ancient moraines. | Messrs. Blanford and Medlicott have also given, in ‘“‘ The Geology of India,” an account of bowlder-beds in what they believe to be Permian strata, and which they compare with those described by me in England many years before. There the Talchir strata of the Gondwana group contain numerous bowlders, many of them six feet in diameter, and in one in- stance some of the blocks were found to be polished and striated, ~ and the underlying Vindhyan rocks were similarly marked. The authors also correlate these glacial phenomena with those found in similar deposits in South Africa, discovered and de- scribed by Mr. Stow. In the Olive group of the Salt range, described by the same authors, there is a curious resemblance between a certain con- glomerate ‘‘and that of the Talchir group of the Gondwana system.” This ‘‘ Olive conglomerate” belongs to the Creta- ceous series, and contains ice-transported erratic bowlders de- rived from unknown rocks, one of which, a red granite, ‘is polished and striated on three faces in so characteristic a man- ner that very little doubt can exist of its having been trans- ported by ice.” One block of red granite at the Mayo salt- mines of Khewra ‘‘is seven feet high and nineteen feet in cir- 486 THE ICH AGE IN NORTH AMERICA. cumference.” In the “transition beds” of the same authors, which are supposed to be of Upper Cretaceous age, there also are bowlder-beds with erratic blocks of great size. I know of no evidence of glacial phenomena in Eocene strata excepting the occurrence of huge masses of included gneiss in the strata known as Flysch in Switzerland. On this question, however, Swiss geologists are by no means agreed, and I attach little or no importance to it as affording evidence of glacier ice. Neither do I know of any Miocene glacier deposits except- ing those in the north of Italy, near Turin, described by the late eminent geologist, Gastaldi, and which I saw under his guidance. ‘These contained many large erratic bowlders de- rived from the distant Alps, which, in my opinion, were then at least as lofty as or even higher than they are now, especially if we consider the immense amount of denudation which they underwent during Miocene, later Tertiary, and post-Tertiary times. * ; In North America Professor Shaler would attribute the conglomerates. of Jurassic age in the valley of the Con- necticut, in a part of which lie the celebrated bird-tracks, to glacial origin.. This he infers, from the great thickness of the beds, the absence of life from the accompanying sand- stones, the subangular forms of many of the pebbles, and from the similarity in composition of the pebbles of that conglomerate with that-of those found in the modern drift — of the region.t' Upon this conclusion, however, it is proper to remark that the drift in the lower Connecticut Valley would, to a great extent, come from the same region, whether brought by ice or water, and the extent to which the pebbles would have been reduced to uniformity and smoothness by attrition depends upon the distance to which they have been rolled, or the length of time to which they have been sub- jected to wave-action. From what appears, the evidence is not clear that the fragments from which the pebbles are x ON ature,” vol. xxii, p. 389. + See “Illustrations of the Earth’s Surface: Glaciers,” by N. S. Shaler and W. M. Davis. Boston: James R. Osgood & Co., 1881, p. 95. THE CAUSE OF THE GLACIAL PERIOD. 487 made may not have originated in the near vicinity, and so their subangular condition need not imply glacial agency in transportation. Professor Shaler also is inclined to attribute the exten- sive conglomerate deposits of the Carboniferous age in the Appalachian district of North America to glacial action ; and certainly the extent of these conglomerate deposits un- derlying the coal-beds is surprising. “ In Pennsylvania they are about one thousand feet; in eastern Kentucky and east Tennessee their thickness rises to about two thousand feet.” Similar conglomerate deposits everywhere underlie the Car- boniferous system: According to Professor Shaler, ‘* we find it from southern France to Scotland, from Alabama to New Brunswick, in India, and elsewhere.” For the most part, however, the pebbles of this conglomerate consist of quartz or quartzite, well rounded, and seldom of larger size than can readily be transported by water ; though Professor Newberry is reported to have “found a bowlder of quartz- ite seventeen inches by twelve inches, imbedded in a seam of coal.” Altogether it seems more likely that we have in these conglomerates underlying the Appalachian coal-tields of America the wash brought down by large rivers heading in the mountain plateau toward the north and east, of which the Archean range on the Atlantic border, together with the hills of New England and the Adirondacks of New York, are but the remnants. That floating ice may have played some part in the streams coming down from these mountain-heighits is not improbable ; but it is doubtful whether the facts war- rant us in inferring anything more. Professor Shaler would also attribute a still lower series of conglomerates whose typical development is in eastern Tennessee and western North Carolina, and which rests un- conformably upon Laurentian rocks, to glacial action ; though he confesses that no scratched bowlders have yet been dis- covered in these deposits, but he writes: ‘‘ Recollecting that we know of no force that is competent to bring together such masses of pebbles derived from a wide-spread surface save 488 THE ICE AGE IN NORTH AMERICA. glacial action, we are justified in believing that this deposit is a product of ice-action, though the waste has evidently been worked over by water since its production.” The thickness of the deposits he estimates to be in some places nearly twenty thousand feet. These deposits correspond in age to the Roxbury conglomerates in Boston, which are about five hundred feet in thickness, and “are composed of materials derived from various points in eastern Massachusetts and southern New Hampshire. The pebbles are rarely over a foot in diameter.” But Professor Shaler thinks “ their frequently subangular forms and the wide range of sub- stances associated together make it pretty clear that they have a glacial origin.” Upon this the same remark is applicable which was made in a preceding section, namely, that along this whole Appala- chian border there were formerly Archean highlands of in- definite height, of which the stumps are all that now remain in the present hills and mountains. The erosion of these mountains on their western flanks has furnished the material of the vast sedimentary deposits of the eastern part of the Mississippi basin. For all we know, the material spread out over this area of sedimentary rocks was all within reach of rivers coming down from Archean heights, and so there is no necessity of supposing extensive glacial transportation from more northern water-sheds such as we are compelled to suppose in the glacial age of recent date. The same remark may be extended to all the evidence adduced in the preced- ing sections concerning a succession of glacial periods.* In all cases they are of such limited character that local glaciers coming down from isolated mountain-masses, such as now come down from the mountains of Alaska, Patagonia, and at no very distant date from those of New Zealand, are sufficient to account for the facts. Returning to the point under discussion, it is proper to remark that the conclusions here presented with reference to * See Lyell, “ Principles of Geology,” vol. i, pp. 293-210. THE CAUSE OF THE GLACIAL PERIOD. 489 Mr. Croll’s theory are those pretty generally adopted at the present time by the American gevlogists best qualified to in- terpret the facts. Thus, among the more eminent American geologists, Mr. G. K. Gilbert wrote, in 1883: It deals with a series of physical laws and physical condi- tions which interact upon each other in an exceedingly complex way—in so complex a way that meteorologists, who have to deal with only a portion of them, do not claim and scarcely hope for a complete analysis of their combinations. The op- portunities for arguing in a circle are most seductive, and the a priori probability that important considerations have been overlooked is not small. The only manner in which so comprehensive and intricate an hypothesis can be established is by stimulating inquiry which shall lead to corroborative evidence, and this is precisely what Croll’s hypothesis, after eight years of wide publicity, has failed todo. If it is true, then epochs of cold must have occurred with considerable frequency through the entire period repre- sented by the stratified rocks; and iceberg drift, if no other traces, should have been entombed at numerous horizons. It has not been found, however, and of the eight horizons claimed by Croll to show evidence of glacial action, the treatise under consideration [A. Geikie’s ‘‘ Text-Book of Geology” ] mentions only two with confidence, and two others with doubt. In the two instances to which queries are not attached, the phenomena appear to indicate local and not general glaciation. If the hypothesis is true, the cold of the Glacial epoch must have been many times interrupted by intervals of exceptional warmth, but little has been added to the evidence adduced by Croll for such an interruption, and in America, where there is now great activity in the investigation of glacial phenomena, the evidence of a single inter-glacial period is cumulative and overwhelming, while there is no indication whatever of more than one.* With this agrees the opinion of President Chamberlin : The various astronomical hypotheses seem to be the worse for increased knowledge of the distribution of the ancient ice- * “Nature,” vol. xxvii, p. 262. ) dl 490 THE ICE AGE IN NORTH AMERICA. sheet. I think I speak the growing conviction of active work- ers in the American field, that even the ingenious theory of Croll becomes increasingly unsatisfactory as the phenomena are developed into fuller appreciation. I think I may say this without prejudice, as one who, at a certain stage of study, was greatly drawn toward that fascinating hypothesis. But the more we know and ponder upon the enormous de- velopment of iceupon the plains of northeastern America, and contrast it with the relatively feeble development and disper- sion from the mountainous regions of Alaska, which now bear the greatest glaciers outside of the arctic regions, and the rela- tive absence of such accumulations in northeastern Asia—in short, the more we consider the asymmetry of the ice distri- bution in latitude and longitude, and its disparity in eleva- tion, the more difficult it becomes to explain the phenomena upon any astronomical basis, correlated though it be with oceanic and aérial currents and geographical features, by whatsoever of ingenuity.* Professor Le Conte remarks, in similar strain : Of the recurrence of many glacial epochs in the history of the earth there is as yet no reliable evidence, but much evidence to the contrary. It is true that what seem to be glacial drifts, with scored bowlders, etc., have been found on several geologi- cal horizons, but these are usually in the vicinity of lofty mountains, and are probably, therefore, evidence of local glacia- tion, not of a glacial epoch. On the other hand, all the evi- dence derived from fossils plainly indicates warm climates even in polar regions during all geological periods antil the Quater- nary. The evidence at present, therefore, is overwhelmingly in favor of the wniqueness of the Glacial epoch. This fact is the great objection to Croll’s theory. f All doubts, concerning the existence of carboniferous and cambrian glacial periods have, however, been removed by facts which have accumulated during the last twenty-five _ *“Proceedings of the American Association for the Advancement of Sci- ence,” vol. xxxv, p.211. + “Elements of Geology,” p. 577. THE CAUSE OF THE GLACIAL PERIOD. 491 years. It is now well ascertained that there have been several glacial periods but at irregular and widely separated intervals. The irregularity of the intervals would indicate that the cause cannot be the astronomical changes which Mr. Croll had adduced, for they occur at regular intervals. The facts as summarized by Professor Coleman are as follows:* (1) The Huronian rocks of Canada, which are the oldest sedimentary strata in existence, contain extensive conglom- erates in every area mapped in northern Canada through a region 1,000 miles long from east to west and 750 miles broad. Some of the bowlders in this conglomerate are tons in weight, while striated pebbles are as characteristic of glacial deposits as can be found in any other age. Sir Archibald Geikie had also noted similar deposits of archean age in Scotland. The deposits in Canada occur over hundreds of thousands of square miles. (2) In rocks of early cambrian age extensive conglom- erates such as would be formed from the petrification of glacial till are found in widely scattered regions, more specially of the southern hemisphere. From such deposits in China Mr. Baily Willis has recently brought back beautifully glaciated stones. But much larger areas in Australia and South Africa are covered with “‘tillite’’ of cambrian age. In ° South Australia Mr. Howchin has traced these deposits over an area extending 450 miles from north to south and 250 from east to west, with a thickness of 1,500 feet. In South Africa the cambrian tillite has been traced by Mr. Rogers over an area of 1,000 miles. In both regions the glaciated area lies near the 30th degree of latitude, andthemovement of bowlders has apparently been from south towards the north. Similar, but less clearly defined cambrian tillite has been reported at various places about Lake Superior. In Australia the ice *“‘Glacial Periods and Their Bearing on the Geological Theories,”’ “Bulletin of the Geological Society of America,’’ vol. xix, pp. 347-566. 492 THE ICE AGE IN NORTH AMERICA. movement evidently reached sea-level in regions which now have a warm temperate climate. There was a glacial epoch of great intensity at the close of the carboniferous period, which has been studied with much care in India, Australia, South Africa and South America. In India bowlder conglomerates or “‘tillite” occur at points which are from 700 to 800 miles apart, or if those reported from Afghanistan be included, extending from latitude 35° to 16°, a distance of 1,500 miles. In Australia this permo- carboniferous tillite has been traced ‘‘ widely in all the states of the Commonwealth, including the island of Tasmania to the south, with a range of latitude between 20° 30’ and 43°. Striated rock surfaces are often found under the old bowlder clay, the directions of the scorings indicating a motion of the ice in general from south to north, as might be expected; but in various places the ice-sheet or sheets reached the sea, large bowlders occurring in stratified shale, as if dropped from ice, and marine fossils being found in close connection with the beds containing bowlders.” The most remarkable glacial deposits of this age, however, or in some respects of any age, are found in South Africa, where fully 1,000,000 square miles are covered with tillite extending from 30° southeast for a distance of 800 miles. It is found in all the provinces “‘from the south of Cape Colony to the middle of the Transvaal or possibly the southern boun- dary of Rhodesia, and from Priesk, in Cape Colony, on the west to eastern Natal.’ The deposit is thin in the north, and thick in the south where, in Cape Colony, it reaches a thick- ness of 1,000 feet. No striated rock surfaces are found in the south, but they abound in the north. The deposits occur at elevations of from 3,000 to 6,000 feet above the sea, but along the southern margin the deposits were evidently laid down in water, whether salt or fresh has not been determined. The most surprising thing about these deposits in South Africa is that the transportation has been from the equator towards the ee ee ee eee A ee ee ce Si Atii aia ease UR Baca Sais UA ay Sas Berean Sear ae ht Fic. 129—Glaciated pebble, 7 inches long, from Fie. 130-Glaciated pebble, 11inches Lower Huronian, Cobalt, Can. (A. P. Colman.) long, from Dwyka, Matjesfontein, CapeColony. (A. P.Colman.) Fic. 131—Glaciated pleistocene surface from Lower Huronian tillite near Thessalon, Ont. (A. P. Colman.) 494 THE ICE AGE IN NORTH AMERICA. south pole. This was indicated by the fact just mentioned that they increased in thickness from north to south, as they do in the pleistocene glacial deposits of North America, though on different sides of the equator. But more decisive evidence appears in the direction of the scratches on the under- lying rock, which is from northwest to southeast; and from the bowlders which have all been transported in the same direction. In. India also the ice movement of the permo-carbonif- erous period was from the equator northward, toward the pole, in some cases bowlders having been transported 750 miles in that direction. Other indications of a permo-carboniferous period have been reported by Karpinsky and Tchernyschev in the Ural Mountains, and by Ramsay in England, but no one has discovered clear evidences of such deposits in America. With reference to these deposits it is significantly remarked by Professor Coleman that ‘‘as in the pleistocene, there seems to have been an impressive grouping of the great ice-sheets in a special quarter, this time in the neighborhood of the present Indian Ocean; and their nearness to the equator, on low ground and reaching to the sea, makes it all the more puzzling that so little evidence of glacial work should be found in higher latitudes.”’ CHAPTER XIX. THE CAUSE OF THE GLACIAL PERIOD—CONTINUED. The eighth theory, which would attribute the growth and disappearance of glaciers entirely to changes in the distribu- © tion of land and water over the surface of the globe, was, according to his general principles, abiy and ardently advo- cated by Sir Charles Lyell; and no one can read in his “Principles of Geology” the chapters upon this subject without being greatly impressed by the possible influences of such changes. The ocean is the great equalizer of the earth’s temperature. Through unimpeded ocean-currents, like the Gulf Stream of the Altantic and the Kuro-Siwa cf the Pacific, the heat of the tropics is transferred many thousands of miles to ameliorate the climate of even the polar regions. It is quite possible that comparatively slight changes in level in the vicinity of the West India Islands and Central America might so affect the direction of the Gulf Stream as to produce most serious modifications of the climate in North America and Europe. Should a portion of the Gulf Stream be driven through a depression across the Isthmus of Panama into the Pacific, and an equal portion be diverted from the Atlantic coast of the United States by an elevation of the sea-bottom between Florida and Cuba, the consequences would neces- sarily be incalculably great, so that the mere existence ofsuch a possible cause for great changes in the distribution of moist- ure over the northern hemisphere is sufficient to make one hesitate before committing himself unreservedly to any other theory—at any rate, to one which has not for itself indepen- dent and adequate proof. 496 THE ICE AGE IN NORTH AMERICA. It is profitable, also, in this connection, to reflect on how delicately balanced the forces of Nature now are with respect to the production of glaciers. As already noted,* the gla- ciers existing at the present time in the Alps have their peri- ods of advance and recession. A slight increase in the present snow-fall of Switzerland, if long continued, would produce alarming results. From this cause alone, the glaciers would at once begin to enlarge; and, in sympathy, the temperature would fall, and the increase of the glaciated area of Switzerland would go on until the whole country was again brought under the desolating reign of ice, or until the intervention of some counteracting force should stay its advance. It is not without reason, therefore, that some alarm was occasioned in Switzerland a few years ago by the. proposition to inundate the Desert of Sahara. Fortunately, no extensive inundation of that region is within the reach of human power. But, if it could be inundated, thus extend- ing greatly the evaporating area from which the clouds gather moisture for the Alpine heights, there is no telling what the result might not be. Should there be an annual increase of a foot of snow upon the Alps, a thousand addi- tional feet of snow would have to be dissolved every thou- sand years, with the enormous absorption of heat accom- panying the process. This simple calculation is sufficient to show the reality of the cause introduced by the eighth hy- pothesis, which would explain the Glacial period through the influence upon climate of changes in the distribution of land and water. ‘This cause is so effective that it may even be conceived to be sufficient, without the introduction of any other agencies. He The ninth theory, which introduces considerable change of levels .n the continents, rests, without doubt, upon a true cause, which, very likely, has coéperated with others, and may in itself have been the chief agency in producing the glacial conditions which we are studying. ‘The evidence in support of this theory was so well presented by Dr. Warren *See pagel05. THE CAUSE OF THE GLACIAL PERIOD. 497 Upham, in the appendix to the original edition of this volume and his conclusions have been supported by so many lines of evidence which have since come to light, that we now insert it in the body of the discussion with such supplementary notes as he has thought it necessary to add. It is a signifi- cant confirmation of his views that Professor Chamberlin’s theory of the effect of the diminution of the carbonic dioxide in the atmosphere in producing glacial conditions involves extensive continental elevation of land surfaces as prelimi- nary to the supposed depletion of this important element. An examination of the evidence of changes in the relative heights of land and sea in various parts of the world during Quaternary time has led me to an explanation of the causes of theGlacial period, which, in this applicationof its fundamental principle, seems to be new, while in its secondary elements it combines many of the features of the explanations proposed by Lyell and Dana and by Croll. Briefly stated, the condi- tion and relation of the earth’s crust and interior appear to be such that they produce, in connection with contraction of the earth’s mass, depressions and uplifts of extensive areas, some of which have been raised to heights where their precipita- tion of moisture throughout the year was almost wholly snow, gradually forming thick ice-sheets; but under the heavy load of ice subsidence ensued, with correlative uplift of other portions of the earth’s crust; so that glacial conditions may have prevailed alternately in the northern and southern hemis- pheres, or in North America and Europe, and may have been repeated after warm interglacial epochs. Quaternary oscillations of land and sea in glaciated regions have been discussed by Croll and Geikie on the assumption that the earth was so rigid that its form would not be changed ‘by the load of the ice-sheet nor by its removal, which seemed more probable because of the well-known physical and mathe- matical researches of Hopkins, Thomson, Pratt, and Professor G. H. Darwin. who conclude that the earth is probably solid, 498 THE ICE AGE IN NORTH AMERICA, with not less rigidity than that of glass or steel. In def- erence to their researches, this conclusion is accepted and taught in recent text-books of geology by Le Conte and A. Geikie ; but in similarly recent text-books Dana and Prestwich teach that the earth probably consists of a comparatively thin crust underlaid by a molten interior, which may change within a moderate depth to a great nucleal solid mass. Among other geologists and physicists who have discussed the condition of the earth’s interior, King * and Shaler ¢ believe it to be solid ; while Whitney,f Dutton,* Powell, || Wadsworth,“ Crosby, } Gilbert,{ Claypole, } Airy, t Fisher,** and Jamieson, tt believe that it is molten, or, at least, is surrounded by a molten layer, and that the earth’s crust floats in a condition of hydrostatic equilibrium upon the heavier liquid or viscous mobile interior or layer enveloping the interior, subject, however, to strains and resulting deformation because of the earth’s contraction. The thickness of the crust, according to this hypothesis, is variously estimated to be from twenty to fifty miles, or posnieny a hundred miles or more. It must be confessed that we have only a very inadequate knowledge of the conditions which would result from the enor- * “United States Geological Exploration of the Fortieth Parallel,” vol. i, “Systematic Geology,” 1878, pp. 117, 696-725. ._t “ Proceedings of the Boston Society of Natural History,” 1866, vol. xi, pp. 8-15; 1868, vol. xii, pp. 128-136; 1874, vol. xvii, pp. 288-292. ‘Memoirs of the Boston Society of Natural History,” 1874, vol. ii, pp. 320-340. “ Seribner’s Magazine,” vol. iii, pp. 201-226, February, 1888. } “‘ Earthquakes, Volcanoes, and Mountain Building,” 1871, pp. 77-87. # “Penn Monthly,” vol. vii, pp. 364-378, and 417-431, May and June, 1876. “ United States Geological Survey, Fourth Annual Report, ” pp. 183-198 ; “Sixth Annual Report,” pp. 195-198. || “Science,” vol. iii, pp. 480-482, April 18, 1884. A “ American Naturalist,” vol. xviii, June, July, and August, 1884. ) “Proceedings of the Boston Society of Natural History,” 1883, vol. xxii, pp. 443-485. ‘Geological Magazine,” II, vol. x, 1883, pp. 241-252. } “ American Journal of Science,” III, vol. xxxi, pp. 284-299, April, 1886. $ “ American Naturalist,” vol. xix, pp. 257-268, March, 1885. “ American Geologist,” vol. i, pp. 382-386, and vol. ii, pp. 28-35, June and July, 1888. 4 “Nature,” vol. xviii, pp. 41-44, May 9, 1878. ** “ Physics of the Earth’s Crust,” 1881, pp. 223, 270, ete. ++ ‘“ Geological Magazine,” III, vol. iv, 1887, pp. 344-348, THE CAUSE OF THE GLACIAL PERIOD. 499 mous pressure and high temperature of the earth’s interior, and wide diversity in speculations on this subject will probably long continue. Professor Shaler, while holding that the earth is mainly solid throughout, perhaps having in its most mobile layer beneath the crust ‘‘a rigidity such as belongs to the metals of average resistance to compression,” yet is one of the earliest and most decided advocates of the opinion that the weight of an ice-sheet may depress the area on which it lies, and that the departure of the ice would be attended by re- elevation. In comparison, however, with the physical condi- tions and laws familiar to us upon the earth’s surface, the subsidence and elevation of extensive areas, as of nearly all glaciated regions, seem to demonstrate a mobility of the earth’s interior as if it were fused rock. The same conclusion is in- dicated by volcanoes, which are probably the openings of molt- en passages that communicate downward through the crust to the heavier melted interior, thence deriving their supply of heat, while their outpoured lavas consist largely or wholly of fused portions of the crust, the phenomena of eruption being caused by the access of water to the upper part of the molten rock near the volcanic vent. But the great plications of the strata in the formation of mountain-chains evidently involve only the upper part of the earth’s crust, crumpled into smaller area in adapting itself to the diminishing volume of the lower portion of the same crust, which, with the nucleus, is under- going contraction on account of the gradual loss of its heat, and perhaps also on account of progressing solidification and compression. There is in this process no dependence on the molten condition of the interior, except as that seems to be necessary for distortion of the earth, both of the crust and nucleus or mobile layer enveloping the nucleus, whereby con- siderable shrinkage of volume can take place before the ac- cumulated strain becomes sufficient for the formation of a mountain-chain. At the present time depressions and eleva- tions, probably caused by accumulating strains, are slowly changing the relations of land and sea upon many parts of the earth’s surface. In the same way the downward and upward movements which would be caused by the burden of the ice- sheet and its removal are doubtless in many places complicated 500 THE ICE AGE IN NORTH AMERICA, by concomitant or subsequent movements thus due to defor- mations under strains, by which the elevation attributable to the departure of the ice-sheet may be augmented or partly or wholly counteracted, giving much irregularity to the glacial and post-glacial oscillations of the land. Jamieson appears to have been the first, in 1865, to suggest this view, which I receive from him, that the submergence of glaciated lands when they were loaded with ice has been caused directly by this load pressing down the earth’s crust upon its fused interior, and that the subsequent re-elevation was a hydrostatic uplifting of the crust by underflow of the inner mass when the ice was melted away.* Two years later Whit- tlesey published a similar opinion.+{ In 1868 Shaler referred the subsidence of ice-covered areas to a supposed rise of iso- geothermal lines in the subjacent crust, operating, in conjunc- tion with the ice-sheet, to produce downward flexure ;{ but in 1874 and later he regards the depression as due directly to the weight of the ice, and the re-elevation as due to its removal. * The same view is advanced also by Chamberlin to account for the basins of the Laurentian lakes, where he believes a con- siderable part of the glacial depression to have been permanent. | * “Quarterly Journal of the Geological Society,” vol. xxi, p. 178. Later discussions of this subject by Mr. Jamieson are in the ‘‘ Geological Magazine,” II, vol. ix, pp. 400-407 and 457-466, September and October, 1882; and III, vol. iv, pp. 344-348, August, 1887. In the article last cited, he applies this ex- planation to the changes of the beaches of Lake Agassiz, which up to that time I had attributed mainly to ice attraction. The same principle, however, was brought forward by Herschel in 1836, and had been advocated by Professor James Hall, of New York, in 1859, in attributing to the weight of sediments the long continued subsidence of the areas on which they have been deposited in great thickness. --+ “Proceedings of the American Association for the Advancement of Science,” vol. xvi, pp. 92-97. _ “ Proceedings of the Boston Society of Natural History,” vol. xii, pp. 128--136. * “ Proceedings of the Boston Society of Natural History,” vol. xvii, pp. 288-292; “Memoirs,” ibid., vol. ii, pp. 335-340; ‘American Journal of Science,” III, vol. xxxiii, pp. 220, 221, March, 1887; “ Scribner’s Magazine,” vol. i, p. 259, March, 1887. -. || “ Geology of Wisconsin,” vol. i, 1888, p. 290; “ Proceedings of the Ameri- can Association for the Advancement of Science,” vol. xxxii, 1883, p. 212. The Ba Met eee ti Shc aua ea at ‘ a THE CAUSE OF THE GLACIAL PERIOD. O01 Accompanying the subsidence of ice-loaded areas, there were doubtless uplifts of contiguous regions, perhaps sometimes 1n- cluding outer portions of the country glaciated. For example, the Quatenary elevation of which Le Conte finds evidence in the Sierra Nevada and northward may have been contempora- neous and correlative with depression of the northern parts of the continent beneath its ice-sheet. Furthermore, instead of being wholly offset by deformation of the crust, the glacial depression may have produced also extensive extravasation of lava, as is suggested by Jamieson * and Alexander Winchell, + for the vast Quaternary lava-flows of California, Oregon, Wash- ington, and a large adjacent region. As Jamieson well re- marks, this result would tend to cause a permanence of part of the depression of the ice-covered area. However it may have been caused, probably such permanent Quaternary subsidence is true for the coasts of many glaciated countries, as shown by * fiords, and for the basins of the Laurentian lakes, which, ex- cepting Erie, are depressed several hundred feet below the level of the ocean. One of the most interesting fiords of North America is that of the Saguenay, tributary to the St. Lawrence. Along a distance of about fifty miles the Saguenay is from 300 to 840 _ feet deep below the sea-level ; its adjoining cliffs rise abruptly in some places 1,500 feet above the water ; and the width of its wonderfully sublime and picturesque gorge varies from about a mile to one mile and a half.{ This fiord, like the many ‘which indent our Eastern coast from Maine to Labrador and Greenland, and our Western coast from Puget Sound to the Arctic Ocean, was eroded by a stream that flowed along the bottom of the gorge when it was above the sea ; and this erosion was probably going forward in the epoch immediately preced- problems of ice attraction and of deformation of the earth’s crust have been further discussed by President Chamberlin before the Philosophical Society of Washington, March 13, 1886; and, jointly with Professor Salisbury, in the “Sixth Annual Report, United States Geological Survey,” pp. 291-304. * “ Geological Magazine,” IT, vol. ix, 1882, p. 405. + “ American Geologist,” vol. i, pp. 139-143, March, 1888. ¢ “J. W. Dawson, “ Notes on the Post-Pliocene Geology of Canada,” 1872, p. 41. 502 THE ICH AGE IN NORTH AMERICA. ing the Ice age, for earlier subsidence during any period of much length, geologically speaking, would have caused the submerged valley to be filled with sediments. The preglacial elevation of the Saguenay region therefore appears to have been at least 1,000 feet greater than now; and it seems to be similarly proved by fiords that nearly the entire extent of the conti- nental glaciated area was considerably higher before than after glaciation. There is also evidence that part of the Atlantic coast of the United States close south of the limits of glaciation was at least for a. short time preceding the Glacial period uplifted much above its present height. The submarine Hudson River fiord * indicates that the vicinity of New York and Philadelphia then stood 2,800 feet above the sea, and that it afterward slowly sank 1,600 feet, while a bar of that height was formed by coast- wise wash across the mouth of the fiord. In this remarkable preglacial elevation, and in its being more or less shared by the whole northern half of the continent, the formation of the North American ice-sheet seems to be explained. If this was the cause of glaciation, probably the formerly greater height of about 1,000 feet on the Saguenay was not exceptional. In- deed, the elevation there and over large portions of the vast territory of Canada, bounded on the east, north, and west by fiord-indented: coasts, may have been much more than is measured by the depth of the Saguenay River. Going a step further back, we may regard this northward elevation as a distortion of the earth’s form in the storage of energy of lateral pressure which culminated, with the introduc- tion of the new factor of northward depression by the ice weight, in the Quaternary uplifts of the Western plains, the Rocky Mountains, the Sierra Nevada, and the Great Basin. These important changes in the elevations of great areas during the comparatively short Quaternary period seem to be consistent only with the hypothesis that our globe has a comparatively thin crust and a molten interior. In the Glacial period significant changes of the sea-level * A. Lindenkohl, “‘ American Journal of Science,” III, vol. xxix, pp. 475-480, with plate, June, 1885. THE CAUSE OF THE GLACIAL PERIOD. 503 were caused : first, by abstraction of water from the ocean and its deposition on the land as snow, which under pressure made the vast ice-sheets ; and, second, by ice attraction of the ocean, _ lowering it still further, except in the vicinity of glaciated lands. An area of about 4,000,000 square miles in North ‘America, and another of about 2,000,000 square miles in Europe, were covered by ice-sheets, which in their maximum: extent had probably an average thickness of a half or two thirds: of a mile, or perhaps even of one mile. Assuming that these ice-sheets were contemporaneous, but disregarding ice-fields of smaller extent, which probably existed in parts of Asia and of the southern hemisphere, as also the glaciers of mountain dis- tricts, the lowering of the ocean surface, which covers approxi- mately 145,000,000 square miles, would slightly exceed 100 feet, if the mean depth of the ice accumulation was half a mile. More probably the sea over the whole globe was thus depressed fully 150 feet, which would correspond to an average of about 3,600 feet of ice on the glaciated areas of North America and Europe. For the second factor in causing such changes, Mr. R. S. Woodward’s computations* indicate that gravitation toward the ice would further depress the ocean probably twenty-five to seventy-five feet within the tropics and in the southern hemisphere, while it would raise the level enough near the borders of the ice-sheets to counterbalance approxi- mately the depression due to the diminution of the ocean’s volume, and would lift portions of the North Atlantic and of the Arctic Sea perhaps two or three hundred feet higher than now. Stream erosion while the sea was lowered to supply the ice of the Glacial period may explain the indentations of the southeastern coast of the United States, as Pamlico and Albe- marle Sounds, besides similar inlets in many other parts of the world ; but the excavation of Chesapeake and Delaware Bays seems more probably referable, at least in part, to the time of preglacial elevation, with the channeling of the now sub- merged Hudson fiord. When the ice-sheet of the last Glacial doa finally re- *“ United States Geological Survey, Sixth Annual Report,” pp. 291-300; and “ Bulletin No. 48,” ‘‘ On the Form and Position of the Sea-Level.” 504 THE ICE AGE IN NORTH AMERICA. treated, the land which it had covered stood mostly lower than now, as is shown by the occurrence of fossiliferous marine deposits overlying the glacial drift up to considerable eleva- tions. Near Boston, and northeast to Cape Ann, the coast — seems to have been submerged to a slight depth, probably not exceeding ten to twenty-five feet. Proceeding toward the north and northwest, the elevation of the marine beds lying on the glacial drift increases to about two hundred and twenty- five feet in Maine, about five hundred and twenty feet in the St. Lawrence Valley at Montreal, and four hundred and forty feet at a distance of one hundred and thirty miles west-south- west of Montreal; but eastward, along the St. Lawrence, it decreases to three hundred and seventy-five feet opposite the Saguenay, and does not exceed two hundred feet in the basin of the Bay of Chaleurs ; while these marine deposits are want- ing in Nova Scotia and Cape Breton Island.* This subsidence accords well with the explanation that it was due to the press- ure of the ice- weight, which was greatest on the highlands between the St. Lawrence and Hudson Bay. Along the East Main coast of Hudson Bay and on Hudson Strait raised beaches are conspicuous, according to Dr. Robert Bell, up to heights of at least three hundred feet.t In the region draining from the southwest to James Bay, Dr. Bell reports marine shells in stratified beds overlying the glacial drift along the Moose, Mattagami, and Missinaibi Rivers up to about three hundred feet above the sea; { along the Albany * A. S. Packard, Jr., ‘Memoirs of the Boston Society of Natural History,” vol. i, pp. 231-262. J. W. Dawson, “Notes on the Post-Pliocene Geology of Canada” ; and “‘ American Journal of Science,” TI, vol. xxv, 1888, pp. 200-202, C. H. Hitchcock, “‘ Proceedings of American Association for the Advancement of Science,” Portland, 1873, vol. xxii, pp. 169-175; “Geology of New Hamp- shire,” vol. iii, pp. 279-282; and ‘‘ Geological Magazine,” II, vol. vi, 1879, pp. 248-250. R. Chalmers, “Transactions of the Royal Society of Canada,” sec. iv, 1886, pp. 1389-145. W. Upham, “ Proceedings of Boston Society of Natural History,” vol. xxiv, pp. 127-141, December, 1888; ‘“‘ American Journal of Sci- ence,” May, 1889. + ‘Geological and Natural History Survey of Canada, Report of Progress for 1877-78,” p. 832 C; for 1882-83-84, p. 31 DD. t “Geological and Natural History Survey of Canada, Report of Progress for 1875-"76,” p. 340; for 1877-78, p. 7 C, THE CAUSE OF THE GLACIAL PERIOD. 905 and Kenogami Rivers up to a height of about four hundred and fifty feet ;* and on the Attawapishkat to about five hundred feet above the sea.+ It is also evident that the shores of Hud- son Bay are still undergoing elevation,{ unlike the eastern coast of the United States and Canada, where the post-glacial uplift- ing has ceased, and there is now in progress a very slow sub- sidence of the land from New Jersey to the Gulf of St. Law- rence. Scantier but yet conclusive proofs of the uplift of British Columbia after glaciation are found in the valley of the Fraser River, and on the Pacific coast, in Vancouver Island and the Queen Charlotte Islands. Lamplugh has observed recent ma- rine shells in a railway cutting on the west bank of the Harri- son River, near its junction with the Fraser, at an elevation not less than one hundred feet above the sea.* At New West- minster, on the Fraser, near its mouth, raised beaches inclos- ing fragments of marine shells are reported by Bauerman about thirty feet above the river.|| Fossiliferous marine deposits found in the vicinity of Victoria and Nanaimo, in the south- east part of Vancouver Island, at small elevations above the sea, are believed by Dr. G. M. Dawson to have been formed at or near the wasting edge of the ice-sheet ;* and near the mid- dle of the northeast side of this island two distinct deposits of till occur, with mtervening beds of loess-like silts, from which * “ Geological and Natural History Survey of Canada, Report of Progress for 1871-72,” p. 112; for 1875-76, p. 340; “Annual Report,” vol. ii, for 1886, pp. 34 and 38 G. + “Geological and Natural History Survey of Canada, Annual Report,” vol. i, p. 27 G. t ‘‘Geological and Natural History Survey of Canada, Report of Progress for 1877-’78,” pp. 32 C and 25 CC; for 1878-79, p. 21 C; for 1882—’83-’84, pp. 26 and 30 DD; “ Annual Report,” vol. i, for 1885, p. 11 DD. * “ Quarterly Journal of the Geological Society,” vol. xlii, 1886, pp. 284, 285. | “Geological and Natural History Survey of Canada, Report of Progress for 1882-—’83-’84,” p. 33 B. A “ Geological and Natural History Survey of Canada, Annual Report,” voi. ii, for 1886, p. 99 B; “Quarterly Journal of Geological Society,” vol. xxxiv, 1878, pp. 97, 98, and vol. xxxvii, 1881, p. 279. Compare also Mr. G. W. Lamp- lugh’s observations of glacial shell-beds at Esquimault, near Victoria, “ Quar- terly Journal of Geological Society,” vol. xlii, 1886, pp. 276-284 506 THE ICE AGE IN NORTH AMERICA. this author infers two periods of glaciation, separated by an interglacial epoch, in which the land was submerged from one to: two hundred feet.* Again, in the northeast part of the Queen Charlotte Islands Dr. Dawson finds evidence of sub- mergence to the amount of two or three hundred feet, while the glacial conditions still endured. + In Europe the glaciated area stood at a greater height be fore the Ice age, as is shown by fiords; it was similarly de- pressed while loaded with the ice-sheet ; and since then it has been partially re-elevated. Its maximum post-glacial uplift known in the British Isles, so far as it has not been counter- acted by subsequent depression, is five hundred and ten feet, near Airdrie, in Lanarkshire, Scotland;{ and in Scandinavia it is about six hundred feet.# As in all the North American districts noted, these upward movements seem attributable to the rise of the earth’s crust, upborne by inflow of a molten magma beneath. But the derivation of the floras of the Firée Islands, Ice- land, and even Greenland from the flora of Europe, demon- strates, according to Professor James Geikie, that the portion of the earth’s crust extending from Britain and Scandinavia to Greenland was uplifted in early post-glacial times about * “ Geological and Natural History Survey of Canada, Annual Report,” vol. ii, p. 105 B. + “‘ Geological and Natural History Survey of Canada, Report of Progress for 1878-79,” p. 95 B. Further important notes of recent changes in level of .the coast of British Columbia, and of Washington Territory and Alaska, are given by Dr. Dawson in the “Canadian Naturalist,” new series, vol. viii, pp. 241 —248, April, 1877. He concludes that this area had a preglacial elevation at least about nine hundred feet above the present sea-level, during part or the whole of the Pliocene period, this being indicated by the fiords; that it was much depressed in the Glacial period; and that in post-glacial time it has been re-elevated to a height probably two or three hundred feet greater than now, followed by subsidence to the present level, the latest part of this oscillation being a somewhat rapid depression of perhaps ten or fifteen feet during the latter part of last century—a movement which may still be slowly going on. t ‘Quarterly Journal of the Geological Society,” vol. vi, 1850, pp. 386-388, and vol. xxi, 1865, pp. 219-221; “ American Geologist,” vol. ii, pp. 371-379, December, 1888. # “Geological Magazine,” I, vol. ix, 1872, p. 309; and II, vol. ii, 1875, p. 390. , : : | THE CAUSE OF THE GLACIAL PERIOD. 507 three thousand feet higher than now ;* and the same author shows that nm interglacial time tropical animals passed from Barbary into Spain upon land where now the Strait of Gi- braltar has a depth of one thousand feet.t These changes in the relations of land and sea can not be ascribed to glacia- tion, but seem to be distortions of the earth’s form, such as may be attributed to the action of strain upon the crust by which the earth can become reduced in volume through the subsidence and elevation of extensive areas during intervals between epochs of mountain-building. In the same class of changes are also to be included, wholly or in part, the post- glacial elevation of Grinnell Land and the northwestern coast of Greenland, one thousand to sixteen hundred feet ; { post- Pliocene upward movements of two thousand feet or more in Jamaica and Cuba ;* the recent uplift of the coast of Peru at least twenty-nine hundred feet,|| which in diminished amount seems to extend along the whole range of the Andes ; its prob- able connection with the upheaval of the Cordilleras of North America, where Le Conte believes that the elevatory move- ments reached their greatest intensity in early Quaternary time, causing a rise of several thousands of feet in the Sierra Nevada ;“ and the apparently correlative subsidence of a great * “ Prehistoric Europe,” pp. 513-522, and 568, with Plate E. + “ Prehistoric Europe,” pp. 325, 337-339 ; ‘‘ Quarterly Journal of the Geo- logical Society,” vol. xxxiv, 1878, p. 505. ¢ “ Quarterly Journal of Geological Society,” vol. xxxiv, 1878, p. 66; “ Geo- logical Magazine,” ITI, vol. i, 1884, p. 522. * J. G. Sawkins, “Reports on the Geology of Jamaica,” 1869, pp. 22, 23, 307, 311, 324-329; W. O. Crosby, “On the Mountains of Eastern Cuba,” “ Ap- palachia,” vol. iii, pp. 129-142. Compare William M. Gabb’s memoir, ‘‘ On the Topography and Geology of Santo Domingo,” “Transactions of the American Philosophical Society,” vol. xv, pp. 103-111. | || A. Agassiz, “ Proceedings of the American Academy of,Arts and Sciences,” vol. xi, 1876, p. 287; and “Bulletin of the Museum of Comparative Zodlogy, at Harvard College,” vol. iii, pp. 287-290. Above this height, at which corals are found attached to rocks, recent elevation of much greater amount seems to be indicated by terraces, by saline deposits, and by the presence of eight species of Allorchestes—a genus of marine crustacea, in Lake Titicaca, 12,500 feet above the sea. 4“ American Journal of Science,” III, vol. xxxii, pp. 167-181, September, 1886. 508 THE ICH AGE IN NORTH AMERICA. area dotted with coral islands in the Pacific. The Quaternary uplifts of the Andes and Rocky Mountains and of the West Indies make it nearly certain that the Isthmus of Panama has been similarly elevated during the recent epoch. On the line of the Panama Railway the highest land rises only two hundred and ninety-nine feet above the sea, and the highest on the Nicaragua Canal is about one hundred and thirty-three feet, while the isthmus nowhere attains the height of one thousand feet.* It may be true, therefore, that the submergence of this isthmus was one of the causes of the Glacial period, the con- tinuation of the equatorial oceanic current westward into the Pacific having greatly diminished or wholly diverted the Gulf Stream, which carries warmth from the tropics to the northern Atlantic and northwestern Europe. In view of the extensive recent oscillations of land and sea both in glaciated and unglaciated regions, it seems a rea- sonable conclusion that, while some of these movements have resulted directly from the accumulation and dissolution of ice- sheets, more generally, when the whole area of the earth 1s considered, they have been independent of glaciation. May not such movements of the earth’s crust, then, have elevated large portions of continents, as the northern half of North America and the northwestern part of Europe, to heights like those of the present snow-line on mountain-ranges, until these plateaus became deeply channeled by fiords and afterward coy- ered by ice-sheets ? For the recentness of the latest glaciation, believed to have ended in the northern United States not more than ten thousand to six thousand years ago,t forbids our re- a — = * Charles Ricketts, ‘‘The Cause of the Glacial Period, with reference to the British Isles,” “Geological Magazine,” II, vol. ii, 1875, pp. 573-580. A. R. Wallace, “The Geographical Distribution of Animals,” vol. i, p. 40. + N. H. Winghell, “Geology of Minnesota,” “Fifth Annual Report,” for 1876, and “Final Report,” vol. ii, pp. 818-341; “Quarterly Journal of the Geological Society,” vol. xxxiv, 1878, pp. 886-901. E. Andrews, “ Transactions of the Chicago Academy of Sciences,” vol. ii. James C. Southall, ““The Epoch of the Mammoth and the Apparition of Man upon the Earth,” 1878, chaps. xxii and xxiii. G. F. Wright, ‘“‘ American Journal of Science,” III, vol. xxi, pp. 120- 123, February, 1881; “The Ice Age in North America,” chap. xx. G. K. Gil- bert, “Proceedings of the American Association for the Advancement of Sci- ence,” vol. xxxv, 1886. q ¥ f ‘ ' THE CAUSE OF THE GLACIAL PERIOD. 509 ferring the glacial climate to conditions brought about by a period of increased eccentricity of the earth’s orbit from two hundred and forty thousand to eighty thousand years ago, which has been so ably maintained by Croll and Geikie; and some other adequate cause or causes must be sought for the successive Quaternary glacial epochs of these great continental areas and other districts of smaller extent both in the northern and southern hemispheres ; also for the rare occurrence of gla- cial conditions in various portions of the earth during past geologic ages, especially in the Carboniferous and Permian periods. The principal cause of all these epochs of glaciation seems to the writer to be probably found by the clew supplied in the relations already stated of the earth’s crust and interior, whereby they become somewhat distorted from the spheroidal form while the process of contraction goes forward, the lateral pressure bearing down some portions of the earth’s surface, and uplifting other extensive areas. Protuberant plateaus, swept over by moisture-laden winds, would be the gathering- grounds of vast ice-sheets, which would probably wax and wane with the changes of the earth’s attitude toward the sun, by which the earth’s place in any season, as summer, alternates from aphelion to perihelion, and back to aphelion in cycles of twenty-one thousand years. A similar explanation of the Gla- cial period was long ago proposed by Lyell and Dana, but without referring the elevatory movements to the earth’s de- formation by contraction and accumulating lateral pressure while approaching an epoch of mountain-building, which fundamental principle was first suggested to me in an article from the pen of Professor W. O. Crosby, on the origin and relations of continents and ocean basins.* During the periods immediately preceding great plications and shortening of segments of the earth’s crust involved in the formation of lofty mountain-ranges, the broad crustal move- ments causing glaciation would be most wide-spread and attain their maximum vertical extent. The accumulation of ice- sheets may have brought about the depression of their areas, * “Proceedings of the Boston Society of Natural History,” 1883, vol. xxii, pp. 455-460. 510 THE ICE AGE IN NORTH AMERICA. with corresponding elevation of other plateaus, which in turn would become ice-covered, so that the epochs of glaciation of © the northern and southern hemispheres may have alternated with each other ;* and this may have been several times re- peated, because of crustal oscillations due to ice-weight and its removal, the effects of elevation and depression of the land — being re-enforced by climatic influences arising from the revolu- tion each twenty-one thousand years in the place of the seasons. When the building up of a great range of mountains ensued, which may have been initiated and accelerated by the repeated | depressions under ice-weight and consequent transfers of the earth’s deformation from one region to another, the accumu- lated strain in the earth’s crust, with development of immense lateral pressure, would be diminished below the limit of its competency to cause glaciation. Such Quaternary mountain-building is known to have oc- curred on a most massive scale in Asia, where the Himalayas, stretching fifteen hundred miles from east to west, and tower- ing twenty thousand to twenty-nine thousand feet above the sea, are known to have been formed, at least in great part, and perhaps almost wholly, during this latest geologic period,f contemporaneously with the glaciation of North America, Kurope, and portions of the southern hemisphere. Within the same time the great table-land of Thibet,{ and much of central and. northwestern Asia, have been uplifted ; the tract extend- ing from the Black and Caspian Seas northeast to the Arctic Ocean has risen to form a land-surface ; and the deep basin of Lake Baikal has been probably formed in connection with these crustal movements. Accompanying the formation of the Himalayas, there has been doubtless much disturbance by faults, local uplifts, and here and there plication of strata * Compare the opinions of Hutton, cited in A. Geikie’s “ Text-Book of Geolo- gy,” second edition, p. 912, that the former greater extension of glaciers in New Zealand was caused by an increase in the elevation of the land, and that it be- longed to a much earlier time than the Ice age in the northern hemisphere, probably to the Pliocene period. + “Manual of the Geology of India,” by H. B. Medlicott and W. T. Blanford, Calcutta, 1879, Part I, pp. lvi, 372; Part II, pp. 569-571, 667-669, 672-681. t Ibid., Part II, pp. 585, 586, 669-672. THE CAUSE OF THE GLACIAL PERIOD. oll along the whole complex east to northwest and west mountain system of Oceania, Asia, Europe, and Northern Africa, from ‘New Guinea, the Sunda Islands, Anam, and Siam, to the Can- casus, Carpathians, Balkans, Apennines, Alps, Pyrenees, and Atlas Mountains, stretching quite across the eastern hemi- sphere ; but the greater part of the relief from the previously existing deformation of the earth was doubtless along the cen- tral part of the belt, in the colossal Himalayan range. In like manner the North American Cordilleras and the Andes, reaching in one continuous mountain system from the Arctic Circle to Cape Horn, have experienced within the same period great disturbances, as already noted, similar to those of the mountains of Southern Europe and the adjacent part of Africa. ‘With this American orographic belt is also probably to be associated the mountain system, consisting largely of volcanoes ‘now active, which forms the Aleutian Islands, Kamtchatka, -the Kurile Islands, Japan, Formosa, the Philippines, Borneo, and Celebes, lying nearly in the same great circle with the Andes and Rocky Mountains, and with them continuous in an arc of about two hundred and forty degrees. Along two lines transverse to each other, one having an extent of half and the other of two thirds of the earth’s circumference, the great lateral pressures of the earth’s crust, which probably caused the elevation and glaciation of extensive areas during the Quaternary period, have been relieved by plication, faults, and uplifts, in the processes of the formation of mountain- ranges. * Combined with oscillations of the earth’s crust, which are here regarded as the primary cause of the growth and decline of ice-sheets, many other concomitant conditions, notably changes in aérial and oceanic currents, and the earth’s cycles of twenty-one thousand years through precession and nutation, enter into the complex causation of recurrent glacial and inter- glacial epochs, and serve to intensify or to mitigate the severity of the glaciation due to elevation. The influences of these conditions would be nearly the same that are claimed for them * See Prestwich’s “Geology,” vol. i, chap. xvii, treating of the relative ages of the principal mountain-ranges of the world. 512 THE ICH AGE IN NORTH AMERICA. in the luminous glacial theory of Croll, but their origin and - effectiveness toward causing a glacial climate are here referred to extensive crust oscillations instead of eccentricity of the earth’s orbit. The prolonged warm interglacial epoch, or sev- eral such epochs, of which evidence is obtained in the Qua- ternary deposits of Kurope and North America, preceded and followed by severe arctic climate and ice-sheets, meet an ade- quate and consistent explanation in the view here taken ; and, indeed, the same reasoning that is presented by Croll in the details of the secondary elements of his theory seems equally applicable if these depend primarily on crustal elevation. The principal interglacial epoch in the United States, un- der this view, may well have been several times longer than either the previous or subsequent epochs of glaciation, or than the whole of post-glacial time, as claimed by McGee ;* but it does not follow that an exact parallelism will be found in the — glacial history of Europe. Former extension of vast glaciers in the Rocky Mountains and Andes, the Pyrenees and Alps, the Atlas range, the Caucasus, the Himalayas, and elsewhere, far exceeding the glaciers of the present time, may be due to the uplift of these mountains much above their present height, followed by subsidence t+ with retreat of the ice ; but these os- cillations and resulting alternations of climate were not proba- bly synchronous everywhere. ‘The highest mountain-ranges in four grand divisions of the world—namely, Asia, Europe, and North and South America—were doubtless largely uplifted and plicated, with formation of deep adjoining lakes, during the early part of the Quaternary period. Twice upheavals of the whole district of the Alps seem to have covered the region with great accumulations of ice, which each time may have depressed the area, first to be succeeded by the formation of interglacial deposits with lignite, and during each depression to send down floods, spreading loess along the Rhine, the Rhone, and the Danube.t After the later epoch of subsidence and glacial re- * “ American Journal of Science,” III, vol. xxxv, pp. 463-466, June, 1888. + A. Geikie’s “ Text-Book of Geology,” second edition, p. 934. + J. Geikie’s “Great Ice Age,” second edition, chapters xxxiii and xxxty, and his “ Prehistoric Europe,”’ chapters ix and xi. ~~ «as 227 ee OO ee ee i Ad ee ee lle THE CAUSE OF THE GLACIAL PERIOD. 513 cession, there seems to have been a renewal of elevation, as shown by the height and slopes of the loess. Asia had no extensive ice-sheet like those of Europe and North America, probably because a sufficient elevation was not attained there until the Himalayas and Thibet were uplifted in the Glacial period. Their southern latitude and the position of Thibet and Mongolia in an arid and partly rainless belt, which stretches thence west to the Sahara, forbade their glacia- tion ; but from these recently uplifted Asiatic table-lands and mountains the most extensive Quaternary deposits of the world have been brought down by rivers and spread in the vast low plains of Siberia, eastern China, and northern India, sloping gently toward the sea, into which the finer part of this allu- vium is carried. All the puzzling features of the Chinese loess formation,* reaching to great elevations with such thickness and slopes of its surface that it could not be so accumulated as alluvium of flooded streams under the present conditions, seem to be readily explained by referring its deposition to annual floods from immense snow-melting, during the European Gla- cial epochs, upon the gradually rising central part of the Asi- atic Continent, which consists largely of easily erosible strata, and had in preglacial time become extensively disintegrated by weathering under a dry climate. With this reference of glaciation primarily to oscillations of land, a new element of Quaternary history is introduced, which seems to help much in accounting for peculiarities in the areal distribution of identical or closely allied species of animals and plants that have doubtless sprung from a common source but have now become widely separated. Not only are we able to follow Gray in his tracing the origin of the big trees of California, of the species in the flora of the eastern United States—which are the same with species of Japan, China, and the Himalayan region, or are represented there by closely re- lated forms, though unrepresented in Hurope—and of mount- * Baron Richthofen, “ Geological Magazine,” II, vol. ix, 1882, pp. 293-305. J. D. Whitney, “ American Naturalist,” vol. xi, pp. 705-713, December, 1877. R. Pumpelly, ‘“‘ American Journal of Science,” III, vol. xvii, pp. 1383-144, Feb- ruary, 1879. -E. W. Hilgard, “American Journal of Science,” III, vol. xviii, pp. 106-112, August, 1879. 514 THE ICE AGE IN NORTH AMERICA. ain plants identical with those of the Arctic zone ;* but also we may now more satisfactorily bridge over the tropics and equa- tor, by uplifts and subsidences of mountain-ranges, so that species incapable of enduring a torrid climate could sometimes become dispersed even to such distances as from north tem- perate latitudes to Tierra del Fuego and the Cape of Good Hope. + It seems probable that the rate of the earth’s contrac has been somewhat uniform throughout the vast ages known to us by the researches of geology ; but the corrugation of the earth’s surface in mountain-building has been much more rapid in some epochs than in others, and between the times of for- mation of great mountain-ranges there have been long intervals. of quietude. { The slowly progressing contraction of the globe has been uninterrupted, and in some way the cooled outer part of the crust which has not shared in this diminution of volume has been able to accommodate itself to the shrinking inner mass. As stated on a previous page, this has probably resulted in distortion of the earth’s form, both of the whole thickness of the crust and of the probably molten interior, within mod- erate limits during the periods of quiet, until so much lateral pressure has been accumulated as to compress, fold, and uplift the strata of a mountain-range. In attributing the severe climate of glacial epochs to great uplifts of the areas glaciated through such deformation preparatory to the process of mount ain-building, it is distinctly implied that the Quaternary period has been at first exceptionally marked by such broad crustal movements, and has since gained comparative rest from the lateral stress to which they were due by equally exceptional Pee a * “Sequoia and its History,” “ Proceedings of the American Association for the Advancement of Science,” Dubuque, vol. xxi, 1872, and “ American Jour: nal of Science,” III, vol iv; “ Forest Geography and Archeology,” “ American Journal of Science,” III, vol. xvi, 1878 ; ‘ Characteristics of the North Ameri; can Flora,” ‘‘ Report of the British Association for the Advancement of Science,” Montreal, 1884, and ‘‘ American Journal of Science,” III, vol. xxviii. + Darwin’s “ Origin of Species,” chapter xi. Wallace’s “ Geographical Dis- tribution of Animals,” chapter iii, and his ‘“‘ Island Life,” chapter vii. t Dana’s “ Manual of Geology,” third edition, p. 795 ; Prestwich’s “ Geology " vol. i, chap. xvii. : THE CAUSE OF THE GLACIAL PERIOD. 515 plication, uplifts, and faults in the birth and growth of mount- ains. Further, it is implied also that stress in the earth’s crust had been gradually increasing through long previous time, while the processes of mountain-building failed to keep pace with contraction, but were still sufficient to keep the earth’s deformation less than is required to produce glaciation ; for no evidences of intense and widely extended glacial conditions are found in the great series of Tertiary and Mesozoic formations, representing the earth’s history through probably ten or fifteen millions of years. And indeed these conclusions, drawn from the Quaternary Glacial period and the absence of glaciation through vast eras preceding, accord well with the known age and stages of growth of mountain-ranges that have been formed during these eras. No epoch since the close of Palzeozoic time has been more characterized by mountain-building than the comparatively short Quaternary, whose duration may probably be included within one hundred thousand or two hundred thousand years. The continuation of the earth’s faunas and floras, with only very slight changes of species and exceedingly rare instances of extinction through the Quaternary period, not- withstanding its remarkable vicissitudes of climate and changes in the relative heights of land and sea, which seem especially adapted to produce both modifications and extinctions of or- ganic forms, bears indisputable testimony of the brevity of this period, when compared with those of Tertiary and Mesozoic time. As we extend our investigations backward in the geo- logic record, the species now existing are found in decreasing numbers until we come to the beginning of the oldest. In their places very different species, genera, orders, and groups _tenanted the earth before them ; and the gradual and doubtless very slow evolution of the present from the past must have re- quired duration almost incommensurable by years and centu- ries. But the total of mountain-building that has taken place during the Mesozoic and Tertiary eras is disproportionately small in comparison with that of the Quaternary period, even when ample allowance is made for long and very great denu- dation. Not until we go back to the Permian and Carboniferous periods are numerous and widely distributed proofs of very 516 THE ICE AGE IN NORTH AMERICA. ancient glaciation encountered. The atmosphere had been purified by the formation of Paleozoic limestones of great thickness, and by the storing up of the principal coal-deposits of the world ; and these changes in the air had quite surely produced eee diversities of climate than before existed, especially in respect to the range of temperature in the seasons and in the several zones. Alternating beds of coal, shales, and sandstones, which form the coal-measures, indicate oscillations of level and climatic conditions much like those of the Qua- ternary period ;* and bowlder-bearing deposits, sometimes closely resembling till and including striated stones, while the underlying rock also occasionally bears glacial grooves and striz, are found in the Carboniferous or more frequently the Permian series in Britain, France, and Germany,t Natal,t India,* and southeastern Australia.|| In Natal the striated glacier floor is in latitude 30° south, and in India only 20° north of the equator. During all the earth’s history previous to the Ice age, which constitutes its latest completed chapter, no other such distinct evidences of general or interrupted and alternating glaciation have been found ; and just then, in close relationship with extensive and repeated oscillations of the land, and with widely distant glacial deposits and striation, we find a most remarkable epoch of mountain-building, sur- passing any other time between the close of the Archean era and the Quaternary. The Appalachian Mountain system of the United States, with its grand plications and upheaval of the whole Paleozoic group of rocks, belongs to this epoch, and the same line of disturbance extends. by faulting and up- hifts northeastward to Gaspé and Newfoundland. In Europe * Croll’s “‘ Climate and Time,” chap. xxvi. + “Climate and Time,” chap. xviii; Wallace’s ‘Island Life,” chap. ix. t “Quarterly Journal of the Geological Society,” vol. xxvi, 1870, pp. 514—- 517; vol. xxvii, 1871, pp. 57-60. # “ Manual of the Geology of India,” Part I, pp. xxxv—xxxviii, 102, 109-112, 229. | “Quarterly Journal of the Geological Society,” vol. xliii, 1887, pp. 190- 196. “Die carbone Eiszeit,” by Dr. W. Waagen, “ Jahrbuch d.k.k. geol. Reich- enstalt,” Vienna, 1888, vol. xxxvii, Part II, pp. 145-192; reviewed in the “ American Geologist,” vol. ii, pp. 886-340, November, 1888. Ns leer: ak ~”, THE CAUSE OF THE GLACIAL PERIOD. O17 the Permian period ended with disturbance and mountain- building along a somewhat irregular west-to-east course through southern Ireland, Wales, England, northern France, Belgium, Germany, and southern Russia ;* and it is to be remarked that this European orographic line lies approximately in the same great circle with the Appalachian ranges, both being in- cluded by an arc of ninety degrees. Transverse to this circle the Sinian Mountain system of eastern Asia was formed in the same epoch, stretching from southwest to northeast along the border of the Old World as the Appalachians similarly bound our own contiuent.t{ Each of these mountain systems was perhaps much longer than the extent now remaining, and each has been reduced by erosion to only moderate heights ; but it is not improbable that their altitude originally was like that of the loftiest ranges of the world, some of which have been formed and the others much uplifted during the last geologic period. The shortness of the time that has elapsed since the latest glaciation of North America, according to the observations and computations of N. H. Winchell, Andrews, Wright, and Gilbert, shows that this cold epoch was not coincident with the period of eccentricity of the earth’s orbit, which is regarded by Croll, Geikie, and Wallace as the primary cause of the Ice age. Eccentricity, therefore, had no share in producing this most recent glaciation, which was more intense and severe, and probably more sudden and brief, than the earlier very cold epoch of the Ice age, as indicated by comparison of the mo- rainic and other drift deposits. Furthermore, it seems proba- ble that the Quaternary Glacial period, including its two or more epochs of glaciation, each subdivided by episodes of tem- porary retreat and readvance of the ice, besides the principal interglacial epoch of warm or temperate climate, and perhaps complete departure of the North American ice-sheet, was wholly subsequent to the maximum eccentricity which the * Prestwich’s “ Geology,” vol. i, p. 300. + ‘‘ Geological Researches in China, Mongolia, and Japan,” by Raphael Pum- pelly, “‘ Smithsonian Contributions,” vol. xv, 1867, chap. vii. The conclusions reached by Pumpelly concerning this mountain system are fully confirmed by the subsequent grand work of Baron Richthofen on the geology of China. 518 THE ICH AGE IN NORTH AMERICA. earth’s orbit attained two hundred thousand years ago. Through all the past ages of geology, also, the earth has from time to time passed through similar stages of increased eccen- tricity, sometimes having a still higher maximum,* which we should expect, in accordance with Croll’s theory, to find re- corded by deposits of glacial drift intercalated in the Tertiary, Mesozoic, and Paleozoic strata of circumpolar and temperate regions. But the recentness of the Quaternary glaciation, and the general absence of earlier drift formations,+ excepting within the Carboniferous and Permian periods, seem to demon- strate that eccentricity has not been the primary cause of gla- ciation, either with the concurrence of climatic conditions and changes of the course of winds and of oceanic currents such as might attend its slight modifications of the seasons, while the present arrangement and relative heights of land and sea were unchanged, or, as Wallace suggests,{ with much greater elevation of the areas glaciated, which he thinks to have been necessary, seconding the effects of eccentricity, for the accumu- lation of ice-sheets. Indeed, we may well doubt that eccen- tricity has exerted any determining influence in producing unusual severity of cold either during the Quaternary or any former period. Elevation of broad areas, as half of North America and half of Europe, either synchronously or in alternation, to such heights that their precipitation of moisture throughout the year was nearly all snow, forming gradually ice-sheets of great thickness, seems consistent with the conditions of the earth’s crust and interior, which are indicated by the changes in the levels of glaciated countries. A molten magma beneath the solid crust appears, in connection with contraction of the earth * Croll’s ‘Climate and Time,” chap. xix, with plate iv, representing the variations in the eccentricity of the earth’s orbit for three millions of years before A. D. 1800, and one million of years after it. + Nordenski6ld reports that, in sections observed by him in Spitzbergen and Greenland, including all formations from the Silurian to the Tertiary, and occu- pying in the aggregate, as he estimates, not less extent than a thousand English miles, he has never observed erratic blocks nor any evidence of glacial action.— “Geological Magazine,” IT, vol. ii, 1875, pp. 525-532, and vol. iii, 1876, p. 266. + “Island Life,” chaps. viii, ix, and xxiv. THE CAUSE OF THE GLACIAL PERIOD. 519 and the formation of mountain-ranges, to afford an adequate explanation of glaciation. It is probable that the great up- lifts which are thus supposed to have caused ice-accumulation were very slow in their progress, and that their effect upon extensive continental areas was so distributed that the maxi- mum changes in slope on thei borders would nowhere exceed twenty or thirty feet per mile, while perhaps some portions of the uplifted region would receive no change of slope. And the subsidence beneath the weight of accumulated ice was probably equally slow and similarly distributed, no limited district being greatly changed. Excepting the rare instances where disturbances of mountain-building or extraordinary ris- ing or sinking of mountain-ranges were associated with these movements, the contour of the country, with its valleys, hills, and mountains, has remained in general the same from pre- glacial time through the Ice age to the present with only changes of slope, small in any limited tract, which in long distances allowed great upheavals and depressions. The ele- vation of the central part of glaciated areas, with downward slopes on all sides, would favor the outward flow of the ice-sheets and their erosion and transportation of the drift. But mount- ains and hills jutted upward in ridges and peaks within the moving ice-sheet, as they now stand forth in bold relief above the lowlands; and the ice with its inclosed drift was pushed around and over them, some portions being deflected on either side, and usually a larger part being carried upward across their tops. Katahdin, the White Mountains, the Green Mount- ains, and the Adirondacks, stood directly in the pathway of the ice outflowing southeastward from the Laurentian high- lands. Its thickness in northern New England and northern New York seems to be measured approximately by the eleva- tion of the highest of these summits above the adjoining low- lands, about one mile; but northward the ice-sheet evidently was somewhat deeper upon the valley of the St. Lawrence, and Professor Dana’s estimate seems still reliable, that its maxi- mum depth, lying on the water-shed between this valley and Hudson Bay, was probably about two miles. 520 THE ICE AGE IN NORTH AMERICA. SUPPLEMENTARY NOTES. By WARREN UPHAM. The twenty-one years which have elapsed since the prep- aration of this chapter have not furnished any facts mate- rially to modify the views here presented. ‘The most impor- tant additional discussions of the subject are those of Messrs. Chamberlin and Salisbury advocating an atmospheric the- ory,* which they state as follows, when treating of the Permian Glacial epoch. “The increased area of the land, and its increased ele- vation, give increased contact between the atmosphere and the rocks of the earth susceptible of carbonation and oxida- tion, as already indicated. As a result, the atmosphere lost carbon dioxide and oxygen at a more rapid rate than in the previous period.” Here, and in other extensive developments of this theory by Chamberlin in the ‘‘Journal of Geology,” it is definitely shown that the supposed decrease of carbon dioxide, re- garded as the chief cause of glaciation, is ascribed to in- creased altitude of continental areas. In other words, the new theory espoused by Chamberlin and Salisbury, depends in the same way as my epeirogenic theory, called by them the “hypsometric hypothesis,’”’ on exceptional continental elevation. Each view recognizes two periods so preémi- nently characterized by extensive ice-sheets, namely, the Permian and the Pleistocene, that we must believe, from the records of glaciation, that they each had much greater land altitude, for large parts of the continents, than any other period in all the vastly long ages of geologic time. The great epeirogenic elevations preceding and causing both the Permian and Pleistocene ice ages are well emphasized in the foregoing pages; but there we had not learned how the * See ‘‘Geology,’’ vol. ii, pp. 655-677; vol. iii. pp. 424-446; also above p. THE CAUSE OF THE GLACIAL PERIOD. 521 ordinary meteorologic conditions of high land elevation were reinforced, in their tendency to produce ice-sheets, by the concomitant depletion of atmospheric carbon dioxide. Now, through the fruitful studies of Arrhenius, Chamberlin, and others, we see how the great altitude of the Continents at these two periods of great areas of long continued glaciation, so very widely separated in time and therefore remarkably unique and exceptional, worked in two ways, not only by _ the common meteorologic effects, but also by the newly recognized results of depletion of carbon dioxide, to give the marvelous glacial periods thus ending Paleozoic and Ceno- zoic time. Further studies will give the proportional effectiveness of these two ways by which great uplifts of the continental areas have induced glaciation. ‘The final theory will rest not less on the sagacious early views of Dana, with their further advocacy by Le Conte and other writers, including Wright and myself, than on the very helpful work of Arrhen- jus and Chamberlin in their added contribution to explain how the land uplifts accumulated ice-sheets with snowfall all the year upon their vast expanses. Indeed I yet think, that the broad view of the causation of glacial periods as given above was presented truly and vividly, with no more than the proper emphasis on the-very exceptional occurrences of only these two periods of general continental glaciation. Coming next to the great question whether the Pleistocene ice-sheets of North America and Europe were wholly melted away, as is argued by Professor James Geikie and less decid- edly by Chamberlin and others, we cannot adduce sure proofs for such conclusions from the central areas of these great ice-sheets on the opposite sides of the Atlantic ocean. The interior of New England and of British America, like the central parts of Sweden and Norway, have not yet revealed such sequence of glacial deposits and intervening fossiliferous beds, of somewhat temperate faunas and floras, 022 _ THE ICE AGE IN NORTH AMERICA, as to give any conclusive evidences of complete departure of the ice-sheets and their subsequent renewal to again spread over nearly all of their former areas. Only in the peripheral parts, broadly speaking, of these two immense ice-fields, are proofs of successive stages of glaciation, divided by old land surfaces and fossil-bearing stratified beds, either of the modi- fied drift or of alluvial, lacustrine, or marine sedimentation. Minnesota, somewhat far back from our southern lim- its of the maximum glaciation, has well ascertained proofs of so great recession.of the borders of the North American ice-sheet as to uncover the south half of this state, succeeded by renewal of the snowfall and ice accumulation until the borders of our continental ice-sheet again reached southward as far as the Iowan and the Wisconsin drift. The earlier glaciation appears surely to have been of much longer dura- tion than the later Iowan and Wisconsin stages. Thus our Pleistocene Ice age was much diversified and even very com- plex, yet I would now far more confidently ascribe all our North American drift formations to one prolonged and con- tinuous glacial period, with great fluctuations of the glacial border, especially in the interior of the continent, than to regard our ice age as two-fold or three-fold, in the sense of having its vast ice-sheet wholly melted away, or even nearly so, with ensuing renewal of the snow and ice-fields. Geologically very rare, an ice age would scarcely be dupli- cated with so nearly the same limits of ice extension upon half of our continent. The same general conclusion is also, as I think, applicable to the European glaciation. Almost inconceivable geologic duration divided the Permian and Pleistocene Ice ages. In this most recent and geologically _ short Ice age which has ended, as I surely believe, within the last 10,000 to 5,000 years, at the threshold of the historic period, I cannot think that the stupendous climatic changes implied in the glaciation could permit complete repetition of these continental ice-sheets in America and Europe, in THE CAUSE OF THE GLACIAL PERIOD. 523 each area so closely extending to nearly the same maximum limits in the earlier and the later parts of this Glacial period. It is better, until proofs are obtained in the central regions of the drift areas on each continent, to regard. their time of glaciation as one and continuous, with much areal oscilla- tion, such as is proverbial of weather, both during the gen- eral stages of growth and departure. My explorations of the Minnesota drift deposits, so far _as they appear to require great recession and later reidvance of the snow and ice accumulation, may be cited in the final reports of our state geological survey, the most notable of these observations being as follows, supplementing Prof. N. H. Winchell’s observations of an interglacial forest bed in Mower county and other localities of southern Minnesota.* 1. The exceedingly interesting and elsewhere unequaled chains of lakes in Martin county, one of the central counties of our most southern tier, I can explain only by regarding them as proofs of a fully developed interglacial system of drainage running there from north to south, which became afterward ice-enveloped in the Iowan and Wisconsin stages of our Glacial period. 2. Somewhat the same conclusion seems again enforced by the section of the drift close southwest of New Ulm, in Brown county, about 40 miles north of these chains of lakes. 3. In the northern part of Chisago county, on the east side of Minnesota, Rushseba township, in which Rush City is situated, about 50 miles north of St. Paul and Minne- apolis, has a considerable tract,§ some 5 or 6 miles long and of nearly as great width, where reddish-modified drift, spread by streams flowing down from the receding northeastern *See below p. 605. t ‘‘Geology of Minnescta,”’ vol. i, 1884, pp. 479-485, with the map facing page 472. t Ibid, vol. i, pp. 581-3, with section, and with map facing p. 562. § ‘Geology of Minnesota,” vol. ii, 1888, pp. 409-415, 417, 418, the last giving the record of that well, with the map facing page 399. 524 THE ICE AGE IN NORTH AMERICA. lobe of the ice-sheet, forming for a time a land surface which bore timber, was subsequently overspread by an ice-lobe whose current was from the northwest to the southeast and east. The overlying yellowish gray till, spread as a continu- ous and nearly uniform bed only ten to twenty feet thick and forming a nearly level expanse of so much extent, at least 5 miles in diameter, has plentiful limestone fragments from the northwest, being thus in remarkable contrast with the red till deposits lying beneath the gray till in that region, which came from the northeast and therefore has no lime- stone. A well’ on this area encountering peat and decaying fragments of wood in a water-deposited clay beneath the gray till and at the top of the older underlying modified drift gravel and sand, testifies that this was a land surface with peat and forest trees, previous to the-very latest glaciation which brought the yellowish gray till.* 4. On the southern part of the area of the Glacial Lake Agassiz, at Barnesville in Clay county, about 190 miles northwest of the Twin Cities (St. Paul and Minneapolis), a well penetrates twelve feet of till, and next beneath, in the bottom of the well, went one foot into quicksand, ‘“‘contain- ing several branches and trunks of trees, thought to be tam- arack, up to eight inches in diameter, lying across the well, which, together with the inflow of water, prevented farther digging.”’ This well is on the till area of the village of Barnes- ville, about eighty feet below the highest beach of Lake Agassiz, which passes from south to north about three miles east of this village. At the time of my survey of that region and when this volume was published, in 1888, I considered the occurrence of this interglacial bed within the area of the glacial lake as good evidence that the ice-sheet in that inter- glacial stage was melted back at least so far as to give out- flow into Hudson Bay from the Red River Valley, draining off the interglacial forerunner of Lake Agassiz. ‘Subsequent studies and general reasoning lead me, however, now to hold * See above p. 184. THE CAUSE OF THE GLACIAL PERIOD. 525 the different view that probably the earlier interglacial lake in this valley may have even cut its channel of southern out- let, at the site of Brown’s Valley, to a lower level than the well in Barnesville, or that the attitude of the land then was unlike what it now has, having then such an ascent from south to north that the Barnesville locality in that inter- glacial time was above the general surface of the region at Brown’s Valley, into which the River Warren, outflowing from Lake Agassiz, cut its deep continuous valley. So I now think that we have there, in the section of this well, only evidence of an ice retreat (that is, a departure of the outer part of the ice-sheet) so far north as to that region, about halfway between the south and north boundaries of this state.* My numerous papers show how, as I think, good forests and other luxuriant vegetation may have flourished near the border of the ice-sheet, accompanying the recession of that border. The questions are sure to be asked: Why is the boundary of the glaciated region in the United States so irregular ? What was the cause of its withdrawing so far north in western New York, and of its sudden bend to the south in eastern Ohio, and of its lobe-like projections in southeastern Indiana and southern Illinois? And what was the cause, at a later stage, of the lobate contour of the moraines west of Lake Michigan in Wisconsin, Iowa, Minnesota, and Dakota? These questions we can only answer by saying that the distance to which the great American ice-sheet penetrated the southern latitudes was evidently not dependent, to any great extent, upon the elevation of the land over which it was compelled to move. The ice did not uniformly move farther south where there was a depression of the land, and the boundary does not ordinarily retreat to the north on account of the higher elevations opposing its progress. South of New England the * Geology of Minnesota, vol. ii, pp. 661-2, and 668; with the map facing p. 656. 526 THE ICE AGE IN NORTH AMERICA. glacial front was at the sea-level, and the ocean itself may have kept it from advancing farther. In Pennsylvania the boundary-line crosses the Alleghany Mountains diagonally, being nearly as high on Pocono Mountain, in the’eastern part of the State (about two thousand feet), as in the southwestern part of New York, where it is sixty or seventy miles farther north. In Ohio the highest portion of the State is in Logan county, almost directly north of Ripley, in Brown county, the most southern point reached in that. State. The unglaci- ated portion in southern Indiana, projecting about seventy miles northward into the glaciated region, is indeed some- what higher than the land on either side, but nowhere is its elevation greater than that of the larger portion of Ohio. The farthest extension of the ice in Illinois is closely coinci- dent with the trough of the Mississippi Valley, and westward of the Mississippi River the edge of the ice withdrew farther and farther north pretty nearly in proportion to the increas- ing elevation of the country, until, at Sim’s Station, in the vicinity of Bismarck, Dakota, it is nineteen hundred and sixty feet above tide, and continues thence to ascend northward to a height of three or four thousand feet in the upper valley of the Saskatchewan. | There is, thus, a general conformity in its southern exten- sion to the valley of the Mississippi. The ice of the Glacial period as a whole did, indeed, move down that great valley, and its most southern point is in the middle of it, where it it is not more than five hundred feet above the sea; but it is evident that the total width of the southern portion of this ice-sheet is so great, and the slope itself so slight, that this depression could not have been the main cause of the great extension to the south in Illinois. The width of the glaci- ated area from southern Ohio to eastern Kansas, on the thirty- ninth parallel, not far from the extreme limit of glaciation, is nearly a thousand miles. The cause, therefore, of the lo- bate character of the southern boundary must, in all proba- bility, be sought in the irregular areas of excessive snow-fall existing to the north during the advance and continuance of THE CAUSE OF THE GLACIAL PERIOD. 527 the Glacial period. From a glance at the map it would seem, therefore, that the greatest area of snow-fall was somewhere in the vicinity of Lake Superior, and that a secondary area of large snow-fall was in the vicinity of Labrador; for the south- ern boundary of the glaciated region consists essentially of the ares of two circles whose centers would fall within the areas indicated. | In speaking of these two areas as centers of radiation for the glaciers of the great Ice age in North America, it is not affirmed that the movement received no impulse from still farther north. It is not improbable that the upper portion of Baffin Bay was filled and crossed by the glaciers still lingering over the continental area of Greenland, and that this Greenland ice aided in the movement which covered the northern part of the United States with its icy mantle. But it was probably by reaction rather than by direct action that aid came from that quarter. The accumulations to the north prevented an outflow in that direction, and so compelled a southerly movement from the vicinity of the Laurentian highlands. It is not, however, probable that any Greenland ice ever reached the United States. None of the bowlders so common in the United States are, so far as known, more than a few hundred miles distant from their parent ledges. There was doubtless all the while an ice-stream down Bat- fin Bay toward the Atlantic Ocean, with a movement into it from both sides. But even if this were not the case, the areas south of Hudson Bay and in Labrador would still be the predominant influence in determining the southern out- line of the glacial boundary. The snow that piled up from year to year over those centers would be compelled to move off in the lines of least resistance. Now, ice can be an ob- struction to other ice as well as to water; and what the . Greenland glacier probably did was to close up the upper portion of Baffin Bay, so that the excess of snow-fall over the subcenter referred to as north of Lake Superior could not move off to the northeast, but was compelled to spend all its force in a southerly movement. It is evident also that 528 THE ICE AGE IN NORTH AMERICA, every subcenter where the snow-fall was larger than the average would, to some extent, make its influence felt upon the shape of the margin. Here is a field for the mathematician. When the prop- erties of ice are more fully understood from experimental investigations, and the laws of its fluidity brought under mathematical formule, it will doubtless be possible, from a study of the contour of the glacial boundary, to calculate the position of all the principal areas of largest precipitation during the Glacial period. Those remarkable lobe-like projections in southern Ohio and Indiana, for example, indicate subcenters of accumu- lated ice not far back from the margin. The still more remarkable prolongation of the loops in the kettle-moraine in Wisconsin, and its extension through the States farther west, point, as President Chamberlin sagaciously and cor- rectly supposes, not merely to greater snow-fall over the regions from which the ice-emovement radiated, but to the conservative influence of the deeper valleys and depressions to the north, which were filled with ice. These loops of the kettle-moraine sustain a remarkable relation to the valley of Green Bay, and to the northeast and southwest axis of Lake Superior, while the ice-lobe which occupied the valley of the Minnesota and extended to the center of Iowa is evidently related to the great valley of the Red River of the North. It is not improbable that the depth of ice in such a depression as Lake Superior would, by its very thickness, tend for a long time to increase the snow-fall over its own area, and in other ways to resist the antagonistic agencies which were gradu- ally driving the ice-front back to the north. The driftless area of southwestern Wisconsin is situated just where it es- capes these several ice-movements dominated by the depths of Lake Michigan and Lake Superior, and it is to this day— as Professor Dana has pointed out—a region of light pies | tation. If this discussion of the cause of the Glacial period seems unsatisfactory, the justification is that the present ‘ ee THE CAUSE OF THE GLACIAL PERIOD. 929 knowledge of the whole subject is in an extremely unsatis- factory condition; and in this, as in other things, the first requisite of progress is to squarely face the extent of our ignorance upon the question. The causes with which the glacialist deals are extremely complicated, and yet they are of such a nature as to invite investigation, and to hold out the hope of increasing success in mastering the problem. There is opportunity yet for some Newton or Darwin to come into the field and discover a clew with which success- fully to solve the complicated problem which has so far baf- fled us. To the genuine investigator it is a source of inspi- ration rather than of depression to have such an untrodden field before him. Conciusion.—Geology is pre-eminently a terrestrial sci- ence, and there is danger of a misdirection of effort when the geologist forms an alliance with the astronomer. Astro- nomical data are so largely theoretical, and the quantities which the astronomer multiplies are often so nearly infinitesi- mal, that quantitative error is in peculiar danger of becom- ing enormous in large calculations. Hence, we can not count it altogether an advantage that astronomical speculation has been so rife during the past few years in determining the causes and the chronology of the Glacial period. Of the various cosmical theories to account for the Gla- cial period, that of Mr. Croll is by far the most plausible and interesting. It must be admitted that his data concerning the various distances at which the earth is, found from the sun during the winters of different periods, and concerning the periodical variations in the length of the winters, rest upon well-ascertained facts. It is no doubt true that about one hundred thousand years ago the winters were at times several days longer than now, and the northern hemisphere was receiving daily considerably less heat than now, since it was several millions of miles farther away from the sun. But the distribution of the earth’s heat by winds and oceanic currents is a subject concerning which much less is known. The phenomena presented in a hot-house are puz- 530 THE ICH AGE IN NORTH AMERICA. zling. The heat of the sun goes through the glass, but can not readily get out again. It is well known, also, that a slight increase of moisture in the atmosphere, or a slight film of cloud over the sky, prevents a frost. The real prob- lem lies, therefore, in the meteorological field. Now, during Mr. Croll’s “ aphelion ” winters, the summers are in “ perihel- ion,” and the summer heat in this hemisphere while in peri- helion is more intense than at other times. In fact, the earth receives at all times the same absolute amount of heat from year to year. Thus, we can not avoid the conclusion that the predominant influence in climate may consist in the power of moisture-laden atmosphere to retain and transport the heat, thus determining its distribution. As a matter of fact, we find that the equator is not so hot as theoretically it should be, and the arctic regions are by no means so cold as, on Croll’s theory, they ought to be. . The difference between the mean temperature on the equator and that at the coldest point on the sixty-seventh parallel is really only about 75° Fahr.; whereas, if the temperature at these points were pro- portionate to the amount of heat received from the sun, the difference would be 172°. Such facts as these lead meteor- ologists to regard Mr. Croll’s theory with much less favor than formerly. nee But the glacialist is not so much concerned to know the ultimate cause of the Glacial period.as he is to collect the facts which characterize the period. The truth is, that the meteorological forces of Nature are so powerful and complex that there is an embarrassment of riches in the field of gla- cial theory. It is easy to see that a slight increase of snow- fall over the Alps would cause a permanent enlargement of all the glaciers of Switzerland, and threaten every interest of that republic, and perhaps of central Europe; for the ulti- mate effects of a climatic disturbance in one such center can not well be estimated. Much light upon the condition of things during the Gla- cial period in America must yet come from a careful study of the lobate contour of the terminal moraines. The shapes j ut — Ss ee THE CAUSE OF THE GLACIAL PERIOD. 531 of these moraines, coupled with what may yet be learned concerning the nature of ice and concerning the shifting course of the atmospheric currents, will, in all probability, eventually furnish the data for the solution of the question of the true cause of the Glacial period. A fair field here invites the active and prolonged attention of some future meteorological Darwin or Newton, and promises immortality such as they have attained. CHAPTER xk THE DATE OF THE GLACIAL PERIOD. Two causes have combined in recent years to favor erro- neous calculations concerning glacial chronology. Of these, the first has been the almost unquestioned acceptance of the astronomical theory subjected to examination in the preced- ing chapter. If Mr. Croll’s theory of the cause of the Gla- cial epoch is correct, then we should no longer speak of an ice age, but of a succession of such ages, whose dates could be readily determined from a table showing the periods of high- est eccentricity in the earth’s orbit. According to this table, the modern period most favorable to the production of a glacial epoch began about two hundred and forty thousand years ago and ended about seventy thousand years ago. The whole intervening time was one of high eccentricity, when, during the recurring intervals in which the winters occurred at aphelion, the excess of winter over summer ranged from fourteen to twenty-six days, and the intensity of the heat received from the sun during those aphelion winters was ten per cent less than at the present time. During the time in- tervening between seventy thousand and two hundred and forty thousand years ago, there occurred, therefore, according to this theory, a succession of glacial and interglacial periods in which geologists and archzologists are invited to distrib- ute their remarkable discoveries concerning glacial man. Undue confidence in this theory has had no small influence in diverting attention from the more legitimate lines of in- vestigation. A second source of error has been an incorrect interpre- ‘plage 668 008 oot 6 069 003 —_—_S——oSSS———Ssr - 4333 JO 31V0S oN eT? STs ey OS 042 THE ICE AGE IN NORTH AMERICA. stream, composed of the waters of the Tonawanda and Chip- pewa Creeks, was of considerable extent, and by its action had doubtless predetermined the course of the present river above the Whirlpool, and may actually have worn a consid- erable part of the present gorge above the Whirlpool. Another element of uncertainty, which has led Mr. Gil- bert and others to retract their former views, or at least to hold them in suspense, relates to the variations of the water supply since the beginning of the erosion. It should, however, be noted that the erosion at Niagara began long before the close of the Glacial period, namely when the ice had melted off from the Mohawk Valley so as to permit the drainage to take that course to the Hudson, and lower the level of the existing glacial lake to that of the col at Rome, N. Y. This would permit erosion to begin at the mouth of the Niagara gorge, long before the ice had retreated from the lower St. Lawrence Valley and from Canada in general. A most interesting state of things respecting the varia- tions of the water supply at Niagara comes to light in connec- tion with the differential northerly depression of land during the Glacial period, and its re-elevation after the disappearance of the ice. From the fact that there was a northerly depres- sion of 600 feet at Montreal, and presumably as much in the northern basin of the Great Lakes, it follows that upon the melting off of the ice from the Ottawa Valley, and from the water parting between it and Lake Huron, the drainage might for the most part be diverted in that direction, leaving the Niagara with only that supply of water which would be fur- nished by the local basin about the east end of Lake Erie. In 1892, I was sofortunate as to find clear evidence of this outlet leading across from Lake Nippissing, past the town of North Bay, into the Mattawa River and thence into Ottawa at the town of Mattawan. The col at North Bay is less than 100 feet above the present level of Lake Huron, while the evi- THE DATE OF THE GLACIAL PERIOD. 548 dences of a post-glacial flow of water in enormous quantity are perfectly clear. At Mattawan there is an enormous delta of bowlders where the valley of the Mattawa joins that of the Ottawa. Many of the bowlders are several feet in diameter, and they are all waterworn. Moreover, the bowldery delta has been pushed out into the Ottawa Valley so as to dam the river and create a deep lake-like expansion above and a long series of rapids below. In confirmation of the theory that there was a flow of water through this channel for a consider- able time Mr. Taylor found miniature pot-holes worn in some of the large bowlders of the delta terrace at Mattawan. Of course while the drainage of the Upper Great Lakes was diverted around to the St. Lawrence by way of the Ottawa Valley, the recession of the Niagara gorge was practically at a standstill. It is important therefore to ascertain how long a time this continued. Calculations upon this point will largely depend upon the question of how rapidly the post- glacial re-elevation of the region went on. Happily we have much evidence upon this point, all of which indicates a rapid rate as compared with that which is now going on. The most important evidence comes from Dr. Upham’s study of the shore lines of the glacial Lake Agassiz which spread over the valley of the Red River of the North (see page 401). Thistemporary lake covered more than 100,000 square miles and its shore lines are easily traced for hundreds of miles, like railroad embankments, across the prairie coun- try of that region. There are several series of these shore lines, at successively higher levels. But at the head of the valley where the outlet was through Big Stone and Traverse lakes into the valley of the Minnesota River, the beaches are approximately at the same level. On proceeding northward, however, while the lower beach remains nearly horizontal, the upper one rises until in latitude 51° 52,’ 200 miles north of the international boundary, it is 400 feet above the lower shore line. Thus it appears that during the existence of this F 1a. 136—Exposure of Niagara shale in Niagara gorge. (Photo by Dutton). 14-2 __191_ 57 140 ~ 41 +3 NIAGARA Soca Wes Aa Niche wai) amo resort 4 S i BBE: i] t ‘ ‘ 4 naan ‘ ' DTT TE ry CLInTON { } sy FA =< Coty: MEDINA (01 pet o eo ee eo Fie. 137—Diagram showing small amount of actual enlargement of the mouthof Niagara Gorge at Lewiston. THE DATE OF THE GLACIAL PERIOD. 045 lake there was a rise of 400 feet in the northern part while there was a rise of but a few feet at the southern end. These facts give us a chance to estimate the rate of this differential rise in the land lying north of the glacial border which has been going on up to the present time, and thus furnishes data from which to calculate the length of time dur- ing which the depression at North Bay was sufficient to divert the water of the Upper Great Lakes from Niagara. From the data collected by Dr. Upham during his investigations of Lake Agassiz he concludes that its entire existence could not have been more than 2,000 years and probably was not more than 1,000 years. The facts upon which Dr. Upham relies, are: 1. The small size of the deltas deposited on the margin of the lake by the great rivers entering from the west; 2. The small size of the ridges themselves; 3. The limited extent of the dunes about the southern end of the lake. 1. The most important rivers which formed deltas in the lake are the Cheyenne, the Assinniboineand theSaskatchewan, which all come in from the region to the westward which was free from ice during the greater part of the time of the exist- ence of the lake. The gradient of these streams is rapid, and the supply of sand and gravel within their reach is abundant. Yet their delta deposits at the level of the beaches is small, and entirely inconsistent with the continuance of the lake for more than 1,000 or at most 2,000 years. 2. Theshore lines, or beaches, are very much smaller than those around Lake Erie, which, as we elsewhere show, could not have been more than 2,000 to 3,000 years in forming. 3. The dunes at the south end are not over one-tenth the size of those at the south end of Lake Michigan, which demon- strably were not over 10,000 to 15,000 years in forming. In explanation of this point it is necessary to call attention to the facts concerning the dunes south of Lake Michigan. These are very prominent features along all the railroads ag { Fic. 1388—Photograph looking north-west towards St. Davids showing the excessive ene largement of themouthofthe preglacial channel. ee 3 ee Fie. 139—Section, drawn to equal vertical and horizontal scale, showing enlargement of Niagara gorge on the east side at its mouth at Lewiston: 1, Niagaralimestone, 20 to 30 feet ; 2, Niagara shale, 70feet ; 3, Clinton limestone, 20 to 30 feet; 4, Clinton and Medina. shale, 70 feet; 5, Quartzose Medina sandstone, 20 to 30 feet; 6, softer Medina sandstone, 120 feet above water level. THE DATE OF THE GLACIAL PERIOD. 547 entering Chicago from the east, but theyare limited in extent, and are in process of formation at the present time, the rate of which can be approximately calculated. Lake Michigan is now a closed body of water at the south end, and it is eating into its western banks and bluffs at a rapid rate, the shelf eroded by the waves since the departure of ice from its central depths being about seven miles wide. The shingle, gravel and sand derived from this erosion of the banks is carried along the west shore southward past Chicago to the south end of ITE: j i +... On ne - Fig. 140—Hypothetie hydrography of the Great Lakes at a date after the melting of the great glacier from the St. Lawrence Valley. the lake, where it is taken up bythe wind and blown outward to form the dunes which are now so prominent a feature in the landscape. It has been important for various reasons to learn how fast the sand is being carried past the Chicago front, so that engineers have made very careful estimates. On comparing the rate at which the material is being carried past Chicago, with the total amount of sand contained in the dunes at the south end of the lake, it appears that the process cannot have been going on more than 10,000 years. Now, since Dr. Upham estimates that the dunes at the south end of glacial Lake Agassiz are not over one-tenth the 548 THE ICE AGE IN NORTH AMERICA. size of those south of Lake Michigan, those on Lake Agassiz would have been formed in about 1,000 years. Hence this differential northerly elevation of land over the basin of Lake Agassiz to the extent of 400 feet must have taken place within that limited period. Such being the ascertained rate of elevation in the Red River Valley, it is altogether probable that the rise in the land at North Bay would not occupy a much longer period, for the conditions with respect to the glacial ice and its recession are nearly alike in both regions. In addition to this evidence adduced by Dr. Upham, I had long before called attention to the small amount of erosion which had taken place in the delta at Mattawan since the glacial outlet there had been closed. Another independent line of evidence indicating the brevity of the past life of the Niagara gorge is drawn from a study of its width at the mouth. In 1898 and 1899 I was deputed by the New York Central Railroad to study the lower part of the eastern side of the gorge, to shed what light I could upon the stability of the conditions surrounding the road bed built along the face of the gorge. Every facility for examination and measurement was granted me. Briefly, the results were as follows: the width of the river at the mouth of the gorge is 770 feet, which is practically the original width of the gorge, for the débris falling down has prevented the stream from enlarging its channel at the base of the cliff. Assuming that the cliff was originally perpendicular, measurements showed that the strata at the summit had receded on the east side only to the extent of 388 feet, making the total width of the top of the gorge at the mouth 1,553 feet, on the supposition that the west side had been worn away as fast as the east side had been. But various irregulari- ies prevented as accuratemeasurementsonthatside. Nowthis subaérial erosion of 388 feet from the top of the gorge on one side indicates the removal of an inverted section of the face of the gorge, with a base of 388 feet and a height of 340 feet, of New York Central Railroad. st side of Niagara Gorge, at its mouth; showing course X—Section on ea PLATA f= of AY THE DATE OF THE GLACIAL PERIOD. 549 the height of the cliff at this point. If the subaérial erosion of the face of the gorge proceeded at the rate of one-quarter of an inch per annum, the material would have been removed in less than 10,000 years. That this rate is not excessive was shown both from the vast amount of débris that is now annually precipitated upon the railroad track, and from actual measurements of the extent to which the hard strata of lime- stone had been undermined since the track was laid, in 1854, when it was found that the underlying Clinton and Niagara shales had worn away more than three inches a year, leaving the harder strata to project from thirteen to fourteen feet. As illustrating the rapidity of erosion from the sides of the gorge it is in point to remark that in 1898 there fell off at one time from the face of the cliff on the east side of the Whirlpool, 100,000 tons of rock, whereas the amount which we have supposed to fall away annually from the one mile and a half measured by us is only 1,237 tons. From these facts it is evident at once that the erosive agencies tending to give a V-shape to the mouth of the gorge could not have been in operation much more than 10,000 years. To suppose they had been at work for 30,000 or 40,000 years, as many still try to do, involves an absurdly low rate of activity on the part of the forces which have been constantly at work. Something more also needs to be said about the significance of the preglacial channel leading from the Whirlpool to St. Davids. In the first place it should be noted that the mouth of this gorge is very wide, being in fact nearly a mile in width, thus indicating great age. In the second place, the depth of the Whirlpool (150 feet), and the width of the head of the St. Davids gorge (fully twice that of the Niagara gorge immedi- ately above and below), point to an extreme age. It seems altogether probable, indeed almost demonstrable, that the St.Davids’ gorge had been worn back by a small stream formed by the junction of two streams, one coming along the line of the present gorge through the Whirlpool Rapids, and the 550 THE ICE AGE IN NORTH AMERICA. other coming from the north from asmall water shed bounded by the escarpment at Queenston. As the gorge both above and below the Whirlpool is for some distance not more than one-half the average width, it is probable that through these spaces these small streams had worn in preglacial times narrow gorges leading to the Whirlpool which had only to be cleared of their glacial débris and somewhat enlarged by the present stream when the cataract had receded to that point. This would account both for the narrowness and the shallow- ness of the gorge at these places. Whereas the water at the Whirlpool is 150 feet deep and still more than that for two miles below the Falls, it is only 35 feet deep in the Whirlpool Rapids. Furthermore, at Fosters Flats, one mile below the Whirlpool there is a projecting shelf extending into the gorge from the western side nearly half its width, but into its upper end on the side next to the main cliff there is the head of an old narrow gorge opening up stream. This can hardly be anything else than a remnant of the gorge supposed to have been formed by a small northerly stream which found an outlet through the Whirlpool. We are bound to state, however, that Dr. Spencer main- tains that the St. Davids outlet was not worn down to the level of the present Whirlpool, and so is only a remnant of erosion in some preceding era. But it is to be observed that Dr. Spencer’s borings to determine the depth of the glacial filling in the St. Davids gorge, were considerably one side of the center, while the measurement nearest the. center was abandoned before penetrating the rock below. The great age of the gorge would imply a fully formed V-shape for it, which would make the depth of the glacial filling to be small near the sides. There is, therefore, no valid reason to doubt that the St. Davids preglacial outlet was complete from the Whirlpool at a depth equal to that of the present Niagara gorge. In view of all these considerations it seems evident that a TH#H DATE OF THE GLACIAL PERIOD. 551 considerable portion of the erosion of the Niagara gorge, both above and below the Whirlpool, had been accomplished before the glacial period, so that all the present stream had to do was to clear of its unconsolidated till the portions of the preglacial gorge which it occupied, and somewhat widen the channel. For future reference, if for nothing else, it is worth while to introduce at this point a portion of our detailed study upon the rate at which lateral erosion is proceeding through atmospheric influences alone along the face of this gorge. In | Miaygara Ls. tagara SA. Sec 78 See TT Fie. 141—Sections showing the actuol rate of erosion along the sides of the Niagara Gorge. Section I was made 860 feet south of the tunnel at the north end of the gorge, and the measurements were taken from the outer rail of the track at points where a perpendicular excava- Say ee THE ICE AGE IN NORTH AMERICA. tion in the Clinton Shale had been made fifty-five years be- fore. The average of fifteen measurements.made at twenty foot intervals, showed that at the line of greatest erosion fourteen feet of the Clinton Shale had fallen away during that period; giving a rate of three inches a year. Section II was made 6.317 feet from the tunnel in what was a perpendicular excavation in the Niagara Shale fifty-five years before. The average amount of greatest erosion along this exposure was obtained by eleven measurements through- out a distance of 1.185 feet, and proved to be fourteen and eight tenths feet, or three and one quarter inches per year. From these measurements it appears that the rate at which the Clinton and Niagara shales crumble away-over the whole surface, through atmospheric agencies alone where unpro- — tected, is one and a half inches per year. The question as to how much protection has been afforded by the talus and the growth of vegetation cannot be defi- nitely answered, but as our photograph on p. 544 shows the Niagara shale has not been protected to any extent by a talus, and but slightly by vegetation. It therefore seems entirely within the bounds of probability that the erosion of the Nia- | gara Shale at the mouth of the gorge has proceeded at one- seventh the rate at the exposures measured, which is about one quarter of an inch per year, or one foot in forty-eight years, which is the rate necessary to accomplish the whole amount in 10,000 years. A second typical place for the study of the recession of post-glacial waterfalls is presented in the gorge of the Mississippi River below the Falls of St. Anthony at Min- neapolis. The problem here presented has been carefully studied by Professor N. H. Winchell as follows.* - From the Falls of St. Anthony to Fort Snelling the gorge between the rock-bluffs is somewhat less than a quarter of a * “Geology of Minnesota,’’ vol. ii, pp. 313-316, 340, 341. THE DATE.OF THE GLACIAL PERIOD. 503 mile in width, and the rock has a freshly broken appearance, the large fragments thrown down by the action of the water on the easily crumbled sand-rock, as the falls have receded, still existing in the talus along the bluffs. Throughout this distance (about eight miles) the strata are horizontal, the thick- ness of the drift-sheet overlying them nearly uniform, and all other conditions, so far as they can be seen, that would affect the rate of recession, seem: to have exerted an unvarying in- fluence. The inference is inevitable that the rate of recession has been practically uniform between the two points named. There is an aspect of age, and long weathering, presented by the rock in the bluffs of the Mississippi below Fort Snelling. It has a deeply changed color, a light-yellow, oxidized exterior, which marks all old bluffs. The blue color is found at greater depths from the surface than it is in the rock of the bluffs above Fort Snelling. This stained condition also pervades the lime-rock at the mouth of Bassett’s Creek and at the quarries in the ancient river-bluffs near the mouth of Shingle Creek, on both sides of the river. Another notable difference between the bluffs above Fort Snelling and those below consists in the absence of caves, and subterranean streams entering the river, above Fort Snelling. Although the Trenton limestone exists in full force about St. Paul, in the bluffs east and north of the city, yet it had been cut through by some means prior to the drift so as to allow the entrance and exit of streams of water at levels below its horizon through the sandstone. None such are found above Fort Snelling. The surface drainage is shed by the limestone, and is precipitated over the brink of the gorge, forming several beautiful cascades. When such streams enter the river below Fort Snelling, they either enter some subterranean passage and appear at the mouths of caverns in the sandstone, or as springs in the drift along the talus, or they find an ancient ravine down which they plunge, by a se- ries of rapids over bowlders, to the river-level, rarely striking either the lime-rock or the underlying sand-rock. Again, the rock-bluffs at St. Paul, and everywhere below Fort Snelling, are buried under the drift-sheet. Their angles are sometimes seen jutting out from some wind-beaten corner, but nearly everywhere thev are smoothed over by a mantle of drift and oo4 THE ICE AGE IN NORTH. AMERICA. loam. Even the immediate river-bank, where the lime-rock should be intact, shows that it has been extensively disrupted and its débris, often coarse and water-worn, in pieces from four to ten feet long, is mixed with the coarse bowlders, gravel and the drift, at the height of fifty to seventy-five feet above the water-level, the heterogeneous mass lying on the worn upper surface of the St. Peter sandstone. But above Fort Snelling the upper edge of the lime-rock is intact all the way to the falls, and shows a fresh-cut section. It is surmounted by a continuous sheet of drift, which rises from the water-level in one bluff coincident with the rock-cut. Its individual strata show that they were cut by the recession of the falls in the same manner as the strata of the rock. They do not conform in their undulations to the outline of the rock, as if the gorge were present when they were formed, as at St. Paul. There is no spreading of loam over these cut edges, except such as has fallen down from above at the time of their removal or subsequent to it. At Fort Snelling, the direction of the Mis- sissipp1 changes abruptly at a right angle. The change is caused by entering the wide gorge which runs in that direc- tion. This gorge is that in which the Minnesota runs, and is out of proportion with the amount of water which it carries. This valley continues in the same direction, and with the same width, beyond the confluence of the Mississippi, but takes the name of the latter stream. At one mile below the mouth of the Minnesota it isa mile and a half wide. These features of greater age, pertaining to the bluffs of the Mississippi below Fort Snelling, are seen in the old rock- bluffs of the river above the mouth of Bassett’s Creek as far as to Shingle Creek. The rock there is deeply changed in color, and is hid by the drift, and the bluffs, as left by the more an- cient river, are far apart, the old gorge being three or four times as wide as that between the falls and Fort Snelling. These rock-bluffs, consisting of the same limestone as that which at the falls is below the water, here rise from thirty to forty feet above the river, and are buried under loam, or under drift and loam. This part of the old valley continues south-. wardly, by way of Bassett’s Creek (below its last turn), across the western suburbs of Minneapolis, through the valleys occu- THE DAT# OF THE GLACIAL PERIOD. 555 pied by Lakes Calhoun and Harriet, and joins the Minnesota at some point above Fort Snelling, the precise locality being “FALLS IN 1830 H\ FALLS IN 1680 —s 4 %, 4% = Zz if RY aut Re se ae a, — a 1 ty T = = A = S =— = ~ LTS" Fie. 142_—Map of Mississippi River from Fort Snelling to Minneapolis and the vicinity, showing the extent of the recession of the Falls of St. Anthony since the great Ice age. Notice the greater breadth of the valley of the Minnesota River as described in the text. hid by a subsequent deposit of drift. It was cut down into the St. Peter sandstone over one hundred feet at least, as shown by the well at the Sumner school-house, and about two 556 THE ICH AGE IN NORTH AMERICA. hundred and seventy-five feet, as shown by the deep well at the Lakewood Cemetery. ‘This would show that probably the an- cient valley of the Minnesota where it passes Fort Snelling, and all the way through Ramsey county and below, has been filled more than two hundred feet by drift that originated since the excavation of the gorge. ‘This supposition is borne out by all borings that have been made between the rock-bluffs at lower points, as at West St. Paul and at Lake City. Such excavation is not found in the river-gorge between Fort Snuel- ling and the Falls of St. Anthony ; but, below the water, are found, first, some large fragments of limestone, and some bowl- ders of foreign origin, the whole being generally less than twenty-five feet in thickness, and below that the undisturbed St. Peter sand-rock is found, suitable for the foundation of piers for bridges. These facts warrant the conclusion that that part of the Mississippi gorge above Fort Snelling has been excavated by the recession of the falls since the last general drift movement, and that prior to that event there was a gorge which passed from the present channel of the Mississippi at the mouth of Bassett’s Creek southward to the great gorge of the Minnesota at some place above Fort Snelling. It is probable that this gorge was then occupied by waters that drained from the northern part of the State, and had existed through many ages, dating back to pre-Cretaceous times. It seems to have been filled first by a blue till, or partly filled, and to have remained free for the passage of the Mississippi during the on-coming of the Glacial epoch, till the advent of the ice of the last Glacial epoch, when morainic accumulations so choked it that the water of the river was driven out and compelled to seek an- other passage to the Minnesota. When this last event took place, the Falls of St. Anthony probably began at Fort Snel- ling, the water being precipitated over the rock-bluff of the pre-existing old gorge, unless the whole valley was too deeply buried under water. Whether this was at the beginning or at the acme of cold, or at the recession of the ice, is a question which may well be considered, but at this time the only point that is claimed is that it was not earlier than the beginning of the last Glacial epoch, and was probably near the acme of cold. THE DATE OF THE GLACIAL PERIOD. 057 Having thus established the post-glacial origin of the gorge below the Falls of St. Anthony, the next point was to determine the rate at which the recession has been proceed- ing. Fortunately, upon this point an abundance of evidence is available. The falls were first visited and described as early as 1680 by the Jesuit missionary Hennepin. His de- scription is found in the Amsterdam edition of his works, printed in 1704. The falls were again visited in 1766, eigh- ty-six years later, by Carver, another Jesuit missionary. In addition to his description this traveler made a sketch of the falls, which was engraved to accompany his travels, published in London in 1778. Subsequent travelers who describe it are Major Z. M. Pike, in 1805; Major Stephen S. Long, in 1817; Schooleraft, in 1820; Professor William Keating and Mr. Beltrami, Rev. W. T. Boutwell and Schooleraft, in 1832; and Mr. G. W. Featherstonhaugh, in 1835. In addition vari- ous artists have gathered descriptions of the falls as they ap- peared in 1842, 1848, 1853, and in 1857, and daguerreotypes were taken in 1851; while in 1853, before the erection of saw- mills, Mr. J. W. Bond gave a careful description of the falls as they then existed, and numerous living witnesses fix their position in 1856, when artificial changes were introduced, which so modified the rate of recession as to disturb further calculation. The period, then, during which evidence is avail- able for caleulation is that between Hennepin’s visit in 1680 and the year 1856—one hundred and seventy-six years. The descriptions are so minute that Professor Winchell is able to fix beyond doubt the various stages of recession between these dates. In 1680 the falls were near the south end of Hennepin and Spirit Islands, not far above the present Tenth Ave- nue Bridge. In 1766, at the time of Carver’s visit, the falls had receded about four hundred and twelve feet, and were at Carver’s Island. In 1856 the west falls were about tive hun- dred feet below their present position, which is now made sta- tionary by artificial means. According to Professor Winchell, the recession from 1680 to 1766, between Ilennepin and 558 THE ICH AGE IN NORTH AMERICA. Carver, was four hundred and twelve feet ; and between 1766 and 1856, six hundred feet, making a total between 1680 and 1856, of one thousand and eighteen feet. ‘These give re- spectively the rates 4°79, 6°73, and 5:08 feet per year, and for the corresponding periods necessary for the recession of the falls from Fort Snelling (a distance of a trifle over eight miles) 8,819 years, 6,276 years, and 8,315 years. The aver- age of these three results is 7,803 years.” Professor Winchell then proceeds to discuss the possible elements of error in this calculation : 1. That arising from difference in the volume of the river. The terraces already described in the chapter on “ Preglacial Drainage,” as characterizing both the Minnesota River and the upper Mississippi, reveal the existence of _ enormous floods during the closing stages of the Glacial pe- riod. Indeed, these floods in the Minnesota River were so high as to fill it up to the level of the lime-rock at Fort Snel- ling, about one hundred feet. During the existence of this high water, therefore, there could have been no cataract at Fort Snelling or farther up the Mississippi. The Falls of St. Anthony could have begun only after the floods of the Minnesota began to shrink so as to uncover the lime-rock at Fort Snelling. 2. Difference in the height of the falls at various points from Fort Snelling up to its present position. Thisis shown to be comparatively insignificant, so that it can be left out of the account. 3. The stage of the Glacial period when the recession began. Upon this we quote again at length : This point has already been considered in the possible va- riations in the volume of the river. It is probable that the Mississippi, in diminutive form, began to flow in its new channel at the acme of the cold,* since the moraine of the sec- ond Glacial epoch runs across the country, approximately through this region, and since it would have remained in its * See map of Minnesota in next chapter (Fig 181). THE DATE OF THE GLACIAL PERIOD. 599 preglacial channel till it was driven out by the encroaching moraine. It was the easier removed from its old channel by reason of its reduction in volume. When it began its course in its new channel, it flowed over a broad plain of gravel and sand, the then latest accumulations of glacial torrents. This plain of gravel and sand extended throughout the adjoining space now occupied by such drift deposits. The same kind of deposits filled the whole Minnesota Valley, from side to side, and rose as high as the plains back of Fort Snelling. The river, being comparatively small, had but little effect on these deposits. If it excavated any channel, the torrents from the ever-present glacier-ice filled them at once—indeed, 2 exca- vated, i¢ refilled, as 7¢ was glacier-born.. It was on the retire- ment of ice, bringing a greater drainage area into contribution to swell the main streams at this latitude, that these rivers began to deposit the fine loam-sand which covers the coarse gravel and sand of these terraces. It was still later, when the rivers were shrunk, by the partial or complete with- drawal of the glaciers from their remote sources, that they began to excavate through the loam and the gravel and sand and finally entered on the slow erosion of rock-gorges. Thus it appears that the date from which the recession of the falls must be reckoned was after the outlet of Lake Agassiz had been opened toward the north, one of the last acts of the Ice age. .. . Finally, if all the supposed irregularities be allowed their full force, and all the elements of doubt be admitted, their combined effect would not, at the most, more than slightly modify the result. And even if it should double the first result, or should reduce it to one half, the chief value of the calcula- tion is not impaired. That consists in showing the lateness of the last Glacial epoch compared with the enormous time that has sometimes been supposed to have elapsed since its de- parture. If the occurrence of our winter in aphelion, caused by the precession of the equinoxes and the revolution of the line of the apsides, about eleven thousand three hundred years ago, was the cause of our last Glacial period, it follows that it re- quired about thirty-five hundred years for the withdrawal 560 THE ICH AGE IN NORTH AMERICA. of the ice-margin from the vicinity of Fort Snelling to that place where the discharge of Lake Agassiz was operied to- ward the north, reducing the Minnesota to nearly its present size. This change must have given prominence and erosive effect to the waterfall at Fort Snelling, if it did not give it birth. These calculations concerning the age of Niagara and the Falls of St. Anthony are amply sustained by the study of various minor waterfalls and gorges in Ohio to which I have myself given special attention. For example, at Elyria, twenty-five miles west of Cleveland, Black River plunges over the outcropping Waverly sandstone, and flows onward to the lake through a wide valley in the Erie shale, which was doubtless preglacial, though no buried channel above has yet been discovered. The gorge below the falls, which has been eroded since glacial times, and which approximately represents the work done by Black River during that time, is only a trifle over two thousand feet long. The water flowing over the falls represents the drainage of about four hundred square miles, and the sandstone which forms the precipice over which the water plunges is underlaid by soft shale very favorable to rapid erosion. In March, 1871, a mass of rock fell which was so large that the concussion shook the whole town and produced the semblance of an earthquake. With the present forces in operation at this point, it would seem incredible that the average rate of re- cession should not be considerably more than one foot in fifty years. Yet thus infinitesimal would be the rate if one hundred thousand years must be allowed for the time separat- ing us from the birth of the present waterfall at Elyria. The shortness of this and other similar gorges in that region points to a great reduction of the prevalent estimates of glacial chronology. Another interesting confirmation of this moderate esti- mate is to be found in Paint Creek Valley, in the southern part of Ohio, to which attention was directed in a previous chapter. As was discovered by Professor Orton several years _— — THE DATE OF THE GLACIAL PERIOD. 561 ago, this stream, a few miles above its junction with the Scioto, at Chillicothe, abandoned its preglacial valley in a most singular manner.* The preglacial valley of Paint Creek for about twenty miles above its junction with the Scioto runs in a northeast direction from the town of Bain- bridge. The valley is nearly a mile wide at the bottom, and about five hundred feet below the general level. But the pres- ent stream, after it has abandoned this old valley, occupies for two or three miles a narrow gorge not over five hundred feet wide, cutting directly through the table-land, and re- entering the old valley considerably lower down in its course. The only satisfactory explanation of this is found in a study of the local glacial phenomena. The lower or northeastern part of this preglacial valley is exactly on the line of the gla- cial boundary, and was for a certain period obstructed by the most advanced portions of the glacier, which dammed up the water and raised it to a level at which it would be forced in front of the ice across a tongue of the table-land, thus eroding the present channel.+ This portion of the channel, as already indicated, is about three miies long, from three hundred to five hundred feet deep, five hundred feet wide at the top, and two hun- dred at the bottom. The walls near the top consist of fifty or sixty feet of Waverly sandstone, while all below is a soft shale crumbling very readily. The question in glacial chro- nology is to find the age of this gorge, which is clearly post- glacial. The true solution of the problem comes from a study of one of the lateral gorges formed by a small tributary entering the main gorge midway from the south. This tributary, though dry a portion of the year, is at other times a raging torrent, and drains an area of two or three square miles. Yet in the soft shale, so favorable for rapid erosion, it has worn a gorge less than six hundred feet long, but hav- ing a mouth of nearly the same width where it joins the * “ Geological Survey of Ohio,” vol. ii, p. 653. + See map, p. 373. 562 THE ICE AGE IN NORTH AMERICA. main channel. It can scarcely be possible that these forces have been in operation in their present position for many thousand years; for, ac- cording to the testin.uny of Mr. Long, who has been a resident upon the ground for fifty years, and has definite data for calculation, this tributary creek has worn back sev- eral feet since his re- membrance. If the rate of recession for this trib- utary gorge were as little as one foot in twenty years, only twelve thou- sand years would be re- plishment of the work Fig. 143.—ldeal view of an old unglaciated coun- try, showing the form assumed by the emi- done. If we should go nences when erosion has proceeded to a great ° extent. (United States Geological Survey.) back to the period as- any be signed by Mr. Croll’s the- ory to find the Glacial period, the rate of recession would be incredibly slow, and far below what is pretty certainly the rate at the present time. An extreme length was at one time given to the intergla- cial episodes by attributing to interglacial time much erosion that was preglacial. For example Professor Chamberlin in his early publications regarded the gorge of the Ohio and the Allegheny as well as those of the Delaware and the Lehigh as the work of interglacial erosion. If this were the case, the interglacial episodes must have been of enormous extent, for these are rock gorges ot great length and 200 or 300 feet in depth. Subsequent investigations, however, showed that the most of this erosion was preglacial rather than interglacial. At Warren, Pennsylvania, on the Allegheny River, as already * quired for the accom- . edn snk, aa = ~~ 2g ede i ai THE DATE OF THE GLACIAL PERIOD. 563 detailed, the upper gravel terraces which Professor Chamber- lin had separated from the lower ones by this enormous interval, were found to be continuous, showing that they belonged to the same period, while deeply buried gorges filled with glacial débris of Kansan age opened into the main channel from the south. As already remarked, also, the high- level terraces of the Monongahela were not, as Professor Chamberlin maintained, ordinary river flood-plains, but eZ 77 = Z = sae oak shore lines of a glacial Fie. 144—A country, in contrast with that on the opposite page, in which the drainage has been lake produced by dam- disturbed by glacial deposits and the streams are ming upo Se eoutlel this beginning to wear new channels. (Chamberlin.) Lake Erie, by way of the Mahoning and Grand River valleys. The most, therefore, that can be made of the interglacial time from the erosion of the Ohio River gorge is that needed for the wearing down of the cols between the branches of the various streams that were flowing north and were dammed up by the advancing ice-sheet. As already shown it was the junction of these upper branches which formed the present tortuous channel of the Ohio River. The gorge of the Dela- ware was proven to be preglacial by the investigations of Professor E. H. Williams, which brought to light the fact that at Bethlehem, Pa., the present Lehigh River flows over a bed of glacial débris filing an old channel which is 120 feet deep, and this in a region reached only by the very earliest ice invasion. The rock gorge of the Delaware into which the Lehigh empties must, therefore, be wholly preglacial. 564 THE ICE AGE IN NORTH AMERICA. Another most instructive illustration of the extent of preglacial erosion is found west of Keokuk, Iowa,* where there isa buried channel of great width now filled with glacial débris while the river at Keokuk flows over a rock bottom and through a comparatively narrow channel. ' | ty 1 ral a re) “J \ | | ! | ! ' | S 2 CCAR = ae Fic. 146—Cross section of the new course of Plum Creek, showing its original width and its enlargement in twelve years. Another means of measuring thhe amount of erosion since the Glacial period is found in post-glacial river-valleys by estimating the amount of material which has been car- ried out by the present streams from the glacial deposit itself. Professor Hicks, of Granville, Ohio, reported in 1884,7 some important results of such an investigation in the valley of Raccoon Creek, Licking county, near the glacial border. Thi present flood plain of this creek is now bordered on either side by gravel terraces about fifty feet high, which are *See cut on page 310. + ‘Baptist Quarterly’’ for July, 1884. See also Fig. 99, p. 324. awed THE DATE OF THE GLACIAL PERIOD. 565 evidently the remains of a modified glacial deposit formerly filling the whole valley to that height. Since the Glacial period the present stream has been occupied with the task of slowly removing this material. The number of cubie yards which it has already carried away can be approximately esti- mated. The rate of removal is more difficult to determine. Assuming the rate to be the same per cubic foot of water as that which is transported by the Mississippi River past New Orleans, which doubtless is far too small, the time required would be, according to the calculation of Professor Hicks, less than fifteen thousand years. I have been able to make a more definite calculation in connection with Plum Creek, in Oberlin, Ohio. The situa- tion is peculiarly favorable both on account of its relation to the glacial shore lines around Lake Erie, and of its freedom from disturbing obstacles. The section of the Creek Valley from which the facts are gathered lies ten miles south of the present shore of Lake Erie, and 250 feet above the lake level. It is about five miles south of the highest of the lake ridges, and fifty feet higher than the upper ridge. Its course is _ wholly in glacial till with no rock bottom anywhere in its course. The average gradient of the stream is twelve feet to the mile, falling 100 feet in eight miles. It is evident that the stream did not begin the erosion of its present trough until the ice-sheet had retreated from the water-shed on the south and had uncovered the outlet of the glacial lake at Fort Wayne, which determined the level of water on whose shores the upper ridge was thrown up by the waves. The Plum Creek trough is therefore older than the Niagara gorge by the length of time that was required for the retreat of the ice-sheet from the south shore of Lake Erietothe Adirondack Mountains, a distance of 200 or 300 miles; for, asalready said, Niagara did not begin its work until the Mohawk Valley, south of the Adirondack Mountains was free from ice. Now, in 1895, a reservoir was constructed in the village occupying the whole width of the trough of the creek, and 566 THE ICE AGE IN NORTH AMERICA. compelling the engineers to open a new channel across an undisturbed neck of the original glacial till. The section of this chosen for observation was 500 feet long, and at first consisted of a ditch twenty-one feet wide at the top, and ten at the bottom, with an average depth of eleven feet, though on the south side it rose to a height of twenty feet above the bottom. But, after a lapse of twelve years (in 1907), the stream had enlarged the ditch to a width of fifty- one feet at the top, andof seventeen feet at the bottom, giving an average width of thirty-four feet compared with the original of fifteen and one-half feet. A simple mathematical calcula- tion shows, therefore, that in twelve years this stream had removed from a 500-foot section whose banks were exposed to the direct action of the current on both sides, 101,750 cubic feet of solid matter, or, 8,450 cubic feet per annum. To get a more perfect basis of comparison, measurements were taken of a section 5,000 feet long below the village, where the original conditions had been undisturbed. In this sec- tion the eroded trough averaged 400 feet in width and seven- teen feet in depth, and this entirely in glacial till such as characterizes the whole valley. The total amount, therefore, of work accomplished, by the stream in this section since the present line of drainage was opened was the removal of 34,000,000 cubic feet of till. To obtain a still more approximate basis for calculation it was necessary to measure the length of the sections of the edge of the trough whcre the stream impinges directly against the bluff and so is eroding under conditions similar to those in the cut-off at the reservoir. Upon doing this it was found that these exposed sections amounted to 1,600 feet in length, which is 600 feet more than that of both sides of the cut-off. The annual erosion, therefore, in the 5,000-foot section is now one and six-tenths greater than in the cut-off, making 13,568 cubic feet of material per year. At this rate the 34,000,000 feet of material from the 5,000-foot section THE DATE QF THE GLACIAL PERIOD. 567 would be removed in 2,505 years; a result so incredible that we are called to examine more closely into the various con- ditions affecting the problem, some of which would tend to retard the eroding action of the stream, and some to accel- erate it. Of the retarding influences the most conspicuous is the former existence of a dense forest of large trees covering the whole basin. It is scarcely possible, however, that the rate would be reduced from this cause lower than to one-tenth of that of the present time, which, if there were no counteract- ing causes, would extend the time to 25,000 years. But, on the other hand, it is evident that the rate of erosion in the main trough is, at its present width, at a minimum. For, as the width of the trough has enlarged, it has taken the stream a longer and longer time to swing from side to side in its meanderings. At the outset the stream acted through the entire length on both sides as it now does in the cut-off, and when the width of the trough was half what it is now, the erosion was twice as fast. It is safe to say, therefore, that the average rate during the forested condition would be twice what we have allowed. This would reduce the time to 12,500 years, which cannot be far from a correct estimate. For, in addition to the early constriction of the channel in increasing the rate, it should be kept in mind that on the first withdrawal of the ice there was no forest to retard the action of the stream. Further- more, it is altogether probable that there was a much greater precipitation over the basin of the creek while the ice lingered over the area immediately to the northward, and this would increase the rate of erosion. It has been necessary to enter thus fully into details con- cerning one instance in order to get the force of the cumula- tive argument from the innumerable similar instances which present themselves all over the area in which the natural drainage is towards the front of the ice-sheet. Present 568 THE ICE AGE IN NORTH AMERICA. eroding forces cannot have been at work over this region for much more than 10,000 years, and this is some time previous to the beginning of the work of the present Niagara River. Another class of facts which seems to set moderate limits to glacial chronology relates to the amount of superficial ero- sion of glacial deposits of various sorts, and the extent to which the rocks have been disintegrated since that period. President T. C. Chamberlin, when State geologist of Wisconsin, remarked that no sensible denudation had taken place there since glacial times.* Even Mr. Croll expresses surprise at the small amount of erosion which has taken place since the kames of Scotland were deposited. Both in Europe and in America these peculiar relics of the Glacial period retain a sharpness of outline which it is difficult to be- lieve could have survived the protracted period of one hun- dred thousand or even of forty thousand years, according to Hitchcock’s reckoning. When, also, one considers the chemi- cal agencies at work to decompose the rocks wherever un- protected by a covering of till, the freshness of the glaciated surfaces never ceases to be a cause of astonishment. Dr. Geo. F. Becker, of the United States Geological Sur- vey, bears striking testimony to the freshness of the glaciated surfaces of the rocks in the mountains of California on the Pacific Coast. He writes: “No one, who has examined the glaciated regions of ‘the Sierra can doubt that the great mass of the ice disappeared at a very recent period. The immense areas of polished surfaces fully exposed to the severe climate of say from 7,000 to 12,000 feet altitude, the insensible erosion of streams running over glaciated rocks, and the freshness of erratic bowlders are sufficient evidence of this. There is also evi- dence that -the glaciation began at no very distant geologic date. As Professor Whitney pointed out, glaciation is the last important geological phenomenon and succeeded the great lava flows. * “Geology of Wisconsin,”’ vol. ii, p. 632. THE DATE OF THE GLACIAL PERIOD. 569 “There is also much evidence thai erosion has been trifling since the commencement of glaciation, excepting under peculiar circumstances, east of the range, for example, at Virginia City; and sites which there is every reason to sup- pose preglacial have scarcely suffered at all from erosion, so that depressions down which water runs at every shower are not yet marked with water-courses, while older rocks, even of tertiary age and close by, are deeply carved. The rainfall at Virginia City is, to be sure, only about ten inches, so that rock would erode only say one-third as fast as on the California coast; but even when full allowance is made for this difference, it is clear that these andesites must be much younger than the commencement of glaciation in the north- eastern portion of the continent as usually estimated. So, too, the andesites near Clear Lake, in California, though beyond a doubt preglacial, have suffered little erosion, and one of the masses, Mount Konocti (or Uncle Sam), has nearly as characteristic a volcanic form as Mount Vesuvius.’’* Dr. Bell} alsowrites as follows: “On Portland promontory, on the east coast of Hudson’s Bay, in latitude 58°, and south- ward, the high, rocky hills are completely glaciated and bare. The strie are as fresh looking as if the ice had left them only yesterday. When the sun bursts upon these hills after they have been wet by the rain, they glitter and shine like the tinned roofs of the city of Montreal.” Again, Pro- fessor Macount writes of the red Laurentian gneiss in the vicinity of Fort Chippewayan, at the west end of Lake Atha- basca: “The rocks around the fort are all smoothed and polished by ice action. When the sun shines they glisten like so much glass, and a person walking upon them is in constant danger of falling.” * “Bulletin of the Geological Society of America,”’ vol. ii, pp. 196, 197. To the same effect see the testimony of Prof. I. C. Russell and Prof. Gilbert, below p. 609. t “Bulletin of the Geological Society of America,’’ vol. i, p. 308. t ““Geological Survey of Canada, Report of Progress,’’ 1875-1876, p. 90. 570 THE ICE AGE IN NORTH AMERICA. “Likewise, concerning the glaciation of Europe, we find that in Wales and in Yorkshire, England, the amount of denudation of limestone rocks on which bowlders lie has been regarded by Mr. Mackintosh* as a proof that a period of not more than six thousand years has elapsed since the bowlders were left in their positions. The vertical extent of this denudation, averaging about six inches, is nearly the same with that observed in the southwest part of the Province of Quebec by Sir William Logan and Dr. Robert Bell, where veins of quartz marked with glacial striae stand out at various heights not exceeding one foot above the weathered surface of the enclosing limestone. As illustrating how little we know about the causes which produce the variations in snow fall, even from year to year, and render it impossible to form trustworthy a priori opinions concerning the proximity of the causes which are capable of producing glacial conditions, Mr. Becker writes that in 1890 the “snowfall in the Sierra was exceptionally large, about two and one-fourth times the average precipitation — having fallen. Much of this snow remained unmelted through the season, and when I left the mountains, on October 1, there were still thousands of snowbanks where in ordinary seasons none remains even far earlier in the season. Many of these banks were also of great depths, say 100 feet, more or less. It is clear, therefore, that were this and succeeding winters to be as wet as the last, the range would show glaciers in great numbers, much as the Alps now do; in short, the glacial period of the Sierra would recur in a moderate way. Now, no one doubts that there was some cause for the unusual snowfall of 1889-90 but no one has any suspicion what it was. No sensible change in cosmical or terrestrial condi- tions has occurred, the weather of the world at large was not remarkable, and, excepting as to precipitation, the year was not extraordinary even in California.” * “Quarterly Journal of the Geological Society,’’ vol. xxxix, pp. 67-69; vol. xlii, pp. 527-539. THE DATE OF THE GLACIAL PERIOD. 571 Again evidence comes from the extent to which lakes, dating from the Glacial period, have been filled with sedi- ment. Little reflection is required to make it evident that our present lake-basins could not always have existed; for, except where counteracting agencies are at work, the “ wash” of the hills will, in due time, fill to the brim all inclosed areas of depression. Mr. Upham, of the Minnesota Geo- logical Survey, expresses surprise at the small extent to which the numerous lakes of that State have been filled with the sediment continually washing into them. “The lapse of time since the Ice age has been insufficient for rains and streams to fill these basins with sediment, or to cut out- lets low enough to drain them, though in many instances we can see such changes slowly going forward.” * Dr. E. Andrews, of Chicago, has made calculations, de- serving of more attention than they have had, concerning the rate at which the waters of Lake Michigan are eating into the shores, and washing the sediment into deeper water or toward the southern end of the lake.t The United States Coast Survey have carefully sounded the lake in all its parts, and have ascertained the width of the area of shallow water extending inward from the shores. It is well known that waves are limited in their downward action, so that there will be a surrounding shelf, or shoulder of shallow water, in cases where the waves of a deep lake are eroding its banks. This fringe of shallow water encircling Lake Michigan is only a few miles wide; and from such data as have been gath- ered, the average rate of erosion is found to be as much as five or six feet per annum; which would indicate that the lake-basins had not been in existence more than seventy-five hundred years. Leaving these more indefinite and in many respects un- satisfactory efforts to estimate the age of lake-basins, we may get some assistance in approximating to a correct chro- * “ Minnesota Geological Report” for 1879, p. 73. + “American Journal of Science,” vol. xeviii, 1869, pp. 172 et seg. 572 THE ICE AGE IN NORTH AMERICA. nology of the Glacial age by studying the smaller kettle-holes | which constitute so marked a feature in the kames and moraines of the glaciated region. As already shown, the most satisfactory explanation of these curious depressions is, that they mark places where masses of ice were buried in the débris of sand and gravel brought down by the streams of the decaying glacier ; and where, upon the melting of the buried ice, a cone-shaped depression was left with sides as steeply inclined as the nature of the soil would permit. At any rate, there can be no question that the kettle-holes were formed during the closing stages of the Glacial period. As typical of numberless others we present the facts concerning a kettle-hole near Pomp’s Pond in Andover, Mass.* Pomp’s Pond is itself a moraine basin about a quarter of a ile in diameter, and but slightly above the level of the Shaw- shin River, into which it empties. Upon its north side is an accumulation of gravel and sand, with pebbles intermingled, in which there are several of the smaller characteristic bowl- shaped depressions of which we have spoken. Their appear- ance is much like that of volcanic craters. You ascend a sharp acclivity from every side toarim of gravel, and then descend as rapidly into the bowl-shaped or crater-like depres- sion.. A section carried across will present the idea. Ve. 147,— Section of kettle-hole near Pomp’s Pond. Andover, Massachusetts. (See sie (For general view of the situation, see Fig. 101, p. 338). From the level of the pond, and two or three rods from the edge, you begin to ascend at an average rate of about one foot in three, till the south side of the rim is reached, at a height of fifty-two and five tenths feet above the pond. (a) (This rim is not, however, of a uniform height. On the east side it rises * T here transfer a few paragraphs from my “Studies in Science and Re- ligion.”’ i i ~ THE DATE OF THE GLACIAL PHRIOD, 573 into a pyramid seventy-seven feet high.) (0) Then, descending fifty and five tenths feet vertically, you are carried one hundred and thirty-eight feet horizontally, reaching at that point the edge of a circular mass of peat which is ninety-six feet in di- ameter. (c) From the opposite side the ascent of the northern rim begins, and you descend from its top to the valley, repeat- ing almost exactly the first descent from the pond. The dis- tance from rim to rim, or the diameter is three hundred and eighty feet. 3 It is evident that since the first formation of this crater- shaped depression no material can have reached the bottom, except from three sources: 1. The wash from the side ; 2. The decay of vegetation which grew within the circumference of the rim; 3. The material brought by the winds. It is equally evident that what is once in can not get out. Dust, leaves, and twigs carried by the winds inevitably lodge in such depressions more thickly than in other places, since the atmosphere in such hollows is comparatively quiet. For the same reason the surrounding trees as they are blown down are more likely to fall toward the center of the kettle- hole ; and the ashy material which their roots abstract from the sides of the depression is no insignificant factor in the problem. Now, from the angle of the declivity, the original depth of the depression can be approximately estimated. If the angle be still the same as at first, the first three terms of the propor- tion would be 138 : 50°5 :: 48 : 1743, making the original depth below the present surface of the peat a trifle over 17°5 feet. If, however, we suppose the original slant to have been steeper and the rim higher, we can still see that there must have been a limit to the depth. Suppose the rim to have been one third higher and the slant one third steeper, we then should have in round numbers the proportion 138 : 68 :: 48: 2345, making the original depth of the depression nearly twenty-four feet below the present surface of the peat. From the nature of the material it is impossible that the depth could originally have much exceeded that amount. Accepting this conclusion, the problem is, to determine the time it would require the agencies mentioned above to fill the o¢4 THE IGE AGE IN NORTH AMERICA. bottom of this bowl to a depth of twenty-four feet—a cone ninety-six feet in diameter at the base and twenty-four feet to the apex—which would be equal to a deposit of only eight feet over the present surface of the bottom. ‘The question is, Could this have stood with so little change for eighty thousand years ; or even for forty thousand years, if we were to accept Professor Charles H. Hitchcock’s estimate of the prolongation of the effects of Croll’s period ?* Is not the supposition of ten thousand years sufficiently extravagant ? If the close of the great Glacial period be so far back as Mr. Croll estimates, we must believe that sediment would accumulate, in the situ- ation above described, over the surface of the present peat-bog, at the rate of only one inch in a thousand years; while, if we put the close of this period back ten thousand years, the rate of accumulation would seem to be as slow as our imagina- tion can well comprehend. One hundred inches, which is little more than eight feet, divided into one hundred thousand parts, would be only :001 of an inch; that is, if this depression has been in existence one hundred thousand years, we must believe that with all the dust there is in the air, and all the soil that would wash down the steep incline of all the sides, and all the vegetable matter growing in and falling into the depression, one thousand years would be required for one inch of sediment to accumulate! If we reduce this supposed period to 50,000, 25,000, and 12,500 years successively, the time re- quired for the accumulation of an inch of sediment would be proportionally 500, 250, and 125 years. If any one will be at the trouble of dividing an inch into 125 equal parts, he will probably be surprised at the insignificance of the quantity. The slowest rate at which Boucher de Perthes calculates for the accumulation of peat over Roman pottery in the valley of the Somme is three centimetres, or a little over an inch, in a century. We do not bring railing accusation against those who, from astronomical considerations, confidently speak of the close of the Glacial period as an event which occurred scores of thou- sands of years ago; but it is important to know what other * “Geology of New Hampshire,” vol. iii, p. 327. ., = THE DATE OF THE GLACIAL PERIOD. 57 Or beliefs that long chronology carries with it. If any one chooses to believe that kettle-holes can stand one hundred thousand years, and fill up only twenty-four feet from the apex of the inverted cone, he must run the risk of bene considered credulous. Inrejectingthe theory of Mr. Croll concerning an indefinite succession of glacial periods, we did not mean to foreclose the discussion connecting the question whether there have not been several Pleistocene glacial epochs. This question must, therefore, now be considered with more particular reference to its bearing upon matters of chronology. As the reader doubtless observed in the remarks upon Croll’s theory, quoted from Mr. Gilbert and President Chamber- lin, in the preceding chapter, each of them spoke of an ‘‘In- terglacial Period’ as clearly indicated in North American geology. The calculations just made relate to the chronology of what President Chamberlin called the “second glacial epoch.” Niagara Falls, the Falls of St. Anthony, the kettle- holes of Massachusetts, and the valley of Plum Creek, are none of them upon the extreme border of the glaciated region. Raccoon Creek is nearer the margin. Calculations respecting those interior points, therefore, do not give the date of the extreme marginal deposits. Hence it becomes a matter of prime importance to consider to what extent the ice retreated during the various climatic episodes which characterized the epoch. Many, perhaps most, of the authorities on glacial subjects at the present time ho!d that during two or three of these episodes the ice retreated as far as the Laurentian Highlands and then re-advanced to the limits of what are called respectively, the Iowan, the Ilinoisan and the Wisconsin boundaries of glacial drift. It is necessary, therefore, to discuss these questions in con- siderable detail. The most obvious evidence adduced in favor of inter- glacial epochs in America consists of the so-called ‘inter- 076 THE ICE AGE IN NORTH AMERICA, glacial” forest-beds.* These forest-beds and vegetal de- posits occur over a wide area, and in places have glacial de- posits both under them and over them. The first supposi- tion with regard to them was that these various forest-beds were contemporaneous, and indicated a general retreat of - the ice after its first invasion of North America until it had entirely disappeared or lingered only in the Canadian high- lands; whereupon there was a readvance of the ice, over- whelming the forests and other vegetal deposits which had collected in kettle-holes and other depressions, and burying them beneath a second sheet of ground-moraine, where they. are opened to present inspection whenever wells penetrate them or eroding streams expose them on their banks. But it is not clear that these interglacial forest-beds might not originate in front of the margin of the slowly retreating ice if only there were comparatively brief periods of readvance along successive lines of latitude. Thus they may belong to various times of oscillation, both during the general advance and during the general retreat of the glacier. If, for ex- ample, at any time during the period of advance there had been a retrocession of the ice-front for a short distance, for- ests and vegetable growth would soon have spread over the marginal belt from which the ice had retreated, and, upon a readvance, these would be overwhelmed and covered with a new stratum of glacial deposition. In case of some of the peat-beds, it is probably necessary to suppose that they were formed where they are, and are really interglacial ; but, in case of many of the fragments and logs of wood found in the glacial deposit, we are not compelled to suppose an interglacial origin. Wood will stand transportation in the ground-moraine almost as well as bowlders, and it is by no means certain that much of the timber found in the till may * See Chamberlin, “ Geology of Wisconsin,” vol. i, chap. xv, especially pp. 271-291; “ Driftless Area,” pp. 211-216; N. H. Winchell in “‘ Proceedings of the American Association for the Advancement of Science,” vol. xxiv, 1875, pp. B, 438-56; “Geology of Minnesota,’ vol. i of the ‘‘ Final Report,” pp. 363 et seqg.; J.S. Newberry, “ Geological Survey of Ohio,” vol. ii, pp. 30-33. Fic. 148.—Perpendicular section of till at Oxford, Ohio, showing a piece of wood three inches in diameter projecting from the face. This has evidently been transported in the till like a bowlder. The section is about fifty feet ; portion shown, about fifteen feet, near the middle. (United States Geological Survey.) (Wright.) 578 THE ICE AGE IN NORTH AMERICA. not have belonged to the original forests which covered the country in front of the first sheet of advancing ice. These logs may have been picked up like the bowlders, and trans- ferred to the south a long time after their original deposi- tion. Thus, it may be that the “forest-beds” near the mar- gin of the glaciated area are of more recent origin than those some distance back, since the ice in its final retreat may have proceeded with few and slight oscillations. As Presi- dent Chamberlin suggests, also, “ certain subaqueous deposits so closely resembled true till that they have been mistaken for it, and there is perhaps no case of superposition of beds supposed to represent two glacial periods that is not still open to these doubts.” * President Chamberlin, whose knowledge of the facts bearing on this subject is wider than that of any one else, therefore does not rely so much upon the existence of in- closed forest-beds and a supposed superposition of distinet beds of glacial débrzs, in proof of distinct glacial epochs, as upon certain other considerations of a more general nature, such as the following : The earlier drift is characterized, in the interior basin, by a wide but relatively uniform distribution, manifesting only occasional and feeble tendencies to aggregation in mo- rainic ridges. It is not bordered, except in rare instances, by a definite terminal moraine, but ends in an attenuated border. It is not characterized by the prevalence of prominent drum- lins or other similarly ridged aggregations. The phenomena of glacial erosion connected with it are generally feeble. Glacial striz are indeed present, even in the peripheral portions, but the surface of the rock is not usually extensively planed. The whole aspect of the deposit indicates an agency which spread the drift over the surface smoothly, and relatively gently, with little forceful action. The drainage phenomena are also of the gentle order. We have yet failed to find evidence of very vigorous drainage connected with the older drift of the in- * See “Geology of Wisconsin,” vol. i, p. 272. THE DATE OF THE GLACIAL PERIOD. 579 terior basin except in osars and kames, whose conditions of formation were exceptional, but, on the contrary, abundant proof of slow-moving waters and imperfect drainage, indicat- ing low slope of the surface. | The later Glacial epoch, on the contrary, was character- ized by strong glacial action, planing the rock-surface vigor- ously, even up to the very limit of its advance. The glaciers plowed up immense moraines about their edges, except on smooth plains whose slope was away from the ice-movement. The drainage was usually vigorous, and immense trains of glacial gravel stretch away from the margin of the ice-sheet, reaching great distances down the valleys and frequently filling them to great depths with well-assorted material. The vigorous action of the glaciers of the second epoch and the rapid drain- age, in general, stand in marked contrast with the gentle action and imperfect drainage of the earlier epoch. One of the conditions that determined the distinction was probably the difference in elevation that characterized the two epochs. The interval between these two leading epochs we regard as the chief interglacial epoch, representing a greater lapse of time and a greater change in the dynamic agencies of the age than the several other interglacial intervals, or episodes of deglaciation, which mark the complicated history of the Ice age. As belonging to the earlier Glacial epoch, we recognize two drift-sheets that have been described by the geologists of the re- spective States as occurring in southwestern Ohio, southern In- diana, central and southern Illinois, eastern and southern Iowa, northern Missouri, eastern Nebraska; and southeastern Min- nesota. Between these occur, at numerous points, vegetal and fer- ruginous accumulations and other evidences of a non-glacial interval. To this horizon belong the larger number of de- posits described under the term ‘‘ old forest-bed,” but very many vegetal deposits so referred do not, in our judgment, belong there, but are referable to several distinct horizons. * Others adduce as evidence of the distinct Glacial epochs in North America the greater oxidization and general de- * “ Driftless Area,” pp. 214, 215. 080 THE ICE AGE IN NORTH AMERICA. composition of the material upon the extreme border of the glaciated region as compared with that of the kettle-moraine in Wisconsin, and what is considered to be a moraine of corre- sponding age in the regions both east and west. A striking evidence of the reality of this difference in oxidization is related by Professor Penck. When Mr. Frank Leverett was visiting him in Germany the two went out together into the Alpine fields where Professor Penck had distinguished three well marked stages of glaciation of — increasing amounts of oxidization and erosion. These suc- cessive periods of glacial and interglacial episodes he had named after three streams in the foothills of the Alps in south- ern Germany, where the deposits are typically present; viz., Mindel, Riss and Wiirm.* In every instance Mr. Leverett was able to correlate these with the three divisions which he had made in America; viz., the Kansan, corresponding to the Mindel period; the Illinoisan to the Riss; and the Wiscon- sin to the Wiirm. But he did not recognize the Iowan. All these identifications were made in the field without previous knowledge of Professor Penck’s determinations. But with ~ reference to this evidence it is to be noted: 1. That the more complete oxidization of the glacial débris along the southern border and the greater decomposi- tion of the granitic bowlders and pebbles distributed over this border, are naturally accounted for by the obvious fact that for the most part the material along the southern border, and for some distance back from it, was that which was first picked up by the advancing ice, and was probably already oxidized and partially decomposed by the long-continued action of preglacial agencies when the ice began its removal. Its oxidization, therefore, may not be any true indication of the remoteness of its transportation and deposition. It is evident that every successive period of movement from the north would operate upon lower strata of rock and upon the masses which had been less affected by secular agencies of *See above page 459. THE DATE OF THE GLACIAL PERIOD. 581 decomposition. Thus it is natural that the more northern moraines and glacial deposits, of various kinds, a = fresher than the southern. fen’: : The peculiar facts brought to light concerning the oxidiza- tion of the belt of oldest till, bordering the Wisconsin moraine, in Pennsylvania, are worthy of close attention in this connec- sion. As already noted, Professor Williams found by exten- tive field work that the moraine as marked by Lewis and Wright across Pennsylvania was not the extreme boundary of glacial action, but lay on an average twenty or twenty-five miles back from that boundary. This attenuated border was teferred to by Lewis'and Wright as “the fringe,” but they did not endeavor to ascertain its limit in that state: ‘The deposits over that area would, however, now be correlated without doubt with those of Kansan age in the ‘Mississippi Valley. It is noteworthy, therefore, that the surface outcrops over this attenuated belt (examined inthousandsof places and at all elevationsineastern Pennsylvania up to 650 feet ‘above tide, and under caps of glacial deposits only a few feet thick, that vary from loose gravels to compact clays) are universally fresh and undecomposed, showing that the already oxidized deposit was laid upon a freshly glaciated surface, and that time enough has not since elapsed to decompose or oxidize the gneiss, limestone, and slate rocks to any appreciable extent. A striking illustration of this has already been given in connection with the mammoth coal-beds at Morea, Pa., within one mile of the extreme limit of glaciation, and twenty- five miles south of the moraine of Lewis and Wright (p. 154). Here the surface of the rock is distinctly glaciated, and covered with from six to ten feet of sandy till through which water easily percolates. But the coal is rotted only to the depth of three-fifths of one inch, while immediately south of it, in the unglaciated region, it is rotted to the depth of many feet. 582 THE ICE AGE IN NORTH AMERICA. 2. The till over this attenuated border is a mixture of fresh and oxidized material at all levels, showing that most of the oxidization preceded the glaciation, and that not suffi- cient time has elapsed since for the oxidization of the fresh material picked up by the glacier. This statement is based upon the examination of sections miles in length; when it everywhere appears that there is such a mixture of fresh material with oxidized material that the conclusion is irre- sistible that it was one movement which brought both. For example, in the vicinity of Warren and south of Oil City at an elevation of 380 feet above the Allegheny River numerous pebbles were found, both of sedimentary and of granitic rocks, which had evidently been oxidized nearly to their center before starting on their journey from Canada, but had been planed down on one side so as almost to expose the core on that side, while leaving the oxidized layers undis- turbed on the other. Some of these described were five inches or more in diameter and had been rotted so that only an inch or more of fresh nucleus remained; while in some cases the unoxidized core was exposed through the glacial erosion of one side. These instances were numerous. Mr. Williams informs me that ‘‘one striking peculiarity in those with joint planes through which the water could readily reach the center, was that the relative permeability of the mass from its different sides did not have the slightest influence on the position of the fresh nucleus. It was as often nearer the side whence water could most easily enter than to any other side. This impressed me greatly,” he says, “‘asan indication of the extreme recency of the final shaping as with time the relative porosity of the various sides would tend to bring the re- maining nucleus under the usual law as to position.” I am permitted, also, to use the following extract from Professor William’s unpublished notes, in which he sums up some most significant facts concerning the Kansan advance: “The glaciated outcrops in the east [in Pennsylvania] are THE DATE OF THE GLACIAL PERIOD. 583 solid: those in the west more oxidized and rotten, but the critical condition in the west. as in eastern Pennsylvania is the constant presence and mixture of fresh rolled material. As the age of the mixture is the age of the freshest part, there is finally no difference between the ages of the eastern and western Kansan drift. “The rustiness of the western gravelsshows that they were the rolled and weathered surface fragments picked up by the ice, and modified by its action. With the crystallines which are thoroughly oxidized to their center, we find a few specimens which look on one side like a piece of rusty gravel. The black bisilicates have entirely disappeared, and have left pits and a rusty staining. The feldspar also has kaolinized. In these very old ones, the glaciated sides were never scraped down to the fresh interior, but uniformly show a rusty though solid exterior, quite smooth and firm to the hammer. “By breaking these, we would find that the solid nucleus might be one-eighth of an inch from one side which had been glaciated, and three inches or more from the other side which had remained unglaciated.” I am not aware that adequate attention has been paid to this class of facts over the Iilinoisan and Kansan areas in the Mississippi Valley, but I was much impressed with the fresh- ness of the Canadian bowlders which were found at Tus- cumbia, on the Osage River, in central Missouri, and by the freshness of many of the pebbles in a great gravel-pit at Hol- liday on the Kansas River a few miles above Kansas City to which the railroads have resorted for a long time for ballast and which contains much material from the far north. In this connection it is proper to call special attention to the accumulating evidence going to show that the glacial movement from the Keewatin center was not strictly con- temporaneous with that from the Labradorian center but preceded it by a longer or shorter interval. In the first edition it was suggested that the remarkable re-entrant angle in the glacial border at Salamanca, N. Y., indicated the junction of two ice-movements from widely 584 THE ICE AGE IN NORTH AMERICA. separated centers of accumulation to the northeast and north- west. Positive evidence in support of this was found, as already stated, by Prof. Williams in 1897 in the discovery of a rolled piece of native copper from Lake Superior firmly imbedded in till at East Warren, Pa., forty feet below the surface, showing that the older ice-movement from the north- west invaded the region now coverd with the later deposits from the northeast to the extent of several hundred miles; for, as already shown, northeastern drift extended some dis- tance across the Mississippi at Burlington, Iowa. The most important evidence supposed to indicate the complete retirement of the continental ice-sheet between successive deposits is found near Toronto, Canada. This was first investigated by Dr. G. J. Hinde in 1878, but has since been more thoroughly studied by Professor A. P. Coleman, of Toronto University. Briefly stated the facts are that in the valley of the Don River and at Scarboro Heights near Toronto there is at the base a deposit of till which after having been extensively eroded was covered by sedimentary deposits 150 feet in thickness which had been brought into standing water by the stream to form a delta whose base extended twenty-five or thirty miles along the shore. The lower strata of this delta deposit are thirty-five feet below the present level of the lake, and probably at about the same relative level as when laid down. But the water from some unknown cause rose as the accumulation progressed until it was 150 feet higher than now, when the upper sediments of coarser gravel were depos- ited the water began to fall, and a period of erosion succeeded. This proceeded until at Scarboro a V-shaped channel, one mile wide at the top and 150 feet deep, was worn in the sedimentary deposits, whereupon the ice advanced again and covered the whole with sheets of bowlder clay and assorted drift to a total depth of 200 feet. Here certainly seems to be an interglacial deposit of unusual extent. Nor is the character of the fossil plants and animals included. in the interglacial deposits any less noteworthy. THE DATE OF THE GLACIAL PERIOD. 585 - Both the fauna and the flora of the lower, or Don, beds indi- cate a much warmer climate than those of the upper, or Scar-: boro beds. In the Don beds there are found leaves and wood of maple, elm, ash, hickory, basswood, and even of pawpaw and osage orange which now flourish only in latitudes several degrees south of Toronto. Also, of the mollusks found in the Don beds, four of the species are not now found in the St. Lawrence basin, but only after passing the watershed which separates it from that of the Mississippi. On the other hand, the upper, or Scarboro sands and clays are wanting in the species indicating a warmer climate but abound in both a flora and a fauna suggestive of Labra- dor and of the region north of Lake Superior. In the opinion of Professor Coleman these facts cannot, be accounted for except on the supposition that the earlier ice-sheet retired from practically the whole region to the northward before the latter one began its advance; which certainly looks very reasonable at first sight. But there are a number of considerations, too much overlooked, which perhaps permit a contrary conclusion. 1. Weare not warranted in assuming that the advance of the ice was simultaneous from the Keewatin and the Labra- dorian centres. On the contrary it seems certain, as has been shown above, that the advance from the Keewatin center was much earlier than from the other. The so-called Kansan till underlies the Illinoisan for several hundred miles east of the Illinoisan border. For example the Illinoisan ice crossed the Mississippi at Burlington, Iowa, and advanced many miles westward. But Kansan ice had at an earlier time spread eastward so as to carry Lake Superior copper as far as Warren in Western Pennsylvania. In a previous chapter (p. 527) attention is called to the fact that the boundary of the glaciated areas in the central and eastern parts of the: United States consists of the arcs of two circles with their centers respectively in Labrador and the Lake Superior region. | This will appear at a glance by consulting the map. Now, 586 THE ICE AGE IN NORTH AMERICA. the junction of these arcs is at Salamanca, New York, almost exactly on the meridian of Toronto. It is therefore a plau- sible hypothesis that the lower till at Toronto was deposited by the Keewatin ice-sheet near its eastern margin and that it withdrew some time before the Labradorian sheet reached that point. | This opens up a wide field of speculation connected with our theories of the cause of the spread of the various ice-sheets. On the theory that elevation of land is the prime cause it would appear that the rise of land proceeded in a wave from west to east. The Keewatin center therefore rose first and sent out its ice-sheets far south to Kansas,and east to Pennsyl- vania. Then as it began to sink under its accumulating load of ice, the eastern or Labradorian center began to rise and in due time started its glaciers to meet the vanishing ones from the Keewatin center. But, possibly long before Toronto was reached by the Labradorian ice-sheet, the Keewatin glacier had retired from its eastern limit amid conditions of climate that were essentially preglacial. For it must be borne in mind that the retreat of the ice can only take place when the climate is abnormally warm. Indeed such warmth would seem to be essential for the melting of the ice. An interesting direct.proof of this was found by Dr. Holst in southern Sweden, where he excavated gravel beds in front of the principal moraine which contained remains of plants and animals characteristic both of warm and cold climates in close connection, and which must have been contemporane- ous. Similar facts were reported to me by Professor Tscher- naschev from Finland. Itis also well known that large species of oysters lived long after the glacial epoch in Maine, especially at Damariscotta, which do not survive except on our southern coasts. It isin point also to instance the spread of the masto- don, the mammoth, the rhinoceros and even the hippopot- amus under the conditions which prevailed in northern Europe and Asia during the glacial period. THE DATE OF THE GLACIAL PERIOD. 587 A further line of inferences follows from studying the probable cause of the rise of the water in Lake Ontario dur- ing the accumulation of the interglacial delta at Scarboro. This, as we have stated, was 150 feet, and the deposits at the bottom indicate a warm climate, and those at the top a cold climate. Now if we study the conditions involved it will appear that there isstrong confirmation of the theory just advanced. Evidently, as Professor Coleman points out, the deposition of the Don beds began when the level of Lake Ontario was just about what it is at the present time. That would imply that its outlet was still through the St. Lawrence, which must then have been unobstructed by ice. But as the Labradorian ice advanced and closed up this outlet the water level would eventually rise to the height of the col at Rome, N. Y., leading through the Mohawk into the Hudson River. This is 200 feet above Lake Ontario. But as it is shown that now the axis of post-glacial elevation is the Mohawk Valley, the north shore of Lake Ontario may well have been rela- tively fifty feet higher during glacial times than it is now, which would bring the elevation of the col at Rome into exact harmony with that of the upper Scarboro beds. Under this theory we have that gradual passage from warm to colder conditions which we need to account for the change in species in passing from the lower to the upper beds. And this is just what Dr. Lamplugh has shown to be the case in the glacial deposits of England.* 2. The uniformity in the distribution of the till over the southern portion of the glaciated area in the Mississippi Valley is partly an illusion, due to the fact that the great amount of loess covering the region, especially in southern Indiana and Illinois and in eastern Nebraska, prevents, to a considerable extent, observations upon the original surface, and this loess, as has already been shown, is doubtless the * “Presidential Address to the Geological Section of the British Association for the Advancement of Science,’’ at York, 1906. 588. THE ICE AGE IN NORTH AMERICA. finer part of the glacial débris carried southward by the gla- cial streams—so that, upon any theory, we should expect a much larger accumulation of loess over the southern portion of: the area. | | Mr. Leverettrelieslargely on the great erosion of the Kansas sheet tillasanindicationofitsage. He estimates, for example, that innorthern Missouri not over thirty per cent of the origi- nal plainisleft upon the retreat of the ice, in the narrow tabu- lar remnant remaining upon the divides. ‘‘The streams are flowing in valleys that have broad slopes and bottoms, the slopes being so toned down as to fall generally below 5° and not uncommonly to 3° or even less. Theslopes of the valley, twenty-five meters in depth, often havea breadth of about a kilometer, and the bottoms of small drainage lines often exceed a kilometer in width. Topographic sheets of the United States Survey, which well illustrate the post-Kansan. erosion, are the Atlanta, Edina, and Kahoka quadrangles of northern, Missouri.” (See comparison of North American Glacial; Deposits, from “ Zeitschrift fur Gletscherkunde,”’ vol. iv, p., 298). ~ With this he compares a part of the Belleville, Ill., topo- graphic sheet which shows 60 per cent or more of the original glacial plain untouched by erosion; but again in the Iowan drift. (which Mr. Leverett would now identify with the Illi- noisan epoch), the portion of the glacial plain which is undis- sected is not greatly in excess of the Kansan plain from Missouri. It should benoted furthermore that the blanket of Kanga till is comparatively uniform over its whole area. There are no moraines in it, and there never were any. Moreover, the deposit was rarely thick enough to disguise the preglacial topography. Much of the supposed evidence of post-glacial erosion. is probably the result of this: failure of the glacial cee vy iD fill the valleys Siar channels of ae original topog- raphy. | eCr Rats 1:83333. ' aoe re = = Be ale§ or 1.666660. eae se sheet. Scale #; Million or erosion. n drift. foto as art re : » 2. 3.9 oe Be de a e al: ee } Sa HE re ge =n SME - : NY ae eo. eras BRN iy eee sic Gy ateN<: fb in (Ko ey VSS on Gre ae P| PALE ee if bos a ees + Fic. 149—Part of Altanta _ Co tourinterva]l 20 feet 590 THE ICE AGE IN NORTH AMERICA. The controlling influence of the preglacial topography may be observed in the neighborhood of Galesburg, Illinois, where all along the divide between the Illinois and Mississippi rivers the surface presents an extensive general level, covered with glacial drift of Illinoisan age to a considerable depth. But as one proceeds on either side towards the rivers men- tioned the size of the preglacial valleys increases so rapidly that the glacial blanket is not sufficient to disguise them, while near the water-shed on both sides appear the original extensive amphitheaters characteristic of valleys of extreme age. , Evidently the post-glacial erosion is not by any means so great as would at first appear to be the case. But what seem ~ to be valleys of post-glacial erosion are simply adjustments of the glacial blanket to the precedent valleys of erosion. Again, the broad valleys bordering the south-flowing streams of gentle gradient in the Illinoisan and Kansan regions differ only in moderate degree from similar valleys in the Wisconsin area. As instances I would note the valleys of the Nishnabotna, the Tarkio, the Nodaway, and the Platte rivers of northwestern Missouri, all of which rise in southwestern Iowa, and, after flowing long distances, enter Missouri. One can but be impressed in crossing these valleys with their great width, and with the signs that they were occupied by immensely larger streams of water than it is possible to provide under present conditions. On comparing these valleys with that of the river Styx, a small streamin Wisconsin drift just south of the water-shed in MedinaCounty, Ohio, we find a very small stream occupying a level flat- bottomed valley, a third of a mile wide, which is evidently the product of the lingering ice and the floods pouring through the valley during the melting of the late Wisconsin period. The contrast between this valley and the valleys in north- western Missouri is by no means great, certainly not so great as to imply an enormous lapse of time between their formation. THE DATE OF THE GLACIAL PERIOD. o91 In both cases, doubtless, the wide troughs were preserved by the presence of lingering masses of the melting ice sheet. 3. The theory of a general depression of the glaciated area with reference to the sea-level may apply to a certain portion of a single period as well as to one of two distinct periods. We may suppose a low slope of a surface and the consequent imperfect drainage and slow-moving waters dur- ing the maximum extent of a single glacial epoch as well as during the first of two epochs. The theory that the weight and attraction of the ice were tangible factors in pro- ducing the relative depression of land which characterized a portion of the Ice age would lead us to expect the greatest depression during the period of maximum extension. When the ice-front had retreated from Carbondale, Ill., to Mad- ison, Wis., the intervening area had been relieved from an enormous amount of pressure. 4. With reference to the comparative absence of glacial strize and of planing and grooving over the southern area, it should be noted, first, that fresh exposures of rock in that region are very infrequent, owing to the great depth of till and loess; and, secondly, that upon any theory the gla- cial grooving and striation would necessarily grow fainter as the boundary was approached, because the movement of ice over that portion was so much less than over the central and northern portions; and, thirdly, the absence of planation is not relatively so great as is sometimes represented. The grooves and striz in Highland and Butler counties, Ohio, very near the margin, and in southwestern Indiana and southern Illinois, still nearer the margin, are as clear and distinct as can anywhere be found. Also, upon the surface of the limestone rocks, within the limits of the city of St. Louis, where the glacial covering was thin, and disintegrat- ing agencies had had special opportunities to work, I found very clear evidences of a powerful ice-movement; and at Du Quoin, IIl., only forty or fifty miles back from the ex- treme limit of glaciation, I was greatly impressed with the extent to which the surface rock had been planed, by ex- 592 THE ICE AGE IN NORTH AMERICA. amining the fragments brought up from a shaft which had recently been sunk first through fifty or sixty feet of surface soil, and then for some distance into the rock. The small fragments from the surface of the rock thrown up were most beautifully planed and striated. A thorough study of the condition and disteibatea of the buried forest-beds bears strongly, as I can not but think, against the complete separation of glacial epochs in North America. In addition to the facts about to be enumerated, it is a significant circumstance that the buried vegetable de- posits under consideration do not mark a warm climate, but. a climate much colder than the present—such a vegetation, in fact, as would naturally flourish near the ice-margin. The buried forests of southern Ohio have a striking resemblance to those we described in Glacier Bay, Alaska. Peat and hardy coniferous trees are predominant. One of the most instructive localities in which to sindy organic remains embodied in glacial deposits is in the region, included in the southern part of Montgomery and the north- ern part of Butler county, Ohio. The glacial deposits con- taining organic remains in that. vicinity were first described by Professor Orton, of the Ohio Survey, in 1870.* Near Germantown, on Twin Creek, in Montgomery county, about thirty miles north of Cincinnati, there is exposed, at a sharp angle of the stream, a perpendicular bank of drift ninety-five feet in height. Underneath this is a deposit of peat as much as fourteen feet thick. The upper portion of the peat “ con- tains much undecomposed sphagnous mosses, grasses, and sedges.” . Both the stratum of peat and the clayey till above ‘contain many fragments of coniferous wood, some of which ean be. identified as red cedar (Juniperus Virginia- nus).” Immediately above the peat-bed there is from tifteen to twenty-five feet of what seems to be true till. This shows no sign of stratification, and abounds in striated stones. Next above occurs a band about ten feet thick of stratified * “ American Journal of Science,” vol. ¢, 1870. THE DATE OF THE GLACIAL PERIOD. 593 material containing coarse gravel and a good deal of fine sand. Above this to the top seems again to be true till, Fie. 151.—Section of till near Germantown, Ohio, overlying thick bed of peat. The man in the picture stands upon a shelf of peat from which the till has been eroded by the stream. The dark spot at the right hand of the picture, just above the water, is an exposure of the peat. The thickness of the till is ninety-five feet. The partial strat- ification spoken of in the text can be seen about the middle of the picture. The fur- rows up and down had been made by recent rains. (United States Geological Sur- vey.) (Wright.) with, however, an occasional pocket of sand or thin stratum of stratified material. But, both up and down the stream from this point the till merges into gravel-beds partially ce- 594 THE ICH AGH IN NORTH AMERICA. mented together by infiltrations of lime and iron. Down the stream the stratum of peat rises to a higher level, so as eventually to come in contact with the first band of stratified material just mentioned, the intervening till gradually thin- ning out between them. The appearance is that of a saucer- shaped deposit of peat such as would have formed in a ket- tle-hole, and which was subsequently filled and covered with the advance of the glacier. That the facts indicate a somewhat prolonged interval between the first advance of the ice over the immediate re- gion and the second, can not, therefore, well be denied, for the peat is clearly enough between two glacial deposits. But it may well be questioned whether an interval of two or three centuries would not suffice for the accumulation of the peat described ; for it will be observed that it seems to have oc- curred in a large kettle-hole in which the vegetable matter naturally gravitated toward the center and is much deeper there than near the edges. It is not therefore allowable to take the extreme thickness of peat as the measure of the amount of accumulation during the interglacial period. | As to the rapidity with which peat may accumulate in favorable circumstances, we can do no better than transfer a recent discussion of the subject from the pen of the veteran botanist, Leo Lesquereux, contributed to the “ Annual Report of the Pennsylvania Geological Survey for 1885 ” : * Two conditions are necessary for the origin and growth of peat—water either stagnant in basins, lakes, pools, etc., or water abundantly supplied by a boggy atmosphere, increased by dense forest-growth. Pools of stagnant water, when not exposed to periodical drying up, are invaded by a peculiar vegetation : first, mostly composed of conferve, simple, thread-like plants, of various color and of prodigious activity of growth, mixed with a mass of infusoria, animalcules, and microscopic plants, which, partly decomposed, partly continuing the floating vegetation, soon * Pages 106, 107, 113, 114. THE DATE OF THE GLACIAL PERIOD. 995 fill the basins, and cover the bottom with a floating of clay- like mold. So rapid is the work of these minute beings, that in some cases from six to ten inches of this mud is deposited in one year. Some artificial basins in the large ornamental parks of Europe have to be cleaned of such muddy deposits of floating plants, mixed with small shells, every three or four years. When left undisturbed this mud becomes gradually thick and solid—in some cases of great thickness, affording a kind of soil for the growth of marsh-plants, which root at the bot- tom of the basins or swamps and send up their stems and leaves to the surface of the water or above it, where their substance becomes in the sunshine hard and woody. As these plants periodically decay, their remains, of course, drop to the bottom of the water; and each year the process is repeated, with a more or less marked variation in the species of the plants. After a time the basins become filled by these suc- cessive accumulations of years or even centuries, and then the top surface of the decayed matter, being exposed to atmos- pheric action, is transformed into humus and is gradually cov- ered by other kinds of plants, making meadows and forests. In this way many deposits of peat are buried under- ground and remain unknown until discovered by diggings or borings. Such are the immense peat deposits in the great swamps of Virginia, the Dismal Swamps, and all along the shores of the Atlantic from Norfolk to New Orleans. In other cases when basins of stagnant water are too deep for the vegetation of aquatic plants, Nature attains the . same result by a different special process, namely, by the pro- longed vegetation of certain kinds of floating mosses, espe- cially the species known as sphagna. These floating masses grow with prodigious speed, and, expanding their branches in every direction over the surface of ponds or small lakes, soon cover itentirely. They thus form a thin floating carpet, which, as it gradually increases in thickness, serves as a solid soil for another kind of vegetation, that of the rushes, the sedges, and some kinds of grasses, which grow abundantly mixed with the mosses, which by their water-absorbing structure furnish a persistent humidity sufficient for the preservation of their re- 596 THE ICE AGE IN NORTH AMERICA. mains against aérial decay. The floating carpet of moss be- comes still more solid, and is then overspread by many species of larger swamp-plants and small arborescent shrubs, espe- cially those of the heath family ; and so, in the lapse of years by the continual vegetation of the mosses, which is never inter- rupted, and by the yearly deposits of plant remains, the carpet at last becomes strong enough to support trees, and is changed into a floating forest, until, becoming too heavy, it either breaks and sinks suddenly to the bottom of the basin, or is slowly and gradually lowered into it and covered with water. .. . The absorbing power of the peat-mosses enables them to grow higher and higher above their original water-level, from which they thus gradually emerge. The name emerged bogs has been therefore given them. The peat of emerged bogs is less compact; the annual layers are more distinct, generally well defined in their succes- sion. At the top of the bog the layers measure about one inch in thickness, at the bottom less than one eighth inch, and in old bogs still less. The growth, therefore, though not very rapid, is easily observed and registered in several ways. It may be measured by compass and level from the border of the swamp, the central portion of which becomes gradually higher and higher, screening from the view of a spectator on one side of it objects which had been before observable on the other side of it. It may be estimated also by a time-scale, in cases where ancient bridges, pavements, etc., whose epoch of construction is certified by documents, are ee buried under beds of peat of known thickness. Again, in places where peat-bogs have been worked for a number of years, old pits are encountered, now entirely re- filled ; and when this happens with peat, during the life of the proprietor, who has himself dug the old pits and can recall the exact date, very precise data are thus furnished for learning the amount of time necessary for the reproduction of a bk thickness of peat. The rate of growth depends, of course, on atmospheric or other local circumstances, but, putting together many such pieces of documentary testimony obtained in different coun- THE DATE OF THE GLACIAL PERIOD. 597 tries, the average production of compact matter may in a general way be estimated at one foot in a century. In immerged bogs, formed of vegetable débris falling into water, the peat grows more slowly and less regularly. The actual rate of its growth has not yet been positively recorded. In very extensive bogs, stretching between Swiss lakes, timber posts have been discovered on the line of an old road, and parts of a bridge buried beneath five or six feet of compact, black peat. Although the exact date of these constructions has not been fixed, the discovery of Roman medals in the vicinity suggests the beginning of the Christian era. ‘This shows that the kind of peat which results from the maceration of plants under water is of much slower growth than the peat layers of the emerged boys. It is also more compact, and is quite black, the vegetable matter being more completely de- composed, and its internal structure generally so destroyed as to be unrecognizable. The peat of emerged bogs, on the con- trary, is yellowish-brown, fibrous, its annual layers distinct, and the woody fragments more generally recognizable. Since the above was written a well sunk at Germantown through the till 100 feet deep, nearly a mile northeast of the exposure shown on p. 593, penetrated a peat layer several feet in thickness, showing that the deposit is extensive and perhaps older than we had estimated. It should also be said that Mr. Leverett is not fully convinced thatthe gravel under- neath the peat is glacial, but thinks that it probably is. But we are not compelled to assume a slow growth, nor even the average growth asthe rate. The cool, moist climate of a glacial age would seem to be peculiarly favorable to both the growth and the preservation of peat; so that two hun- dred or three hundred years is perhaps ample for the pro- duction of all the facts connected with the peat accumula- tions at this point. If it be asked how such a deposit of peat could be overwhelmed with ice without disturbance, the answer is that, as suggested by N. H. Winchell, before che reinvasion of ice the peat in the kettle-hole and probably the 598 THE ICVh AGE IN NORTH AMERICA. rim of the whole had become frozen, and so capable of re taining its form. Similar deposits of peat in superficial kettle-holes are very frequent in the glaciated region, and constitute an important portion of. the reserved stores of fuel laid up for the future use of man. Professor Lewis and myself had an excellent opportunity to study such a modern deposit at Freehold, Warren county, Pa.* Here one half of such a hole had === Sir trattif ew of yeh 7 ——— SS - SSS Fic. 152—Section of kettle-hole in Freehold, Pennsylvania. (See text.) been removed in making a road, and exposed a complete and fresh section through the middle. The depth of the peat in the middle was six feet, growing gradually thin- ner in each direction toward the sides. Peat and soil were mingled in alternate layers near the edges. Numerous logs of prostrate trees were also imbedded in the peat. It is evident that had there been a readvance of the ice over this region after the above accumulation was complete, and had the soil become frozen, there would have been at Freehold an interglacial deposit of vegetable matter closely analogous to that described at Germantown. A comparatively short interval between the periods of recession and advance of the ice-front in southern Ohio is also indicated in numerous places where fragments of wood are found imbedded in true glacial deposits near the glacial margin. For example, near Darrtown, on Four-Mile Creek, in Butler county, Ohio, is an exposure of till, sixty-five feet high, containing fresh red-cedar logs near the bottom, and fragments of wood in all conceivable positions throughout the lower half of the deposit. The deposit is true till, being unstratified and full of scratched stones, many of which are - granitic. There is, however a line of stratified material * See “Second Geological Survey of Pennsylvania, Z,” p. 171. a THE DATE OF THE GLACIAL PERIOD. 599 about half-way up the bank, which is about two feet thick, and contains pebbles several inches in diameter. Not much Fig. 153.—Section in till near Darrtown, Butler County, Ohio, sixty-five feet high. Coarse line of stratification near the middle. Fresh cedar logs at the bottom. (See text.) (United States Geological Survey.) (Wright.) wood is found above this line, yet there is some, and the structure above seems identical with that below. All this would seem to indicate that there was a temporary retreat of 600 ‘THE ICH AGE IN NORTH AMERICA. the ice, when fora short time water sorted and deposited material over the lower stratum of till; then there was a re- advance, pushing along a vast mass of unsorted material over the stratified stratum without disturbing it. In the deposit already described near Germantown, evidence of as many as four such marks of successive advances and retreats can be seen. Again, near Oxford, in Butler county, a few miles up the same stream (Four-Mile Creek) from Darrtown isan ex- posure of till where the unstratified character is perfectly manifest in which I observed and photographed a piece of wood, well preserved, projecting from the perpendicular face of the bank about forty feet below the surface, and where no land-slide could have occurred.* _ Equally good sections were also seen on Aunt Ann’s Run, near the city of Hamilton, in the same county, and only about twenty miles north of Cin- cinnati. Usually, as has been remarked, these buried deposits of peat and wood have been assumed to imply the existence of two distinct glacial periods. But, from what has been said above, it would appear that the facts point rather to shorter periods of advance and recession of the ice-front, analogous to those which are now in progress in the Alpine glaciers, as heretofore noted. That the interval between the two move- ments noted at Darrtown was comparatively short is evident from the fact that the fragments of wood found mingled with the till, both above the stratum of stratified material and below it, are identical in kind, and are in a similar state of preservation. This locality is about twenty miles back from the glacial margin. In the instances next mentioned of wood being found imbedded in glacial deposits the locality is still nearer the glacial margin, and, instead of being interglacial are pre- glacial—that is, the vegetable remains have glacial deposits over them but not under them. * See Fig. 148, p. 577. THE DATE OF THE GLACIAL PERIOD. 601 A sycamore log was reported to me as found at Morgan- town, Morgan county, Ind., thirty feet below the surface. This is, however, in a stratified deposit, but one which was evidently formed in connection with the last stages of the Glacial period at that point. It is one quarter of a mile back from the little creek running through the village, and the. glaciai limit is but a few miles south, on the higher lands of Brown county. Again, near Seymour, Jackson county, Ind., logs of wood are reported as occasionally found in digging wells in the village at a depth of twenty feet below the surface. Sey- mour is on a glacial terrace, in the line of one of the largest glacial floods carrying off the melting torrents from the de- caying ice over a good part of southeastern Indiana. The wide terrace on which Seymour stands, and in which the logs are found, is about sixty feet above the present bed of the East Fork of White River, running through the place. Black- walnut logs are also mined from the banks of the river in low water. This instance is not probably decisive of the age of the buried wood, as the terrace may be the product of the so-called second Glacial period. Still, there can be no doubt that the most recent glacial advance extended to the borders of Brown county, which lies a little west of the locality just spoken of, and’ which is nearly in the lat- itude of Butler county, Ohio, alluded to in a previous para- graph. Another most decisive instance of vegetable remains in till near the margin occurs in Bigger township, in the south- eastern corner of Jennings county, Ind. Here Mr. Burchill reported to me the finding of wood im a well, twelve feet deep, in a hard blue clay which, from neighboring exposures, is, without dovbt, true till. On another farm, near by, wood was reported to me as found thirty feet below the surface in a well that failed to reach the rock at that depth. This is on as high land as there is in that region, and is about ten miles north of Madison, on the Ohio River, and about five hundred feet above it. 602 THE ICE AGE IN NORTH AMERICA. Professor Borden * reports a well at Paris Crossing, in Jefferson county, about twelve miles southwest of the fore- going place, in blue-drift clay forty feet below the surface. The same authority also reports a well at Milan, near the summit of Ripley county, Ind., which is as far south as Cin- cinnati, and about twelve miles northeast from the river, with muck and wood fifty-four feet down in what is evidently the true till of the region. In Hamilton county, Ohio, the late Colonel Charles Whittlesey reported thirty-five wells containing muck-beds, leaves, or timber, from three hundred to five hundred feet above the Ohio River.t That at New Burlington is certainly in till. In Highland county, Professor Orton reports many cases of the occurrence of such vegetable deposits. In the village of Marshall, “eleven wells out of twenty reached a stratum of vegetable matter with leaves, branches, roots, and trunks of trees.” Marshall is on the very limit of the glaciated region. Similar instances were reported to me in the south- ern part of Highland county and in Clermont county. In Ross county, near Lattas, Mr. J. M. Connell reported to me finding wood in a well, situated very near the extreme limit of glacial action, and where it could not possibly have been brought into position by means of water. .The locality is four hundred and twenty-five feet (barometer) above the valley, just to the north, near Frankfort, and five hundred and twenty-five feet above the valley of the Scioto River at Chillicothe, ten miles to the east. The till is massed up against and upon the margin of a rocky plateau, here facing the north, in great quantities. The well described was in this marginal till upon the highest land, and passed through twelve feet of yellow clay, then through three or four feet of blue clay, then ten feet of yellow clay, then gravel for five feet. About thirteen feet below the surface there was * “Geological Report of Indiana,” 1875, p. 172. { “Smithsonian Contributions to Knowledge,” 1869, pp. 13, 14. THE DATE OF THE GLACIAL PERIOD, 603 found a log of wood three or four feet long and about three inches in diameter. This was in the blue clay, and was ac- companied with traces of muck. There is not space to mention the many other places where wood is reported in the modified drift filling what are perhaps preglacial channels serving as outlets of the melting glacial torrents, and which may therefore have been trans- ported a long distance from their native place. One such was reported to me in the valley of Raccoon Creek, in Gran- ville, Licking county, Ohio, and but a few miles from the glaciated border. This was found ninety-four feet below the surface of the terrace, which would bring it about forty feet below the present bed of the stream. A few miles farther up in this same valley so many red-cedar logs were formerly found beneath the glacial terraces along the valley, and the wood was so fresh, that a flourishing business was for a while carried on in manufacturing household utensils from them. Red cedar is not found in that region now, and these logs are probably of the same period with those described as found in true glacial till in Butler county, and which are so fresh as to preserve still the peculiar odor of the wood. Professor Collett reports that all through that portion of southwestern Indiana included within the glacial boundary there are found, from sixty to a hundred and twenty feet be- low the surface, peat, muck, rotted stumps, branches and leaves of trees, and that these accumulations sometimes occur through a thickness of from two to twenty feet. We may mention, also, as probably connected with the period of the ice-dam at Cincinnati, the well-preserved or- ganic remains found in the high-level terraces of various trib- utaries of the upper Ohio. In the vicinity of Morgantown, Professor I. C. White, as already noted, reports that, in the terraces which he connected with the period of the Cincinnati ice-dam, the leaves of cur common forest-trees are most beau- tifully preserved some distance below the surface, and that logs of wood in a semi-rotten condition were encountered seventy feet below the surface. At Carmichaels, in Wash- 604 THE ICE AGE IN NORTH AMERICA. ington county, Pa., a log of wood was also reported to me as found in a situation similar to that described by Professor White, buried thirty feet in the sand of a corresponding » high-level terrace some miles back from the present bed of the Monongahela. Wood was also reported to me as found in a similar situation in terraces two hundred and fifty feet above the Alleghany River at Parker, Pa. The terraces there are many miles outside the glacial limit, but by their granite pebbles are unmistakably connected with the Glacial period. The wood was reported as dug from quicksand in a well two miles east of the river, and two hundred and fifty feet above it. iat : Another instance of wood which has been preserved in a deposit of the Glacial age is worthy of more minute descrip- tion. In this case I have the advantage of having found it myself. The locality is that of Teazes valley, Putnam county, W.Va. This valley runs from the Kanawha River a little below Charleston to the Ohio at the mouth of the Guyan- dotte near Huntington. The valley, as already described,* is clearly enough a remnant of early erosion, when the water of the upper Kanawha took that course to join the Ohio. The valley is very clearly marked, being about a mile wide, and from two hundred to three hundred feet lower than the hills on either side, and having a remarkably level floor throughout the greater part of its course. The bottom of the valley is filled throughout with a deposit of river-pebbles covered many feet with a mixture of sand and clayey loam. In some places this loam is from thirty to forty feet deep, extending for several miles without interruption, as at Long Level, about the middle of the valley.t Here a section about half a mile long and twenty-five feet deep shows at the top a stiff stratum of clay containing wood at a depth of seven feet. Immediately below is sand containing much iron, and cemented together by the infiltrations of the ore. The stra- tum above, containing the wood, had never been disturbed, * See p. 379. 1 See Fig. 111,on p. 380. THE DATE OF THE GLACIAL PERIOD. 605 and the wood (a small specimen of a knot of some coniferous tree) is remarkably fresh in its whole appearance. It is scarcely possible that it should have remained in such a posi- tion during the immense period supposed by Mr. Croll to have elapsed since the glacial age. Many of these cases of subglacial vegetable accumula- tions are beneath or in deposits of the very earliest portion of the glacial period. Unquestionably of this age are those found in Jackson, Jennings and Jefferson counties, Indiana, and those found by Professor I. C. White in the terraces of the Monongahela River, which are now correlated with the earliest stages of the ice advance to the water-shed between the Great Lakes and the Ohio River. Farther north, notably in Mower County, Minnesota, a stratum of peat from eighteen inches to six or eight feet in thickness, with much wood, is very uniformly encountered in digging wells, the depth varying from twenty to fifty feet. “‘From all accounts it (the peat stratum) appears to be em- braced between glacial deposits of gravelly clay, and it seems to mark a period of interglacial conditions when coniferous trees and peat-mosses spread over the country . There are extensive marshes now existing in northern Min- nesota, mainly covered with ericaceous plants, with some cedar and tamaracks that are forming immense peat deposits. With an increase of the amount of moisture in the air such peaty accumulations would spread over much higher levels. A return of glacial conditions would bury such marshes be- low the deposits that are known as drift.’’* The observations of Professor Tarr upon the burial of forests and peat bogs by the recent advance of glaciers in Alaska are deserving of the most careful consideration in our interpretation of the significance of the facts which are being here detailed. *N.H. Winchell in “Geology of Minnesota,’’ vol. i of ‘Final Re- port,”’ p. 363. 606 THE ICE AGE IN NORTH AMERICA. ‘Along both the Atrevida and the Malaspina glacier mar- gins, the glacier and glacial deposits are advancing in forested regions and overspreading old soils, peat beds, and forests. When the process of present change is at an end there will be in this region soil beds and plant beds interbedded with glacial deposits, and all as the result of a sudden change in glacier-margin conditions. It requires no elaboration of this subject to make it clear that here is a hint of great significance in the interpretation of pleistocene deposits. In view of such phenomenaas those described above it is evident that the interpretation sometimes placed upon plant beds and soil beds intercalated in pleistocene deposits—namely, that they prove i | Fria. 154—Forest lately disturbed and about to be overwhelmed by an advancing Alaskan glacier. (Photo by Gilbert. ) separate glacial epochs—can hardly stand without the support of other and convincing evidence that the plant or soil bed interval was of long duration.’’* All this is in the region where the natural drainage is to the south; but, upon entering the northern water-shed, especially in the area now covered by the deposits of Lake Agassiz, in- terglacial deposits would seem necessarily to imply that the *R. 8. Tarr and B.S. Butler, ‘““The Yakutat Bay Region, Alaska,’’’ “U.S. Geological Survey,’’ ‘‘Professional Paper,’ 64, pp. 86, 87. THE DATE OF THE GLACIAL PERIOD. 607 ice had melted back sufficiently to reopen the natural drain- age lines of the Red River Valley into Hudson Bay. Mr. Upham confesses that beds of vegetal deposit which are both underlaid and overlaid by till are very rarely found in northern Minnesota. Still, he supposes some such are found, and gives an exhaustive list of instances.* The two which he mentions as being in the area of Lake Agassiz are encount- ered in digging wells, first, at Barnesville, Clay county, where twelve feet of till was penetrated, then one foot of quicksand “containing several sticks of tamarack up to eight inches in diameter ; second, in Wilkin county, where the record is that till occupied the first eight feet, then a layer of gray sand one half an inch in thickness, then a much harder lower till for eighteen feet, which was underlaid by sandy black mud containing many snail-shells. But these two cases hardly seem sufficient to establish the theory, while the correspond- ing cases adduced by the Canadian geologists farther north are not described with sufficient minuteness to render their meaning unequivocal.t . Another class of phenomena bearing on the questions of the discontinuity and date of the great Ice age is to be found in the inclosed lake-basins lying between the Rocky Mount- ains and the Sierra Nevada, near the fortieth parallel. Nu- merous salt lakes now occupy this region. But it is evident, even upon hasty examination, that these are but insignificant remnants of those which formerly occupied it. Great Salt Lake is estimated to have contained at one period four hun- dred times its present volume of water. The terraces mark- ing its former limits are very distinctly visible, and are nine hundred feet above its present level. Lake Mono has several distinct terraces, the highest of which is six or seven hun- dred feet above the present level. Pyramid and North Car- son Lakes, in Nevada, are but the remnants of an immense salt lake extending from the Oregon boundary to latitude * “Minnesota Geological Report for 1879,” p. 48. + ‘Report of Progress, Geological Survey of Canada, 1882-’84,” p. 414, C. 608 THE ICE AGE IN NORTH AMERICA. 38° 30’ south, a distance of two hundred and sixty miles. The Central Pacific Railroad is built through the bed of this lake for one hundred and sixty-five miles, from the vicinity of Golconda to that of Wadsworth. This ancient lake has been carefully surveyed and described by Mr. I. C. Russell, of the United States Geological Survey,* and has been named | (| il cw il} tl il in NT | ly il Fic. 155.—Sketch map of the Pacific coast, showing the outlines of the ancient lakes Bon- neville and Lahontan. (Le Conte.) * “Third Annual Report of the United States Geological Survey,” pp. 195= 235, and “ Monograph XI,” 1885. THE DATE OF THE GLACIAL PERIOD. 609 Lake Lanhontan, as that of which Great Salt Lake is the rem- nant was named Lake Bonneville, after the first explorers of the region. These basins have now no outlet to the sea. That of Lake Lahontan never had any; but, if the relative levels were the same at former times as now, Lake Bonne- ville at its greatest extent poured through Snake River into the Columbia. During the year 1890 Mr. Gilbert published the first volume of his monograph upon Lake Bonneville—the ancient enlarge- ment of Great Salt Lake, Utah—to which reference has just been made above. Mr. Gilbert estimates that at its maxi- mum stage the area of this lake was 19,750 square miles—that is, about ten times the present size of Great Salt Lake—and that its maximum depth was one thousand and fifty feet, as compared with about forty feet at. present. The climatic changes indicated by the studies of this ancient lake cor- respond closely with those indicated by Mr. Russell’s study of Lake Lahontan as detailed on page 607. Early in post- tertiary times there was a great rise in these lakes, though not sufficient by ninety feet to reach the passage through the Port Neuf River into the Snake. This first rise was fol- lowed by a long epoch of desiccation, during which it is prob- able the lakeentirely disappeared. Thisinter-lacustrine epoch was a long one, as is indicated: by the extent of the gravel deposits which were then laid down. After this there was a second rise, in which the water attained theheight of the pass- age from the Cache Valley to the Port Neuf, and then rapidly “cut a channel three hundred and seventy-five feet deep in the alluvium to a sill of limestone.”’ At this level (about six hun- dred feet above the Great Salt Lake) the water was held for a long time, forming what is known as the Provost shore-line. During the period of the Provost shore-line, glaciers descended from the Wahsatch Mountains, and left their moraines near the margin of the lake. 610 THE ICE AGE IN NORTH AMERICA. In searching for an explanation of the former increase in. size of these bodies of water, the conditions of the Glacial period naturally present themselves as furnishing an ade- quate cause. Glaciers, however, never occupied much of the territory, being found only to a limited extent in the border- ing mountain-ranges. But the proximity of the glaciated region, and, indeed, the general conditions favoring the pro- duction of the Glacial period in North America, would be ample to produce the temporary enlargement of these lakes. A slight increase in precipitation, or a slight diminution of temperature, would either of them cause a rise in the water until the balance should be readjusted between the rainfall and the evaporation. It would seem that there is here also a significant record of an interglacial epoch, for the lakes have had two periods of increase, with an arid period intervening. During the first rise of the lakes, sediment to the extent of one hundred and fifty feet in thickness was deposited. There was then a dry period, in which the lakes were reduced to their present dimensions, or even smaller, when these first deposits were subjected to a period of erosion by surface streams, and partly covered with gravel. There was also upon it a deposit of great quantities of compact stony tufa precipitated from waters saturated with calcium carbonate. After the period of low water there was a subsequent reflooding of the basin, which reached a horizon thirty feet higher than the first. During this rise a deposit of thinolite took place, and of other substances whose position and character serve to note the changes. Subsequent to this rise the evaporation proceeded at an increased rate until the basins were completely desic- cated, and only began to refill within a period which Mr. Russell estimates to be less than three hundred years. All this, however, might have occurred within the space of a few thousand years, and does not, independently of other evidence, go far to establish the complete duality of the Ice age. As to the date of the expansion of these lakes, Mr. Rus- sell expresses it as his opinion that ‘the last desiccation oc- THE DATE OF THE GLACIAL PERIOD. * ‘Ot4 curred certainly centuries, but probably not many thousands of years ago.”* This opinion is sustained by the fact that the erosion of present streams in these old beds is slight, and by the fact that in the cafions of the high Sierra, which were once occupied by glaciers, “the smooth surfaces. are still scored with fine, hair-like lines, and the eye fails to detect more than a trace of disintegration that has taken place since the surfaces received their polish and striation. . . . It seems reasonable to conclude that in a severe climate like that of the high Sierra it [the polish] could not remain unimpaired for more than a few centuries at the most.” To the same effect is the testimony of Mr. Gilbert as to the date of the last great extension of Lake Bonneville, of which he says: “The Bonneville shores are almost unmodified. Intersect- ing streams, it is true, have scored them and interrupted their continuity for brief spaces ; but the beating of the rain has hardly left a trace. The sea-cliffs still stand as they first stood, except that frost has wrought-upon their faces so as to erumble away a portion and make a low talus at the base. The embankments and beaches and bars are almost as perfect as though the lake had left them yesterday, and many of them rival in the symmetry and perfection of their contours the most elaborate work of the engineer. There are places where bowlders of quartzite or other enduring rock still re- tain the smooth, glistening surfaces which the waves scoured upon them by dashing against them the sands of the beach. “ When this preservation is compared with that of the low- est tertiary rocks of the region—the Pliocene beds to which King has given the name Humboldt—the difference is most impressive. The Pliocene shore-lines have disappeared. “The deposits are so indurated as to serve for building- stone. They have been upturned in many places by the up- lifting of mountains. Elsewhere they have been divided by faults, and the fragments, dissevered from their continuation in the valley, have been carried high up on the mountain- * “ Monograph XI,” p. 273. 612 THE ICE AGE IN NORTH AMERICA. fianks, where erosion has carved them in typical mountain. forms. . . . The date of the Bonneville flood is the geologic yesterday, and, calling it yesterday, we may without exag- geration refer the Pliocene of Utah to the last decade the Eocene of the Colorado basin to the last century, and re- legate the laying of the Potsdam sandstone to prehistoric times.’’”* Mr. Gilbert believes that all this is attributable to sue- cessive elevations of the region, with an intervening subsidence. The evidence of a post-tertiary elevation is found ‘in the deeply submerged channel near Cape Mendicino,” while the proofs of asubsequent depression “are supplied by the marine terraces of the Columbia and Fraser basin, and by the post- tertiary beds of the California coast recently described by Dall as rising gradually toward the south until at Monterey and southward they are about six hundred feet above the sea-level. . . . The uplifting of the Wahsatch range is shown to be still in progress by post-Bonneville fault- scraps.’ Mr. Gilbert’s study of the horse-remains found in the region would assign them to the period of ‘the upper- most of the Lahontan and Bonneville beds,” thus transferring their geological horizon from the late tertiary to the latter part of the glacial period. It is interesting to note, in connection with these old lake-basins, that the Dead Sea in Palestine probably has a similar relation to the development of glaciers in the Le- banon Mountains, and Russell is of the opinion that the gravel-deposits reported at various elevations about it are, like those of Lakes Bonneville and Lahontan, records of the Glacial period. My own investigations upon the glacial deposits of the Lebanon Mountains, however, showed that there had never been any glaciers reaching the head-waters of the Jordan Valley; but there was a glacier descending from the highest *“‘Second Annual Report of the U.S. Geological Survey,’’ p. 188. } ‘‘Jordan-Arabah and the Dead Sea, ‘Geological Magazine,’’ vol. 5, pp. 337, 387. } 4 ; % aq 1 4 ’ THE DATE OF THE GLACIAL PERIOD. 613 summit of the mountains about thirty miles northeast of Beirut and depositing an extensive moraine upon which the present grove of the Cedars of Lebanon are growing. The height of the summit is a little over 10,000 feet, and the glacier descended to the Ievel of 5,000 feet above the sea. The mo- raine is about three miles broad at the foot, and extends five miles back toward the summit, and is several hundred feet thick at its termination. Though not directly connected with the Jordan Valley the climatic conditions accompanying the formation of this glacier doubtless extended a long dis- tance in that direction and so may account for the enlarge- ment of the Dead Sea indicated by the abandoned shore- lines, the most persistent of which is 650 feet above its present level. (See “Records of the Past,’ July, 1906, pp. 195-204.) Such are, in brief, the considerations which seem to make it proper to hesitate before recognizing the theory of discon- tinuous pleistocene epochs in America as an established doctrine to be taught. The most of the facts adduced to support the theory of distinct epochs are capable of explana- tion on the theory of but one epoch with the natural oscil- lations accompanying the retreat of so vast an ice-front. It seems more likely that the retreat from the extreme border of the glaciated area to the line of the moraines of the several later glacial epochs was analogous to that from one to another of the successive twelve or thirteen receding concentric lines of moraine appearing on our general map and on that of Minnesota made from the latest reports, than that successive glacial advances should so nearly duplicate the first as it is made to do on the other theory. After a painstaking discussion of the whole subject, Professor Prestwich expresses it as his opinion that— The time required for the formation and duration of the great ice-sheets in Europe and America (the Glacial period) need not, after making all allowances, have extended be- yond fifteen thousand to twenty-five thousand years, instead 614 THE ICE AGE IN NORTH AMERICA. of the one hundred and sixty thousand years or more which have been claimed. | The adoption by some of a term of eighty thousand years for the post-Glacial period has been very much the result of the belief that no shorter time would account for the excavation of the valleys supposed to have been formed during this period, on the assumption of a “‘uniformitarian”’ rate of denudation. Thisrate, based on observations made at the present time, always seemed to me open to grave objections, and in this belief subsequent experience has confirmed me. . . . and I would for the same reasons limit the time of the so-called post-Glacial period, or of the melting away of the ice-sheet, to from eight thousand to ten thousand years or less.* Summary. — The terrestrial facts brought to light as clearly. bearing on the question of the date of the glacial era are much more numerous than they have heretofore been supposed to be. Scarcely more than a beginning has been made in their collection and interpretation ; but, as far as we have gone, the investigation has been most interesting and suggestive. For the most part these facts imply a later date for the Glacial period than the current astronomical theory would admit, and so far they go to disprove that theory. The glaciated area seems a vastly newer country than the unglaciated. In the glaciated region the waterfalls have hardly more than begun to recede; the valleys and gorges are both narrower and shallower than in the unglaciated por- tion of the country ; the lakes and kettle-holes are yet unfilled with sediment, and their outlets have not yet to any great extent lowered the drainage lines; the striated rocks have resisted disintegration to a remarkable degree during post-gla- cial times, and the moraines and kames have retained their original forms with little signs of erosion. Niagara Falls and the Falls of St. Anthony can neither of them be over ten thousand years old. The waves of Lake Michigan can * See Prestwich’s “ Geology,” vol. ii, pp. 533, 534. THE DATE OF THE GLACIAL PERIOD. 615 not have washed its shore for a much longer time, and the smaller lakes and kettle-holes of New England and the North- west can not have existed for the indefinite periods some- times said to have elapsed since the glacial era, while eternity itself is scarcely long enough for the development of-species if the rate of change is no greater than is implied if man and his companions both of the animal and vegetable kingdom were substantially what they are now as long ago as the date often assigned to the great Ice age. But while approximate limits are already set to giacial chronology, the field is still open for an indefinite amount of painstaking inquiry. Local observers may now profitably spend as much time upon a single river-valley or in a single county as has yet been spent upon the whole field between Cape Cod and the Mississippi. Fie. 156—Bowlder bed at Pocatello, Idaho, where the Port Neuf river debouches upon the Snake river plain. These bowlders were brought down to their present position by the torrential floods which followed the overflow of Lake Bonneville, described on pages 609 and 704. CHAPTER XXI. MAN AND THE GLACIAL PERIOD. Wuen, in 1863, Sir Charles Lyell published his great work upon “The coaenis of Man,” the general public was somewhat surprised to find that one tenia and sixty pages, or almost one third of the entire volume, was devoted toa discussion of glacial phenomena. This course was justified by the fact that rough-stone implements, undoubtedly of human ed EG had recently been found in deposits BIG. 1é 7.—Typical collection of Gulealithie implements, reduced in photograph to one eighth natural size. The four in the lower row are of “argillite from the gravel in Trenton, New Jersey. The smal! one, a lit- tle above the lower row is from Moustier, France. The large one in the middle row is from’ Amiens, France. The two at the left of it are from France. The one at the right is from upver Egypt. These are all of flint. The four in the upper row, a core of flint and flakes of flint. supposed to be of glacial age in north- ern France and southern England, making the question of the antiquity of man one no longer of mere history or archeology, but of glacial geology. A further reason for the prominence giy- en to the discussion of purely glacial questions in Sir Charles Lyell’s work was the comparative ignorance, at that time, of the character, extent, and significance of glacial phe- nomena. The discussions running through the previous MAN AND THE GLACIAL PERIOD. 617 chapters of the present volume prepare the way for readily understanding even a summary statement of the facts already discovered con- . | necting man with the Gla- cial period in North Ameri- ca. We may, therefore, with- out further pre- liminaries, at once address ourselves to the subject, and de- scribe the con- ditionsin which implements of Fic. 158.—Reverse side of 2 implements shown in the preced- ing figure. 3 ee a =. ao human manu- facture have been found in the glacial deposits on this con- tinent. At the outset two questions arise in the discussion: 1. Whether the implements found are really artificial and gen- uine. 2. Whether the deposits in, which they occur really belong to the Glacial period. 1. That the implements are of human origin is evident from close inspection, and comparison with natural frag- ments. Flint and some other species of stone are specially adapted for the manufacture of implements, because of their hardness, and of the facility with which flakes can be struck from them so as to leave a sharp, cutting edge. Many nat- urai forms of flint can be appropriated as useful tools with- out modification. The action of frost upon a flint nodule, or the accidental falling of a stone upon it, may produce a sharp-edged fragment of convenient size for use. But the proof of human workmanship consists in a series of fractures of such character and so arranged that they irresistibly indi- cate design. One prominent feature of an artificial flake is 618 THE ICE AGE IN NORTH AMERICA. the so-called “bulb of percussion.”” When a sharp, well- directed blow falls upon a flint nodule, the force distributes itself in such a way that, in the immediate vicinity of the blow, a slight hollow is made in the nodule, and the corre- sponding bulb in the flake is shaped somewhat like the ball of one’s thumb, while the rest of the flake is straight and regu- lar in form. It is possible that this bulb of percussion may sometimes be made by the accidental falling of one stone upon another; but such an occurrence must, in the nature of the case, be very rare, since the blow must be delivered at exactly the right point and at the proper angle, in order to produce the right result. The chances are exceedingly small that such a blow should be delivered except by design. As to the arrangement of the fractures, the evidence is even more conclusive. A simple cutting edge may readily be formed by natural forces; but, in the implements that are regarded as of human origin, the arrangement of the fract- ures producing the cutting edge is so complicated as to pre- clude the supposition that they are undesigned. Nor does it require many secondary chippings to establish the artificial origin of an implement. A half-dozen subsidiary chippings on a natural flint pebble, serving to bring it into a symmetry such as would serve the purpose of a human being, is evi- dence enough. A trained eye has no difficulty in distin- guishing, at a glance, between natural forms and artificial forms. ‘The loose statements asserting that there is occasion for grave doubt as to whether the mass of so-called palso- lithic implements are really implements can only be made, and be believed, by those who have given little personal at- tention to the subject. That I may not seem to place too much confidence in my own judgment in this all-important matter, I have thought it best to secure the opinion, concerning the imple- ments of which this chapter treats, of one who has had ample opportunity to examine them and compare them with those from other parts of the world, and whose authority would be second to that of none. I therefore addressed a letter MAN AND THE GLACIAL PERIOD. 619 to Professor Henry W. Haynes, of Boston, requesting his opinion on the subject. His reply I will, with his consent, reproduce.* 3 Boston, January 23, 1889. DEAR Proressor Wricgut: You ask for my opinion in regard to the artificial character of the quartz fragments dis- covered by Miss Babbitt, at Little Falls, Minn., as well as of the argillite objects discovered by Dr. Abbott, at Trenton, N. J., and those still more recently obtained by Dr. Metz and Mr. Cresson. In replying to your inquiry I must premise by stating that, although I have had abundant opportunity of studying all these different objects, I have only visited one of the localities where they were found—that is Trenton, N. J.— where, as you know, I was accompanied by yourself, Professor Boyd Dawkins, and the late Professor Henry Carvill Lewis, in my examination of the region ; but I had previously visited many localities in Europe, where paleolithic implements have been discovered ; and I have myself found many. Several years of study in that country have made me familiar with the cleavage of flint, and the method of fabricating rudely chipped implements. Subsequently, in this country, for a still longer period, I have given much attention to the tools and weapons of the Indians, and the different materials of * I would remark that Professor Haynes’s private collection of paleoliths is one of the largest in this country, and abounds in representatives from every locality where they have been found. The following is a list of his publications upon the subject: Silex Acheuléeus de VEgypte, “ Bull. de la Soc. d’Anthrop. de Paris,” 3d ser., vol. i, p. 389; “The Fossil Man,” “ Popular Science Monthly,” July, 1880, p. 350; “The Egyptian Stone Age,” “Nation,” January 27, 1881; “Discovery of Paleolithic Implements in Egypt,” “ Memoirs of the American Academy of Arts and Sciences,” vol. x, p.357; “ The Argillite Implements,” ete. “Proceedings of the Boston Society of Natural History,” vol. xxi, p. 1382; “ The Paleolithic Man,” “ American Antiquarian,” vol. vi, p. 187; ‘The Stone Age in Prehistoric Archeology,” ‘ Science,’’ vol. iv, pp. 469, 522; “Man in the Stone Age,” “Science,” vol. v, p. 43; “The Bow and Arrow unknown to Paleolithic Man,” “Proceedings of the Boston Society of Natural History,” vol. xxiii, p. 269; “‘ Paleolithic Man in London and its Neighborhood,” “ Science,” vol. ix, p- 221; “Opinion on Paleolithics,” ‘‘ American Antiquarian,” vol. x, p. 125; “The Prehistoric Archeology of North America”; ‘ Narrative and Critical History of America,” vol. i. pp. 329-368. 620 THE ICE AGE IN NORTH AMERICA. which they were fashioned, in a great many different localities. I think, therefore, I have gained an acquaintance with the character of the fracture of very many different kinds of stone, which have been broken by man intentionally for his use as tools. I say this, because I have always.been in the habit of compar- ing and contrasting such broken stones with those whose fract- ure had been occasioned by different natural forces, so that I might learn the resemblances and the differences between. them. ‘This is a subject which it is difficult to treat of satis- factorily in writing, as it is so much an affair of ocular dem- onstration. ‘These little minute differences and peculiarities are very palpable, when they are pointed out, although a geolo- © gist, or a mineralogist, who is perfectly familiar with the ma- terial, but who may have had little or no training as an arche- ologist, may have failed to notice them. The whole subject is one solely for the judgment of the expert; and when a heap of. broken stones, characterized by a general external re- semblance, ‘has been submitted to the determination of several trained archeologists, as I have often seen done in Europe, there has been no difference of opinion among them as to which were natural and which were artificial forms. Of course, if the broken stones have been afterward subjected to the action. of running water, so as to produce a general wearing away of the edges of the fractures, the difficulty of discriminating becomes much greater. In such cases only a very practiced eye can de- cide; and the opinion of any man, however eminent he may be in other departments of knowledge, who has not had great archeological experience, is practically worthless. It was in the autumn of 1880 when we visited Trenton, and at that time I found a few paleoliths there myself; after-. ward Dr. Abbott gave me quite a collection of his own find- ing, which I have had ever.since in my possession, and have continually studied. So in repeated instances have I examined his great collection in the Peabody Museum. At a meeting of the Boston Society of Natural History, in January, 1881, I expressed my conviction as to the artificial character of these argillite implements, notwithstanding the fact that the. coarseness of their material precludes their ever equaling in workmanship the flint implements of Europe. My subsequent MAN AND THE GLACIAL PERIOD. §21 study of the same and other objects from that locality has only served to strengthen the opinion I then expressed. The quartzes discovered by Miss Babbitt I first saw in the autumn of 1882, when she forwarded a box of them for my inspection. The following summer she sent me another lot of them on deposit ; both of these have been in my possession ever since, and have been repeatedly studied by me. I have also examined the collection she sent to the Peabody Museum. I should judge that I have thus had at least a hundred and fifty of these pieces of quartz brought under my careful scrutiny. Miss Babbitt had no knowledge of archeology, and her fanci- ful speculations in regard to the supposed use that had been, or might have been, made of certain fragments, which she dig- nified with the name of types, have tended to obscure the real presence among them of some well-marked examples of palezo- lithic implements. I wrote her my opinion in regard to them, and a portion of my letter was printed by her in connection with her articles on ‘‘ Vestiges of Glacial Man in Minnesota,” in the June and July numbers of the “‘ American Naturalist ” for 1884. In this I stated that ‘‘ some of them I believe to be implements ; many are only chips struck off in shaping imple- ments, and refuse pieces left from such work ; many are natural forms, and one or two rolled pebbles. . . . I trace clearly upon your implements such a preparation of them (i. e., by having had most of their projections battered off by another stone) for holding them in the hand. Many of yours bear evident marks of use in the worn condition of portions of their edges or of their points.” All my subsequent study of them has tended to confirm this opinion, and I can only repeat my assured conviction that these rudely fashioned implements, and the fragments that were found with them, whose edges are still as sharp as when they were first struck off, are the ‘‘ prod- uct of an intentional breaking by the hand of man and not the result of natural causes.” It is important to notice that among the hundreds of paleolithic implements discovered by Dr. Abbott, at Trenton, a few made of quartz are so absolutely similar to those found by Miss Babbitt, and now either in my possession or at the Peabody Museum, that it would be impossible to distinguish them apart. 622 THE ICE AGE IN NORTH AMERICA. The implements discovered by Dr. Metz and Mr. Cresson, and now also in the Peabody Museum, are as palpable human tools as any I ever saw, although, on account of the inferior quality of the material of which they are made, they are not equal in excellence to similar objects of like age in Europe. I can not conceive of any one, who has a proper acquaintance with the subject, entertaining a moment’s question as to their artificial character. By this frank expression of my conviction, I have en- deavored, as best I can, to answer your questions, and remain, Sincerely yours, HENRY W. HAYNEs. A still further question with regard to these implements relates to their genuineness. Their present commercial value offers temptation for their forgery, and there can be no doubt that hundreds of implements of the very earliest type have been made to order and sold to unsuspecting collectors. Still, however perfect these forgeries may be in form, only the inexperienced and the unwary can be deceived by them. There are certain chemical changes affecting the superficial aspect of an implement which time only can produce. A fresh flake can readily be distinguished by a practiced eye. As yet not enough is known of the rapidity with which weathering takes place under stated conditions, to make it a basis for chronological calculation; but the difference be- — tween a very ancient implement and a very recent one is easily enough detected. It isa significant fact early observed, and supported by all recent discoveries (if we except those in California, of which further mention will be made), that in America as in Europe the implements found in glacial deposits are all of a peculiar type. None but implements of stone have been found in these deposits; and of the stone implements none are polished and smooth, but all are rude in form and roughly flaked. From their evident antiquity, as will be shown a little later, these rough stone implements are called palwolithic (Gr. mandaws “old,” and dios, MAN AND THE GLACIAL PERIOD. 623 “stone ”); while the later stone implements are classified as neolithic (Gr. véos, “ new,” and AlGos, “ stone”). Paleolithic implements are said to be old, however, not because of any inelastic theory of evolution, implying that people using rude arts always precede those who are more skilled, but the age of these implements as a class is deter- mined by the fact that they have been found in undisturbed glacial deposits or under other geological conditions showing their antiquity. Such implements are unquestionably older than others found upon the surface ; and, in their case, the evidence of great age is definite and conclusive, while the antiquity of the implements found upon the surface is sub- ject to more or less of doubt. If man inhabited the region bordering upon the great ice-sheet when it extended to its farthest limits, his implements should be found near the sur- face of the ground outside those limits; and such might be of even greater age than those which are found in stratified glacial deposits themselves. Also, as the ice receded, it is to be expected that man would follow it in its slow recession (as the Eskimo does to-day in Greenland) and that his imple- ments would be lost upon the surface. How long he may have continued thus to use implements of paleolithic type can not readily be determined. Mr. Thomas Wilson, of the Smithsonian Institution, has already collected, or had reported to him, many thousand implements of the paleolithic type found in various parts of North America. In almost all cases these were found upon the surface, and there is no means of determining their age except from their general weathered appearance, as implements of the same forms have been made and used all through the Stone age. About the year 1860 interest in the subject of man’s an- tiquity received a new and definite impulse in connection with the discoveries of Boucher de Perthes in northeastern France. As long ago as 1841 this indefatigable investigator discovered rudely fashioned stone implements in high gravel terraces along the valley of the Somme at Abbeville. An account of his discoveries was published in 1846. Little at- 624 THE ICE AGE IN NORTH AMERICA. tention was paid to the matter, however, until 1859, when Dr. Falconer, Mr. Prestwich, Mr. Evans, Sir Charles Lyell; and other English geologists visited the locality, and brought the discovery more fully to public attention. Full deserip- tions may be found in the works of Sir Charles Lyell on “The Antiquity of Man” * and Sir John Lubbock on “ 4 historic Times.” + The river Somme is a small stream, about one hundred miles in length, occupying a broad, deep trough, about a mile in width at Abbeville, worn out 4 chalk formations. Upon the sides of this trough, up to an elevation of something over one hundred feet, there are remnants of gravel terraces, formed when the river flowed at a correspondingly higher level than now. ‘These terraces consist wholly of material local to the Somme Valley, and not in any degree of foreign — drift. The implements found are imbedded in undisturbed strata of this gravel. In connection with them, also, there are found bones of many animals now extinct, those of the Elephas primigenius being specially numerous. Soon after the confirmation by these eminent authorities of the important discoveries made by Boucher de Perthes, examination showed that the same class of rudely formed chipped stone implements occurred also in gravel-deposits in southern England. The relation of these deposits to the streams was similar to that of those in the valleys of north- eastern France. Indeed, a discovery of paleeoliths had been made in England more than fifty years before, in the very first years of the century; but its importance was not sus- pected until Boucher de Perthes’s discoveries called attention anew to the subject. Mr. John Frere had, in the year 1800, described a collection of flints found at Hoxne near Diss, in Suffolk, England, specimens of which were preserved in the British Museum and in the collections of the Society of Anti- quaries. These proved to be of the same type with those found at Abbeville, and the deposits are of corresponding * P. 106 ef seq. + P. 342 et seq. MAN AND THE GLACIAL PERIOD. 625 character in the two places. Similar discoveries were also made at various other places in southeastern England, the most important being in the vicinity of Southampton and the Isle of Wight. When we come to examine these European deposits with reference to their relation to the Glacial period, it must be confessed that we enter a rather obscure field. The region in Europe in which paleolithic implements have been found imbedded in the gravel of river terraces is peculiar for its limitation. In Great Britain none have been found north of a line connecting the British Channel with the Wash, and on the Continent these discoveries are all outside the direct action of glaciers either from the Scandinavian or the Swiss fields. Hence it will be seen that the problem is quite dif- ferent from that which we shall presently study in America, and is far more complicated. Still, the same rule holds good in one country as in the other, that the higher terraces are older than the lower, and there can be little doubt that the terraces in which paloliths are found are directly or in- directly of glacial origin. But the data for estimating the time which has elapsed since the deposition by glacial tor- rents of the high-level gravels in the valley of the Somme and in southern England are much less clear than in this country. The year 1875 marks an epoch in the prehistoric arche- ology of North America, since it was then that Dr. C. C. Abbott’s attention was first specially attracted to the imple- ments of a paleolithic type found in the neighborhood of his residence in Trenton, N. J. Whether these implements were from the surface, or from the gravel which underlies the city, was at first uncertain, for they had then been found only in the talus of the gravel-banks. But Dr. Abbott’s residence at .Trenton enabled him during the succeeding year to give attention to the numerous fresh exposures of the gravel made by railroad and other excavations; and he was soon rewarded for his pains by finding several chipped imple- ments in undisturbed strata of gravel, some of which were as 626 THE ICE AGE IN NORTH AMERICA. much as twelve feet below the surface. Since that time he . has continued to make similar discoveries at various _ inter- vals. In 1888 he had already found four hun- dred implements of the paleeolith- ic type at Tren- ton, sixty of which had been taken from re- corded depths in the gravel, two hundred and fif- ty from the talus at the bluff fac- ing the river, and the remainder from the surface, or derived from collectors who did not record the positions or circumstances under which they were found. Fic. 159.—Face view of argillite implement, found by Dr. C. C. % Abbott, ee fblnit aed’ New vivo t in dank three In 1878 Profess feet from ace of bluff, and twenty-two feet from the sur- . face (No. 10,985). (Putnam. )* or J. D. Whit- * This cut, together with the following ones credited to him, Professor F. W. Putnam has kindly furnished me, for use in advance of publication, from his elaborate report upon the palzolithic implements in the Peabody Museum of American Archeology and Ethnology, Cambridge, Mass. The numbers in paren- theses are those on the implements, and correspond to the catalogue of the museum. The figures are natural size. MAN AND THE GLACIAL PERIOD. 627 uey, with Mr. Lucien Carr, of the Peabody Museum, Cam- bridge, visited Dr. Abbott, and they together found several palzeolithic implements in the undisturbed gravel.* And again, in 1879 and 1880, Professor F. W. Putnam was with Dr. Abbott when specimens were found in similar condi- tions. Mr. Carr describes the situation as follows: It was “in a fresh exposure made by a re- cent heavy storm, and was about three feet deep in the ground, and one foot in from the perpen- dicular face of this newly ex- posed surface.” Professor Put- nam gives the following descrip- tion of his discoveries: A short distance from Dr. Abbott’s house, and very near where the Trenton gravel joins the marine gravel, there is a deep gully through which flows a small brook. In this gully the gravel- bank is constantly washing away, and presenting new surface ex- posures. After a heavy rain in June, 1879, I visited the spot with Dr. Abbott and his son. Here I noticed a small bowlder of about six or eight inches in diameter, projecting an inch or two from the face of the bank about four feet from the surface of the soil above ; I worked the stone from the gravel in which Fie. 160.—Side view of the preceding. (Putnam.) it was firmly imbedded and drew it out. At the back part of the cavity thus made I noticed the pointed end of a stone, and * “ Proceedings of the Boston Society of Natural History,” vol. xxi, p. 145 628 THE ICE AGE IN NORTH AMERICA. after working it up and down a few times, so as to loosen the. gravel about it, I drew out the implement now exhibited, a b ome rit sh “a ——_ Fie. 161.—Argillite implement found by Dr. C. C. Abbott, March, 1879, at A. K. Rowan’s: farm, Trenton, New Jersey, in gravel sixteen feet from surface. a, face view ; 3, side view. (No. 11,286.) (Putnam.) On the same day I discovered a second specimen in place eight feet from the surface, and Dr. Abbott’s son Richard found another about four feet from the surface. These three specimens were found within twenty or thirty feet of each other, after a heavy shower had made the most favorable con- ditions for their discovery. My own first visit to the locality was in November, 1880, in company with Professors W. Boyd Dawkins, Henry W. Haynes, and H. Carvill Lewis, when we were conducted by Dr. Abbott to the various localities favorable for investiga- tion. Professor Lewis and myself also repeatedly visited the MAN AND THE GLACIAL PERIOD. 629 locality afterward. But neither of us was ever so fortunate as to find a paleolithic implement in place, or even in the fresh talus of the bluff facing the river. As our experience is that of many others who have visited the locality, and hence of attempts in some quarters to throw doubts upon the genuineness of Dr. Abbott’s discoveries, it is worth while to record that Professors Dawkins and Haynes independently Fic. 162.—Chipped pebble—black chert, found by Dr. C. C. Abbott, 1876, near the site of Lutheran church, Trenton, New Jersey, in gravel six feet below the surface. a, face view ; 6, side view. (No. 10,986.) (Putnam.) found implements in the talus over which we had passed a moment or two before; but, as the attention of Professor Lewis and myself was directed chiefly to the geological prob- lems relating to the character and age of the deposit itself, our failure to discover implements where trained eyes saw them but illustrates the limitations of observers. To distin- guish a roughly flaked human implement in a bed of gravel and pebbles where the ratio of artificial flakes to the natural forms is as one to a million, is like finding a needle in a hay- mow. Hence negative evidence, or a failure of particular 630 THE ICE AGE IN NORTH AMERICA. observers to find implements, has very little weight in discrediting the testimony of others who have been more successful. : | The acrimonious controversy over the genuineness of these implements of supposed glacial age was finally put to rest by a fortunate discovery made by Mr. Ernest Volk, while working under the auspices of the Peabody Museum of Cam- bridge, Mass. The discovery was that of a human femur, in undisturbed gravel twenty feet below the surface, and be- neath a thick deposit of crossbedded coarse gravel which unquestionably belongs to the glacial era. The accompanying illustration of the gravel pit in which this was found lies in the same bank shown in the illustration on p. 521, but after the gravel bank had been excavated 100 feet or more farther back from the river. Accepting as now beyond question that. these palzeolithic implements ‘at Trenton occur in undisturbed strata of the — gravel, of which the evidence just given would seem to be sufficient, the question of the archzologist as to the age of the deposit is asked of the geologist, and it is for him tu answer. In the light of the preceding chapters, a ready an- swer is found to this question. The city of Trenton is built upon a horseshoe-shaped gravel-deposit which is about three miles in diameter, extending back about that distance to the east from the present river. This deposit is somewhat lower around its inland boundary than along the river. The prongs of this horseshoe rest, one at Trenton, and the other two miles below, just north of the house of Dr. Abbott. This gravel is thus described by Professor Shaler : The general structure of the mass is neither that of ordi- nary bowlder-clay nor of stratified gravels, such as are formed by the complete rearrangement by water of the elements of simple drift-deposits. It is made up of bowlders, pebbles, and sand,..varying in size from masses containing one hundred cubic feet or more to the finest sand of the ordinary sea-beach- MAN AND THE GLACIAL PERIOD. 631 Fic. 163.—Typical section of the Trenton gravel in which the implements described in the text are found. Note the distinct stratification and the large angular bowlder near the surface, showing the presence of floating ice, since by no other means could such a bowlder get into sucha position as here found. The elevation of the surface is here 50 feet and is about half a mile back from the river edge of the bluff. Perpendicular exposure is here between 30 and 40 feet. (Photograph by Abbott.) es. There is little trace of true clay in the deposit ; there is rarely enough to give the least trace of cementation to the masses. The various elements are rather confusedly arranged ; the large bowlders not being grouped on any particular level, and their major axes not always distinctly coinciding with the horizon. All the pebbles and bowlders, so far as observed, -are smooth and water-worn, a careful search having failed to show evidence of distinct glacial scratching or polishing on their surfaces. The type of pebble is the subovate or discoidal, _and though many depart from this form, yet nearly all ob- served by me had been worn so as to show that their shape had been determined. by running water. ,The materials com- prising the deposit are very varied, but all I observed could apparently with reason be supposed to have come from the Fig. 164—Graveldepositat Trenton, N.J., where Mr. Volk found a human femurin Dec- ember, 1899. The arrow points to the spot where the femur was discovered. (Courtesy of Records of the Past. ) ; MAN AND THE GLACIAL PERIOD. 633 extensive valley ot the river near which they lie, except per- haps the fragments of some rather rare hypogene rocks.* It is now settled that the rocks from which these beds were derived are all in place in the upper Delaware Valley.t The distinction between the river-gravel and that which overlies the larger part of southern New Jersey is marked in several ways. The Trenton gravel is much coarser than the genera! deposit, it is also largely composed of fresher looking and softer pebbles, showing that it has been subject to much less abrasion than the other, and that it is of more recent age; it is alsc limited to the river-valley, and finally is not overlaid by the Philadelphia brick-clay which, so far as it extends, rests unconformably upon the general deposit of gravel. The general deposit of gravel in this region is com- posed almost exclusively of small, well-rounded pebbles of quartz and of hard limestone which “are not fresh looking, but are eaten and weather-worn by age.” Fie. 128.—Section across the Delaware River at Trenton, New Jersey. a, a, Philadelphia red gravel and brick clay (McGee’s Columbia deposit) ; 6, 6, Trenton gravel, in which the implements are found; c, present flood-plain of the Delaware River. (After Lewis.) (In Abbott’s ‘‘ Primitive Industry.”’) The elevation of this implement-bearing gravel at Tren- ton is not far from forty feet above the present high-water limit; and Trenton is now at the head of tide-water. These gravels are continuous as a terrace all along up the river. As one ascends the river, however, their height (at least below the Water-Gap) is reduced to fifteen or twenty feet above the present flood-plain. But most significant of all the facts indicated are the character and position of the Philadelphia red gravel and brick-clay. This also is confined to the river-valley and its tributaries, and rests unconformably upon the older gravel * “Report of Peabody Museum,’’ vol. ii, 1876-’79, pp. 44-47. Tt ‘‘New Jersey Report for 1877,’’ p. 21; Lewis on ‘‘The Trenton Gravel,”’ p. 5. 634 THE ICE AGE IN NORTH AMERICA. formations, rising to a height of one hundred and fifty feet above the river, and there ceasing. This elevation relative to the river is maintained as far up as Easton, where the bed of. the river itself is one hundred and fifty ewe feet above tide-level. Finally, the Philadelphia brick-clay con- tains numerous bowlders of considerable size, derived from the ledges of Medina sandstone and other rocks above. This marks it as a deposit of the glacial flood some time during the declining centuries of the great Ice age. The succession of events would seem to be as follows: During the early part of the Glacial period the ice accumu- lated in the upper portion of the valley of the Delaware to a depth of many hundred feet. The area in the valley of the Delaware covered by the ice is not far from six thousand square miles. It is not improbable that the average depth of the ice accumulated over the region was considerably more than fifteen hundred feet, or a quarter of a mile, making the total accumulation of ice more than fifteen hundred cubic miles, with its southern border sixty miles above Trenton. All this as it melted must find its outlet to the sea through the Delaware River. It is evident ata glance that during the decline of the Glacial period, when the pro- cess of melting was proceeding with greatest rapidity, the floods in the valley below must have been upon a scale of surprising magnitude. And yet it is impossible that diese glacial floods in the Delaware should have been so enormous as to have filled the valley below Trenton to the height of one hundred and fifty feet, for this valley is nowhere less than five miles in width and constantly enlarges toward the sea. If the water at Trenton were raised one hundred and fifty feet, the slope to the bay would be about two feet per mile. Now, a current of five miles per hour, one hundred and fifty feet deep and one mile wide, would discharge a cubic mile of water every eight hours, or three cubic miles per day. (The mean rate of the Ohio River, with an average descent of five inches to the mile, is three miles per hour—that of the Mississippi MAN AND THE GLACIAL PERIOD. 635 very nearly the same.) To supply such a volume of water as this, the whole accumulation of ice in the upper Delaware would suflice for only five hundred days, or for about sixteen months. And to furnish this amount of water there would need to be, during such floods, a daily accumulation by rains and the melting ice over the whole upper valley of the Dela- ware of about three feet of water, which of course is incred- ible, even if we suppose the floods confined to a single month of each successive year. Hence, without doubt, we may con- clude that the deposition of the bowlder-bearing brick-clay in the Delaware Valley below Trenton implies a depression of that region to the extent of one hundred or more feet: Doubtless the region north of Trenton shared in this de- pression, but, being above the tide-water, the effects would not be equally evident. The valley above Trenton is narrow; at Lambertville, about twelve miles up the stream, a trap- dike contracts the valley to a width of about one quarter of a mile. Above this point the supposition of floods suft- cient to deposit the bowlder-bearing clay is, therefore, not in- eredible, especially since the descent in the stream was prob- ably less then than now. For the depression of that period proceeded, as we have seen, at increased rate northward. In Montreal, it was five hundred feet; in Vermont, about three hundred feet; and how much more or less in the vicinity of Lake Erie we can not tell. Such depression would greatly diminish the velocity of the torrent, and the narrow places in the valley would work to the same end. Professor Dana has shown that in the lower part of the val- ley of the Connecticut River the floods rose during the Cham- plain epoch from one hundred and fifty to two hundred feet above the present high-water mark. But the Connecticut River Valley below Middletown is contracted by trap-dikes much as the Delaware is at Lambertville; and the drain- age basin of the Connecticut is three times as extensive as that of the Delaware (being twenty thousand square miles). The effect of this obstruction, however, is partly offset by the branch currents which, as Professor Dana shows, set off from the Connecticut at various places above Middle- town. 636 THE ICE AGE IN NORTH AMERICA. After an exhaustive examination carried on for several years in connection with the New Jersey Geological Survey, Professor Salisbury reports finding deposits in that state corresponding to those here spoken of as Philadelphia brick clay and red gravel, which he describes under the local names of Bridgeton and Pensauken, reaching a height of 200 feet in the case of the former and 150 of the latter. But he is inclined to refer these ‘in large part to subaérial (fluvial and pluvial origin’). On this theory the deposits were chiefly brought into place by the Delaware and its tributaries during the close of the first glacial period, when the land was nearly at its present level, and the streams were overloaded with glacial débris. This accumulated as a broad delta over lowlands which were subsequently so much eroded that only the present remnants are left. But the extent over which the deposit is spread, as well as its character militates strongly against this theory. For the deposit extends for many miles northeast of the Delaware at Trenton, above where the unaided current of the glacial stream would carry the material, while several miles south- east of Trenton, bowlders, three and four feet in diameter, are found at an elevation of 200 feet, the bowlders being identical in material with others bearing glacial scratches found in the valley of the Delaware, twenty or thirty miles above Trenton. It hardly is possible that the whole area south of Trenton to the limit of these bowlders was covered with Bridgeton gravel to this height, Besides, the distribution of the bowlders in the brick clays of Philadelphia was evidently by stranded icebergs. In this clay bowlders two and three feet in diameter are distributed in a manner that would be impossible in any other way. A depression of 200 feet in the lower valley of the Delaware, therefore, cannot easily be dispensed with. Similar facts lead to the same conclusion respecting the depression at the mouth of the Susquehanna at the head of Chesapeake Bay, near Havre de Grace. MAN AND THE GLACIAL PERIOD. 637 At any rate, in the Delaware Valley we find bowlder-bear- ing clay rising to a height of one hundred and tifty or more feet above the present high-water level. In the Lehigh Valley, at Bethlehem, a few miles above its junction with the Delaware, and several miles south of the limit of the ice- field, Professor Lewis and myself found this bowlder-bearing clay containing scratched pebbles and lying unconformably upon thick deposits of coarse stratified gravel at a height of one hundred and eighty feet above the river. Farther up the Lehigh Valley also, near Weissport, we ascertained the limit of ice-carried bowlders to be one hundred and eighty feet above the river. We are probably safe in assuming that these floods, de positing clay and bowlders at the height above mentioned, mark both the period of greatest depression during the Gla- cial epoch and that when the ice was most rapidly melting away. Of course, the deposition of what Professor Lewis styles “red gravel,’ and the high gravels at Bethlehem, oc- curred earlier, since the clay overlies them. It is evident that the deposition of this bowlder-bearing clay is separated from that of the implement bearing gravel at Trenton by a period of considerable physical changes, if not of vast time. Considering, now, this Trenton gravel, we find it to be limited at the head of tide-water toa level of about forty feet, and diminishing in height relatively to the river both as one ascends and as one descends the channel, until at Yardleyville, a few miles above Trenton, it merges into the terrace which maintains a pretty uniform height of fifteen or twenty feet above the river all the way to the Water-Gap. Above the Water-Gap the gravel terraces rise to a much greater height. At Stroudsburg a second terrace stands seventy-five feet above the first terrace, which is about fifteen feet above Broadhead Creek. But this upper terrace is kame-like in its structure, and hence would be explained in part by the lingering presence of the glacier itself. The descent of the river-valley from Belvidere, where the 638 THE ICE AGE IN NORTH AMERICA. ice-sheet terminated, to Trenton, is two hundred and thirty- two feet, or.at the rate of nearly four feet per mile. ‘Now, the transportation of gravel by a river is dependent both upon the amount of material accessible to the running stream and upon the rapidity of the current. Toward the ~ close of the Glacial period the pebbles accessible to the stream were superabundant, having been deposited in excessive amount by the melting of the glacier in the lower latitudes. The water-worn pebbles at Trenton were probably largely derived from this source. Even a glacial torrent may have more loose material than it can manage, and so may silt up its bed with gravel. Hence it is not necessary to suppose the river at this point to have been of sufficient volume to fill the whole valley with water to the height of the terraces, tifteen or twenty feet. The river may have flowed upon a more elevated gravel bottom in a shallower current = the terrace would seem to imply. When, now, the current, passing down this declivity of four feet to the mile, reached the level of the sea at Trenton, its transporting power would be greatly diminished, and thus we should have an accumulation of gravel at the head of tide-water, without bringing into the problem the supposition of any very extraordinary increase in the volume of the river. The transporting capacity of a stream of water is esti- mated to vary as the sixth power of the velocity; i. e:, if a current is checked so that it moves at only half its former rate, its transporting capacity is diminished to one sixty- fourth.* It is easy to see that the sudden enlargement of the valley just above Trenton, as well as the occurrence there of tide-water, would diminish the rapidity of the river, and hence cause an extraordinary deposition of gravel when the moraines above were fresh and when ice-fields still lin- gered in the southern valleys of the Catskills. The process of deposition must have been so rapid that it might well have taken place not long before the withdrawal of the con- * See Le Conte’s “ Elements of Geology,” pp. 18-20. MAN:AND THE GLACIAL PERIOD. 639 tinental glacier to the north of the Catskills. The time re- quired for the river under present conditions. to erode the channel it now occupies was of much greater duration. The following is the probable course of events : 1,,.The Philadelphia brick-clay was deposited during the height of the Glacial epoch, when the Delaware Valley was considerably depressed below its present level. This is Mc- Gee’s Columbia. period. | 2; Toward the close of that period, when the land had ‘resumed its present level and the ice had nearly all. dis- appeared :south of the Catskills, the still. swollen stream brought-down the superabundant loose material from the kames:and moraines of. the glaciated area and deposited it in the valley below. The material was so abundant that doubt- less the whole. channel was silted up so that the bed of the river was considerably above. that it now occupies. At Tren- ton. it flowed over:and through:an extensive delta of coarse ‘grayel forty feet above its present level ; and, above Trenton, dyer an accumulation of gravel from fifteen to twenty feet above the present high-water mark. This period was marked by the presence of the mastodon and. other extinct animals with: palzeolithic man in the neighborhood of Trenton.* « , 8.. During the Terrace epoch the river. worked its way ‘down. through the delta gravel at Trenton, and has since eroded: its present channel which is about two miles wide. at that point. Higher up, where the current is swift, the lateral erosion in recent times has been small. .4, To.determine approximately the date of the earliest evidence of man’s appearance at Trenton we have as data: (1) The amount of erosion in the gravel at Trenton. (2) The ¥ Tt should have been mentioned earlier that Professor Cook found in this gravel, fourteen feet below the surface, the tusk of a mastodon, and that near the same place, at a depth of sixteen feet from the surface, Dr. Abbott took from it a portion of a human under-jaw, also from another place a human tooth, and from still another’ a “‘ very thick and in several respects singular human cranium.” Interesting as these are, however, they are too fragmentary to add materially to our information derived from the implements. See ‘‘ Annual Geo- logical Report for New Jersey for 1878,” p. 24; “Report of Peabody Museum for 1886,”’ p. 408. 640 THE ICE AGE IN NORTH AMERICA. general evidence from other sources bearing upon the date of the close of the Glacial epoch in this country, more fully treated of in the preceding chapter. Since my first visit to Trenton I have studied attentively all the streams situated like the Delaware with reference to the glaciated area between the Atlantic Ocean and the Mis- sissippi River, and can state from personal observation, as heretofore detailed, that a common cause, which can not be anything else than glacial floods operating while the ice re- mained over the head-waters of these streams, has been at work filling them with gravel-deposits similar to those de- scribed along the Delaware. Without exception, those south- erly-flowing streams, whose drainage area lies to any consider- able extent within the glaciated regions, are lined by exten- sive terraces of the overwash gravel of the Glacial! period. On obtaining definite information as to these facts, I at once pointed out * the importance of having local observers turn their attention to the discovery of palzoliths at various points in Ohio, where the glacial conditions were similar to those in the valley of the Delaware at Trenton. In my re- port to the Western Reserve Historical Society (p. 26) I wrote as follows: *“‘The gravel in which they [Dr. Abbott’s im- . plements] are found is glacial gravel deposited upon the banks of the Delaware when, during the last stages of the Glacial period, the river was swollen with vast floods of water from the melting ice. Man was on this continent at that period when the climate and ice of Greenland extended to the mouth of New York Harbor. The probability is, that if he was in New Jersey at that time, he was also upon the banks of the Ohio, and the extensive terrace and gravel de- posits in the southern part of our State should be closely scanned by archeologists. When observers become familiar with the rude form of these palzolithic implements, they will * “ American Journal of Science,” vol. cxxvi, pp. 7-14; “The Glacial Boundary in Ohio, Indiana, and Kentucky”; ‘‘ Western Reserve Historical Society,” 1884, pp. 26,27; ‘Ohio Archeological and Historical Quarterly,” vol. i, pp. 176, 177. MAN AND THE GLACIAL PERIOD. 641 doubtless find them in abundance. But whether we find them or not in this State [Ohio], if you admit, as I am com- pelled to do, the genuineness of those found by Dr. Abbott, our investigation into the glacial phenomena of Ohio must have an important archeological significance, for they bear upon the question of the chronology of the Glacial period, and so upon that of man’s appearance in New Jersey.” The substance of these remarks had been previously made by me in a meeting of the “Boston Society of Natural His- tory ” for March 7, 1883, and reported in “ Science,” vol. i, pp. 269-271. Commenting upon this report Dr. Abbott sent a communication to “ Science,” from which the following ex- tracts are very significant and interesting as connected with the discussion : In ‘‘ Science” of April 13th, p. 271, Professor Wright re- marks that ‘‘no paleolithic implements have yet been found fin Ohio], but they may be confidently looked for.” It has seemed to me possible, from mv own studies of the remains of paleolithic man in the valley of the Delaware River, that traces of his presence may only be found in those river-valleys which lead directly to the Atlantic coast, and that paleolithic man was essentially a coast-ranger, and not a dweller in the interior of the continent. If we associate these early people with the seal and walrus rather than with the reindeer, and consider them essentially hunters of these amphibious mammals rather than of the latter, it is not incredible, I submit, that they did not wander so far inland as Ohio, nor even so far as the east- ern slope of the Alleghanies ; and we need not be surprised if palzolithic implements, concerning which there can be no doubt whatever—for recent Indians made and used stone imple- ments that are ‘‘ paleolithic”’ in character—are not found in Ohio, nor even in Pennsylvania west of the valley of the Sus- quehanna River... . On the other hand, if the relationship of paleolithic man and the Eskimo is not problematical, and the latter is of Ameri- can origin, then I submit that man was preglacial in America, was driven southward by the extension of the ice-sheet, and probably voluntarily retreated with it to more northern re- 642 THE ICE AGE IN NORTH AMERICA. gions ; and, if so, then in Ohio true palezolithic implements will surely be found, and evidences of man’s preglacial age will ulti- mately be found in the once-glaciated areas of our continent.* The expectation of finding evidence of pregiat man in Ohio was met not long after this. Ata meeting of the Boston Society of Natural History t for November 4, 1885, “ Mr. Putnam showed an implement chipped from a pebble of black flint, found by Dr. C. L. Fic. 166.—Chipped pebble of black chert, found by Dr. C. L. Metz, October, 1885, at Madi- sonville, Ohio, in gravel eight feet from surface under clay, a, face view ; b,'side view. Note its resemblance to Fig. 126, from Trenton, New Jersey. (No. 40,970.) (Putnam. ) Metz, in gravel, eight feet below the surface, in Madison- ville, Ohio. This rude implement is about the same size and shape of one made of the same material, found by Dr. Ab- bott in the Trenton (N. J.) gravel, and is of special interest as the first one known from the gravels of Ohio.” Professor Putnain’s announcement, followed by a letter from Dr. Metz, saying that he had since found another implement in the * “Science,” vol. i, p. 359. ¢ “ Proceedings,” vol. xxiii, p. 242. MAN AND THE GLACIAL PERIOD. 643 gravel at Loveland, led me, on the 11th and 12th of No- vember, 1887, to visit the localities and see their relation to the glacial deposits of the region. The situation is as fol- lows: ! t id O | WARREN e Lebanon a AS ae KS 76 RIES PRICE rere S Ss eee eer Scale of Miles RS a RSS an ae 8% spl J.C. Teaters, B.C.ES/A/ 7 RS Ly pe wot ts Fic. 167.—Map showing glacial boundary, channels, and terraces near Cincinnati. Madisonville is situated eleven miles northeast of Cincin- nati, in a singular depression connecting the Little Miami River with Mill Creek, about five miles back from the Ohio (see Fig. 167). The Little Miami joins the Ohio some miles above Cincinnati, while Mill Creek joins it just below the 644 THE ICE AGE IN NORTH AMERICA. city. The general height of the hills in that vicinity above the river is from four hundred to five hundred feet. But the hills just north of Cincinnati are separated from the general elevation farther back by the depression referred to, in which Madisonville is situated. — The depression is from one to two miles wide, and about five miles long, from one stream to the other, and is occu- pied by a deposit of gravel, sand, and loam, clearly enough belonging to the Glacial-terrace epoch. Recent investigations make it probable that the Ohio formerly flowed north through Mill Creek, and joined the Great Miami near Hamilton. The surface of this is generally level, and is about two hundred feet above the low-water mark in the Ohio. On the east side, on the Little Miami River, at Red Bank, opposite Madi- sonville, the gravel is coarse, merging into pebbles from one to three or four inches through, interstratitied with sand, and - underlaid, near the river-level, with fine clay. There is here a thin covering of loess, or fine loam. On going westward this loess-deposit increases in thickness, being at Madison- ville, one mile west, about eight feet thick. Farther west it is much deeper, and seems to take the place of the gravel entirely. At several railroad cuttings, compact glacial clay appears underneath all. Thus, it is evident that this cross-valley, connecting Mill Creek with the Little Miami back of Avondale, Walnut © Hills and the observatory, was once much deeper than now, and has been filled in with deposits made when immense glacial floods were pouring down these two streams from the north. The Little Miami was a very important line of glacial drainage, as is shown by the extensive gravel-terraces all along its course, to which the railroads resort for ballast. The coarser material was deposited near the direct line of drainage, where the current was strong, while back from the river to- ward Madisonville, there was naturally an increase of the fine deposit, or loess, which is practically a still-water formation. In making an excavation for a cistern, Dr. Metz pene- trated the loess, just described, eight feet before reaching MAN AND THE GLACIAL PERIOD. , 645 the gravel, and there, just below the surface of the gravel,. the implement referred to was found. There is no chance for it to have been covered by any slide, for the plain is ex- tensive and level-topped, and, according to Dr. Metz, there had evidently been no previous disturbance of the gravel. Subsequently, in the spring of 1887, Dr. Metz found another paleolith in an excavation in a similar deposit in the northeast corner of the county, on the Little Miami across from Loveland. The river makes something of an elbow here, open to the west. This space is occupied by a gravel- terrace about fifty feet above the stream. The terrace is composed in places of very coarse material, much resembling that of Trenton, N. J.. where Dr. Abbott has found imple- ments. The excavation is about one quarter of a mile hack from the river, near the residence of Judge Jolmson. The section shows much coarser material near the surface than at the bottom. The material is largely of the limestones of the region, with perhaps ten per cent of granitic pebbles. The limestone pebbles are partially rounded, but are mostly ob- long. Some of them are from one to three feet in length. These abound for the upper twenty feet of the section on the east side toward the river. One granitic bowlder noticed was about two feet in diameter. On the west side of the eut, away from the river, mastodon-bones were found ina deposit of sand underlying the coarser gravel and pebbles. It was here, about thirty feet below the surface, that Dr. Metz found the paleolithic implement referred to. In October, 1889, Mr. W. C. Mills, president of a local archeological society of some importance at Newcomerstown, on the Tuscarawas River, in Ohio (see map on page 168), found a flint implement of paleeolithic type fifteen feet below the sur- face of the glacial terrace bordering the valley at that place. The facts were noted by Mr. Mills in his memorandum-book at the time, and the implement was placed with others in his col- lection. But, as he was not familiar with implements of that type, and did not at the time know the significance of these gravel deposits, nothing was said about it until meeting me the following spring, when I was led from his account to suspect 646 THE ICE AGE IN NORTH AMERICA. the importance of the discovery. Mr. Mills soon after sent the implement to me for examination, and its value at once became apparent. In company with Judge C. C. Baldwin and two or three other prominent citizens of Cleveland, [ immediately visited Newcomerstown. A cut Fie. 168.—The smaller is the paleolith from Newcomerstown, the larger from Amiens (face view). of the implement is given in the accompanying pages, made from a photograph one quarter the diameter. Beside it is a paleolith which came into my possession from Dr. Evan’s collection in London, with his certification that it is from the valley of the Somme. The two implements as they appear side by side, are in shape and finish the exact —— or cS TC MAN AND THE GLACIAL PERIOD. 647 counterparts of each other. The one from Newcomers- town, however, is made from a local flint which occurs in nodules in the “Lower Mercer” limestone, which is situated in the lower part of the coal-measures, and crops out a few miles from there. ane Ub Fie. 169.—Edge view of the preceding. The implement has upon it the patina characteristic of the genuine flint implements of great age in the valley of the Somme, and is recognized by Professor Haynes, of Boston, as in itself fullfilling all the requirements looked for in such a discovery. The gravel-pit in which it was found is one which for some years has been resorted to by 648 THE ICE AGE IN NORTH AMERICA. the railroads for ballast. Mr. Mills saw the implement as it was projecting from the undisturbed gravel in the fresh exposure, and took it out with his own hands. The surface of the glacial terrace is here thirty-five feet above the prefent high-water mark of the river, and, as already said, the implement was found fifteen feet below the surface. The terrace is one which characterizes the Tuscarawas River everywhere below the glacial boundary, and the illustration upon page 324 might well have been taken from this very spot. Fic. 170.— Face View Fic. 171—Face View. Fic. 172—Diagonal View of the Implement of Sharpened Edge. In 1892 another important discovery was made in the upper terrace of the Ohio River at Brilliant, Ohio. This was a well fashioned flint implement one inch long which was found in place beneath eight feet of cross bedded sand and gravel where there had been no chance for secondary deposition or a land slip. The surface of the terrace was nearly uniform for two miles in length and a quarter of a mile in width at a height of 80 feet above low water, and fifty feet above the present high water mark. Excavations near by to a depth of 43 feet show continuous cross bedded stratification of sand and gravel with clay in small quantities. Mr. Sam Huston, the County Surveyor, and a well known geological collector of highest MAN AND THE GLACIAL PERIOD. 649 reputation saw the point of the implement projecting from the perpendicular bank while the workmen were at dinner, and extracted it with his own hands. The implement was submitted to the joint meeting of the Geological and Anthro- pological sections of the American Association for the Ad- vancement of Science at Springfield Mass., in 1895, where Professor F. W. Putnam, Mr. F. H. Cushing and Miss Alice Fletcher and others all recognized it as an indubitable relic of great antiquity. Its great age was indicated by the patina with which it was covered, and by the fact, instantly recognized by Dr. Cushing, that the form was antique, being intermediate between that of paleoliths and modern Indian implements. Fie. 173.—Section of the Trough of the Ohio at Brilliant. Location of the implement shown by a *. For full accounts see ‘‘Popular Science Monthly” for De- cember 1895, pp. 157-166. The cumulative evidence of these facts is increased with the discovery, by Mr. Hilborne T. Cresson, of Philadelphia, in 1886, of implements of similar type in Medora, Ind. Medora is situated in Jackson county, about one hundred miles west of Cincinnati, and is on the border of the glaciated region in that State. The situation is upon the East Fork of White River, near where it enters the triangular unglaciated portion of Southern Indiana as seen in the map of the gla- cial boundary. The eastern border of this consists of sand- duet tS Raa NS Xx SS No as ! at tata 1 > “os . a x ore ke aS SS a ee ix wes 3 meESS » 7“. % 7] ry aS ae we SARE) Fie. 174,— Paleolith of gray flint, found by Mr. H. T. Cresson, May 1886, at Medora, In- diana, in glacial gravel, eleven feet from surface, in bluff on east fork of White River. (Face view.) (No. 46,145.) (Putnam.) Fic. 175.—Side view of the preceding. (Putnam.} 652 THE ICE AGE IN NORTH AMERICA stone knobs formed by the outcropping of the subearbonit- erous strata, which here dip to the west. The unglaciated area is, therefore, considerably higher than that which adjoins it on the east, and is much cut up into gorges along the drainage lines, and must have furnished a favorite retreat, both for man and animals, during the maximum extension of the ice. . Mr. Cresson, having been called into this locality on busi- ness, and finding that it was near the glacial boundary as I had recently traced it, was led to turn aside for an hour or two to examine a bank of modified drift. While digging with his hunter’s knife under a bowlder of about one hun- dred pounds weight to see if it showed signs of glaciation, he, to his surprise encountered a well-wrought paleeolithie flint implement. Fortunately, a long experience in exploring the gravel-beds in France where paleoliths occur (and, indeed from experience in exploring while a youth a shelter-cave which we will hereafter describe, on the banks of the Dela- ware) had prepared him fully to appreciate the discovery ; Fic. 176.—Section of glacial gravel at Medora, Indiana. in which Mr. Cresson found the palreolith figured in the text. A. is a deposit of soil three feet in depth ; B, modified drift eight feet in depth: D. is probably till ; L, L, layers of alluvium ; C, the bowl- der, under which the implement was found at X. and he remained a day or two until he had thoroughly in- vestigated the surroundings and made further search for im- plements. Such search, however, was not rewarded with suc- cess, since all that he found later were from the surface, and of a neolithic type. According to Mr. Cresson, this palzeo- MAN AND THE GLACIAL PERIOD, 653 lith was found in undisturbed gravel about fifty feet above the flood-plain of the river. The gravel was firmly packed, and the implement was with difficulty extricated from it with his hunting-knife. Above it and the bowider just mentioned were eight feet of gravel and loam, capped by three feet of soil. Mr. Cresson was thoroughly convinced that it would have been impossible for any implement of recent manufacture to have rolled down from the soil above and assume the position it was in with reference to the bowlder. Besides, the imple- ment is of a true palzolithic type, and has the usual marks of age characterizing such implements.* Th Hm oe é es ae \ i 1 AN Fic. 177.1, a, convex surface of a chert implement found at the month of Little Elk River. Morrison County, Minnesota, sapposed to be a scraper. 1.0. profile view of the same.t 2, @, convex surface of « chert implement found at Little Falls. Minnesota. 2, 6. profile view of the same. The figures do not perfectly represent the evident- ly chipped edges. (Winchell.) Another locality especially worthy of attention, in which palzoliths have been found, is at Little Falls. Morrison county, Minnesota, the situation of which ean readily be seen by reference to the map on page 546. The first discover- ies at this point were made as long ago as 1877, and an ac- count of them was given in the “Sixth Annual Geological Report of Minnesota.” + These implements were made from chert and quartz, and were recognized by Professor N. H. * See Mr. Cresson’s report on the subject, in the “ Proceedings of the Boston — Society of Natural History,” vol. xxiv, p. 150 et seq. + This specimen is regarded a finished inplement by Putnam. { Pp. 53-58. 654 THE [CE AGE IN NORTH AMERICA. Winchell as belonging to the age of the glacial deposits which here line the trough of the Mississippi. A little later, Miss France E. Babbitt examined the locality more carefully, and found a large number of additional implements. Her discoveries were first reported in a paper read before the Minnesota Historical Society in February, 1880. A fuller account was presented at the meeting of the Ameri- can Association for the Advancement of Science at Minne- apolis in August, 1883. At that time also the subject was thoroughly canvassed by the numerous geologists present, and a paper was read upon the subject by Mr. Warren Upham, to whose work upon the surface geology of the Northwest we have so often had occasion to refer. To get the whole subject before our readers we can do no better than to append the principal portion of an elaborate paper read by Mr. Upham before the Boston Society of Natural History, on December 31, 1887, which will be the more readily understood by reason of the previous chapters of the present volume detailing the general results of Mr. Upham’s work in that region : The recession of the ice-sheet of the last Glacial epoch in Minnesota seems to be clearly marked by as many as ten stages of halt or readvance, in which distinct marginal mo- raines were accumulated, besides the moraine on the limits of its farthest extent. Six summers of geologic field-work in that State have been spent by the writer chiefly in the examination of its glacial and modified drift, of these mo- raines, and of the beaches and deltas of the glacial Lake Agassiz, which was formed in the valley of the Red River of the North and of Lake Winnipeg by the barrier of the departing ice-sheet. In their bearings upon this subject, my observation and study of that region convince me that the rude implements and fragments of quartz discovered at Little Falls were overspread by the glacial flood-plain of the Mis- sissippi River. while most of the northern half of Minnesota was still covered by the ice, contemporaneously with its for- mation of the massive moraines of the Leaf Hills and with MAN AND THE GLACIAL PERIOD. 655 the expansion of Lake Agassiz on their west side, respectively sixty and eighty-five miles west of Little Falls. This was during the highest stage of Lake Agassiz, and previous to its extension beyond the north line of Minnesota and Dakota. More than twenty lower beaches of this glacial lake have been traced, belonging to later stages in the recession of the ice- sheet, before it was melted so far as to reduce Lake Agassiz to its present representative, Lake Winnipeg. Estimated by comparison with the series of moraines and beaches formed during the glacial recession, the date of the gravel plain at Little Falls appears to be about midway between the time of maximum extent of the last ice-sheet and the time of its melting on the district across which the Nelson River flows to Hudson Bay. | The town of Little Falls is on the east bank of the Mis- sissippl River, in Morrison county, near the geographic center of Minnesota. It is about a hundred miles northwest from St. Paul and Minneapolis, and nearly an equal distance southeast from Itasca Lake. The elevation of Itasca Lake is about 1,450 feet above the sea; of the Mississippi, at the head of the rapids or Little Falls, from which the town derives its name, 1,090 feet ; and at the head of St. Anthony’s Falls in Minneapolis, 796 feet. Following the general course of the river, without regarding its minor bends, its descent from Lake Itasca by Little Falls to Minneapolis averages about two feet per mile, and is approximately uniform along the entire distance. Considered in a broad view, this central part of the State may be described as a low plateau, elevated a few hundred feet above Lake Superior on the east and the Red River Valley on the west., In most portions it is only slightly undulating or rolling, but these smooth tracts alternate with belts of knolly and hilly drift, the recessional moraines of the ice- sheet, which commonly rise fifty to one hundred feet, and in the Leaf Hills one hundred to three hundred and fifty feet above the adjoining country. The bed-rocks are nearly every- where concealed by the drift-deposits, into which the streams have not eroded deep valleys, their work of this kind being mostly limited to the removal of part of their glacial flood- plains. The upper portions of the Mississippi and of its 656 THE ICE AGH IN NORTH AMERICA. chief tributaries, and all the smaller streams throughout this region, flow in many places through lakes which they have. not yet filled with silt nor drained by cutting down their outlets. At Little Falls the glacial flood-plain of the Mis- sissippi is about three miles wide, reaching two miles east, and one mile west from the river. Its elevation is twenty- five to thirty feet above the river at the head of the rapids, which have a descent of seven feet. The Mississippi here flows over an outcrop of Huronian slate, and the same forma- tion is also exposed by the Little Elk River near its mouth, on the west side of the Mississippi three miles north of Little Falls. Veins of white quartz occur in the slate at both these localities, and were doubtless the source of that used by man here in the Glacial period for the manufacture of his quartz implements. | The locality and section of the modified drift, where these worked fragments of quartz were found by Miss Babbitt, and the account of their discovery, are best told in her own words from her paper read before the Anthropological Section of the American Association for the Advancement of Science at its Minneapolis meeting in 1883. I quote as follows : ‘‘Rudely worked quartzes had previously been discovered here by the State Geologist of Minnesota, Professor N. H. Winchell, by whom they had been described and figured in the State Geological Report for 1877. . . . The find reported by Professor Winchell consists of chipped objects of a class generally ascribed to what is called the rude stone age. Of these many appear to be mere refuse, while others are regarded as finished and unfinished implements. The Winchell speci- mens have been assigned, upon geological ground, to a pre- historic era antedating that of the mound-building races, and reaching back to a time when the drift material of the terrace- plain was just receiving its final superficial deposit. It is found that, at intervals, the surface soil of the terrace con- tains these quartzes to a depth of not unfrequently three or four feet. | “The lowest and newest formation at this place is the present flood-plain of the river. It is still in process of depo- sition, being yet subject to partial overflows at periods of y ae =~ — sa ed ek ial emcee ral" Fees MAN AND THE GLACIAL PERIOD. 657 exceptionally high water. In that portion of the town of Little Falls situated east of the Mississippi, this bottom-land is limited on the east by a high, ancient river-terrace, which has here an average elevation of about twenty-five feet above the river. . . . This older terrace, like the present flood-plain, has been spread out by the immediate action of water. . ... Fic. 178.—Quartz implement, found by Miss F. E. Babbitt, 1878, at Little Falls. Minneso- ta, in modified drift, fifteen feet below surface. a, face view; 0, profile view. The bdlaek represented on the cut is the matrix of the quartz vein. (No. 31,323.) (Put- nam.) While occupied in examining the river bank at Little Falls in quest of wrought quartzes, one day during the season of 1879, I had occasion to ascend a slope lying between the new flood-plain and the older terrace, by a path leading through a sort of gap or notch in the latter (three hundred and ten rods, very nearly, or almost one mile north of the east-west road by Vasaly’s Hotel ; ten rods west of the road to Belle Prairie ; and thirty- eight rods from the river). . . . It seemed that at some past period a cut had been effected here by drainage, and that the wash-out thus formed had afterward been deepened by being 658 THE ICE AGE IN NORTH AMERICA. used, now and then, as a wagon-track. In this notch I dis- covered the soil to be thickly strewed with pieces of sharp, opaque quartz. These were commonly of a white color, and ranged in size from minute fragments to bits as large as a man’s hand, and in some instances even larger. There were - many hundreds of these chips visible, scattered over an area Fic. 179—Quartz implement. found by Miss F. E. Babbitt, 1878, at Little Falls, Minne- sota, in modified drift, fifteen feet below surface. a, face view ; 5, side view. (No. 31,316.) (Putnam.) the width of the wagon road, and ten or fifteen yards im length. They were conspicuously unwaterworn, and likewise mostly unweathered, though occasionally a bit was picked up having some one of its surfaces weathered, while fractured or wrought faces appearing upon other parts of it, looked as fresh as if the work of yesterday. On the other hand, the mass of stone rubbish upon and among which the quartzes were strewed is much water-worn, many of the pieces being well rounded, while. none of them are wholly angular. ‘* By continued observations at this locality, I found that many of these quartz chips were brought to light at every suc- ceeding freshet of the season, being washed out of the sand by MAN AND THE GLACIAL PERIOD. 659 descending drainage. Their immense and continually increas- ing numbers seemed to warrant the belief that they had re- sulted from systematic operations of some sort, once conducted, for unknown purposes, upon this particular spot. A portion of the studied specimens subsequently yielded evidence of having received shape from human hands, and therefore it was assumed provisionally that the site of exposure represented a prehistoric workshop. “* Prolonged investigation ensued ; and investigation estab- lished the hitherto unsuspected fact that no quartz chips nor fragments were inclosed in the upper part of the gravel and sand terrace at the notch, nor within a considerable distance at either hand, though they were sought with careful scrutiny. . . . Ultimately it was ascertained that the notch quartzes had dropped to the level at which they were seen from a thin layer of them once lying from ten inches to two feet above it, and subsequently broken up through the wearing away of the sand underneath by drainage. This layer or stratum was still intact on the north and south and partially so on the east, in which direction it had, however, at certain points, suffered some dis- placement by wagoning. It extended in a nearly horizontal plane into the terrace, in the sloping edge of which the notch, opening into its west bank and truncated at its edge, is cut. . . . The quartz-bearing layer averaged a few inches only in thickness, varying a little as the included pieces happened to be of smaller or larger size. The contents were commonly closely compacted, so much so that one might sometimes ex- tract hundreds of fragments, many of them very small ones, of course, from an area of considerably less than a square yard. “The quartz bed, so far as examined, rested upon a few inches of sandy soil, which passed downward into a coarse water-worn gravel, immediately overlying till. Above the quartz chips, stratified gravel and sand extended up to the sur- face of the terrace. The pebbles of the gravel lying directly on the quartz-bearing stratum were small and well rounded, and were noticeably less angular than those of the gravel below. The stratum of quartz chips lay at a level some twelve or fif- teen feet lower than the plane of the terrace-top. ‘* These observations show that the quartz chips were spread 660 THE ICE AGE IN NORTH AMERICA. originally upon an ancient surface that has been since covered deeply by the modified drift which forms the terrace. It will be remembered that the quartz chips and implements discovered by Professor Winchell in this vicinity are contained in the up- per stratum of the terrace-plain ; but the notch quartzes do not occur at the terrace-top, and can not have been derived from it, but are confined strictly to a single stratum of the lower gravels closely overlying the till. Hence the two sets of objects can not be synchronous, though they may have been produced by the same race at different stages of its existence. The notch quartzes must, of course, be older than those de- scribed. by Professor Winchell, by at least the lapse of time required for the deposition of the twelve or fifteen feet of modi- fied drift forming the upper part of the terrace-plain, above the quartz-bearing, stratum.” This description by Miss Babbitt shows that these imple- ments and fragments of chipped quartz occurred in a well-de- fined thin layer in the modified drift forming the glacial flood- plain of the Mississippi River, as shown in the section which I have drawn (see the following figure). I have examined the w. Stratum containing dified Dri Ja E. ie 4 Caste che pene Terrace of Moc Legied Drif' 1 a aes ow epooenas = == = terraces and plains of this valley drift from St. Paul and Min- neapolis to Brainerd, some twenty-five miles north of Little Falls, and find them similar in material and origin with the modified drift terraces in the valleys of the Merrimack, Con- necticut, and other rivers in New England. These water- courses extending southward from the region that was covered by the ice-sheet became the avenues of drainage from it during its retreat. A part of the drift which had been contained in the lower portion of the ice was then washed away by the streams formed on the ice in its rapid melting and was depos- ited as modified drift, forming layers of gravel, sand, and fine silt, in the valleys along which the floods supplied by this melting descended toward the ocean. Along the Mississippi a ice cael la Ne = a a ai = . td 4 INDEX. Hanover, N. H., 345. Hartwig, G.,on glaciers of Magdalena Bay, 107. Haughton, Professor S., on transported bowlders in the Hudson Bay region, 245. Haverhill Mass., 338. Hayes, I., explorations of, in the Saint Elias range, 30; in Greenland, 86, 89 et seq. Haynes, Professor H. W., on palsoliths, 619 et seg., discovers paleoliths, 628, 629. Helland, Mr. A., 445; on rate of movement of Greenland glaciers, 80, 82, 202; on slope of Jakobshavn glacier, 201; on ero- sion in Greenland, 255; in Scandinavia, 260; on depth of drift in Germany and Russia, 260, on formation of cirques, 274. Hennepin discovers Falls of St. Anthony, Bar Herschel, Sir John, 500. Hice, Mr.,309. Hicks, Professor, on Raccoon Creek, 56¢, 565. Higginsport, Ohio, 170. Highland county, Ohio, 170, 591, 602. Hilgard, Professor E. W., 513; on loess, 410, 411, 415; on depression in Mississippi Valley, 410, 411. Hillsborough county, N. H.., 330. Himalayan Mountains, 108, 365, 427; Qua- ternary uplift of, 510, 513. Hind, Professor, on glacial drainage, 335. Hinde, Dr. G. J., 584. Hippopotamus, 690. Hitchcock, President E., on size of bowl- ders, 236 et seqg.; on the Richmond train of bowlders, 239; on kames in Andover, Mass., 339. Hitchcock, Professor Charles, 504; on ele- vation of bowlders, 194, 246, 247; on depth of ice, 202; on lenticular hills, 281, 283, 290, 292; on buried kame in Hano- ver, N. H., 345; on Croll’s theory, 574. Hocking River, 300, 323, 326. Holkham Bay, 27. Holmes county, Ohio, terminal moraine in, 169; bowlders in, 242; glacial terraces in, 326. Holst, N. O., 239, 586; on the Greenland glaciers, 100, 101. Hopkins, Professor W., 497. Horse, 436, 438, 690. Horseshoe Fall, Niagara, recession of, 540. Hudson Bay,199, 246, 354, 356, 607. Hudson Bay and Strait, raised beaches of, 504. 7ol Hudson River, 136, 228, 305, 329, 352, 357, 358; submarine fiord of, 305, 306, 502, 503. Hugh Miller Glacier, 73. Humboldt Glacier, 91 et seq. Humboldt Range, 177. Hunt, Professor Sterry, on preglacial ero- sion, 261. Hunter, Captain,on depthof Muir Glacier, 45. Huntingdon Mountain, 148. Hurricane Creek, W. Va., 381, 382. Hutton, Captain, 510. Icebergs, on coast of Alaska, 35; from Muir Glacier, 40, 50, 51, 67; from Greenland, 85, 95; in Straits of Magellan, 111; of the Antarctic Continent, 112, 114 et seq.; for- mation of, 235. Iceberg theory, 126, 133, 143, 183, 200 e¢ seq., 240. Ice, characteristics of, 1 et seg., 232; is but compressed snow, 6. Iceland, 107, 430, 441, 582. Ice-pillars, 10, 49, 70. Ice-sheet, advance of, 313; retreat of, 139, 150, 221, 314, 315, 316, 348, 349, 352, 387 et seq., 398, 558, 623, 654, 661; causing de- pression of the earth’s crust, 416, 417, 497,500, 510; probably due to elevation, 497, 509, 511. Icy Bay, 30. Tllecillewaet Glacier, 13, 14. Illinois, driftless area of, 134; depth of ice in, 201; glacial boundary in, 170-172, 525, 526, 528; bowlders iu, 243; depth of drift in, 257; loessin, 415, 587; strie in, 591; buried wood in glacial deposits in, 601. Illinois River, 314, 354. Illinoisan deposits, 223, 590. Implement-bearing gravels in Europe, 616, 624, et seq.; at Trenton, N. J., 630 et seq., 669, 706; at Madisonville and Loveland, Ohio, 644 et seq., 669, 706; at Medora, Ind., 649 et seq., 669, 706; at Little Falls, Minn., 656 e¢ seq., 669, 706; at Claymont, Del., 669 et seq. India, 487, 510, 513, 516; glaciers of, 108,365; Permian glacial deposits in, 485, 516. Indian Ridge in Andover, Mass., 339. Indiana, glacial boundary in, 170, 207, 525, 526, 528; bowlders in, 243, 652; depth of drift in, 257, 601, 602; wells in, 300, 601, 602; loess in, 415, 587; strise in, 591; vege- table deposits in, 601, 602, 603; palso- lithic implements in, 649 et seq. Indianapolis, Ind., 170. 752 Insects, migrations of, during the Glacial period, 438 e¢ seg.; Alpine species of but- terflies upon the White Mountains, 438. Interglacial deposits, how preserved, 295 et seq.; theory of, 576; in Ohio, 592, 598; in Minnesota, 605, 607. See Vegetable Remains in Glacial Deposits. Interglacial epoch, evidence favoring, 575 et seq., 607 et seq.; duration of, 512, 562, 563; probable causes of, 497, 512. Interglacial man, in France, 616, 623; in England, 616, 624; at Trenton; N.J., 625 et seq.; at Madisonville and Loveland, Ohio, 643 et seq.; at Medora, Ind., 649 et seq.; at Little Falls, Minn., 653 et seq.; at Claymont, Del., 669 et seg.; in Nebraska, 675; in Tuolumne county, Cal., 689 et seq.; Le Conte on, 688 et seg., 699; Daw- kins on, 699. Interglacial migrations from Africa to Europe, 507. Interior moraines, 140, 204, 207 et seq. Interior, probable condition of the earth’s 498, 502, 518. Towa, 362, 525, 528, 661; driftless area of, 134, 414; depth of ice in, 201; bowlders in, 243; lakes in, 361; loessin, 413-416; veg- etable deposits in, 605. Iowan deposits, 223. Treland, 11, 339, 360, 361, 445, 446, 448. Trish Sea Glacier, 446, 449-451. Isblink, 79. Italy, xlaciation in, 486, Jackson county, IlJ., 171, 172, 243. Jackson county, Ind., 170, 601, 649. Jackson, Dr. Sheldon, on depth of Muir Glacier, 45. Jackson, Mr. C. T., cited, 331. Jacobus Creek, 352. Jakobshavn Glacier, 78, 80; rate of dis- charge, 82, 85; slope of, 201,202; subgla- cial streams of, 255; glacial damsof, 366. Jamaica, post-glacial elevation of, 507. James, Professor Joseph F., on buried channels in the Ohio, 301. James River, Dakota, 214, 215, 336. Jamieson, T. F.. 498, 500, 501. Japan, flora of, 423, 426, 431, 4382, 434; dust- fog in, 409. Jefferson county, Ind., 602. Jennings county, Ind., 601. Jensen, A.D., 80, 81, 201. Johns Hopkins Glacier, 73. Johnson, Dr. L., on drumlinsin New York, 286, 291. ‘ Johnsonville, Pa., 352. INDEX. Jones, Dr., 701. Jtivdliarsuk Glacier, 79. Juneau, Alaska, 27, 59. Kamchatka, 480, 441. Kames in Rindge, N. H., 330; in Winchen- don, Mass., 330; chapter on, 339-354; Ed- ward Hitchcock’s description of, 339; J. Geikie’s description of,339; structure of, 340; compared with terminal moraines, 340; theory of, 11, 16, 66, 341; forming at the Muir Glacier, Alaska, 66, 342; sys- tem of,in New England, 342; buried, 345; - in the Connecticut Valley,345; Dana on, 346, 347; at Stroudsburg, Pa., 348, 352; deltas of, 348, 352; in Rangely Lakes, 349; location of, prognosticated, 349, 350; of backward drainage, 350 et seq.; in Schoodic Lake, 350; near Ossipee Lake, 351; near Portland, Pa., 352; near the Finger Lakes, N. Y., 352; in Ohio, 353; absence of, in the Northwest, 353; com- pared to a skeleton, 354. Kanawha River, 300, 309, 379, 381, 383, 604. Kane, Dr., explorations of in Greenland, 86, 87, 92 et seq.; on formation of icebergs, 2352 Kansan drift, 158, 154, 158, 224, 585, 588. Kansas, glacial boundary in, 172; loess in, 414, 415. Kansas City, Mo., 172, 412. Kansas River, 172, 414. Karajak Glacier, 78. Keewatin ice center, 585, 586. Kelley’s Island, 262. Kenai Peninsula, glaciers on, 36. Kennebec River, 221, 342. Kenton county, Ky., 367. Kentucky, 170, 201, 243, 367, 368, 375, 385, 386, 487. Kettle-holes, defined, 11; formation of, in front of Muir Glacier, 57, 66; in Ply- mouth county, Mass., 139, 360; explan- ation of, 143; resemble sink-holes, 148; formation of, 144, 204, 359, 360, 572; on Pocono Mountain, 148; near Ack- ley, Pa., 150; in Ohio, 168, 169, 597; abun- dance of, in terminal moraine, 204, 360, 361; Professor Koons on, 204 et seq.; direc- tion of longer axis of, 204, 205; in New England, 360, 361; age of, estimated, 572 et seq.; near Freehold, Pa., 598. Kettle Range, Wis., 134, 144, 207, 211, 212, 221, 361, 415, 527. ' King, Mr. Clarence, 498; on glaciers of Mount Shasta, 15 et seq.; discovers ter- minal moraine, 134, 221; report on forti- .; i x —e— Le ail INDEX. eth parallel, 177 et seg.; on Yosemite | Valley, 271; on drumlins, 288; on dust- fogs, 409. Kinnahan on drumlins, 290. Kittatinny Mountain, 133, 146, 228; eleva- tion of bowlders on, 196, 247 et seq.; ero- sion on, 260. Knox county, Ohio, glacial boundary in, | 169; buried channel in, 301; terraces in, 326. 3 Koldewey, Captain, on east coastof Green- | land, 98. Koons, Professor B. F., on kettle-holes, 204 et seq. Kryokonite defined, 9. Kuro-Siwa, 495. Kurtz, Mr. M. A., 701. Kuskovim River, 36. Labrador, depth of ice in, 202; insects in, | 439-441; acenterofshow-fall, 527,585,586. Lake Agassiz, 401 et seq., 559, 654, 655; delta terrace in, 334; beaches of, 401, 404 e¢ seq., 500, 543, 545, 655, 664; vegetable deposits in bed of, 603, 607; Upham on, 401 et seq., 543 et seq. Lake Allegheny, 158-160. Lake Arikaree, 336. Lake Bonneville, 336, 609, 611, 622, 704. Lake Calhoun, 555. Lake Champlain, 358, 363. Lake Chautauqua, 308, 363. Lake Erie, 201, 354, 395, 542; islands of, 262 | et seq.; preglacial outlet of, 303 et seq., 536; glacial drainage of, 314, 317;formationof, 356 et seq., 363; beaches of, 545. Lake Harriet, 555." Lake Huron, 201, 367, 542; preglacial out- let of, 304 et seq.; glacial drainage of, 314, 317; origin of, 356, et seg. Lake Humber, 448, 451, 452. Lake Itasca, 655. Lake Lahontan, 608 e¢ seq., 612. Lake Lesley, 156. Lake Lindeman, 29. Lake Michigan, 211, 306, 354, 361, 525, 528, — 665; preglacial outlet of, 305, 306; glacial drainage of, 314; origin of, 356 et seq.; | dunes of, 545; post-glacialerosionin, 571. Lake Minnetonka, 211, 212, 361. Lake Mono, Cal., 273, 607. Lake Nipissing, 542. Lake Ontario, 148, 395, 398, 536, 587; pre- glacial drainage of, 304 et seq.; origin of, 356 et seq. Lake ridges, around Erie, 395, 397; around Ontario, 395. 753 Lake Superior, 199, 201, 212, 213, 325, 367, 528, 664; preglacial outlet of, 305, 306; glacial drainage of, 314; origin of, 356 et seq,; Vicinity of, acenter of snow-fall, 527. Lake Traverse, 316, 354. Lake Washington, 181. Lake Williams, 153, 154. Lake Winnepesaukee, 221, 363. Lake Winnipeg, 654, 655. Lakes formed in mountain-building, 510, Pe: ‘Lamoile River, 347. Lamplugh, G. W., 505, 587. Lang, Mr. C., 105. La Pérouse, 42, 43. Lattas, Ohio, 602. Laurentian lakes, basins of the, 500, 501. Laurentian Mountains, 199, 244, 246, 259, 357, 527. Lava-beds in western United States, 417, 418. Lawrence county, Pa., 326. Lawrence, Mass., 348, 350. Lawrenceburg, Ind., 326, 327. Le Conte, Professor Joseph, 498, 501, 507; on succession of glacial epochs, 490; on deep placer deposits in California, 688 et seq. Lebanon Mountains, glaciers of, 612 e¢ seq. Lehigh River, 325, 637. Lehigh Water-Gap, 197. Lenox, Mass., train of bowlders in, 239, 240. Lesley, Professor J. P., on depth of the ice, 195-197; on elevation of bowlders, 195, 248 et seq.;on depthof drift in, 259; onerosion in northern Pennsylvania, 260; on Cin- cinnati ice-dam, 371. Lesquereux, Leo, on rate of accumulation of peat, 594 et seq.; cited, 690. Leverett, Mr., on the Kanawha, 309; corre- lates Alpine episode with American, 580; on age of Kansan till, 588. Lewis, Professor H. Carvill, 619, 628, 629, 637; begins the survey of Pennsylvania, 135, 148, 149; discovers moraine on Pocono Mountain, 147;0n transportation of bowl- ders, 197, 247 et seq.; on depth of ice in eastern Pennsylvania, 197; on erosion in nortbern Pennsylvania, 260; reports drumlins in Pennsylvania, 287; on mar- ginal kames in eastern Pennsylvania, 352; on glaciated area of Great Britain, 448, 449 et seq.; on kettle-hole at Free- hold, Pa., 598; the Philadelphia red gravel and brick-clay of, 637, 671. Lewiston, Me., 343. Licking county, Ohio, 169, 564, 603. 154 _ INDEX. Licking River, Ky., 310, 367, 385-387. Licking River, Ohio, 300. Lindenkohl, A., 502. Little Falls, Minn, 619, 653 et Seq. Little Falls, N. Y., 329. Little Miami River, 327, 643, 644, 645. Little Sandy River, 19. Little Scioto, 309. Lituya, 42, 43. Lituya Bay, Alaska, 74. Llama, 436, 437. Loess, 172, 256, 685; chapter on, 407-420; Pumpelly on, 407, 408; composition of, 407, 412; in China, 408, 513; Baron Richt- hofen on, 408; in Europe, 410, 512; in America, 410; Hilgard on, 410, 411; alti- tude of deposits of, 410, 413, 416; Cham- berlin on, 412; theory of, 413 et seq., 588; extent of subsidence indicated by, 413, 416; Upham on, 415; earthworms and the, 418; in Ohio, 644. Logan, Sir William, 570. Long Island, terminal moraine on, 140, 144, 204, 207; bowlders on, 238; over-wash gravel on, 349; kettle-holes on, 360. Long Level, W. Va., 381, 604. Long, Mr., on Paint Creek, 562. Lorain county, Ohio, 395. Lorange, on cirques, 274, 276. Louisville, Ky., 170, 300. Loveland, Ohio, palzolithic implements found at, 643, 645. Lowell, Mass., 343-345. Lubbock, Sir John, 624. Luzerne county, Pa., 148. Lycoming county, Pa., kettle-holes in, 149; terminal moraine in, 149; bowlders in, 242. Lycoming Creek, 149, 325. Lyell, Sir Charles, 497, 509; observations of, in Nova Scotia, 126,127; on Richmond train of bowlders, 239, 240; theory of the cause of the Glacial period, 495; principle of uniformity, 533; on rate of recession of Niagara Falls, 539, 706; on antiquity of man, 616, 624. ; Lynn Canal, Alaska, 27, 43, 59, 61, 188. Machias River, 342, 343. Mackenzie River, 246. Mackintosh, Mr., 570. Macoun, Professor, cited, 569. Madison, N. H., bowlder in, 238. Madisonville, Ohio, paleolithic imple- ments found at, 643, 644. Magdalena Bay, 107. Maine, 137, 441, 665; depth of ice in, 194, 195; bowlders in, 247; depth of drift in, 259; absence of drumlins of large size in, 286; kames in, 349-351, 353; lakes in, 361; marine beds overlying glacial drift, 504. Malaspina Glacier, 30, 31, 32, 606. Mammoth, 438, 586, 690. Mammoth Cave, 229. Man, antiquity of, in America, 438, 534, 639-640; and the Glacial period, chapters on, 616-709. . Manchuria, 427, 432. Mandan, 430. Manitoba, 335, 354. Manomet Hill, 139. Marginal drainage, 175, 333 er seq., 351, 352. Marietta, Ohio, 323, 327. Marine shells, elevation of, in glacial de- posits in Wales, 453; near Boston, 453. Marr, Mr. J. E., on erosion in Greenland, 256, on glacial dams, 366. Marshall, Ohio, 602. Martha’s Vineyard, 187, 144, 203, 237. Martinsville, Ohio, 309. Marvine Glacier, 32. Mary Minturn River, 92. Massachusetts, terminal moraines of, 137, 139; depth of ice in, 195; depth of drift in, 259; transported bowlders in, 238, 239, 240; drumlins in, 283-285, 288; kames in, 330, 353; kettle-holes in, 360, 361, 575; lakes in, 361. Mastodons, 436, 437, 586, 639, 645, 675, 690. Mattawa River, 542, 543. Mattawamkeag, Me., 343. Mattawan, Can., 542, 543, 548. Mattison, Mr., 700, 761. Mattmark, Sea, 365. Maumee River, terminal moraine in valley of, 207 et seq., 266. McConnell, Mr. R. G., on the Cypress Hills, 199, 200; on depth of drift in Brit- ish America, 259. McGee, Mr. W J, 512; Columbia period of, 613, 639, 671. McKeesport, Pa., 379. Medial moraines, east arm of Kettle Range, a, 211; Coteau des Prairies, a, 214. Medial moraines, formation of, 9; of Muir Glacier, 48, 49, 236; of White River Glac- ier, 22. Mediterranean Sea, 433. Medlicott and Blandford on signs of glac- iation in India, 484, 485, 510. Medora, Ind., paleolithic implements found at, 649 et seq. Megalonyx, 436. * Ady a INDEX. Megatherium, 436. Melville Bay, 92. Mer de Glace of Switzerland, 3, 4, 10; of Greenland 87, 89, 90. Merjelen Sea, 364. Merrimack River, 330, 331, 348, 344, 350, 660. Mesozoic era, absence of glacial epochs during the, 515, 518. Metuchen, N. J., 142. Metz, Dr. C. L., finds palzolithic imple- ments at Loveland and Madisonville, Ohio, 619, 642, 644, 645. Michigan, buried channel in, 306; salt deposits of, 464. Middle Bass Island, 262. Migrations of plants and animals, 422, et seq., 506, 513, 665. Milan, Ind., 602. Milk River, 334. Mill Creek, 300, 301, 393, 643, 644. Minneapolis, Minn., 211, 212, 303, 315, 361, 552, 554, 655, 660. Minnesota, driftless area of, 134; depth of icein, 201; terminal moraines in, 211-213, 525, 613, 655, 661 et seq.; varieties of drift in, 213; depth of drift in, 258, 555; drum- lins absent in, 287; waterfalls in, 303, 552 et seq.; delta terraces in, 334; occasional kames in, 353; lakes of, 361; loess in, 416; preglacial man in, 438, 653 et seg.; post- glacial erosion in, 552 et seq.; buried chan- nel in, 553 et seg.; wells in, 555, 605, 607; vegetable deposits in, 605; palzolithic discoveries in, 619, 653 et seq. Minnesota River, 214, 315, 316, 336, 354, 361, M362, 554-556, 558, 559. ississippi River, 136, 171, 203, 354, 357, 358, 361, 389, 417, 527, 634, 655, 656, 665; preglacial channels of, 311; preglacial erosion of, 228, 298, 315, 496; loess of the valley of, 256, 410 et seq., 415; glacial drain- _ age of, 313, 314; terraces on, 315, 415, 558, 654; post-glacial erosion in, 315, 552 et seq., 665; rate of transportation by the, 562. Missouri coteau in British America, 135, 176, 217 et seq.; source of, 244. Missouri coteau in Dakota, 215, 217, 332, 333. Missouri, glacial boundary in, 172, 415; bowlders in, 243. Missouri River, 172-175, 215, 220, 243, 244, 320, 321, 336, 414-416. Mohawk River, 195, 228, 303, 305, 314, 319, 352, 353, 587; ice-dam in, 398, 536, 539. Mohawk Valley, 542. Mohegan Rock, Conn., 238. 750 / Mono county, Cal., 13, 222. Monongahela River, 300, 308, 370, 372, 377, 378, 384, 604; ice-dam in, 391-393. Monroe county, Pa., terminal moraine in, 146, 148; depth of ice in, 195, 198; buried channels in, 311. Montana, former glaciers in, 13, 176;glacial boundary in, 133, 175; bowlders in, 243. Mont Blane, 104, 109. Montgomery county, Ohio, organic re- mains in glacial deposits in, 592, 593; depth of till in, 592. Montreal, marine beds overlying glacial drift, 504; depression at, 542. Moose, 675. Moraines, formation of, described, 9. Moraines of retrocession, 57, 207, 222, 223. Moreau River, 174, 175. Morgan county, Ind., 601. Morgantown, Ind., 601. Morgantown, W. Va., 370, 377, 378, 603. Morris county, N. J., 241. Morrison county, Minn., 653, 655. Morse Glacier, 72. ; Moulins defined, 9; on Mount Tacoma, 22; on Muir Glacier, 48. Mountain-building, probably correlated with epochs of glaciation, 499, 502, 507, 509 et seq. Mount Baker, 23, 180, 192. Mount Crillon, 42, 43, 68. Mount Dana, 15. Mount Desert, Me., 137, 194, 195. Mount Fairweather, 35, 42, 43, 68. Mount Hood, 19, 192. Mount Jefferson, 19. Mount Katahdin, Me., 195, 247, 348, 441. Mount Kelertingouit, Greenland, 85, 86. Mount McKinley, 36. Mount Lyell, 15, 269, 273. Mount Rainier. See Mount Tacoma. Mount Shasta, 15 et seq., 192. Mount St. Elias, 30, 34-36, 42. Mount Tacoma, 21, 136, 180, 192, 193. Mount Washington, 194, 246, 439-441. Mount Wrangel, 36. Mower county, Minn., 605. Mud River, W. Va., 381. Muir Glacier, cross-section of, 4, 39; kames forming in, 11, 66, 342; discovery of, 39; chapter on, 40-74; accessible to tourists, 40; difficulties of measurement, 41, 52; surrounding mountains, 41-43; vegeta- tion in the vicinity of, 41, 57; view of, 42; former extension of, 43, 59, 189; relation to Glacier Bay, 45; width of, 45; terminal moraine of, 45, 57; transported bowlders 756 INDEX. on, 45, 236; thickness of, 47, 234; slope of, 47; extent of, 47; moulins of 48; nunataks of, 47, 79, 189; medial moraines of, 43, 49, 56, 236; ice-pillars of, 49; surface of, 50; front of, 50; icebergs from, 50, 51, 67; subglacial streams of, 51, 55, 57, 61, 66 ez seq., 342; buried forests near the, 53, 61 et seq., 233, 592; velocity of, 55, 80; daily discharge of, 55, 82; view of surface of, 56; kettle-holes in front of, 57, 58, 66, 144, 204; retreat of, 57; former extent of, 59; Van- couver on, 59; view of stumps of cedar trees 62, 63; movement over gravel de- posits, 66, 233; sediment, 68; temperature near, 69; Professor Reid on, 71, 72. Muir Inlet, 41, 45, 189, 192; list of plants” about, 69. Muir, Professor, explorations in Alaska, 39, 68. Muskingum River, 300, 314, 323, 327. Musk-ox, 675. Mylodon, 436. Naaman’s Creek, 675. Nampa image, 701 et seq. Nansen, Dr. F., on Greenland, 98. Nanticoke, Pa., 332. Nantucket, 137, 139, 203. Natal, Permian glacial deposits in, 516. Naushon, 204 e¢ seq. Nebraska, glacial boundary in, 172; bowl- ders in, 243; loess in, 411, 414, 415, 587. Nelson River, 313. Nevada, former glaciers in, 176; salt lakes in, 607. Névé field, in Greenland, 88; on the Sierra Nevada, 18, 179, 273 ‘New Alexandria, Ohio, 168. Newark, Ohio, 169, 326. Newberry, J. S., 487; on glaciers of Cascade Range, 19; on depth of glacial deposits, 257; on glacial erosion, 261; on formation _of the Great Lakes, 262, 356 e¢ seq.; on buried channels in Ohio, 300, 301; on pre- glacialdrainage through Ontario, 305,306. ‘New Burlington, Ohio, 602. Newburyport, Mass., 343. Newcomb, Professor Simon, 192, 476. Newcomerstown palzolith, 645 et seq. New England, 139, 358, 398, 487, 523; glacial drainage of, 136; kettle-holes in, 139, 360, 361; depth of ice in, 194, 195, 201; termi- nal moraines of, 134, 203, 361; transported bowlders in, 237, 238, 239, 240; depth of drift in, 259; glacial drainage in, 330, 331, 342, 343; kames in, 330, 343 et seq.; lakes in, 361, 363; peat-bogs, 360. New Hampshire, 139,665; depth of icein,194 transported bowlders in, 194, 237, 246; terminal moraines in, 221; depth of till in, 259; drumlins in, 283, 285, 288; delta terraces in, 330; kames in, 340, 341; lakes in, 361, 363, New Harmony, Ind., 170, 326. New Jersey, terminal moraine in, 133, 134, 140, 142, 144, 151, 206; depth of ice in, 198; transported bowlders in, 241; lakes in, 363; interglacial man in, 438 palzolithie dis- coveries in, 619, 620, 625 et seq. New Mexico, 274. New Richmond, Ohio, 367. New York, 317, 398, 665; glacial boundary in, 133, 525; depth of ice in, 195, 261; ter- minal moraine in, 149, 206; bowlders in, 242; drift hills in, 286; buried channels in, 305, 306, 307, 308; kames in, 352, 353; lakes in, 363; lake ridges in, 395; salt de- posits in, 463. New York Central Railroad, terraces along the, 329. New York City, 357, 398, 502. New Zealand, glaciers in, 104, 112, 488, 510; cirques in, 274. Niagara gorge, length of, 299, 353, 376, 536; a glacial chronometer, 299, 536 et seq., 548-552; erosion of, 542; recession of at standstill, 543. Niles, Professor, on erosion by the Aletsch Glacier, 231, 232. Niobrara River, 172. Nisqually River, 21. Nittany Valley, Pa., 229, 230. No Man’s Land, 137. Nordenskiéld, A. E., 518; on influence of meteoric dust,9;expedition to Greenland, 75 et seq.; on subsidence of Sahara, 433. Northampton county, Pa., terminal mor- aine in, 146. North Bass Island, 262. North Bay, Can., 548. North Bend, Ohio, 170, 367. North Carson Lake, Nevada, 607. Northern Pacific Railroad crosses the gla- cial boundary, 174, 175, 213. North Sea Glacier, 446, 449. Norway, glaciers of, 104, 106, 110, 232, 234, 445; erosion in, 278; depth of ice in, 447. Nova Scotia, 126, 127; absence of Quater- nary marine beds in, 504. Nova Zembla, 107, 488. Nunataks, 47, 79, 189, 254, 366. Oahe, Dakota, 174. Oberlin, Ohio, 565. j INDEX. Ocean lowered to supply ice, 503; raised by | ice attraction, 503. Ohio, fringe in, 167; terminal moraine in, 168 et seq., 198, 372; kettle-holes in, 168, 169; wells in, 168, 169, 257, 258, 602; bowl- | ders in, 242, 243; depth of till in, 257, 258, 592, 593, 598-600; preglacial erosion in, | 299, et seqg.; buried channels in, 300 et seg., | 304, 644; glacial drainage in, 314; absence | of terraces in unglaciated part, 323; kames in, 353; limit of glacier in, 357, 358; glacial erosion in, 358; glacial boundary in, 367, 525, 526; lake ridges | in, 395 et seq.; interglacial man in, 438, | 640 et seqg.; post-glacial erosion in, 560; | strie in, 591; vegetable deposits in, 592, . 593, 598 et seg., 602, paleolithic implements in, 642 et seq. 603; loess in, 644; Ohio River, 170, 208, 228, 353, 358, 634, 643; | glacial drainage of, 314, 353; preglacial | drainage of, 309, 310; occupies a pregla- | cial gorge, 299 et seqg., 384; glacial dam | in, 366, et seq; terraces on, 370 et seq. Oil Creek, Pa., 326. Okhotsk-Kamchatkan region, flora of, 441-444, Olympian Mountains, 180, 192. Ontario, Can., 665. Oregon, 222, 417, 426; glaciers in, 19, 177, | 191, 192, 607. Oregonia, O., limestone bowlder in, 239. Orton, Professor Edward, on bowlder at Oregonia, O., 239; on depth of till, 257; on buried channels in Ohio, 302; on | Paint Creek, 560; on vegetable deposits in Ohio, 592, 602. Osage River, 321. Oscillations of land and sea, 497 et seq. Ossipee Lake, 351. Ottawa Valley, 542, 543. Over-wash gravel, 204, 348 et seg. See | Delta Terraces and Kames. Owen, Miss, finds implement at St. Joseph, Mo. Oxford, Ohio, 600. Oysters, 586. Packard, Prof. A. S., 504; reports trans- ported bowlders on Mount Katahdin, Me., 247. Paint Creek, 326, 372 et seq., 384, 560 et seq. Palezoliths, characteristics of, 616 et seq.; Haynes on, 619 e¢ seg.; oceurrence of, in glacial gravels in France and England, 623-625; at Trenton, N. J., 625 et seq.; at Madisonville and Loveland, Ohio, 642 et seq.; at New Comerstown, Ohio, 645 757 et seq.; at Medora, Ind., 649 et seg.; at Little Falls, Minn., 653 et seg.; at Clay- mont, Del., 669 e¢ seq. Palestine, Ohio, 168. Panama, Isthmus of, Quaternary oscil- lations of, 568. Paris Crossing, Ind., 602. Parker Creek, 15. Parker, Pa., 604. Passadumkeag, Me., 343. Patagonia, 104, 488. Patterson Glacier, 27. Patton, Rev. J. L., 40. Payer, Mr., on east coast of Greenland, 98. Peabody Bay, 92. Peary, R. A., 99, 100. Peat-beds, formation of, 360, 594 et seq.; age of, 573, 574, 597, 598; in New England, 360; in southern Ohio, 592, 593; in Penn- sylvania, 598; in Minnesota, 605. Peekopee Lake, 334. Pelee Island, 262. Pelican Lake, 334. Pembina River, 333, 334. Penck, Dr. A., on cirques, 275, 278; on Al- pine glaciers, 459; on oxidization, 580. Pendelton county, Ky., 170. Pennsylvania, 436, 487; terminal moraines in, 133, 146 et seq., 206, 376, 526; kettle- holes in, 148, 598; fringe in, 153, 167; trans- ported bowlders in, 241, 242; terraces in, 150, 370-372, 375, 379, 384; depth of ice in, 195 et seq.; direction of strize in, 248, 249; depth of till in, 259; glacial erosion in, 260; wells in, 260, 604; few drumlins in, 287; buried channels in, 307, 308, 332; kames in, 348, 352; marginal drainage in, 352; vegetable deposits in, 604. Penobscot River, 342, 343. Percival on drumlins, 285. Permian glacial epochs, 484, 485, 509, 515, 518. Perry county, Ohio, 169, 326. Perth Amboy, N. J., 140. Perthes, Boucher de, palezolithic discover- ies of, in France, 574, 623, 624. Peru, post-glacial elevation of, 507. Petermann Peak, 98. Philadelphia, 671; and vicinity, preglac- ial elevation of, 502. Philadelphia red gravel and brick-clay, 634 et seq., 636, 671, 673. Pickaway county, Ohio, 169. Pike county, Ohio, 372 et seq., 374. Pike county, Pa., 205. Pilgrim Fathers, 137. 758 Pipestone county, Minn., 353. Piscataqua River, 342, 352. Pittsburgh, Pa., 370, 375, 384. Plainfield, N. J., 140, 142. Plains, the Western, uplifted in the Qua- ternary period, 502. Plants, in the clay deposits of the Monon- gahela, 392; migrations of, during the Glacial period, chapter on, 422-444; pre- glacial distribution of, 422, 430; Professor Asa Gray on, 422 et seq.; resemblance of, in Japan and eastern North America, 423, 432; manner of migration of, 424; of the Pacific coast of North America, 426, 435; of Japan and North China, 427, 434; of Europe, 427; of the Tertiary period, 428, 430; effect of Glacial period upon, 429, 431, 433; the birthplace of, 432; on oceanic islands, 436; list of, common to the Okhotsk-Kamchatkan region and North America, 441-444. Platte River, 172, 177, 414, 416. Plum Creek, Ohio, 565-568, 575. Plum Island, 140. Plymouth county, Mass., 137, 139, 360. Plymouth Rock, Mass., 238. Pocatello, Idaho, 337. Pocono Mountain, terminal moraine on, 133, 146, 148, 526; depth of ice over, 198; bowlders on, 241. Pohlman, Dr., on the Niagara gorge, 540. Point Pleasant, Ohio, 36. Point Wilson, state of Washington, 182. Polar ice-cap, 179, 192. Pomp’s Pond, Andover, Mass., 572: et seq. Port Foulke, 89, 92. Port Jervis, 314. Port Townsend, 180, 182. Portland, Me., 349. Portland, Ore., 21, 39, 40, 135. Portland, Pa., 352. Post-glacial erosion, 590; in gorge of Niag- ara, 269, 536 et seq.; of Mississippi, 315, 552 et seq.; of Paint Creek, 561, 562; in Rac- coon Creek, Ohio, 564, 565; in Plum Creek, Ohio, 565-568; in Lake Michigan, 571. Post-glacial oscillations of level, 504-506. Pot-holes, in Grafton county, N. H., 331; in Lackawanna county, Pa., 332; at Mat- tawan, Can., 543. Potomac River, 671. Potter county, Pa., terminal moraine in, 149; depth of ice in, 195. Powell, Major J. W., 498. Pratt, Archdeacon J. H., 497. Precession of equinoxes, 467, 468, 509, 511. | INDEX. Preglacial climate, 463. Preglacial drainage, chapter on, 298-312; lower levels of, in the Ohio Valley, 300 et seq.; erosive effect of, 300; buried chan- nels of, 301 e¢ seqg.; in the vicinity of Cin- cinnati, 301; in central Ohio, 302; in the vicinity of Minneapolis, 303; between Lakes Erie and Ontario, 303; in southern tributaries to Lake Erie, 304; between Lakes Huron and Ontario; 304; in the Mohawk Valley, 305; in Illinois, 306; in western Pennsylvania and western New York, 307, 308; in eastern Pennsylvania, 311; in the Province of Quebec, 312. Preglacial elevation, 502. Preglacial erosion, extent of, 226 et seq., 261, 279, 298 et seq., 353, 540, 542, 562, 564. Preglacial terraces, 372. Preglacial topography, 590. Preglacial weathering of strata, 513. Prehistoric woodenstructures of Naaman’s Creek, 675. Prestwich, Professor Joseph, 498, 511, 514, - 517, 624; on length of Glacial period, 613 et seq. Prince William Sound, 36. Provincetown, Mass., 137. Puget Sound, 136, 176, 180, 192, 193. Pumpelly, Professor Raphael, 513, 517; on preglacial erosion, 261, on loess, 407 et seq. Putnam county, W. Va., 379, 604. Putnam, Professor F, W., 642; on his dis- coveries of paleolithic implements, 627; on antiquity of man in California, 698, 699. Puyallup River, 21. Pyramid Lake, Nev., 607. Pyrenees, 429, 433, 436, 449; ancient glaciers in, 512. Qu’Appelle River, 333, 335. Quebec, Province of, 570. Queechee, Vt., 247. Queen Charlotte Islands, 506. Queen Inlet, 73. Queenston, Can., 536 et seg., 550. Raccoon Creek, Ohio, 324, 564, 575, 603. Ramsay, Sir A. C., theory of rock basins, 269; on early glaciation, 483 et seq. Randolph, N. Y., 149. Rangeley Lakes, 342, 349. Ravenna, Ohio, 353. Read, Mr. M. C., on buried channels in Ohio, 301. 4 > ewelsg 2 ce dete ey ee ao de ee ote Lei eS ha R : . INDEX. Recession, rate of, of falls of Niagara, 536 et seq.; Falls of St. Anthony, 552 et seq.; falls in Black River, Ohio, 560; of trib- utary to Paint Creek, 561, 562. Red Bank, Ohio, 644. Red River of the North, 199, 220, 258, 316, 333, 334, 354, 361, 607, 654. Red River Valley, 548. Reid, H. F., 71, 72. Reid Glacier, 73. Reid Inlet, 73. Reindeer, 641, 675. Rendu Glacier, 73. Rensselaer Harbor, 89. Revillo Gigedo Island, 188. Rhine River, 410, 412, 447. Rhinoceros, 586, 690. Rhode Island, terminal moraine in, 140, 204; depth of drift in, 259. Rhone Glacier, 255. Richardson , Mr. James, 187, 188. Richardson, Sir J., on transported bowl- ders in the Mackenzie Valley, 246. Richmond, Mass., train of bowlders in, 239-241. Richthofen, Baron, 513, 517; on loess, 408, 409. Ricketts, Dr. Charles, 508. Riggs, Rev. Thomas L., 175. Rink, H., on results of Greenland explor- ation, 77 et seq. Ripley county, Ind., 602. Ripley, Ohio, 170, 367, 526. River that turns, 335. Riviére des Lacs, 334. Roches moutonnées, 84, 183, 185, 187, 227, 231, 295, 483. Rock-basins in the Sierra, 267 et seq., 355. Rock-scoring in Glacier Bay, Alaska, 44; described, 123 et seg.; near Victoria, Van- couver Island, 183 et seg.; on islands in Lake Erie, 262 et seg.; on the Sierra, 267 et seq.; in South Africa, 485. Rocky Mountains, 13, 14, 200, 244, 273, 415-417, 429, 441, 462, 607; ancient glaciers in, 175-177, 512; Quaternary uplifts of, 502, 507, 511, 512. Rocky River, 304. Rome, N. Y., 542, 587. Ross county, Ohio, 372; terminal moraine in, 169, 170; transported bowlders in, 169, 242; vegetable deposits in, 602. Ross, Sir J. C., explorations of, in Ant- arctic Continent, 112 et seq. Russell, Mr. I. C., on glaciers of the Sierra Nevada, 179; on moraines of Monocoun- ty, Cal., 222; on glacial erosion, 267; on 759 Yosemite Valley, 271; on cirques, 271 et seq.; on Lakes Lahontan and Bonneville, 608, 610; on gravel deposits about Dead Sea, 612. Russell Fiord, 31, 32. Sabine, E., explores east coast of Green- land, 98. Saco River, 221, 342, 351. Saguenay, fiord of the, 501. Sahara, Desert of, 433, 496. Salamanea, N. Y., 586. Salisbury, Professor R. D., 501; on loess, 172; discoveries in northern Germany, 452,456; on deposits in New Jersey, 636. Sandusky, Ohio, 262, 390. — Sandy River, 19. Saskatchewan River, 13, 199, 220, 244, 259, 333 et seq., 526, 545. Sawkins, J. G., 507. Searboro Heights, 584, 585, 587. Scandinavia, glaciers of, 104, 106, 445, 447; erosion in, 260; maximum post-glacial uplift, 506. Schenectady, N. Y., 329. Schoodic Lake, 350. Schoolcraft on the antiquity of man, 699. Schuylkill Water-Gap, 197. Schwatka, F., explorations in Alaska by, 29, 30, 190. Scioto River, 169, 300, 314, 323, 326, 327, 375, 561. Scoresby explores east coast of Greenland, 98. Scotland, 487, 534; glacial erosion in, 278; kames in, 339; glaciation in, 445, 446, 483, 484; post-glacial erosion in, 568; maxi- mum post-glacial uplift, 506. Scott, Captain, 120. Scratched stones, by moving ice, 125 et seq.; by land-slides, 127. Scribner, Mr., 701. Scudder, Mr. Samuel, on the existence of Alpine insects on the White Mountains, 438, 439. Sea cow, 436. Sea-level, changes of the, 503. Seattle, State of Washington, 21, 135, 180- 182. Second Glacial epoch, 207, 258, 558, 575, 579, 601, 669. Seeman, G. B., visits Kotzebue Sound, 37. Selkirk Mountains, glaciers in, 13. Serrate character of glacial margin, 132, 525 et seq. Seville, Ohio, 353. Seymour, Ind., 601. Shackelton, E., 120, 121, 760 Shaler, Professor, N. S., 498-500; on depth of the drift in New England, 259; on drumlins, 288, 290; on glacial action in the Connecticut Valley, 486; in Appala- chian region, 487; on the Trenton gravel, 630. Shawshin River, 338. Sheep, 436. Sheyenne River, 333, 334. Shingle Creek, 553, 554. -Ship-canal, possible, between Lakes Su- perior and Michigan, 306. Ship Rock, Mass., 237. Siberia, 36, 476, 477, 479. Sierra Nevada Mountains, 409, 429, 607, 611; glaciers in, 13 e¢ seq., 177, 179, 180, 273; rock-basins in, 267 et seq.; cirques in, 272 et seq.;Quaternary uplifts of the, 501, 502, 507; glaciation of, 568; erosion of, 569. Sinclair, Professor W. J., 700. Sinian Mountain system, 517. Sink-holes, frequent in limestone regions, 143. Sitka, Alaska, 68, 189. Skeena River, 25. Slickenside, 129. Smith Sound, 86, 92, 245. Smock, Professor J. C., on depth of ice in New Jersey and Pennsylvania, 198. Somme River, 574, 623,624. Souris River, 334. Southall, J. C., 508; on antiquity of man in California, 697, 698. South America, 437, 478; glaciers of, 104, 108 et seq., 462; relation of contour of, to the Gulf Stream, 472, 473. South Bass Island, 262, 266. South Brewster, Mass., 139. South magnetic pole, 121. Spencer, Professor J. W., on the erosive power of glaciers, 232, 233; on preglacial drainage, 302, 304; on St. Davids, 550. Sperry Glacier, 13. Spitzbergen, 104, 107, 424, 430, 463. Split Rock, Ky., 385, 386. Springfield, Ohio, 302. Squier, Mr., 385. Stainmoor Glacier, 449-451. Stark county, Ohio, 169, 326. Staten Island, 140. St. Davids, Ontario, 537 et seg., 549, 550. Steenstrup, K. J. V., onrate of movement ~ of Greenland glaciers, 80. Stickeen River, 25, 27, 136, 228. St. Joseph River, Ohio, 208, 209. St. Lawrence River, 305, 314, 354, 357-359, 398 INDEX. St. Louis, Mo., 134, 171, 315, 591. St. Marie’s River, 208, 209. Stockbridge, Mass., train of bowlders in, 239, 240. Stone, Professor George H., on moraines in Maine, 221; on depth of drift in Maine, 259; on drumlins in Maine, 286; on kames in Schoodic Lake, Me., 350, 351. St. Paris, Ohio, 257, 258, 302. St. Paul, Minn., 315, 553, 554, 655, 660. Strait of Georgia, 186, 188, 192. Strait of Juan de Fuca, 182, 192. Straits of Magellan, 111. : Strie, direction of, on the west coast of North America, 183, 186 et seq.; in Maine, 195; on Hudson Strait, 246; in Western Pennsylvania, 248, 249; in Lake Erie, 265, 266; in Scandinavia, 446; in India, 484; in Ohio and Indiana, 591; in Illinois, 591, 592. Stroudsburg, Pa., 146, 352, 637. Sub-Aftonian till, 224. Subglacial streams, source of, 82; of the Alps, 18, 255; on Mount Shasta, 18; Mount Hood, 19; Mount Tacoma, 21; milky-white color of, 18, 21, 135, 136, 254; of Muir Glacier, 51, 55, 62, 67, 68, 342; of Greenland, 82, 255, 256; transporting power of, 67, 68, 82, 135, 136, 254 et seq. Submergence during the Glacial epoch in North America, 200, 413; in Wales, 453. Subsidence in Rocky Mountain region, . 200; theory of, to account for lake ridges, 397, 398; necessary to account for loess 413; theory of, 413, 416; due to weight of ice-sheet, 416, 417, 497, 00, 510, 519; of Sahara and central Asia, 433; on the Atlantic, north of glacial limit, 635; in Vermont, 635; in Dominion of Canada, 635; general, of the glaciated area, 591; in the Delaware Valley, 636-640. Sullivan county, Pa., 195. Superglacial streams, 22, 48, 75, 90. Susquehanna River, 133, 136, 148, 198, 228, 241, 325, 352. Sverdrup, Lieutenant, on east coast of Greenland, 98. Sweden, 104, 339; chalk bowlder in, 239. Switzerland, 463, 496; erosion in, 231, 232, 274; glaciers of, 445, 448. Table Mountain, 692; relics from 694. Tacoma, 136. Taku Inlet, 27. Tapir, 436, 437, 690. Tarr, Ralph, 32, 605. Taylor, Mr., 543. — ee S « >» INDEX. 761 Teazes Valley, 309, 379 e¢ seg., 604. Temperature, of the southern hemisphere lower than that of the northern, 475; of the interior of South America, 478; of northeast Siberia, 478; not altogether dependent on the heat from the sun, 477; variations of, in different latitudes not understood, 479; causes affecting, 480. Tennessee, conglomerates in, 487. Terminal moraines, 251; conditions favor- ing the formation of, 135, 203; char- acteristics of, 142; on Nantucket and Martha’s Vineyard, 137,203; 0n the Eliza- beth Islands, 137, 203; in Plymouth county, Mass., 139; in Long Island, 140, 204; in New Jersey, 142, 151, 206; in east- ern Pennsylvania, 144 et seg., 206; on Pocono Mountain, 146; in Valley of Fish- ing Creek, 148; in valley of Conewango Creek, 150; in Ohio, 168 e¢ seg., 207 et seq.; in Dakota, 174; in Washington State, 180; in Wisconsin, 211; south of Maine, 195; south of New England, 203; in central New York, 206; in Ammonoo- suc Valley, 221; in Great Britain, 448 et seq.; in Germany, 447, 456; compared with those of America, 456 et seq.; lobate contour of, 132, 207, 528, 530, 661. Terraces, glacial, on the Conewango, Ohio, 150; at Lewiston, Pa., 155; on the Mo- hawk, 319; on the St. Croix, 319; on the Wabash, 319; on the Mississippi, 315, 415, 557, 654; on the Ohio and its tribu- taries, 323, 370 et seqg.; in western Penn- sylvania, 371; on Brush Creek, Ohio, 372; at Bellevue, Pa., 375, 384; near Mor- gantown, W. Va., 377 et seg., 603; at Clarksburg and Weston, W. Va., 378; at McKeesport, Pa., 379; in Teazes Valley, W. Va., 379 et seq., 604; on the Big Sandy, W. Va., 382; and Guyandotte, 382; on Lake Agassiz, 500, 655, 664; on the Min- nesota, 558; on the White, Ind., 601; on | Raccoon Creek, Ohio, 603;0n the Somme, France, 623, 624; in southern England, 624, 625; on the Delaware, 633 et seg., on | the Little Miami, 645. Tertiary era, absence of Glacial epochs | during the, 515, 518. Thames River, 447, 449. Thibet, Quaternary uplift of, 510, 513. Thompson, Mr. Gilbert, on the glaciers of Mount Shasta, 15. Thomson, Sir William, 497. Thornville, Ohio, 169. Three Sisters, 19. Tidioute, Pa., 303. | Tierra del Fuego, 109, 110. Tight, Professor, on Kanawha drainage, 309; on Middle Ohio drainage, 309. Till, defined, 123, 129 et seqg.; depth of, 257, et seq.; British Columbia, 185; in Minne- sota, 213, 258, 555, 695, 607; in Canada, 258; in Indiana, 257, 60i,602;in Illinois., 257; in Ohio, 257, 258, 592, 593, 599, 600; in New England, 259; in Pennsylvania, 259, 260, 604; in Europe, 260; average in North America, 280. Tioga county, Pa., 195. Titusville, Pa., 326. Todd, Professor J. E., on glacial dams across the Kansas and Platte River, 172; on Coteau des Prairies, 214; Missouri coteau, 215, 217; on glacial drainage, 332. Tonawanda Creek, 542. Topeka, Kan., 172. Toronto, Can., 584, 585, 586. Torsukatak Glacier, 78. Towson, Mr., 117, 118. Trade-winds, motions of, in the Atlantic, 470; relations to the Gulf Stream, 472; cause of the predominance of the south- east, 473 et seq. Transportation by subglacial streams, 135, 136, 254 et seqg.; in Alaska, 67, 68, 136; in Greenland, 82, 256; in the Alps, 254, 255. Transportation of bowlders, 236 e¢ seg.; in Alaska, 45; direction of, 196, 240 et seq.; in Europe, 236; in New England, 237 et seqg.; in New Jersey, 241; in Pennsyl- vania, 241; in Ohio, 242; in Indiana and Illinois, 243; beyond the Missouri River, 243 et seq.; in British America, 176, 244 et seg.; on northeastern Mackenzie River, 245; upward, 246 e¢ seg.; in Scotland, 484; in Africa, 485; in India, 485. Transportation of till, 257 et seg.; in Ohio, 257; in the Red River region, 258; in New England, 259; in Pennsylvania, 259; in Europe, 260. Transporting power of rivers, 638. Trenton, N. J., 329; paleolithie imple- ments at, 541, 619, 620, 625 et seq., 645, 671. Trenton gravel, 631-633, 637 et seq., 671. Tschernyschey, Professor, 586. Tuckernuck Island, 137. Tundra in Alaska, 36, 37. Tuolumne county, Cal., 13, 180, 689 et seq. Tuscarawas River, Ohio, 301, 316, 326. Two glacial epochs, 575 et seg., 607 et seq., 669. Tyndall, Professor John, measurements of glaciers, 2, 3, 41, 81. 762 Tyndall Glacier, 87. Tyrol Mountains, 104, 365. Uintah Mountains, 178, 179. Unalaska, island of, 36. Uniformitarianism, 532, 533. Upham, Mr. Warren, 497, 504; discovers terminal moraine, 134; traced moraine through Iowa and eastern Dakota, 211, 212; on depth of drift, 258, 259; on drum- lins, 282, 283, 287, 289, 292; on Brown’s Valley, 316; on glacial drainage in the Northwest, 330 et seqg.; in British America, 335; on kames in the Con- necticut Valley, 345; on the gravel plains north of Portland, Me., 349; on kame-like ridges in Minnesota, 353; on lakes of Minnesota, 361, 362; on Lake Agassiz, 401-406, 548, 548; on loess, 415, 416; on Lewis’s work in England, 448, 452; on shells near Bos- ton, Mass., 453; on probable causes of glaciation, 497; on vegetable deposits in .. northern Minnesota, 607; on paleolithic implements, 654 et seq. Ural Mountains, 108, 447. Utah, former glaciers in, 176, 177. Vancouver on glaciers of Alaska, 22 et seq., 30; visit to Disenchantment Bay, 31; on Glacier Bay, 59 et seq. Vancouver Island, 183, 185 et seq., 192, 505. Vegetable remains in glacial deposits, near Muir Glacier, 61 et seq., 233, 592; at Point Wilson, 182, 183; at Morgantown, W. Va., 377, 378, 384, 603; in Teazes Valley, 381, 604; theory of, 576, 579; in Montgomery county, Ohio, 592, 593; in Butler county, Ohio, 592, 598 et seq.; in Morgan, Jackson, Jennings, and Jefferson counties, Ind., 601, 602; in Hamilton, Highland, Ross, and Licking counties, Ohio, 602, 603; in southwestern Indiana, 603; in Penn- sylvania, 604; in Minnesota, 605 Vegetation in the vicinity of Muir Glacier, 41, 69. Veins in glacial ice, 7. Vermont, 194, 247, 635, 665. Vessel Rock, N. H., 236. Victoria, glacial grooves near, 183, 184. Victoria Glacier, 13. Viscosity of ice, 88, 96. Volcanic outflows probably correlated with glaciation, 501. Volcanoes indicating molten interior of the earth, 499. Volk, Mr. Ernest, 630. INDEX. Waagen, Dr. W., 516. Wabash River, 170, 300, 314, 323, 326, 353, 354. Wadsworth, Professor M: E., 498. Wahsatch Mountains, 149-179, 274, 336. Wakefield, N. H., 351. : Wales, 446, 450, 453, 484. * Wallace, A. R., 436, 508, 514, 516-518. Wallenpaupack Creek, Pa., 311. Walrus, 436, 438, 641, 675. Warner, L. C., 306. Warping rafts, 351. Warren county, Pa., terminal moraine in, 149, 150; preglacial drainage in, 307. Warren, Pa., 149, 150,307; kettle-hole in, 598. ‘ Washington county, Pa., 604. Washington Land, 86, 92, 94, 97. Washington, State of, 135, 178, 180, 181; glaciers in, 19 et seq., 177, 191, 222. Watch Hill, 140. Water, peculiarities of its freezing-point, 1, 4, 5. Waterfalls, scarcity of, in unglaciated re- gions, 362. Watertown, N. Y., 481. Wells in Ohio, 168, 169, 257, 258, 602; in British Columbia, 185; in Pennsylvania, 260, 604; in Indiana, 300, 601, 602; near Morgantown, W. Va., 377; in Minnesota, 555, 605, 607. Wells, Mr. David A., 238. Wenkchemna Glavter, 13. Wensleydale Glacier, 449, 450. Weston, W. Va., 378. West Virginia, 604; terraces in, 377 et seq., 603, 604; vegetable remains in glacial deposits in, 377 et seq., 603, 604; wells in, 377; transported bowlders in, 379, 382. Whirlpool in Niagara River, 536 et seq., 549 et seq., 551. White Glacier, 72. White Mountains, Alaska, 43, 61. White Mountains, N. H., 429, 438 et segq., 519. White, Professor I. C., 605; on the Cin- cinnati ice-dam, 197, 370, 371, 384, 603; reports wells in Wyoming county, ‘Pa., 260; reports buried channels in Pike and Monroe counties, Pa., 311; on terraces in West Virginia, 377 et seq., 382, 384; on the Monongahela ice-dam, 391-393. Whittlesey, Colonel Charles, 500; on forma- tion of kettle-holes, 144; reports wells in Ohio, 602. White River, Dak., 173. White River, Ind., 601, 649. INDEX. White River, Ore., 19. White River, State of Washington, 21-23. Whitney, Professor J. D., 498, 513; ascent of Mount Shasta by, 18; cited, 108, 176, 178; on glaciers of New Zealand, 112; on formation of Yosemite Valley, 180, 271; on cause of ice age, 464; paleolithic dis- coveries of, 627; on antiquity of man in California, 688, 692 et seq.; on deep placers of California, 689, 690. Whymper on Greenland glaciers, 82 et seq.; cited, 108. Williams, Professor E. H., 582, 584; on the attenuated border, 151-166. Williamson county, IIl., 170, 171. Willoughby Island, 44, 61, 189. Wilson, Mr. Thomas, 623. Winchell, Professor A., 5; on the effect of pressure of a glacier, 417, 418; on antiq- uity of man in California, 698. Winchell, Professor N. H., 508, 517, 597; on rate of recession of Falls of St. An- thony, 552 et seq., 665; paleolithie dis- coveries of, 537, 656, 660. 763 Wind River Mountains, 13. Wind, transporting power of, 408, 409. Winooski River, 347. Winslow, Dr. C. F., 692. Wisconsin, 525; driftless area of, 134, 413, 414, 527; depth of ice in, 201; kettle-range in, 134, 144, 210 et seq., 221, 361; drift hills in, 286; lakes in, 361; loess in, 413, 414; post-glacial erosion in, 568. Wisconsin episode, 222 e¢ seq. Woeikoff, on Croll’s theory of the cause of the Glacial period, 474; on glaciers of the southern hemisphere, 475, 476; on dis- tribution of heat over the earth, 478, 479 et seq. Wood Glacier, 74. Wood’s Holl, 137, 139, 204, 205. Woodward, Mr. R. S., 295, 503; on rate of recession of Niagara Falls, 540. Wright, C. W., 72. Wright, F. E., 72. Wright, Professor G. F., 508, 517, 665. Wright, Professor W. E. C., 349. Wyman, Dr., 693.