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 DEPARTMENT OF GEOLOGY 
 
 UNIVERSITY of CALIFORNIA 
 
 LOS ANGELES, CALIF.
 
 *: 
 
 *?l^ : *>g3fc^'-i^
 
 
 No.
 
 No.2.
 
 THE 
 
 COMING ICE AGE 
 
 BY 
 C A. M. TABER. 
 
 BOSTON: 
 
 GEO. H. ELLIS, 141 FRANKLIN STREET. 
 1896.
 
 COPYRIGHT, 1896. 
 Bv C. A. M. TABER. 
 
 QUO. M. ILLI*, FXINTIX, 141 FKARKLIN STUEIT, BOSTON.
 
 78 
 Til 
 
 
 P R E FA C E. 
 
 THE explanations given in the following pages, in which I 
 have sought to show the manner in which an ice age is being 
 brought about, is an extension of a treatise on " The Cause of 
 Warm and Frigid Periods," which I published in a small 
 edition in 1894. And, from the small number of copies circu- 
 lated, only a few came to the hands of persons particularly 
 interested in such matter. Yet there were instances of its 
 having proved of special interest to persons celebrated for their 
 geological attainments, and also to instructors in physical geog- 
 raphy. Besides, it received considerate notice in some of the 
 leading reviews. Being thus somewhat encouraged, and think- 
 ing that the subject was too important to be neglected, I have 
 given it further study during the last year, and meanwhile 
 have obtained additional information from recent discoveries 
 which has served to corroborate my views. Hence I have been 
 able to be more explicit in my explanations in the present vol- 
 ume than in my earlier writings. Still, while acting as a pio- 
 neer in the matter, it will be seen that I have only attempted to 
 expose the main outlines, as my age and failing health will not 
 permit me to enter into the voluminous details necessary for 
 a full explanation. In order to show why my attention has 
 been turned to the great climatic changes which have taken 
 place during past ages, and now threaten the future, I will re- 
 peat the introduction of my earlier publication, wherein I 
 wrote that " the reason why I have undertaken to explain the 
 causes which have brought about the warm and cold epochs is 
 because of my being unable to harmonize the several theories 
 
 394727
 
 that have been published with the general mode of action 
 which nature pursues to-day. Having in the early part of my 
 life been employed for a score of years in the whaling service, 
 during which time my sea voyages were passed in cruising over 
 the North and South Atlantic, and over the Indian Ocean, 
 from latitudes north of the equator to the southern shores of 
 Kerguelen Land, and along the seas of Southern Australia, I 
 also, in my searching, cruised over the Pacific Ocean from the 
 icy seas south of Cape Horn to the northern latitudes of 
 Alaska, and, from New Zealand in the Western Pacific to the 
 numerous islands in the tropical zone. And it may be said 
 that among the chief things to be learned on such voyages 
 was the direction of the prevailing winds and surface currents 
 of the sea. Thus the impressions then received were in mind 
 when, in after years, I had my attention drawn to the several 
 theories advanced for explaining the causes which produced 
 the warm and frigid epochs. But, so far as my marine experi- 
 ence goes, such theories have not harmonized with nature's 
 mode of operating at this age of the world. Therefore, I have 
 conceived views which, to my mind, are more agreeable to the 
 simple operations of nature of which I have long been witness. 
 Consequently, I have written several short essays on climatic 
 changes since 1880, and also letters relating to the same sub- 
 ject, which have been published in Science aud Scientific Amer- 
 ican. But the space allowed for the introduction of such 
 matter was necessarily too limited for so wide an explanation 
 as the subject required. The views then advanced I have 
 again repeated, with the addition of several facts pertaining to 
 physical geography, which, so far as I know, have never before 
 been published." 
 
 WAKEFIELD, MASS., U.S.A. 
 June, 1896.
 
 CONTENTS. 
 
 CHAPTER I. 
 
 PAGE 
 
 CAUSE OF COLD AND MILD PERIODS, 9-36 
 
 Traces of ancient glaciers in temperate zones, 9; prevailing 
 winds the main cause of the circulation of the ocean waters 
 between the tropical and temperate zones, 10; general 
 direction of prevailing winds, and how, in connection with 
 continents, they circulate the surface waters of the sea, 11 ; 
 high and low sea-levels; separation of antarctic lands 
 from South America, 12; Captain Larson's discoveries in 
 antarctic regions, 13; how low lands south of Cape Horn 
 were submerged, 13; how the winds move more surface 
 water southward than northward, 14; Dr. Croll's views on 
 winds and ocean currents, 16; under-currents of the ocean, 
 and how caused, 16; Gulf Stream currents, 17; antarctic 
 under-currents, 18; why the winds were able to force more 
 of the ocean waters southward than northward at the close 
 of the Tertiary age, 19; Mr. Alfred R. Wallace's views on 
 Tertiary seas, 20; how the Cape Horn channel affects the 
 ocean currents, 21 ; cause of the increase of cold in southern 
 latitudes, 22; how the Cape Horn channel is closed during 
 ice age, and its effect on ocean currents and temperature 
 of southern latitudes, 24; the melting of glaciers from 
 southern lands, 27; a salt sea requisite for circulation dur- 
 ing ice age, 28; direction of surface currents in southern 
 seas, 29; Humboldt current, 30; Agulhas current, 32; tem- 
 peratureof arctic ice, 34; movement of southern icebergs, 35; 
 glaciers south of Cape Horn, 36.
 
 CHAPTER II. 
 
 PAGE 
 HOW ICE PERIODS IN THE NORTHERN HEMISPHERE ARE 
 
 BROUGHT ABOUT, 37-54 
 
 Northern seas during Tertiary age, 37 ; Gulf Stream during Ter- 
 tiary times, 38; the origin of a cold period in the northern 
 hemisphere, 38; remarks on Gulf Stream and arctic cur- 
 rents, 39; circulation of arctic waters, 40; arctic channels 
 during ice age, 41; how the weight of glaciers in the north- 
 ern hemisphere attracts the waters of the southern seas 
 during ice age, 42; Professor Prestwich on the submergence 
 of European lands, 43; the great Atlantic tide rips the head- 
 waters of the Gulf Stream, 44 ; high sea-level of Atlantic 
 calm region, 45; tropical Atlantic currents, 46; Sargasso 
 Sea, 48; arctic and Gulf Stream currents, 49; Pacific Ocean 
 currents, 50; slow growth of an ice period, 52; reduction of 
 Cape Horn channel, 53; permanence of antarctic glaciers 
 elevated above the snow-line during mild periods, 54. 
 
 CHAPTER III. 
 
 SPREAD OF GLACIERS DURING COLD EPOCHS, 54-61 
 
 Spread of glaciers in tropical zone, 54; Professor Agassizon 
 the origin of Galapagos Islands, 55 ; the bowlders of Hood's 
 Island and rookery of Albatross, 56; alpine flora of Galap- 
 agos and tropical America, 57; Mr. J. Crawford on ancient 
 glaciers in Nicaragua, 58; Cuba and Republic of Colombia 
 during ice age, 68 ; destruction of animal life during glacial 
 age, 59; temperature of North Atlantic and Mediterranean 
 Sea during ice age, 60; temperature of ocean during warm 
 epochs, 61 ; generative age ascribed to warm eras ; Professor 
 Wright on pre-glacial man, 61. 
 
 CHAPTER IV. 
 
 THE GLACIERS OF THE TEMPERATE ZONE, 62-75 
 
 Professor Hitchcock on the early history of North America, 62; 
 glacial deposits of Nantucket and Martha's Vineyard, 63 ; 
 Professor James Geikie on the glacial deposits of Northern 
 Italy, 64 ; California coast ranges the work of Sierra glaciers,
 
 65; ancient glaciers on the Pacific slope north of California, 
 67 ; Professor Geikie's views on the ancient glaciers in the 
 Salt Lake region, 68; Colorado Canon, 69; the conglomerate 
 deposits in the Appalachian district, 69; remarks on the 
 glacial boundaries in United States during ice age, 70; 
 sands of Florida, 71 ; ancient ice-sheets of the plains west 
 of the Mississippi River, 73; the driftless region of Wiscon- 
 sin, 74; tropical waters of North Atlantic chilled during ice 
 age, 75; the drifted snow of British America and Siberia 
 during ice age, 75. 
 
 CHAPTEK V. 
 
 PAGB 
 
 REMARKS ON THEOBIES ADVANCED FOR EXPLAINING ICE 
 
 PERIODS, 76-93 
 
 Professor Geikie on supposed causes of the glacial period, 76; 
 change in the relative level of the land and sea during 
 glacial and post-glacial times, 77; submergence of northern 
 lands at close of ice age, 78; the main cause of the move- 
 ment of water from the northern seas at the close of glacial 
 age, 79; why the earth movement hypothesis should be re- 
 jected, 79; glaciers of Europe and Alaska, 80; North Pacific 
 currents, 81; why the Pacific waters are growing cool, 82; 
 the lowering temperature of the northern seas, 83 ; the in- 
 crease of cold in Europe and Asia, 84 ; falling temperature 
 of the Andean region, 85; General Drayson's astronomical 
 discoveries for explaining the cause of ice periods, 87 ; why 
 the Gulf Stream was always confined to the North Atlantic, 
 89; the improbability of the Indian Ocean currents entering 
 the arctic seas, 90; why the increase of glaciers must con- 
 tinue while the Cape Horn channel maintains its present 
 capacity, 91; comments on the coming ice age, 92; tropical 
 zone the abode of man during ice age, 93; preservation of 
 the tropical ocean fauna through the glacial period, 93.
 
 CHAPTER I. 
 
 CAUSE OF COLD AND MILD PERIODS. 
 
 IT is now generally conceded by those who have given the 
 subject much attention that the greater portion of North Amer- 
 ica above the latitude of 39 north to the shores of the Arctic 
 Ocean has been furrowed and scoured by the action of ice. 
 
 Vast traces of ancient glaciers are also found in Europe ; for 
 it is reported that ice-sheets have left unmistakable marks of 
 having overrun the greater part of the lands lying between the 
 arctic seas and the latitude of the Pyrenees. 
 
 In Asia evidences of glacial action have been noticed from 
 Northern Siberia to the mountains of Syria. 
 
 The great glaciers of Himalaya have in times past attained 
 gigantic proportions. In Northern China huge bowlders are 
 found scattered over the valleys, and a long distance from the 
 mountains. 
 
 The southern hemisphere, in proportion to the extent of its 
 land surface, shows ample traces of former ice action. From 
 the latitude of 38 south to the southern extremity of the 
 western continent there is said to be the clearest evidence of 
 former glacial action in numerous bowlders scattered over the 
 land. 
 
 On the shores of the South Pacific, from the Island of Chiloe 
 to Cape Horn, the coast is fringed with deep fiords, which 
 appear to be channelled out by ice, like the fiords of Norway 
 and Greenland. And at this date the mountains of that 
 southern region are covered with snow, and the glaciers which 
 flow down the valleys are said to reach the tide-water as far 
 north as the latitude of 47 south. The glaciers of New Zea-
 
 10 
 
 land, now of Alpine proportions, during the ice age descended 
 to the sea, and channelled the deep fiords on its south-western 
 coast ; and certain traces of glacial action have been observed 
 in Southern Australia, and also in the province of Natal, South 
 Africa. 
 
 Kerguelen Land is pierced with deep, narrow fiords, which 
 have the appearance of having been the work of ancient 
 glaciers. 
 
 The lands south of the antarctic circle are to-day supposed to 
 be covered by an ice-sheet, of which the great ice barrier sur- 
 rounding that region furnishes ample proof. 
 
 While impressed with the above reports of the work of 
 ancient glaciers, in connectiou with my own observations along 
 the shores of the several oceans, I have been led to seek for the 
 physical causes which brought about the great climatic changes 
 of past geological ages. And, while having the subject under 
 consideration, I have had my attention directed to the manner 
 in which the great prevailing winds in connection with conti- 
 nental lands are able to move the heated surface waters of the 
 tropical oceans into the colder zones, and also transfer the cold 
 waters of the higher latitudes into the tropical zones. 
 
 And it is through this grand movement of the ocean waters 
 that we are enabled to account for the difference in the tem- 
 perature of places now lying in the same parallels of latitude. 
 
 The natural methods for conveying tropical heat into the 
 higher latitudes, and also for excluding it therefrom, are so 
 simple and efficient that on due consideration we are able to 
 conceive how epochs possessing mild climates have been suc- 
 ceeded by periods of frigidity. 
 
 It has been admitted by several writers on climatic changes 
 that, should the tropical surface waters of the ocean be moved 
 into the high latitudes in large volume, thus adding their 
 warmth to the heat imparted by the sun, such combined heat 
 would cause a mild climate. And it has been estimated that 
 the amount of equatorial heat moved into the temperate and
 
 11 
 
 polar regions of the northern hemisphere by the Gulf Stream 
 alone is equal to one-fourth of all the heat received from the 
 sun by the North Atlantic from the tropic of Cancer to the 
 arctic circle. Still, it appears to me, while viewing the subject 
 from a marine standpoint, that the explainers of climatic 
 changes have never fully comprehended the manner in which 
 the surface waters of the ocean are moved from the tropics into 
 the high latitudes, and returned from the high latitudes to the 
 tropics. Consequently, they have neglected necessary and effi- 
 cient natural agents in their explanatory theories, and with 
 much learning and ingenuity have laboriously sought to show 
 how great changes of climate could be brought about through 
 other causes. 
 
 But when we notice the simple methods employed by nature 
 to-day for transferring the heat of the tropics into the higher 
 latitudes, and also the manner of excluding such heat there- 
 from, they appear to afford an explanation for the great 
 changes of climate which have taken place during past ages ; 
 for it appears that the natural manner of proceeding by which 
 heat is moved from the torrid zone into the high latitudes 
 sufficient to cause a mild climate is through the ocean currents 
 which are constantly set in motion by the great prevailing 
 winds of the globe. These winds, as is well known, blow 
 mostly from the east toward the west in the tropics, and from 
 the west toward the east in the high latitudes. 
 
 This counter-movement of the winds, in connection with a 
 continent extending both northward and southward from the 
 equator over many degrees of latitude, such as obtains on the 
 western continent, is abundantly able to create extensive de- 
 pressions and elevations on the ocean's surface, and thus cause 
 vast streams of water to move by gravity from the high sea- 
 levels to the low sea-levels ; and in this way the tropical waters 
 have been moved during past ages, and to a considerable extent 
 are now moved far into the northern and southern seas. 
 
 This transfer of the ocean waters is the main cause of a tern-
 
 12 
 
 perate climate being enjoyed by countries situated in the high 
 latitudes at this age. 
 
 But, in order that the tropical currents should be able to flow 
 into the high latitudes, in quantities sufficient to cause all lands 
 and seas situated in such latitudes to enjoy a mild climate, it 
 would be necessary that the land should extend unbroken, or 
 nearly so, from the arctic to the antarctic circles. Thus, with 
 a continent of such vast extent, the westerly winds would blow 
 the surface waters of the ocean away from the eastern shores 
 in the high latitudes, and so cause extensive low sea-levels ; 
 while the easterly winds of the torrid zone would heap the 
 surface waters of the ocean against the eastern tropical shores 
 of the continent. Consequently, the warm waters of the trop- 
 ical high sea-level would be moved by gravity to the low sea- 
 levels of the high latitudes, even to the arctic and antarctic 
 regions, and thus afford them a mild climate. In this way we 
 account for the mild climate enjoyed on lands and seas within 
 the high latitudes during the warm epochs anterior to the 
 glacial periods. 
 
 As the western continent is the only land that extends un- 
 broken from the equator to the cold latitudes of both hemi- 
 spheres, thus affording an opportunity for the prevailing winds 
 to move the tropical waters into the high latitudes, I will call 
 attention to that portion of the continent which extends far 
 southward into the southern ocean, where the winds and ocean 
 currents have the greatest range and power to affect the cli- 
 mate on different parts of the globe. Here we see South 
 America separated from the antarctic continent by a wide 
 channel of deep water, where the westerly winds blow with 
 great force. The space now covered by this interesting chan- 
 nel, owing to its being situated in the high southern latitudes, 
 must have been occupied by a channel of comparatively small 
 capacity, or else an isthmus of low land uniting the southern 
 portion of South America with the antarctic continent during 
 the warm epochs when the beds of the ancient seas of the
 
 13 
 
 northern hemisphere contained a considerable portion of the 
 water now swelling the southern ocean. 
 
 Therefore, the obstructions which separated the Pacific 
 Ocean from the South Atlantic furnished opportunity for the 
 westerly winds to force the surface waters of the sea away 
 from the leeward side of such obstructions, causing a vast low 
 sea-level, sufficient to attract the tropical waters heaped against 
 Brazil by the trade winds into the southern seas in adequate 
 quantity to cause a mild climate throughout the antarctic 
 regions through long periods of time. 
 
 Recent discoveries have proved that these high southern lati- 
 tudes have been subject to great changes of climate. Accord- 
 ing to the reports from the Dundee whalers, while searching 
 for seal in the icy seas that surround the South Shetlands, they 
 met with the Norwegian ship " Jason," Captain Larsen, who 
 had traced the eastern shore of Graham Land to 68 south lati- 
 tude, noting two active volcanoes. 
 
 The same mariner brought from Seymour Island fossil 
 shells and coniferous wood of the Tertiary epoch. 
 
 These furnish sufficient evidence to show that a warmer 
 climate once prevailed there. 
 
 At the commencement of the glacial age the obstructions 
 which separated the South Pacific from the South Atlantic had 
 become deeply submerged by the sea, which may have been 
 caused by a tendency of the ocean's waters to move southward 
 or by a comparative small movement in the earth's crust. But, 
 on account of the stability of the crust of the earth during 
 times so late as the glacial epochs, the submergence of this 
 southern region was probably owing to the movement of the 
 ocean's waters from the northern hemisphere into the southern 
 hemisphere, which appears to have been brought about mostly 
 through the agency of the great prevailing winds ; for it seems 
 to have happened that the prevailing winds on account of the 
 disposition of the lands and seas were able to move more of the 
 ocean waters southward than they moved northward during
 
 14 
 
 the age preceding the glacial periods. The waters thus slowly 
 and gradually forced into the high southern latitudes must 
 have deprived the northern hemisphere of their heaviness, and 
 added their weight to the southern hemisphere. Therefore, 
 the waters moved southward could not all be returned to the 
 seas of the northern hemisphere by gravity, for the reason that 
 the earth's centre of attraction would change in accordance 
 with the weight of water moved from the northern hemisphere 
 into the southern. It will thus be seen that, while the north- 
 ern seas were drained or became shallow, the augmented south- 
 ern oceans deeply submerged the region south of Cape Horn, 
 thus widely separating the western continent from the antarc- 
 tic lands. 
 
 Although the south-east trade winds on the eastern sides of 
 the Atlantic and Pacific Oceans extend further northward than 
 the north-east trade winds extend southward, owing to the 
 heated tropical shores north of the equator being more exten- 
 sive than such lands south of the equator, still, on account of 
 the general weakness of the south-east trade winds at the equa- 
 tor, and also because of the obstructing northern lands, they 
 have during remote times, and at this age, been largely pre- 
 vented from impelling the surface waters of the sea into the 
 northern latitudes in opposition to the brisk north-east trades. 
 Furthermore, on account of the widening of the oceans as they 
 extend southward, the surface currents setting in the latter 
 direction have more broad and easy passages than the great 
 currents setting northward. 
 
 Moreover, the great currents setting southward on the west- 
 ern sides of the oceans south of the equator are also much 
 assisted during the southern summer months by the strong 
 north-east monsoons which prevail along the east coast of 
 equatorial Africa and the east coast of South America as far 
 as the latitude of 30 south. 
 
 The South African current is impelled northward by the 
 trade winds down the south-western coast of Africa ; but it is
 
 15 
 
 debarred from entering the northern latitudes by the Guinea 
 currents, and so turned away into the south equatorial current 
 which flows into the Brazilian stream. 
 
 The Gulf Stream is much obstructed in its northern 
 movement by the narrow Florida channel and the opposing 
 arctic currents, and also by the trend of the North American 
 coast eastward ; while its return current on the eastern side 
 of the Atlantic has a much less obstructed passage in its south- 
 ern movement, and, while on its way past the Azores and 
 Madeira Islands, is largely assisted by the prevailing winds. 
 
 The Brazil current, with the impelling force of a strong 
 north-east monsoon during the summer season, has no obstruc- 
 tion whatever in its southern passage until it meets with an off- 
 shoot from the great drift current of the southern ocean. 
 
 And the same favorable conditions are obtained by the great 
 currents setting southward on the western sides of the South 
 Pacific while on their way to the low sea-levels east of Southern 
 Australia and Xew Zealand. That portion of the equatorial 
 stream of the Pacific which continues west across the Indian 
 Ocean finds no open passage to the northern seas. Conse- 
 quently, it turns south along the east coast of Africa into the 
 southern seas. 
 
 Therefore, this current, in connection with the great currents 
 setting southward east of Australia, offsets the great Humboldt 
 current setting north along the coast of Peru. 
 
 In the Xorth Pacific the Japanese current setting northward 
 is obstructed by the narrowing of the ocean ; while its return 
 current on the American side has a constantly widening ocean 
 on its passage southward, and also favorable winds to impel the 
 surface waters toward the equator. Still, with all the facilities 
 above mentioned for the movement of the ocean waters into the 
 southern latitudes, it is probable that since the shallow seas of 
 the northern hemisphere were drained, or much diminished, 
 the prevailing winds have not possessed sufficient force to 
 further augment the southern seas, because of the superior
 
 16 
 
 weight of the land in the northern hemisphere compared with 
 the lands south of the equator. 
 
 It will appear to those who attribute the rotation of the 
 earth as being the main cause of ocean currents that I am too 
 much given over to the wind theory. But I have reason to 
 believe, as Dr. Croll has asserted, that "the winds are the 
 principal cause of the ocean currents, and are not due to the 
 trade winds alone, but to the general impulse of the prevailing 
 winds of the globe." 
 
 Dr. Croll also declares that " all of the principal currents of 
 the globe are moving in the exact direction which they ought 
 to move, assuming the winds to be the sole impelling cause." 
 
 Those who think that the rotation of the earth is the real 
 cause of the movement of the great surface currents of the sea 
 should explain in some reasonable way why the Agulhas cur- 
 rent turns west into the Atlantic from the Mozambique stream, 
 and why the Guinea current turns to the east from the main 
 tropical current of the North Atlantic ; for it seems that these 
 two great currents move in direct opposition to the rotation 
 theory, while at the same time many things go to show that 
 they receive their motion from the winds. This view of the 
 question will receive further attention in succeeding pages. 
 
 It is the opinion of some writers that a difference of temper- 
 ature and density between the waters of the polar latitudes 
 and the torrid zone is the principal cause of the movement of 
 the surface waters of the ocean from the equatorial latitudes 
 toward the polar seas, and so returned in under-currents ; and 
 this is a favorable factor for assisting the winds on some parts of 
 the sea, especially in aiding the Brazil current in moving the 
 surface waters from the high sea-levels abreast Brazil, and the 
 equatorial calm belt of the Atlantic into the southern ocean, 
 and also for favoring the surface currents setting southward on 
 the western sides of the South Pacific and Indian Oceans. 
 
 Yet, whatever gravitating force it may possess for assisting 
 the above-named currents, it would also act against the impel-
 
 17 
 
 ling force of the trade winds, while they were drifting the sur- 
 face waters northward toward the equator on the eastern sides 
 of the several oceans, and also to retard the returning surface 
 currents, while being drifted by the winds southward on the 
 eastern sides of the North Atlantic and North Pacific. There- 
 fore, while it would seem to favor the winds in their work on 
 the one hand, it woald act as an opposing agent on other parts 
 of the ocean. Still, the difference of temperature between the 
 tropical and antarctic seas probably does act in opposition to 
 the wide and brisk trade winds on the eastern sides of the great 
 oceans south of the equator, and so prevents their impelling 
 the surface waters northward to a great extent ; and this seems 
 to be one great cause of there being less surface water moved 
 northward than southward over the greatest oceans of the 
 globe. 
 
 The theory that the difference of density caused by the dif- 
 ference of temperature between the polar seas and the equato- 
 rial oceans made under-currents to flow from the polar lati- 
 tudes, and meet in the equatorial seas, can only be carried on 
 in the Atlantic Ocean, and in a comparatively less perfect way 
 in the Pacific Ocean, and not at all in the Indian Ocean. 
 
 The North Atlantic being open to the Arctic Ocean, a por- 
 tion of the Gulf Stream waters that enter it from the north- 
 west of Europe do sink and return southward in under-cur- 
 rents ; and the cold waters which pass down the east and west 
 coast of Greenland also sink under the Gulf Stream while on 
 their southern movement. The meeting of these arctic currents 
 with the cold under-currents from the antarctic seas in the 
 tropical zone is probably one cause of their cold waters rising 
 near the surface of the sea in the torrid latitudes of the Atlan- 
 tic ; and the same conditions probably obtain in a somewhat 
 less degree in the Pacific Ocean. 
 
 Yet it appears that the cold waters of the Antarctic occupy 
 the largest space in the tropical zone, even in the North Atlan- 
 tic. Dr. Carpenter, in his lectures on Ocean Currents, speaks of
 
 18 
 
 meeting with antarctic water so far north as the latitudes of the 
 West India Islands ; and he also says that all of the Pacific 
 Ocean at its depths is supplied from the Antarctic Ocean, as are 
 the cold under-waters of the tropical Indian Ocean, which ex- 
 tend over twenty degrees north of the equator. 
 
 Thus, from what we can learn of the antarctic under-currents, 
 they seem to show that they are not wholly attracted north- 
 ward on account of the difference of temperature between the 
 antarctic and the tropical oceans, but partly because of more 
 surface water being moved southward by the prevailing winds 
 than they are able to move northward. 
 
 And it appears that, if through the winds, combined with 
 the difference of temperature between the antarctic seas and the 
 equatorial waters, and also because of the oceans widening 
 toward the south, more surface water is being carried south- 
 ward than northward, the waters of the under-currents so 
 caused must rise toward the surface in the latitudes from 
 which they were first removed. Having called attention to the 
 fact that the prevailing winds are not able at this date to aug- 
 ment the southern ocean waters from the scanty northern seas, 
 because of the preponderance of northern lands, still there is 
 reason to believe that even now, owing to the form of conti- 
 nents and oceans, and the attraction of the tropical surface 
 waters into the Antarctic Ocean because of the difference of 
 density between the warm and cold seas, the prevailing winds 
 of this age are able to force more of the surface waters of the 
 sea southward than they force northward; but, owing to the 
 superior weight of the land in the northern hemisphere, the sur- 
 plus surface water forced into the southern seas is returned by 
 gravity after being cooled by the antarctic ice, and so adding to 
 the deep under-currents which flow with a sluggish movement 
 over the bottom of the sea into the tropical and northern tem- 
 perate latitudes. And in this way the northern oceans are 
 maintained at their present sea-level. 
 
 The cold under-currents are probably assisted in their
 
 19 
 
 northern movement by whatever difference there may be in the 
 density of the antarctic waters over the bottom waters of the 
 equatorial seas. But, as such currents extend into the northern 
 tropical latitudes of the northern hemisphere, it seems that the 
 winds are the main cause of the under-currents which carry so 
 much antarctic cold into the northern tropical seas, because the 
 winds have forced an undue proportion of ocean surface water 
 southward, to be attracted northward in under-currents by the 
 preponderating northern lands. 
 
 Yet, notwithstanding the superior weight of land in the 
 northern hemisphere, it appears that there have been periods 
 when there was somewhat more water in the oceaus of the 
 southern hemisphere than now; for it is reported that a por- 
 tion of the low lands of Australia show traces of having been 
 submerged during late geological times. 
 
 This may have happened through an increased weight in the 
 antarctic glaciers, which have in past ages, and probably may in 
 future epochs, cause more of the ocean waters to be attracted 
 southward than now obtains. But it is probable that an in- 
 crease of southern ice would be largely counterbalanced by the 
 accumulation of ice on northern lands. 
 
 Yet it appears certain that since the Tertiary epoch the 
 waters of vast shallow seas have been moved from the northern 
 hemisphere into the southern. The dry beds of the ancient 
 northern seas encourage this opinion, while the comparatively 
 small area of southern lands serves to support such views. 
 
 Still, during the ages prior to the glacial periods, while the 
 low lands of the northern hemisphere were covered by the sea, 
 the wide shoal channels which submerged the lower portion of 
 North America afforded convenient passages for the surface 
 waters of the ocean in their northern movement, and so pre- 
 vented the oceans of the southern hemisphere from gaining 
 undue preponderance. 
 
 Hence long geological ages passed away before the winds 
 were able to force more of the ocean waters southward than they
 
 20 
 
 could move northward, and thus augment the southern ocean 
 from the waters of the northern seas. But the slow growth of 
 such immense marine deposits in the shallow seas as are found 
 in the Florida Peninsula and other portions of that region was 
 at length sufficient to greatly obstruct the passage of the Gulf 
 currents in their northern movement, and thus cause conditions 
 which enabled the winds to force more of the ocean waters 
 southward than they could move northward after the close of 
 the Tertiary epoch. 
 
 Mr. Alfred R. Wallace says in " Island Life " that the seas 
 in the northern hemisphere during the Tertiary period covered 
 a much larger area than now, and extended across .Central 
 Europe and portions of Western Asia, and the Arctic Ocean 
 was enlarged. 
 
 As it is not likely that any portion of the waters of the sea 
 have been absorbed by the earth during the late epochs in the 
 world's history, therefore the ocean waters have not diminished 
 except during cold periods, when the water evaporated from 
 the sea was converted into ice, and, eventually, again returned 
 to the sea. 
 
 Thus it necessarily follows that, when the seas of the 
 northern hemisphere contained a much larger portion of the 
 waters of the globe than at this age, the seas of the southern 
 hemisphere must have contained proportionally less. Conse- 
 quently, during such times a portion of the shoal seas of the 
 high southern latitudes must have been dry land. Therefore, 
 this must have been the condition of the shallow sea basins in 
 the region of Cape Horn. 
 
 Mr. Wallace also says that " many peculiarities in the distri- 
 bution of plants and some groups of animals in the southern 
 hemisphere render it almost certain that there has sometimes 
 been a greater extension of antarctic lands during Tertiary 
 times." 
 
 And he also asserts that the great ocean basins have not 
 changed, and that the form of continents has been permanent.
 
 21 
 
 It will thus be seen that it was through the movement of the 
 ocean's waters southward that the low lands south of Cape 
 Horn were covered with water previous to the frigid periods, 
 and so caused the wide separation between the western conti- 
 nent and the antarctic lands. 
 
 The Cape Horn channel thus enlarged, the continuous 
 mildness of the high southern latitudes which possessed the 
 earlier ages came to an end, and gave place to alternate epochs 
 of frigid and mild weather. For it appears that it is owing to 
 the creation or enlargement of the Cape Horn channel that it is 
 possible for frigid periods to be brought about, for the reason 
 that its enlarged space of water prevents the westerly winds 
 from maintaining a great low sea-level in the higher latitudes 
 of the southern ocean ; for, whenever the capacity of the Cape 
 Horn channel is enlarged, the westerly winds, instead of 
 maintaining a low sea-level on the South Atlantic, employ 
 their force in impelling the surface water of the southern seas 
 around the globe. And this work the strong westerly winds 
 of the high southern latitudes have always accomplished when- 
 ever the Cape Horn channel was widely open, and this is what 
 the winds are doing at this date. 
 
 Therefore, such waters of the torrid zone as are moved 
 southward from their high sea-level, caused by the trade winds 
 abreast the Brazilian coast, are largely turned away from the 
 high southern latitudes. It is true, even with an enlarged 
 Cape Horn channel, they can always flow along the South 
 American coast to an inferior low sea-level, caused by the 
 westerly winds blowing the surface waters of the sea away 
 from the coast of Argentine and Patagonia; but on gaining 
 that region they meet the cold ice-bearing currents which turn 
 away east of Cape Horn from the great southern drift current 
 to gain the same low sea-level which attracts the Brazil water. 
 Consequently, the ice-bearing currents from the south, which 
 branch off from the great southern drift current, are able to 
 largely turn away the warm Brazil current from the higher
 
 22 
 
 southern latitudes ; and, furthermore, the great southern drift 
 current which passes through the Cape Horn channel, and so 
 onward around the globe, also partly turns away the Mozam- 
 bique current as well as the East Australian current, and so 
 largely prevents their waters from warming the southern seas. 
 
 Therefore, it is evident that, whenever the Cape Horn 
 channel obtains sufficient capacity to give an independent 
 circulation to the southern ocean, the conditions are favorable 
 for the increase of cold in the southern latitudes. For it is 
 because of the large exclusion of the tropical waters from the 
 southern seas that ice-sheets have been able to form in early 
 periods and in later epochs on the antarctic lands, and store 
 away the annual frosts for thousands of years, and at the 
 same time furnish icebergs sufficient to chill the waters of 
 the southern temperate oceans, and consequently make cold 
 such of the surface waters of the sea as are forced into the 
 southern latitudes by the winds in surface currents, and 
 so returned to warmer seas in cold under-currents, and thus 
 with such frigid combinations bring about cold periods. 
 
 Thus it appears, as I have previously shown, that it is owing 
 partly to there being more of the surface waters of the sea 
 forced southward by the prevailing winds than they impel 
 northward that the cold under-currents are maintained ; but it 
 also requires an independent circulation of the southern ocean, 
 such as I have pointed out, to cool its surface waters before 
 they can sink and form cold under-currents. 
 
 And there is reason to believe that such cold under-currents 
 are more efficient in lowering the temperature of the temperate 
 and tropical oceans than even the icebergs which such under- 
 currents move into the temperate seas. And, when it is con- 
 sidered that the cold antarctic under-currents fill the depths of 
 the Pacific and Indian Oceans in the northern hemisphere, and 
 also largely the tropical depths of the North Atlantic, I am led 
 to believe that the frigid conditions of the ice age were concur- 
 rent in the northern and southern hemispheres. The main rea- 
 sons for such belief I will explain in the following chapter.
 
 23 
 
 After the foregoing explanations, showing how frigid periods 
 are brought about through the independent circulation of the 
 southern ocean surface waters, it is evident that, whenever 
 through a slow natural process the Cape Horn channel is closed, 
 a great change is wrought in the circulation of the southern 
 ocean. 
 
 For instead of the westerly winds blowing the surface waters 
 of the southern seas constantly around the globe, and so turn- 
 ing away and preventing the entrance of the tropical currents 
 into the high southern latitudes, the strong westerly winds, 
 whenever the Cape Horn channel is closed or greatly obstructed, 
 would blow the surface waters away from the Atlantic side of 
 the closed channel, and so cause a great low sea-level, sufficient 
 to attract the ocean waters of the tropical high sea-level abreast 
 Brazil well into the southern seas. Therefore, it is important 
 to trace nature's slow methods of closing the wide Cape Horn 
 channel at the perfection of an ice age. 
 
 In my previous explanations on the subject I have thought 
 that, should the southern seas have remained at or near the 
 same sea-level as now, through an ice period brought about 
 in the manner I have described, ice-sheets would accumulate 
 on the antarctic continent, and also on the southern lands of 
 South America, sufficient to flow out into the sea and close the 
 Cape Horn channel. 
 
 But further consideration shows the impossibility of the 
 southern seas having maintained their present sea-level during 
 the growth of frigid epochs which have left such ample traces 
 of glaciers having extended widely over the lands of the high 
 latitudes of both the northern and southern hemispheres. For 
 it appears that the larger areas of land in the northern lati- 
 tudes, embracing wide continents and large islands, must, dur- 
 ing the growth of a frigid age, have increased the spread of 
 glaciers many times greater in extent than could be obtained 
 on the smaller lands of the high latitudes of the southern 
 hemisphere.
 
 24 
 
 For it is evident that the water evaporated from the sea and 
 deposited in snow on the large continents and islands of the 
 high northern latitudes during the growth of an ice period 
 would, while thus diminishing the ocean waters, greatly in- 
 crease the weight of northern lands. Therefore, the waters of 
 the diminishing seas of the southern latitudes would be at- 
 tracted into the northern oceans in opposition to the prevailing 
 winds. 
 
 Thus it appears that the Cape Horn channel would be too 
 much reduced at the perfection of an ice age to afford an in- 
 dependent circulation for the southern ocean, even without 
 being filled by glaciers to the extent I have pointed out in pre- 
 vious essays. Still, to whatever dimensions the Cape Horn 
 channel might be reduced at the perfection of a frigid period, 
 the enlarged shores bordering its diminished waters would be 
 covered by heavy glaciers that would flow into the shrunken 
 strait, and so close it effectually. Thus the reduction of the 
 Cape Horn channel during the advance of an ice age seems, on 
 close consideration, to be a simple operation of nature, which 
 in the normal course of events must have taken place. 
 
 As the closing of the Cape Horn channel has been considered 
 by reviewers the weak and questionable point in preventing 
 my views from gaining acceptance, it becomes necessary to be 
 explicit concerning the manner in which the Cape Horn chan- 
 nel has in past ages been obstructed. 
 
 According to the charts prepared by John James Wild, the 
 middle portion of the strait is represented as being over a 
 thousand fathoms in depth ; but, as far as I know, its true sound- 
 ings have never been determined. The deep portion of the 
 mid-channel is described as being narrow when compared with 
 its whole breadth from Cape Horn to the antarctic continent. 
 
 And, when it is considered, with the growth of an ice age, 
 how much of the ocean waters would be stored in the vast 
 ice-sheets of the northern hemisphere, and consequently be- 
 cause of their weight a large portion of the diminished south-
 
 25 
 
 ern oceans would be attracted into the northern seas, it seems 
 that the bottom of the shoaler waters of the Cape Horn chan- 
 nel, which now comprise so large a portion of its breadth, 
 would be raised above the surface of the sea. 
 
 The one-hundred-fathom depth south of Cape Horn, now 
 supposed to extend from longitude 70 west to 55 west, and 
 southward to the latitude of 57, would be a land supporting 
 heavy glaciers for six hundred miles along the north side of 
 the reduced channel during the advanced growth of a frigid 
 age ; and the same conditions would be obtained in the vicinity 
 of the South Shetland. And when, in addition, we contemplate 
 the great snow-fall of that region, and the consequent gather- 
 ing of glaciers which would occur on the widened shores of 
 the lessened channel, and the certainty of their flowing into 
 the diminished strait, together with the immense icebergs of 
 such an age groundingMn the shoaled waters, it seems that the 
 complete obstruction of the reduced channel would be accom- 
 plished. 
 
 While contemplating the conditions that would obtain 
 while the Cape Horn channel was being reduced, it will be 
 seen that the independent circulation of the icy southern ocean 
 would be carried on to a considerable extent even after the 
 narrowing strait was no longer able to afford space for wide 
 drift currents, for the reason of the strong current that would 
 be caused on account of the high ocean-level maintained by 
 the westerly winds on the Pacific side of the diminishing chan- 
 nel, and the great low sea-level that would take place on its 
 Atlantic side. 
 
 Still, as previously shown, it seems that during an advanced 
 stage of the frigid epoch, the heavy glaciers from the enlarged 
 northern and southern shores of the shrunken channel, to- 
 gether with the ponderous icebergs, blocking its waters, the 
 closing process would at last be speedy and effective. 
 
 And on further consideration it might be said that a channel 
 of much less width and depth would not have been of sum-
 
 26 
 
 cient capacity to have caused ice periods so wide-spread as 
 those that have left their traces on the continents and islands 
 of the globe, for the reason that the independent circulation 
 of the southern ocean would not have been sufficiently com- 
 plete and long continued to have brought such world-wide 
 cold periods to perfection. 
 
 With the Cape Horn channel closed, as above explained, 
 there would be, as I have asserted, a great change wrought in 
 the circulation of the southern ocean ; for instead of the west- 
 erly winds blowing its surface waters constantly around the 
 globe, and so turning away and preventing the entrance of 
 tropical currents into the higher latitudes, the strong prevail- 
 ing westerly winds would blow the surface waters of the sea 
 from the Atlantic side of the closed Cape Horn channel, and 
 so cause a great low sea-level, sufficient to attract the ocean 
 waters of the tropical high sea-level abreast Brazil well into the 
 southern seas. 
 
 The winds of the southern westerly wind-belt being stronger 
 in that region than on any other portion of the globe, conse- 
 quently they are able to do nearly as much work while drifting 
 surface water as the belt of westerly wind of greater width on 
 other parts of the southern seas. Thus a person who has had 
 a long experience with the forcible westerly winds of the 
 southern ocean can well understand their ability for disturb- 
 ing the ocean waters in the latitudes of the Cape Horn channel. 
 
 The drift currents of this region are moved by the winds 
 and waves from one to four miles an hour. Therefore, with 
 the Cape Horn channel closed, 'there is nothing more certain 
 than that the westerly winds would be able to cause a vast low 
 sea-level on the Atlantic side of the closed Cape Horn strait, 
 and that the waters of the high tropical sea-level abreast Brazil 
 would be attracted to its wide depression, as shown on map 
 No. 1. 
 
 The tropical waters thus attracted far southward would be 
 cooler than the tropical waters of to-day, owing to the great
 
 27 
 
 amount of cold imparted to the ocean by the numerous ice- 
 bergs of a frigid age. Still, they would begin the slow process 
 of raising the temperature of the southern ocean, and would in 
 time carry sufficient heat into the southern regions to melt the 
 ice from all southern lands ; for, in addition to the Brazil cur- 
 rents, the waters of the high sea-level of the tropical Indian 
 Ocean which pass southward down the Mozambique channel 
 would reach a much higher latitude than during periods when 
 the Cape Horn channel was open. 
 
 The ice periods of the northern and southern hemispheres 
 being concurrent, a condition which I shall explain in another 
 chapter, makes it obvious that during the melting of the gla- 
 ciers from the antarctic continent and other southern lands the 
 depleted Cape Horn channel could not gain sufficient capacity 
 to give an independent circulation to the southern ocean during 
 the melting of the southern ice-sheets, on account of the dimin- 
 ishing heaviness of the antarctic ice and the greater weight of 
 the extensive glaciers and augmented seas of the northern lati- 
 tudes. Consequently, it seems that the southern seas would 
 continue in a lessened state while the glaciers were being melted 
 from the northern hemisphere, as was the case during the melt- 
 ing of the ice from the southern hemisphere ; and, furthermore, 
 during such times the glaciers which overrun all the low lands 
 and shoal waters of the Cape Horn region would, on account of 
 their position being to the windward of the tropical currents, 
 be the last great mass of ice to melt from the southern hemi- 
 sphere. 
 
 Therefore, it seems that the Cape Horn channel would con- 
 tinue closed or greatly obstructed while the glaciers were being 
 melted from the lands of both hemispheres. Thus at length a 
 mild climate would extend over the globe, and so remain until 
 the prevailing winds slowly forced the surface waters of the sea 
 into the southern ocean in the manner explained in previous 
 pages, thus filling the Cape Horn channel to its present ca- 
 pacity, and again restoring the independent circulation of the 
 southern ocean.
 
 28 
 
 While contemplating the conditions that would obtain dur- 
 ing the melting of the ice from the antarctic lands, it will be 
 seen that the tropical waters attracted to the great low sea- 
 level to the leeward of the closed Cape Horn channel would 
 eventually enter the great bight of the antarctic continent to 
 the eastward of Graham Land, where Captain Weddell sailed 
 to the latitude of 74 south. This deep gulf, owing to its situa- 
 tion, would receive the full impact of the southern movement 
 of the tropical currents ; and, as the warm waters spread over 
 the wide sea-level, the westerly winds would convert them into 
 a drift current, and under such conditions would be driven 
 along the shores of the antarctic continent, past the South 
 Indian and Pacific Oceans, and eventually, after undergoing a 
 cooling process from the long icy passage, be forced against the 
 Pacific side of the closed Cape Horn channel and the western 
 Patagonian coast. 
 
 While regarding the circulation of the sea during an ice 
 age, it may be said that the ocean's being composed of brine was 
 the cause of its waters being able to circulate in frigid lati- 
 tudes where fresh water would congeal. Consequently, this is 
 one of the reasons why successive periods of frigidity and mild- 
 ness have been brought about; for with an ocean of fresh 
 water, repeated epochs of cold and warmth could not have oc- 
 curred, because a sea composed of fresh water would have con- 
 gealed while circulating in the high latitudes during a frigid 
 age. Therefore, it required a sea of brine to maintain a liquid 
 state during the low temperature of an ice period. 
 
 For, while the cold of a glacial age increased, the saltness of 
 the sea increased also, because of the great amount of fresh 
 water evaporated from the ocean, and stored in ice-sheets on 
 the great continents and islands of the globe. Thus the briny 
 sea was maintained in a liquid state, while washing vast ice- 
 fields and glaciated shores and floating the numerous icebergs 
 of a freezing age. The cold which radiated from such ice- 
 bound seas must have been severe ; but meanwhile the evapo-
 
 29 
 
 ration from the ocean was much reduced, while the saltness 
 and coldness of the sea increased, and so prevented the ice of a 
 glacial period from gaining invincible proportions before the 
 independent circulation of the southern ocean was arrested. 
 Therefore, the remaining warmth of the tropical waters after 
 gaining free access to the antarctic latitudes was able to over- 
 come the accumulated cold of that frigid region. 
 
 At this date the observant navigators who have visited the 
 antarctic seas report that the surface currents above the lati- 
 tude of Cape Horn, while being drifted eastward by the prevail- 
 ing westerly winds, also set toward the antarctic ice cliffs, as 
 shown on map No. 2. 
 
 The reason why this southerly set of the surface currents be- 
 comes noticeable above the latitude of 55 south is because the 
 tropical currents which set southward from the torrid latitudes 
 on the western sides of the Atlantic, Indian, and Pacific 
 Oceans, although largely turned away from the high latitudes 
 by the westerly winds and drift currents, are also able to send 
 sufficient water into the great belt of westerly winds to furnish 
 water for the deep under-currents setting northward from the 
 antarctic shores. Thus the surface waters moving from the 
 north in order to gain the higher latitudes, after entering the 
 westerly wind-belt, are moved in drift currents by the impel- 
 ling winds easterly over many degrees of longitude, and also at 
 the same time slowly southward among the cooling icebergs, 
 because of the attraction caused by the difference of tempera- 
 ture and density between the northern drift waters and the icy 
 seas of the antarctic ice barrier. Consequently, the gradual 
 movement of the surface waters of the westerly wind-belt 
 southward before entering the higher latitudes is not generally 
 apparent ; for it is after they enter latitudes where the globe 
 becomes much reduced in circumference that their southern 
 movement in the contracted seas becomes more noticeable. 
 The impact of this southerly current, which finds its outlet 
 in deep under-currents, and retards somewhat the increase of
 
 30 
 
 ice on the southern continent at this date, also largely prevents 
 the small icebergs and field ice from floating northward, away 
 from the antarctic ice barrier ; for it is such large icebergs as 
 penetrate the deep under-currents that are the best able to 
 move into the more temperate latitudes. 
 
 From the above explanations it will be seen that the impact 
 of surface water against the antarctic ice barrier when the 
 Cape Horn channel was closed would greatly assist the tropical 
 waters attracted to the great low sea-level to the leeward of 
 the obstructed strait to wash the antarctic shores while being 
 drifted eastward by the westerly winds over the southern 
 ocean against the Patagonian coast and the Pacific side of the 
 closed channel, and there causing a high sea-level. This move- 
 ment of the winds and currents encircling the antarctic conti- - 
 nent is shown on map No. 1. 
 
 The vast, high sea-level caused by the westerly winds drift- 
 ing the surface waters against the Patagonian coast would ob- 
 tain a much higher plain, were it not that so much of the water 
 of the great drift current was required to feed the antarctic 
 under-current which constantly sets northward from the an- 
 tarctic shores; yet it would be sufficient to greatly increase the 
 volume of the Humboldt current, which would flow in the 
 same direction it now flows, down the South American coast to 
 the equatorial latitudes, where it would become the main 
 source of the great equatorial stream, and thus offset the in- 
 creased southward flow of the equatorial waters through the 
 Brazil and Mozambique streams. 
 
 The equatorial stream, with its increased volume, would also 
 move, as it moves to-day, across the Pacific; and, on gaining 
 the western side, after sending off large streams to the north- 
 ern and southern latitudes, it would pass through the East 
 India passages into the Indian Ocean, where it would be 
 drifted westward by the trade winds and cause a high sea-level 
 abreast the east coast of Africa, and so become the source of 
 the great Mozambique current, which would flow southward
 
 31 
 
 along the east coast of Africa, and, with the Cape Horn chan- 
 nel closed, would gain a much higher latitude than it would 
 with the channel open. At this age, when the continuation of 
 this great equatorial stream gains the latitude of the Cape of 
 Good Hope, its waters are largely turned eastward by the great 
 drift current of the southern ocean. 
 
 Still, a considerable portion of its waters turns toward the 
 west, forming the Agulhas current, which flows around the 
 Cape of Good Hope into the Atlantic, where it mingles with 
 the cooler currents which branch off from the great southern 
 drift current ; and so, in connection with the latter, it is at- 
 tracted to the low sea-level caused by the south-east trade 
 winds abreast the south-western coast of Africa, and from 
 thence moved as a drift current by the trade winds to the equa- 
 torial Atlantic and coast of Brazil. Thus it will be seen that 
 the Agulhas current, even with the Cape Horn channel in pos- 
 session of its present wide capacity, serves to retard somewhat 
 the advance of a cold period. 
 
 The Agulhas current at this date also partly serves to replen- 
 ish the water which is forced from the South Atlantic by 
 strong westerly winds into the Southern Indian and Southern 
 Pacific Oceans. For it appears that more water is now re- 
 moved by such winds from the South Atlantic than enters it 
 from the South Pacific, even through the enlarged Cape Horn 
 channel of this date ; and this fact seems to favor an impres- 
 sion that a portion of this enlarged channel existed prior to 
 the glacial periods, but with its waters so much reduced as to 
 be unable to give the southern ocean an independent circula- 
 tion sufficient to exclude the tropical currents from reaching 
 the high southern latitudes in adequate volume to maintain a 
 mild climate in the southern hemisphere. 
 
 For previous to the glacial age, with little or no ice gathered 
 on the antarctic lands, it seems that a strait possessing one- 
 half the capacity of the Cape Horn channel of the present age 
 could not prevent the Brazil current and the Agulhas stream
 
 32 
 
 from flowing into the southern ocean in quantities sufficient to 
 make it impossible for glaciers to form on southern lands. 
 
 Thus it is probable that a reduced channel separated the 
 western continent from the antarctic lands even in the mild 
 eras previous to the glacial epochs. 
 
 The Cape Horn channel, at the present age, with a capacity 
 sufficient to largely maintain an independent circulation for the 
 southern ocean, is still only one-third of the breadth of the 
 westerly wind-belt of the southern seas. Therefore, the drift 
 currents do not all pass through it from the Pacific into the 
 Atlantic. Consequently, a considerable portion of the drifted 
 water turns northward west of Cape Horn, and so forms the 
 Humboldt current. 
 
 The Agulhas stream, which even now assists in replenishing 
 the South Atlantic with tropical water, would, during the per- 
 fection of a glacial period, with the Cape channel closed, be 
 a much stronger stream than it now obtains with the Cape 
 channel possessing its present enlarged capacity, for the rea- 
 son that the South Atlantic waters would continue as now to 
 be forced eastward by the westerly winds, while they could not 
 be replenished, as they are to-day, directly from the South 
 Pacific. 
 
 Consequently, the waters of the South Atlantic Ocean would 
 be correspondingly reduced. 
 
 Such conditions alone would greatly increase the volume of 
 the Agulhas stream at the culmination of a frigid age. There- 
 fore, the work of subduing a frigid period in the southern hem- 
 isphere after the Cape Horn channel was closed would not rest 
 on the Brazil current alone, but also on the great equatorial 
 stream of the Pacific and Indian Oceans. 
 
 Yet during such frigid times the sources of the equatorial 
 stream would be greatly chilled by its two great feeders, the 
 Humboldt current and the returning Japanese current, both 
 of which flow down from the high latitudes and meet in the 
 equatorial latitudes on the eastern side of the Pacific, thus 
 cooling the source of the great equatorial current.
 
 33 
 
 But this latter stream, while on its long western passage 
 across the Pacific and Indian Oceans, beneath a torrid sun, 
 with only one cold feeder from the south which approaches it 
 along the west side of Australia, would, on its long tropical 
 journey, be able to obtain considerable warmth, even during an 
 ice period, to supply the Mozambique and Agulhas streams, 
 and so greatly assist the Atlantic waters in bringing about a 
 mild period. Still, the process of subduing the cold of the 
 southern latitudes would be slow, even with the Cape Horn 
 channel closed, because of the vast collection of ice burdening 
 the sea and land. 
 
 Yet there were conditions that were naturally brought about 
 to favor the process of returning warmth ; for it appears that, 
 when the southern ocean was made shallow because of a con- 
 siderable portion of its waters having been moved into the 
 northern hemisphere, it will be seen that the conditions were 
 more favorable for the westerly winds to create drift currents 
 than would be the case on deeper seas. Therefore, the high and 
 low sea-levels caused by such winds would be greater on a shal- 
 low ocean than would occur on deeper waters. Thus the low 
 sea-levels of the shallow southern sea would have strong attrac- 
 tion for tropical surface waters, and so increase the thickness of 
 its warm drift currents, and at the same time its lessened depths 
 would have less capacity for the storage of cold water to re- 
 duce the temperature of the under-waters of the tropical zone. 
 
 And, furthermore, when the southern ocean was shallow, 
 New Zealand acquired a longer extension of land to the north 
 and south. Consequently, the enlarged low sea-level on its 
 eastern side attracted more tropical water into the southern lat- 
 itudes than now. 
 
 So, according to the conditions I have pointed out, the ice- 
 sheets would at length melt away, and a long period of mild- 
 ness would succeed on account of the length of time it would 
 require after the ice disappeared from the earth for the pre- 
 vailing winds to move the surface waters of the augmented
 
 34 
 
 northern seas into the southern ocean, and again restore its 
 independent circulation, and so, after a considerable lapse of 
 time, bring about the geographical and climatic conditions ex- 
 isting at the present date, which can be seen on map No. 2, 
 which shows that a cold period has already made considerable 
 advance in the southern hemisphere, the southern continent 
 and islands being covered with glaciers, and the prevalence of 
 icebergs as far north as the latitude of 35 south. 
 
 Moreover, when we consider that the independent circula- 
 tion of the southern ocean is caused by the westerly winds 
 blowing its surface waters constantly around the globe through 
 the open Cape Horn channel, and so largely preventing the 
 tropical currents from entering the high southern latitudes, 
 and how, in consequence, the cold is slowly on the increase 
 through the constant accumulation of ice on the lands and in 
 seas of the southern latitudes, it appears that a frigid age is 
 slowly progressing in the southern hemisphere. For it seems 
 that continental ice-sheets should not only be able to retain 
 their freezing temperature, but also the mean of the low tem- 
 perature in which they were formed, for a considerable length 
 of time, and so impart their extreme coldness in the shape of 
 icebergs into such seas as border on the glaciated lands. 
 
 It has been proved at Point Barrow that strata of ice and 
 gravel can maintain a wintry temperature through the sum- 
 mer months. Captain G. B. Borden, keeper of the refuge sta- 
 tion in that region, states that Lieutenant Ray, of the Signal 
 Service, excavated through ice and gravel to a depth of forty- 
 one feet, and that the lower portion of the excavation main- 
 tains a temperature 15 Fahrenheit above zero the year around. 
 Therefore, with the probability of southern glaciers obtaining 
 a temperature of over 15 Fahrenheit below the freezing point, 
 we can well realize the frigidity imparted to the southern 
 oceans while melting numerous immense icebergs, and con- 
 sequently will conclude that the temperature of the southern 
 latitudes is gradually lowering.
 
 35 
 
 The icebergs of the antarctic seas would not move northward 
 into the temperature latitudes so readily as they now do, were 
 it not that the general southward set of the southern ocean 
 currents were interrupted by the movement of northerly sur- 
 face currents in the longitudes of the low sea-levels, caused by 
 the westerly winds drifting the surface waters of the sea from 
 the eastern coasts of Southern South America and New Zea- 
 land. For it is owing to the low sea-levels thus created, in 
 connection with the deep under-currents which set northward 
 from the ice cliffs of the antarctic lands, that many icebergs 
 are enabled to move into the temperate latitudes, especially to 
 seas north-east of the Falkland Islands. 
 
 On other portions of the southern ocean above the latitude of 
 55 south the surface waters, while being drifted eastward by 
 the strong westerly winds, also set toward the antarctic shores, 
 and so furnish water for the cold under-currents which set 
 northward from that frigid region. Thus from such parts of 
 the coast only the largest bergs, which require a deep sea to 
 float them, are moved by the under-currents into the temperate 
 latitudes. Therefore, it happens that, while an ice period pro- 
 gresses, and the antarctic icebergs increase in size, the more 
 readily the cold, deep under-currents force them into the tem- 
 perate zone, in opposition to the winds and surface currents. 
 
 The icebergs, after gaining the temperate latitudes, are 
 moved more or less eastward by the westerly winds and drift 
 currents, and so are scattered over the southern temperate 
 oceans, where the melting bergs impart whatever coldness they 
 were able to store up while forming in the antarctic regions. 
 
 The low sea-levels caused by the westerly winds to the lee- 
 ward of New Zealand and to the leeward of Argentine, not only 
 cause the ice-bearing currents to set northward, but they also 
 cause the tropical currents to make considerable inroads into 
 the high southern latitudes. This is the reason why the lands 
 are less burdened with ice on the antarctic shores opposite Cape 
 Horn than on other parts of that glaciated continent.
 
 36 
 
 The tropical currents which turn southward east of New Zea- 
 land largely mingle their waters with the great southern 
 drift current, and so are carried through the Cape Horn chan- 
 nel. Owing to this cause, the antarctic lands abreast Cape 
 Horn are less burdened with ice than other portions of the 
 antarctic shores. 
 
 Thus, were it not for this penetration of warm waters south- 
 ward, the antarctic coasts south of Cape Horn, because of the 
 great snow-fall of that region, would obtain heavier glaciers 
 than other portions of the southern continent. But the time is 
 slowly coming when, with a lower temperature, the ice-sheets 
 on the lands in the vicinity of the South Shetlands will attain 
 greater thickness than the glaciers on other shores of the 
 antarctic continent. 
 
 Hence it appears that, when the several agents for producing 
 and distributing cold in the southern latitudes are taken into 
 consideration, the immense and continuous storage of ice on 
 the southern lands, which adds to the wide-spread fleet of ice- 
 bergs that float the southern temperate seas, and also the vast 
 movement of cold antarctic water into the temperate and trop- 
 ical oceans in deep under-currents, combined with the increas- 
 ing coldness of the westerly winds, are now slowly bringing 
 about in the southern hemisphere a period of frigidity.
 
 37 
 
 CHAPTER II. 
 
 HOW ICE PERIODS IK THE NORTHERN HEMISPHERE ARE 
 BROUGHT ABOUT. 
 
 A LARGE number of geologists are of the opinion that 
 during the whole of the Tertiary period the climate of the 
 northern temperate and arctic latitudes was uniformly warm, 
 without a trace of intervening frigid periods. I have before 
 explained why the climate was made warm in the southern 
 hemisphere during the Tertiary epoch, and how on the closing 
 of that age, and subsequently, a considerable portion of the 
 ocean waters had moved from the northern hemisphere into the 
 southern. 
 
 Therefore, the northern seas during Tertiary times covered 
 a much larger area than have obtained during periods following 
 that mild epoch. So, when the low lands of Europe were sub- 
 merged, the Baltic, .Caspian, and other neighboring seas, now 
 land-locked, were a portion of an enlarged Atlantic. Conse- 
 quently, the westerly winds blew over a much wider North 
 Atlantic than during the later periods. 
 
 Thus the high sea-level caused by such winds on its European 
 side was greater than has since been obtained with the Atlan- 
 tic of less breadth. This high sea-level, composed largely of 
 drift water from the ancient Gulf Stream, had convenient 
 access to the enlarged Arctic Ocean, which then covered the 
 low plains of Northern Europe and Siberia. And owing to the 
 trend of elevated lands north-eastward, which then formed the 
 southern shores of the Arctic Ocean in those regions, the warm 
 waters of the high sea-level of the Eastern North Atlantic 
 found an easy passage into the arctic seas ; for, while they 
 moved over the European and Siberian seas to the north-east, 
 they had the assistance of the westerly winds well into the 
 arctic seas, from which position they were attracted across the 
 
 394727
 
 38 
 
 Arctic Ocean to the low sea-level abreast Labrador and Davis 
 Strait. 
 
 The Gulf Stream of Tertiary times comprised a much larger 
 area than it now obtains ; for with Florida and a large portion 
 of the Gulf States submerged, and a wide, shallow sea covering 
 the Mississippi valley and the Great Lake region, the tropical 
 waters of the enlarged Gulf of Mexico moved from their vast 
 high sea-level to the low sea-level abreast British America and 
 Labrador, without being confined to the narrow Florida chan- 
 nel. Thus with an enlarged Gulf Stream in possession of a 
 wide and clear passage leading northward, in connection with 
 a mild period in the southern hemisphere, giving warmth to 
 the southern oceans, the resources of the ancient Gulf currents 
 for warming the northern regions were so ample and inex- 
 haustive they were fully able to maintain a mild climate on 
 the shores of the European seas, and also on the shores border- 
 ing the Arctic Ocean, during the Tertiary epoch. 
 
 Furthermore, the Humboldt current, which had its rise in 
 the mild southern seas of that age, mingled its warmth with 
 the equatorial current of the Pacific, which in turn gave its 
 warmth to the Japanese current. Therefore, the latter stream 
 under such conditions was competent to maintain a mild 
 climate on the North Pacific coasts. 
 
 The origin of a cold period in the northern hemisphere was 
 largely owing to the changed condition of the northern oceans 
 following the close of the Tertiary epoch. The movement of 
 the ocean waters into the southern hemisphere lessened the 
 area of the Arctic and North Atlantic Oceans, and brought 
 them to their present reduced limits, and also diminished the 
 volume of the Gulf currents. 
 
 This great geographical change, in connection with a cold 
 period progressing in the southern hemisphere, and so increas- 
 ing the coldness of the Japanese current, and the cold antarctic 
 currents, previously explained, which set northward on the 
 bottom of the sea through the torrid latitudes even into the
 
 39 
 
 North Pacific and North Atlantic Oceans, were altogether 
 sufficient to cause conditions favorable for the advancement 
 of a cold period in northern latitudes. Besides, with reduced 
 northern oceans and a diminished Gulf current, conditions were 
 favorable for an independent circulation of the arctic waters, 
 such as is being carried out at the present time. Hence an ex- 
 planation of the movements of the ocean waters of to-day will 
 explain the conditions which caused the northern ice periods in 
 times past, as well as those to come in a future age. Although 
 the conditions are such that the independent circulation of 
 the arctic waters cannot be so well performed as the indepen- 
 dent circulation of the southern ocean, still the open arctic 
 channels are able to prevent the tropical Gulf Stream water 
 from largely entering the higher northern latitudes. For it is 
 certain that the prevailing westerly winds blow the surface 
 waters of the North Atlantic away from the eastern shores of 
 North America from Georgia to Labrador. 
 
 Consequently, the low sea-level thus caused attracts the 
 waters of the Arctic Ocean southward through Baffin's Bay 
 and Davis Strait, and likewise down the east coast of Green- 
 land, thus surrounding that large island with an arctic tem- 
 perature, and so causing it to become a land of glaciers, which 
 are constantly launching icebergs into the sea to cool the waters 
 of the northern oceans. The tropical waters of the high sea- 
 level of the Gulf of Mexico also seek the low sea-level abreast 
 the American coast, thus causing the Gulf Stream. This great 
 ocean current, being the main conveyer of tropical heat into the 
 high latitudes of the North Atlantic, calls for particular notice. 
 The great gravity currents, of which the Gulf Stream is one of 
 the most conspicuous, are moved by small gradients. 
 
 Hence the gradient which causes the Gulf Stream waters to 
 move out of the Florida passage is small. The levellings 
 which have been made place the surface waters of the Gulf 
 of Mexico as being about one metre higher than the Atlantic 
 abreast New York, the pressure of the higher Gulf waters
 
 40 
 
 toward the low level of the Atlantic being nearly equal in 
 the narrow Florida channel from the surface to the bottom 
 of the stream. Therefore, according to descriptions given by 
 Commander Bartlett, the warm stream moves like a river over 
 the hard level floor of the channel; but to the northward of 
 the Bahamas, abreast Cape Hatteras, the stream spreads out in 
 fanlike form, and flows over a bed of cold water of great depth. 
 
 A bed of cold water is found to cover the bottom of all the 
 deep oceans that are accessible to the antarctic seas, through 
 which the cold water is mostly supplied, as I have before 
 pointed out. 
 
 But the cold water which underruns the Gulf Stream is 
 probably furnished by the arctic waters which move down 
 Davis Strait and the east coast of Greenland. The Gulf 
 Stream, as it widens and becomes more shallow, is, through 
 its exposure to the westerly winds, gradually converted into a 
 drift current; and in this way its surface waters are forced 
 over abreast the shores of Western Europe, where it imparts its 
 warmth to a wide region, and also causes a high sea-level. 
 A portion of the waters of this high sea-level turn southward 
 to replenish the waters which have been moved by the trade 
 winds from the eastern tropical North Atlantic over into the 
 Caribbean Sea and Gulf of Mexico, while its northern and 
 smaller portion mingles with the Arctic Ocean waters north 
 of Europe. These latter waters, having escaped from the 
 westerly wind-belt, and acquired a high sea-level, and also 
 made cool on mingling with the icy arctic seas, lose a part of 
 their bulk on becoming chilled by sinking and returning in 
 under-currents to the seas from which they were forced by 
 the south-westerly winds ; while the larger remaining surface 
 waters set across the Arctic Ocean over to the northern coast 
 of Greenland, and so down the east and west coasts of that 
 large island to the low sea-level abreast the American coast, 
 where the cold waters not only crowd the Gulf Stream from the 
 shore, but they also sink under it, and form the vast bed of
 
 41 
 
 cold water over which the Gulf currents flow. This cold 
 underflow of water southward probably joins the deep antarc- 
 tic currents south and south-east of the Bermuda Islands, and 
 returns to the tropical latitudes a portion of the water that is 
 carried into the Arctic Ocean by the Gulf Stream. 
 
 There are times during the late summer and early fall months 
 when the arctic channels are considerably obstructed by ice- 
 bergs, and the low sea-level of Davis Strait and Baffin's Bay, 
 with the assistance of occasional south-east winds, is able to 
 attract the temperate waters of the Atlantic as far north as the 
 Arctic Circle. Also from the same cause the icy waters which 
 flow down the east coast of Greenland are attracted along its 
 southern and south-western shores into Davis Strait. 
 
 Yet at the same time the icy waters which flow from Smith's 
 Sound and other arctic channels move in a counter-current 
 down the westerly side of Baffin's Bay and Davis Strait, and so 
 carry the icebergs and field-ice past Labrador and Newfound- 
 land well on to the borders of the Gulf Stream. And, according 
 to Lieutenant Maury, the westerly gales of the winter months 
 force the temperate waters of the Atlantic, which pertain to 
 the Gulf Stream, several degrees away from the south-east 
 coast of Greenland. Therefore, during such seasons the surface 
 waters of the returned arctic currents, which flow down the 
 east coast of Greenland and Davis Strait, are drifted past 
 Southern Greenland and Iceland, and so onward into the arctic 
 seas, north of Europe. Thus the arctic waters maintain an 
 independent circulation sufficient to largely exclude the Gulf 
 Stream from the arctic seas, and surround Greenland with an 
 arctic temperature; and it is on this account glaciers have 
 formed on Greenland and other arctic shores, and such glaciers 
 are probably increasing, as every iceberg launched from the 
 frigid lands and floated to the lower latitudes lowers somewhat 
 the temperature of the North Atlantic, and so causes conditions 
 favorable for larger accumulations of ice on the arctic shores. 
 
 Yet it is probable that an ice period extending over the
 
 42 
 
 northern temperate zone could not be perfected by this process 
 alone, should the tropical and southern oceans maintain their 
 present temperature. But, with the assistance of a frigid 
 period in the southern hemisphere to cool the ocean waters, and 
 thus lower the temperature of all tropical currents, including 
 the Gulf Stream and Japan currents, an ice age could be 
 brought about in the northern hemisphere equal in intensity 
 to the glacial periods of the past. 
 
 And, when we know that a considerable portion of the heat 
 carried into the northern latitudes by tropical streams is largely 
 derived through the mingling of the waters of such currents 
 with the warm waters of the southern tropical oceans, it is 
 evident that the ice periods of the northern and southern hemi- 
 spheres were concurrent; although the culmination of the 
 northern frigid period would be somewhat later than the per- 
 fected southern ice age, on account of the northern seas requir- 
 ing the assistance of the cold oceans of the southern hemisphere 
 to perfect a northern ice age. 
 
 The small area of the northern seas, compared with the 
 southern oceans, and the wide mingling of the ocean waters of 
 the hemispheres, make it evident that the comparatively scanty 
 northern seas could not bring about or maintain either a frigid 
 or mild period in opposition to the superior oceans of the 
 southern hemisphere. 
 
 On the consummation of an ice period in the northern hemi- 
 sphere heavy glaciers covered the larger portion of its conti- 
 nents and islands, which added so much weight to the northern 
 lands as to attract the waters of the southern oceans into the 
 northern latitudes, as I have before explained. 
 
 Thus, when the ice was mostly melted from the lands of the 
 southern hemisphere, the heavy ice-sheets that remained on 
 the extensive northern lands would still continue to attract 
 the warm waters of the southern seas into the northern oceans ; 
 and in this way the Japanese and Gulf currents would gain a 
 higher temperature and greater volume, and thus add to their
 
 43 
 
 ability for melting the northern glaciers wherever they were 
 able to flow, and so hasten the growth of a mild era in the 
 northern hemisphere. 
 
 And it seems reasonable to suppose that there was more 
 water in the northern hemisphere on the ending of its ice 
 period than at this age ; yet it appears that it was returned to 
 the southern hemisphere during a short period by the prevailing 
 winds in the manner which I have previously explained. 
 
 Therefore, there are but few traces of such flowage to be 
 found in the glacial drift, especially with the scarcity of marine 
 life after the rigor of a frigid age. 
 
 An article in Science, July 5, 1895, written by Agnes Crane, 
 states that Professor Joseph Prestwich has recently contrib- 
 uted a suggestive memoir on this subject to the Philosophical 
 Transactions of the Royal Society. It treats of the evidence 
 of a submergence of Western Europe and the Mediterranean 
 coasts at the close of the glacial period ; and in a previous 
 paper communicated to the Geological Society of London, in 
 1892, the author gave evidence, deduced from personal obser- 
 vation, of the submergence of the south of England not less 
 than a thousand feet, at the close of the glacial epoch. 
 
 Since that time the flood of water which flowed all of the 
 low lands of the high northern latitudes has been returned to 
 the southern seas, because of the force of the prevailing winds 
 in connection with the great oceans which open so widely 
 toward the south, the force of the winds being assisted through 
 the attraction caused by the difference of temperature in the 
 surface waters of the vast southern temperate oceans and the 
 antarctic seas, and in this manner bringing about the geograph- 
 ical conditions of to-day which favor the return of another 
 ice age. 
 
 It is said by those who attribute the great currents of the 
 ocean to the rotation of the earth that the winds have little to 
 do in causing such currents as the Gulf Stream. But my im- 
 pression is that the southern portion of the Gulf Stream
 
 44 
 
 waters, after being drifted by westerly winds over abreast 
 Europe, are attracted to the low sea-level in the vicinity of the 
 Canary Islands, to be moved by the trade winds toward the 
 equatorial calm belt and the West India Islands. And dur- 
 ing my many months' cruising over these seas I have had my 
 attention directed to the singular action of the surface waters, 
 while being impelled by the trade winds toward the West India 
 sea ; for during the first fifteen hundred miles of their passage 
 they are moved by the prevailing easterly winds without much 
 apparent resistance or unusual disturbance. But on nearing 
 the longitude of Cape St. Roque, and having acquired a high 
 sea-level from which there is no easy or wide outlet, the im- 
 pelled surface waters begin to rebel against the forceful winds, 
 and cause a remarkable commotion in the shape of tide-rips 
 and white-capped ripples, which extend from the equator in a 
 northerly direction to the latitude of about 19 north, thus 
 crossing the central portion of the north-east trade-wind belt, 
 with a breadth of over three hundred miles, as shown on map 
 No. 2. 
 
 This disturbed region where the winds and waters conflict 
 is the probable fountain-head of the Gulf Stream. The reason 
 why the surface waters of this disturbed portion of the Atlan- 
 tic do not flow peacefully along through the West India pas- 
 sages into the Caribbean Sea and Gulf of Mexico is because of 
 their narrow outlet at the Florida channel. For it is mainly 
 through this narrow channel that the vast waters of the tropi- 
 cal high sea-level are attracted to the low ocean-level of the 
 Western North Atlantic. 
 
 Thus it seems that the great fountain-head of the Gulf 
 Stream is situated between the wide tide-rips and the Carib- 
 bean Islands. The waters from this high ocean-level enter the 
 Caribbean Sea mainly through the several passages south of 
 Guadeloupe ; while the northern portion of the raised waters 
 set mostly toward the north-west, and so unite with the east- 
 ern portion of the Gulf currents after they enter the Atlantic.
 
 45 
 
 Still, the great high sea-level which presses against the Wind- 
 ward Islands, being somewhat higher than the Caribbean Sea, 
 forces its waters through the island passages in quantities suf- 
 ficient to supply the Gulf Stream ; and there are times when 
 the winds are so strong and favorable that all of the passages 
 east of Cuba conduct water into the Caribbean Sea, the cold 
 under-waters entering the deeper channels as well as the warm 
 surface waters. Yet the currents setting through these numer- 
 ous channels are subject to fluctuations, and so also is the Gulf 
 Stream which they supply. 
 
 That portion of the high sea-level south of Guadeloupe re- 
 ceives considerable assistance as a feeder for the Gulf Stream 
 through being connected on the south by the great high sea- 
 level abreast Brazil and the great high sea-level of the equato- 
 rial calm belt. The latter high level is caused by the trade 
 winds, which generally blow briskly down the coast of Sahara, 
 and also further off shore, and ending south of the Cape Verde 
 Islands somewhat abruptly in the equatorial calm belt. 
 
 The south-east trades which blow over the Eastern and Mid- 
 dle South Atlantic terminate on the southern side of the calm 
 region. Therefore, the two trade winds impel the surface 
 waters of the tropical Atlantic from opposite directions di- 
 rectly toward the calm belt, and so raise its waters above the 
 common level of the sea. 
 
 This is the opinion of the writers of the South Atlantic 
 Directory. Still, it is probable that the high ocean-level of the 
 calm belt is but slightly raised above the common level of the 
 sea, ou account of the trade winds having to contend against 
 the tendency of the warm tropical surface waters to move 
 toward the polar latitudes. The calm belt expanse which ex- 
 tends from Africa, where it attains its greatest width, gradually 
 narrows as it extends westward to the longitude of Cape St. 
 Roque, where it attains its highest sea-level, on account of the 
 borders of its narrowing space being impelled westward by the 
 trade winds.
 
 46 
 
 The movement of the waters of this high ocean-level is 
 mostly toward the west, forming a portion of the equatorial 
 current of the Atlantic. The reason of its western movement 
 is on account of its raised waters being able to supply a portion 
 of the Gulf Stream with water which is sent off in a westerly 
 current along the South American coast, west of Cape St. 
 Roque into the Caribbean Sea; while, on the other hand, it 
 joins with the great high sea-level abreast Brazil, and so unites 
 with its great southern current. The gradient of the high sea- 
 level of the calm belt on its southern side probably extends 
 south of the equator, on account of the south-east trades being 
 weak in latitudes near the equator ; while on the north side 
 the north-east trades generally blow brisk and end more 
 abruptly, so producing a gradient of less width than that of the 
 South Atlantic side. 
 
 It does not appear that the seas of the high northern lati- 
 tudes gain an undue proportion of the tropical Atlantic waters, 
 because of the south-east trades extending north of the equator, 
 on account of such winds being weak, and the waters of the 
 high sea-level of the Western North Atlantic having narrow 
 and otherwise obstructed passages leading to its northern seas. 
 Yet the high sea-level of the equatorial calm belt is always 
 ready, whenever a favorable grade is formed by a monsoon or 
 otherwise, to run off its surplus water obtained by winds and 
 rain ; and I have noticed, while cruising in these seas, that it 
 happens at times during the northern winter months when the 
 north-westerly gales drive the surface waters of the North- 
 western Atlantic toward the tropical zone, and at the same 
 time a strong north-east monsoon is prevailing along the south- 
 ern coast of Brazil, the westerly currents setting past the Ama- 
 zon River are reversed, and set to the south-east, while such 
 conditions last. 
 
 For, when the summer solstice is in the south, and the north- 
 east monsoon moves southward along the coast of Brazil, much 
 equatorial water moves off in that direction ; and during the
 
 47 
 
 same season the cooled Sahara has an outward flow of air 
 toward the south, which moves more or less water from the 
 coast of Guinea, which is easily accomplished, because the 
 warm surface waters of that coast are inclined to join with the 
 south equatorial stream. Consequently, the waters move from 
 their high sea-level north of Cape Palmas, and so form the 
 Guinea current. 
 
 The high sea-level of the equatorial calm belt of the Atlantic 
 contains a large portion of the conserved heat of the tropical 
 Atlantic, which at this age sends off a somewhat limited supply 
 of warm water to the Gulf Stream, and also to the Brazil cur- 
 rent. But, whenever the Cape Horn channel is closed or much 
 obstructed, so causing a great low sea-level in the Southern At- 
 lantic, the tropical waters heaped against Brazil, and the raised 
 waters of the great calm region being one continuous high sea- 
 level, would mostly be attracted to the vast low sea-level of the 
 southern ocean. Hence it will be seen how large a portion of 
 the conserved heat of the tropical Atlantic would be used to 
 warm the high southern latitudes during a warm period in the 
 southern hemisphere, and at the same time the head-waters of 
 the Gulf Stream would obtain the same height as now. For 
 we now see much of the force of the north-east trade winds lost, 
 while maintaining so large a high sea-level to the windward of 
 the West India Islands, which is probably capable of supplying 
 a stream of double the capacity of the gulf current which 
 passes through the Florida channel. 
 
 And it appears, while viewing the vast reservoirs of warm 
 water apparently gathered by trade winds to subdue the cold 
 of the high latitudes, that much of the energy of such winds 
 is now lost to the world, while maintaining a vast and pent-up 
 high sea-level which has a difficult outlet to the northern seas, 
 and no strongly attractive low sea-level to move its waters into 
 the oceans of the high southern latitudes. The wide waters 
 which are banked up to the windward of the West India 
 Islands, and cause the wide tide-rips, set mostly to the westward
 
 48 
 
 into the Caribbean Sea through the passages south of Guade- 
 loupe, while the northern portion of the raised waters set 
 mostly toward the north, and thus form the eastern boundary 
 of the Gulf Stream, and comprise the inner circle of the great 
 current that encircles the Sargasso Sea. 
 
 I have been informed by an old Barbuda fisherman that " the 
 weeds which float on the surface of the Sargasso Sea grow in 
 large quantities on the bottom of the shoal waters to the north 
 and eastward of that island and Antigua." Consequently, the 
 currents of that region carry such weeds as become detached 
 from their places of growth into the higher latitudes, where 
 the westerly winds in the winter season drift them eastward 
 south of Bermuda, until finally the central area of their gath- 
 ering, where the most dense collection of weeds is found, is 
 situated near the tropic of Cancer, and about 55 west longi- 
 tude, as shown on map No. 2. 
 
 This position is also the centre of the great circular currents 
 which encompass the Sargasso Sea. The comparatively few 
 weeds which enter the Gulf Stream abreast Florida are cur- 
 rented to the northward of the Bermuda Islands, and from 
 thence drifted by the westerly winds to the south-west of the 
 Azores before entering the trade-wind belt. The weeds, on 
 their long drift from their native shoals, hold their freshness, 
 and continue to grow while floating on the sea for a consider- 
 able time, but at length lose their renovating properties, and 
 in certain areas of the sea acquire an appearance of age and 
 decay. 
 
 The Gulf Stream, and such other tropical waters as are at- 
 tracted northward to the low sea-level abreast the North Ameri- 
 can coast, pass into the westerly wind-belt, and so gradually 
 become drift currents, while being forced by the winds over to 
 the European side of the ocean, as we have previously shown. 
 
 The vast movement of the North Atlantic waters encircling 
 the great Sargasso Sea has often been pointed out by writers 
 on the subject. But the central and most dense portion of the
 
 49 
 
 vast sea of weeds has always been placed on the charts several 
 degrees of longitude east of its true position. 
 
 It is fifteen years since I wrote of the Gulf Stream and arctic 
 currents as being attracted to a low sea-level caused by the 
 westerly winds. But, as far as I know, writers on the Atlantic 
 currents have had nothing to say of the great low sea-level 
 caused by the westerly winds blowing the surface waters of the 
 North Atlantic away from the eastern coast of North America, 
 from Georgia to Newfoundland, and thus attracting the arctic 
 and Gulf Stream waters in opposite directions, fifteen hundred 
 miles along the North American coast. For, were it not for 
 this low sea-level, the Gulf Stream would not be able to move 
 so far northward as it now flows, but would spread out, were 
 there no unevenness in the sea-level of the Atlantic, and be- 
 come a drift current far south of its present northern limits. 
 The United States government has caused surveys to be made 
 of the Gulf Stream, and the interesting discoveries thus ob- 
 tained have all been laid before the public. Still, such sur- 
 veys cover but a portion of the whole round of the vast move- 
 ment of the Gulf Stream water, and do not refer to the vast 
 high sea-level of the calm belt as being one of its feeders, or to 
 the wide disturbance of the surface waters of the tropical 
 North Atlantic in their conflict with the trade winds, while 
 being forced to the vast high sea-level of the Caribbean Sea 
 and Gulf of Mexico, and so giving head to the Gulf Stream. 
 
 Thus from the foregoing explanations it will be seen that the 
 ability of the prevailing winds to move the surface waters of 
 the ocean away from the weather shores of continents over 
 against the opposite leeward shores in the different wind-belts 
 of the globe, and so cause both high and low sea-levels, is the 
 main reason why there is an interchange of surface water be- 
 tween the tropical and colder zones sufficient to carry heat 
 from the tropics to the cooler regions, and thus largely affect 
 the temperature of the higher latitudes. 
 
 The unmistakable traces of cold periods having occurred in
 
 50 
 
 both hemispheres have given rise to an ingenious astronomical 
 theory to account for their origin. According to this theory 
 the ice periods in the two hemispheres were consecutive; and 
 it is admitted by its supporters that, should it be shown that 
 the frigid periods in the northern and southern hemispheres 
 were concurrent, the astronomical doctrine would have to be 
 abandoned. 
 
 It is impossible for a person who is acquainted with the 
 great surface currents of the several oceans to conceive how 
 a mild period could be maintained in the northern hemisphere 
 with a frigid period existing in the southern hemisphere. 
 A frigid period in the latter hemisphere necessitates a cold 
 temperature for the superior oceans of the globe south of the 
 equator. With this vast area of water reduced to a chilling 
 temperature, it seems impossible for the inferior waters of the 
 northern latitudes to maintain sufficient warmth to favor a 
 mild period in the northern hemisphere, especially with both 
 hemispheres receiving an equal annual amount of the sun's 
 rays. The great Humboldt current, having its rise in the 
 southern ocean west of Cape Horn, would during a southern 
 frigid period greatly lower the temperature of the vast equato- 
 rial stream in the Pacific Ocean. Consequently, the Japanese 
 stream, which branches off from the equatorial current into 
 the North Pacific, would be cooled to such a degree that it 
 would be unable to maintain the mild climate on the shores of 
 the North Pacific which extensive lands now enjoy. Further- 
 more, during a cold period in [the southern hemisphere the 
 temperature of the Gulf Stream would also be greatly lowered by 
 the great South-eastern Atlantic return current, which is caused 
 by the south-east trade winds impelling the surface waters of 
 that region into the equatorial latitudes, such waters being re- 
 plenished from the common level of the southern ocean, and 
 so mingling the cool waters of that sea with the equatorial 
 waters of the Atlantic during a frigid period in the southern 
 latitudes. And it may be said that during such times the
 
 51 
 
 frigid Antarctic Ocean would send its cold under-currents to 
 cool the inferior northern oceans. Even to-day the northern 
 and southern hemispheres, through the intermingling of the 
 waters of the northern and southern oceans, largely maintain 
 a like temperature in their temperate zones. Therefore, when 
 we consider the certain traces of ice-sheets having formed on 
 South Africa and Southern Australia, and to have overrun 
 South America above the latitude of 40 south, thus strewing 
 the oceans of the southern temperate zone with ice that are 
 now largely free from it, it seems that the maintenance of 
 warm oceans in the northern hemisphere during the time of a 
 frigid period in the southern hemisphere would be impossible. 
 
 In order to make this statement more plain, I will again 
 refer to the importance of the great Humboldt current for 
 cooling the waters of the North Pacific during the perfection 
 of a southern ice age. For during such times the ocean 
 strewed with ice west of Cape Horn, where the Humboldt 
 current takes its rise, would impart its coldness to the Hum- 
 boldt stream, while it was floating icebergs toward the equator. 
 The equatorial current of the Pacific being a continuation of 
 the Humboldt stream, its waters would partake of its coldness. 
 The Japanese current, being a large offshoot from the equato- 
 rial stream, would also possess a lower temperature than it 
 obtains at this age. Yet at this date, with the southern ice- 
 sheets confined to the antarctic lands, it does not possess heat 
 sufficient to prevent glaciers from flowing down to the tide- 
 water from mountains in Alaska. 
 
 Consequently, the Japanese stream could not maintain a 
 mild climate on the North Pacific coasts while a cold period 
 was being completed in the southern hemispheres. Therefore, 
 under the conditions above set forth the support of a mild 
 period in the northern hemisphere during the existence of a 
 frigid period in the southern hemisphere could not be carried 
 out. 
 
 From what has been explained, it will be seen that the
 
 52 
 
 growth of an ice period is necessarily slow, especially in its 
 early stage, and also that the storage of ice is carried on in 
 both hemispheres at the same time; but I will call further 
 attention to the southern hemisphere, because it possesses 
 greater resources than the northern for the production of an 
 ice age. 
 
 The independent circulation of the southern ocean waters, 
 as before shown, turns away the tropical currents, and thus 
 largely prevents their warm waters from entering the high 
 southern latitudes. Consequently, the heat from the sun's 
 rays, and all other sources of heat included, are not suffi- 
 cient to prevent ice from gathering on lands within the ant- 
 arctic circle. This increasing storage of ice is only another 
 name for the accumulation and spreading of cold, and so the 
 increasing dullness goes on. The snow falls, and thus adds 
 to the extension and thickness of the ice-sheets; and at the 
 same time the spreading snow-fields reflect the heat received 
 from the sun's rays into space, while the cold is retained and 
 increased in the growing glaciers. 
 
 The spreading ice-sheets having covered the land are able 
 to flow into the surrounding seas, where their outer edges 
 become detached and form icebergs, which float out to sea, and 
 so scatter over the adjoining oceans. Thus their coldness is 
 mingled with and largely preserved by the sea, while the sur- 
 face water, which is carried into the southern latitudes from 
 the northern oceans by the prevailing winds, and also such 
 surface waters as are attracted into the antarctic seas because 
 of the difference of temperature of the antarctic waters and 
 the more northern seas, are on gaining the frigid latitudes 
 made cool, and returned to the more northern seas in cold 
 under-currents, and so chilling the vast under-waters of the 
 great oceans of the globe, and eventually their wide surface 
 waters also ; and so the coldness increases until the ice-sheets 
 which at first formed on polar lands are enabled to spread 
 slowly toward the equatorial regions so long as the indepen- 
 dent circulation of the southern ocean is maintained.
 
 53 
 
 But at length the depth of the great southern ocean is dimin- 
 ished because of the water evaporated from its surface, and 
 precipitated in the shape of hail and snow over the vast conti- 
 nents and islands of the high northern latitudes, thus add- 
 ing sufficient weight to the northern lands to attract the waters 
 of the southern seas and still further lessen their depth. Thus 
 during such times the Cape Horn channel is so reduced as to be 
 obstructed by the heavy glaciers and icebergs of an ice age. 
 
 Consequently, a great change is wrought in the circulation of 
 the southern seas. For, when the Cape Horn channel is closed, 
 the westerly winds employ their strength to force the ocean's 
 surface waters away from the glaciers which have filled the 
 diminished channel. This potent action of the winds necessa- 
 rily creates a great low sea-level on the Atlantic side of the ob- 
 structed strait, sufficient to attract the tropical waters heaped 
 against Brazil by the trade winds, and the waters of the high 
 sea-level of the equatorial calm belt, and also the equatorial 
 waters which set along the east coast of Africa, well into the 
 southern seas. 
 
 It will thus be seen that the conditions for the circulation of 
 the tropical ocean waters have met with a great change. 
 
 But the temperature of the waters has been lowered by the 
 coldness of a frigid period ; and, consequently, their capability 
 for conveying heat to the high latitudes has largely dimin- 
 ished. Therefore, their first inroads in the higher latitudes 
 make small impression on the icy seas, so the early process for 
 melting ice is exceedingly slow. But the icy southern ocean, 
 deprived of its independent circulation, in the course of time 
 yields to the warming invasion of the tropical waters, whose 
 wide and increasing spread is eventually able to bring about a 
 mild period, according to the natural methods which I have ex- 
 plained in the preceding pages. 
 
 And it may be said that a mild period succeeding a glacial 
 age gained sufficient warmth to melt the ice-sheets from all 
 lands excepting the highest mountains. For it is probable
 
 54 
 
 that there are lands situated in the antarctic circle sufficiently 
 elevated even during late Tertiary times to have been above 
 the snow-line. Therefore, the glaciers on such lands could not 
 have melted away during mild periods succeeding an ice age. 
 For, as has been explained, a portion of the waters of the south- 
 ern seas had moved into the northern hemisphere. Conse- 
 quently, the antarctic lands were raised higher above the sea- 
 level than at this age. Hence the area of lofty land was in- 
 creased above the snow-line. And, according to Dr. James 
 Croll's estimate, the ice-sheet at the south pole is at this age 
 several miles in thickness. Therefore, its upper surface is 
 above the line of perpetual snow, and could not be melted 
 away during the warm eras succeeding glacial periods. 
 
 CHAPTER III. 
 
 THE SPREAD OF GLACIERS DURING COLD EPOCHS. 
 
 I HAVE before explained that the conditions are such that 
 the cold periods of the northern and southern hemispheres 
 were concurrent. Through this cause, while the glacial epoch 
 was being perfected, the ice followed down the mountain 
 ranges of both hemispheres ; and, while gathering on the lands 
 of the temperate latitudes, it also spread over a portion of the 
 tropical zone. It is reported that traces of ancient glaciers are 
 found in India, and also in Central America and in tropical 
 South America. In fact, the denudation caused by ancient 
 glaciers on the elevated lands of the tropics are too well de- 
 fined to be attributed to any process of weathering, while Al- 
 pine plants of the same species are found near the summits of 
 mountains in the tropics as well as in the high latitudes of 
 both hemispheres. 
 
 This fact goes to show that a portion of the lowlands of the 
 tropical zone have experienced a temperature favorable for the
 
 55 
 
 growth of Alpine plants. And, judging from the tropical 
 islands I have visited, situated in the cold currents which flow 
 down the eastern sides of the oceans from the high latitudes, I 
 think they show strong traces of having during some remote 
 period been subject to the action of glaciers. The island of St. 
 Helena, situated in the southern tropical Atlantic, has the ap- 
 pearance of having been heavily iced during a frigid age. Its 
 steep ravines, which deepen as they approach the sea, recall to 
 the southern voyager the ice-worn islands of the high latitudes. 
 It seems improbable that these deep ravines which penetrate 
 the hard volcanic rock, on their short course to the sea, could 
 have been caused by their scanty brooklets. 
 
 The bowlders scattered over the island are not in harmony 
 with the weathering process, while the obliteration of its 
 craters seems to point to a more rapid process of erosion than 
 could be attributed to weathering. 
 
 Professor Agassiz, in his " General Sketch of the Expedition 
 of the ' Albatross,' " states that the Galapagos Islands are of 
 volcanic origin, and that their age does not reach beyond the 
 earliest Tertiary period ; and his report seems to favor the im- 
 pression of their having undergone denudation sufficient to 
 slough off large portions of the rims of the older craters, and 
 also the eastern face of Wenman Island. On Hood's Island, 
 at the time of my visit, its crater had entirely disappeared. 
 
 The highest portion of the island, which was the probable site 
 of its ancient crater, showed no trace of its former existence ; 
 yet at the foot of this low mountain, on its southern side, I saw 
 a large collection of loose bowlders, composed of hard volcanic 
 rock, which were mostly free from soil and other debris, and 
 easily moved from their places, while the spaces afforded by 
 the loose piles of dark basaltic rocks afforded a secure retreat 
 for numerous owls and lizards. Beyond the rocky piles to the 
 southward a horizontal area of land was strewn with bowlders 
 to the sea, which was some two miles distant from the higher 
 land. The bowlders which covered the plain were somewhat
 
 56 
 
 smaller than those at the foot of the mountain, as none of the 
 former were more than three or four feet in their longest meas- 
 urement. 
 
 They seem to have been formed from thin strata of lava, 
 which were broken in pieces from pressure, such as the action 
 of ice could perform. In fact, the crowded and angular and 
 somewhat worn blocks of lava presented a different appearance 
 from stones thrown from the crater of a volcano, while no such 
 bowlders are found among the recent volcanic eruptions on the 
 islands. 
 
 The plain so thickly strewn with bowlders, and partly 
 shaded by a tall growth of shrubs, fell off abruptly at the sea- 
 side, forming a steep cliff some two hundred feet in height. 
 
 The rocky floor at the foot of the cliff received such debris as 
 fell from the sea-washed land ; yet it contained few bowlders, 
 they having been washed away by the waves soon after falling. 
 
 At one place a steep, dry ravine penetrated the land from the 
 seashore, which was dangerous to cross on account of the loose 
 stones resting on its sides. Two or three miles further west, 
 on the level land bordering the sea, a large rookery of albatross 
 were brooding their eggs and chicklings. The land on the 
 south side of Albemarle, near the sea, consists of debris from 
 the eroded high lands ; and, judging from the crumbling cliffs 
 by the sea, it seems that the land at one time extended further 
 seaward. 
 
 Besides the excessive denudation which appears to have 
 taken place on portions of these bowlder-strewn lands, we have 
 other unmistakable testimony of their having formerly pos- 
 sessed a frigid temperature. The characteristic Alpine flora of 
 these islands points to a time when they were exposed to a cold 
 climate. Furthermore, rookeries of seal and albatross, which 
 naturally belong to shores situated in cold latitudes, still exist 
 on these equatorial islands ; and, when we consider the favor- 
 able position of the Galapagos for the reception of cold during 
 a frigid period, we can well account for the lingering signs 
 which point to their former cold climate.
 
 57 
 
 During the perfection of an ice period the western shore of 
 South America was covered with an ice-sheet from the summits 
 of its mountain range to the sea, extending northward as far as 
 the latitude of 38 south. 
 
 This vast ice-sheet, situated in a region of great snow-fall, 
 was constantly sending icebergs into the sea, where they were 
 borne northward by the cold Humboldt current directly toward 
 the Galapagos Islands ; while, on the other hand, in the north- 
 ern latitudes, in regions of great snow-fall, such as Alaska and 
 British America, numerous icebergs were launched into the 
 ocean, to be currented southward to the Galapagos seas. Thus 
 during the frigid epoch the equatorial waters surrounding the 
 Galapagos group was one of the greatest gathering places for 
 floating ice to be found on the globe. 
 
 And here the frigidity stored up in the glaciers of the higher 
 latitudes was set free, thus chilling the waters as well as the 
 atmosphere of that region. The Alpine flora of the American 
 coast mountains was probably carried by floating ice to the 
 Galapagos, while its rookeries of albatross and seal date back 
 to a cold period. And it seems that these cold-weather ani- 
 mals, with the assistance of the cool Humboldt current, may be 
 able to preserve their rookeries at the equator until the advent 
 of another ice period. In connection with the evidences of a 
 cold climate having possessed the Galapagos, there are ample 
 traces of ice-sheets having flowed over a large portion of the 
 high lands of tropical America, and in some places the ice may 
 have flowed down to the sea, especially where the large rivers 
 now empty; and it is said that masses of clay, mixed with sub- 
 angular stones, have been found in Brazil, which goes to prove 
 the glaciation of portions of that tropical land during a remote 
 age. Professor Louis J. R. Agassiz, during his research in the 
 Amazon valley, found bowlders resting near the summits of the 
 low hills of that region, which he attributed to the action of 
 ice. The spread of glaciers on southern continents and islands 
 is shown on map No. 1.
 
 58 
 
 In Science, Nov. 17, 1893, Mr. J. Crawford published a sum- 
 mary of his discoveries in Nicaragua, during ten months of 
 nearly continuous exploration since August, 1892. 
 
 The author of this report says : " The numerous eroded 
 mountain ridges and lateral terminal moraines of that tropical 
 region give unquestionable evidences of the former existence 
 of a glacial epoch, which covered an area of several thousand 
 square miles in Nicaragua with glacial ice. The ice-sheet 
 covered a large part of the existing narrow divide of land 
 (containing about 48,000 square miles) between the Pacific and 
 Caribbean Sea." And it is likely that other large areas of trop- 
 ical America were glaciated at the same time, especially in 
 regions of great precipitation. 
 
 The island of Cuba, during a portion of the ice age, probably 
 supported heavy glaciers, and obtained an average temperature 
 as low as South-western New Zealand at this age. According 
 to the description given by J. W. Spencer, of the Cuban land, 
 great valleys have been excavated, the lower portion of which 
 are now fiords, reaching in one case at least to seven thousand 
 feet in depth before gaining the sea beyond. Thus, while keep- 
 ing in view the glacial condition of Central America during the 
 frigid period, it seems that the great Cuban excavations were 
 partly the work of glaciers of the same cold epoch.* Judging 
 from such reliable statements, it is probable that the climate of 
 tropical America during the frigid age was somewhat colder than 
 obtained in the tropical regions of the eastern continent, owing 
 to the wide connection of the Atlantic with the Arctic Ocean 
 as well as with the antarctic seas, and because of its shores pos- 
 
 *The meeting of the British Association for the Advancement of 
 Science, September, 1895, was reported in Science of October 18, where 
 mention is made of an interesting paper by Mr. R. B. White, on " The 
 Glacial Age of Tropical America," in which he described a number of 
 apparently glacial deposits in the Republic of Colombia, almost under the 
 equator. He spoke of moraines forming veritable mountains, immense 
 thicknesses of bowlder clay, breccias, cement beds, sand, gravels, and 
 clays, beds of loess, valleys scooped, grooved, and terraced, monstrous 
 erratics, and traces of great avalanches."
 
 59 
 
 sessing a larger area of glaciated lands in proportion to its 
 size than the Pacific and Indian Oceans, and also owing to the 
 tropical Atlantic containing so small a portion of the world's 
 waters which lie within the torrid zone, and its equatorial cur- 
 rent being separated by continental lands from the great equa- 
 torial stream of the Pacific and Indian Oceans. 
 
 Therefore, the tropical Atlantic waters must have been re- 
 duced to a lower temperature during a frigid age than the 
 tropical waters of the Indian Ocean or the western part of the 
 tropical Pacific, as a large portion of the great equatorial cur- 
 rent of the latter oceans, during its western movement, was ex- 
 posed to the rays of a tropical sun for a much longer time, after 
 being replenished by the cold waters of the high latitudes, than 
 the tropical currents of the Atlantic ; and it is probable that, 
 on account of tropical America possessing a colder climate than 
 the tropical lands of the eastern continent during the frigid 
 epoch, the cold of the western continent was more destructive 
 to its fauna and flora than was the case in the tropical regions 
 of the eastern continent. Professor Wright, in his valuable work 
 on " The Ice Age of North America," gives a good description 
 of the " flight of plants and animals during the glacial epoch," 
 and also of the extermination of many superior species because 
 of the frigid climate. 
 
 The high lands of tropical Africa, above the altitude of 
 three thousand feet, and situated in places of great precipita- 
 tion, were probably covered with snow and ice during the 
 glacial age. Travellers have reported that islands composed 
 partly of granite bowlders are found in the lakes at the head- 
 waters of the Nile. But the glaciers that invaded the tropical 
 latitudes were of short duration compared with the ice-sheets 
 that burdened the lands of the temperate zones. Besides, such 
 tropical ice as flowed to the low lands was so near a melting 
 condition that it made small impression on the rocks ; but on 
 steep mountain slopes, where the movement of the ice was 
 comparatively rapid, it possessed considerable eroding power.
 
 60 
 
 The climate of the tropical zone on both continents during the 
 perfection of an ice period was so cold that such animals as 
 could not endure a low temperature retreated into the warmest 
 regions of the equatorial latitudes, while many species who 
 failed to reach such places perished. And especially was this 
 the case with the pre-glacial fauna of the western continent. 
 Mr. W. B. M. Davidson, in his treatise on Florida phosphates, 
 says : " The great mammal hordes of the glacial epoch were 
 driven into Florida in their flight southward for life aud 
 warmth, and there perished because of the deadly cold which 
 ever moved southward. The Florida waters grew so icy cold, 
 fishes, reptiles, and mammoth animals died, and added their 
 frames and teeth to the valley of bones now found in that 
 southern region." 
 
 Such species of the tropical fauna of the ocean as survived 
 the ice age could have existed only in torrid seas with small 
 connection with the cold oceans during the frigid epochs. For, 
 with the diminished oceans of a cold period, it seems that 
 the conditions were favorable for the maintenance of such 
 seas in the region of the East India Islands. 
 
 Such parts of Southern Europe and Northern Africa as 
 bordered on the Mediterranean Sea probably possessed a 
 milder climate during the ice age than regions in the same 
 latitudes on the Atlantic coast, for the reason that the North 
 Atlantic was proportionally a greater receptacle for icebergs 
 which were launched into it from the numerous glaciers of 
 North-eastern America, Greenland, Iceland, and North-western 
 Europe than the great inland sea obtained from its less frigid 
 shores. And it may have happened that during such times the 
 tropical waters of the Indian Ocean had some connection with 
 the Mediterranean through the Red Sea and Suez, and so dur- 
 ing portions of the year the waters of the tropical Indian 
 Ocean were forced by the periodical winds into the inland sea. 
 It is the opinion of several writers that man, along with other 
 species of animal life, existed previous to the glacial period ;
 
 61 
 
 for, since the seas and lands of the globe were chilled, the con- 
 ditions seem to have been less favorable for the spontaneous 
 generation of animate bodies than during the previous warm 
 ages. Therefore, it appears that the generative ages should 
 be ascribed to the long genial eras prior to the glacial epochs. 
 For it is probable that the lower parts of the ocean, which 
 now possess a low temperature even in the tropical latitudes, 
 were, during the warm eras, wholly composed of warm water, 
 because the surface waters of the antarctic seas of that age, 
 which supply the great under-currents of the ocean, would 
 possess a high temperature ; and it is probable that the tem- 
 perature of a large portion of the seas of the torrid zone was 
 for a long time maintained at blood heat. For it should be 
 considered that the waters which moved from the torrid seas, 
 after making their journey through the warm regions of the 
 high latitudes, would on their return to the tropics retain a 
 large portion of the heat they acquired in the torrid zone before 
 making their journey to the mild polar regions. 
 
 And, when we reflect how the heat of the sun's rays was 
 conserved by the ocean waters, and that their circulation dur- 
 ing such times was almost wholly performed by the winds, as 
 the difference of temperature between the polar latitudes and 
 the equator was small, it appears that during the eras previous 
 to the glacial age the oceans must have obtained a higher 
 temperature than possessed by the warmest seas of to-day. 
 
 According to the discoveries of Professor Wright and others, 
 ancient stone implements have been found beneath the glacial 
 drift, as well as the bones of animals whose descendants are 
 now living, which goes to prove that man, with other species of 
 fauna which now inhabit the earth, existed anterior to the 
 glacial epoch. 
 
 And on consideration it seems unreasonable to suppose that 
 any of the superior species of animals could have been brought 
 into existence since the waters and lands of the earth were 
 chilled by the cold of a glacial age. And it appears that many
 
 62 
 
 species of animals which are known to have survived the cold 
 periods were indebted for such survivals to the slow process 
 through which a frigid period is brought about, thus affording 
 time for evolutionary inurement to the slow increase of cold 
 which at length perfects a glacial epoch. 
 
 The inurement to cold acquired by animals during the 
 glacial age is still an attribute possessed by many species 
 of fauna to-day. For, when a warm climate took possession of 
 the tropical zone, it was deserted by a large portion of the 
 animals that found refuge there during the glacial age. 
 
 Thus, while the seas and shores of the cooler latitudes swarm 
 with animate bodies, the torrid latitudes seem comparatively 
 lonely to the voyagers on the tropical oceans. 
 
 CHAPTER IV. 
 
 THE GLACIERS OF THE TEMPERATE ZONES. 
 
 HAVING asserted that during the culmination of a frigid 
 period the ice-sheets spread over a portion of the lands of the 
 tropical zone, I will give my views, with those of several 
 writers, on the spread of ice-sheets within the now temperate 
 latitudes ; and meanwhile I will repeat a portion of my former 
 essays on the subject. Professor Hitchcock, in his lectures on 
 the early history of North America, says that " the history opens 
 with igneous agency in the ascendant, aqueous and organic 
 forces become conspicuous later on, and ice has put on the 
 finishing touches to the terrestrial contours." But there appear 
 to be various opinions held by geologists respecting the changes 
 brought about on the earth's surface during the glacial period. 
 Some think that glaciers have never been an important geologi- 
 cal agent, while others assert that during the glacial epoch 
 heavy ice-sheets covered the elevated portions of Western
 
 63 
 
 North America as far south as the thirty-sixth parallel of lati- 
 tude, and Eastern North America was overspread with ice- 
 sheets, which attained a depth of five or six thousand feet, and 
 were able to more their debris over wide lands of little declivity 
 toward the sea, their immense deposits forming the lands 
 of Cape Cod, and also the islands of Nantucket and Martha's 
 Vineyard. 
 
 But it is now said that thia implied magnitude of the glacial 
 deposits on the lands skirting the New England coast is with- 
 out foundation, since the larger bulk of these islands consists 
 of upturned Cretaceous and Tertiary strata, which are only 
 thinly covered with glacial debris, such as bowlders, gravel, 
 clay, and sand, from the eroded shores of the mainland of 
 New England. But it appears that the dislocated and folded 
 cretaceous strata which underlie the glacial drift of Nantucket 
 and Martha's Vineyard were during an early period deposited 
 on the bottom of a shallow sea, which then covered the Vine- 
 yard Sound, Buzzard's Bay, and their surrounding lowlands. 
 Thus the ice-sheets of the frigid age which moved over New 
 England displaced the yielding stratified deposits of the shal- 
 low sea, and forced them southward in a disturbed condition to 
 the position which they now occupy. 
 
 Still, it is apparent that only a small portion of the glacial 
 drift is found on these islands, which, according to appearances, 
 must have been eroded and moved southward from the rocky 
 lands of New England during the ice age ; but there is suffi- 
 cient to show that large quantities of such debris were carried 
 over the islands into the Atlantic. And, judging from the 
 eroded rocky New England lands, there must have been suffi- 
 cient glacial drift moved over Nantucket and Martha's Vine- 
 yard into the ocean beyond to far exceed in bulk the deranged 
 Tertiary and Cretaceous deposits which now form so large a 
 portion of the islands. 
 
 For, when we look over lands bearing traces of the ice age, 
 where the glaciers did not move their drift into the sea, so the
 
 64 
 
 terminal moraines of such glaciers can be better estimated, we 
 can realize the great work that has been performed by the ice- 
 sheet that overran New England during a frigid age. 
 
 Professor James Geikie. states, in his discussion on the gla- 
 cial deposits of Northern Italy, that the deposits from Alpine 
 glaciers of a frigid period "rise out of the plains of Piedmont 
 as steep hills to a height of fifteen hundred feet, and in one 
 place to nearly two thousand feet. Measured along its outer 
 circumference, this great morainic mass is found to have a 
 frontage of fifty miles, while the plain which it encloses ex- 
 tends some fifteen miles from Andrate southward." And it is 
 reported that there are found on the southern flank of the Jura 
 numerous scattered bowlders, all of which have been carried 
 from the Alps across the intervening plains, and left where 
 they now rest. Many contain thousands of cubic feet, and not 
 a few are quite as large as cottages. 
 
 Such blocks are found on the Jura, at a height of no less than 
 two thousand feet above the Lake of Neuchatel. The Jura 
 Mountains being formed of limestone, it is easy to distinguish 
 the debris deposited by Alpine glaciers ; and, from what I can 
 learn of extensive glacial work, it appears that intervening 
 plains, lakes, and sounds are so often found separating the 
 source of ancient glaciers from their deposits that their exist- 
 ence becomes almost necessary to represent the general outlines 
 of disturbance performed during an ice period. In consider- 
 ation of such facts and the foregoing statements of reliable ob- 
 servers, I am prompted to offer my views on glacial work per- 
 formed on a portion of the Pacific shores of North America, 
 which seems to me to be much more extensive than hitherto 
 supposed. 
 
 Professor Whitney describes the coast mountains of Califor- 
 nia as being made up of great disturbances, which have been 
 brought about within geologically recent times ; and this state- 
 ment I found to be so obvious in my travels over that region 
 that it appears to me that the coast ranges originated in a dif-
 
 65 
 
 ferent manner from the older Sierras. The western sides of 
 the latter mountains everywhere show the great eroding power 
 of ancient glaciers ; and, when I considered their favorable po- 
 sition for the accumulation of snow during a glacial period, I 
 was led to seek for the glacial deposits adequate to represent 
 the great gathering of ice which an age of frigid temperature 
 would produce. 
 
 But it seemed to me that such deposits could not be found in 
 the foot-hills of the Sierras, which contain the moraine of infe- 
 rior ice-sheets that terminated at the base of the mountains. 
 
 Under these conditions I came to the conclusion that during 
 the earlier ice period the immense glaciers which must have 
 formed on the western slopes of the Sierra range moved their 
 gigantic accumulation of debris so far seaward as to form the 
 range of hills now existing next the coast line, and perhaps 
 the islands abreast the Santa Barbara coast, the Contra Costa, 
 or eastern range, being formed during a subsequent ice period, 
 in the same manner as the hills next the coast line. 
 
 Still, it may be that neither of the coast ranges was the work 
 of a single cold epoch ; but the western range must necessarily 
 have been the earliest deposit. Although the coast ranges dif- 
 fer from the Sierras in their make up, yet it does not disagree 
 with the glacial origin of the former inferior mountains, from 
 the fact that the ice-sheets, while moving their bulk westward, 
 displaced the deposits of such bays, lakes, rivers, and marshes 
 as lay abreast of the Sierra slopes. The advancing ice-sheets, 
 thousands of feet in depth, moving from a lofty and steep in- 
 cline, pressed and ploughed below the somewhat superficial cre- 
 taceous and alluvial strata which lay in their course. The dis- 
 turbed strata, while forced along in confused heaps in front of 
 the ice, were amassed in ridges sufficient to form the hills of 
 the coast ranges. The bowlders found imbedded in several of 
 the coast hills must have been moved by the ice from the Sier- 
 ras on account of the coast ranges not having a rocky core of 
 sufficient firmness to give shape to such bowlders. Moreover,
 
 66 
 
 the temperature of the Pacific waters would not be favorable 
 for glaciers to form on the coast ranges, with the ice-sheets of 
 the Sierras terminating at the foot-hills. 
 
 The Sacramento and San Joaquin Valleys are now covered 
 by recent river deposits. Therefore, the glacial drift which 
 should be traced from the Sierras to the coast ranges is con- 
 cealed. 
 
 Yet the abraded appearance of exposed solid rocks at the 
 base of the foot-hills, and also the scattered bowlders which 
 gradually disappear beneath the diluvial deposits of the plains, 
 indicate that the Sierra ice-sheets could not have ended at the 
 foot-hills, but must have moved further westward, while gath- 
 ering immense accumulations in their front, sufficient to form 
 the coast hills, the debris thus amassed being able to arrest the 
 further movement of the ice seaward. 
 
 The coast ranges in several places have been subject to igne- 
 ous action, which may have been brought about through heat 
 generated from pressure exerted on the interior masses after 
 the ice had melted away, the heat thus produced being suffi- 
 cient to cause outbursts of lava, where the nature of the mate- 
 rial favored combustion. The low plains, lakes, and bays 
 which separate the Sierras from the coast hills are in a po- 
 sition similar to the shallow sounds which separate Nantucket, 
 Martha's Vineyard, and Long Island from the inferior slopes 
 of the mountains of New England. Therefore, while agreeing 
 with glacialists, who believe that great geological changes have 
 been wrought by ice-sheets in Italy and New England, it ap- 
 pears to me that the ancient glaciers of the Sierra Nevada have 
 accomplished more extensive work, owing to the Sierras being 
 situated in a more favorable position to receive the humidity 
 of the ocean. 
 
 Hence, with a low temperature, vast quantities of snow must 
 have collected on their lofty sides ; and at the same time their 
 great height and declivity would cause the ice to move down 
 their steeps with greater force than the glaciers which passed
 
 67 
 
 over New England. "Writers who have given the subject con- 
 siderable study think that the deep valleys of the Sierra Nevada 
 were produced by disruptive rather than erosive agencies. 
 This conclusion has been formed from the lack of large accu- 
 mulations of debris about their lower extremities, which would 
 not be the case if such valleys were the result of glacial 
 erosion. But, should the coast ranges be attributed to glacial 
 action, as has been stated, we can well account for the debris 
 that should accumulate from the erosion of the deep valleys. 
 
 The only thing that could prevent the ice from gathering 
 on the Sierra Nevada range during an ice period in greater 
 masses than on any mountains in the northern hemisphere 
 would be the lack of cold; for, with a low temperature, the 
 fall of snow would be enormous. This is shown by the great 
 snow-fall during the short mild winters of to-day. Therefore, 
 with ice-sheets covering a large portion of the lands of the 
 high northern latitudes, and with the Japanese current which 
 tempers the north Pacific waters made cold in the manner 
 described in the foregoing pages, and while the sea along the 
 north-west coast of America was strewn with icebergs launched 
 from Alaska and British Columbia, it seems that California 
 must also have obtained a frigid climate during the ice age. 
 Therefore, on account of its exposure to the ocean winds, and 
 the consequent heavy snow-fall, the accumulation of ice on its 
 lands must have been immense. For, when it is considered 
 that the glaciers of North America extended southward even 
 into the torrid zone sufficient to cover a large portion of Cen- 
 tral America, it is unreasonable to suppose that any portion 
 of California could escape being covered by heavy ice-sheets 
 during the glacial epoch. The comparatively scant fall of rain 
 and snow over Greenland is known to form ice-sheets hundreds 
 of feet in thickness. 
 
 Therefore, what must have been the depth of ice over the 
 high lands of the Pacific coast north of California at the cul- 
 mination of a frigid period? The descriptions given by Dr.
 
 68 
 
 Dawson and others, of glacial phenomena along that coast, 
 favor the impression that an immense ice-sheet at one time 
 deeply covered the whole region from the top of the mountain 
 range to the ocean. 
 
 Thus all the deep channels were filled and all the islands 
 deeply overrun with ice, while the immense bergs launched 
 from the shore and carried by the winds and currents south- 
 ward were probably not melted until they reached the tropical 
 latitudes. Thus, when the whole circulation of the Pacific 
 waters are taken into account, it will be seen that their temper- 
 ature during the ice age must have been considerably lowered. 
 The movement of ice-sheets on the Pacific slope was probably 
 local in character, and not connected with the movement of 
 ice on the eastern sides of the mountains. 
 
 From what I have seen of the vast territory lying between 
 the Sierra Nevada and the Rocky Mountains it appears that it 
 obtained much heavier ice-fields than generally supposed. Pro- 
 fessor Geikie in his lectures says of this region that during 
 the glacial age, "in the Second Colorado Canyon, the sides 
 were completely glaciated from bottom to top. These walls 
 are from 800 to 1,000 feet high, and at the thickest point the 
 glacier was 1,700 feet thick " ; and he says that " the country 
 around Salt Lake was covered with ice, for the rocks about 
 there show the action of ice, and that the bones of the musk-ox 
 are found there." This vast area of ancient ice, although 
 subject to little movement in its interior basin, still, in what- 
 ever movement it may have had, must have found its main 
 outlet through the Grand Canyon of the Colorado. 
 
 For in no other way can we account for the erosive forces 
 necessary to excavate that immense chasm. Not even the 
 mighty torrent that carried off the waters of the melting ice- 
 sheets that covered the interior portion of the continent could 
 accomplish work of such magnitude. 
 
 According to Professor Geikie's observations the Second 
 Colorado Canyon was filled with glaciers during the ice age.
 
 69 
 
 Therefore, it seems that these glaciers must have flowed down 
 into the Grand Canyon, and there united with glaciers flowing 
 from more northern regions. 
 
 An account of a collecting expedition to Lower California 
 by G. Eison, in 1895, describes ancient moraines at the ex- 
 tremity of the peninsula as being prominent, large, and steep. 
 This region lies under the tropic of Cancer, and 8 south of 
 the mouth of the Colorado River where it empties into the 
 Gulf of California. Hence it appears that the temperature 
 of that portion of North America during the ice age was favor- 
 able for the great glacier of the Colorado Canyon to have 
 flowed into the Gulf of California. 
 
 The wide, shallow basins of Utah and Nevada were filled 
 with the water from the melting ice-sheet on the breaking up 
 of the ice period, and the lakes so caused remained for a con- 
 siderable time after the disappearance of the ice. But, owing 
 to the great evaporation and light rain-fall of that region, the 
 lakes gradually shrank away, the filling and emptying of the 
 lake basins being governed by the cold and mild epochs. 
 
 The conglomerate deposits in the Appalachian district of 
 North America are known as occurring on a large scale. Pro- 
 fessor Shaler is inclined to attribute them to glacial action, 
 because he knows of no other force that could bring together 
 such masses of pebbles from a wide-spread surface. In East- 
 ern Kentucky and East Tennessee these deposits are found to 
 be several hundred feet in thickness. Such accumulations of 
 apparent glacial origin are to be found from New Brunswick 
 to Alabama. 
 
 Hence it seems that the ice during a frigid period followed 
 down the Alleghany range even so far south as Georgia and 
 Alabama ; and for a time, when the ice attained its greatest 
 spread, it flowed over the central portion of the Gulf States. 
 For how else can we account for the clay mixed with gravel and 
 pebbles and stony fragments being spread broadcast over that 
 region ?
 
 70 
 
 I know that such statements do not agree with the views of 
 glacialists who have written on the subject, and have drawn 
 the glacial boundary from seven to ten degrees further north, 
 where a line of bowlders with other glacial debris is plainly 
 traced. Still, it appears to me that a line of bowlders de- 
 posited by an ice-sheet spreading over a continent and across 
 many degrees of latitude cannot be compared to the moraines 
 of inferior mountain glaciers of the temperate latitudes of the 
 present age. 
 
 An ice-sheet moving from a high latitude to a lower would, 
 while in the colder latitude, freeze firmly to the rocky ledges, 
 and hold them so strong in its frigid grasp as to break off the 
 weaker portions of the rocks, and drag them toward a milder 
 region, as far as the freezing grip of the ice-sheet would per- 
 mit ; but, on gaining lower and milder latitudes, the holding 
 and dragging power of the ice would be lost on account of the 
 increased warmth of the earth over which the glacier must 
 pass, and also because of the ice-sheet having lost a portion of 
 the low temperature acquired in the higher latitudes. There- 
 fore, on such lines the bowlders would be released, while the 
 ice-sheet would still move on, although largely deprived of its 
 eroding power. 
 
 This is the probable reason why a line of glacial debris, 
 largely composed of bowlders, is found to extend across the 
 Middle and Western States, and so generally supposed to be 
 the glacial boundary of a frigid period. But there is no reason 
 to suppose that an ice-sheet, although deprived of its eroding 
 power, was arrested in its southern movement on the line of its 
 stony ddbris, because there could be no sudden change of tem- 
 perature in a particular latitude on the eastern lands of North 
 America to cause an abrupt ending of the ice-sheets. And 
 there appears to be nothing to hinder the ice from gathering 
 and flowing over lands warm enough to loosen its implements 
 of erosion ; for there is much to show that the ice-sheets flowed 
 much further southward, even into the middle portion of the
 
 71 
 
 Gulf States, and there spread the clay mixed with gravel and 
 pebbles, with now and then a bowlder, over the land. The 
 scattered bowlders, found in numerous instances many miles 
 south of the bowlder line, were so deeply imbedded in the ice- 
 sheet that they could not be dropped on the usual releasing 
 ground. The ice-sheet, when deprived of its rocky, eroding 
 implements, would, while flowing over the land, leave few or 
 no imprints on the rocks ; but it would probably move and 
 spread a large amount of clay, gravel, pebbles, and sand over 
 its wide course, especially if the ice moved from a region 
 abounding with such material. 
 
 Should we place the glacial boundary on the line of the rocky 
 debris, how could we account for the glaciated stones found on 
 the hills and plains situated far southward of the bowlder- 
 strewn regions of the Middle and Western States ? The clay 
 mixed with gravel and sand, and spread so broadcast over 
 a large portion of Georgia and even into Northern Florida, 
 makes it appear that the ice of a cold period must have covered 
 that southern region. 
 
 Moreover, it seems to have been through the great abrasion 
 which only ice-sheets could perform that the sands of the 
 Florida peninsula were produced; for on examination they 
 seem to have resulted from the abrasion and weathering of 
 crystalline rocks. 
 
 The worn remnants of such rocks are now found in the 
 southern Appalachian range. In fact, the hills and mountains 
 of that region at the present time are supposed to be a small 
 remnant of the ancient highlands. Thus, on consideration, it 
 appears that the sands caused by the action of glaciers were, 
 on the disappearance of ice-sheets, blown by the strong north- 
 west winds toward the Florida peninsula as fast as the reced- 
 ing waters of the ocean which flowed the lowlands on the 
 breaking up of the ice age would permit ; and in this way the 
 sand was spread over the lowland region, which was largely 
 composed of coral sea shells and other marine matter. And it
 
 72 
 
 seems that the sand must have been blown over large areas in 
 Florida soon after the ending of the frigid period, because the 
 sand, in order to be moved by the winds, must have spread over 
 a country nearly destitute of vegetation ; and such would be 
 the condition of that region during times which succeeded the 
 ice period and the subsequent brief flowage of the lowlands on 
 the ending of the frigid age, which would not be the case if 
 such sands resulted entirely from water erosion and weather- 
 ing, because with such a state of things the country would be 
 covered with forests and grasses, which would prevent the sand 
 from being moved by the winds to any great extent. 
 
 This goes to show that the region of the Gulf States was so 
 much affected by the cold of the glacial period, together with 
 the submergence of the lowlands at its close, its flora and also 
 its animals were exterminated ; for how else can we account 
 for the abundant fossil remains of animals now found buried 
 in the Florida sands ? It appears also that, when Florida was 
 being covered with drifting sands, many of the lake basing now 
 formed did not exist, as the wind-blown sand could not have 
 crossed a continuous chain of lakes like the St. John's River ; 
 and it is an easy matter to-day to trace the beds of the ancient 
 lakes that prevented the sands from drifting over certain lands 
 now nearly destitute of it. And it is probable that the sea 
 flowed the lowest lands during the period when the winds were 
 drifting the greater portion of the sands over the peninsula. 
 Therefore, regions which embrace the Everglades and portions 
 of the Indian River territory are quite free from heavy sand 
 deposits, and so also are the extensive flat woods of the 
 peninsula. 
 
 Since the sands blew over the ancient desert of Florida, many 
 lake basins have been formed because of the sinking of the 
 ground. This sinking of the ground is a common occurrence 
 in limestone regions, where a great amount of material is 
 moved in solution, leaving caverns whose roofs often fall in. 
 The great amount of sand blown upon Florida caused the
 
 73 
 
 marine strata to give way in the weaker places under its 
 burden. The sinks thus formed, probably of frequent occur- 
 rence at one time, have now nearly ceased. Still, there are 
 depressions to be seen to-day where the tops of large pine-trees, 
 which grew on dry, sandy land, are barely above the surface of 
 the water which partly fills the basins so recently formed. Yet 
 I would not assert that all of the depressions where Florida 
 lakes exist were caused by the sinking of the ground ; for the 
 winds may have caused shallow basins in the sand, where the 
 decayed vegetation has formed mud sufficient to hold the water 
 which now partly fills such basins. 
 
 The mobility of Florida sands can be seen to good advantage 
 when exposed to a strong, dry north-west wind, where the 
 ground happens to be destitute of vegetation. An observer can 
 then realize what the result would be, should the whole land 
 be deprived of vegetation and laid bare to the action of the 
 winds. 
 
 Under such conditions, not only would the winds be much 
 stronger than now, but the air near the ground would be filled 
 with sand, moving like drifting snow in a Dakota blizzard. And, 
 furthermore, it is probable that the rainfall was very light 
 while Florida was void of vegetation ; and, even if shallow 
 basins were formed, there would be a lack of rain to supply 
 them with water. 
 
 The wide plains west of the Mississippi River, extending 
 southward into Texas, during the frigid period must have been 
 covered with a sheet of ice and snow. And it is probable that 
 it was not wholly a product of more northern latitudes, but 
 was mostly produced by the snow which fell on the plains 
 during the long winters of that period, which could not be 
 melted away during the cold summers of an ice age, when it is 
 considered that an ice-sheet, with a temperature sufficiently low 
 as to carry glacial drift, covered the lands of Missouri as far as 
 latitude 38 south ; and it may have been through the pressure 
 from an ice-sheet in its south-eastern movement that we are to
 
 74 
 
 account for the numerous ore-bearing faulting fissures travers- 
 ing the limestone strata. 
 
 The ice-sheet was also the probable cause of the erosion of 
 the horizontal bedded stones, yet it appears that the ice did 
 not greatly change the contour of the ground; for it is well 
 known that glaciers do move over lands that are not frozen to 
 the ice without causing much disturbance, especially where the 
 gradient is small, and this was the probable condition of the 
 Western plains during the ice age. Thus it seems that what- 
 ever disturbance this region has undergone could be partly 
 attributed to ice-sheets without the presence of bowlder drift, 
 because the temperature and texture of the ground in the lime- 
 stone region were unfavorable for such accumulations ; yet it 
 may be owing to the action of ice that minerals once diffused 
 are now found collected in fissures. The deep valleys through 
 which the large rivers now pass on their way toward the sea 
 were once filled with glaciers which flowed into them from 
 their tributaries. Thus the deep trenches of the plains are 
 largely the work of glaciers. It is generally supposed that 
 the driftless region of Wisconsin was free from ice during the 
 frigid period. But it seems impossible for this region to have 
 escaped being covered by ice and snow, with the great lakes 
 filled with glaciers, and the regions on all sides of the driftless 
 area covered with ice. 
 
 The reason why this territory escaped the drift from the 
 north was on account of the hindrance which the drift-bearing 
 ice-sheet encountered in the deep basin of Lake Superior. In 
 this great depression the ice-sheet from the north was relieved 
 of bowlders and other glacial drift, as well as obstructed in its 
 southern movement. 
 
 Therefore, the snow and ice which gathered on the driftless 
 region had little movement in any direction, while the temper- 
 ature and consistency of the ground under the ice were not 
 favorable for the production of bowlder drift ; and, when we 
 consider that the Mississippi valley was deprived of great
 
 75 
 
 sources of warmth during the culmination of a glacial period, 
 we are forced to the conclusion that its wide lands were also 
 covered with snow and ice. 
 
 The tropical waters of the North Atlantic were so much 
 chilled by the floating icebergs of North-eastern America, 
 Greenland, Iceland, and Northern Europe that the Caribbean 
 Sea, its warmest reservoir, was reduced to a temperature so 
 low that the easterly winds which blew over its waters were 
 unable to prevent ice-sheets from gathering on Eastern Nica- 
 ragua. 
 
 Therefore, during such frigid times it appears that, with the 
 waters of the Caribbean Sea and Gulf of Mexico reduced to a 
 low temperature, it was impossible for the great Mississippi 
 valley to escape glaciation, while being surrounded by cold seas 
 and glaciated lands which extended even into the tropical lati- 
 tudes. The broad, level lands of British America and Siberia 
 during the ice age must have been thickly covered by the snow 
 which fell on the deeply frozen plains, besides the large amount 
 of snow that the cold westerly winds must have drifted over 
 their icy surface from lands of greater snow-fall on their western 
 borders. This snow during such freezing times could not be 
 melted away. 
 
 The great ice-sheets thus formed over wide, level lands could 
 have but little motion in any direction, certainly not sufficient 
 to cause glacial drift of much magnitude ; yet the ice-sheet, at 
 one stage of its existence, probably served to widen and deepen 
 the channels of the great rivers which empty into the Arctic 
 Ocean from these vast regions, and the glacial debris from such 
 erosion was deposited in the arctic seas.
 
 76 
 
 CHAPTER V. 
 
 REMARKS ON THEORIES ADVANCED FOR EXPLAINING ICE 
 PERIODS. 
 
 ON Nov. 12, 1891, Professor Geikie made his presidential 
 address before the Edinburgh Geological Society, the subject 
 being " Supposed Causes of the Glacial Period." 
 
 Many of his views advanced in this lecture were so much in 
 accordance with my own that I am induced to repeat them. 
 He safd that the glacial period was a general phenomenon due 
 to some widely acting cause, and that where we now have the 
 greatest rain-fall the greatest snow-fall took place, and that the 
 Pleistocene period was characterized by great oscillations of 
 climate, extremely cold and very genial conditions alternating. 
 He also said that in glacial and post-glacial times changes in 
 the relative level of the land and sea had taken place, and any 
 suggested explanation which did not fully account for these 
 various climatic and geographical conditions could not be satis- 
 factory. And, while examining the earth-movement hypoth- 
 esis, he pointed out that in the first place there was not the 
 least evidence of great continental elevations and depressions 
 in the northern hemisphere, such as the hypothesis postulated. 
 Next he showed that, even if the diserrated earth-movements 
 were admitted, they would not account for the phenomena. 
 
 Such changes, no doubt, would profoundly affect the maritime 
 regions of North America and Europe; but they would not 
 bring about the conditions that obtained at the climax of the 
 ice age. 
 
 Another objection to the earth-movement hypothesis was 
 this : it did not account for interglacial conditions. The advo- 
 cates of that hypothesis imagined that these conditions would 
 supervene when the highly elevated northern regions were de- 
 pressed to their present level. But these were the conditions
 
 77 
 
 that obtained at the present time ; and yet in spite of them the 
 climate was neither so equable nor so genial as that which ob- 
 tained in interglacial times and during the mild stage of the 
 necessary post-glacial period. 
 
 Therefore, he said that the earth-movement hypothesis should 
 be rejected, not only because it was highly improbable that such 
 wonderfully rhythmic elevations and depressions of northern 
 lands could have taken place, but chiefly because it did not 
 explain the conditions of the glacial periods and interglacial 
 times. 
 
 Still, Professor Geikie says that in glacial and in post-glacial 
 times changes in the relative level of the land and sea had taken 
 place ; and it is reasonable to suppose that such changes were 
 obtained in the high latitudes of both hemispheres during the 
 breaking up of the last ice age. 
 
 We have previously pointed out that much of the ice of the 
 glacial period in the southern hemisphere was melted away, 
 and its waters warmed sufficiently to assist the Gulf Stream 
 and Japanese current to bring about a mild period in the north- 
 ern hemisphere; for without such assistance they would be 
 unable to disperse the vast ice-sheets of the northern latitudes. 
 
 Still, the attraction of the southern ocean waters into the 
 northern seas must have commenced as soon as the growing 
 ice-sheets of the large continents and islands of the high north- 
 ern latitudes surpassed the growth and weight of the glaciers 
 on the smaller lands of the southern hemisphere. 
 
 Hence the attraction of the ocean waters northward over- 
 comes the force of the prevailing winds from moving an undue 
 portion of the ocean's surface waters southward. Consequently, 
 the movement of water from the southern seas into the northern 
 latitudes continued so long as the vast northern ice- sheets in- 
 creased in weight greater than the glaciers of the southern 
 hemisphere. Therefore, at the perfection of a frigid age straits 
 and channels situated so far southward as the Magellan and 
 Cape Horn channels were much diminished in width and depth
 
 78 
 
 or entirely deprived of their waters. Through this cause such 
 reduced channels were readily filled with glaciers in a region of 
 great snow-fall. The depth of water on the submerged northern 
 lands at the close of the glacial period is not known. 
 
 According to Professor Dawson, in the township of Montague 
 in Ontario the skeleton of a whale was found in post-glacial 
 deposits 440 feet above tide-water, and marine shells are 
 known to occur on Montreal mountain at an elevation of 520 
 feet above the ocean ; and it is said that there are traces of 
 submergence of over one thousand feet in the higher latitudes, 
 including the islands of Great Britain. 
 
 According to the researches of Dr. J. W. Spencer, one great 
 sheet of water covered most of the great lake region about the 
 close of the ice age; and the lower strands of these inland 
 seas are known to be connected with old marine shore lines. 
 The probable reason why so few sea-shells collected on the 
 glacial drift during such times was because of so much marine 
 life having been exterminated in the high northern latitudes 
 during the frigid age. Therefore, the sea, in the short period 
 of northern submergence, left but few traces on the glacial 
 drift it once flowed. 
 
 Thus it will be seen that, if the ocean waters were attracted 
 northward through the preponderance of northern ice-sheets, 
 they not only assisted in melting the northern ice, but also 
 served to greatly reduce the waters in the Cape Horn channel, 
 and so largely prevented the independent circulation of the 
 southern ocean, thus furthering a mild climate in the southern 
 hemisphere until the prevailing winds, after the northern ice- 
 sheets were melted, were able to move more of the ocean waters 
 southward than they could move northward, owing to the ocean 
 currents setting southward being less obstructed than the lesser 
 currents setting northward. This tendency of the ocean waters 
 to move southward I have before explained in the preceding 
 pages. 
 
 But I will say in addition that, on further consideration, it
 
 79 
 
 seems that one of the main causes of the waters of the aug- 
 mented northern oceans moving southward so soon after the 
 melting of the ice from the northern lands was on account 
 of so much water being attracted southward to the great low 
 sea-level east of Cape Horn. This vast low sea-level remained 
 a great area of attraction for the northern seas until so much 
 northern water was moved into the southern ocean as to reduce 
 the seas of the northern hemisphere and augment the southern 
 ocean sufficiently to enlarge the Cape Horn channel, thus caus- 
 ing the extinction of the vast low sea-level that furnished such 
 great attraction for the waters of the more northern latitudes. 
 
 If the earth-movement hypothesis, so wholly rejected by Pro- 
 fessor Geikie, fails to explain the cause or causes of a northern 
 ice age, it seems to be still more inadequate for explaining the 
 occurrence of ice periods extending over both hemispheres. 
 For it is not probable that portions of continents and large 
 islands rose above the snow-line in both temperate zones during 
 the same period of time, and then again obtained their present 
 level with the occurrence of a mild era. 
 
 Those who maintain that the continents of North America 
 and Europe rose to great elevations during the ice age, in order 
 to prove their assertions, point to the fiords which indent the east- 
 ern and western coasts of North America, and also to the fiords 
 of Norway, as having been eroded by streams of ice that flowed 
 along the bottom of such gorges when they were above the sea. 
 
 But it appears that such erosion could be performed by heavy 
 glaciers with the lands at their present level. A glacier three 
 thousand feet thick would fill and press heavily on the bottom 
 of a gorge fifteen hundred feet in depth. Therefore, should 
 the bottom of a fiord sink hundreds of feet below the sea-level, 
 a glacier several thousand feet thick flowing through and over 
 it into a sea of much greater depth, the erosion at the bottom 
 of the sunken channel would be greater than on the land above 
 the sea, where the ice possessed less weight. 
 
 Therefore, it is not necessary that lauds pierced by deep
 
 80 
 
 fiords should have acquired a higher level during the ice age 
 than they now maintain. And it is probable that on the ant- 
 arctic continent ice erosion may be going on at much greater 
 depths below the sea-level than the deepest channels in the 
 high northern latitudes. For it is likely that the temperature 
 of a glacier is so low in such frigid regions that it holds firmly 
 in its freezing grasp such bowlders as may become detached 
 from the rocks, thus giving it great erosive power. 
 
 But this great eroding ability could not be maintained by 
 glaciers in the lower latitudes, where a higher temperature 
 would largely deprive the ice of its abrading properties except 
 on the steep slopes of mountainous lands. 
 
 There are deposits of ice on the North American coast bor- 
 dering the arctic shores, and also on Northern Siberia, that are 
 supposed to have existed since the last frigid period, and are 
 likely to be preserved into a future cold age, which now appears 
 to have made considerable progress on Greenland and other 
 ice-clad arctic shores on account of the independent circulation 
 of the Arctic Ocean waters, which largely excludes the Gulf 
 Stream from the polar seas ; and it is for this reason that the 
 glaciers on the elevated lands of Iceland are being enlarged 
 and rapidly advancing. Yet, notwithstanding the gathering of 
 ice and increasing coldness of lands largely removed from the 
 warm Gulf currents, there are still mountain regions where 
 glaciers may have been preserved through post-glacial times, 
 although directly to the leeward and under the influence 
 of the Gulf Stream and Japanese currents. These glaciers are 
 situated in the Alpine districts of Europe and on the mountain 
 ranges of Alaska. It would appear that, were the climate 
 growing gradually colder in the northern temperate zones, such 
 glaciers should be increasing in size. 
 
 Yet it is said that such is not always the case. This is prob- 
 ably owing to their being subject to the genial influence of 
 the tropical currents. For, although the climate of Europe 
 and Alaska may have been slowly growing colder for centuries,
 
 81 
 
 still the slow shrinkage of these once immense glaciers may 
 still be going on, although at a much slower rate than formerly, 
 even if the tender plants of these latitudes, because of the 
 growing coldness, have gradually moved southward. 
 
 As to the Alpine glaciers, M. Forel reports from data he has 
 collected that there have been several enlargements and dim- 
 inutions during the last century. And since 1875 enlargements 
 have taken place, their shrinkage being caused by warm and 
 dry weather, while their enlargement was brought about dur- 
 ing cold and rainy seasons. The glaciers of Alaska cannot at- 
 tain much extension until the waters of the great Japanese 
 stream acquire a lower temperature. There is at this date a 
 small current setting down through the eastern side of Bering 
 Strait, bearing field-ice in the spring season down to Anadyr 
 Gulf. The Okhotsk Sea in the spring season furnishes consid- 
 erable field-ice to cool the north Pacific waters, and the wintry 
 winds which sweep down from the high lands of Northern Asia 
 also serve to chill the Pacific seas ; but all such sources of cold 
 combined at this age have but little general effect on the vast 
 Japanese current, which still has warmth sufficient to prevent 
 the increase of glaciers on Alaska. 
 
 This great ocean stream in its impact against the shores of 
 Oregon causes a high sea-level, which is mostly turned south- 
 ward by the prevailing north-west winds. Still, a compara- 
 tively small stream sets along the shore of the Alaska Gulf, and 
 also through the island passages toward a slight low sea-level, 
 to the leeward of the Alaska peninsula ; and it is probable 
 that this current which warms these in-shore waters is favored 
 by the difference of temperature and density between the 
 waters abreast Oregon and the Gulf of Alaska, and it may be 
 owing to the same cause that a small stream is sent along the 
 eastern shore of Bering Strait into the deep portions of the 
 Arctic Ocean. Thus because of the warm waters that proceed 
 from the great Japanese current the glaciers of Alaska are 
 prevented from increasing their bulk.
 
 82 
 
 The only way to furnish the Japanese stream with colder 
 water, and so cause glaciers to increase on the north-west coast 
 of America, is through the great Humboldt current, which has 
 its rise in the southern ocean west of Patagonia and the Cape 
 Horn channel, where a moderate but vast high sea-level is 
 formed on account of the great drift current of the southern 
 ocean being somewhat obstructed on its passage through the 
 Cape Horn channel, which is about one-third the breadth of 
 the westerly wind-belt. 
 
 Therefore, the northern portion of the waters of the high 
 sea-level so caused are attracted northward to the low sea-level 
 abreast Peru, from whence they are moved by the south-east 
 trade winds as a drift current to the equatorial latitudes, thus 
 meeting and mingling with the returning Japanese current 
 abreast Central America, and so giving head to the great 
 equatorial stream which moves westward over the Pacific 
 Ocean, partly impelled by the trade winds, and, on gaining 
 the western side of the ocean, sends off from a moderate high 
 sea-level a large stream to the low sea-level caused by the 
 westerly winds abreast Japan, from whence it is drifted by 
 the same winds over to the north-west coast of America, thus 
 forming the great Japanese current. 
 
 Meanwhile the temperature of the Humboldt current, being 
 governed by the temperature of the southern ocean from which 
 it takes its rise, is cooling at a slow rate through the enlarge- 
 ment of ice-sheets in the antarctic regions, while the increase of 
 glaciers on Patagonia will in time greatly add to its coolness, 
 and so lower the temperature of the equatorial current from 
 which the Japanese current branches, the latter current being 
 made cooler through the increase of coldness of the former 
 streams. Therefore, the temperature of Alaska, which is 
 governed by the Japanese current, will slowly acquire a colder 
 climate ; and, consequently, its glaciers will increase in size 
 sufficient to launch icebergs into the Pacific to be currented 
 southward, and so still further lower the temperature of the
 
 83 
 
 Eastern Pacific waters, and consequently the equatorial current 
 from which the Japanese stream branches, and so eventually, 
 under the above conditions, cause heavy ice-sheets to spread 
 widely over the north-west coast of North America. 
 
 It will be seen from the above explanations how an increase 
 of cold in the southern hemisphere is necessary to cause a wider 
 spread of ice-sheets on lands in the northern hemisphere. 
 
 Especially is this the case to promote the gathering of 
 glaciers on the west coast of North America. The great 
 equatorial current while on its way to the Indian Ocean not 
 only sends off the Japanese stream, but also the East Austral- 
 ian current, which is like the Japanese current, having its 
 temperature lowered in proportion as the equatorial stream 
 is cooled. Therefore, the southern ocean is slowly being 
 deprived of equatorial heat from this source. 
 
 I have explained how the increasing coldness of the superior 
 oceans of the southern hemisphere affects more or less the 
 temperature of the Gulf Stream, which meanwhile is only able 
 to enter a small portion of its waters into the Arctic Ocean 
 after undergoing a long cooling process as a drift current; 
 and, while thus mingling with the arctic waters, it is not able 
 to prevent the gathering of ice-sheets on Greenland, where 
 glaciers are launching bergs to float southward as far as the 
 latitude of 40 north. Consequently, the northern seas are 
 now being cooled as well as the seas of the southern hemi- 
 sphere. 
 
 Yet this cooling process is so slow there is a lack of data to 
 show that the temperature of the high latitudes is lowering. 
 Our thermometrical observations are of such recent date 
 they cannot be used to determine climatic changes which re- 
 quires centuries to bring about. Still, it is generally known 
 that the climate of Northern Europe has been accused of 
 growing colder. The vine no longer flourishes on the shores 
 of Bristol Channel or hi Flanders or Brittany ; and vineyards 
 are no longer planted on the elevated shores of France where
 
 84 
 
 they flourished three hundred years ago. Arago did not re- 
 fuse to believe that the laws regulating the temperature of 
 Western Europe had notably altered. This is proved, he said, 
 by the general retrogradation of the vineyards southward. 
 
 The recent deadly freezing of the orange groves of Florida 
 makes it uncertain whether the cultivation of the orange can 
 again be successful in the counties where during this genera- 
 tion it has been very profitable. 
 
 Travellers visiting Iceland say that the old accounts of its 
 prosperity seem strange to those who now visit its shores ; 
 and it is narrated in the Sagas that in early times sheep could 
 shift for themselves during winter, and that there were 
 large forests and that corn ripened. Several years ago a cor- 
 respondent of the Spectator, writing from Northern Russia 
 where the Volga is locked with ice for six months in the year, 
 stated that "the people were beginning to show increased re- 
 sentment at the climate, and that there was reason to believe 
 that the northern government of Russia would be abandoned 
 to the desert. The people silently glide south by the tens of 
 thousands every year, so the life of Russia was concentrating 
 in the south." 
 
 It is now the opinion of travellers in arctic lands that the 
 inhabitants of the Esquimaux regions are decreasing, as are 
 also the inhabitants of Northern Siberia. 
 
 A writer in the North China Herald, of Shanghai, says that 
 " the climate of Asia is becoming colder than it formerly was, 
 and its tropical animals and plants are retreating southward 
 at a slow rate. In the time of Confucius elephants were in use 
 on the Yangtse River. A hundred and fifty years after this 
 Mencius speaks of the tiger, the leopard, the rhinoceros, and 
 the elephant as being in many parts of China. 
 
 " It is also said that the ferocious alligator, that formerly in- 
 fested the rivers of South China, has retreated southward. 
 
 " The flora of the country is also affected by the increasing 
 coldness of the climate. The bamboo is not found in the for-
 
 85 
 
 ests of North China, where it grew naturally two thousand 
 years ago, but is still grown in Pekin, with the aid of good 
 shelter, as a sort of garden plant only." 
 
 A letter from Hong Kong, published in the London Stand- 
 ard, reports that on the 15th of January, 1893, the temperature 
 of Hong Kong, a tropical seaport of China, was below freez- 
 ing for three days, and was colder than ever before known. 
 The rocks and also vegetation were covered with a coating of 
 ice. The thermometer at times stood at 23 and 26 Fahren- 
 heit. 
 
 I have previously explained how the slow increasing coldness 
 of the northern temperate zone is also being carried out in the 
 southern hemisphere. The meteorological records for the lofty 
 table lands of Ecuador, although very incomplete, furnish 
 strong evidence to show that the mean temperature of that 
 region is gradually lowering. 
 
 Observations made by Boussingault at Quito in 1831, com- 
 pared with those from 1878 to 1881, showed a decrease from 
 15.2 Centigrade to 13.27 Centigrade. 
 
 Records made by Hall from 1825 to 1827 give averages of 
 16.1 Centigrade, 15.52 Centigrade, and 15.6 Centigrade. 
 This decrease holds good for all points in the inter- Andean 
 region where records have been kept. 
 
 Yet we know that the falling temperature in the northern 
 temperate latitudes is not brought about by a yearly increase 
 of cold, because, when the arctic channels are somewhat ob- 
 structed with icebergs, the movement of arctic waters through 
 them is lessened ; and, therefore, during such times the Gulf 
 Stream, meeting with less opposition from arctic currents while 
 flowing northward, is able to move a larger volume of its 
 waters into the arctic seas, thus warming their waters suffi- 
 ciently in a few seasons to clear the obstructed channels, and 
 also somewhat soften for several successive years the temper- 
 ature of such lands as border on the seas of that region. 
 
 And in this way we account for the mild seasons which at
 
 86 
 
 times follow those of lower temperature in high northern lati- 
 tudes. 
 
 But, when the detained icebergs are set adrift, and currented 
 into the temperate North Atlantic, the heat consumed while 
 melting such numerous bodies of ice is able to more than over- 
 come the warmth gained during the temporary detention of ice 
 in the northern seas. Thus, under such considerations, it ap- 
 pears that the conditions are favorable for the growth of gla- 
 ciers in the high northern latitudes. 
 
 I have pointed out the manner in which the superior oceans 
 in the southern hemisphere are obtaining a lower temperature, 
 and how they impart their coldness to the tropical currents, 
 and in this way slowly cool the waters of all oceans. Thus it 
 appears that the northern temperate zone, with all other parts 
 of the earth, is slowly approaching a cold epoch. 
 
 Several writers on climatic changes have expressed their 
 views as to the number of glacial and mild periods that have 
 been perfected since the conditions have been favorable for 
 their appearance on the globe. According to my views, while 
 considering the reasons for the occurrence of the great glacial 
 periods which have left such extensive traces on the land, it 
 seems certain that two very cold epochs have possessed the 
 earth, separated by a warm period ; and, possibly, other pre- 
 ceding cold epochs of less intensity have possessed the high 
 latitudes, with intervening periods of mildness. But the earlier 
 cold periods, if they ever existed, were comparatively short, 
 because the Cape Horn channel during such times possessed 
 less capacity than in the later periods, and, therefore, was more 
 easily and quickly obstructed by the natural methods previously 
 explained. 
 
 Consequently, the independent circulation of the southern 
 ocean was sooner arrested than during the later epoch, when 
 the channel had become enlarged by erosion from heavy gla- 
 ciers and icebergs; and meanwhile the same conditions may 
 have governed the arctic channels which give an independent
 
 87 
 
 circulation to the arctic waters which surround Greenland, and 
 thus, in connection with cold epochs in the southern hemisphere, 
 have caused periods of cold of small intensity to occur in the 
 high northern latitudes, and it may happen in the future that 
 more ice periods will be perfected than the one now progressing. 
 
 Still, it is well to bear in mind that the Cape Horn channel, 
 which is the real cause of glacial periods having occurred in 
 both the northern and southern hemispheres, in the manner 
 previously explained, is being made wider and deeper during 
 each succeeding ice age. For this reason the latest cold epoch 
 will require a longer continuance of cold to obstruct the chan- 
 nel than the cold period preceding. Therefore, it appears that 
 the time will come when there will be such great accumulations 
 of ice stored on the land and in the sea before the enlarged 
 Cape Horn channel can be closed that, when it is closed, there 
 will not be sufficient warmth remaining in the tropical seas to 
 unite with the sun's rays to subdue the intense cold stored in 
 the immense gatherings of ice. And thus the earth, which 
 began its career with a warm temperature, and so continued 
 for long ages, will finally terminate in an endless glacial age. 
 
 The statements made by General Cowell in Science of Nov. 25, 
 1892, in reference to the alleged discovery of the second rota- 
 tion of the earth by Major-general Drayson, represents the dis- 
 covery as affording a new solution for the cause or causes of an 
 ice age. 
 
 The second rotation as defined consists in the pole of the 
 heavens describing a circle around a point which is ascertained 
 to be situated six degrees distant from the pole of the ecliptic. 
 And it is asserted that by a knowledge of the second rotation 
 it is proved that a variation of twelve degrees in the extent of 
 the arctic circle and the tropics occurred not later than 13,500 
 B.C., "the tropics varying in distance from the equator from 
 the minimum of 23 25' 47" to the maximum of 35 25' 47", 
 thus extending the torrid zone during its widest expansion 
 from Cape Hatteras to the river Plate. ... It is calculated that
 
 88 
 
 at this date we are about 403 years distant from the time when 
 the pole of the heavens in its revolution, the pole of the ecliptic 
 and that of the second rotation, will be in the same colure, 
 that is, in the year 2,295 A.D. ; and then the least differences in 
 temperature between summer and winter will be experienced. 
 From that time forward this difference will increase, and about 
 6,000 years later, or about the year 8,300 A.D., the earth will 
 enter the next glacial period, and attain its greatest severity 
 about the year 18,136 of our era." General Cowell does not 
 state how the widening of the tropical zone, as above set forth, 
 would bring about a glacial period. The winters of the tem- 
 perate zones would evidently be colder than now ; but, on the 
 other hand, the summers would be proportionally warmer, 
 while the westerly winds above the latitudes of 40 would pre- 
 vail the same as now. 
 
 Therefore, their general effect on the surface waters of the 
 ocean in the high latitudes would not be changed with such an 
 extension of the tropical zone, neither would the trade winds 
 change their general direction with a wider torrid zone ; yet 
 the boundaries of the trade winds and also the westerly winds 
 would be more shifting according to the declination of the sun, 
 such winds being governed as now by the position of the sun 
 during the summer and winter solstice. Yet the natural proc- 
 ess for moving tropical water into the high latitudes, or ex- 
 cluding it therefrom, would not be greatly changed. 
 
 Consequently, the expansion of the torrid zone to the latitudes 
 named by General Drayson would not affect the climate of the 
 hemispheres sufficiently to cause a frigid epoch. On the con- 
 trary, the summer monsoons, which now blow from the north- 
 east, along the shores of Eastern Africa, and also along the 
 coast of Southern Brazil, would be much stronger with a verti- 
 cal sun in midsummer as far south as river Plate, thus forcing 
 the surface waters of the tropical oceans into the higher lati- 
 tudes with greater facility than at this age. 
 
 Moreover, according to the statements of General Cowell, the
 
 89 
 
 present period of mildness should be on the increase, and obtain 
 perfection in the year 2,295, or about 400 years hence; while, 
 on the contrary, according to the explanations we have given 
 in the preceding pages, there is much to show that an ice age 
 is advancing, and has made considerable progress in the high 
 latitudes of both hemispheres. Furthermore, if the second 
 rotation, as claimed by General Cowell, is able to perfect a 
 glacial period at regular intervals of 31,600 years, it seems that 
 traces of frigid epochs should not be confined to late geological 
 records, as there appear to be little or no traces of glacial work 
 prior to the Quaternary or Post-tertiary periods. 
 
 It appears that explanations so far given, which depend on 
 the astronomical theory to account for the ice age, are not in 
 harmony with well-known geographical facts. The explainers 
 neglect the attention due to the great prevailing winds which 
 since the earlier geological ages have, in connection with conti- 
 nents, moved the surface waters of the ocean from torrid lati- 
 tudes to colder zones, and from the colder zones to the warmer 
 latitudes. 
 
 This exchange of ocean waters between the zones is as old 
 as the continents which shape their courses. The important 
 change wrought in the ocean currents sufficient to have caused 
 the glacial age which ended the early warm epochs was brought 
 about through the action of the prevailing winds, which, in 
 connection with the form of continents, became able to move 
 the ocean waters from the northern hemisphere into the south- 
 ern sufficient to submerge the low lands of the southern hemi- 
 sphere, causing a great diversion of the tropical currents from 
 the high southern latitudes, such as I have pointed out in pre- 
 ceding chapters. 
 
 Those writers who believe that ocean currents have been the 
 cause of great climatic changes have suggested that the exist- 
 ence of an ancient channel through the isthmus of Panama 
 would have caused a frigid period on lands bordering on the 
 northern shores of the Atlantic by turning the head-waters of 
 the Gulf Stream into the Pacific Ocean.
 
 90 
 
 Professor Agassiz thinks that such a channel existed during 
 some remote geological age, judging from the semblance of the 
 fauna pertaining to the Caribbean Sea and Pacific Ocean. 
 
 Yet it may be said that an open channel through Central 
 America would have connected two high sea-levels. 
 
 For this reason there would be little or no exchange of water 
 between the Caribbean Sea and the Pacific Ocean. 
 
 The high sea-level on the Pacific side is caused by the pre- 
 vailing north-west winds which blow down the North American 
 coast past California as far south as Central America ; while, 
 on the other hand, the south-east trade winds impel the surface 
 waters of the South Pacific along the coast of Peru down to 
 the equator, and so onward 5 to 8 north latitude. Thus the 
 space between the ending of the two ocean winds obtains a high 
 sea-level, corresponding to the high level of the Caribbean Sea. 
 This has been proved from levellings for the Nicaragua ship 
 canal. 
 
 Consequently, the Atlantic waters would not run into the 
 Pacific Ocean, even if a channel opened through Central 
 America. 
 
 Therefore, the Gulf Stream has never been turned away 
 from the North Atlantic. 
 
 Writers, while seeking a cause for the mild climate of ages 
 preceding the glacial epochs, have thought that during such 
 times channels opening through Asia from the Indian Ocean 
 by the way of the Persian Gulf into the arctic seas would be 
 the means of furnishing the Arctic Ocean with warm water. 
 But it is evident that such a movement of water could not be 
 brought about, because the winds would not be favorable for 
 it. For, when we reflect that the prevailing winds would blow 
 in the same direction as now, and that the seas of Eastern Eu- 
 rope and Western Asia were enlarged during the warm epochs, 
 it seems that they would obtain high levels superior to the 
 high level seas of the Indian Ocean. 
 
 Besides, we should consider that there is a continuous range
 
 91 
 
 of high land separating the Persian Gulf from the northern 
 seas, which probably existed anterior to the ice age. Still, 
 during later periods, while the ice-sheets were being melted 
 from the northern hemisphere and also on the ending of the 
 last ice age, the Isthmus of Suez was submerged, as were all 
 other low lands in that latitude; but it is probable that the 
 waters of the high sea-level of the Indian Ocean abreast tropi- 
 cal Africa did not flow largely into the Mediterranean Sea for 
 the reason that the enlarged European seas, being within the 
 westerly wind-belt, maintained a high sea-level, while at the 
 same time the high level tropical Indian Ocean waters were 
 strongly attracted into the southern oceans through the Mo- 
 zambique and Agulhas currents in the manner I have pre- 
 viously explained. Yet the waters of the high sea-level of the 
 southern European seas must have been strongly attracted to 
 the low sea-level abreast the Canary Islands. 
 
 While considering the causes which brought about the 
 glacial periods, it is well to reflect that the natural mode of 
 action which could have produced a frigid age was as exten- 
 sive as the surface of the globe ; and, therefore, any geographi- 
 cal change that would affect only a comparatively small por- 
 tion of the earth cannot serve to account for ages of warmth 
 which extended over the globe, or for glacial epochs which 
 were separated by warm periods of time, which seem to have 
 affected all lands and seas. 
 
 And it appears from the geographical explanations given in 
 preceding pages of the general movements of the winds and 
 currents of the sea how impossible it is for heat to be con- 
 veyed to the antarctic latitudes sufficient to prevent the growth 
 of glaciers on their lands while the Cape Horn channel is in 
 possession of its present capacity. 
 
 For, as has been shown, this channel furnishes opportunity 
 for the westerly winds to impel the surface waters of the great 
 southern ocean constantly around the globe, and so largely 
 turns away the tropical currents from the high southern lati- 
 tudes.
 
 92 
 
 Consequently, there seems to be no method yet devised 
 through nature's mode of action that can carry sufficient heat 
 into the antarctic latitudes to melt the ice-sheets from the 
 southern continent, or even arrest their growth, while the Cape 
 Horn channel maintains its present width and depth. 
 
 Therefore, the increase of glaciers and icebergs will slowly 
 continue until a glacial epoch is perfected. 
 
 And it seems that this arrangement for bringing about a 
 frigid age made slower progress in its early stage than at this 
 date, owing to there having been a lack of glacial ice in the 
 polar regions to produce icebergs for cooling the ocean waters. 
 But the independent circulation of the great southern ocean, 
 after turning away the tropical currents from the high southern 
 latitudes for thousands of years, did at length cause glaciers to 
 form on the antarctic lands, which have been slowly, but con- 
 stantly increasing ; and, consequently, the cooling of the ocean 
 has been accelerated proportionate to the increase of ice-sheets. 
 Therefore, with the cooling process so well advanced as it now 
 appears to be, it seems that more than half of the time required 
 to bring a frigid age to perfection has been expended since ice- 
 sheets began to gather on the antarctic shores. For, when we 
 realize how the facilities for making ice have advanced through 
 the increase of glaciers in both hemispheres, and how large a 
 portion of the ocean waters have been cooled below a temperate 
 or tropical temperature even in the torrid latitudes where the 
 warm upper waters of the ocean have been reduced to a com- 
 paratively thin stratum when compared to the vast bulk of 
 the cooled under waters, it appears that the cold will increase 
 at a faster rate for the next thousand years than was the case 
 during the last ten centuries. Therefore, the climate will be 
 less favorable for plants and animals existing on lands in the 
 high latitudes for the next thousand years than during the ten 
 centuries preceding; and, when we take into consideration 
 the accelerative growth of a frigid epoch, it seems that the in- 
 creasing cold will in a few thousand years drive the greater
 
 93 
 
 portion of both plants and animals from the now temperate 
 latitudes to maintain an existence in the tropical zone, where a 
 large part of the existing species of such life must have taken 
 refuge during the last ice period. 
 
 And, from what can be learned from the relics of man's pre- 
 historic life, it seems to point to the lands of the tropical lati- 
 tudes as having been his home during the frigid ages ; and, 
 because of his long undisturbed residence in favored portions 
 of the tropics, he there attained his earliest civilization. For it 
 appears that the tropical zone was not only less burdened with 
 ice in glacial times than the higher latitudes of the globe, but 
 was also more exempt from the great flooding of lands which 
 obtained in the more northern latitudes through the shifting of 
 the ocean waters, from causes set forth in the preceding pages. 
 Yet it may be said that the low lands of the tropical zone 
 south of the equator during cold epochs were much more ex- 
 tensive than at this age, on account of the shrinkage of the sea, 
 because of the great amount of water evaporated from its sur- 
 face, and stored in ice-sheets on the great continents and 
 islands. Hence the reefs and shallows which surround such 
 tropical islands as include the Seychelles Archipelago, and also 
 the extensive banks covered with shoal water in that portion of 
 the Indian Ocean, were during the glacial period elevated above 
 the surface of the sea, possessing a climate favorable for 
 vegetable and animal life. But, owing to the great rain-fall of 
 that region, it is probable that the highest lands were glaciated, 
 as it is reported that granite bowlders still rest on the moun- 
 tain slopes of the highest island. The numerous islands and 
 shoals of the south-western tropical Pacific must ; also have 
 afforded wide land areas, with a temperate climate, owing to 
 their having been situated on one of the warmest regions of 
 the earth during the ice age. 
 
 Moreover, it is probable that these tropical lands afforded 
 space for numerous lagoons which had little connection with 
 the surrounding oceans, and consequently were able to main-
 
 94 
 
 tain, in their secluded shallow basins, a warmer temperature 
 than obtained in the open seas ; and at the same time, owing 
 to the great rainfall in such tropicalfportions of the Indian and 
 Pacific regions, the waters of the lagoons were rendered less 
 salt than the briny depths of the shrunken oceans of a cold 
 period. Hence because of such conditions the fauna of the 
 tropical seas were preserved from the destructive rigor which 
 beset the earth during the frigid epochs.
 
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