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A. M. Taber - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: The Coming Ice Age - -Author: C. A. M. Taber - -Release Date: August 29, 2019 [EBook #60195] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE COMING ICE AGE *** - - - - -Produced by Tim Lindell, Charlie Howard, and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive/American Libraries.) - - - - - - -</pre> - - -<div id="map1" class="figcenter" style="max-width: 50em;"> - <img src="images/map1.png" width="800" height="1145" alt="Map 1" /> - <div class="caption">No. 1.<br /> - <p class="small">THIS MAP SHOWS THE SPREAD OF GLACIERS AND ICEBERGS, AND THE EXTENSION - OF SOUTHERN LANDS DURING ICE AGE AND ALSO THE DIRECTION OF WINDS AND - OCEAN CURRENTS.</p> - </div> -</div> - -<div id="map2" class="figcenter" style="max-width: 50em;"> - <img src="images/map2.png" width="800" height="1158" alt="Map 2" /> - <div class="caption">No. 2.<br /> - <p class="small">THIS MAP SHOWS THE SPREAD OF GLACIERS AND ICEBERGS AND THE DIRECTION - OF WINDS AND CURRENTS AT THIS DATE.</p> - </div> -</div> - -<hr /> - -<h1><span class="xxsmall">THE</span><br /> - -<span class="smcap">Coming Ice Age</span>.</h1> - -<p class="p2 center vspace">BY<br /> -<span class="larger wspace">C. A. M. TABER.</span></p> - -<p class="p2 center vspace wspace">BOSTON:<br /> -<span class="smcap">Geo. H. Ellis, 141 Franklin Street</span>. -<span class="smaller">1896.</span> -</p> - -<hr /> - -<p class="newpage p4 center small"> -<span class="smcap">Copyright, 1896.<br /> -By C. A. M. Taber.</span></p> - -<p class="p4 center xsmall"><span class="bt">GEO. H. ELLIS, PRINTER, 141 FRANKLIN STREET, BOSTON.</span> -</p> - -<hr /> - -<p><span class="pagenum" id="Page_3">3</span></p> - -<div class="chapter"> -<h2 id="PREFACE">PREFACE.</h2> -</div> - -<p><span class="firstword">The</span> 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 circulated, -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 geography. -Besides, it received considerate notice in some of the -leading reviews. Being thus somewhat encouraged, and thinking -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 volume -than in my earlier writings. Still, while acting as a pioneer -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 repeat -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<span class="pagenum" id="Page_4">4</span> -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 experience -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 subject, -which have been published in <cite>Science</cite> and <cite class="smcap">Scientific American</cite>. -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.”</p> - -<p class="in0 in1"> -<span class="smcap">Wakefield, Mass., U.S.A.</span><br /> -<span class="in3">June, 1896.</span></p> - -<hr /> - -<p><span class="pagenum" id="Page_5">5</span></p> - -<div class="chapter"> -<h2 id="CONTENTS">CONTENTS.</h2> -</div> - -<table id="toc" summary="Contents"> - <tr> - <td class="tdc chap" colspan="2"><a href="#CHAPTER_I">CHAPTER I</a>.</td></tr> - <tr class="small"> - <td> </td> - <td class="tdr" style="width: 5em;">PAGE</td></tr> - <tr class="bpad"> - <td class="chapsub"><span class="smcap">Cause of cold and mild periods</span>,</td> - <td class="tdr"><a href="#CHAPTER_I">9–36</a></td></tr> - <tr> - <td class="tdl">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 Larsen’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 during ice age, 28; direction of surface currents in southern seas, 29; Humboldt current, 30; Agulhas current, 32; temperature of arctic ice, 34; movement of southern icebergs, 35; glaciers south of Cape Horn, 36.</td></tr> - <tr> - <td class="tdl"><span class="pagenum" id="Page_6">6</span></td></tr> - <tr> - <td class="tdc chap" colspan="2"><a href="#CHAPTER_II">CHAPTER II</a>.</td></tr> - <tr class="bpad"> - <td class="chapsub"><span class="smcap">How ice periods in the northern hemisphere are brought about</span>,</td> - <td class="tdr"><a href="#CHAPTER_II">37–54</a></td></tr> - <tr> - <td class="tdl">Northern seas during Tertiary age, 37; Gulf Stream during Tertiary times, 38; the origin of a cold period in the northern hemisphere, 38; remarks on Gulf Stream and arctic currents, 39; circulation of arctic waters, 40; arctic channels during ice age, 41; how the weight of glaciers in the northern 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.</td></tr> - <tr> - <td class="tdc chap" colspan="2"><a href="#CHAPTER_III">CHAPTER III</a>.</td></tr> - <tr class="bpad"> - <td class="chapsub"><span class="smcap">Spread of glaciers during cold epochs</span>,</td> - <td class="tdr"><a href="#CHAPTER_III">54–61</a></td></tr> - <tr> - <td class="tdl">Spread of glaciers in tropical zone, 54; Professor Agassiz on the origin of Galapagos Islands, 55; the bowlders of Hood’s Island and rookery of Albatross, 56; alpine flora of Galapagos and tropical America, 57; Mr. J. Crawford on ancient glaciers in Nicaragua, 58; Cuba and Republic of Colombia during ice age, 58; 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.</td></tr> - <tr> - <td class="tdc chap" colspan="2"><a href="#CHAPTER_IV">CHAPTER IV</a>.</td></tr> - <tr class="bpad"> - <td class="chapsub"><span class="smcap">The glaciers of the temperate zone</span>,</td> - <td class="tdr"><a href="#CHAPTER_IV">62–75</a></td></tr> - <tr> - <td class="tdl">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,<span class="pagenum" id="Page_7">7</span> 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 Cañon, 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 Wisconsin, 74; tropical waters of North Atlantic chilled during ice age, 75; the drifted snow of British America and Siberia during ice age, 75.</td></tr> - <tr> - <td class="tdc chap" colspan="2"><a href="#CHAPTER_V">CHAPTER V</a>.</td></tr> - <tr class="bpad"> - <td class="chapsub"><span class="smcap">Remarks on theories advanced for explaining ice periods</span>,</td> - <td class="tdr"><a href="#CHAPTER_V">76–93</a></td></tr> - <tr> - <td class="tdl">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 movement of water from the northern seas at the close of glacial age, 79; why the earth-movement hypothesis should be rejected, 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 increase 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 continue 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.</td></tr> -</table> - -<hr /> - -<p><span class="pagenum" id="Page_9">9</span></p> - -<div class="chapter"> -<h2 id="CHAPTER_I" class="vspace">CHAPTER I.<br /> - -<span class="subhead">CAUSE OF COLD AND MILD PERIODS.</span></h2> -</div> - -<p><span class="firstword">It</span> is now generally conceded by those who have given the -subject much attention that the greater portion of North America -above the latitude of 39° north to the shores of the Arctic -Ocean has been furrowed and scoured by the action of ice.</p> - -<p>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.</p> - -<p>In Asia evidences of glacial action have been noticed from -Northern Siberia to the mountains of Syria.</p> - -<p>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.</p> - -<p>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.</p> - -<p>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 Zealand,<span class="pagenum" id="Page_10">10</span> -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.</p> - -<p>Kerguelen Land is pierced with deep, narrow fiords, which -have the appearance of having been the work of ancient -glaciers.</p> - -<p>The lands south of the antarctic circle are to-day supposed to -be covered by an ice-sheet, of which the great ice barrier surrounding -that region furnishes ample proof.</p> - -<p>While impressed with the above reports of the work of -ancient glaciers, in connection 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 continental -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.</p> - -<p>And it is through this grand movement of the ocean waters -that we are enabled to account for the difference in the temperature -of places now lying in the same parallels of latitude.</p> - -<p>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 succeeded -by periods of frigidity.</p> - -<p>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<span class="pagenum" id="Page_11">11</span> -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 efficient -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.</p> - -<p>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 therefrom, -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.</p> - -<p>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 depressions -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.</p> - -<p>This transfer of the ocean waters is the main cause of a temperate<span class="pagenum" id="Page_12">12</span> -climate being enjoyed by countries situated in the high -latitudes at this age.</p> - -<p>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 tropical -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.</p> - -<p>As the western continent is the only land that extends unbroken -from the equator to the cold latitudes of both hemispheres, -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 climate -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 channel, -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<span class="pagenum" id="Page_13">13</span> -northern hemisphere contained a considerable portion of the -water now swelling the southern ocean.</p> - -<p>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.</p> - -<p>Recent discoveries have proved that these high southern latitudes -have been subject to great changes of climate. According -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 latitude, -noting two active volcanoes.</p> - -<p>The same mariner brought from Seymour Island fossil -shells and coniferous wood of the Tertiary epoch.</p> - -<p>These furnish sufficient evidence to show that a warmer -climate once prevailed there.</p> - -<p>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<span class="pagenum" id="Page_14">14</span> -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 northern -seas were drained or became shallow, the augmented southern -oceans deeply submerged the region south of Cape Horn, -thus widely separating the western continent from the antarctic -lands.</p> - -<p>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 extensive -than such lands south of the equator, still, on account of -the general weakness of the south-east trade winds at the equator, -and also because of the obstructing northern lands, they -have during remote times, and at this age, been largely prevented -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.</p> - -<p>Moreover, the great currents setting southward on the western -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.</p> - -<p>The South African current is impelled northward by the -trade winds down the south-western coast of Africa; but it is<span class="pagenum" id="Page_15">15</span> -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.</p> - -<p>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 southern -movement, and, while on its way past the Azores and -Madeira Islands, is largely assisted by the prevailing winds.</p> - -<p>The Brazil current, with the impelling force of a strong -north-east monsoon during the summer season, has no obstruction -whatever in its southern passage until it meets with an offshoot -from the great drift current of the southern ocean.</p> - -<p>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 New 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. Consequently, -it turns south along the east coast of Africa into the -southern seas.</p> - -<p>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.</p> - -<p>In the North 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<span class="pagenum" id="Page_16">16</span> -weight of the land in the northern hemisphere compared with -the lands south of the equator.</p> - -<p>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.”</p> - -<p>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.”</p> - -<p>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 current -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.</p> - -<p>It is the opinion of some writers that a difference of temperature -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.</p> - -<p>Yet, whatever gravitating force it may possess for assisting -the above-named currents, it would also act against the impelling<span class="pagenum" id="Page_17">17</span> -force of the trade winds, while they were drifting the surface -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. Therefore, -while it would seem to favor the winds in their work on -the one hand, it would 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.</p> - -<p>The theory that the difference of density caused by the difference -of temperature between the polar seas and the equatorial -oceans made under-currents to flow from the polar latitudes, -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.</p> - -<p>The North Atlantic being open to the Arctic Ocean, a portion -of the Gulf Stream waters that enter it from the north-west -of Europe do sink and return southward in under-currents; -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 Atlantic; -and the same conditions probably obtain in a somewhat -less degree in the Pacific Ocean.</p> - -<p>Yet it appears that the cold waters of the Antarctic occupy -the largest space in the tropical zone, even in the North Atlantic. -Dr. Carpenter, in his lectures on Ocean Currents, speaks of<span class="pagenum" id="Page_18">18</span> -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 extend -over twenty degrees north of the equator.</p> - -<p>Thus, from what we can learn of the antarctic under-currents, -they seem to show that they are not wholly attracted northward -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.</p> - -<p>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 southward -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 augment -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 continents -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 surplus -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 temperate -latitudes. And in this way the northern oceans are -maintained at their present sea-level.</p> - -<p>The cold under-currents are probably assisted in their<span class="pagenum" id="Page_19">19</span> -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.</p> - -<p>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 oceans of the -southern hemisphere than now; for it is reported that a portion -of the low lands of Australia show traces of having been -submerged during late geological times.</p> - -<p>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 increase -of southern ice would be largely counterbalanced by the -accumulation of ice on northern lands.</p> - -<p>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.</p> - -<p>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 prevented -the oceans of the southern hemisphere from gaining -undue preponderance.</p> - -<p>Hence long geological ages passed away before the winds -were able to force more of the ocean waters southward than they<span class="pagenum" id="Page_20">20</span> -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.</p> - -<p>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.</p> - -<p>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.</p> - -<p>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. Consequently, -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.</p> - -<p>Mr. Wallace also says that “many peculiarities in the distribution -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.”</p> - -<p>And he also asserts that the great ocean basins have not -changed, and that the form of continents has been permanent.<span class="pagenum" id="Page_21">21</span> -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 continent -and the antarctic lands.</p> - -<p>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 whenever -the Cape Horn channel was widely open, and this is what -the winds are doing at this date.</p> - -<p>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<span class="pagenum" id="Page_22">22</span> -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 Mozambique -current as well as the East Australian current, and so -largely prevents their waters from warming the southern seas.</p> - -<p>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.</p> - -<p>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.</p> - -<p>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 considered -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 concurrent -in the northern and southern hemispheres. The main reasons -for such belief I will explain in the following chapter.</p> - -<p><span class="pagenum" id="Page_23">23</span> -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.</p> - -<p>For instead of the westerly winds blowing the surface waters -of the southern seas constantly around the globe, and so turning -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.</p> - -<p>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.</p> - -<p>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 latitudes, -embracing wide continents and large islands, must, during -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.</p> - -<p><span class="pagenum" id="Page_24">24</span> -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 increase -the weight of northern lands. Therefore, the waters of -the diminishing seas of the southern latitudes would be attracted -into the northern oceans in opposition to the prevailing -winds.</p> - -<p>Thus it appears that the Cape Horn channel would be too -much reduced at the perfection of an ice age to afford an independent -circulation for the southern ocean, even without -being filled by glaciers to the extent I have pointed out in previous -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.</p> - -<p>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 channel -has in past ages been obstructed.</p> - -<p>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 soundings -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.</p> - -<p>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 because -of their weight a large portion of the diminished southern<span class="pagenum" id="Page_25">25</span> -oceans would be attracted into the northern seas, it seems -that the bottom of the shoaler waters of the Cape Horn channel, -which now comprise so large a portion of its breadth, -would be raised above the surface of the sea.</p> - -<p>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 gathering -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 grounding in the shoaled waters, it seems that the -complete obstruction of the reduced channel would be accomplished.</p> - -<p>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 channel, -and the great low sea-level that would take place on its -Atlantic side.</p> - -<p>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, together -with the ponderous icebergs, blocking its waters, the -closing process would at last be speedy and effective.</p> - -<p>And on further consideration it might be said that a channel -of much less width and depth would not have been of sufficient<span class="pagenum" id="Page_26">26</span> -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 complete -and long continued to have brought such world-wide -cold periods to perfection.</p> - -<p>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 westerly -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 prevailing -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.</p> - -<p>The winds of the southern westerly wind-belt being stronger -in that region than on any other portion of the globe, consequently -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 disturbing -the ocean waters in the latitudes of the Cape Horn channel.</p> - -<p>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 <a href="#map1" class="locked">map No. 1</a>.</p> - -<p>The tropical waters thus attracted far southward would be -cooler than the tropical waters of to-day, owing to the great<span class="pagenum" id="Page_27">27</span> -amount of cold imparted to the ocean by the numerous icebergs -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 currents, -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.</p> - -<p>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 glaciers -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 diminishing -heaviness of the antarctic ice and the greater weight of -the extensive glaciers and augmented seas of the northern latitudes. -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 melting -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 hemisphere.</p> - -<p>Therefore, it seems that the Cape Horn channel would continue -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 capacity, -and again restoring the independent circulation of the -southern ocean.</p> - -<p><span class="pagenum" id="Page_28">28</span> -While contemplating the conditions that would obtain during -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 situation, -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.</p> - -<p>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 latitudes -where fresh water would congeal. Consequently, this is -one of the reasons why successive periods of frigidity and mildness -have been brought about; for with an ocean of fresh -water, repeated epochs of cold and warmth could not have occurred, -because a sea composed of fresh water would have congealed -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.</p> - -<p>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 evaporation<span class="pagenum" id="Page_29">29</span> -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 overcome -the accumulated cold of that frigid region.</p> - -<p>At this date the observant navigators who have visited the -antarctic seas report that the surface currents above the latitude -of Cape Horn, while being drifted eastward by the prevailing -westerly winds, also set toward the antarctic ice cliffs, as -shown on <a href="#map2" class="locked">map No. 2</a>.</p> - -<p>The reason why this southerly set of the surface currents becomes -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 impelling -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 temperature -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<span class="pagenum" id="Page_30">30</span> -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.</p> - -<p>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 movement -of the winds and currents encircling the antarctic continent -is shown on <a href="#map1" class="locked">map No. 1</a>.</p> - -<p>The vast, high sea-level caused by the westerly winds drifting -the surface waters against the Patagonian coast would obtain -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 antarctic -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 increased -southward flow of the equatorial waters through the -Brazil and Mozambique streams.</p> - -<p>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 northern -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<span class="pagenum" id="Page_31">31</span> -along the east coast of Africa, and, with the Cape Horn channel -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.</p> - -<p>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 attracted -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 equatorial -Atlantic and coast of Brazil. Thus it will be seen that -the Agulhas current, even with the Cape Horn channel in possession -of its present wide capacity, serves to retard somewhat -the advance of a cold period.</p> - -<p>The Agulhas current at this date also partly serves to replenish -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 removed -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 impression -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 circulation -sufficient to exclude the tropical currents from reaching -the high southern latitudes in adequate volume to maintain a -mild climate in the southern hemisphere.</p> - -<p>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<span class="pagenum" id="Page_32">32</span> -from flowing into the southern ocean in quantities sufficient to -make it impossible for glaciers to form on southern lands.</p> - -<p>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.</p> - -<p>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.</p> - -<p>The Agulhas stream, which even now assists in replenishing -the South Atlantic with tropical water, would, during the perfection -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 reason -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.</p> - -<p>Consequently, the waters of the South Atlantic Ocean would -be correspondingly reduced.</p> - -<p>Such conditions alone would greatly increase the volume of -the Agulhas stream at the culmination of a frigid age. Therefore, -the work of subduing a frigid period in the southern hemisphere -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.</p> - -<p>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.</p> - -<p><span class="pagenum" id="Page_33">33</span> -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.</p> - -<p>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 considerable -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 shallow -ocean than would occur on deeper waters. Thus the low -sea-levels of the shallow southern sea would have strong attraction -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 reduce -the temperature of the under-waters of the tropical zone.</p> - -<p>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 latitudes -than now.</p> - -<p>So, according to the conditions I have pointed out, the ice-sheets -would at length melt away, and a long period of mildness -would succeed on account of the length of time it would -require after the ice disappeared from the earth for the prevailing -winds to move the surface waters of the augmented<span class="pagenum" id="Page_34">34</span> -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 existing -at the present date, which can be seen on <a href="#map2" class="locked">map No. 2</a>, -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.</p> - -<p>Moreover, when we consider that the independent circulation -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 temperature -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.</p> - -<p>It has been proved at Point Barrow that strata of ice and -gravel can maintain a wintry temperature through the summer -months. Captain G. B. Borden, keeper of the refuge station -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 maintains -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 consequently -will conclude that the temperature of the southern -latitudes is gradually lowering.</p> - -<p><span class="pagenum" id="Page_35">35</span> -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 surface -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 Zealand. -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.</p> - -<p>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 progresses, -and the antarctic icebergs increase in size, the more -readily the cold, deep under-currents force them into the temperate -zone, in opposition to the winds and surface currents.</p> - -<p>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.</p> - -<p>The low sea-levels caused by the westerly winds to the leeward -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.</p> - -<p><span class="pagenum" id="Page_36">36</span> -The tropical currents which turn southward east of New Zealand -largely mingle their waters with the great southern -drift current, and so are carried through the Cape Horn channel. -Owing to this cause, the antarctic lands abreast Cape -Horn are less burdened with ice than other portions of the -antarctic shores.</p> - -<p>Thus, were it not for this penetration of warm waters southward, -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.</p> - -<p>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 icebergs -that float the southern temperate seas, and also the vast -movement of cold antarctic water into the temperate and tropical -oceans in deep under-currents, combined with the increasing -coldness of the westerly winds, are now slowly bringing -about in the southern hemisphere a period of frigidity.</p> - -<hr /> - -<p><span class="pagenum" id="Page_37">37</span></p> - -<div class="chapter"> -<h2 id="CHAPTER_II" class="vspace">CHAPTER II.<br /> - -<span class="subhead">HOW ICE PERIODS IN THE NORTHERN HEMISPHERE ARE -BROUGHT ABOUT.</span></h2> -</div> - -<p><span class="firstword">A large</span> 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.</p> - -<p>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 submerged, -the Baltic, Caspian, and other neighboring seas, now -land-locked, were a portion of an enlarged Atlantic. Consequently, -the westerly winds blew over a much wider North -Atlantic than during the later periods.</p> - -<p>Thus the high sea-level caused by such winds on its European -side was greater than has since been obtained with the Atlantic -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<span class="pagenum" id="Page_38">38</span> -Arctic Ocean to the low sea-level abreast Labrador and Davis -Strait.</p> - -<p>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 channel. -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 inexhaustive -they were fully able to maintain a mild climate on -the shores of the European seas, and also on the shores bordering -the Arctic Ocean, during the Tertiary epoch.</p> - -<p>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.</p> - -<p>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.</p> - -<p>This great geographical change, in connection with a cold -period progressing in the southern hemisphere, and so increasing -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<span class="pagenum" id="Page_39">39</span> -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 explanation -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 independent -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.</p> - -<p>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 Greenland, -thus surrounding that large island with an arctic temperature, -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.</p> - -<p>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<span class="pagenum" id="Page_40">40</span> -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.</p> - -<p>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.</p> - -<p>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<span class="pagenum" id="Page_41">41</span> -cold water over which the Gulf currents flow. This cold -underflow of water southward probably joins the deep antarctic -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.</p> - -<p>There are times during the late summer and early fall months -when the arctic channels are considerably obstructed by icebergs, -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.</p> - -<p>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 Newfoundland -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.</p> - -<p>Yet it is probable that an ice period extending over the<span class="pagenum" id="Page_42">42</span> -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.</p> - -<p>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 hemispheres -were concurrent; although the culmination of the -northern frigid period would be somewhat later than the perfected -southern ice age, on account of the northern seas requiring -the assistance of the cold oceans of the southern hemisphere -to perfect a northern ice age.</p> - -<p>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.</p> - -<p>On the consummation of an ice period in the northern hemisphere -heavy glaciers covered the larger portion of its continents -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.</p> - -<p>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<span class="pagenum" id="Page_43">43</span> -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.</p> - -<p>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.</p> - -<p>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.</p> - -<p>An article in <cite>Science</cite>, July 5, 1895, written by Agnes Crane, -states that Professor Joseph Prestwich has recently contributed -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 observation, -of the submergence of the south of England not less -than a thousand feet, at the close of the glacial epoch.</p> - -<p>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 geographical -conditions of to-day which favor the return of another -ice age.</p> - -<p>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 impression -is that the southern portion of the Gulf Stream<span class="pagenum" id="Page_44">44</span> -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 during -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 impelled -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 <a href="#map2" class="locked">map No. 2</a>.</p> - -<p>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 Atlantic -do not flow peacefully along through the West India passages -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 tropical -high sea-level are attracted to the low ocean-level of the -Western North Atlantic.</p> - -<p>Thus it seems that the great fountain-head of the Gulf -Stream is situated between the wide tide-rips and the Caribbean -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 eastern -portion of the Gulf currents after they enter the Atlantic.<span class="pagenum" id="Page_45">45</span> -Still, the great high sea-level which presses against the Windward -Islands, being somewhat higher than the Caribbean Sea, -forces its waters through the island passages in quantities sufficient -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 numerous -channels are subject to fluctuations, and so also is the Gulf -Stream which they supply.</p> - -<p>That portion of the high sea-level south of Guadeloupe receives -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 equatorial -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.</p> - -<p>The south-east trades which blow over the Eastern and Middle -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 directly -toward the calm belt, and so raise its waters above the -common level of the sea.</p> - -<p>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, on 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 extends -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.</p> - -<p><span class="pagenum" id="Page_46">46</span> -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.</p> - -<p>It does not appear that the seas of the high northern latitudes -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 southern -coast of Brazil, the westerly currents setting past the Amazon -River are reversed, and set to the south-east, while such -conditions last.</p> - -<p>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<span class="pagenum" id="Page_47">47</span> -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.</p> - -<p>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 current. -But, whenever the Cape Horn channel is closed or much -obstructed, so causing a great low sea-level in the Southern Atlantic, -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.</p> - -<p>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<span class="pagenum" id="Page_48">48</span> -into the Caribbean Sea through the passages south of Guadeloupe, -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.</p> - -<p>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 gathering, -where the most dense collection of weeds is found, is -situated near the tropic of Cancer, and about 55° west longitude, -as shown on <a href="#map2" class="locked">map No. 2</a>.</p> - -<p>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 currented -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 considerable -time, but at length lose their renovating properties, and -in certain areas of the sea acquire an appearance of age and -decay.</p> - -<p>The Gulf Stream, and such other tropical waters as are attracted -northward to the low sea-level abreast the North American -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.</p> - -<p>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<span class="pagenum" id="Page_49">49</span> -vast sea of weeds has always been placed on the charts several -degrees of longitude east of its true position.</p> - -<p>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 become -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 obtained -have all been laid before the public. Still, such surveys -cover but a portion of the whole round of the vast movement -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.</p> - -<p>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 between -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.</p> - -<p>The unmistakable traces of cold periods having occurred in<span class="pagenum" id="Page_50">50</span> -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.</p> - -<p>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 equatorial -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. Furthermore, -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 replenished -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<span class="pagenum" id="Page_51">51</span> -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.</p> - -<p>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 Humboldt -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 equatorial -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.</p> - -<p>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.</p> - -<p>From what has been explained, it will be seen that the<span class="pagenum" id="Page_52">52</span> -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.</p> - -<p>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 sufficient -to prevent ice from gathering on lands within the antarctic -circle. This increasing storage of ice is only another -name for the accumulation and spreading of cold, and so the -increasing chillness 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.</p> - -<p>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 surface -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 independent -circulation of the southern ocean is maintained.</p> - -<p><span class="pagenum" id="Page_53">53</span> -But at length the depth of the great southern ocean is diminished -because of the water evaporated from its surface, and -precipitated in the shape of hail and snow over the vast continents -and islands of the high northern latitudes, thus adding -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.</p> - -<p>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 necessarily -creates a great low sea-level on the Atlantic side of the obstructed -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.</p> - -<p>It will thus be seen that the conditions for the circulation of -the tropical ocean waters have met with a great change.</p> - -<p>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 diminished. -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 explained -in the preceding pages.</p> - -<p>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<span class="pagenum" id="Page_54">54</span> -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 southern -seas had moved into the northern hemisphere. Consequently, -the antarctic lands were raised higher above the sea-level -than at this age. Hence the area of lofty land was increased -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.</p> - -<hr /> -<div class="chapter"> -<h2 id="CHAPTER_III" class="vspace">CHAPTER III.<br /> - -<span class="subhead">THE SPREAD OF GLACIERS DURING COLD EPOCHS.</span></h2> -</div> - -<p><span class="firstword">I have</span> 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 defined -to be attributed to any process of weathering, while Alpine -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.</p> - -<p>This fact goes to show that a portion of the lowlands of the -tropical zone have experienced a temperature favorable for the<span class="pagenum" id="Page_55">55</span> -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 appearance -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.</p> - -<p>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.</p> - -<p>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 impression -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.</p> - -<p>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 débris, 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<span class="pagenum" id="Page_56">56</span> -smaller than those at the foot of the mountain, as none of the -former were more than three or four feet in their longest measurement.</p> - -<p>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.</p> - -<p>The plain so thickly strewn with bowlders, and partly -shaded by a tall growth of shrubs, fell off abruptly at the seaside, -forming a steep cliff some two hundred feet in height.</p> - -<p>The rocky floor at the foot of the cliff received such débris as -fell from the sea-washed land; yet it contained few bowlders, -they having been washed away by the waves soon after falling.</p> - -<p>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 débris 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.</p> - -<p>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 possessed -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 favorable -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.</p> - -<p><span class="pagenum" id="Page_57">57</span> -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.</p> - -<p>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 northern -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.</p> - -<p>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 animals, -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 <a href="#map1" class="locked">map No. 1</a>.</p> - -<p><span class="pagenum" id="Page_58">58</span> -In <cite>Science</cite>, Nov. 17, 1893, Mr. J. Crawford published a summary -of his discoveries in Nicaragua, during ten months of -nearly continuous exploration since August, 1892.</p> - -<p>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 tropical -America were glaciated at the same time, especially in -regions of great precipitation.</p> - -<p>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 keeping -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.<a id="FNanchor_1" href="#Footnote_1" class="fnanchor">*</a> 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 possessing<span class="pagenum" id="Page_59">59</span> -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 current -being separated by continental lands from the great equatorial -stream of the Pacific and Indian Oceans.</p> - -<div class="footnote"> - -<p><a id="Footnote_1" href="#FNanchor_1" class="nodec">*</a>The meeting of the British Association for the Advancement of -Science, September, 1895, was reported in <cite>Science</cite> 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.</p></div> - -<p>Therefore, the tropical Atlantic waters must have been reduced -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 current -of the latter oceans, during its western movement, was exposed -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.</p> - -<p>The high lands of tropical Africa, above the altitude of -three thousand feet, and situated in places of great precipitation, -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.<span class="pagenum" id="Page_60">60</span> -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 and -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.”</p> - -<p>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.</p> - -<p>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 during -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;<span class="pagenum" id="Page_61">61</span> -for, since the seas and lands of the globe were chilled, the conditions -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 temperature -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.</p> - -<p>And, when we reflect how the heat of the sun’s rays was -conserved by the ocean waters, and that their circulation during -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.</p> - -<p>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.</p> - -<p>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<span class="pagenum" id="Page_62">62</span> -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.</p> - -<p>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.</p> - -<p>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.</p> - -<hr /> -<div class="chapter"> -<h2 id="CHAPTER_IV" class="vspace">CHAPTER IV.<br /> - -<span class="subhead">THE GLACIERS OF THE TEMPERATE ZONES.</span></h2> -</div> - -<p><span class="firstword">Having</span> 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 geological -agent, while others assert that during the glacial epoch -heavy ice-sheets covered the elevated portions of Western<span class="pagenum" id="Page_63">63</span> -North America as far south as the thirty-sixth parallel of latitude, -and Eastern North America was overspread with ice-sheets, -which attained a depth of five or six thousand feet, and -were able to move their débris 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.</p> - -<p>But it is now said that this implied magnitude of the glacial -deposits on the lands skirting the New England coast is without -foundation, since the larger bulk of these islands consists -of upturned Cretaceous and Tertiary strata, which are only -thinly covered with glacial débris, 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 Vineyard -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 shallow -sea, and forced them southward in a disturbed condition to -the position which they now occupy.</p> - -<p>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 sufficient -to show that large quantities of such débris were carried -over the islands into the Atlantic. And, judging from the -eroded rocky New England lands, there must have been sufficient -glacial drift moved over Nantucket and Martha’s Vineyard -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.</p> - -<p>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<span class="pagenum" id="Page_64">64</span> -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.</p> - -<p>Professor James Geikie states, in his discussion on the glacial -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 extends -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.</p> - -<p>Such blocks are found on the Jura, at a height of no less than -two thousand feet above the Lake of Neuchâtel. The Jura -Mountains being formed of limestone, it is easy to distinguish -the débris 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 existence -becomes almost necessary to represent the general outlines -of disturbance performed during an ice period. In consideration -of such facts and the foregoing statements of reliable observers, -I am prompted to offer my views on glacial work performed -on a portion of the Pacific shores of North America, -which seems to me to be much more extensive than hitherto -supposed.</p> - -<p>Professor Whitney describes the coast mountains of California -as being made up of great disturbances, which have been -brought about within geologically recent times; and this statement -I found to be so obvious in my travels over that region -that it appears to me that the coast ranges originated in a different<span class="pagenum" id="Page_65">65</span> -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 position -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.</p> - -<p>But it seemed to me that such deposits could not be found in -the foot-hills of the Sierras, which contain the moraine of inferior -ice-sheets that terminated at the base of the mountains.</p> - -<p>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 débris 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.</p> - -<p>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 differ -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 incline, -pressed and ploughed below the somewhat superficial cretaceous -and alluvial strata which lay in their course. The disturbed -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 Sierras -on account of the coast ranges not having a rocky core of -sufficient firmness to give shape to such bowlders. Moreover,<span class="pagenum" id="Page_66">66</span> -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.</p> - -<p>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 concealed.</p> - -<p>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 gathering -immense accumulations in their front, sufficient to form -the coast hills, the débris thus amassed being able to arrest the -further movement of the ice seaward.</p> - -<p>The coast ranges in several places have been subject to igneous -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 sufficient -to cause outbursts of lava, where the nature of the material -favored combustion. The low plains, lakes, and bays -which separate the Sierras from the coast hills are in a position -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 appears -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.</p> - -<p>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<span class="pagenum" id="Page_67">67</span> -over New England. Writers who have given the subject considerable -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 accumulations -of débris 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 débris -that should accumulate from the erosion of the deep valleys.</p> - -<p>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 Central -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.</p> - -<p>Therefore, what must have been the depth of ice over the -high lands of the Pacific coast north of California at the culmination -of a frigid period? The descriptions given by Dr.<span class="pagenum" id="Page_68">68</span> -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.</p> - -<p>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 southward -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 temperature -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.</p> - -<p>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. Professor -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 whatever -movement it may have had, must have found its main -outlet through the Grand Canyon of the Colorado.</p> - -<p>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.</p> - -<p>According to Professor Geikie’s observations the Second -Colorado Canyon was filled with glaciers during the ice age.<span class="pagenum" id="Page_69">69</span> -Therefore, it seems that these glaciers must have flowed down -into the Grand Canyon, and there united with glaciers flowing -from more northern regions.</p> - -<p>An account of a collecting expedition to Lower California -by G. Eison, in 1895, describes ancient moraines at the extremity -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 favorable -for the great glacier of the Colorado Canyon to have -flowed into the Gulf of California.</p> - -<p>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 considerable -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.</p> - -<p>The conglomerate deposits in the Appalachian district of -North America are known as occurring on a large scale. Professor -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 Eastern -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.</p> - -<p>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?</p> - -<p><span class="pagenum" id="Page_70">70</span> -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 débris is plainly -traced. Still, it appears to me that a line of bowlders deposited -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.</p> - -<p>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 permit; -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. Therefore, -on such lines the bowlders would be released, while the -ice-sheet would still move on, although largely deprived of its -eroding power.</p> - -<p>This is the probable reason why a line of glacial débris, -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 débris, because there could be no sudden change of temperature -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<span class="pagenum" id="Page_71">71</span> -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.</p> - -<p>Should we place the glacial boundary on the line of the rocky -débris, 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.</p> - -<p>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.</p> - -<p>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 receding -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<span class="pagenum" id="Page_72">72</span> -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 weathering, -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.</p> - -<p>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 basins 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.</p> - -<p>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<span class="pagenum" id="Page_73">73</span> -marine strata to give way in the weaker places under its -burden. The sinks thus formed, probably of frequent occurrence -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.</p> - -<p>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.</p> - -<p>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.</p> - -<p>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<span class="pagenum" id="Page_74">74</span> -account for the numerous ore-bearing faulting fissures traversing -the limestone strata.</p> - -<p>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 whatever -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 limestone -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.</p> - -<p>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.</p> - -<p>Therefore, the snow and ice which gathered on the driftless -region had little movement in any direction, while the temperature -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<span class="pagenum" id="Page_75">75</span> -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.</p> - -<p>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 Nicaragua.</p> - -<p>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 latitudes. -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.</p> - -<p>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 débris from such -erosion was deposited in the arctic seas.</p> - -<hr /> - -<p><span class="pagenum" id="Page_76">76</span></p> - -<div class="chapter"> -<h2 id="CHAPTER_V" class="vspace">CHAPTER V.<br /> - -<span class="subhead">REMARKS ON THEORIES ADVANCED FOR EXPLAINING ICE -PERIODS.</span></h2> -</div> - -<p><span class="firstword">On</span> Nov. 12, 1891, Professor Geikie made his presidential -address before the Edinburgh Geological Society, the subject -being “Supposed Causes of the Glacial Period.”</p> - -<p>Many of his views advanced in this lecture were so much in -accordance with my own that I am induced to repeat them. -He said 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 satisfactory. -And, while examining the earth-movement hypothesis, -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.</p> - -<p>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.</p> - -<p>Another objection to the earth-movement hypothesis was -this: it did not account for interglacial conditions. The advocates -of that hypothesis imagined that these conditions would -supervene when the highly elevated northern regions were depressed -to their present level. But these were the conditions<span class="pagenum" id="Page_77">77</span> -that obtained at the present time; and yet in spite of them the -climate was neither so equable nor so genial as that which obtained -in interglacial times and during the mild stage of the -necessary post-glacial period.</p> - -<p>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.</p> - -<p>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.</p> - -<p>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 northern -hemisphere; for without such assistance they would be -unable to disperse the vast ice-sheets of the northern latitudes.</p> - -<p>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 northern -latitudes surpassed the growth and weight of the glaciers -on the smaller lands of the southern hemisphere.</p> - -<p>Hence the attraction of the ocean waters northward overcomes -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 increased -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<span class="pagenum" id="Page_78">78</span> -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.</p> - -<p>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.</p> - -<p>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.</p> - -<p>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.</p> - -<p>But I will say in addition that, on further consideration, it<span class="pagenum" id="Page_79">79</span> -seems that one of the main causes of the waters of the augmented -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 causing -the extinction of the vast low sea-level that furnished such -great attraction for the waters of the more northern latitudes.</p> - -<p>If the earth-movement hypothesis, so wholly rejected by Professor -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.</p> - -<p>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 eastern -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.</p> - -<p>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.</p> - -<p>Therefore, it is not necessary that lands pierced by deep<span class="pagenum" id="Page_80">80</span> -fiords should have acquired a higher level during the ice age -than they now maintain. And it is probable that on the antarctic -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.</p> - -<p>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.</p> - -<p>There are deposits of ice on the North American coast bordering -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.</p> - -<p>Yet it is said that such is not always the case. This is probably -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,<span class="pagenum" id="Page_81">81</span> -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.</p> - -<p>As to the Alpine glaciers, M. Forel reports from data he has -collected that there have been several enlargements and diminutions -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 during -cold and rainy seasons. The glaciers of Alaska cannot attain -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 considerable -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.</p> - -<p>This great ocean stream in its impact against the shores of -Oregon causes a high sea-level, which is mostly turned southward -by the prevailing north-west winds. Still, a comparatively -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.</p> - -<p><span class="pagenum" id="Page_82">82</span> -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.</p> - -<p>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.</p> - -<p>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 enlargement -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<span class="pagenum" id="Page_83">83</span> -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.</p> - -<p>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.</p> - -<p>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 Australian -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.</p> - -<p>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 hemisphere.</p> - -<p>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 requires -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 in Flanders or Brittany; and vineyards -are no longer planted on the elevated shores of France where<span class="pagenum" id="Page_84">84</span> -they flourished three hundred years ago. Arago did not refuse -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.</p> - -<p>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 generation -it has been very profitable.</p> - -<p>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 correspondent -of the <cite>Spectator</cite>, 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 resentment -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.”</p> - -<p>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.</p> - -<p>A writer in the North China <cite>Herald</cite>, 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.</p> - -<p>“It is also said that the ferocious alligator, that formerly infested -the rivers of South China, has retreated southward.</p> - -<p>“The flora of the country is also affected by the increasing -coldness of the climate. The bamboo is not found in the forests<span class="pagenum" id="Page_85">85</span> -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.”</p> - -<p>A letter from Hong Kong, published in the London <cite>Standard</cite>, -reports that on the 15th of January, 1893, the temperature -of Hong Kong, a tropical seaport of China, was below freezing -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° Fahrenheit.</p> - -<p>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.</p> - -<p>Observations made by Boussingault at Quito in 1831, compared -with those from 1878 to 1881, showed a decrease from -15.2° Centigrade to 13.27° Centigrade.</p> - -<p>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.</p> - -<p>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 obstructed -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 sufficiently -in a few seasons to clear the obstructed channels, and -also somewhat soften for several successive years the temperature -of such lands as border on the seas of that region.</p> - -<p>And in this way we account for the mild seasons which at<span class="pagenum" id="Page_86">86</span> -times follow those of lower temperature in high northern latitudes.</p> - -<p>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 overcome -the warmth gained during the temporary detention of ice -in the northern seas. Thus, under such considerations, it appears -that the conditions are favorable for the growth of glaciers -in the high northern latitudes.</p> - -<p>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.</p> - -<p>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 preceding -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.</p> - -<p>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 glaciers -and icebergs; and meanwhile the same conditions may -have governed the arctic channels which give an independent<span class="pagenum" id="Page_87">87</span> -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.</p> - -<p>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 channel -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.</p> - -<p>The statements made by General Cowell in <cite>Science</cite> of Nov. 25, -1892, in reference to the alleged discovery of the second rotation -of the earth by Major-general Drayson, represents the discovery -as affording a new solution for the cause or causes of an -ice age.</p> - -<p>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 -<span class="smcap smaller">B.C.</span>, “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<span class="pagenum" id="Page_88">88</span> -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 <span class="smcap smaller">A.D.</span>; 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 <span class="smcap smaller">A.D.</span>, 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 temperate -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 prevail -the same as now.</p> - -<p>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 process -for moving tropical water into the high latitudes, or excluding -it therefrom, would not be greatly changed.</p> - -<p>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 contrary, -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 vertical -sun in midsummer as far south as river Plate, thus forcing -the surface waters of the tropical oceans into the higher latitudes -with greater facility than at this age.</p> - -<p>Moreover, according to the statements of General Cowell, the<span class="pagenum" id="Page_89">89</span> -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.</p> - -<p>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 continents, -moved the surface waters of the ocean from torrid latitudes -to colder zones, and from the colder zones to the warmer -latitudes.</p> - -<p>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 southern -sufficient to submerge the low lands of the southern hemisphere, -causing a great diversion of the tropical currents from -the high southern latitudes, such as I have pointed out in preceding -chapters.</p> - -<p>Those writers who believe that ocean currents have been the -cause of great climatic changes have suggested that the existence -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.</p> - -<p><span class="pagenum" id="Page_90">90</span> -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.</p> - -<p>Yet it may be said that an open channel through Central -America would have connected two high sea-levels.</p> - -<p>For this reason there would be little or no exchange of water -between the Caribbean Sea and the Pacific Ocean.</p> - -<p>The high sea-level on the Pacific side is caused by the prevailing -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.</p> - -<p>Consequently, the Atlantic waters would not run into the -Pacific Ocean, even if a channel opened through Central -America.</p> - -<p>Therefore, the Gulf Stream has never been turned away -from the North Atlantic.</p> - -<p>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 Europe -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.</p> - -<p>Besides, we should consider that there is a continuous range<span class="pagenum" id="Page_91">91</span> -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 tropical -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 Mozambique -and Agulhas currents in the manner I have previously -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.</p> - -<p>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 extensive -as the surface of the globe; and, therefore, any geographical -change that would affect only a comparatively small portion -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.</p> - -<p>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 conveyed -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.</p> - -<p>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 latitudes.</p> - -<p><span class="pagenum" id="Page_92">92</span> -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.</p> - -<p>Therefore, the increase of glaciers and icebergs will slowly -continue until a glacial epoch is perfected.</p> - -<p>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 constantly -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 -realise 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 comparatively -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 increasing -cold will in a few thousand years drive the greater<span class="pagenum" id="Page_93">93</span> -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.</p> - -<p>And, from what can be learned from the relics of man’s prehistoric -life, it seems to point to the lands of the tropical latitudes -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 extensive -than at this age, on account of the shrinkage of the sea, -because of the great amount of water evaporated from its surface, -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 mountain -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.</p> - -<p>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 maintain,<span class="pagenum" id="Page_94">94</span> -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 tropical portions 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.</p> - -<div class="chapter"><div class="transnote"> -<h2 id="Transcribers_Notes" class="nobreak p1">Transcriber’s Notes</h2> - -<p>Punctuation, hyphenation, and spelling were made -consistent when a predominant preference was found -in the original book; otherwise they were not changed.</p> - -<p>Simple typographical errors were corrected; unbalanced -quotation marks were remedied when the change was -obvious, and otherwise left unbalanced.</p> -</div></div> - - - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of The Coming Ice Age, by C. A. M. 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