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