वेदों की प्राचीनता एवं काल-निर्णय / ओरायन (लोकमान्य बाल गंगाधर तिलक - खगोलीय वैदिक शोध)

PREHISTORIC TIMES. 13
But these estimates are not better than mere approximations,
and generally speaking we may take the Neolithic age in Europe
as commencing not later than 5000 B. C.
But when we pass from the Neolithic to the Palæolithic
period the difficulty of ascertaining the commencement of the
latter becomes still greater. In fact we have here to ascertain
the time when the Post-Glacial period commenced. The
Palæolithic man must have occupied parts of Western Europe
shortly after the disappearance of the Ice Age and Prof. Geikie
considers that there are reasons for supposing that he was inter-
glacial. The Glacial period was characterised by geographical
and climatic changes on an extensive scale. These changes and
the theories regarding the cause or the causes of the Ice Age will
be briefly stated in the next chapter. We are here concerned
with the date of the commencement of the Post-Glacial period,
and there are two different views entertained by geologists on the
subject. European geologists think that as the beginning of the
Post-Glacial period was marked with great movements of eleva-
tion and depression of land, and as these movements take place
very slowly, the commencement of the Post-Glacial period cannot
be placed later than 50 or 60 thousand years ago. Many American
geologists, on the other hand, are of opinion that the close of the
last Glacial period must have taken place at a much more recent
date. They draw this inference from the various estimates of time
required for the erosion of valleys and accumulation of alluvial
deposits since the last Glacial period. Thus according to Gilbert,
the post-glacial gore of Niagara at the present rate of erosion
must have been excavated within 7000 years ¹. Other American
geologists from similar observations at various other places have
arrived at the conclusion that not more than about 8000 years have

1. See Geikie's Fragments of Earth Lore, p. 286; also Dr. Bonney's.
   Story of our Planet, p. 560.

14 . THE ARCTIC HOME IN THE VEDAS.
elapsed since the close of the last Glacial period. This estimate
agrees very well with the approximate date of the Neolithic
period ascertained from the amount of silt in some of the
lakes in Switzerland. But it differs materially from the
estimate of the European geologists. It is difficult to decide,
in the present state of our knowledge, which of these
estimates is correct. Probably the Glacial and the Post-Glacial
period may not, owing to local causes, have commenced or ended
at one and the same time in different places, just as the ages of
Stone and Bronze were not synchronous in different countries.
Prof. Geikie does not accept the American estimate on the
ground that it is inconsistent with the high antiquity of the
Egyptian civilisation, as ascertained by recent researches. But
if no traces of glaciation are yet found in Africa this objection
loses its force, while the arguments by which the American view
is supported remain uncontradicted.
There are other reasons which go to support the same view.
All the evidence regarding the existence of the Glacial period
comes form the North of Europe and America; but no traces of
glaciation have been yet discovered in the Northern Asia or North
Alaska. It is not to be supposed, however, that the northern
part of Asia did not enjoy a genial climate in early times. As
observed by Prof. Geikie "everywhere throughout this vast
region alluvial deposits are found packed up with the remains of
mammoth, woolly rhinoceros, bison, and horse;" and "the fossils
are usually so well preserved that on one occasion the actual
carcass of a mammoth was exposed in so fresh a state that dogs
ate the flesh thereof." * These and other equally indisputable
facts clearly indicate the existence in Siberia of a mild and genial
climate at a time, which, from the freshness of the fossil remains,
cannot be supposed to be removed from the present by several
*. See Geikie's Great Ice Age, 1st Ed., p. 495; Dr. Croll's Climate
and Cosmology, p. 179.

PREHISTORIC TIMES. 15
thousands of years. Again in North Africa and Syria we find in
dry regions wide-spread fluviatile accumulations which are believ-
ved to be indications of rainy seasons, contemporaneous with the
Glacial period of Europe.* If this contemporaneity can be
established, the high estimate of time for the commencement of
the Post-Glacial period in Europe will have to be given up, or at
any rate much curtailed.
As regards the races which inhabited Europe in these early
ages, the evidence furnished by human remains or skulls shows
that they were the direct ancestors of the races now living in the
different parts of Europe. The current classification of the human
races into Aryan, Semetic, Mongolian, &c. is based upon the
linguistic principle; but it is evident that in dealing with ancient
races the archæologist and the geologist cannot adopt this princi-
ple of division, inasmuch as their evidence consists of relics from
which no inference can be drawn as to the language used by the
ancient man. The shape and the size of the skull have, therefore,
been taken as the chief distinguishing marks to classify the
different races of prehistoric times. Thus if the extreme breadth
of a skull is three-fourths, or 75 per cent., of its length or lower, it
is classed as long-headed or dolicho-cephalic, while if the breadth
is higher than 83 per cent. of the length, the skull is said to be
brachy-cephalic or broad-headed; the intermediate class being
styled ortho-cephalic, or sub-dolicho-cephalic, or sub-brachy-
cephalic according as it approaches one or the other of these
types. Now from the examination of the different skulls found in
the Neolithic beds it has been ascertained that Europe in those
early days was inhabited by four different races, and that the existing
European types are directly descended from them. Of these four
races two were dolicho-cephalic, one tall and one short; and two
brachy-cephalic similarly divided. But the Aryan languages are,

• See Geikie's Fragments of Earth Lore, p. 252.

16 'THE ARCTIC HOME IN THE VEDAS.
at present, spoken in Europe by races exhibiting the charac-
teristics of all these types. It is, however, evident that one
alone of these four ancient races can be the real representative
of the Aryan race, though there is a strong difference of
opinion as to which of them represented the primitive Aryans.
German writers, like Posche and Penka, claim that the tall
dolicho-cephalic race, the ancestors of the present Germans, were
the true representative Aryans; while French writers, like Chavee
and M. de Mortillet, maintain that the primitive Aryans were
brachy-cephalic and the true Aryan type is represented by the Gauls.
Canon Taylor in his 'Origin of the Aryans sums up the controversy
by observing that when two races come in contact, the probability
is that the speech of the most cultured will prevail, and therefore
“it is" he says “an easier hypothesis to suppose that the dolicho-
cephalic savages of the Baltic coast acquired Aryan speech from
their brachy-cephalic neighbours, the Lithuanians, than to suppose,
with Penka, that they succeeded in some remote age in Aryanis-
ing the Hindus, the Romans and the Greeks.”*
Another method of determining which of these four races
represented the primitive Aryans in Europe is to compare the
grades of civilisation attained by the undivided Aryans, as
ascertained from linguistic palæontology, with those attained by
the Neolithic races as disclosed by the remains found in their
dwellings. As for the Palæolithic man his social condition appears
to have been far below that of the undivided Aryans; and Dr.
Schrader considers it as indubitably either non-Indo-European or
pre-Indo-European in character. The Palæolithic man used stone
hatchets and bone needles, and had attained some proficiency in
the art of sculpture and drawing, as exhibited by outlines of various
animals carved on bones &c.; but he was clearly unacquainted

• See Taylor's Origin of the Aryans, p. 243.

PREHISTORIC TIMES. . 17
with the potter's art and the use of metals. It is only in the
Neolithic period that we meet with pottery in the piled villages
of lake-dwellers in Switzerland. But even the oldest lake-dwellers
seem to have been unacquainted with the use of metals and
waggons, both of which were familiar to the undivided Aryans.
No trace of woollen cloth is again found in these lake-dwellings,
even when sheep had become numerous in the Bronze age. But with
these exceptions the culture of the Swiss lake-dwellings is con-
sidered by Dr. Schrader to be practically of the same character
as the culture common to the European members of the Indo-
Germanic family, and he, therefore, ventures to suggest, though
cautiously, that "from this point of view there is nothing to
prevent our assuming that the most ancient inhabitants of Switzer-
land were a branch of the European division" of the Aryan race.*
But though recent discoveries have brought to light these
facts about the human races inhabiting Europe in prehistoric
times, and though we may, in accordance with them, assume
that one of the four early Neolithic races represented the primitive
Aryans in Europe, the question whether the latter were autochth-
onous, or went there from some other place and then succeeded
in Aryanising the European races by their superior culture and
civilisation, cannot be regarded as settled by these discoveries.
The date assigned to the Neolithic period as represented by Swiss
lake-dwellers is not later than 5000 B. C., a time when Asiatic
Aryans were probably settled on the Jaxartes; and it is admitted
that the primitive Aryans in Europe could not have been the de-
scendants of the Palæolithic man. It follows, therefore, that
if we discover them in Europe in the early Neolithic times
they must have gone there from some other part of the
*Dr. Schrader's Prehistoric Antiquities of the Aryan Peoples,
translated by Jevons, Part IV. Ch. xi. p. 368.

18 . THE ARCTIC HOME IN THE VEDAS.
globe. The only other alternative is to assume that one of the
four Neolithic races in Europe developed a civilisation quite
independently of their neighbours, an assumption, which is impro-
bable on its face. Although, therefore, we may, in the light of
recent scientific discoveries, give up the theory of successive
migrations into Europe from a common home of the Aryan race
in Central Asia in early times, yet the question of the primeval
home of the Aryan race, a question with which we are mainly
concerned in this book, still remains unsolved. When and where
the primitive Aryan tongue was developed is again another
difficult question which is not satisfactorily answered. Canon
Taylor, after comparing the Aryan and Ural-Altaic languages,
hazards a conjecture that at the close of the reindeer, or the last
period of the Palæolithic age, a Finnic people appeared in
Western Europe, whose speech remaining stationary is represent-
ed by the agglutinative Basque, and that much later, at the be-
ginning of the pastoral age, when the ox had been tamed, a taller
and more powerful Finno-Ugric people developed in Central
Europe the inflexive Aryan speech.* But this is merely a
conjecture, and it does not answer the question how the Indo-
Iranians with their civilisation are found settled in Asia at a time
when Europe was in the Neolithic age. The Finnic language
again discloses a number of culture words borrowed from the
Aryans, and it is unlikely that the language of the latter could
have got its inflection from the Finnic language. A mere similarity
of inflectional structure is no evidence whatsoever for deciding
who borrowed from whom, and it is surprising that the above
suggestion should come from scholars, who have assailed the
theory of successive Aryan migrations from a common Asiatic
home, a theory which, amongst others, was based on linguistic
grounds. Why did the Finns twice migrate from their home is also

• The Origin of the Aryans, p. 296.

PREHISTORIC TIMES. 19
left unexplained. For reasons like these it seems to me more
probable that the Finns might have borrowed the culture words
from the Aryans when they came in contact with them, and that
the Aryans were autochthonous neither in Europe nor in Central
Asia, but had their original home somewhere near the North
Pole in the Palæolithic times, and that they migrated from this
place southwards in Asia and Europe, not by any 'irresistible
impulse,' but by unwelcome changes in the climatic conditions of
their original home. The Avesta preserves traditions which fully
support this view. But these have been treated as valueless by
scholars, who worked up their theories at a time when man was
regarded as post-glacial, and the Avestic traditions were, it was
believed, not supported by any Vedic authority. But with the
time-telescope of a wider range supplied to us by recent scientific
discoveries it has become possible to demonstrate that the Avestic
traditions represent a real historical fact and that they are fully
supported by the testimony of the Vedas. The North Pole is
already considered by several eminent scientific men as the most
likely place where plant and animal life first originated; and I
believe it can be satisfactorily shown that there is enough positive
evidence in the most ancient books of the Aryan race, the Vedas
and the Avesta, to prove that the oldest home of the Aryan people
was somewhere in regions round about the North Pole. I shall
take up this evidence after examining the climatic conditions of
the Pleistocene or the Glacial period and the astronomical
characteristics of the Arctic regions in the next two chapters,

CHAPTER II.
THE GLACIAL PERIOD.
Geological climate—Uniform and gentle in early ages—Due to
different distribution of land and water—Climatic changes in the
Quaternary era—The Glacial epoch—Its existence undoubtedly
proved—Extent of glaciation—At least two Glacial periods—
Accompanied by elevation and depression of land—Mild and
genial Inter-glacial climate even in the Arctic regions—Various
theories regarding the cause of the Ice Age stated—Lyell's theory
of geographical changes—Showing long duration of the Glacial
period—Croll's theory—Effect of the precession of the equinoxes
on the duration and intensity of seasons—The cycle of 21,000
years—The effect enhanced by the eccentricity of the earth's
orbit—Maximum difference of 33 days between the duration of
summer and winter—Sir Robert Ball's calculations regarding
the average heat received by each hemisphere in summer and
winter—Short and warm summers and long and cold winters,
giving rise to a Glacial epoch—Dr. Croll's extraordinary
estimate regarding the duration of the Glacial epoch—Based
on the maximum value of the eccentricity of the earth's orbit
—Questioned by astronomers and geologists—Sir Robert Ball's
and Newcomb's view—Croll's estimates inconsistent with
geological evidence—Opinions of Prof. Geikie and Mr. Hudleston
—Long duration of the Glacial period—Summary of results.
THE climate of our globe at the present day is characterised by
a succession of seasons, spring, summer, autumn, and winter, caused
by the inclination of the earth's axis to the plane of the ecliptic.
When the North Pole of the earth is turned away from the sun in
its annual course round that luminary, we have winter in the
northern and summer in the southern hemisphere, and vice versa
when the North Pole is turned towards the sun. The cause of the
rotation of seasons in the different hemispheres is thus very simple,
and from the permanence of this cause one may be led to think

THE GLACIAL PERIOD. 21
that in the distant geological ages the climate of our planet
must have been characterised by similar rotations of hot and
cold seasons. But such a supposition is directly contradicted by
geological evidence. The inclination of the earth's axis to the
plane of the ecliptic, or what is technically called the obliquity of
the ecliptic, is not the sole cause of climatic variations on the
surface of the globe. High altitude and the existence of oceanic
and aerial currents, carrying and diffusing the heat of the equatorial
region to the other parts of the globe, have been found to produce
different climates in countries having the same latitude. The
Gulf Stream is a notable instance of such oceanic currents, and
had it not been for this stream the climate in the North-West of
Europe would have been quite different from what it is at present.
Again, if the masses of land and water be differently distributed
from what they are at present, there is every reason to suppose
that different climatic conditions will prevail on the surface of the
globe from those which we now experience, as such a distribution
would materially alter the course of oceanic and aerial currents
going from the equator to the Poles. Therefore, in the early
geological ages, when the Alps were low and the Himalayas not
yet upheaved, and when Asia and Africa were represented only
by a group of islands, we need not be surprised if, from geological
evidence of fossil fauna and flora, we find that an equable and
uniform climate prevailed over the whole surface of the globe as
the result of these geographical conditions. In Mesozoic and
Cainozoic times this state of things appears to have gradually
changed. But though the climate in the Secondary and the
Tertiary era was not probably as remarkably uniform as in the
Primary, yet there is clear geological evidence to show
that until the close of the Pliocene period in the Tertiary
era the climate was not yet differentiated into zones and there
were then no hot and cold extremes as at present. The close

22 THE ARCTIC HOME IN THE VEDAS.
of the Pliocene and the whole of the Pleistocene period was
marked by violent changes of climate bringing on what is called
the Glacial and Inter-Glacial epochs. But it is now conclusively
established that before the advent of this period a luxuriant forest
vegetation, which can only grow and exist at present in the
tropical or temperate climate, flourished in the high latitude of
Spitzbergen, where the sun goes below the horizon from Novem-
ber till March, thus showing that a warm climate prevailed in
the Arctic regions in those days.
It was in the Quaternary or the Pleistocene period that the
mild climate of these regions underwent sudden alterations,
producing what is called the Glacial period. The limits of this
Glacial period may not so exactly coincide with those of the
Pleistocene as to enable us to say that they were mathematically
co-extensive, but, still, in a rough sense we may take these two
periods as coinciding with each other. It is impossible within the
limits of a short chapter to give even a summary of the evidence
proving the existence of one or more Glacial epochs in the
Pleistocene period. We may, however, briefly indicate its nature
and see what the geologists and the physicists have to say as
regards the causes that brought about such extensive changes of
climate in the Quaternary era. The existence of the Glacial
period is no longer a matter of doubt, though scientific men are
not agreed as to the causes which produced it. Ice-sheets have
not totally disappeared from the surface of the earth, and
we can still watch the action of ice as glaciers in the valleys
of the Alps or in the lands near the Pole, like Greenland
which is still covered with a sheet of ice so thick as to make
it unfit for the growth of plants or the habitation of animals.
Studying the effects of glacial action in these places geologists
have discovered abundant traces of similar action of ice in
former times over the whole of Northern Europe and America.
Rounded and scratched stones, till or boulder-clay, and the

THE GLACIAL PERIOD. 23
rounded appearance of rocks and mountains clearly point out
that at one period in the history of our globe northern
parts of Europe and America must have been covered
for a long time with a sheet of ice several hundreds of feet in
thickness. The ice which thus invaded the northern portion
of America and Europe did not all radiate from the Pole. The
evidence of the direction of the striæ, or scratches engraved
on rocks by ice, undoubtedly proves that the ice-caps spread out
from all elevated places or mountains in different directions. These
ice-sheets of enormous thickness covered the whole of Scandinavia,
filled up the North Sea, invaded Britain down to the Thames
valley, greater portion of Germany and Russia as far south as
Moscow and almost as far east as the Urals. It is calculated that
at least a million of square miles in Europe and more in North
America were covered by the debris of rocks ground down by
these glaciers and ice-caps, and it is from this debris that geologists
now infer the existence of an Ice Age in early times. The examina-
tion of this debris shows that there are at least two series of
boulder clay indicating two periods of glaciation. The debris of
the second period has disturbed the first layer in many places, but
enough remains to show that there were two distinct beds of
boulder-clay and drifts, belonging to two different periods. Prof.
Geikie mentions four such Glacial periods, with corresponding
Inter-Glacial periods, as having occurred in succession in Europe
during the Pleistocene period. But though this opinion is not
accepted by other geologists, yet the existence of two Glacial
epochs, with an intervening Inter-Glacial period, is now consider-
ed as conclusively established.
A succession of cold and warm climates must have chara-
cterised these Glacial and Inter-Glacial periods, which were
also accompanied by extensive movements of depression and
elevation of land, the depression taking place after the land
was weighed down with the enormous mass of ice. Thus

24 THE ARCTIC HOME IN THE VEDAS.
a period of glaciation was marked by elevation, extreme cold and
the invasion of the ice-caps over regions of the present Temperate
zone; while an inter-glacial period was accompanied by depression
of land and milder and congenial climate which made even the
Arctic regions habitable. The remains of the Palæolithic man
have been found often imbedded between the two boulder-clays
of two different Glacial periods, a fact which conclusively estab-
lishes the existence of man in the Inter-Glacial period in the
Quaternary era. Prof. Geikie speaking of the changes of climate
in the Glacial and Inter-Glacial period remarks that "during the
Inter-Glacial period the climate was characterised by clement
winters and cool summers so that the tropical plants and animals,
like elephants, rhinoceroses and hippopotamuses, ranged over the
whole of the Arctic region, and in spite of numerous fierce carni-
vora, the Palæolithic man had no unpleasant habitation there."*
It will thus be seen that in point of climate the Pleistocene period,
or the early Quaternary era, was intermediate between the early
geological ages when uniform genial climate prevailed over the
globe, and the modern period when it is differentiated into zones.
It was, so to speak, a transitional period marked by violent changes
in the climate, that was mild and genial in the Inter-Glacial, and
severe and inclement during the Glacial period. It was at the
beginning of the Post-Glacial or the Recent period that modern
climatic conditions were established. Prof. Geikie is, however,
of opinion that even the beginning of the Post-Glacial period was
marked, at least in North-Western Europe, by two alternations
of genial and rainy-cold climate before the present climatic condi-
tions became established.†
But though the fact of the Ice Age and the existence of a
milder climate within the Arctic regions in the Inter-Glacial
Fragments of Earth Lore, p. 266. † Prehistoric Europe, p. 530.

THE GLACIAL PERIOD. 25
time is indubitably proved, yet scientific men have not been as
yet able to trace satisfactorily the causes of this great catastrophe.
Such immense mass of ice as covered the whole of Northern
Europe and America during this period could not, like anything
else, come out of nothing. There must be heat enough in certain
parts of the globe to create by evaporation sufficient vapour, and
aerial currents are required to transfer it to the colder regions
of the globe, there to be precipitated in the form of ice. Any
theory regarding the cause of the Ice Age which fails to take
this fact into account is not only inadequate but worthless. A
succession of Glacial periods, or, at any rate, the occurrence of
two Glacial periods, must again be accounted for by the theory
that may be proposed to explain these changes; and if we test the
different theories advanced in this way, many of them will be at
once found to be untenable. It was, for instance, once urged that
the Gulf Stream, which, at present, imparts warmth to the
countries in the North-West of Europe, might have been turned
away from its course in the Pleistocene period by the submergence
of the Isthmus of Panama, thus converting the countries on the
North-Western coast of Europe into lands covered by ice. There
is, however, no geological evidence to show that the Isthmus of
Panama was submerged in the Pleistocene period, and we must,
therefore, give up this hypothesis. Another theory started to
account for the catastrophe was that the earth must have
passed through cold and hot regions of space, thus giving rise to
Glacial and Inter-Glacial periods respectively. But this too is
unsupported by any evidence. A third suggestion advanced
was that the supply of solar heat on earth must have
varied in such a way as to give rise to warm and cold
climates but this was shown to be a mere conjecture. A
change in the position of the earth's axis might indeed cause
such sudden changes in the climate; but a change in the
4

26 THE ARCTIC HOME IN THE VEDAS.
axis means a change in the equator, and as the earth owing to its
diurnal rotation causes the equatorial regions to bulge out, a
change in the axis would give rise to a second equatorial protu-
berance, which, however, is not observable, and the theory cannot,
therefore, be accepted. A gradual cooling of the earth would
make the Polar regions habitable before the other parts of the
globe; but a succession of Glacial epochs cannot be accounted for
on this theory.
Thus out of the various theories advanced to account for the
vicissitudes of climate in the Pleistocene period only two have
now remained in the field, the first that of Lyell which explains
the changes by assuming different distribution of land and water
combined with sudden elevation and submergence of large landed
areas, and the second that of Croll which traces the glaciation to
the precession of the equinoxes combined with the high value of
the eccentricity of the earth's orbit. Lyell's theory has been
worked out by Wallace who shows that such geographical changes
are by themselves sufficient to produce heat and cold required to
bring on the Glacial and Inter-Glacial periods. We have seen
that in earlier geological ages a pleasant and equable climate
prevailed over the whole surface of the globe owing mainly to
different distribution of land and water, and the theory advanced
by Lyell to account for the Glacial epoch is practically the same.
Great elevation and depression of extensive areas can be effected
only in thousands of years, and those who support Lyell's theory
are of opinion that the duration of the Glacial epoch must be
taken to be about 200,000 years in order to account for all the geo-
graphical and geological changes, which, according to them, were
the principal causes of the Glacial period. But there are other
geologists, of the same school, who hold that the Glacial
period may not have lasted longer than about 20 to 25
thousand years. The difference between the two estimates

THE GLACIAL PERIOD. 27
is enormous; but in the present state of geological evidence it is
difficult to decide in favour of any one of these views. All that
we can safely say is that the duration of the Pleistocene period,
which included at least two Glacial and one Inter-Glacial epoch,
must have been very much longer than the period of time which
has elapsed since the commencement of the Post-Glacial period.
According to Sir Robert Ball the whole difficulty of finding
out the causes of the Glacial period vanishes when the solution of
the problem is sought for in astronomy rather than in geography.
Changes which seem to be so gigantic on the globe are, it is said,
but daily wrought by cosmical forces with which we are familiar
in astronomy, and one of the chief merits of Croll's theory is
supposed to consist in the fact that it satisfactorily accunts for a
succession of Glacial and Inter-Glacial epochs during the Pleisto-
cene period. Dr. Croll in his Climate and Time and Climate and
Cosmology has tried to explain and establish his theory by elaborate
calculations, showing that the changes in the values of the variable
elements in the motion of the earth round the sun can adequately
account for the climatic changes in the Pleistocene period. We
shall first briefly state Dr. Croll's theory, and then give the
opinions of experts as regards its probability.
Let PQ'AQ represent the orbit of the earth round the sun.
This orbit is an ellipse, and the sun, instead of being in the centre
C, is in one of the focii S or s. Let the sun be at S. Then the
distance of the sun from the earth when the latter is at P would
be the shortest, while, when the earth is at A it will be the longest.
These points P and A are respectively called perihelion and
aphelion. The seasons are caused, as stated above, by the axis of
the earth being inclined to the plane of its orbit. Thus when the
earth is at P and the axis turned away from the sun, it will produce

28 THE ARCTIC HOME IN THE VEDAS.
winter in the northern hemisphere; while when the earth is at
A, the axis, retaining its direction, will be now turned towards
the sun, and there will be summer in the northern hemisphere.
If the axis of the earth had no motion of its own, the seasons
will always occur at the same points in the orbit of the earth, as,
for instance, the winter in the northern hemisphere at P and the
summer at A. But this
axis describes a small
circle round the pole of
the ecliptic in a cycle of
25,868 years, giving rise
to what is called the pre-
cession of the equinoxes,
and consequently the
inclination of the earth's axis to the plane of its orbit is not always
the same at any given point in its orbit during this period. This
causes the seasons to occur at different points in the earth's orbit
during this great cycle. Thus if the winter in the northern hemi-
sphere occurred when the earth was at P at one time, some
time after it will occur at p and the succeeding points in the orbit
until the end of the cycle, when it will again occur at P. The
same will be the case in regard to summer at the point A and
equinoxes at Q and Q'. In the diagram the dotted lines qq' and
pa represent the new positions which the line QQ' and PA will
assume if they revolve in the way stated above. It must also be
noted that though the winter in the northern hemisphere may
occur when the earth is at p instead of at P, owing to the aforesaid
motion of its axis, yet the orbit of the earth and the points of
perihelion and aphelion are relatively fixed and unchangeable.
Therefore, if the winter in the northern hemisphere occurs at p,
the earth's distance from the sun at the point will be greater than
when the earth was at P. Similarly, in the course of the

THE GLACIAL PERIOD. ·29
cycle above mentioned, the winter in the northern hemisphere will
once occur at A, and the distance of the earth from the sun will
then be the longest. Now there is a vast difference between a
winter occurring when the earth is at P and a winter occurring
when it is at A. In the first case, the point P being nearest to the
sun, the severity of the winter will be greatly modified by the near-
ness of the sun. But at A the sun is farthest removed from the
earth, and the winter, when the earth is at A, will be naturally very
severe; and during the cycle the winter must once occur at A.
The length of the cycle is 25,868 years, and ordinarily speaking
half of this period must elapse before the occurrence of winter is
transferred from the earth's position at P to its position at A.
But it is found that the points P and A have a small motion of
their own in the direction opposite to that in which the line of
equinoxes QQ' or the winter point p moves along the orbit. The
above cycle of 25,868 years is, therefore, reduced to 20,984, or, in
round number, 21,000 years. Thus if the winter in one hemisphere
occurs when the earth is at P, the point nearest to the sun in the
orbit, it will occur in the same hemisphere at A after a lapse of
10,500 years. It may be here mentioned that in about 1,250
A. D., the winter in the northern hemisphere occurred when the
earth in its orbit was at P, and that in about 11,750 A. D. the
earth will be again at A, that is, at its longest distance from
the sun at the winter time, giving rise to a severe winter. Calculat-
ing backwards it may be seen that the last severe winter at A
must have occurred in the year 9,250 B. C.* It need not be
mentioned that the winter in one hemisphere corresponds with
the summer in the other, and that what is said about winter in
the northern hemisphere applies mutatis mutandis to seasonal
changes in the southern hemisphere.

• See Herschel's Outlines of Astronomy, Ed. 1883, Arts. 368, 369.

30 THE ARCTIC HOME IN THE VEDAS.
There is another consideration which we must take into
account in estimating the severity of winter or the mildness of
summer in any hemisphere. If the summer be defined to be the
period of time required by the earth to travel from one equinoctial
point Q' to another equinoctial point Q, this interval cannot always
be constant for we have seen that the winter and summer points
(P and A), and with them the equinoctial points (Q and Q') are
not stationary, but revolve along the orbit once in 21,000 years.
Had the orbit been a circle, the lines qq' and pa will have always
divided it in equal parts. But the orbit being an ellipse these
two sections are unequal. For instance, suppose that the winter
occurs when the earth is at P, then the duration of the summer
will be represented by Q'AQ, but when the winter occurs at A
the summer time will be represented by QPQ', a segment of the
ellipse necessarily smaller than Q'AQ. This inequality is due to
the ellipticity of the orbit, and the more elongated or elliptic the
orbit is, the greater will be the difference between the durations
of summer and winter in a hemisphere. Now the ellipticity of
the orbit is measured by the difference between the mean and
the greatest distance of the earth from the sun, and is called in
astronomy the eccentricity of the earth's orbit. This eccentricity
of the earth's orbit is not a constant quantity, but varies, though
slowly, in course of time, making the orbit more and more
elliptical, until it reaches a maximum value, when it again begins
to reduce until the original value is reached. The duration of
summer and winter in a hemisphere, therefore, varies as the
value of the eccentricity of the earth's orbit at that time; and it
has been stated above that the difference between the duration of
summer and winter also depends on the position of the equinoctial
line, or of the points in the earth's orbit at which the winter and
the summer in a hemisphere occur. As the joint result of

THE GLACIAL PERIOD. ·31·
these two variations, the difference between the durations of summer
and winter would be the longest, when the eccentricity of the
earth is at its maximum and according as the winter and summer
occur at the points of perihelion or aphelion. It has been found
that this difference is equal to 33 days at the highest, and that at
the present day it is about 7½ days. Thus if the winter in the
northern hemisphere occurs when the earth is at P in its orbit
and the eccentricity is at its maximum, the winter will be shorter
by 33 days than the summer of the time. But this position will
be altered after 10,500 years when the winter, occurring at A,
will, in its turn, be longer than the corresponding summer by the
same length of time, viz., 33 days.
Now, since the earth describes equal areas in equal times in
its orbit, Herschel supposed that in spite of the difference between
the duration of summer and winter noticed above, the
whole earth received equal amount of heat while passing from one
equinox to another, the "inequality in the intensities of solar
radiation in the two intervals being precisely compensated by the
opposite inequality in the duration of the intervals themselves."
Accepting this statement Dr. Croll understated his case to a
certain extent. But Sir Robert Ball, formerly the Astronomer
Royal of Ireland, in his recent work On the Cause of an Ice Age
has demonstrated, by mathematical calculation, that the above
supposition is erroneous, and that the total amount of heat received
from the sun by each hemisphere in summer and winter varies as
the obliquity of the earth or the inclination of its axis to the
ecliptic, but is practically independent of the eccentricity of the
earth's orbit. Taking the total sun-heat received in a year by
each hemisphere to be 365 units, or on an average one
unit a day, and taking the obliquity to be 23° 27', Sir.
Robert Ball has calculated that each hemisphere would
receive 229 of these heat-units during summer and only 136

32. THE ARCTIC HOME IN THE VEDAS.
    during winter, whatever the eccentricity of the earth
    may be. But though these figures are not affected by
    the eccentricity of the orbit, yet we have seen that the
    duration of the summer or winter does vary as the eccentricity.
    Supposing, therefore, that we have the longest winter in the
    northern hemisphere, we shall have to distribute 229 heat-units
    over 166 days of a short summer, and 136 heat-units over 199
    days of a long winter of the same period. In other words, the
    difference between the daily average heat in summer and winter
    will, in such a case, be the greatest, producing shorter but warmer
    summers and longer and colder winters; and ice and snow
    accumulated in the long winter will not be melted or removed
    by the heat of the sun in the short summer, giving rise, thereby,
    to what is known as the Glacial period in the northern hemisphere.
    From what has been stated above, it may be seen that the southern
    hemisphere during this period will have long and cool summers
    and short and warm winters, a condition precisely reverse to that
    in the northern hemisphere. In short the Glacial and Inter-
    Glacial periods in the two hemispheres will alternate with each
    other every 10,500 years, if the eccentricity of the earth be suffi-
    ciently great to make a perceptibly large difference between the
    winters and the summers in each hemisphere.
    If Dr. Croll had gone only so far, his position would have
    been unassailable, for the cause, enumerated above, is sufficiently
    potent to produce the climatic changes attributed to it. At any
    rate, if this was not the sole cause of a succession of Glacial and
    Inter-Glacial periods, there could be no doubt that it must have
    been an important contributory cause in bringing about these
    changes. But taking the value of the eccentricity of the earth's
    orbit from the tables of Leverrier, Dr. Croll calculated that during
    the last three million years there were three periods of maximum
    eccentricity; the first of 170,000, the second of 260,000, and the third