which the "great whales" and "winged fowl," the "cattle and creeping thing, and beast of the earth after his kind," might have severally predominated; and it was a further proof of the wisdom and goodness of the Creator, that the larger and presumably more hurtful of these great beasts had been suffered to die out, before Adam was formed from the dust of the ground, a perfect man, endowed with faculties which raised him far above the brute creation, and taught by God Himself to use those faculties for the subjugation of all created things, in order that he might attain thereby to the highest degree of civilization, even if not from the first instructed in all wisdom, and able to impart to his posterity a perfect knowledge of all the arts and sciences possible to mankind. No trace of this highly-endowed being could be found in geologic strata; it was only in the most superficial deposits that human remains and human works could be disinterred, and he certainly had no existence in those ages when the earth was filled with strange uncouth forms, differing so widely from those of our day.

This position appeared for a long time impregnable, but lately even this has been assailed, and already it totters to its foundation, for the works of man, andalthough rarely-his remains also, have been found in positions and under circumstances which cannot fail to convince the unprejudiced mind, that man has existed for countless ages; and although he may not have been contemporary with the gigantic Saurians and other fossil types now extinct, yet that he certainly did co-exist with huge mammals, which have long passed away. But before we can appreciate the evidence upon which this belief is based, we must consider the intimate connection which exists between the sciences of astronomy, geology, palæontology, and anthropology.

CHAPTER II.

ASTRONOMICAL THEORIES.

Geological Facts due to Astronomical Causes still in Operation The Glacial Period—Theories of Croll, Lyell, Adhemar— Sir John Lubbock, Hopkins, and Dr. John Evans on Change of Earth's Axis-Professor Haughton-Sir W. Thompson on Rigidity of Earth-Semi-Tropical Plants in the Arctic Region -Traces of Glaciation in Europe, North America, India, and South Africa-Bearing of the Glacial Epoch upon the Antiquity of Man.

THE changes which geology has traced in the crust of the earth are due mainly to astronomical causes which have existed through all time, and still continue to operate. The shape of our globe, at first doubtless a perfect sphere, has become modified by its varied motions in space, and the gradual flattening of the poles and shrinkage of bulk has probably caused most of the disruptions of geologic strata and changes in the distribution of land and water which can be traced throughout the geologic series.

Whether our globe has now become rigid and solid to the centre, and therefore no longer subject to the changes and vicissitudes which marked its earlier history, or whether the solid matter forms only a crust resting upon a molten sea of mineral matter in a state of incandescence, the crust remaining sufficiently elastic to allow of certain bulges due to the external attraction of planetary matter, and of occasional rents and fissures consequent upon such surface changes, remain among the unsolved problems of geological and astronomical

science,1 as does also that singular change of climate designated as the "Glacial Period," or the "Great Ice Age," which possesses such great and peculiar interest as connected with the antiquity of man.

That the variety of climates on our globe is due to the inclination of the poles is well known, but that this inclination did not always exist is rendered probable by the researches of astronomers who find it absent in the case of the superior planets. That the change of position has caused a large ice-cap to accumulate round either pole, both on our own globe and on Mars, the planet most nearly resembling our own, we see and know; but what could have caused the great increase of this ice-cap round the north pole so as to extend far down into the continent of Europe, covering Great Britain, Scandinavia, and the northern part of the American continent with a huge sheet of ice, but leaving Siberia free; and why this phenomenon should have occurred again and again with greater or less intensity, are questions which have given rise to many theories and much ingenious speculation.

The most plausible and generally received explanation of this strange phenomenon is that given by Mr. Croll, in his book entitled Climate and Time, wherein by a series of elaborate computations based upon well-known astronomical facts, he proves that as a consequence of the precession of the equinoxes and the varying ellipticity of the earth's orbit, the winters of the northern hemisphere, which now occur when the earth is in perihelion, that is when nearest to the sun, will in course of time take place not only when in aphelion, or most distant from that luminary, but also when the eccentricity of the orbit is at its greatest, making a difference of thirteen and a half millions of miles in distance, and increasing the winters occurring during that epoch by many days, which, repeated from year to year during centuries, would necessarily cause an increase of cold and an accumulation of ice round the north pole, sufficient to account for the Glacial Period. Mr. Croll, in

1 Sir Wm. Thompson believes the earth to be as rigid as steel.

calculating the eccentricity of the earth's orbit backwards for a million of years, finds two periods in which the conditions before enumerated would be favourable to the production of a glacial age. One of these occurred 800,000 years ago, and the other 200,000. Sir Charles Lyell inclined to the former period as that of the glacial age of geologists, but Sir John Lubbock prefers the latter as the most probable; because "it seems unlikely that the present fauna of Europe should have continued to exist without alteration for so long a period as 800,000 years, and the variations in the range and distribution of aquatic and terrestrial animals might have occurred in less than 200,000 years, under the great changes in climate which have taken place." 1

Seeing that geologists trace at least two glacial epochs, it is possible that both Lyell and Lubbock may be right, and that Mr. Croll's theory may be the true solution of the difficulty which geologists have hitherto found, in accounting for the alternations of heat and cold clearly traceable in the past history of the world; but other theories which have been advanced to account for this glacial period and for a universal deluge must also be glanced at. M. Adhemar, working somewhat in the same groove as Mr. Croll, whom he preceded by some years, imagined that deluges were caused by the accumulation of ice round one pole, which would in time be sufficient to cause a change in the earth's centre of gravity; and hence the sea, rushing alternately from north to south, or from south to north every 10,500 years, would cause a deluge, which would of course alter the disposition of land and water, and cause the destruction of the greater portion of the terrestrial fauna and flora at that time existent; but the records. of geology are for the most part opposed to violent cataclysms, and hence the theory of M. Adhemar is not favoured by geologists; and astronomers would hardly allow of the possibility of the sudden heeling over of a body like the earth without occasioning more serious

1 Pre-historic Times, p. 403.

consequences than an alteration in the disposition of land and water. Mr. Hopkins suggested several hypotheses to account for glacial periods, attributing them either to a variation in the intensity of solar radiation, or to the possibility that the sun in its motion through space may have recently passed from a colder into a warmer region; but Sir John Lubbock,' who has passed all the various hypotheses of modern writers under review, points out that these theories are untenable, because the formation of glaciers requires an alternation of heat and cold. Another hypothesis suggested by Mr. Hopkins, and for which he claims something approaching an ascertained fact, is an alteration in, or rather the absence of, the Gulf Stream, which, he says, would lower the January temperature of Western Europe ten degrees, while a cold current from the north would make a further difference of three or four degrees; and this, Mr. Hopkins asserts, must follow the submergence of North America. But Sir John Lubbock shows that this also would necessitate an immense time, for "if when the gravels and loëss of the Somme and the Seine were being deposited, the Gulf Stream was passing up what is now the valley of the Mississippi, then it follows that the formation of the loëss in that valley and its delta, an accumulation which Sir Charles Lyell has shown would require a period of about 100,000 years, would be subsequent to the excavation of the Somme valley, and to the presence of man in Western Europe." 2

But the hypothesis which next to that of Mr. Croll has been received with most favour in the scientific world, is that which attributes the evidences of glaciation in Central Europe to a change in the position of the earth's axis. This solution of the grand geological problem had suggested itself to my mind many years ago; but upon its first proposition by Mr. Hopkins, or some other scientist, it was scouted as impossible, improbable, and absurd. Like many other theories, however, and some great truths, it has outlived the 2 Ibid. p. 393.

1 Pre-historic Times.