yet in others, and those by far the more numerous, the traces of gradual change were evident, and the facts not to be accounted for by any other hypothesis; and thus by degrees it came to be acknowledged on all hands, that either the accepted date of the creation must be abandoned, or else that there had been many creations, of which ours was the latest.

In support of this latter theory many strange forms presented themselves to geologists; bones converted into stone by the lapse of ages-the curious freaks of nature of the pre-scientific naturalists-but recognized as undoubtedly parts of once living organisms by students of the new science, although belonging to creatures having apparently no representatives on our present earth; antediluvian they were called, and the name has remained in unscientific parlance; but it was soon perceived that although some of the types had died out, many remained but slightly modified, even to our own day, the evident progenitors of living species; and anatomical science began to discover here also a gradual progression-instead of a sudden extinction, followed by a new creation-till at last it was seen and acknowledged that there was no break in the chain of continuity; that from the eozoon to the stately elephant of the present day, the tide of life had flowed on unbroken and unchecked. Not that this was understood in the Darwinian sense as the effect of evolution and the survival of the fittest, but simply that the various types were found to have co-existed and overlapped each other, and not to have suddenly died out, to be superseded by a new creation. Some types indeed seemned to have run through the whole series, with only slight modifications; but this was certainly not the case with

man.

Here the disciples of the ancient faith took their stand, and for a long time maintained their ground unchallenged. Man was certainly a later and a distinct creation; the earth might indeed have been preparing for him for long ages; the six days of creation might have figuratively represented six geologic periods during

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, AdhemarSir 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

1

science, 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.