THE

AMERICAN NATURALIST.

Vol. IV. - OCTOBER, 1870.- No. 8.

RECENT ADVANCES IN GEOLOGY.*

BY J. W. FOSTER, LL. D.

Mr. President, and Gentlemen of the American Association for the Advancement of Science:

THERE is an article contained in our Constitution which requires the retiring President to address the Association in general meeting; and custom has prescribed that he select. for his theme some new and important discoveries in science, or some new inventions and processes in the arts.

It is in the discharge of this duty that I appear before you on this occasion, and solicit your attention for the passing hour. So vast is the domain of science, and so numerous have become its cultivators in almost every part of the world, that, even if I had the capacity, the labor of embodying the results of a single year, in a brief address, would be a mere accumulation of details devoid of that spirit which gives them value-generalization.

I shall, therefore, restrict myself to the researches which have been made in those departments of science which with me have been the subjects of special investigation; and shall

Address of the retiring president of the American Association for the Advancement of Science, J. W. Foster, LL. D., delivered at Troy, New York, on the evening of August 18, 1870.

Entered according to Act of Congress, in the year 1870, by the PEABODY ACADEMY OF SCIENOR, in the Clerk's Office of the District Court of the District of Massachusetts.

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seek to set forth what others have accomplished, rather than to advance original views.

It will be found that, throughout all time, since the earth became fitted for the habitation of organic life, that there have been great cycles of heat and cold, and that these cycles have exercised a marked influence in the modification of all terrestrial forms. To traverse the whole ground, would employ too much time; and I shall, therefore, restrict myself to the changes which barely antedate the Human Epoch.

We know that the Tertiary Age, so far, at least, as related to the northern hemisphere, was characterized by a warm and equable climate, extending even to the Polar Sea. Where now blooms the Andromeda close by banks of perpetual snow, at that time grew a luxuriant forest vegetation. McClure's sledging party gathered fragments of fossil wood, acorns, and fir cones in the interior of Banks's Land, far within the limits of the Arctic Circle. As high as latitude 70° N. in Greenland, large forests lie prostrate and encased in ice. At Disco Island, the northern verge of European settlement, the strata are full of the trunks, branches, leaves, and even the seeds and fruit-cones of trees, comprising firs, sequoias, elms, magnolias, and laurels,―a vegetation characteristic of the Miocene Period of Central Europe. Professor Heer particularly notices the Sequoia Langsdorfii, which is very closely allied to the Sequoia sempervirens of the Coast Range of California.

Spitzbergen was clothed with a forest vegetation equally luxuriant, amongst which the Swedish naturalists recognize the swamp-cypress (Taxodium dubium) in a fossilized state, at Bell's Sound (76° N.), and the plantain and linden in King's Bay (78° and 79° N.). The same Sequoia was observed by Sir John Richardson within the Arctic Circle west of MacKenzie River. The lignite beds of Iceland have yielded to the botanists, Steenstrup and Heer, fifteen arborescent forms identical with the Miocene plants of Europe.

In the flora of the Great Lignite Basin of Nebraska, which is referred to the Miocene age, Hayden has detected the oak, the tulip or poplar, the elm and walnut, and a true fanpalm, with a leaf-spread of twelve feet;-all, however, of extinct species. These forms he regards as characteristic of a sub-tropical climate, such as now prevails in the Gulf States. The fan-palm (Sabal Campbellii) is the representative of the Sabal major of the European Tertiaries, and the Sabal palmetto of our Southern States.

The Cinnamonium, an unquestioned tropical type, while not thus far detected in the Missouri Basin, has been found by Lesquereaux in the Cretaceous (?) beds of Bellingham Bay, on our Northwestern coast; in the Eocene of the Lower Mississippi, and in the lignite beds of Vermont.

Professor Newberry, in a review of the flora of the Cretaceous and Tertiary Ages of North America, thus remarks:

"We have, therefore, negative evidence, though it may be reversed at an early day by further observations, that the climate of the interior of our continent, during the Tertiary Age, was somewhat warmer than during the Cretaceous Period; and that during both the same relative differences of climate prevailed between the western and central portions that exist at the present day."

The Drift Epoch was ushered in by a marked change in physical influences, by which the whole flora of the extreme northern hemisphere was so far affected that certain forms were blotted out of existence, while other forms were forced to seek, by migration, a more congenial climate, and accommodate themselves to altered conditions. In the higher regions we find a predominating growth of mosses and saxifrages, and at the southern limits of the Drift a buried vegetation of an Alpine character.

If we examine the fauna of the two epochs-particularly the land animals which we may suppose to be peculiarly susceptible to atmospheric changes-we shall find that there

was a marked modification of forms. Dr. Leidy, in his late work on the extinct mammalian faunæ of Dakota and Nebraska, states that, of the thirty-two genera of Miocene animals, not one occurs in the Quaternary formation of North America. In comparing the Miocene and Pliocene fauna with each other, as represented mainly by the remains from the Mauvaises Terres and the Niobrara River, scarcely a genus is common to both. "In view," he continues, "of the consecutive order and close approximation of position of the two formations and faunæ, such exclusiveness would hardly have been suspected." The greater similitude of the Miocene and Pliocene faune with the contemporaneous fauna of the Old World, has led him to suggest that the North American continent was peopled, during the Tertiary Epoch, from the West. "Perhaps this latter extension," he continues, "occurred from a continent whose area now forms the bottom of the Pacific Ocean, and whose Tertiary faunæ is now represented east and west by the fossil remains of America on the one hand, and of Asia, with its peninsula, Europe, on the other."

The topographical features of the two continents and the hydrographical soundings of the two oceans, render this supposition probable. Between Ireland and Newfoundland there is a great plateau, which an elevation of the earth's crust to the extent of a few thousand feet would convert into dry land; and Behring's Straits, which now separate Asia and North America, are, at their narrowest points, but thirty miles wide, and their shallowest depth is but twentyfive fathoms.

And here the paleontologist comes to the aid of the hydrographer, and, by their joint labors, the one renders probable what the other has conjectured as possible-the former union of the two hemispheres. Zoology would indicate that such was the fact during the Pliocene Epoch, in which will probably be found the origin of those mammalian types contemporary with the elder man, and represented by

the extinct Proboscidians and Ruminants. None of these large animals could probably have passed over the straits which now divide these regions, and the close alliance in form would indicate a common origin. We infer, therefore, that the subsidence during the Drift Epoch cut off the communication between the two hemispheres, and the refrigeration which then took place, served to disperse the colossal animals, who sought by migration to lower latitudes a climate congenial to their nature.

As in Europe we find the remains of these northern types intermingled with those of an African type—the hippopotamus, which in his summer migrations strayed as far north as England; so on this continent we had, during this epoch, the great sloths, represented by the megalonyx and mylodon, whose congeners at this time exist in South America. Thus there was an inosculation, so to speak, of two distinct and contemporaneous faunæ.

It is an inquiry of the highest interest-perhaps as much so as any connected with the physical history of the past: How far has man been a witness of these stupendous changes? It is not until towards the close of the Drift Epoch, that we are enabled to detect unmistakable signs of his works, although there are not wanting proofs which would refer his origin to an earlier date- the Pliocene. So numerous and well-attested are the facts, that we must now regard him as the contemporary of many of the great mammals which have ceased to exist, and the subject of physical conditions very different from what now prevail. To account for these changes requires the lapse of a longer period of time than has heretofore been assigned to his existence upon earth.

Thus within a few years has been opened a sphere of investigation which has enlisted a large class of able observers, and their labors have thrown a flood of light upon the origin of our race. Ethnography has become aggrandized into one of the noblest of sciences. However conflicting these revelations may be to our preconceived notions, they