VOL. XI, NO. 6. DES MOINES, IOWA, JULY, 1914.

3D SERIES

FOUNDATION OF MODERN GEOLOGIC SCIENCE IN AMERICA.

BY CHARLES KEYES.

For permitting Iowa to furnish the foundation stones of modern science in the New World the Fates appear mainly responsible. Just a hundred years ago this work was accomplished. In veral respects its bearings are more than statewide. In the history of American geology it assumes national import and far-reaching influence. In the history of that science the circumstances surrounding the earliest discoveries within the limits of our State are worthy of special record and attention.

The scientific discoveries to which I allude were made in Iowa-land before Iowa was a State, before she was a territory, before she was hardly a part of the United States. It was in the earliest springtime of the last century, when our Nation was yet new, when the region was still remote and unknown, and when even the land itself was yet to receive its name.

For several reasons this pioneer scientific work is of exceptional historic interest. It was the first time that modern geological principles were successfully applied in this country. It was, up to the time, the boldest stroke at universal correlation of geological formations ever attempted by geologists. It was the first definite recognition of the two greatest geologic formations found on our continent. It was the first chronologic comparison of American Carbonic rocks with those of the typical locality in the Old World. It furnished the basis for all subsequent investigations of the midcontinental region. It gave rise to a host of perplexing problems many of which are still unsolved. Where else in all the

world have not the echoes of a century-long discussion long since died away? Singular is it that our Iowa should be the pivotal point.

When in England about a century ago, earth-study was made a modern science through William Smith's famous geologic discovery that the relative age and natural sequence of rock-layers were susceptible of accurate determination by means of the contained organic remains, America very early and from a wholly unexpected quarter furnished important aid in support of the newly-established principles. The circumstances were long since all but forgotten. In the few casual references made to them in later years either their importance was misunderstood or familiarity with the attendant conditions was entirely wanting. As the first successful application of modern geological principles in the New World the episode must ever remain of great historic interest.

Singularly, this primal American effort to correlate by their faunal contents geologic formations widely separated geographically, was not made in that portion of our continent which was most accessible and where it was most natural to expect it-that is, along the well-settled Atlantic borderbut it was in the then remotest section of the Upper Mississippi valley. First fruits of research and observation were obtained in a region which was then perfect wilderness, but which now forms part of the great and populous State of Iowa. Moreover, these remarkable observations were made within a decade of the time when the novel method was originally announced in England. They antedated by fifteen years Samuel Morton's similar effort on the Tertiaries of our Atlantic coast, commonly regarded as the maiden attempt in America along these lines. By two decades they were in advance of the first work of that pioneer American paleontologist, Lardner Vanuxem. They anticipated by a full generation the famous investigations of Thomas Conrad and James Hall in New York. Indeed they were the means of actually and correctly interpreting the true position and biotic relations of the Carbonic rocks of the continental interior a

half century before their geologic age was otherwise generally admitted. The Mississippian limestones, as the rocks are now called, remain today as compact and as sharply delimited a sequence of geologic terranes as they appeared when first recognized in that memorable summer of the year 1809.

This successful use in America of faunal criteria for purposes of solving problems of geologic correlation and of identifying geological formations was the first real ray of modern light to penetrate the stratigraphic darkness shrouding the New World. The happy application of these criteria was due directly to the keen scientific perception and peculiar reasoning of one who was never known as a geologist at all, but who was raised to fame through a wholly different channel of scientific activity. This truly remarkable personage was Thomas Nuttall, botanist.

Nuttall's extensive travels in America were undertaken chiefly in the interests of his monumental works on North American plants and of his valuable contributions to American ornithology. On his first great trip, after traversing the southern shore of Lake Erie, and coasting by canoe Lakes Huron and Michigan, he entered Green bay, and, following to the West that famous all-water route which the Indians had used from time immemorial, ascended Fox river to the portage to the Wisconsin river, down which stream he floated to its mouth, near Prairie du Chien, thence down the Mississippi river to St. Louis. Subsequent trips took him far up the Missouri and Arkansas rivers.

On his Mississippi venture, besides garnering great quantities of interesting plants and taking voluminous notes on the birds, he appears to have made extensive collections of the fossils which he found along his path abundantly scattered through the limestones which in high cliffs bordered both sides of the great stream. In the course of his explanations of the geologic features of the region through which he passed, Nuttall naively notes that he is "fully satisfied that almost every fossil shell figured and described in the Petrifacta Derbiensia of Martin was to be found throughout the great calcareous platform of Secondary rocks exposed in the

eastern Mississippi valley." Thus by means of fossils he parallels these limestones of the Mississippi river with the Mountain limestone of the Pennine range, in Derbyshire, England, to which, several years later, Conybeare gave the title of Carboniferous.

Along the Mississippi river, as we now know, Nuttall really encountered little else than rocks of Early Carbonic age, so that his identifications of the fossils were doubtless, with very few exceptions, correct. Moreover, at this date and for some time afterward, the lower portions of the exposed stratigraphic sections, it must be remembered, were entirely undifferentiated, the great sequence of older beds which were subsequently separated from one another being jumbled together under the title of the Transition group. It was not until more than a quarter of a century later that out of them, in Britain, Murchison and Sedgwick established the Cambrian, Silurian and Devonian systems.

Another important geologic correlation is to be credited to Nuttall. On his journey up the Missouri river, in 1810, which he undertook with John Bradbury,' a Scotch naturalist, he reached the Mandan villages on the upper reaches of that stream. He makes especial mention of the Omaha village situated below the mouth of the Big Sioux river. A short distance upstream from the last-mentioned point he examined strata which, by means of their fossils presumably, he referred to the Chalk division of the Floetz, or Secondary rocks of northern France and southern England. This is the earliest definite recognition of beds of Cretacic age in America. It preceded by a decade and a half the separation by John Finch, of the newer Secondary rocks from the Tertiary section in the Atlantic states, and Lardner Vanuxem's and Samuel Morton's references of the same deposits to the Cretaceous age. Thus, also, was another great succession of one of our main geologic periods discovered in a then remote part of our continent years before it was recognized in the East.

Travels in interior of America in 1809-1811, London, 1817.