Part 12

It had now become clearly evident, moreover, that the fossils from the older formations were all extinct species, and that only in the most recent deposits were there remains of forms still living.... Another important conclusion reached, mainly through the labors of Lyell, was, that the earth had not been subjected in the past to sudden and violent revolutions; but the great changes wrought had been gradual, differing in no essential respect from those still in progress. Strangely enough, the corollary to this proposition, that life, too, had been continuous on the earth, formed at that date no part of the common stock of knowledge. In the physical world, the great law of ‘correlation of forces’ had been announced, and widely accepted; but in the organic world, the dogma of the miraculous creation of each separate species still held sway.”

_Evolutionary Period._—This period begins with 1860 and the publication of Darwin’s Origin of Species (late in 1859). It is the period of modern paleontology, and is dominated by the belief that universal laws pervade not only inorganic matter, but all life as well. Louis Agassiz had been in America fourteen years when Darwin’s book appeared, and his wonderful influence in bringing the zoology of our country to a high stand and the further influence he exerted through his students was bound to react beneficially on invertebrate paleontology. Shortly after the beginning of this period, or in 1867, Alpheus Hyatt, one of Agassiz’s students, began to apply the study of embryology to fossil cephalopods, showing clearly that these shells retain a great deal of their growth stages or ontogeny. This method of study was then followed by R. T. Jackson, C. E. Beecher, and J. P. Smith, and has been productive of natural classifications of the Cephalopoda, Brachiopoda, Trilobita, and Echinoidea.

The dominant invertebrate paleontologist of this period was of course James Hall, who described about 5000 species of American Paleozoic fossils. He also built up the New York State Museum, while around his private collections of fossils have been developed the American Museum of Natural History in New York City and the Walker Museum at the University of Chicago. In his most important laboratory of paleontology at Albany, there have been trained either wholly or in part the following paleontologists: F. B. Meek, C. A. White, R. P. Whitfield, C. D. Walcott, C. E. Beecher, John M. Clarke, and Charles Schuchert.

In Canada, through the work of the Geological Survey of the Dominion, came the paleontologists Elkanah Billings and, later on, J. F. Whiteaves. The “father of Canadian paleontology,” Sir William Dawson, who developed independently, was active in all branches of the science and did much to unravel the geology of eastern Canada. No organism has been more discussed and more often rejected and accepted as a fossil than his “dawn animal of Canada,” _Eozoon canadense_, first described in 1865. His son, George M. Dawson, was one of the directors of the Geological Survey of Canada. Finally the extensive paleontology of the Cambrian of Canada was worked out by another self-made paleontologist, G. F. Matthew.

_Paleobotany._—American paleobotany was developed during this, the fourth period, through the state and national surveys, first in Leo Lesquereux, a Swiss student induced by Agassiz to come to America, and in J. S. Newberry. The second generation of paleobotanists is represented by Lester F. Ward and W. N. Fontaine, and the third generation, the present workers, includes F. H. Knowlton, David White, Arthur Hollick, and E. W. Berry. A new line of paleobotanical work, the histology of woody but pseudomorphous remains, has been developed by G. R. Wieland.

The grander results of the study of paleontology during the evolutionary period may be summed up with the conclusions of Marsh:

“One of the main characteristics of this epoch is the belief that all life, living and extinct, has been evolved from simple forms. Another prominent feature is the accepted fact of the great antiquity of the human race. These are quite sufficient to distinguish this period sharply from those that preceded it.”

Charles Darwin’s work at once aroused attention, and brought about in scientific thought a revolution which “has influenced paleontology as extensively as any other department of science.... In the [previous period] species were represented independently by parallel lines; in the present period, they are indicated by dependent, branching lines. The former was the analytic, the latter is the synthetic period.”

_Synthetic Period._—What is to be the next trend in paleontology? Clearly it is to be the Synthetic period, one that Marsh in 1879 indicated in these words: “But if we are permitted to continue in imagination the rapidly converging lines of research pursued to-day, they seem to meet at the point where organic and inorganic nature become one. That this point will yet be reached, I cannot doubt.”

This Synthetic period, foreshadowed also in Herbert Spencer’s Synthetic Philosophy, has not yet arrived, but before long another great leader will appear. We have the prophecy of his coming in such books as The Fitness of the Environment, by Lawrence J. Henderson, 1913; The Origin and Nature of Life, by Benjamin Moore, 1913; The Organism as a Whole, by Jacques Loeb, 1916; and The Origin and Evolution of Life, by Henry F. Osborn, 1917.

In all nature, inorganic and organic, there is continuity and consistency, beauty and design. We are beginning to see that there are eternal laws, ever interacting and resulting in progressive and regressive evolutions. The realization of these scientific revelations kindles in us a desire for more knowledge, and the grandest revelations are yet before us in the synthesis of the sciences.

_Notes._

Footnote 3:

For more detail in regard to these tillites and the older ones see Climates of Geologic Time, by Charles Schuchert, being Chapter XXI in Huntington’s Climatic Factor as Illustrated in Arid America, Publication No. 192 of the Carnegie Institution of Washington, 1914. Also Arthur P. Coleman’s presidential address before the Geological Society of America in 1915, Dry Land in Geology, published in the Society’s Bulletin, 27, 175, 1916.

III A CENTURY OF GEOLOGY.—STEPS OF PROGRESS IN THE INTERPRETATION OF LAND FORMS

By HERBERT E. GREGORY

The essence of physiography is the belief that land forms represent merely a stage in the orderly development of the earth’s surface features; that the various dynamic agents perform their characteristic work throughout all geologic time. The formulation of principle and processes of earth sculpture was, therefore, impossible on the hypothesis of a ready-made earth whose features were substantially unchangeable, except when modified by catastrophic processes. In 1821, J. W. Wilson wrote in the Journal: “Is it not the best theory of the earth, that the Creator, in the beginning, at least at the general deluge, formed it with all its present grand characteristic features?”[4] If so, a search for causes is futile, and the study of the work performed by streams and glaciers and wind is unprofitable. The belief in the Deluge as the one great geological event in the history of the earth has brought it about that the speculations of Aristotle, Herodotus, Strabo, and Ovid, and the illustrious Arab, Avicenna (980–1037), unchecked by appeal to facts but also unopposed by priesthood or popular prejudice, are nearer to the truth than the intolerant controversial writings of the intellectual leaders whose touchstone was orthodoxy. A few thinkers of the sixteenth century revolted against the interminable repetition of error, and Peter Severinus (1571) advised his students: “Burn up your books ... buy yourselves stout shoes, get away to the mountains, search the valleys, the deserts, the shores of the seas.... In this way and no other will you arrive at a knowledge of things.” But the thoroughgoing “diluvialist” who believed that a million species of animals could occupy a 450–foot Ark, but not that pebbles weathered from rock or that rivers erode, had no use for his powers of observation.

Sporadic germs of a science of land forms scattered through the literature of the seventeenth and eighteenth centuries found an unfavorable environment and produced inconspicuous growths. Even their sponsors did little to cultivate them. Steno (1631–1687) mildly suggested that surface sculpturing, particularly on a small scale, is largely the work of running water, and Guettard (1715–1786), a truly great mind, grasped the fundamental principles of denudation and successfully entombed his views as well as his reputation in scores of books and volumes of cumbrous diffuse writing.

At the beginning of the nineteenth century a sufficient body of principles had been established to justify the recognition of an earth science, geology, and the 195 volumes of the Journal thus far published carry a large part of the material which has won approval for the new science and given prominence to American thought. From the pages in the Journal, the progress of geology may be illustrated by tracing the fluctuation in the development of fact and theory as relates to valleys and glacial features, the subjects to which this chapter is devoted.

_The Interpretation of Valleys._

_The Pioneers._

Desmarest (1725–1815) might be styled the father of physiography. By concrete examples and sound induction he established (1774) the doctrine that the valleys of central France are formed by the streams which occupy them. He also made the first attempt to trace the history of a landscape through its successive stages on the basis of known causes. His methods and reasoning are practically identical with those of Dutton working in the ancient lavas of New Mexico; and Whitney’s description of the Table Mountains of California might well have appeared in Desmarest’s memoirs.[5] The teachings of Desmarest were strengthened and expanded by DeSaussure (1740–1799), the sponsor for the term, “Geology,” (1779) who saw in the intimate relation of Alpine streams and valleys the evidence of erosion by running water (1786).

The work of these acknowledged leaders of geological thought attracted singularly little attention on the Continent, and Lamarck’s volume on denudation (Hydrogéologie), which appeared in 1802, although an important contribution, sank out of sight. But the seed of the French school found fertile ground in Edinburgh, the center of the geological world during the first quarter of the nineteenth century. Hutton’s “Theory of the Earth, with Proofs and Illustrations,” in which the guidance of DeSaussure and Desmarest is gratefully acknowledged, appeared in 1795. The original publication aroused only local interest, but when placed in attractive form by Playfair’s “Illustrations of the Huttonian Theory” (1802), the problem of the origin and development of land forms assumed a commanding position in geological thought. Hutton was peculiarly fortunate in his environment. He had the support and assistance of a group of able scientific colleagues as well as the bitter opposition of Jameson and of the defenders of orthodoxy. His views were discussed in scientific publications and found their way to literary and theological journals. Hutton’s conception of the processes of land sculpture—slow upheaving and slow degradation of mountains, differential weathering, and the carving of valleys by streams—has a very modern aspect. Playfair’s book would scarcely be out of place in a twentieth century class room. The following paragraphs are quoted from it:[6]

“... A river, of which the course is both serpentine and deeply excavated in the rock, is among the phenomena, by which the slow waste of the land, and also the cause of that waste, are most directly pointed out.

The structure of the vallies among mountains, shews clearly to what cause their existence is to be ascribed. Here we have first a large valley, communicating directly with the plain, and winding between high ridges of mountains, while the river in the bottom of it descends over a surface, remarkable, in such a scene, for its uniform declivity. Into this, open a multitude of transverse or secondary vallies, intersecting the ridges on either side of the former, each bringing a contribution to the main stream, proportioned to its magnitude; and, except where a cataract now and then intervenes, all having that nice adjustment in their levels, which is the more wonderful, the greater the irregularity of the surface. These secondary vallies have others of a smaller size opening into them; and, among mountains of the first order, where all is laid out on the greatest scale, these ramifications are continued to a fourth, and even a fifth, each diminishing in size as it increases in elevation, and as its supply of water is less. Through them all, this law is in general observed, that where a higher valley joins a lower one, of the two angles which it makes with the latter, that which is obtuse is always on the descending side; ... what else but the water itself, working its way through obstacles of unequal resistance, could have opened or kept up a communication between the inequalities of an irregular and alpine surface....

... The probability of such a constitution [arrangement of valleys] having arisen from another cause, is, to the probability of its having arisen from the running of water, in such a proportion as unity bears to a number infinitely great.

... With Dr. Hutton, we shall be disposed to consider those great chains of mountains, which traverse the surface of the globe, as cut out of masses vastly greater, and more lofty than any thing that now remains.

From this gradual change of lakes into rivers, it follows, that a lake is but a temporary and accidental condition of a river, which is every day approaching to its termination; and the truth of this is attested, not only by the lakes that have existed, but also by those that continue to exist.”

_Steps Backward._

Even Hutton’s clear reasoning, firmly buttressed by concrete examples, was insufficient to overcome the belief in ready-made or violently formed valleys and original corrugations and irregularities of mountain surface. The pages of the Journal show that the principles laid down by Playfair were too far in advance of the times to secure general acceptance. In the first volume of the Journal, the gorge of the French Broad River is assigned by Kain to “some dreadful commotion in nature which probably shook these mountains to their bases,”[7] and the gorge of the lower Connecticut is considered by Hitchcock (1824)[8] as a breach which drained a series of lakes “not many centuries before the settlement of this country.” The prevailing American and English view for the first quarter of the nineteenth century is expressed in the reviews in this Journal, where the well-known conclusions of Conybeare and Phillips that streams are incompetent to excavate valleys are quoted with approval and admiration is expressed for Buckland’s famous “Reliquiæ Diluvianæ,” a 300–page quarto volume devoted to proof of a deluge. The professor at Yale, Silliman, and the professor at Oxford, Buckland, saw that an acceptance of Hutton’s views involved a repudiation of the Biblical flood, and much space is devoted to combating these “erroneous” and “unscientific” views. For example, Buckland says:[9]

“... The general belief is, that existing streams, avalanches and lakes, bursting their barriers, are sufficient to account for all their phenomena, and not a few geologists, especially those of the Huttonian school, at whose head is Professor Playfair, have till recently been of this opinion.... But it is now very clear to almost every man, who impartially examines the facts in regard to existing vallies, that the causes now in action, mentioned above, are altogether inadequate to their production; nay, that such a supposition would involve a physical impossibility. We do not believe that one-thousandth part of our present vallies were excavated by the power of existing streams.... In very many cases of large rivers, it is found, that so far from having formed their own beds, they are actually in a gradual manner filling them up.

Again; how happens it that the source of a river is frequently below the head of a valley, if the river excavated that valley?

The most powerful argument, however, in our opinion, against the supposition we are combating, is the phenomena of transverse and longitudinal valleys; both of which could not possibly have been formed by existing streams.”

Phillips writes in 1829:[10] “The excavation of valleys can be ascribed to no other cause than a great flood of water which overtopped the hills, whose summits those vallies descend.”

Faith in Noah’s flood as the dominant agent of erosion rapidly lost ground through the teaching of Lyell after 1830, but the theory of systematic development of landscapes by rivers gained little. In fact, Scrope in 1830,[11] in showing that the entrenched meanders of the Moselle prove gradual progressive stream work, was in advance of his English contemporary. Judged by contributions to the Journal, Lyell’s teaching served to standardize American opinion of earth sculpture somewhat as follows: The ocean is the great valley maker, but rivers also make them; the position of valleys is determined by original or renewed surface inequalities or by faulting; exceptional occurrences—earthquakes, bursting of lakes, upheavals and depressions—have played an important part. Hayes (1839)[12] thought that the surface of New York was essentially an upraised sea-bottom modified by erosion of waves and ocean currents. Sedgwick (1838)[13] considered high-lying lake basins proof of valleys which were shaped under the sea. Many of the valleys in the Chilian Cordillera were thought by Darwin (1844) to have been the work of waves and tides, and water gaps are ascribed to currents “bursting through the range at those points where the strata have been least inclined and the height consequently is less.” Speaking of the magnificent stream-cut canyons of the Blue Mountains of New South Wales, gorges which lead to narrow exits through monoclines, Darwin says: “To attribute these hollows to alluvial action would be preposterous.”[14]

The influence of structure in the formation of valleys is emphasized by many contributors to the Journal. Hildreth in 1836, in a valuable paper,[15] which is perhaps the first detailed topographic description of drainage in folded strata, expresses the opinion that the West Virginia ridges and valleys antedated the streams and that water gaps though cut by rivers involve pre-existing lakes. Geddes (1826)[16] denied that Niagara River cut its channel and speaks of valleys which “were valleys e’er moving spirit bade the waters flow.” Conrad (1839)[17] discussed the structural control of the Mohawk, the Ohio, and the Mississippi, and Lieutenant Warren (1859)[18] concluded that the Niobrara must have originated in a fissure. According to Lesley (1862)[19] the course of the New River across the Great Valley and into the Appalachians “striking the escarpment in the face” is determined by the junction of anticlinal structures on the north with faulted monoclines toward the south; a conclusion in harmony with the views of Edward Hitchcock (1841)[17] that major valleys and mountain passes are structural in origin and that even subordinate folds and faults may determine minor features. “Is not this a beautiful example of prospective benevolence on the part of the Deity, thus, by means of a violent fracture of primary mountains, to provide for easy intercommunication through alpine regions, countless ages afterwards!” The extent of the wandering from the guidance of DeSaussure and Playfair after the lapse of 50 years is shown by students of Switzerland. Alpine valleys to Murchison (1851) were bays of an ancient sea; Schlaginweit (1852) found regional and local complicated crustal movements a satisfactory cause, and Forbes (1863) saw only glaciers.

_Valleys Formed by Rivers._

One strong voice before 1860 appears to have called Americans back to truths expounded by Desmarest and Hutton. Dana in 1850[20] amply demonstrated that valleys on the Pacific Islands owe neither their origin, position or form to the sea or to structural factors. They are the work of existing streams which have eaten their way headwards. Even the valleys of Australia cited by Darwin as type examples of ocean work are shown to be products of normal stream work. Dana went further and gave a permanent place to the Huttonian idea that many bays, inlets, and fiords are but the drowned mouths of stream-made valleys. In the same volume in which these conclusions appeared, Hubbard (1850)[21] announced that in New Hampshire the “deepest valleys are but valleys of erosion.” The theory that valleys are excavated by streams which occupy them was all but universally accepted after F. V. Hayden’s description[22] of Rocky Mountain gorges (1862) and Newberry’s interpretation of the canyons of Arizona (1862); but the scientific world was poorly prepared for Newberry’s statement:[23]

“Like the great canons of the Colorado, the broad valleys bounded by high and perpendicular walls _belong to a vast system of erosion, and are wholly due to the action of water_.... The first and most plausible explanation of the striking surface features of this region will be to refer them to that embodiment of resistless power—the sword that cuts so many geological knots—volcanic force. The Great Canon of the Colorado would be considered a vast fissure or rent in the earth’s crust, and the abrupt termination of the steps of the table lands as marking lines of displacement. This theory though so plausible, and so entirely adequate to explain all the striking phenomena, lacks a single requisite to acceptance, and that is _truth_.”

With such stupendous examples in mind, the dictum of Hutton seemed reasonable: “there is no spot on which rivers may not formerly have run.”

_Denudation by Rivers._

The general recognition of the competency of streams to form valleys was a necessary prelude to the broader view expressed by Jukes (1862)[24]

“The surfaces of our present lands are as much carved and sculptured surfaces as the medallion carved from the slab, or the statue sculptured from the block. They have been gradually reached by the removal of the rock that once covered them, and are themselves but of transient duration, always slowly wasting from decay.”

Contributions to the Journal between 1850 and 1870 reveal a tendency to accept greater degrees of erosion by rivers, but the necessary end-product of subaërial erosion—a plain—is first clearly defined by Powell in 1875.[25] In formulating his ideas Powell introduced the term “base-level,” which may be called the germ word out of which has grown the “cycle of erosion,” the master key of modern physiographers. The original definition of base-level follows: