Part 23

However, the theory of deluges, whether of ocean or land streams, did not hold the field unopposed. In 1823, Granger, an observer whose contributions to science total only six pages, speaks of the striæ on the shore of Lake Erie as

“having been formed by the powerful and continued attrition of some hard body.... To me, it does not seem possible that water under any circumstances, could have effected it. The flutings in width, depth, and direction, are as regular as if they had been cut out by a grooving plane. This, running water could not effect, nor could its operation have produced that glassy smoothness, which, in many parts, it still retains.”

Hayes and also Conrad expressed similar views in the Journal 16 years later.

The idea that ice was in some way concerned with the transportation of drift has had a curious history. The first unequivocal statement, based on reading and keen observation, was made in the Journal by Dobson in 1826:

“I have had occasion to dig up a great number of bowlders, of red sandstone, and of the conglomerate kind, in erecting a cotton manufactory; and it was not uncommon to find them worn smooth on the under side, as if done by their having been dragged over rocks and gravelly earth, in one steady position. On examination, they exhibit scratches and furrows on the abraded part; and if among the minerals composing the rock, there happened to be pebbles of feldspar, or quartz, (which was not uncommon,) they usually appeared not to be worn so much as the rest of the stone, preserving their more tender parts in a ridge, extending some inches. When several of these pebbles happen to be in one block, the preserved ridges were on the same side of the pebbles, so that it is easy to determine which part of the stone moved forward, in the act of wearing.

These bowlders are found, not only on the surface, but I have discovered them a number of feet deep, in the earth, in the hard compound of clay, sand, and gravel....

I think we cannot account for these appearances, unless we call in the aid of ice along with water, and that they have been worn by being suspended and carried in ice, over rocks and earth, under water.”

In Dobson’s day the hypothesis of “gigantic floods,” “debacles,” “resistless world-wide currents,” was so firmly entrenched that the voice of the observant layman found no hearers, and a letter from Dobson to Hitchcock written in 1837 and containing additional evidence and argument remained unpublished until Murchison, in 1842, paid his respects to the remarkable work of a remarkable man.

“I take leave of the glacial theory in congratulating American science in having possessed the original author of the best glacial theory, though his name had escaped notice; and in recommending to you the terse argument of Peter Dobson, a previous acquaintance with which might have saved volumes of disputation on both sides of the Atlantic.”

Glaciers vs. Icebergs.

The glacial theory makes its way into geological literature with the development of Agassiz (1837) of the views of Venetz (1833) and Charpentier (1834), that the glaciers of the Alps once had greater extent. The bold assumption was made that the surface of Europe as far south as the shores of the Mediterranean and Caspian seas was covered by ice during a period immediately preceding the present. The kernel of the present glacial theory is readily recognizable in these early works, but it is wrapped in a strange husk: it was assumed that the Alps were raised by a great convulsion under the ice and that the erratics slid to their places over the newly made declivities. The publication of the famous “Etudes sur les Glaciers” (1840), remarkable alike for its clarity, its sound inductions, and wealth of illustrations, brought the ideas of Agassiz more into prominence and inaugurated a 30–years’ war with the proponents of currents and icebergs. The outstanding objections to the theory were the requirement of a frigid climate and the demand for glaciers of continental dimensions; very strong objections, indeed, for the time when fossil evidence was not available, the great polar ice sheets were unexplored, and the distinction between till and waterlaid drift had not been established.

The glacial theory was cordially adopted by Buckland (1841) and in part by Lyell in England but viewed with suspicion by Sedgwick, Whewell, and Mantell. In America the response to the new idea was immediate. Hitchcock (1841) concludes an able discussion with the statement: “So remarkably does it solve most of the phenomena of diluvial action, that I am constrained to believe its fundamental principles to be founded in truth.”

The theory formed the chief topic of discussion at the third and fourth meetings of the Association of American Geologists and Naturalists (1842, 1843) under the lead of a committee on drift consisting of Emmons, W. B. Rogers, Vanuxem, Nicollet, Jackson, and J. L. Hayes. The result of these discussions was a curious reaction. Hitchcock complained that he “had been supposed to be an advocate for the unmodified glacial theory, but he had never been a believer in it,” and Jackson spoke for a number of men when he stated:

“This country exhibits no proofs of the glacial theory as taught by Agassiz but on the contrary the general bearing of the facts is against that theory.... Many eminent men incautiously embraced the new theory, which within two or three years from its promulgation, had been found utterly inadequate, and is now abandoned by many of its former supporters.”

Out of this symposium came also the strange contribution of H. D. Rogers (1844), who cast aside the teachings of deduction and observation and returned to the views of the Medievalists.

“If we will conceive, then, a wide expanse of waters, less perhaps than one thousand feet in depth, dislodged from some high northern or circumpolar basin, by a general lifting of that region of perhaps a few hundred feet, and an equal subsidence of the country south, and imagine this whole mass converted by earthquake pulsations of the breadth which such undulations have, into a series of stupendous and rapid-moving waves of translation, helped on by the still more rapid flexures of the floor over which they move, and then advert to the shattering and loosening power of the tremendous jar of the earthquake, we shall have an agent adequate in every way to produce the results we see, to float the northern ice from its moorings, to rip off, assisted with its aid, the outcrops of the hardest strata, to grind up and strew wide their fragments, to scour down the whole rocky floor, and, gathering energy with resistance, to sweep up the slopes and over the highest mountains.”

Because of the prominence of their author, Rogers’s views exerted some influence and seemingly received support from England through the elaborate mathematic discussions of Whewell (1848), who considered the drift as “irresistible proof of paroxysmal action,” and Hopkins (1852), who contended for “currents produced by repeated elevatory movements.”

After his arrival in America (1846), Agassiz’s influence was felt, and his paper on the erratic phenomena about Lake Superior (1850), in which he called upon the advocates of water-borne ice to point out the barrier which caused the current to subside, produced a salutary effect; yet Desor (1852) states that in the region described by Agassiz “the assumption [of a general ice cap] is no longer admissible,” and that the bowlders on Long Island “were transported on ice rafts along the sea shore and stranded on the ridges and eminences which were then shoals along the coast.” Twenty years of discussion were insufficient to establish the glacial theory either in Europe or America. The consensus of opinion among the more advanced thinkers in 1860 is expressed by Dana:

“In view of the whole subject, it appears reasonable to conclude that the Glacier theory affords the best and fullest explanation of the phenomena over the general surface of the continents, and encounters the fewest difficulties. But icebergs have aided beyond doubt in producing the results along the borders of the continents, across ocean-channels like the German Ocean and the Baltic, and possibly over great lakes like those of North America. Long Island Sound is so narrow that a glacier may have stretched across it.”

Papers in the Journal of 1860–70 show a prevailing belief in icebergs, but the evidence for land ice was accumulating as the deposits became better known, and in 1871 field workers speak in unmistakable tones:

“It is still a mooted question in American geology whether the events of the Glacial era were due to glaciers or icebergs.... American geologists are still divided in opinion, and some of the most eminent have pronounced in favor of icebergs.

Since, then, icebergs cannot pick up masses tons in weight from the bottom of a sea, or give a general movement southward to the loose material of the surface; neither can produce the abrasion observed over the rocks under its various conditions; and inasmuch as all direct evidence of the submergence of the land required for an iceberg sea over New England fails, the conclusion appears inevitable that icebergs had nothing to do with the drift of the New Haven region, in the Connecticut valley; and, therefore, that the Glacial era in central New England was a Glacier era.”

Matthew (1871) reached the same conclusion for the Lower Provinces of Canada. In spite of the increasing clarity of the evidence, the battle for the glacial theory was not yet won. The remaining opponents though few in number were distinguished in attainments. Dawson clung to the outworn doctrine until his death in 1899.

An interesting feature of the history of glacial theories is the calculation by Maclaren (1842) that the amount of water abstracted from the seas to form the hypothetical ice sheet would lower the ocean level 350 feet—an early form of the glacial control hypothesis (see Daly).

Extent of Glacial Drift.

By the middle of the nineteenth century, it was recognized that the “drift,” whatever its origin, was not of world-wide extent. In America its characteristic features were found best developed north of latitude 40 degrees; in Europe, the Alps, the Scottish Highlands, and Scandinavia were recognized as type areas. The limits were unassigned, partly because the field had not been surveyed, but largely because criteria for the recognition of drift had not been established. The well-known hillocks and ridges of “diluvium” and “alluvium” and “drift” of New Jersey and Ohio, and the mounds of the Missouri Cotou elaborately described by Catlin (1840) bore little resemblance to the walls of unsorted rock which stand as moraines bordering Alpine glaciers. The Orange sand of Mississippi was included in the drift by Hilgard (1866), and the gravels at Philadelphia by Hall (1876). Stevens (1873) described trains of glacial erratics at Richmond, Virginia, and William B. Rogers (1876) accounts for certain deposits in the Potomac, James, and Roanoke rivers by the presence of Pleistocene ice tongues or swollen glacial rivers, and remarks: “It is highly probable that glacial action had much to do with the original accumulation of the rocky debris on the flanks of the Blue Ridge, and in the Appalachian valleys beyond.” Kerr (1881) referred the ancient erosion surface of the Piedmont belt in North Carolina to glacial denudation, De la Beche compared the drift of Jamaica with that of New England, and Agassiz interpreted soils of Brazil as glacial.

The first detailed description and unequivocal interpretation of either terminal or recessional moraines is from the pen of Gilbert (1871), geologist of the Ohio Survey. In discussing the former outlet of Lake Erie through the Fort Wayne channel, Gilbert writes:

“The page of history recorded in these phenomena is by no means ambiguous. The ridges, or, more properly, the ridge which determines the courses of the St. Joseph and St. Marys rivers is a buried terminal moraine of the glacier that moved southwestward through the Maumee valley. The overlying Erie Clay covers it from sight, but it is shadowed forth on the surface of that deposit, as the ground is pictured through a deep and even canopy of snow. Its irregularly curved outline accords intimately with the configuration of the valley, and with the direction of the ice markings; its concavity is turned toward the source of motion; its greatest convexity is along the line of least resistance.