Chapter XII: A Century of Zoology in America. Wesley R. Coe 391 (6)

“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hearers, and a letter from Dobson to Hitchcock written in 1837 and containing additional evidence and argument remained unpublished until Murchison, in 1842,[43] paid his respects to the remarkable work of a remarkable man.[44]

“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)[45] 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)[46] 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:[47]

“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),[48] 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),[49] 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)[50] 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:[51]

“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:[52]

“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)[53] 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)[54] 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[55]).

_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)[56] 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),[57] and the gravels at Philadelphia by Hall (1876).[58] Stevens (1873)[59] described trains of glacial erratics at Richmond, Virginia, and William B. Rogers (1876)[60] 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)[61] 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),[62] 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.

South of the St. Marys river are other and numerous moraines
accompanied by glacial striæ. Their character and courses have not yet
been studied; but their presence carries the mind back to an epoch of
the cold period, when the margin of the icefield was farther south,
and the glacier of the Maumee valley was merged in the general mass.
As the mantle of ice grew shorter—and, in fact, at every stage of its
existence—its margin must have been variously notched and lobed in
conformity with the contour of the country, the higher lands being
first laid bare by the encroaching secular summer. Early in the
history of this encroachment the glacier of the Maumee valley
constituted one of these lobes, and has recorded its form in the two
moraines that I have described.”

Three years after the recognition of moraines in the Maumee valley, Chamberlin (1874)[63] showed that the seemingly disorganized mounds and basins and ridges known as the Kettle range of Wisconsin is the terminal moraine of the Green Bay glacier. At an earlier date (1864) Whittlesey interpreted the kettles of the Wisconsin moraine as evidence of ice blocks from a melting glacier and presented a map showing the “southern limit of boulders and coarse drift.” In 1876 attention was called to the terminal moraine of New England by G. Frederick Wright, who assigns the honor of discovery to Clarence King.

With the observations of Gilbert, Chamberlin, and King in mind, the terminal moraine was traced by various workers across the United States and into Canada and the extent of glacial cover revealed. Following 1875 the pages of the Journal contain many contributions dealing with the origin and structure of moraines, eskers, kames, and drumlins. Before 1890 twenty-eight papers on the glacial phenomena of the Erie and Ohio basin alone had appeared. By 1900 substantial agreement had been reached regarding the significant features of the drift, the outline history of the Great Lakes had been written, and the way had been paved for stratigraphic studies of the Pleistocene, which bulk large in the pages of the Journal for the last two decades.

_Epochs of Glaciation._

For a decade following the general acceptance of the glacial origin of “diluvium,” the deposits were embraced as “drift” and treated as the products of one long period of glacial activity, and throughout the controversy of iceberg and glacier the unity of the glacial period was unquestioned. Beds of peat and fossiliferous lacustrine deposits in Switzerland, England, and in America and the recognition of an “upper” and a “lower” diluvium by Scandinavian geologists suggested two epochs, and as the examples of such deposits increased in number and it became evident that the plant fossils represented forms demanding a genial climate and that the phenomena were seen in many countries, the belief grew that minor fluctuations or gradual recession of an ice sheet were inadequate to account for the phenomena observed.

It is natural that this problem should have found its solution in America, where the Pleistocene is admirably displayed, and where the State and Federal surveys were actively engaged in areal mapping. In 1883 Chamberlin[64] presented his views under the bold title, “Preliminary Paper on the Terminal Moraine of the Second Glacial Epoch,” and the existence of deposits of two or more ice sheets and the features of interglacial periods were substantially established by the interesting debate in the Journal led by Chamberlin, Wright, Upham and Dana.[65] Contributions since 1895 have been concerned with the degree rather than the fact of complexity, and continued study has resulted in the general recognition of five glacial stages in North America and four in Europe.

_The Loess as a Glacial Deposit._

A curious side-product of the study of glaciation in North America is the controversy over the origin of loess. The interest aroused is indicated by scores of papers in American periodicals and State reports of the last quarter of the 19th century—papers which bear the names of prominent geologists.

The “loess” in the valley of the Rhine had long been known, but the subject assumed prominence by the publication in 1866 of Pumpelly’s Travels in China.[66] Wide-spread deposits 200 to 1,000 feet thick were described as very fine-grained yellowish earth of distinctive structure without stratification but penetrated by innumerable tubes and containing land or fresh-water shells. Pumpelly considered these deposits lacustrine, a view which found general acceptance though combated by Kingsmill (1871),[67] who argued for marine deposition. Baron Von Richthofen’s classic on China, which appeared in 1877, amplifies the observations of Pumpelly and marshals the evidence to support the hypothesis that the loess is wind-laid both on dry land and within ancient salt lakes. The conclusions of Von Richthofen were adopted by Pumpelly whose knowledge of the Chinese deposits, supplemented by studies in Missouri, of which State he was director of the Geological Survey in 1872–73, placed him in position to form a correct judgment. He says:[68]

“Recognizing from personal observation the full identity of character
of the loess of northern China, Europe and the Missouri Valley, I am
obliged to reject my own explanation of the origin of the Chinese
deposits, and to believe with Richthofen that the true loess, wherever
it occurs, is a sub-aerial deposit, formed in a dry central region,
and that it owes its structure to the formative influence of a steppe
vegetation.

The one weak point of Richthofen’s theory is in the evident inadequacy
of the current disintegration as a source of material. When we
consider the immense area covered by loess to depths varying from 50
to 2,000 feet, and the fact that this is only the very finest portion
of the product of rock-destruction, and again that the accumulation
represents only a very short period of time, geologically speaking,
surely we must seek a more fertile source of supply than is furnished
by the current decomposition of rock surface.

It seems to me that there are two important sources: I. The silt
brought by rivers, many of them fed by the products of glacial
attrition flowing from the mountains into the central region. Where
the streams sink away, or where the lakes which receive them have
dried up, the finer products of the erosion of a large territory are
left to be removed in dust storms.

II. The second ... source is the residuary products of a secular
disintegration.”

The evidence presented by Pumpelly for the eolian origin of loess—structure, texture, composition, fossil content and topographic position—is complete, and to him belongs the credit for the correct interpretation of the Mississippi valley deposits. Unfortunately his contribution came at a time when the geologists of the central States were intent on tracing the paths and explaining the work of Pleistocene glaciers, and the belief was strong that loess was some phase of glacial work. Its position at the border of the Iowan drift so obviously suggests a genetic relation that the fossil evidence of steppe climate suggested by Binney in 1848[69] was minimized. Students of Pleistocene geology in Minnesota, Iowa, Nebraska, Missouri, although less vigorous in expression, were substantially in agreement with Hilgard (1879).[70] “The sum total of anomalous conditions required to sustain the eolian hypothesis partakes strongly of the marvellous.” The last edition of Dana’s Manual, 1894, and of LeConte’s Geology, 1896, the two most widely used text-books of their time, oppose the eolian theory, and Chamberlin, in 1897,[71] states: “the aqueous hypothesis seems best supported so far as concerns the deposits of the Mississippi Valley and western Europe” (p. 795). Shimek, in papers published since 1896 has shown that aquatic and glacial conditions can not account for the loess fossils, and the return to the views of Pumpelly that the loess was deposited on land by the agency of wind in a region of steppe vegetation is now all but universal.

_Glacial Sculpture._

Within the present generation sculpture by glaciers has received much attention and has involved a reconsideration of the ability of ice to erode which in turn involves a crystallization of views of the mechanics of moving ice. The evidence for glacier erosion has remained largely physiographic and rests on a study of land forms. In fact, the inadequacy of structural features or of river corrasion to account for flat-floored, steep-walled gorges, hanging valleys, and many lake basins, rather than a knowledge of the mechanics of ice has led to the present fairly general belief that glaciers are powerful agents of rock sculpture. The details of the process are not yet understood.

Erosion by glaciers enters the arena of active discussion in 1862–63. The possibility had been suggested by Esmark (1827) and by Dana (1849) in the description of fiords and by Hind (1855) with reference to the origin of the Great Lakes. It appears full-fledged in Ramsay’s classic, which was published simultaneously in England and in America.[72] The argument runs as follows: There is a close association of ancient glaciers and lakes especially in mountains; glaciers are amply able to erode; evidences of faulting, special subsidence, river erosion, and marine erosion are absent from the lake basins of Switzerland and Great Britain. To quote Ramsay:

“It required a solid body grinding steadily and powerfully in direct
and heavy contact with and across the rocks to scoop out deep hollows,
the situations of which might either be determined by unequal hardness
of the rocks, by extra weight of ice in special places, or by
accidental circumstances, the clue to which is lost from our inability
perfectly to reconstruct the original forms of the glaciers.”

“I believe with the Italian geologists, that all that the glaciers as
a whole effected was only slightly to deepen these valleys and
materially to modify their general outlines, and, further (a theory I
am alone responsible for), to deepen them in parts more considerably
when, from various causes, the grinding power of the ice was unusually
powerful, especially where, as in the lowlands of Switzerland, the
Miocene strata are comparatively soft.”

Whittlesey (1864)[73] considered that the rock-bound lakes and narrow bays near Lake Superior were partly excavated by ice. LeConte (1875)[74] records some significant observations in a pioneer paper on glacier erosion which has not received adequate recognition. He says:

“... I am convinced that a glacier, by its enormous pressure and
resistless onward movement, is _constantly breaking off large blocks_
from its bed and bounding walls. Its erosion is not only a grinding
and scoring, but also a _crushing and breaking_. It makes by its
erosion not only rock-meal, but also large _rock-chips_.... Its
erosion is a constant process of alternate _rough hewing_ and
_planing_.

If Yosemite were unique, we might suppose that it was formed by
violent cataclysms; but _Yosemite is not unique_ in _form_ and
therefore probably not in _origin_. There are many Yosemites. It is
more philosophical to account for them by the _regular_ operation of
known causes. I must believe that all these deep perpendicular slots
have been sawn out by the action of glaciers; the _peculiar
verticality of the walls having been determined by the perpendicular
cleavage structure_.”... A lake in Bloody Canyon “is a _pure rock
basin scooped out by the glacier_ at this place.... These ridges
[separating Hope, Faith, and Charity valleys] are in fact the lips of
consecutive lake basins scooped out by ice.

... Water tends to form deep V-shaped canons, while ice produces broad
valleys with lakes and meadows.... I know not how general these
distinctions may be, but certainly the Coast range of this State is
characterized by rounded summits and ridges, and deep V-shaped canons,
while the high Sierras are characterized on the contrary by sharp,
spire-like, comb-like summits, and broad valleys; and this difference
I am convinced is due in part at least to the action of water on the
one hand, and of ice on the other.”

King (1878)[75] assigned to glacial erosion a commanding position in mountain sculpture. In regard to the Uintas, he says:

“Glacial erosion has cut almost vertically down through the beds
carving immense amphitheatres with basin bottoms containing numerous
Alpine lakes.... Post-glacial erosion has done an absolutely trivial
work. There is not a particle of direct evidence, so far as I can see,
to warrant the belief that these U-shaped canons were given their
peculiar form by other means than the actual ploughing erosion of
glaciers....”

These contributions from the Cordilleras corroborating the conclusions of Ramsay (1862), Tyndall (1862), Jukes (1862), Hector (1863), Logan (1863), Close (1870), and James Geikie (1875), made little impression. The views of Lyell (1833), Ball (1863), J. W. Dawson (1864), Falconer (1864), Studer (1864), Murchison (1864, 1870), Ruskin (1865), Rutimeyer (1869), Whymper (1871), Bonney (1873), Pfaff (1874), Gurlt (1874), Judd (1876), prevailed, and the conclusions of Davis in 1882[76] fairly expressed the prevailing belief in Europe and in America:

“The amount of glacial erosion in the central districts has been very
considerable, but not greatly in excess of pre-glacial soils and old
talus and alluvial deposits. Most of the solid rock that was carried
away came from ledges rather than from valleys; and glaciers had in
general a smoothing rather than a roughening effect. In the outer
areas on which the ice advanced it only rubbed down the projecting
points; here it acted more frequently as a depositing than as an
eroding agent.”

During the past quarter-century the cleavage in the ranks of geologists, brought about by Ramsay’s classic paper, has remained. Fairchild and others in America, Heim, Bonney, and Garwood in Europe argue for insignificant erosion by glaciers; and Gannet, Davis, Gilbert, Tarr in America followed by Austrian workers present evidence for erosion on a gigantic scale. A perusal of the voluminous literature in the Journal and elsewhere shows that the difference of opinion is in part one of terms, the amount of erosion rather than the fact of erosion; it also arises from failure to differentiate the work of mountain glaciers and continental ice sheets, of Pleistocene glaciers and their present diminished representatives. The irrelevant contribution of physicists has also made for confusion.

It is interesting to note that the criteria for erosion of valleys by glaciers has long been established and by workers in different countries. Ramsay (1862) in England outlined the problem and presented generalized evidence. Hector (1863) in New Zealand pointed out the significance of discordant drainage, the “hanging valleys” of Gilbert. The U-form, the broad lake-dotted floor, and the presence of cirques and the process of plucking were probably first described by LeConte (1873) in America. The truncation of valley spurs by glaciers pointed out by Studer in the Kerguelen Islands (1878) was used by Chamberlin (1883) as evidence of glacial scouring.

_Conclusion._

During the past century many principles of land sculpture have emerged from the fog of intellectual speculation and unorganized observation and taken their place among generally accepted truths. Many of them are no longer subjects of controversy. Erosion has found its place as a major geologic agent and has given a new conception of natural scenery. Lofty mountains are no longer “ancient as the sun,” they are youthful features in process of dissection; valleys and canyons are the work of streams and glaciers; fiords are erosion forms; waterfalls and lakes are features in process of elimination; many plains and plateaus owe their form and position to long-continued denudation. Modern landscapes are no longer viewed as original features or the product of a single agent acting at a particular time, but as ephemeral forms which owe their present appearance to their age and the particular forces at work upon them as well as to their original structure.

It is interesting to note the halting steps leading to the present viewpoint, to find that decades elapsed between the formulation of a theory or the recording of significant facts and their final acceptance or rejection, and to realize that the organization of principles and observations into a science of physiography has been the work of the present generation. Progress has been conditioned by a number of factors besides the intellectual ability of individual workers.

The influence of locality is plainly seen. Convincing evidence of river erosion was obtained in central France, the Pacific Islands, and the Colorado Plateau—regions in which other causes were easily eliminated. Sculpture by glaciers passed beyond the theoretical stage when the simple forms of the Sierras and New Zealand Alps were described. The origin of loess was first discerned in a region where glacial phenomena did not obscure the vision. The complexity of the Glacial period asserted by geologists of the Middle West was denied by eastern students. The work of waves on the English coast impressed British geologists to such an extent that plains of denudation and inland valleys were ascribed to ocean work.

In the establishment of principles, the friendly interchange of ideas has yielded large returns. Many of the fundamental conceptions of earth sculpture have come from groups of men so situated as to facilitate criticism. It is impossible, even if desirable, to award individual credit to Venetz, Charpentier, and Agassiz in the formulation of the glacial theory; and the close association of Agassiz and Dana in New England and of Chamberlin and Irving in Wisconsin was undoubtedly helpful in establishing the theory of continental glaciation. From the intimate companionship in field and laboratory of Hutton, Playfair and Hope, arose the profound influence of the Edinburgh school, and the sympathetic cooperation of Powell, Gilbert, and Dutton has given to the world its classics in the genetic study of land forms.

The influence of ideas has been closely associated with clarity, conciseness, and attractiveness of presentation. Hutton is known through Playfair, Agassiz’s contributions to glacial geology are known to every student, while Venetz, Charpentier, and Hugi are only names. Cuvier’s discourses on dynamical geology were reprinted and translated into English and German, but Lamarck’s “Hydrogéologie” is known only to book collectors. The verbose works of Guettard, although carrying the same message as Playfair’s “Illustrations” and Desmarest’s “Memoirs,” are practically unknown, as is also Horace H. Hayden’s treatise (1821) on the drift of eastern North America. It has been well said that the world-wide influence of American physiographic teaching is due in no small part to the masterly presentations of Gilbert and Davis.

It is surprising to note the delays, the backward steps, and the duplication of effort resulting from lack of familiarity with the work of the pioneers. Sabine says in 1864:[77]

“It often happens, not unnaturally, that those who are most occupied
with the questions of the day in an advancing science retain but an
imperfect recollection of the obligations due to those who laid the
first foundations of our subsequent knowledge.”

The product of intellectual effort appears to be conditioned by time of planting and character of soil as well as by quantity of seed. For example: Erosion by rivers was as clearly shown by Desmarest as by Dana and Newberry 50 years later. Criteria for the recognition of ancient fluviatile deposits were established by James Deane in 1847 in a study of the Connecticut Valley Triassic. Agassiz’s proof that ice is an essential factor in the formation of till is substantially a duplication of Dobson’s observations (1826).

The volumes of the Journal with their very large number of articles and reviews dealing with geology show that the interpretation of land forms as products of subaërial erosion began in France and French Switzerland during the later part of the eighteenth century as a phase of the intellectual emancipation following the Revolution. Scotland and England assumed the leadership for the first half of the nineteenth century, and the first 100 volumes of the Journal show the profound influence of English and French teaching. In America, independent thinking, early exercised by the few, became general with the establishment of the Federal survey, the increase in university departments, geological societies and periodicals, and has given to Americans the responsibilities of teachers.

_Bibliography._

(In the following list “this Journal” refers to the American Journal of Science.)

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Footnote 5:

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Footnote 6:

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Footnote 7:

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Footnote 8:

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Footnote 9:

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Footnote 10:

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Footnote 11:

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Footnote 12:

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Footnote 13:

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Footnote 14:

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Footnote 15:

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Footnote 16:

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Footnote 18:

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Footnote 19:

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Footnote 17:

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Footnote 20:

Dana, J. D., On denudation in the Pacific, this Journal, =9=, 48–62,
1850.

——, On the degradation of the rocks of New South Wales and formation
of valleys, this Journal, =9=, 289–294, 1850.

Footnote 21:

Hubbard, O. P., On the condition of trap dikes in New Hampshire an
evidence and measure of erosion, this Journal, =9=, 158–171, 1850.

Footnote 22:

Hayden, F. V., Some remarks in regard to the period of elevation of
the Rocky Mountains, this Journal, =33=, 305–313, 1862.

Footnote 23:

Newberry, J. S., Colorado River of the West, this Journal, =33=,
review, 387–403, 1862.

Footnote 24:

Jukes, J. B., Address to the Geological Section of the British
Association at Cambridge, Quart. Jour. Geol. Soc., 18, 1862, this
Journal, =34=, 439, 1862.

Footnote 25:

Powell, J. W., Exploration of the Colorado River of the West, 1875.
For Powell’s preliminary article see this Journal, =5=, 456–465, 1873.

Footnote 26:

McGee, W. J., Three formations of the Middle Atlantic slope, this
Journal, =35=, 120, 328, 367, 448, 1888.

Footnote 27:

Davis, W. M., Topographic development of the Triassic formation of the
Connecticut Valley, this Journal, =37=, 423–434, 1889.

Footnote 28:

Percival, J. G., Geology of Connecticut, 1842.

Footnote 29:

Kerr, W. C., Origin of some new points in the topography of North
Carolina, this Journal, =21=, 216–219, 1881.

Footnote 30:

McGee, W. J., The classification of geographic forms by genesis, Nat.
Geogr. Mag., =1=, 27–36, 1888.

Footnote 31:

Davis, W. M., The rivers and valleys of Pennsylvania, Nat. Geogr.
Mag., =1=, 183–253, 1889.

——, The rivers of northern New Jersey with notes on the classification
of rivers in general, ibid., =2=, 81–110, 1890.

Footnote 32:

Silliman, Benjamin, Notice of Horace H. Hayden’s geological essays,
this Journal, =3=, 49, 1821.

Footnote 33:

Cornelius, Elias, Account of a singular position of a granite rock,
this Journal, =2=, 200–201, 1820.

Footnote 34:

Finch, John, On the Celtic antiquities of America, this Journal, =7=,
149–161, 1824.

Footnote 35:

Finch, John, Geological essay on the Tertiary formations in America,
this Journal, =7=, 31–43, 1824.

Footnote 36:

Conybeare and Phillips, Outlines of the geology of England and Wales,
this Journal, =7=, 210, 211, 1824.

Footnote 37:

Hayden, Horace H., Geological essays, 1–412, 1821, this Journal, =3=,
47–57, 1821.

Footnote 38:

Jackson, C. T., Reports on the geology of the State of Maine, and on
the public lands belonging to Maine and Massachusetts, this Journal,
=36=, 153, 1839.

Footnote 39:

Gibson, J. B., Remarks on the geology of the lakes and the valley of
the Mississippi, this Journal, =29=, 201–213, 1836.

Footnote 40:

Phillips, John, Geology of Yorkshire, this Journal, =21=, 14–15, 1832.

Footnote 41:

Granger, Ebenezer, Notice of a curious fluted rock at Sandusky Bay,
Ohio, this Journal, =6=, 180, 1823.

Footnote 42:

Dobson, Peter, Remarks on bowlders, this Journal, =10=, 217–218, 1826.

Footnote 43:

Murchison, R. I., Address at anniversary meeting of the Geological
Society of London, this Journal, =43=, 200–201, 1842.

Footnote 44:

Peter Dobson (1784–1878) came to this country from Preston, England,
in 1809 and established a cotton factory at Vernon, Conn.

Footnote 45:

Buckland, W., On the evidence of glaciers in Scotland and the north of
England, Proc. London Geol. Soc., =3=, 1841.

Footnote 46:

Hitchcock, Edward, First anniversary address before the Association of
American Geologists, this Journal, =41=, 232–275, 1841.

Footnote 47:

Third annual meeting of the Association of American Geologists and
Naturalists, this Journal, =43=, 154, 1842; Abstract of proceedings of
the fourth session of the Association of American Geologists and
Naturalists, ibid., =45=, 321, 1843.

Footnote 48:

Rogers, H. D., Address delivered before Association of American
Geologists and Naturalists, this Journal, =47=, 275, 1844.

Footnote 49:

Agassiz, Louis, The erratic phenomena about Lake Superior, this
Journal, =10=, 83–101, 1850.

Footnote 50:

Desor, E., On the drift of Lake Superior, this Journal, 13, 93–109,
1852; Post-Pliocene of the southern States, etc., =14=, 49–59, 1852.

Footnote 51:

Dana, J. D., Manual of geology, 546, Philadelphia, 1863.

Footnote 52:

Dana, J. D., on the Quaternary, or post-Tertiary of the New Haven
region, this Journal, =1=, 1–5, 1871.

Footnote 53:

Matthew, G. F., Surface geology of New Brunswick, this Journal, =2=,
371–372, 1871.

Footnote 54:

Maclaren, Charles, The glacial theory of Prof. Agassiz, this Journal,
=42=, 365, 1842.

Footnote 55:

Daly, R. A., Problems of the Pacific Islands, this Journal, =41=,
153–186, 1916.

Footnote 56:

Catlin, George, Account of a journey to the Côteau des Prairies, this
Journal, =38=, 138–146, 1840.

Footnote 57:

Hilgard, E. W., Remarks on the drift of the western and southern
States and its relation to the glacier and iceberg theories, this
Journal, =42=, 343–347, 1866.

Footnote 58:

Hall, C. E., Glacial phenomena along the Kittatinny or Blue Mountain,
Pennsylvania, this Journal, =11=, review, 233, 1876.

Footnote 59:

Stevens, R. P., On glaciers of the glacial era in Virginia, this
Journal, =6=, 371–373, 1873.

Footnote 60:

Rogers, W. B., On the gravel and cobble-stone deposits of Virginia and
the Middle States, Proc. Boston Soc. Nat. Hist., 18, 1875; this
Journal, =11=, 60–61, 1876.

Footnote 61:

Kerr, W. C, Origin of some new points in the topography of North
Carolina, this Journal, =21=, 216–219, 1881.

Footnote 62:

Gilbert, G. K., On certain glacial and post-glacial phenomena of the
Maumee valley, this Journal, =1=, 339–345, 1871.

Footnote 63:

Chamberlin, T. C., On the geology of eastern Wisconsin, Geol. of
Wisconsin, =2=, 1877; this Journal, 15, 61, 406, 1878.

Footnote 64:

Chamberlin, T. C, Preliminary paper on the terminal moraine of the
second glacial epoch, U. S. Geol. Survey, Third Ann. Rept., 291–402,
1883.

Footnote 65:

Wright, G. F., Unity of the glacial epoch, this Journal, =44=,
351–373, 1892.

Upham, Warren, The diversity of the glacial drift along its boundary,
ibid., =47=, 358–365, 1894.

Wright, G. F., Theory of an interglacial submergence in England,
ibid., =43=, 1–8, 1892.

Chamberlin, T. C., Diversity of the glacial period, ibid., =45=,
171–200, 1983

Dana, J. D., On New England and the upper Mississippi basin in the
glacial period, ibid., =46=, 327–330, 1893.

Wright, G. F., Continuity of the glacial period, ibid., =47=, 161–187,
1894.

Chamberlin, T. C. and Leverett, F., Further studies of the drainage
features of the upper Ohio basin, ibid., =47=, 247–282, 1894.

Footnote 66:

Pumpelly, Raphael, Geological researches in China, Japan, and
Mongolia, Smithsonian Contributions, No. 202, 1866.

Footnote 67:

Kingsmill, T. W., The probable origin of “loess” in North China and
eastern Asia, Quart. Jour. Geol. Soc., =27=, No. 108, 1871.

Footnote 68:

Pumpelly, Raphael, The relation of secular rock-disintegration to
loess, glacial drift and rock basins, this Journal, =17=, 135, 1879.

Footnote 69:

Binney, A., Some geologic features at Natchez on the Mississippi
River, Proc. Boston Soc. Nat. Hist., =2=, 126–130, 1848.

Footnote 70:

Hilgard, E. W., The loess of Mississippi Valley, and the eolian
hypothesis, this Journal, =18=, 106–112, 1879.

Footnote 71:

Chamberlin, T. C, Supplementary hypothesis respecting the origin of
the loess of the Mississippi Valley, Jour. Geol., =5=, 795–802, 1897.

Footnote 72:

Ramsay, A. C., On the glacial origin of certain lakes in Switzerland,
the Black Forest, Great Britain, Sweden, North America, and elsewhere,
Quart. Jour. Geol. Soc., 1862; this Journal, =35=, 324–345, 1863.
Preliminary statements of this theory appeared in 1859 and 1860.

Footnote 73:

Whittlesey, Charles, Smithsonian Contributions, No. 197, 1864.

Footnote 74:

LeConte, Joseph, On some of the ancient glaciers of the Sierras, this
Journal, =5=, 325–342, 1873, 10, 126–139, 1875.

Footnote 75:

King, Clarence, U. S. Geol. Expl. 40th Par., 1, 459–529, 1878.

Footnote 76:

Davis, W. M., Glacial erosion, Proc. Boston Soc. Nat. Hist., =22=,
=58=, 1882.

Footnote 77:

Sabine, Sir Edward, Address of the president of the Royal Society,
this Journal, =37=, 108, 1864.

IV
A CENTURY OF GEOLOGY.—THE GROWTH OF KNOWLEDGE OF EARTH STRUCTURE

By JOSEPH BARRELL

_Introduction
The Intellectual Viewpoint in 1818._

In 1818, the year of the founding of the Journal, the natural sciences were still in their infancy in Europe. Geology was still subordinate to mineralogy, was hardly recognized as a distinct science, and consisted in little more than a description of the character and distribution of minerals and rocks. America was remote from the Old World centers of learning. The energy of the young nation was absorbed in its own expansion, and but a few of those who by aptitude were fitted to increase scientific knowledge were even conscious of the existence of such a field of endeavor. Under these circumstances the educative field open to a journal of science in the United States was an almost virgin soil. Original contributions could most readily be based upon the natural history of the New World, and the founder of the Journal showed insight appreciative of the situation in stating in the “Plan of the Work” in the introduction to the first volume that “It will be a leading object to illustrate AMERICAN NATURAL HISTORY, and especially our MINERALOGY and GEOLOGY.”

At this time educated people were still satisfied that the whole knowledge of the origin and development of the earth so far as man could or should know it was embraced in the Book of Genesis. They were inclined to look with misgiving at attempts to directly interrogate the earth as to its history. Philosophers such as Descartes and Liebnitz, the cosmogonists de Maillet and Buffon had been less instrumental in developing science than in fitting a few facts and many speculations to their systems of philosophy. By the opening of the nineteenth century, however, men of learning were coming to appreciate that the way to advance science was to experiment and observe, to collect facts and discourage unfounded speculation. Silliman’s insight into the needs of geologic science is shown in the following quotation (=1=, pp. 6, 7, 1818):

“Our geology, also, presents a most interesting field of inquiry. A
grand outline has recently been drawn by Mr. Maclure, with a masterly
hand, and with a vast extent of personal observation and labour: but
to fill up the detail, both observation and labour still more
extensive are demanded; nor can the object be effected, till more good
geologists are formed, and distributed over our extensive territory.

To account for the formation and changes of our globe, by excursions
of the imagination, often splendid and imposing, but usually
visionary, and almost always baseless, was, till within half a
century, the business of geological speculations; but this research
has now assumed a more sober character; the science of geology has
been reared upon numerous and accurate observations of _facts_; and
standing thus upon the basis of induction, it is entitled to a rank
among those sciences which Lord Bacon’s Philosophy has contributed to
create. Geological researches are now prosecuted by actually exploring
the structure and arrangement of districts, countries, and continents.
The obliquity of the strata of most rocks, causing their edges to
project in many places above the surface; their exposure, in other
instances on the sides or tops of hills and mountains; or, in
consequence of the intersection of their strata, by roads, canals, and
river-courses, or by the wearing of the ocean; or their direct
perforation, by the shafts of mines; all these causes, and others,
afford extensive means of reading the interior structure of the globe.

The outlines of American geology appear to be particularly grand,
simple, and instructive; and a knowledge of the important facts, and
general principles of this science, is of vast practical use, as
regards the interests of agriculture, and the research for useful
minerals. Geological and mineralogical descriptions, and maps of
particular states and districts, are very much needed in the United
States; and to excite a spirit to furnish them will form one leading
object of this Journal.”

_The Prolonged Influence of Outgrown Ideas._

Those interested in any branch of science should, as a matter of education, read the history of that special subject. A knowledge of the stages by which the present development has been attained is essential to give a proper perspective to the literature of each period. Much of the existing terminology is an inheritance from the first attempts at nomenclature, or may rest upon theories long discarded. Popular notions at variance with advanced teaching are often the forgotten inheritance of a past generation.

Gneiss, trap, and Old Red Sandstone are names which we owe to Werner. The “Tertiary period” and “drift” are relics of an early terminology. The geology of tourist circulars still speaks of canyons as made by “convulsions of nature.” Popular writers still attribute to geologists a belief in a molten earth covered by a thin crust. Within the present century the eighteenth century speculations of Werner and his predecessors, postulating a supposed capacity of water to seep through the crust into the interior of the earth, resulting in a hypothetical progressive desiccation of the surface, views long abandoned by most modern geologists, have been revived by an astronomer into a theory of “planetology.”

A review of the literature of a century brings to light certain tendencies in the growth of science. Each decade has witnessed a larger accumulation of observed facts and a fuller classification of these fundamental data, but the pendulum of interpretative theory swings away from the path of progress, now to one side, now to the other, testing out the proper direction. For decades the understanding of certain classes of facts may be actually retrogressive. A retrospect shows that certain minds, keen and unfettered by a prevailing theory, have in some directions been in advance of their generation. But the judgment of the times had not sufficient basis in knowledge for the separation and acceptance of their truer views from the contemporaneous tangle of false interpretations.

An interesting illustration of these statements regarding the slow settling of opinion may be cited in regard to the significance of the dip of the Triassic formations of the eastern United States. The strata of the Massachusetts-Connecticut basin possess a monoclinal easterly dip which averages about 20 degrees to the east. Those of the New Jersey-Pennsylvania-Virginia basin possess a similar dip to the northwest. Both basins are cut by great faults and the dip is now accepted by practically all geologists as due to rotation of the crust blocks away from a geanticlinal axis between the two basins. Edward Hitchcock, whose work from the first shows an interpretative quality in advance of his time, states in 1823 (=6=,74) regarding the dip of the Connecticut valley rocks:

“There is reason to believe that Mount Toby, the strata of which are
almost horizontal, exhibits the original dip of these rocks, and that
those cases in which they are more highly inclined are the result of
some Plutonian convulsion. Such irregularity in the dip of coal fields
is no uncommon occurrence.”

In Hitchcock’s Geology of Massachusetts, published in 1833, ten years later, geological structure sections of the Connecticut Valley rocks are given, the facts are discussed in detail and the dip ascribed to the elevatory forces. He says (l. c., pp. 213, 223):

“If it were possible to doubt that the new red sandstone formation was
deposited from water, the surface of some of the layers of this shale
would settle the question demonstrably. For it exhibits precisely
those gentle undulations, which the loamy bottom of every river with a
moderate current, presents. (No. 198.) But such a surface could never
have been formed while the layers had that high inclination to the
horizon, which many of them now present: so that we have here, also,
decisive evidence that they have been elevated subsequently to their
deposition....

The objection of a writer in the American Journal of Science, that
such a height of waters as would deposit Mount Toby, must have
produced a lake nearly to the upper part of New Hampshire, in the
Connecticut Valley, and thus have caused the same sandstone to be
produced higher up that valley than Northfield, loses its force, when
it is recollected that this formation was deposited before its strata
were elevated. For the elevating force undoubtedly changed the
relative level of different parts of the country. In this case, the
disturbing force must have acted beneath the primary rocks. And
besides, we have good evidence which will be shown by and by, that our
new red sandstone was formed beneath the ocean. We cannot then reason
on this subject from present levels.”

In 1840, H. D. Rogers, a geologist who has acquired a more widely known name than Hitchcock, but who in reality showed an inferior ability in interpretation, made the following statements in explanation of the regional monoclinal dip of the New Jersey Triassic rocks averaging 15 to 20 degrees to the northwest:[78]

“Their materials give evidence of having been swept into this estuary,
or great ancient river, from the south and southeast, by a current
producing an almost universal dip of the beds towards the northwest, a
feature clearly not caused by any uplifting agency, but assumed
originally at the time of their deposition, in consequence of the
setting of the current from the opposite or southeastern shore.”

In 1842, at the third annual meeting of the Association of American Geologists both H. D. and W. B. Rogers argued (=43=, 170, 1842) against Sir Charles Lyell and E. Hitchcock that the present dip of the Triassic was the original slope of deposition, stating among other reasons that the footprints impressed upon the sediments often showed a slipping and a pushing of the soft clay in the direction of the downhill slope. In 1858 H. D. Rogers still held to the same views of original dip,[79] notwithstanding that a moderate amount of observation on the mud-cracked and rain-pitted layers would have supplied the proof that such must have dried as horizontal surfaces. The idea of inclined deposition is not yet wholly dead as it has been suggested more than once within the present generation as a means of escaping from the necessity of accepting the very great thicknesses of this and similar formations. Thus, as Brögger has remarked in another connection,—the ghosts of the old time stand ever ready to reappear.

In the present essay on the rise of structural geology as reflected through a century of publication in the Journal, attention will be given especially to two fields, that of structures connected with igneous rocks and that of structures connected with mountain making, and emphasis will be placed upon the growth of understanding rather than upon the accumulating knowledge of details. The growth in both of these divisions of structural geology is well illustrated in the volumes of the Journal.

_Structures and Relationships of Igneous Rocks._

_Opposed Interpretations of Plutonists and Neptunists._

During the first quarter of the nineteenth century the geologic controversy between the Plutonists and Neptunists was at its height; the Plutonists, following the Scotchman, Hutton, holding to the igneous origin of basalt and granite, the Neptunists, after their German master, Werner of Freiberg, maintaining that these rocks had been precipitated from a primitive universal ocean. The Plutonists, although time has shown them to have been correct in all essential particulars, were for a generation submerged under the propaganda carried forward by the disciples of Werner. The “Illustrations of the Huttonian Theory of the Earth,” a remarkable classic, worthy of being studied to-day as well as a century ago, was published in 1802 by John Playfair, professor of mathematics in the University of Edinburgh and a friend of Hutton, who had died five years previously. This volume was opposed by Robert Jameson, professor of natural philosophy in the same university, who had absorbed the ideas of the German school while at Freiberg and published in 1808 a volume on the “Elements of Geognosy,” in which the philosophy of Werner is followed throughout and even obsidian and pumice are argued to be aqueous precipitates. The authority of the Wernerian autocracy caused its nomenclature to be adopted in the new world, but strong evidence against its interpretations was to be found in the actual structural relations displayed by the igneous rocks.

_Contributions on Volcanic and Intrusive Rocks._