88G 



GEOLOGY IN AMERICA. 



[1855. 



would occasion is not very distinctly appurent in tlie Tertiiuy period, 

 and much less in the earlier, we have reason for referring the grenter 

 part of the elevation to that drift era, and for believing that the exca- 

 vation of these fiord valleys was then in progiess. Both fiords and 

 drift are alike high-latitude phenomena on all the continents north and 

 south. The change of climate between the Cretaceous and Tertiary, 

 and the absence of tertiary beds north of Cape Cod, may have been 

 connected with an incipient stage in this high-latitude movement. 



However this be, there is other evidence in the cold of the drift 

 period of some extraordinary cause of cold. The drift in Europe and 

 Britain is generally attributed to glaciers and icebergs during a period 

 of greater cold than now ; and the fact of this greater cold is so 

 generally admitted that it is common to speak of it as the glacial epoch. 

 Prof. Agassiz, moreover, has urged for this continent the glacial theory. 



In a memoir of great research, by JJr. Hopkins, of Cambridge, 

 England, the able author maintains that this glacial cold might have 

 been produced over Europe, partly at least, by a diversion of the Gulf- 

 stream from its present position. He seems in his paper to attribute 

 too much effect to the Gulf-stream and too little to the prevailing 

 currents of the »traosphere ; but setting this aside, it is unfortunate 

 for the hypothesis that there is no reason to suppose that xVmevica was 

 not then as much in the way of such a diversion as now. The small 

 changes of level which the Tertiary and Post-tertiary of the Gulf have 

 undergone, prove that the gate of Darien was early closed, and has 

 since continued closed. America, as far as ascertained facts go, has 

 not been submerged to receive the stream over its surface. If it had 

 been, it would have given other limits to her own drift phenomena ; 

 for it is an important fact that these limits in America and Europe 

 show the very same differences in the climates or in the isothermals, 

 as that which now exists. 



On the question of the drift, we therefore seem to be forced to con- 

 clude that, whatever be the difficulties we may encounter from the 

 conclusion, the continent was not submerged, and therefore icebergs 

 could not have been the main drift agents. The period was a cold or 

 glacial epoch, and the increase of cold was probably produced by an 

 increase in the extent and elevation of northern lands. Further than 

 this, in the explanation of the drift, known facts hardly warrant our 

 going. 



If then the drift epoch was a period of elevation, it must have been 

 followed by a deep submergence to bring about the depression of the 

 Continent, already alluded to, when the ocean stood at least 400 feet 

 in Lake Champlain, and a whale was actually stranded on its shores; 

 and when the upper terrace of the rivers was the lower river flat of the 

 valleys. 



This submergence, judging from the elevated sea beaches and ter- 

 races, was 400 to 500 feet on the St. Lawrence and Lake Champlain ; 

 80 feet at Augusta, Me. ; 50 feet at Lubec ; 30 feet at Sancoti Head, 

 Nantucket; over 100 at Brooklyn, N.Y., and 200 to 250 in Central 

 New England, just north of Massachusetts ; while south in South 

 Carolina it was but 8 feet. 



But whence the waters to flood valleys so wide, and produce the 

 great alluvial plains, constituting the upper terrace so immensely 

 beyond the capability of the present streams ? Perhaps, as has been 

 suggested for the other continent, from the melting snows of the 

 declining glacial epoch. The frequent absence of fine stratification, so 

 common in the material of this upper terrace, has often been attributed 

 to a glacial origin. 



According to this view, the events of the Post-tertiary period in this 

 country make a single consecutive series dependent mainly on polar or 

 high-latitude oscillations. An elevation for the first or Glacial epoch ; 

 a depression for the second or Laukentian epoch ; a moderate elevation 

 again, to the present height, for the third or Terrace epoch. 



The same system may, I believe, be detected in Europe ; but, like 

 all the geology of that continent, it is complicated by many conflicting 

 results and local exceptions, while North America, as I have said, is 

 like a single unfolding flower, in its system of evolutions. 



There is the grandeur of natui-e in the simplicity to which we thus 

 reduce the historical progress of the continent. The prolonged series 

 of oscillations, acting by pressure from the south-east beneath the 

 Atlantic, reach on through immeasureable ages, producing the many 

 changes of level through the Silurian and Devonian, afterward with 

 greater frequency in the Carboniferous, and then, rising with quick- 

 ened energy and power, folding the rocks and throwing up the long 

 range of the Apalachians with vast effusions of heat through the racked 

 and tortured crust, next go on declining as the Jurassic and Cretaceous 

 periods pass, and finally fade out in the Tertiary. The Northern 

 oscillations, perhaps, before in progress, then begin to exhibit their 



effects in the high temperature latitudes, and continue to the Human 

 Era. The sinking of Greenland now going on may be another turn in 

 the movement ; and it is a significant fact that while we have both 

 there and in Sweden northern changes of level in progress, such great 

 secular movements have nowhere been detected on the tropical parts 

 of the continent. 



In deducing these conclusions I have only stated in order the facts 

 as developed by our geologists. Were there time for a more minute 

 survey of detail the results would stand forth in bolder characters. 



The sublimity of these continental movements is greatly enhanced 

 when we extend our vision beyond this continent to other parts of the 

 world. It can be no fortunate coincidence that has produced the 

 parallelism between the Appalachian system and the great feature 

 lines of Britain, Norway and Brazil, or that has covered the North and 

 South alike with drift and fiords. But I will not wander, although the 

 field of study is a tempting one. 



In thus tracing out the fact that there has been a plan or system of 

 development in the history of this planet, do we separate the Infinite 

 Creator from his works ? Far from it; no more than in tracing the 

 history of a plant. We but study the method in which Boundless 

 Wisdom has chosen to act in creation. For we cannot conceive that 

 to act without plan or order is either a mark of divinity or wisdom ; 

 and assuredly it is far from the method of the God of the Universe, who 

 has filled all Nature with harmonies ; and who has exhibited his will 

 and exalted purpose as much in the formation of a continent, to all its 

 details, as in the ordered evolution of a human being. And if man 

 from studying physical nature begins to see only a deity of physical 

 attributes, of mere power and mathematics, he has but to look within 

 at the combination of the affections with intellect, and observe the 

 latter reaching its highest exaltations when the former are supreme, 

 to discover that the highest glory of the Creator consists in the infini- 

 tude of his love. 



My plan laid out in view of the limited time of a single address, has 

 led me to pass in silence many points that seemed to demand attention 

 or criticism; and also to leave unnoticed the labors of many successful 

 investigators. 



There are some subjects, however, which bear on genei'al geology 

 that should pass in brief review : — 



I. The rock-formations in America may in general be shown to be 

 synchronous approximately with beds in tiae European series. But it 

 is much more difficult to prove that catastrophes weie synchronous ; 

 that is, revolutions limiting the ages or periods. 



The revolution closing the Azoic age, the first we distinctly observe 

 in America was probably nearly universal over the globe. 



An epoch of some disturbance between the Lower and Upper Silurian 

 is recognized on both continents. Yet it was less complete in the 

 destruction of life in Europe than here — more species there surviving 

 the catastrophe ; and in this country there was but little displacement 

 of the rocks. 



The Silurian and the Devonian ages each closed in America with no 

 greater revolutions than those minor movements which divided off the 

 subordinate periods in those ages. Mr. Hall observes that they blend 

 with one another and the latter also with the Carboniferous ; and that 

 there is no proof of cotemporaneous catastrophe, giving them like 

 limits here and in Europe. But after the Carboniferous came the 

 Appalachian revolution, one of the most general periods of catastrophe 

 and metamorphism in the Earth's history. Yet in Europe the distur- 

 bances were far less general than with us, and occurred along at the 

 beginning and end of the Permian period. 



From this epoch to the close of the Cretaceous, there were no 

 cotemporaneous revolutions, as far as we can discover. But the Creta- 

 ceous period terminates in an epoch of catastrophe which was the most 

 universal on record — all foreign cretaceous species having been exter- 

 minated, and all American with a few doubtful exceptions. This third 

 general revolution was the prelude to the Mammalian age. 



But there is no time to do this subject justice, and I pass on, merely 

 adding, on account of its interest to those who would understand the 

 first chapter of Genesis, that there is no evidence whatever in geology 

 that the Earth after its completion passed through a chaos and a six 

 days' creation at the epoch immediately preceding man, as Buckland 

 in the younger days of the science suggested on Biblical, not on 

 geological ground. No one pretends that there is a fact or hint in 

 geology to sustain such an idea ; moreover the science is totally opposed 

 to it. 



II. The question of the existence of a distinct Cambrian System is 

 decided adversely by the American records. The Molluscs, in all their 

 grand divisions appear in the Lower as well as the Upper Silurian, and 



