380 REPORT OF NATIONAL MUSEUM, 1904. 



sion, showing but one geological era for the deposition of the whole. In that era 

 the earth first witnessed the dawn of animal life and ages of its greatest fecundity in 

 marine organisms and the approach of the period when it became fitted to support a 

 vegetation so luxuriant and universal, of which no modern era has afforded a parallel. 



Hall, it should be noted, in this report, gave precedence to paleon- 

 tological characters over all others in distinguishing the sedimentary 

 strata, but recognized the fact that lithological characters must not be 

 wholly disregarded, a fact to which ho had previously called attention 

 (p. 383) 



Changes in the lithological features of a rock * * * which may render obser- 

 vations unsatisfactory or doubtful are usually accompanied by greater or less change 

 in the nature of the fossils. In no case, therefore, are to he overlooked either of the 

 three important facts and characters, viz: Lithological character, order of superposi- 

 tion, and nature of the contained fossils. 



At the time of making his report Hall's views regarding the drift 

 were still somewdiat hazy. That he did not accept Agassiz's doctrine 

 of a vast ice sheet is very evident. Thus he wrote: 



That blocks of granite either enclosed in ice or moved by other means have been 

 the principal agents affecting the diluvial phenomena; that they have scored and 

 grooved the rocks in their passage and, breaking up the strata and mingling them- 

 selves with the mass, have been driven onward, carrying everything before them in 

 one general melee. That such may have been the case in some instances or in lim- 

 ited localities can not be denied, but that it ever has been over any great extent of 

 country will scarcely admit of proof. 



The erratics he felt had been dropped from time to time by ice floes 

 and at a period apparently distant from that of the general drift. 



Hall was at this time evidently a eatastrophistand regarded the drift 

 soils, terraces, and the deep valleys and water courses as due to the 

 violent action of water, which may have been caused in part by a sud- 

 den submergence and the rapid passage of a wave over its surface. 

 His views were, indeed, in many respects, little, if any, in advance of 

 those held by Mitchill twenty-five years earlier. Like Mitchill, he 

 conceived of an inland sea bounded by and held back, in this case, by 

 the Canadian Highlands on the north, the New England range on the 

 east, the Highlands of New York and the Alleghenies on the south, 

 and the Rocky Mountains on the west. These presented a barrier of 

 from 1,000 to 1,200 feet above the level of the ocean until broken 

 through by the St. Lawrence, the Susquehanna, the Hudson, partially 

 by the Mohawk at Little Falls, and perhaps also by the Connecticut. 



But, to whatever cause we attribute the phenomena of the superficial detritus of 

 the fourth district, the whole surface has been permanently covered by water, for it 

 seems impossible that partial inundations could have produced the uniform character 

 and disposition of the materials which we find spread over the surface. 



Hall apparently failed at first to realize the efficacy of subaerial ero- 

 sion, and thought that the immense amount of denudation which had 

 taken place in his portion of the State could only have been accom- 



