328 Association of American Geologists and Naturalists. 
and the space filled with loose materials. Sometimes large masses 
were thrown over upon the stratum in place to the south—at other 
times they had been lifted and fallen back, presenting abrupt anticlinal 
axes of small extent. 
In the section before us similar causes seem to have operated ina 
more stupendous manner, and to have produced corresponding results. 
He gave an explanation of the section, which consists of a stratum 
of loam, resting on clay and gravel, and below this the shaly strata, 
which are cracked throughout into short blocks as if by a violent undu- 
latory motion ; insinuated beneath these, and between different strata, 
we find clay, gravel and pebbles, with smaller fragments of the shale. 
These materials are often folded and cortorted in such a manner as to 
lead to the conclusion that they could only have been produced by a 
tremendous force from the northward, forcing the loose materials be- 
neath and between the strata, and mers - whole to the southward, 
producing the folded appearance. =~ 
The surface of the firm rock behenth is Gries and striated, pre- 
cisely in the same manner as the surfaces of our present strata, so that 
if the broken rocks above were removed the surface would present the 
same appearances as those of the grooved and polished rocks. . 
It is here quite evident that the breaking up of the strata, the inter- 
mingling of the drift, &c., all took place during a single period, being 
produced by a force movi to the southward. This ihc whatever it 
may have been, seems sufficient to have produced the breaking up of 
strata, the production of worn fragments, and the excavation or denuding 
operations every where visible. 
The phenomena presented in this instance lead us to the most inter- 
esting conclusions, but whether we are warranted in assuming that sim- 
ilar causes may have produced the effects every where, it is perhaps 
impossible to decide. The subject of drift and the causes of its pro- 
duction are still open to discussion, and no theory yet advanced seems 
satisfactory to all parties. Therefore, without a desire to advance any 
theoretical considerations, he had presented the facts for the considera- 
tion of the Association. 
After explanation of sections of the drift and river sash at 
ees: Mr. Horsford inquired whether there was evidence of 
he original north and south valleys having been excavated by 
a force operating from south to north. 
Mr. Hall replied that he had formerly embraced that opinion; 
but finding no positive evidence of such a force had abandoned it. 
If this opinion were true we should expect to have found remains 
of southern drift among the loose materials at the north, but s° 
far from this being the case he had always found northern mate- 
ye 
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