Classes of Detritus. 157 



into its present situation by any existing cause, its character 

 is unquestionable ; such as the Erie Canal line from Little 

 Falls to near the Genesee river. This great diluvial trough 

 of one hundred and sixty miles in extent, could not have 

 been scooped out and filled by any existing cause. But the 

 Detritus on which Troy, N. Y. is built, might have been 

 produced by the Hudson : Yet, as the constituents resemble 

 those of the great diluvial trough in every particular, we 

 feel a confidence in the opinion that it is diluvial. In both 

 localities, though eighty miles apart, the Hemlock tree, 

 (Pinus canadensis) with its roots, trunk, branches and green 

 leaves, is the chief vegetable. In both localities we find 

 much quicksand, masses of clay, gravel, &c. which are 

 much alike. These remarks will apply to numerous other 

 localities, which I have examined. This subject will be re- 

 sumed in its proper place.* 



23. Ultimate Diluvion. 



I believe nothing had been published on this subject until 

 I made a communication to the American Journal of Sci- 

 ence, vol. 12, p. 17, unless DeLuc and Jameson intended 

 the word Geest for this stratum. Their definition, however, 

 would seem to embrace surperficial analluvial also. Since 

 that time the subject has occupied the attention of many 

 accurate observers. Prof. Cleaveland has observed it in 

 the state of Maine, and it has been recognized by several 

 geologists in most of the ancient elevated forests of Massa- 

 chusetts, Connecticut, New York, and Pennsylvania. It is 

 always some shade of yellow, and gray, or rather a light dir- 

 ty orange. It is best characterized when reposing on the 

 hard-pan variety of crag. It is from three to nine inches 

 thick in most localities. When thicker we can generally 

 find evidence of its having been accumulated by the last 

 settling of water into basins, or depressions of the surface of 

 the crag. 



24. Post-Diluvion. 



In the beds of large rivers this may be distinguished from 

 diluvion by an undeviating character. The coarse ■pebbles 

 are always higher up the river than the fine sediment. For 



* Reference would be made to the Alluvial detritus of New York, and Long 

 Island, but neither Mrs. Griffith's, nor Dr. De Kays' excellent essays seem to be 

 sufficiently particular to establish its character. 



