CHAMPLAIN DIVISION. 117 



I. CHAMPLAIN DIVISION. 



Having given the grand divisions of the New-York system, we may proceed rapidly to 

 the consideration of the individual members which compose them ; and in doing this, their 

 agricultural relations appear to us the most important, and hence I propose to keep those 

 relations in the foreground. In the Taconic system I had a special object in view, namely, 

 its establishment, and therefore those characters and relations which are geological were 

 mainly dwelt upon. 



§ 1. Potsdam sandstone. 



This sandstone is more uniform in its characters than most of the individual rocks in the 

 series. At Potsdam, it is yellowish brown ; at Moira and its neighborhood, and also in 

 Mooers, it is nearly white, and sandy ; at Chazy, it is of a deep red at the bottom, and 

 gray towards the top ; while at Whiteball, Corinth, Hammond, and near Glensfalls, it is 

 gray and more or less crystalline. In many places it is a coarse conglomerate, as at Mooers 

 in Franklin county, and at Dekalb in St. Lawrence county. It is of course a siliceous 

 rock, yet it does not exclude other substances or elements ; for, a true sandstone, far from 

 being composed of pure siliceous sand, admits into its composition mica and felspar, oxide 

 of iron, and probably even a greater variety of the primitive minerals, as hornblende, 

 pyroxene, etc. in a state of fine division. This being the case, it does not necessarily 

 make, on decomposition, a pure siliceous soil, or one free from alkaline matters : the mica 

 and the felspar being decomposable minerals, especially the latter, we may expect to find 

 traces of their elements in the soil. One way of determining the nature of the soil formed 

 from this or any other sandstone, is to inspect it carefully with a common microscope, by 

 which means we may discover the composition of the rock : the mica vv'ill be found in 

 small glimmering scales, and the felspar in dull earthy grains destitute of the vitreous 

 lustre. All grains possessing this lustre, or that of glass, may be considered as either 

 silex or quartz. 



This rock has suffered greatly by denudation. Being superimposed in New- York upon 

 the Primary system, it has been exposed more directly, and for a longer period, to the action 

 of those causes which destroy the solid strata, than have the subsequent ones ; and, besides, 

 it has been exposed more directly in consequence of position. It has been first broken up 

 on its interior rim, which rests on the primary, north of the Mohawk valley ; and hence, 

 for this reason we find it more or less fissured or cleft, as well as distributed widely in 

 boulders and fragments. 



Its soil. The soil formed from this rock, is one possessing very distinctly the character 

 of a granitic soil ; which, to be sure, is partly owing to the position it occupies, inasmuch 

 as the debris of granite and gneiss must mix more or less with it. 



