284 GEOLOGY OF THE SECOND DISTRICT. 



the lake, yet it will be found in insulated beds or masses, and in this respect it resembles 

 the rocks. It extends from the lake in the rear of all those low ranges of mountains which have 

 been described as terminating upon its shores ; but on leaving the lake, it rarely contains 

 fossils, though it preserves its lithological characters. 



The fact now stated, that the fossils are confined to the present shore of the lake, goes to 

 favor the opinion often expressed in this report, that the topographical features of this portion 

 of the State have undergone no important changes since the deposition of the tertiary. The 

 estuary was undoubtedly deeper than the lake ; but the most favorable positions for those 

 animals whose remains are now found, were near the present shores of the lake ; and to 

 restore in our minds the former conditions, we have only to imagine the valley slightly 

 depressed, to sink the shores to that depth at which the same species are now found in our 

 present estuaries and coasts. 



Superficial Deposits, Drift, Peat, &c. 



In a region so mountainous as Essex county, it cannot be expected that extended deposits 

 of any of the later kinds should exist. There are no wide plains and valleys for their recep- 

 tion : hence we merely find a few unimportant beds of peat, bog iron ore, marl or tufa. Drift, 

 one of the most superficial of all the deposits of this county, exists every where, except upon 

 the sides and summits of the highest mountains. The general arrangement also prevails here 

 as elsewhere, and the same general phenomena. The loose materials were all transported 

 southward, and hence the boulders of hypersthene rock do not occur on the east or Vermont 

 side of Lake Champlain. The fragments of the porphyry dyke at Essex are found at the 

 south, but never to the north of Canon's point ; and the peculiar reddish greywacke or grit 

 is common for a great distance south, but it never reaches the higher valleys of the Hudson 

 river. 



At the base of the ranges of mountains, I find an accumulation of debris composed entirely 

 of the hypersthene rock ; and being unmixed with other materials from other sources, I am 

 disposed not to regard it as the ordinary drift of the country. It appears to belong to a dif- 

 ferent period, and to have been deposited by different agents. If, however, it is to be regarded 

 as ordinary drift, it has been transported only from the sides and summits of the ranges to 

 their bases, and it appears rather to have slidden down to its present level. The facts are 

 more clear in consequence of the peculiar location of the northern ranges, and their abriipt 

 termination, and still more so from the well known characters of the rocks themselves, their 

 debris being as easily recognized as the parent rock from which it is derived. Without stating 

 specifically the position of this debris, I only remark generally that it may be observed in the 

 vicinity of most of the head waters of the principal rivers which rise in this region. It is, of 

 course, local : no continuous beds or extended lines of these materials are ever seen. It may 

 be distinguished from drift, by the more angular shape of the masses : the stones in these 

 beds, though somewhat rounded, yet are much less so than in drift, or where the same mate- 

 rials are accumulated. 



