Geological Reports on the State of New York. 27 



have been filled with chlorite or carbonate of lime ; 2, a compact am- 

 phibole, or hornblende ; and 3, sienite, or a compound of feldspar and 

 hornblende ; 4, a reddish porphyry, in which the crystals of feldspar are 

 small and indistinct. They pursue an easterly and westerly course, and 

 extend a great distance ; and, indeed, I have not been able to ascertain 

 their extent in a single instance. This is owing partly to the wooded 

 state of the country. The largest of them is at Avalanche Lake. It is 

 80 feet wide, and cuts through Mount McMartin, nearly in its center. 

 The gorge formed by the breaking up of this dyke extends entirely or 

 nearly to its summit. A portion of the northern face of the wall may be 

 seen from lake Henderson, a distance of five or six miles. This gorge 

 exhibits, on a large scale, the powerful effects of frost and water, in 

 breaking up the solid crust of the globe. In it are rocks from 50 to '100 

 feet in length, broken up from their original beds, and carried partly 

 down the declivity ; they lie in confusion in all directions, and constitute 

 together a mass of ruins from the base of the mountain to its summit." 



In the sandstone of Essex there are ripple marks at the depth 

 of seventy to eighty feet in the sandstone, which, with that of 

 Potsdam, is a part of the grauwacke formation of Europe. 



The tertiary formation of Lake Champlain presents some 

 interesting features. Mr. Emmons inclines to the opinion that 

 Lake Champlain, which is ninety seven feet above the ocean and 

 more than six hundred feet deep, was formerly connected with 

 the Hudson on the one hand, and the St. Lawrence on the other. 

 The tertiary deposited when this connection existed, rises in Yer- 

 mont 200 feet above the lake, and there is reason to suppose, may 

 belong to the same era with the beds on the Hudson. Many good 

 reasons are given for this opinion, and it appears that the ocean 

 overflowed here, as the rocks are deeply water-worn in continu- 

 ous channels, particularly at West Port, towards Essex, and marine 

 shells are found in the tertiary beds of Essex county and of Lake 

 Champlain, although absent from those on the Hudson. The 

 tertiary strata appear to have been brought into day light, not by 

 drainage, but by an uplift of the land, and there are indications 

 that this is one of the most recent of the tertiary formations. 



Mountains of Essex County. — Mr. Wm. C. Redfield gave an 

 mteresting account of these mountains in Vol. xxxiii, p. 30 i of this 

 Journal. The following citations from the report may, however,, 

 be interesting. 



" The group, taken as a whole, is more lofty than the White Hills of 

 New Hampshire, though the main summit, Mount Washington, exceeds 

 Mount Marcy by 767 feet ; for there remain unmeasured many peaks 



