Hall.] Q [January. 



Valley proper, at the base of the Lower Silurian Formation, In 

 like manner, the Canadian geologists, having traced the great fault 

 from Cape Gaspe, for seven hundred miles, along the south shore of 

 the Lower St. Lawrence, past Quebec, across the plain of the Riche- 

 lieu, and along the east shore of Lake Champlain, to meet the Hud- 

 son River Valley fault, which seems to terminate north of the High- 

 lands, it is now certain that the Quebec Group, the Georgia rocks of 

 Vermont, and the whole Taconic System of Dr. Emmons, belong to 

 the Lower Silurian System near its base, and are a thickening east- 

 ward of the calciferous sand-rock over the Potsdam Sandstone which 

 lies at its base. As soon as fossils were discovered in the slates on 

 the east side of the great fault, those slates had to be referred to the 

 base, instead of to the top of the Lower Silurian, But no further 

 change was needful. Everything else remained the same. The 

 structure of the Taconic range, and of the Canadian plain, remained 

 the same. Dr. Emmons's Taconic System beneath fhe Potsdam 

 sandstone has no existence now, any more than it had before the dis- 

 covery of the fossils, and their recognition by Barrande. Professor 

 Hunt, of Montreal, has shown how both M, Marcou and M. Bar- 

 rande have mistaken Dr. Emmons's language, where he speaks of an 

 "inversion" of the series in the Taconic Mountains, east of the Hud- 

 son, Dr, Emmons supposed the existence of not one great fault, 

 but numerous parallel faults, bringing up lower and lower sandstones, 

 slates and marbles, as one crosses them going east. His interpreters 

 ignorantly suppose a fan-shaped structure in the Green and Berk- 

 shire Mountains, overturning the dips in the ranges to the west of 

 them. Dr. Emmons taught an apparent inversion produced by the 

 parallel upthrows. His interpreters teach an actual inversion by 

 overthrow. The succession of the strata, however, is equally falsified 

 by the view of Dr. Emmons and by that taken by his interpreters. 

 Dr. Emmons, however, argued correctly from his premises. Did the 

 parallel and increasing upthrows exist, then the Taconic System 

 would be as he says it is, beneath the base of the Lower Silurian Sys- 

 tem. M, Marcou, on the contrary, misconceives the whole structure, 

 and his conclusion flows just contrariwise from his premises. The 

 recent careful map survey of the minute anticlinal subfolds of the 

 great fault along the east shore of the foot of Lake Champlain, by 

 Sir William Logan, has resulted in establishing the old accepted 

 order of the rocks, as both the apparent and the real order of the 

 Taconic System ; and the only resource we have is to accept his 

 theory, of a great thickening of the calciferous sand-rock along a deep 



