OF ARTS AND SCIENCES. 221 



" Etant prive ici de beaucoup de ressources litterairos, je suis pen 

 au coiirant de ce qui se passe en Ameiique. J'igiiorais qu'il fut de 

 nouveau question de systeme Taconique. 



'' Je serai cliarme de voir les figures des fossiles (de Georgia) que 

 Mr. Whitfield va publier d'apres vos materiaux. 



" J. Barrande." 



III. Vertical and General Section of the Taconic Sys- 

 tem. — Infra-Primordial, Primordial, and Supra-Pri- 

 mordial Faun.e. 



The dislocation of strata which occurred at the close of the deposit 

 of the " Taconic slates," the last group of which I have culled " Swan- 

 ton slates," is the greatest as regards the breaking, squeezing, and 

 local folding which has ever occurred in North America. The lateral 

 pressure came from the east-east-south and met the inassifs of terra 

 Jirma of the Laurentine and the Adirondacks ; all the strata were 

 pressed together and taken between the force which pushed them from 

 the east and the resistance from the west-west-north. Tiiey were 

 first raised to a vertical position, and then overturned in fanlike 

 shaj)e. 



Such are the origin and the form of that local folding of the earth's 

 crust called the Green Mountain Chain of Vermont. The upper part 

 of the " Swanton slates" came up against an<l spread over the crys- 

 talline rocks of the Adirondacks and the Laurentines, forming small 

 local folds. The denudation took place immediately after; then the 

 sea flowed over the upper part 'of the Taconic, extending even fartlier 

 west, over the crystalline group of the Adirondacks, forming a gulf, 

 of which Lake Champlain is the last witness, because it occupies 

 a small part of it. This gulf deposited the " Potsdam sandstone," 

 which covers a part of the Taconic. A new dislocation at the end of 

 the Potsdam diminished the size of this gulf, reduced now to a sort of 

 sound or fiord, in which the strata of the " Champlain series," or the 

 true " Second fauna," were deposited, deposits which, added to the 

 Potsdam, cover and hide entirely the upper part of the " Swanton 

 slates." 



But where the sea which deposited the Potsdam did not reach, as 

 along the Laurentines from Three Rivers to Quebec, St. Anne, and 

 lower down along the St. Lawrence River, all the "Swanton slates" 

 must be found complete, leaning against the crystalline rocks. It is 

 so at Quebec, Charlesbourg, Indian Lorette, Montmorency's fall, and 



