XIII.] GEOGNOSY OF THE APPALACHIANS. 251 



To the west of the hills of primary schist, he placed his 

 Taconic system, named from the Taconic hills, which run from 

 north to south along the boundary line of New York and 

 Massachusetts, and form a range parallel with the Green Moun- 

 tains. The lower portions of the Taconic system, according to 

 Emmons, are schistose rocks made up from the ruins of the 

 primary schists which lie to the east of them. Thus the talcose 

 schists of Berkshire are said to be regenerated rocks, belonging 

 to the newer system, but showing the color and texture of the 

 older talcose schists from which they were formed. How far 

 this is true of these particular strata may be a question, for 

 there is reason to believe that Emmons included among his 

 Taconic rocks some beds belonging to the older crystalline 

 series of the Green Mountains ; yet it is not less true that the 

 possibility of derived rocks of this kind is one which has been 

 too much overlooked by geologists.* Emmons elsewhere re- 

 marks that, while the talcose slates of the primary are associated 

 with steatite and with hornblende, these are never found in 

 the Taconic rocks, and also, that epidote, actinolite, titanium 

 (rutile), etc., which are characteristic minerals of the primary, 

 are wanting in the Taconic system. 



The statements of Emmons on this point were sufficiently 

 explicit ; he included in the primary system all of the crystal- 

 line schists of the Green Mountains, except certain talcose and 

 micaceous beds, which he supposed to be made up of the ruins 

 of the similar strata in the primary, and to constitute, with a 

 great mass of other rocks, the Taconic system ; which was, in 

 its turn, unconformably overlaid by the Potsdam sandstone 

 and Calciferous sand-rock of the New York system. His views 

 have, however, been misunderstood by more than one of his 

 critics ; thus, Mr. Marcou, while defending the Taconic system, 

 makes it to include the three groups just mentioned, namely, 

 1. The Green Mountain gneiss ; 2. The Taconic strata as 

 denned by Emmons ; and, 3. The Potsdam sandstone ; t thus 



* Some observations on this point will be found in Essay XIV. 

 t Proceedings of Boston Society of Natural History, November 6, 1861, and 

 American Journal of Science (2), XXXIII. 282. 



