TO THE TACONIC SYSTEM. Ill 



inteilaminatcd. This question, thoiigli I deem it to have been set at rest by my own ob- 

 servations in Maine at the Megiinticook mountain in Camden, still as observations cannot 

 make an obscure question too clear and certain, I am induced to add, that last summer 

 (1845) I discovered beds of well characterized conglomerate at the base of this rock in 

 Williamstown. This l)ed may l>e traced witliin a few yards of granite, upon which it 

 evidently reposes. It is made up of pebbles (without any visible ceiueiil) of an oval shape, 

 some of which are of the size of a hen's egg. They consist mostly of the ([uartzose part of 

 granite or gneiss, rounded by attrition into smooth and well characterized pebbles, inter- 

 mixed with fine mica, which sometimes adheres to their surfaces. This discovery, it must 

 be admitted, settles the question as it regards the quartz, which is the most easterly mass 

 of the Taconic system, or so far at least as to carry it out of what is termed in this country 

 the Primary system, to which our gneiss and mica slate belongs ; and it furthermore goes 

 to show that the Stockliridgc limestone, and some of the primary-looking slates also, be- 

 long to the same era as the quartz rock. In Maine, I observed a variety of mica slate or 

 talcose slate, which contained well characterized chiastolite, resting upon this quartz rock, 

 and it may probably prove that most of these made rocks are of an age long posterior to 

 the Gneiss and Mica slate systems. 



There is another consideration which is deeply impressed upon my own mind, namely, 

 that the line of demarkation between the Taconic and the Primary systems is clearly 

 defined, especially upon the eastern side, where it was at one time supposed to be very 

 obscure. Commencing then at the quartz rock in Williamstown, at the top of what is there 

 called Oak hill, and ending at Troy, we pass over an uninterrupted succession of rocks 

 belonging to the Taconic system. The distance, in a direct line, is about thirty miles from 

 this bed of conglomerate. No primary appears on this route. On the more circuitous 

 roads, however, we meet with beds of the calciferous sandstone, reposing unconformably 

 upon the magnesian and taconic slate of the New- York system. At the junction of the 

 quartz with the granite, the dip of tlie former is to the southwest, or perhaps to the south. 

 The granite is rather peculiar, being a variety which contains a blue hyaline ([uartz ; and 

 it seems rather a persistent mass, inasmuch as it appears twenty-five and thirty miles to 

 the north, in Arlington (Vermont) , in precisely the same connection. It is, however, soon 

 succeeded by gneiss to the east. 



I have had occasion to speak of this granite before, and also of the termination of the 

 quartz in this direction. All that I wish here to impress upon the reader, is the affinity, 

 if I may use the expression, of tliose rocks which I have denominated Taconic, with them- 

 selves, or with each other ; or rather the general coincidence in dip and strike, producing 

 conformity with each other, and the non-coincidence or want of conformity with the Pri- 

 mary below and the New-York system above ; proving conclusively the occurrence of an 

 intermediate era or period of great length between the former and latter systems, during 

 which another system (the Taconic) was deposited. This carries us back a vast stride in 

 the earth's history, to the time when earthy sediments first began to accumulate or form 



