204 The Taconic System. [Oct., 



position, we may despair of establishing any proposition in this 

 department of knowledge. We proceed to give the substance of 

 our remarks. 



" Dr. Emmons observed at the opening of the question in regard 

 to the Taconic system, that it was necessary to be well acquainted 

 with the Champlain division of the New York system. Thence 

 he was led to speak briefly of these members, and especially to 

 point out the fact that tlje Potsdam sandstone is often absent, in 

 which case the calciferous sandstone becomes the inferior rock of 

 the series. Thus at Little Falls this rock rests on gneiss, with 

 w^hich it appears to conform in dip. The succession of the rocks 

 of the Champlain division was then given, which need not be 

 repeated in this place, except that in this connexion it was stated 

 that the superior part of the Potsdam sandstone, near Chazy, in 

 Clinton county, N. Y., was formed of a breccia, which contained 

 masses of a sedimentary limestone, an important fact, the bearing 

 of which could not be misunderstood by the gentlemen present. 



Dr. E. then stated that the Taconic rocks were limited by the 

 Hoosick mountain range on the east, and by the Hudson river and 

 Lake Champlain on the west, and he should confine his re- 

 marks to this section of country, although he was aware that the 

 same system extended far north as well as south, and that it even 

 existed in Maine, Rhode Island, and the upper peninsula of Mi- 

 chigan. The oldest rock of this system, is the granular quartz: 

 a rock which was formerly ranked with the primary, but which 

 was clearly separable from that system, on the ground that its in- 

 ferior part is a conglomerate; thus proving its sedimentary origin. 

 Oakhill, near Williams College, supjports a mass of this charac- 

 ter which reposes on granite. Stonehill, an eminence just south 

 of the college, is composed of quartz alternating several times 

 with a variety of slate, containing tale, needleform schorl and 

 crystals of octahedral iron. The rocks of these hills conform to 

 those which lie west and form the Taconic range, lying between 

 New York, Massachusetts and Vermont. The line of demarcation 

 then, between the primary of the Green Mountains and the Taco- 

 nic rocks is clearly indicated by the conglomerate of the quartz. 



