242 |ifr 5 £ft iX Dana-^Zower Silurian Fossils 



the " Sparry limestone " interstratified with the slates west of 

 the Taconic Eange and for the mosi part lying against the west 

 side of the range; (3) The " talcose " or " magnesian " schist 

 (as he called it) constituting the Taconic Eange, and Grreyiock 

 or Saddle Mountain, the high ridge between Williamstown and 

 Adams in the northwestern angle of Massachusetts ; (4) the 

 Stockbridge limestone, east of the range of Taconic schist ; 

 (5) quartzyte. 



He described the prevailing dip of the strata as eastward, as 

 later investigators have done. He made the sparry or western 

 limestone older than the Taconic schists, the limestone dipping 

 under the schists. The belt of sparry or western limestone 

 (sparry is a misleading term and was afterward rejected by 

 him) he described as extending through the New York towns 

 of Hoosic, Petersburg, Berlin, New Lebanon, Canaan and Hills- 

 dale, along the west side of the Taconic Eange. 



The above-mentioned series of rocks constituted the Taconic 

 System as propounded and described by Prof. Emmons in 1842. 

 He says, on page 136 of this Eeport: 



" The Taconic System, as its name is intended to indicate, 

 lies along both sides of the Taconic Eange of mountains, 

 whose direction is nearly north and south, or, for a great dis- 

 tance parallel with the boundary line between the State of New 

 York and those of Connecticut, Massachusetts and Vermont." 

 He remarks that the rocks extend farther north through Ver- 

 mont into Canada, but gives no details about Vermont or 

 Canada localities, and adds, " It is, however, in Massachusetts, 

 in the County of Berkshire, that we find the most satisfactory 

 exhibition of these rocks." 



Prof. Emmons's declaration, in this first detailed account of 

 the system, as to what is the typical Taconic series, must be 

 accepted ; and the geological age of these beds — the rocks of 

 the original Taconic System — whatever it may prove to be, 

 must therefore be taken as the age of the Taconic System. 



The stratigraphical observations of Prof. Emmons are right. 

 But he took a step of questioned correctness when he con- 

 cluded in 1842 that the system was intermediate in age be- 

 tween the New York Potsdam sandstone and what he calls the 

 4 ' Primary " system lying to the eastward; or, as stated, in 

 another place (on page 163) that the rock "appears to be 

 equivalent to the Lower Cambrian of Sedgwick." For the 

 criterion of age which he announced, namely: "As a general 

 rule, certain minerals are found in particular rocks " was of 

 unascertained value ; and the facts referred to as a basis of his 

 conclusion : that the Taconic quartzyte is interstratified with 

 limestone ; that the limestones are peculiar in grain ; and others 

 of related character, are doubtful evidence for separating them 



