278 AXNUAL OF SCIENTIFIC DISCOVERY. 



THE TACONIC SYSTEM. 



The geological questions involved in the so-called " Taconic Sys- 

 tem " of Dr. Emmons have continued during the past year greatly to 

 interest the attention of American and European geologists, and the 

 discussions relative thereto have occupied to a considerable extent 

 the pages of Silliman's Journal, and the Proceedings of the Boston 

 Natural History Society. To attempt to give even a brief resume of 

 the recent discussions of the subject would occupy a greater space 

 than the limits of the present volume will allow ; but it is sufficient, 

 however, to say that the geological views expressed by Dr. Emmons 

 in 1844, and which have since been scouted at and ridiculed by most 

 American geologists, and which have even been taken advantage of 

 by certain unscrupulous scientific opponents to bring Dr. Emmons's 

 name and character into contempt before the public, have now been 

 admitted by all geologists to be true in part, and by many to be true 

 altogether. The essential points involved in this subject of the Ta- 

 conic System are thus clearly presented in the March (1861) number 

 of Silliman's Journal : 



" The rocks under discussion occupy a belt of country east and west 

 from twenty to sixty miles wide, stretching from the vicinity of the 

 city of New York in a northerly direction to Lake Champlam, and 

 thence through Vermont and Lower Canada to Cape Gaspe at the 

 mouth of the St. Lawrence. The strata, consisting of slates, lime- 

 stones, sandstones, and conglomerates, are greatly disturbed, plicated 

 and dislocated, and arc often, especially along the eastern side of the 

 belt, in a highly metamorphic condition. On this side they are over- 

 laid unconformably by Upper Silurian and Devonian rocks, but on 

 the western and northern margin they are in contact with, and in 

 general seem to be a continuation of, the Lower Silurian. Some of 

 the slates of the formation closely resemble in lithological characters 

 those of the Hudson River group, and thus along the western side of 

 the region, where the junction of the two formations occurs, it is 

 often impossible to draw the line between them. The dip and strike 

 of both are in the same direction, and throughout extensive areas the 

 newer rocks appear to plunge beneath the older. The whole dis- 

 trict affords an excellent example of those cases, so well known to 

 field geologists, where the true relations of the different masses can- 

 not be clearly worked out without the aid of fossils, and where the 

 best of observers may arrive at diametrically opposite opinions. 



" Dr. Emmons, one of the geologists of the New York Survey, early 

 convinced himself, by a careful examination of these rocks, that they 

 constituted a distinct physical group more ancient than the Potsdam 

 sandstone, the latter being regarded by him as the base of the Lower 

 Silurian system in North America. His views were given in detail 

 in 1842 in his final report on that part of the State confided to his 

 charge, and in a more special manner in another work entitled The 

 Taconic System, published in 1844. In this latter work he figured 

 several species of fossils which had been collected in different parts 

 of the formation. Two of these were trilobites, and were described 

 under the names of Atops trilineatus and Elliptocerfiala asaphoides. 

 The others were graptolites, fucoides, and apparently trails of anel- 



