AMERICAN GEOLOGY — THE TACONtC QUESTION. 663 



The first announcement of this conclusion appears to have been 

 made at the Philadelphia meeting of the American Association of 

 Geologists and Naturalists, held in April, 1841. Unfortunately 

 neither the paper nor the discussion which followed was printed in 

 detail. It is stated by Dana, however, that the matter was discussed 

 by II. I). Rogers, Edward Hitchcock, William Mather, James Hall, 

 and Lardner Vanuxem, all of whom had worked in the region. It is 

 stated, further, that none of the gentlemen, with the exception of 

 Vanuxem, favored the views put forward by Emmons. 



During the summer following both Rogers and Hall studied the sec- 

 tion, as described by Emmons, in the field, Rogers rendering a report 

 to the American Philosophical Society at Philadelphia at the meeting 

 in 1842. In this report Rogers sustained the views previously advo- 

 cated by Hitchcock, Hall, Mather, and himself, to the effect that the 

 rocks were Lower Silurian (as the term was then used) extending from 

 the Potsdam upward, but much Hexed and disguised by partial meta- 

 morphism. Hall for some reasons failed to make a report at the time, 

 though later claiming to have written out his notes very fully (see 

 p. 671). 



In his paper in the Report on the Geology of the Second District of 

 New York, in 1842, where the system is first elaborated, Emmons 

 referred to Rogers's conclusions, and seemingly himself recognized 

 the possibility of the various beds of limestone being but portions of 

 the same bed, brought to the surface by successive uplift. He did 

 not, however, regard the same as probable. The system as a whole 

 he thought to be the equivalent of the Lower Cambrian of Sedgwick, 

 the upper portion being the lower part of the Silurian system. 



Although the Proceedings of the American Association of Geolo- 

 gists were not given in full, as already noted, the opinions of Mather 

 regarding the Taconie have fortunately been handed down to us in his 

 Report on the Geology of the First New York District, dated 1843. In 

 this he made use of the term in his descriptions, but stated emphatically 

 that the "Taconie rocks are the same in age as those of the Champlain 

 division, but modified by metamorphic agency and the intrusion of 

 plutonic rock." 



In December, 1844, Emmons brought out in pamphlet form a revision 

 of the Taconie system, with additions and an extension of its limits. 

 This was published without change as a chapter in his Report on the 

 Agriculture of New York, under date of 1846. The most important 

 feature of this revision related to the finding of fossil crustacean 

 remains in the Black slate of Bald Mountain, in Washington County, 

 New York. These he accounted for on the supposition that the beds, 

 instead of being the lowermost, as he first supposed, belonged in 

 reality to the top of the series, and had come into their present posi- 

 tion through a reversion of the strata, adopting thus in part Rogers's 



