jj . H. Wmchell on ilie Taconic. 165 
Objection No. 1. 
The old objection which was at the first uro;cd against the 
Taconic still survives, and is urg-ed principally by Prof. Dana. 
// /s the cqui-calcnt of strata above the Potsdam , and only tJiat^ 
and comes into conflict v:ith the term Silurian. An^•one who 
examines Prof. Dana's papers, extended throug-h the volumes 
of the American Journal of Science, from 1S70 to this date, will 
cjuickl}- learn that the basis of all his opposition to the Taconic, 
and the mainspring of all his able investigations in the rocks 
Iving in Vermont and western Massachusetts, is that concejitinn 
of the Taconic which he acquired in 1S42, on the publication of 
the geological report of Emmons on the second district. This 
he distinctiv affirms in his letter to ]Mr. Billings in 1S72,' wlicre 
he defines his idea of " the true Taconic." In thus restricting 
Mr. Emmons to his first pul)lished description of the Taconic, 
he violates one of the above mentioned canons of nomenclature. 
This is a sufficient answer to this objection, but, it appears that 
even with that restriction, if exact justice be done to Dr. 
Emmons, he mav be allowed to include the priniordial strata 
along ^vith those which are post-Potsdam, in the Taconic of 
1843. He defines its geographic area to extend from the Iloosic 
hills on the east to the limits of "the New York transition sys- 
tem on the west." He did not attemjjt to give exact geographic 
definition to his svstem in that report. It was impossible. He 
relied on the fundamental idea of his system, and stated that 
there were "great perplexities as regards the true limits of 
either s\stem." (p. 137). 
But l)i'. Emmons had a perfect right to remodel his strati- 
graphic scheme, and to extend or restrict it," and no one objected 
to it till 1S72. It was found that at the same time with the 
change, he actualh' demonstrated, bv the aid of Billings anil 
Barrande, that his system embraeetl strata that were pre-Pots- 
tlam. The question whether the details of his scheme were 
right, or whether he "blundered" in interpreting the coirplcx 
1 Am. Journ. Sci. (3) iii, 468. 
2 Mr. Sedg-vvick found similar difficultie;? in the stratigraphy of tlie 
Cambrian, and introduced some changes .subsequent to his Hrst descrip- 
tion. 
