416 J. D. Dana — Brief history of Taconio ideas. 



and at the following meeting in 1847, Mr. S. S. Haldeman, 

 the chairman of the committee, made an adverse report.* A 

 reply from Mr. Hall appeared in this Journal in 1848. f 



The discussion was continued at the first meeting of the 

 American Association for the Advancement of Science (an 

 expansion of the Association of American Geologists and Nat- 

 uralists), in 1848, when Prof. Emmons read a paper entitled 

 " On the identity of the Atops trilineattcs and the Triarthrus 

 Beckii, with remarks upon the Elliptocephalus asaphoides" 

 in which he gives a full comparison of characters and also 

 points out the differences between the latter species and either 

 of the allied genera Olenus and Paradoxides.% 



The following year, 1849, a new advocate of the views of 

 Eogers and Mather, in opposition to Emmons, appeared, in 

 Mr. T. S. Hunt, then of the Geological Survey of Canada, who 

 presented that year to the American Association for the 

 Advancement of Science, at its second meeting in Cambridge, 

 an abstract of the Geological Report of Canada for the year 

 1847-8. § But it does not appear that either Mr. Hunt, or any 

 one connected with the Canadian survey, had made the Taconic 

 region a subject of investigation. 



1855 to 1859; Phase III.— In the year 1855, Prof. Emmons 

 made, in his new volume entitled ''American Geology," his 

 third presentation of the Taconic System. || The chief changes 

 introduced are the following : (1) The fossiliferous portion of 

 the system is now called the Upper Taconic, and the rest the 

 Lower Taconic ; (2) the Sparry and Stockbridge limestones 

 are brought together as one formation; (3) the synclinal char- 

 acter of Greylock is first recognized and figured ; and (4) 

 extensions of the system to new localities are mentioned. 



The order of succession in this third phase of the system 

 and the true equivalents are as follows : 



Taconic System in 1855. Equivalents. 



TT (2. Black slate of Bald I. Cambrian. 



Upper ) Mountain . 



laconic. ^ j Taconic slate. Ill, I. Hudson slates and Cam- 



brian. 

 (3. Magnesia slate. HI. Hudson slates. 



Lower J 2. Stockbridge lime- II. Lower Silurian. 



Taconic. ) stone. 



[ 1. Granular quartz. I. Cambrian. 



* S. S. Haldeman, this Journal, II, v, 117, 1848. At the same meeting, in 

 1847, Prof. C. B. Adams, of the Vermout Geological Survey, read a brief note on 

 the Taconic rocks of Addison County, Vt., in opposition to the system. 



f James Hall, this Journal. II, v, 322, 1848. 



\ E. Kmmoi.s, Proc. Amer. Assoc, for 1848, vol. i, p. 16. 



§ T. S. Hunt, Proc. Amer. Assoc, for 1849, vol. ii, p. 325, and this Journal, II, 

 ix, 12, 1850. 



\ Occupies pages 1 to 122 of Part II of the American Geology, 8vo, Albany, 1855^ 



