AMERICAN GEOLOGY — DECADE OF 1840-1849. 377 



the water having only a very moderate flow; that subsequently the 

 country was raised en masse to a height of from 300 to 1,000 feet. 

 This elevation he conceived to have been sudden, causing - strong cur- 

 rents to flow through the channels communicating with the ocean, 

 depositing sand, gravel, and bowlders in their eddies. (See further 

 on p. 394.) 



He also believed that the limestones, that are frequently crystal- 

 line white and variegated marbles in the western part of Vermont, 

 Massachusetts, and Connecticut, were metamorphosed forms of the 

 Mohawk limestone and Calciferous sandstone; that they were, in short, 

 rocks of the Champlain division, but much more highly altered and 

 modified by metamorphic agency than Taconic rocks. It should be 

 said that, while using the term " Taconic " and describing the rocks and 

 their distribution, Mather stated distinctly that he regarded the Cham- 

 plain division and the Taconic systems as the "same rocks, the latter 

 somewhat modified in character by metamorphic agencies." 



In describing the Taconic rocks separately I have yielded to the opinion of my 

 colleagues who have considered them as interposed between the Champlain division 

 and the primary. I can discover no evidence of any such interposition, but consider 

 them as rocks modified by metamorphic agency and intermediate in their character- 

 istics between the unchanged rocks of the Champlain division and those still more 

 altered and crystalline along the eastern line of New York and in the western part 

 of Vermont, Massachusetts, and Connecticut. (See also under. The Taconic Ques- 

 tion, p. 659.) 



The trap rocks of the Hudson Palisades he looked upon as ancient 

 lavas that had flowed through the rock fissures in dikes while this 

 part of the continent was still beneath the waters of the ocean. These 

 rocks and the associated red sandstones he rightly believed to be of 

 the same age as those of Connecticut, Virginia, and Nova Scotia, 

 though he wrongly put down the Lake Superior red sandstone as also 

 a contemporaneous deposit, 



Emmons, who had charge of the second district, presented his 

 results in a quarto volume of 437 pages, with 17 plates and colored 

 sections. It was during this survey that he proposed the name New 

 York Transition system for the stratigraphic series of 

 N^Tvork. work in rocks extending from the primary up to and including 

 the Old Red sandstone, Subsequently this name was 

 shortened by the omission of the word transition, and in this form 

 was adopted by the other members of the survey. He classified the 

 rocks of this system in ascending order as, first, Champlain division; 

 second, Ontario division; third, Helderberg division; and, fourth, Erie 

 division. The first, or Champlain, division included the Potsdam 

 sandstone, the Calciferous sand rock, the Chazy and Birdseye lime- 

 stone, the Isle la Motte marble, Trenton limestone, and Loraine shales. 

 The second, or Ontario division, included the Medina sandstone, green 

 shales, and oolitic iron ore, now known as the Clinton ore, the Onon- 



