Related Formations, 



17 



discussion are situated. His official report contains the above. On 

 page 366 he says : 



" The division of the fossiliferous rocks of the first geological dis- 

 trict, as proposed in the Fourth Annual Report (1840), was one of con- 

 venience, and founded in nature, and as affording means of easily 

 tracing the groups of strata. This division of the rocks has been 

 substantially sustained by the Board of Geologists, the Hudson slate 

 series being divided into the Champlain division and Taconic sys- 

 tem, etc." 



Prof. Mather recognized the presence of the lower members of 

 the Champlain division in the confused strata on the east side of the 

 Hudson. He established the Hudson River group on the west side 

 and then referred the strata on the east side, in many places with 

 doubt, to it. The correctness of the original reference and its accept- 

 ance by the Board of Geologists is a fact in the history of the 

 survey. 



The use of the term Lorraine group is not admissible, as the term 

 Hudson River antedates it, and Lorraine was placed as a synonym 

 by the Board of Geologists who agreed upon the nomenclature of 

 the New York system of rocks. The facts presented by Prof. 

 Mather upon which the term Hudson River group was established, 

 have not been materially changed by subsequent investigations. 

 Mr. Dale's discovery of an old locality given by Mather and Mr. 

 Ford's verification of the presence of a lower member of the Cham- 

 plain division by palseontological evidence, being the two instances 

 cited in the article by Prof. Hitchcock. 



In a very interesting paper on the " Hudson River Age of the 

 Taconic Schists" (^Amer. Jour. Sci., Arts'i^^. 375-388, May 1879), 

 Prof. J. D. Dana shows that the Taconic schists are, according to 

 the evidence presented, of the age of the Hudson River group and 

 that the five limestone belts mentioned are of Lower Silurian age, 

 thus ar] iving at conclusions partially coinciding with those of Prof. 

 Mather. 



Trans, a;.] 



3 



