H. P. Cushing — Lower Paleozoic Pocks of New York. 141 



Emmons did not use the term Black River at all, though 

 the Chazy was practically confined to his district, and the 

 remainder of the formation was as fully shown as in the Third 

 district. It is, however, quite differently shown. He plainly 

 did not sympathize with the term, and probably objected to 

 the inclusion of Chazy in it. The above quotation also indi- 

 cates that Vanuxem did not feel sure of the propriety of 

 extending the term to cover the Chazy. Emmons used instead 

 the terms Chazy limestone, Birdseye limestone, and Isle la 

 Motte marble, and did not sanction the use of a group term 

 to include the three. Emmons correlates the 7 foot tier at 

 Watertown with the black limestone at Glens Falls, Chazy, 

 and Isle la Motte. But the Glens Falls, Chazy and Isle la 

 Motte occurrences represent the horizon of the chert beds 

 rather than that of the 7 foot tier. 



Vanuxem's broad use of the term Black River has been con- 

 sistently followed by some writers since, and notably so by the 

 Geological Survey of Canada. 



In the first volume of the Paleontology (1847) Hall seems to 

 advocate a quite different use of the term, though he nowhere 

 makes an explicit statement to that effect and there is little 

 evidence that he had any detailed acquaintance with the Water- 

 town section. The most specific statement made is at the bottom 

 of p. 41, where he says that Murchisonia perangulata " occurs 

 in a siliceous, cherty mass of the Birdseye limestone .... 

 near the upper termination of the rock at Watertown." Now 

 there is little or no chert in the Lowville proper and it seems 

 that the reference here can only be to the cherty beds just 

 under the 7 foot tier, which Cushing and Ruedemann mapped 

 with it as a single lithologic unit. If Hall regarded the chert 

 beds as Birdseye he must have restricted the use of Black River 

 substantially to the 7 foot tier. 



Since the appearance of Hall's report there has been uo use 

 of the term Black River in New York in the comprehensive 

 Vanuxem sense. A usage has grown up however which is not 

 so sharply restrictive as that of Hall, namely that of calling 

 everything Black River which lies between the Lowville and 

 the Trenton. As thus used the term had no precision, since it 

 had not been determined just what was included in the Low- 

 ville. Our recent work about Watertown, which we extended 

 so as to include study of the type section at Lowville, gave pre- 

 cise definition to the Lowville formation for the first time.* 

 At the same time a very complicated and difficult nomencla- 

 torial problem was presented. If we included the chert beds 

 with the 7 foot tier as Black River, in accord with present 

 New York usage, and excluded them from the Lowville, as 

 the Watertown sections seemed to suggest we should do, diffi- 



*Bull. 145. N. Y. S. M., pp. 79-86. 



