NIAGARA AND LOWER HELDERBERG GROUPS. 121 



gists. Professor Eogers, in a paper upon Niagara Falls, pub' 

 iislied, I believe, in 1882, takes this view of the relations of 

 these formations, and includes also the limestone of Black 

 Rock under the same designation. It is not surprising that at 

 that period, when no critical examinations had been made, 

 when we had no knowledge of palaeontology as a guide in the 

 more obscure and difficult points, that great surface features 

 should have been taken as guides in the determination of geo- 

 logical formations. It happened in this case that the great 

 escarpment of the Niagara at Lewiston and Queenstown was 

 regarded as the extension of that of the Helderberg and the 

 south side of the Mohawk valley. The limestone of Black 

 Rock, though so far separated from Niagara, was regarded as 

 a part of the same ; the features in the west being more sub- 

 dued, as was supposed. 



This, in brief, was the condition of our knowledge and be- 

 lief regarding these formations at the beginning of the New 

 York Geological Survey, and for some time afterward. 



The one horizon which, above all others, was at that time 

 regarded as fixed beyond question was that of the salt-bearing 

 strata. This formation, at its base bearing a great thickness 

 of red and mottled shales and marls, succeeded by gray, ash 

 or drab colored beds of similar characters, and finally hard 

 beds of limestone, was regarded as clearly defined from Salt- 

 springville in the Mohawk valley, by way of Syracuse, Mon 

 tezuma, and thence westward along the base of the Limestone 

 Terrace from Rochester to Lewiston. 



Throughout this entire extent salt springs had been discov- 

 ered, and brines of varying and different qualities were known 

 to exist. No doubt of the nature, age or identity of the for- 

 mation, from Herkimer county to the Niagara river at Lewis- 

 ton, had ever been expressed, or, so far as I know, entertained 

 by any one. Now, though this may seem irrelevant to the 

 question before us, it nevertheless lies at the foundation of the 

 error then prevalent, regarding the Niagara and Helder- 

 berg formations ; and is intimately connected with the greater 

 error now sought to be revived in the paper under consider- 

 ation. 



It was not until the close of the field work of 1838 that this 

 question came before the assembled members constituting the 

 Commission of the New York Geological Survey. The young- 

 16 



