CHAPTERS ON THE CEMENT INDUSTRY 869 



Cliarles S. Proseer^ has determined that the entire section shown 

 consists of the following rocks, the datum being taken as the 

 level of the Cobleskill at the suspension footbridge. 



0-32 feet covered with soil. 



32-56 feet green, argillaceous shales (Clinton group). 



56-63 feet dark gray, massive limestones (Niagara group). 



63-102 feet gray argillaceous and magnesian limestones (Water- 

 lime group). - 



102-3 3i feet dark blue limestone (Tentaculite group). 



133i-44|- feet limestones (transitional Tentaculite Penta- 

 merus). 



144^-68 feet very massive gray limestone (Pentamerus group). 



The limestone used in Portland cement manufacture is obtained 

 from the Pentamerus and Tentaculite beds, exposed in quarries 

 just west of the station, on the northern side of the railroad track, 

 while the Clinton and Waterlime beds above noted are shown 

 only in the lower quarries. Partial analyses of these upper lime- 

 stones, quoted by Prosser as having been made by C. A. Schaeffer 

 follow: 



Si Og Ca CO^ 



Tentaculite limestone i. ......... .. 1.48 95.Y5 



Pentamerus limestone i 4 . 12 93.68 



Another sample analyzed by Schaeffer gave: 



sio 3 1 . 2r 



• I .73 



Al ,0s 



Fe.Oa ) 



CaCOg , 97.24 



MgCOg 1.39 



SO3 tr. 



As no complete analyses of the materials actually used for 



Portland were obtainable, I have included this analysis, as the 



1 18th an. rep't N. Y. state geol. p. 67. 



