424 ANNALS NEW YORK ACADEMY OF SCIENCES 



In the absence of the Eecording Secretary, Professor D, W. Johnson 

 was appointed Secretary pro tern. 



The minutes of the last meeting were read and approved. 



There being no further business to transact, the Academy then ad- 

 journed. 



D. "W. JOHXSOX, 



Secretary pro tern. 



SECTIOX OF GEOLOGY AXD MTXEEALOGY 



•i October, 1915 



Section met at 8 :20 p. ai. . Vice-President Charles P. Berkey presiding. 

 The minutes of the last meeting of the Section were read and approved. 

 The following programme was then offered : 



R. J. Colony, Peteographic Methods Applied to the Study of 

 Cemext. 



Summary of Paper 



Mr. Colony said in abstract: In a previous paper fPetroorapliic study 

 of Portland cement: School of Mines Quarterly, 5-XXXYI, 191-1) the 

 character of cement clinker has been briefly discussed from a petrographic 

 standpoint, and the fact emphasized that while the components of the 

 clinker, Alit, Belit and Celit, have a mineral identity, they are, indi- 

 vidually, complex solid solutions composed of two or more components 

 each; these solid solutions may vary within the limits of solubility of the 

 solute in each case, and it seems quite likely that such variability may 

 affect the resulting cement. 



It was also pointed out that when cement is gaged with water the first 

 products of the reaction which follows are primary crystalline calcium 

 hydrate with spherulitic habit; a multitude of minute, formless isotropic 

 grains judged to be hydration products, and a greater or less amount of 

 primary colloid of uncertain composition which co-precipitates with the 

 spherulitic calcium hydrate, the resulting structure being minutely lamel- 

 loid. A secondary reaction then takes place between these components, 

 which form a dense, structureless constituent, called the amorphous con- 

 stituent proper. 



It was also stated that secondar}' calcium hydrate which later forms in 

 various situations, especially in voids and cavities, was hexagonal, uniaxial 

 and optically negative. 



Further study of numerous thin sections of cement and concrete, in 



