846 NEW YORK STATE MUSEUM 



mixture tlien burned in suitable kilns at a higher temperature than 

 that arrived at in the manufacture of any except the most refractory 

 grades of clay products proper, the object of the burning being to 

 cause the component elements of the mass to unite — for which 

 reason the material in burning has to be brought to a condition 

 of sintering — the new compounds being calcic silicates and calcic 

 aluminates. The burned mass is then finely ground, after which 

 most of it will pass through a 100 mesh sieve, and a large percentage 

 of it through 200 mesh as well. This ground material when mixed 

 with water has excellent hydraulic properties, the mass setting into 

 a stonelike condition. It has been found by ISTewberry that in the 

 best cements the percentage of lime is equal to 2.8 times the silica 

 plus 1.1 times the alumina. 



ISTew York, with her great series of Paleozoic limestone forma- 

 tions, her Quaternary marls, and her clays and shales ranging in 

 age from the Silurian to the Quaternary, is liberally supplied with 

 raw materials to support a flourishing portland cement industry, 

 and indeed there are already seven factories in operation in the 

 state, while an eighth one is nearly completed, and several more 

 are in contemplation. 



The characters of the different limestone formations are discussed 

 in the bulletin already referred to, and an idea of the nature of the 

 clays and shales can be gained from the analyses given in different 

 portions of this bulletin. Tor farther reference there are given 

 herewith some additional analyses of clays and shales used at differ- 

 ent localities in the United States for the manufacture of portland 

 cement. 



Up to a few years ago most of the portland cement used in the 

 United States was imported from foreign countries, but at the 

 present time it is being found that it is possible to make just as good 

 hydraulic cement in this country, and the local production, already 

 large, is increasing annually, and prejudice against it, which has 

 unfortunately existed, is slowly disappearing. 



