CEMENT RESOURCES: SELMA CHALK. 



49 



Physical Character. The Selma Chalk is soft, and may there- 

 fore be easily and cheaply quarried and pulverized. In this re- 

 spect it is probably the most satisfactory cement material in 

 the United States. Enough should be quarried in dry weather, 

 hr/ever, to carry the plant entirely through rainy seasons, for 

 the chalk takes up water easily, and the expense of removing 

 tfiib absorbed water would be considerable. 



Accessibility to Clay: Clay beds are adajcent to, and in 

 some cases immediately overlying, the Selma chalk. These 

 clays, which are probably residual in origin, are in general very 

 suitable for use, in connection with the limestone, in making 

 up the cement mixture. It seems probable that in no case will 

 a plant, located on the Selma chalk, have to go more than a few 

 hundred yards to obtain the necessary supply of clay. 



Table VI. Composition of Clays near Selma Chalk. 



*Trace. 



Besides the residual clays above noted, and which are 

 nearly everywhere available over the chalk, it seems entirely 

 practicable to use mixtures'in varying proportions of the purer 

 forms of the chalk as shown in analyses of Table V, Nos. i to 

 9, with more argillaceous varieties such as those shown by 

 analyses 10 to 14. In this way a proper cement mixture might 

 be obtained without the use of clays, where they were difficult 

 to obtain. 



