COMPOSITION AND PROPERTIES OF NATURAL CEMENTS. 259 



North Dakota. The Pembina cement is a highly satisfactory prod- 

 uct, of high index and low magnesia, much like the Chickamauga 

 cement of Georgia. 



TABLE 118. 

 ANALYSES OF NATURAL CEMENT, NORTH DAKOTA. 



1-8. Analyses of natural cement, Pembina Cement Co., Milton, N. D. 



Pennsylvania. The Lehigh district natural cements are low in 

 magnesia. As marketed they are often very badly mixed products. 

 Portland cement is usually added, while adulteration with coke and 

 ground limestone is not unknown. 



TABLE 119. 

 ANALYSES OP NATURAL CEMENTS, LEHIGH DISTRICT, PA. 



1. Quoted by Smith. Mineral Industry, vol. 1, p. 50. 

 2 i. " " 



3. "Bonneville Improved." Tests of Metals at Watertown Arsenal, 1901. 



West Virginia-Maryland. These cements are fairly low in mag- 

 nesia and usually of very high index. 



