TABLE OF CONTENTS. xiii 



PAGE 



Edge-runners 243 



Centrifugal grinders 243 



Ball-grinders 243 



Impact pulverizers 244 



Separating systems 245 



Power required in grinding 246 



Fineness actually attained 246 



Packing weights 248 



Costs of manufacture 248 



Cost of raw material 248 



Labor costs 248 



Fuel costs 249 



Total costs per barrel 249 



References on manufacturing methods 250 



CHAPTER XIX. 



COMPOSITION AND PROPERTIES OF NATURAL CEMENTS. 



Chemical composition of natural cement 252 



Georgia 252 



Illinois 252 



Indiana-Kentucky 252 



Kansas 254 



Maryland 254 



Minnesota 254 



New York 256 



North Dakota 259 



Pennsylvania 259 



West Virginia-Maryland 259 



Wisconsin 260 



Belgium 260 



England 260 



France 260 



Germany- Austria 261 



Physical properties of natural cements 263 



Weight and specific gravity 263 



Rapidity of set 263 



Effects of gypsum or plaster on natural cements 264 



Effect of salt on strength 267 



Tensile strength 267 



Effect of sand on tensile strength 272 



Compressive strength 274 



Effect of heating 275 



Ratio of compressive to tensile strength 275 



Modulus of elasticity 277 



