682 NEW YORK STATE MUSEUM - 



central "New York, in tlie Lehigh valley of Pennsylvania, in the 

 James, Potomac, and Ohio river valleys, the result being that 

 natural rock cements were made at all these localities at a com- 

 paratively early date. 



In 1899 the total production of natural rock cement was 

 9,868,179 barrels. This was unequaled by any other country, 

 the nearest approach to it being France, with six million to seven 

 million barrels a year of both hydraulic lime and hydraulic 

 cements. The United States is probably in the lead, owing to 

 excellence and abundance of raw materials. The greatest pro- 

 duction was in 1892; since then both product and price have de- 

 creased, one reason for this being the increase in the Portland 

 cement industry. 



The American natural cements are made from ' argillaceous 

 limestone of varying geologic age. In western ISTew York state 

 they are mostly derived from the waterlime beds at the top of 

 the Salina. Those of the Posendale region are from the base^ 

 of the lower Helderberg. In Wisconsin, natural rock cement is 

 made from rocks of Devonian age near Milwaukee; and in Ken- 

 tucky there is an important cement-producing area near Louis- 

 ville. In Pennsylvania thick cement beds are found in the 

 Trenton limestone of the Lehigh valley, but magnesian hydraulic 

 limestones are also known in the Carboniferous. In Wisconsin 

 cement rocks are quarried near Milwaukee, belonging to the 

 Hamilton period. In Illinois near Utiea and La S«lle , cement 

 is obtained from the Calciferous limestone. The rocks of Mary- 

 land are also Silurian. 



The deposits at Rosendale (N. Y.) are perhaps the most im- 

 portant; but those of the Lehigh valley in Pennsylvania are re- 

 markable for their purity and extent. 



The hydraulic limestones, or natural rock cements, can be 

 divided into two classes based on the ^diflfereiit amounts of car- 

 bonate of magnesia' which they contain. In one class it does not 

 exceed 3^ or 4.^, while in another 15^ to 35^ is found. Most of 

 the hydraulic limestone of the United States is magnesian, but 



