LIME AND CEMENT INDUSTRIES 693 



as compared with, hydraulic limes, and differs from the Posendale 

 type of cements in developing a much higher tensile strength, 

 and being invariably very low in magnesia. 



Portland cement was discovered by Joseph Apsdin, of Leeds 

 (Eng.), who desired to make an artificial cement that would re- 

 place natural hydraulic cements. It received its name because 

 it hardened under water to a mass resembling Portland stone. 



With very few exceptions, Portland cements are artificial mix- 

 tures, and many of the so-called " natural " Portland cements 

 made in the United States and Germany are not strictly such. 



The use of hydraulic cement is very old; still the Portland 

 cement industry has been developed entirely in the present cen- 

 tury. In this country it is widespread and active, but the output 

 is not large enough to supply the home markets, for the growth 

 of the Portland cement industry has been greatest abroad up to 

 the last three or four years. 



In England Portland cement is made chiefly in the Thames and 

 Medway districts, where white and gray chalks and river mud 

 are used. In Germany the Portland cement industry is devel- 

 oped chiefly in the northern part of the empire, the region about 

 Stettin and the Rhine valley being important centers of produc- 

 tion. In these localities the materials used are chiefly chalks 

 and marls which are mixed with clay. In southern Germany 

 and Austria as well as Switzerland hard limes are used, in north- 

 ern France marls, chalks and clays are the materials employed. 



The enormous development of the Portland cement industry 

 in the United States, as well as the amount of material used, 

 both native and foreign, may be judged from the following table, 

 which gives the production of Portland cement in the United 

 States from 1891 to 1898 inclusive and also the imports for these 

 years. These imports include shipments from Germany, Bel- 

 gium, France, England and Denmark. 



The statistics are taken from the volume, Mineral resources, 

 21st ann. rep't United States geol. sur. (see pi. 12). 



