After being wet with water it hardens into stone, and it was given the name “Portland” because, when first manufactured in England, and mixed with sand and stone, it resembled a celebrated building stone called Portland, which was obtained from the Isle of Portland. Compared with other American industries, the manufacture of Portland cement is of recent origin. Formerly all Portland cement was brought from foreign countries. After successful manufacture became established in this country, however, the industry advanced with great rapidity. A few years ago the entire United States did not use as much cement as is now used in any one of our large cities. At the time these facts were written (1914) the manufacturers were making more than 90 millions of barrels a year. What Is Cement Made Of? Portland cement is composed chiefly of lime, alumina and silica. It is manufactured from rocks, marl, clay and shale containing these ingredients. If any one of them is lacking in the raw material as it is taken from the earth, it is supplied during process of manufacture. The greatest cement district in America is in Pennsylvania, and is known as the “Lehigh District.” A rock containing proper constituents for making Portland cement was found there in vast quantities, and for a number of years the Lehigh District was the center of the industry. In time it was found that certain clays, marls and shale could also be manufactured into Portland cement, and thus mills have been erected in all sections of the United States. One of the largest companies in the United States found that cement could be manufactured from a combination of blast-furnace slag and limestone, and this is now made by the company in large quantities, the product being a true Portland cement. What Is Concrete? Portland cement is the strongest and most lasting of all modern mortars or binding materials. When mixed with sand and stone the resulting mixture is called concrete. Being a plastic material when first mixed, it cannot be used as we use brick or stone, but must be poured into molds or forms, which hold it in place until it hardens into rock. It may be cast in any form or shape, and thus it is useful for a vast number of purposes. It will harden under water, and time and exposure to the elements merely increase its strength. The most common form in which it is used, one familiar to everybody, is in the construction of sidewalks. It is used in all great engineering projects, such as the building of dams, bridges, retaining walls, sewers, subways and tunnels. Being fireproof, large quantities of it are used in buildings and likewise on our farms, where it is extremely valuable as an enduring and sanitary material. What Is Cement Used For?