HISTORICAL SKETCH No one knows when, where, or by whom con crete was invented or first employed. Its use as a material of construction dates back to the dim antiquity of prehistoric times, and examples of the ancient craft have come down to us with practically undiminished strength which have withstood the bombardment of nature's forces through all the centuries. Orpheus himself, whose lyric strains animated the very stones of which the walls of Thebes were built, may, for all we know, have been merely a skilled worker in concrete. Certain it is, however, that long before the dawn of authentic history, at a period back beyond the prying curiosity of scientific research, and while the earth was still young, people lived who knew a great deal about ce meat and its adaptability to the various needs of construction, as well as its wonderful powers of resistance to the disruptive action of natural forces.
The ancient Egyptians understood the use of hydraulic cement. It has been proved that in some of the marvelous constructions which still endure as monuments of their engineering skill, they used a porous lava possessing hydraulic properties and containing the basic element necessary to making of cement somewhat similar to the Portland cement of the present day. Many of the sarcophagi in which they placed their dead were made of artificial stone. The majestic Pyramids which for over 4,000 years have reared their stupendous forms above the desert, and which still tranquilly laugh de fiance at the ravages of time, were built in part of concrete. It is now generally conceded that in the construction of their upper tiers, at least, concrete was the material employed; and the massive blocks of stone that have baffled past ages by the mystery of their transportation to such elevations were probably borne to their destination by the pailful, and formed directly in place. Evidence that these blocks are of man's formation is found in the fact that break ages in some of them have revealed small pieces of wood embedded in the mass.
The Romans constructed many miles of high ways and walls and aqueducts from hydraulic cements, which they also used to some extent in the building of their residences and temples; and many examples of their work still extant not only bear witness to the high standard of civilization attained under the ancient Empire, but also afford unquestionable evidence of the permanent character of the material composing them.
The word "Concrete" is itself of Latin or igin, meaning "grown together" ("con," to gether; and "crescere," to grow), and implies a body formed by the coalition of separate par ticles into a solid mass.
Roadbeds of concrete resounded to the thun dering tread of the Roman legions as they went out to or returned from their campaigns of world-wide conquest. The famous Appian Way, over which the Apostle Paul entered Rome, as described in the Book of Acts in Holy Writ, was underlaid with cement concrete and topped with paving stones. The latter have been worn away, but the concrete is still intact, just as when the Romans laid it. This was the oldest of the Roman highways, having been started by Ap Pius Claudius Caius about the third century be fore the Christian era. It extended from Rome to Capua, and later was built to Tarentum and Brundisium, in far Southern Italy. The aque ducts which supplied the imperial city with water were built without reinforcement, and are still in almost perfect condition. The cement lining of the Pont du Gard at Nismes, in Southern France, a Roman aqueduct built in the first cen Jury A. D., is still hard and smooth as when first put in place. The pools of King Solomon, nine miles from Jerusalem, were built wholly of con crete, and still furnish water for the city. Many residences of the Roman nobles were con structed of concrete unfaced by brick or stone; and wood framing was used in casting the walls, in much the same manner as wooden forms are used in concretevonstruction to-day. The Col osseum was built on piers and foundations of concrete; and Professor Middleton, in his work on "Ancient Rome," tells us that the entire up per floor of the Antrium Vesta was formed of one great slab of concrete fourteen inches thick and having a span of twenty feet, supported on edges, but having no intermediate supports. The Pantheon of Rome, a circular temple origin ally dedicated about the time of Christ, in the reign of Augustus, has a dome 142 feet in diam eter, constructed mainly of concrete, and still in perfect condition after 1900 years of service. The Aurelian wall about the city, over ten miles in length, still standing, was built of the same material. An English writer has said: "In strength and durability, no masonry, however hard the stone or large the blocks, could ever equal these Roman walls of concrete, for each wall was one perfect coherent mass, and could be destroyed only by a laborious process like that of quarrying hard stone from its natural bed." In the recent construction of a tunnel under part of the old city of London, England, the workmen uncovered Roman cement which had been placed over 800 years before, so hard that it turned the edges of the hardest cold steel chisels.