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people, and needed for their various structures greater economy of
material than was compatible with large blocks of stone, especially for
such as were carried to great altitudes. The arch supplied this want,
and is perhaps the greatest invention ever made in architecture. No
instance of its adoption occurs in the construction of Greek edifices
before Greece became a part of the Roman empire. Its application dates
back to the Cloaca Maxima, and may have been of Etrurian invention. Some
maintain that Archimedes of Sicily was the inventor of the arch; but to
whomsoever the glory of the invention is due, it is certain that the
Romans were the first of European nations to make a practical
application of its wonderful qualities. It enabled them to rear vast
edifices with the humblest materials, to build bridges, aqueducts,
sewers, amphitheatres, and triumphal arches, as well as temples and
palaces. The merits of the arch have never been lost sight of by
succeeding generations, and it is an essential element in the
magnificent Gothic cathedrals of the Middle Ages. Its application
extends to domes and cupolas, to floors and corridors and roofs, and to
various other parts of buildings where economy of material and labor is
desired. It was applied extensively to doorways and windows, and is an
ornament as well as a utility. The most imposing forms of Roman
architecture may be traced to a knowledge of the properties of the arch,
and as brick was more extensively used than any other material, the arch
was invaluable. The imperial palace on Mount Palatine, the Pantheon
(except its portico and internal columns), the temples of Peace, of
Venus and Rome, and of Minerva Medica, were of brick. So were the great
baths of Titus, Caracalla, and Diocletian, the villa of Hadrian, the
city walls, the villa of Mecaenas at Tivoli, and most of the palaces of
the nobility,--although, like many of the temples, they were faced with
stone. The Colosseum was of travertine, a cheap white limestone, and
faced with marble. It was another custom to stucco the surface of brick
walls, as favorable to decorations. In consequence of the invention of
the arch, the Romans erected a greater variety of fine structures than
either the Greeks or Egyptians, whose public edifices were chiefly
confined to temples. The arch entered into almost every structure,
public or private, and superseded the use of long stone-beams, which
were necessary in the Grecian temples,