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HISTORY OF ENGINEERING.

Book I.

Temple of Fortuna Seja, which formed a part of his golden House. Domitian had the wallsof the arcades, through which he alone passed, inlaid with it, that he might observe whatwas passing behind him. This was possibly the Marino Salino.

Of the coloured marbles, the most famous was that of Carystos , the modern Castel Itosso,a city of the Negropont; it has a greenish colour, with lines and undulations, resemblingthe waves of the sea : the quarries at Mount Ocha were called Marmarion : it was muchused in Roman edifices, and was one of the earliest marbles introduced into that city,and became very common in the time of the emperors. The columns of the templeof Antoninus and Faustina are formed of it, and in consequence of their resemblance to theeipollo (onion) are called Cipollino. It was used also for pavements ; the Basilica of Con-stantine , or temple of Peace, has slabs of it; there are many columns still among theruins, and in modern churches, made of the Cippolino.

The Lacedemonian marble is of a green colour and very hard ; it is found at Taigeto inLaconia, and its quarries were used in the time of Strabo under Augustus and 'liberius ;it is likened by some to the emerald and to the verde antique ; it bore some resemblance tothe Thessalian, and from a passage in Pausaniaswe learn that at a village in Laconia , at thefoot of Taygctus, quarries of marble or hard stone were worked, which being cut into formwere polished by immersion in the river, and became so beautiful, that they were appliedto adorn the temples of the gods. The marble we call serpentine is mentioned byStrabo, and is the ophite of Pliny . The qualities which the ancient writers quotedgive to this marble agree with the serpentine, which is of a grassy colour and very hard,being especially adapted for tessera?; such is that of the grotto of the nymph Egeria.Lampridius says that Ileliogabalus lined the arcades of the Palatine with Lacedaemonian marble and porphyry, that is, serpentine and porphyry, a method improved upon by AlexanderSeverus , from whom it was afterwards called Opus Alexandrinum, and was in great useduring the decline of the arts, most of the early churches being cased with it : one of thefinest examples of which is that of S. Giovanni and Paolo, on the Caclian mount, whichwas decorated in the fourth century. The ancient writers mention that the Lacedaemonian marble was used for incrustation, but do not say it was employed for the shafts of columns :in the baptistery of the Lateran , before the chapel of St. John the Baptist, are two columnsof red porphyry, of the Corinthian order, with capitals and bases of Lacedaemonian marble.Serpentine in small pieces is very common in Rome , and was much employed for pavementin consequence of its hardness. In the baths of Antoninus , the pavement was composed ofsmall tessera;, or coarse mosaic, of Laceda?monian and Numidian marble, viz. serpentine andgiallo antique.

The Atracian or Thessalian was another variety of green marble, obtained from the banksof the Peneus, 10 miles from Larissa. Paolus Silenziarius says it was a green marble, re-sembling the emerald, mixed with deep blue spots, a light black and snowy white, and wasmuch prized by the Greeks. This is no doubt the verde antique, specimens of which arein the Basilica of the Lateran .

The marble of Chios , from the island of that name, is of various colours, the light blackmost predominating, resembling the African. The Arch of Drusus on the Via Appia hascolumns of this marble ; they are also found in the Pantheon, and in the Basilica Ulpia ofthe forum of Trajan, which was partly paved with it.

The Phrygian marble , called Pavonozzetto, very much esteemed, was found near Docimeain Phrygia . It is white, with purple veins. Twenty-four columns of this marble decoratedthe Basilica of Paulus Emilius in the Roman forum, and now form the chief ornament ofthe Basilica of Ostia. This marble is common at Rome , being found in almost all the churches.The figures of the Prisoner Kings on the arch of Constantine arc made of it, as are thestatues found among the ruins of the forum of Trajan. From a passage in Strabo we learnthat quarries which at first only yielded small masses of this marble afterwards producedcolumns of one block, and notwithstanding the distance from the sea they were transportedto Rome . During the decline it was used in the decoration of the churches, particularly byJustinian at S. Sophia at Constantinople .

The Lydian marble was of two kinds, one red mixed with a pale colour, which wenow call red brescia ; the other black, called by the ancients basinite and chrysite, bothfound in Lydia, a province of Asia Minor .

Nero Antico, or black, quarried at Tenarus, a promontory of Laconia , has a beautiful sur-face, and is at the present day highly prized. Columns of it at Rome are to be met with asearly as the time of Augustus, at which time it was much used in Greece .

Of the Timber used by the Romans. Great attention was paid in the selection of timberfor construction, and all belonging to the fir species were usually cut down when theyput forth their young shoots, that the bark might be more readily stripped. Themaple, the ash, the elm, the lime, and the oak were felled in winter, the latter beingconsidered subject to worm if cut down in the summer. Vitruvius prefers the autumnfor felling of timber; for the fruits being ripened, and the leaves dry, the roots draw