Chap. IV.
ROMAN.
105
small, irregular formed stones were thrown together, without any apparent order. In thelarge vaults of the baths of Caracalla , a species of porous lava was used, which was as lightas pumice-stone. The vaults of the baths of Diocletian, the Coliseum, and the temple ofMinerva Medica, are so constructed. These vaults, as well as those of Caracalla and theVilla Adriana , were turned on centres, formed of boards laid longitudinally, the marks ofwhich may be seen where the stucco which finished their soffites has peeled off. On theboards was first spread a thickness of mortar of more than a foot, on which was laid flattiles 2 inches in thickness, and nearly 2 feet square. These tiles were covered by others,and a second layer of mortar, but not so thick ; the tiles were about 8 inches square, and
inch in thickness, laid in courses in such a manner as to break joint with the first layer.
Of the Forum and Basilica . No city of the Roman empire, however small, was withoutits place of assembly and its market for the sale of all sorts of goods. 'The forum wasoriginally intended for this purpose, and was surrounded by a colonnade, over which was agallery or covered portico, from whence the gladiatorial shows might be seen, which wereexhibited before the introduction of the amphitheatre. Trades were carried on under itsporticoes, and at the end of it was the senate-house; the curia, where meetings on solemnand religious matters were held, the comitia for the common people, the treasury, and otherpublic buildings, adjoined it. Such was the Roman forum, and that at Pompeii , the size ofwhich was proportioned to its population : its width was usually two-thirds its length ;the columns of the upper colonnade were made one-fourth less than those below, followingthe order of nature, which in the fir, cypress, and pine, preserves a gradual diminutionthroughout their height.
The basilica, in which all legal business belonging to the city was transacted, had itsprecise form and arrangement. Vitruvius , who constructed one at Fano, gives its distri-bution, and describes what is necessary for its interior.
The middle vault between the columns was 120 feet in length, and 60 feet in width ;the portico, or space between the outer wall and columns being 20 feet in width. Theheight of the columns,including their capitalsand bases, 50 feet, andtheir diameter 5 feet.
The columns in thedirection of the breadthof the vault were fourin number, and on theside which joined theforum eight, includingthose at the angles inboth cases ; on the op-posite side there weresix, because the twocentral were omitted,that the view of thePronaos of the templeof Augustus might notbe obstructed. Thetribunal was in theform of the segment ofa circle, the width being46 feet, and the depth15 feet.
The two-fold di-rection of the roof, Vi-truvius states, pro-duces an agreeableeffect on the exterior,as well as from thelofty vault within; andfor economy such abuilding would alwaysbe preferred, no ar-rangement affordinggreater accommoda-tion, with the same
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BASILICA AT FANO.