Chap. IV.

HOMAN.

211

are built against the outer walls, which renders the ventilation imperfect, windows not beingpermitted on the outside.

The docks for the shipping are convenient, and there are plentiful supplies of fresh water ;but the want of a free circulation of air, and the too great proximity of the differentbuildings, arc serious objections.

Great attention and skill is demanded in the selection of a site, as well as in the arrange-ment of hospitals of this kind.

Ill Italy, engineering works continued to be carried on with great success: in Rome lasanta , Napoli la gentile , Genoa la superba , Milano la grande , Ferenze la bella , Bologna la grassa , Ravenna f antica , Padua la dotta , and Venezia la ricca , all can boast of objectsworthy the attention of an engineer. The latter city deserves admiration for the variousdifficulties overcome in laying the foundations for the noble buildings it contains. Theprovince of the Roman Venetia was bounded by the Adda, the Ilhrctian and Julian Alps ,and the Po. About 450 years before Christ, the inhabitants of Aquileia and Padua, drivenout by the Huns under Attila , took refuge in the islands along the coast, and laid the firstfoundations of the future Venice , on the island of Ripa Alta or Rialto. In a. n. 570, thepatriarch of Aquileia fled before the Lombards with his flock, and settled himself at Grado ,afterwards called New Aquileia ; his successors became the first ecclesiastical primates, andabout the middle of the fifteenth century they removed to Venice .

The modern city is built upon two islands, separated from each other by the great ser-pentine canal, which is crossed by one bridge, called the Rialto ; its total area has been es-timated at one square mile and a half. The two islands arc subdivided by many smallercanals at right angles with the larger, and as the streets or alleys arc seldom more than 8 or9 feet wide, the communication from house to house is chiefly carried on by means of boats,almost every doorway having a landing stair at the water side.

The houses are of brick, or of Istrian marble, which bears a fine polish ; the floors arccomposed of fine plaster and pounded brick, into which, when in a soft state, black and whitemarbles are imbedded, and when dry, are polished; the foundations of the buildings areeither upon piles or masses of concrete.

Hie entrance of the Laguna is guarded by the fort of Lido, distant about two or threemiles from Venice ; the Laguna is separated from the sea by a line of narrow sandy islands,which have required the most vigilant attention, in order to prevent the embankments orbarriers from being forced into the channel. There arc two other passages through thesenarrow sandy deposits, one at the port of Malamoceo, and the other at Chiozza, where mas-sive stone walls have been constructed to defend it against the action of the sea.

Within these sand-banks, produced by the deposits brought into the Adriatic by theseveral mouths of the Po, the Laguna forms an extensive bay, a great portion of which isdry at low water ; the tide rises about 3 or 4 feet, and occasions a current sufficient to workthe mills on the island of San Georgio Maggiore. To keep the various canals open, adredging machine was used at a very early period, which underwent many changes andimprovements before its introduction became general.

Cassiodorus , appointed prefect of Venice by the Emperor Theodoric, has left us aninteresting account of the lagunes at the commencement of the sixth century, when thechief exports were fish and salt.

From the summit of the lofty Campanile in the Piazza San Marco , a fine view of the cityrising amidst the Laguna is obtained. To the north lies the Julian Alps , reaching fromthe Lake of Garda to Trieste , often covered with snow ; to the west is Monte Selice, formedof porphyry and trap, probably of volcanic origin.

The arsenal was a noble establishment, and contained slips for ship-building, andarrangements for the manufacture of all that was required for their equipment and efficiencyin time of war. Here the camel was first used for floating large vessels out of the Laguna,which consisted of four cases, with concave sides, so made as to embrace the whole ship;they were towed under it, and united securely together ; the water was then pumped out ofthe camel, and it became sufficiently buoyant to float its burthen in very' shallow water;such a method was adopted by the ancients to move obelisks and heavy masses, where therewas not depth enough for their large craft to navigate.

In constructing the foundations at Venice , every precaution was taken to collect thewaters which rise from the springs at the bottom of the lagunes; they are conducted intoa basin or well left to receive them, in the bed of concrete upon which the walls werebuilt; where a spring did not occur, the well was converted into a tank to receive thatwhich fell from the roofs of the buildings during the rainy season. These supplies,however, frequently failed, and it was then conveyed in boats from the shores of the mainland, and disposed of to the inhabitants. Trade and commerce have departed from Venice ,and its population is in consequence greatly diminished; but the city remains, to interestthe historian, the architect, and the civil engineer. The finest designs of Palladio, and themanner in which he laid his foundations, may be seen in various parts of the city, and formthe best commentary upon that portion of his treatise on building. All the chief men of

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