V E N V E N 157 number of 18th-century pictures by the Canalctli and by Guard! represent canal views. The fine woodcut bird s-eye view of the city in 1497, engraved by Jacobo de Barbari, is about to be published in facsimile with descriptive text by Giaeomo Boni. PART III. MODERN CITY. The modern city stands on 117 islands, separated by 150 canals (rio) and united by 380 bridges ; all the main traffic passes along the canals. The usual range of tide-level is about 20 inches ; but under exceptional circumstances there is a difference of nearly 6 feet between lowest and highest water. The name " gondola " given to the passenger boats does not occur earlier than the 14th century. As shown in Carpaccio s and Gentile Bellini s pictures (c. 1500), the gondola of that date was quite unlike the present boat with its heavy black cabin and absence of any colouring : the older form had an awning of rich stuffs or gold einbroideries, supported on a light arched framework open at both ends. 1 The peculiar method of rowing with one oar at the stern is the same now as it was in the 15th century, and probably much earlier. Since 1880 "omnibus" steamers have been introduced on the Grand Canal, which has also LA CIUDECCA Map of the islands of Venice. been disfigured in the 19th century by the addition of two hideous iron bridges, over one of which passes the railway that connects Venice with the mainland. Before the Venetian republic was sup pressed by Napoleon I. the population amounted to nearly 200,000 ; in 1830 it had sunk to about 100,000 ; but since then it has in creased, and in 1881 amounted to 132,826 (commune 145,637). The city has grown rapidly in prosperity since its restoration to the kingdom of Italy, and it is now second only to Trieste among the seaports of the Adriatic. The climate is mild but some what rainy, owing to the water-surrounded site. The principal manufactures of the city remain what they were in the Middle Ages, namely, gold and silver work, glass, and velvet and silk, to which must now be added cotton, in all of which, as well as in grain, oils, wine and spirits, fruits, drugs, fish, and hides and leather an active trade is carried on. In 1886 the total value of the exports from Venice to foreign countries amounted to 7,239,470 and that of the imports to 8,788,012. During the same year there entered 2595 vessels of 714,642 tons (Italian 1565 vessels of 222,217 tons) and cleared 2597 of 724,740 tons (Italian 1565 vessels of 227,021 tons). (J. H. M.) VENLO, a frontier town of Holland, in the province of Limburg, on the right bank of the Meuse (here crossed by a bridge), is an important railway junction ; Cologne lies GO miles to the south-east and Maastricht 43 miles to the south-west. The population, which is somewhat closely packed, was 8494 in 1876 and 10,550 in 1887. None of the public buildings has any special interest attaching to it. The leading industries are distilling, brewing, tanning, spinning, needle-making, and tobacco manufacture. There is considerable trade by river with Rotterdam. Venlo was at one time a place of strength, but the fortifications were dismantled in 18G8. VENTILATION is the process of changing the air of rooms and other closed places so that a certain standard of purity may be preserved notwithstanding the vitiation which the air undergoes from the breath of inhabitants, the products of combustion of illuminating agents, and other causes. In estimating the amount of air to be supplied, account must be taken of the standard of purity which is aimed at and of the rate at which vitiation occurs. Of the various impurities that are found in the air of Carbonic inhabited rooms carbonic acid forms the most ready index n( i l in of the ventilation. The open air of London and other air< large inland towns contains about four parts by volume of this gas in 10,000 of air. In the country and in towns near the sea two or three and a half parts in 10,000 is a more usual proportion. Authorities on ventilation usually take four parts in 10,000 as the standard for pure air, and use the excess over that quantity in estimating the adequacy of the air supply. But they differ as to the proportion 1 The use of black was made compulsory by a sumptuary edict oi
the great council in the 16th century.