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 ICE 147 pressure is used, it is necessary that the ice should be but little below the freezing point. This is the explanation of snow-ball making. As the freezing point of water is lowered by pressure, it is easy to understand how this for- mation of solid blocks from fragments may take place. A certain degree of viscosity, ap- proaching liquefaction, is produced, by which the particles are reunited, and are firmly held as soon as the pressure is removed or lessened. The motions of glaciers, attended as they are by alterations in the form of immense masses of ice, is explained by this property that ice has of liquefying under enormous pressure. Mountains of ice squeezed into crevasses must oxert a force which we probably cannot pro- duce by any artificial means, and as a conse- quence the ice may be made viscous when at a temperature considerably below the freezing point. For other properties of ice, see GLA- CIER, SNOW, and FREEZING, ARTIFICIAL. ICE TRADE. Ice was little known as an article of commerce until the early part of the present century. In the 17th century its use was so common in France that many dealt in it and in snow, gathering these in winter and packing them closely in pits surrounded with straw or other non-conducting substances and protected from the air. The Italian peasants also have long found a profitable business in collecting the snow upon the Apennines and storing it in the caves of these mountains to supply the large demand at Naples. The bodies of ice found in the recesses of Mount Etna, and ex- cavated sometimes from beneath beds of lava which have flowed over them, are noticed in the article ETNA. In the last century the gathering and storing of ice for summer use is known to have been practised in some of the middle states of the American Union, the re- ceptacles for preserving it being deep cellars, placed so as to be readily drained, or from which the water was pumped out as it collect- ed ; but though most wanted in countries where it is not naturally produced, no attempts had been made to transport it by sea. This was first done by Mr. Frederick Tudor of Bos- ton, who sailed with a cargo of 130 tons in his own brig to Martinique in. 1805. He perse- vered in the business, though making little or no profit, till after the close of the war of 1812. In 1815 he obtained the monopoly of the Havana business and important privileges from the Cuban government. In 1817 he introduced the trade into Charleston, S. C., the next year into Savannah, and in 1820 into New Orleans. Frequent disasters attended his enterprises, and in 1832 his entire shipments amounted to only 4,352 tons, the whole of which came from Fresh pond in Cambridge. In May, 1833, he sent the first cargo of ice to the East Indies, which was delivered at Calcutta in the autumn of that year. Of 180 tons, one third was wast- ed on the voyage, and 20 tons more in going up the Ganges. It was packed in large blocks closely fitted together between a double plank casing filled in with dry tan. The ice was sold immediately at half the cost of that prepared by the natives. At the present time a waste of about one half is generally expected on this voyage. In 1834 the first cargo was shipped by Mr. Tudor to Brazil. Until 1836 he conduct- ed the whole trade ; but as it became profitable others began to enter into it, and from other ports besides Boston. That port, however, still has the great bulk of the trade, the shipments having been as follows, according to the incom- plete returns that have been preserved : In 1805 180 tons. ' 1816 1,200 " " 1826 4,000 " " 1836 12,000 " " 1646 65,000 " " 1856 146,000 " In 1866 124,751 tons. " 1668 105,818 " " 1870 78,808 " " 1871 109,298 " " 1872 98,859 " " 1878 81,266 " Of the amount shipped in 1873, 30,333 tons went to coastwise and 50,933 tons to foreign ports. The total exports from the United States to foreign ports for the year ending June 30, 1873, were 53,553 tons, valued at $188,095, of which 48,890 tons, valued at $175,848, were from Boston ; 14,449 tons were shipped to Cuba, 13,342 to the East Indies, 10,186 to the British West Indies and British Honduras, 4,392 to British Guiana, and the rest to other por- tions of the West Indies, South America, &c. Into the interior ice has been carried by rail- road in considerable quantity as far as Knox- ville, Tenn. Some ice was formerly shipped to England, but the British market is now en- tirely supplied from Norway, the Norwegian ice being cheaper than the American, though of inferior quality. The imports into the United Kingdom in 1872 amounted to 139,421 tons, valued at 128,251. The chief difficulty in es- tablishing the ice business in warm countries has been the necessity of constructing houses especially adapted for preserving the ice ; and these to be profitable must be upon a large scale. One of these erected in 1845 at Cal- cutta, by Mr. Wyeth of Cambridge, covered more than three fourths of an acre, and was capable of holding 30,000 tons of ice. Its walls of brick were triple, with flues or air spaces between ; their length was 198 by 178 ft., and their height 40 ft. The building was covered by five roofs, and between every two contigu- ous ones were air spaces. New York city is supplied with ice chiefly from small lakes near the Hudson river, or from the river itself above Newburgh. The whole amount gathered when the season is favorable is about 1,160,000 tons, of which 200,000 tons are from the lakes (Rock- land lake in Orange co. supplying 80,000 tons), and the rest from the river. Deducting one third for wastage, we have 774,000 tons, the amount required to supply the present demand of New York and Brooklyn. The demand in- creases at the rate of about 70,000 tons a year. With the growth of the business upon the coast it has also spread in the interior, where, espe- cially near the large towns, the gathering of ice is now an important business. The great