VAN WERT ward devoted himself to architecture, and de- signed several .churches in Urbino, a new port for Ancona, and many religious edifices. In 1725 the pope appointed him architect of St. Peter's, for the protection of the cupola, of which he designed several supports of iron; and he built the vast Augustinian convent at Borne. Subsequently he became architect to Charles III., king of Naples, for whom he con- structed a palace and aqueduct at Caserta, and other fine works. See Vita di Luigi Vanvi- telli, by L. Vanvitelli (Naples, 1823). VAN WERT, a N. W. county of Ohio, border- ing on Indiana, drained by the St. Mary's and tributaries of the Auglaize river ; area, 390 sq. m. ; pop. in 1870, 15,823. The surface is level and mostly covered with a heavy growth of valuable timber. The soil is a rich loam rest- ing on a substratum of blue marl. The Miami canal passes along the E. border of the county, which is intersected by the Pittsburgh, Fort Wayne, and Chicago railroad. The chief pro- ductions in 1870 were 146,719 bushels of wheat, 25,768 of rye, 162,280 of Indian corn, 90,379 of oats, 35,617 of potatoes, 57,781 Ibs. of wool, 270,789 of butter, and 14,799 tons of hay. There were 4,364 horses, 4,340 milch cows, 5,202 other cattle, 19,780 sheep, and 12,945 swine ; 2 flour mills, 1 iron foundery, 3 tanneries, 18 saw mills, 1 machine shop, and 2 woollen mills. Capital, Van Wert. VAN ZANDT, a N. E. county of Texas, bound- ed N. E. by the Sabine river, and drained by affluents of the Sabine, Neches, and Trinity ; area, 875 sq. m. ; pop. in 1870, 6,494, of whom 682 were colored. The surface is undulating and the soil fertile. About one third is prai- rie, and the rest timbered. The chief produc- tions in 1870 were 194,879 bushels of Indian corn, 29,935 of sweet potatoes, 4,088 Ibs. of wool, and 2,926 bales of cotton. There were 2,422 horses, 15,179 cattle, 2,406 sheep, and 17,300 swine. Capital, Canton. VAPEREAU, Louis Gustave, a French author, born in Orleans, April 4, 1819. He studied at the normal school, and in 1842 was secretary to Victor Cousin, whom he assisted in his work Pensees de Pascal. From 1843 to 1852 he was professor of philosophy in the college at Tours, being half of the time also professor of Ger- man. ' In 1852, when restrictions were im- posed upon philosophical instruction in col- leges, he settled in Paris as a private teacher and as a writer. In 1854 he was admitted to the bar, and became the chief editor of the Dic- tionnaire universel des contemporaim, editions of which appeared in 1858, 1861, 1865, and 1870, the last in 1888 double-column pages (supplement, 1873). VAPORIZATION, the conversion of the par- ticles of liquids, and in some instances of solids, into a gaseous condition. "When the action takes place from the surface, it is called evap- oration ; when from the interior of the mass, ebullition. Evaporation takes place at all tem- peratures with most liquids, but there are VAPORIZATION some which cease to give off vapor at reduced temperatures ; thus if two vessels, one contain- ing oil of vitriol and the other a solution of chloride of barium, are placed together under the exhausted receiver of an air pump, no pre- cipitate of barium will be produced in the lat- ter vessel, showing that no sulphuric acid has evaporated. Most solids before passing into vapor become liquid; but several, as iodine and camphor, pass immediately from the solid to the vaporous condition. Ebullition differs remarkably from evaporation, and with a few exceptions always takes place in a given liquid, subjected to the same external pressure, at the same temperature. (See BOILING POINT, and EVAPORATION.) The amount of vaporization which will take place from any liquid will de- pend upon its molecular composition, its tem- perature, and the spa<Je in which it is confined. The laws of vaporization are conveniently studied by observing the formation of vapor in the upper end of a barometer tube. A glass tube from 36 to 40 in. long and half or three quarters of an inch in diameter, closed at one end and filled with mercury, may be inverted in a reservoir of that liquid, when the column will fall until it is balanced by the pressure of the atmosphere, and a vacuum will exist in the upper part of the tube. If now a drop or two of sulphuric ether is passed into its mouth, it will on arriving at the surface of the mercurial column meet with no resistance to the vapori- zation of. its particles, and it will consequently fill the previous vacuum, and produce by its expansion a pressure on the surface of the mercurial column, which will therefore fall to such an extent that its weight, added to that of the force of expansion of the ether vapor, will balance the pressure of the atmosphere. The introduction of one or two drops more will cause a further fall of the mercurial col- umn, until after several repetitions the depres- sion of the column will cease, but simultane- ously there will be a collection of fluid ether at the surface of the mercury and on the sides of the tube, and no drop of ether subsequently introduced will suffer vaporization unless the temperature is increased. If, however, the tube is warmed, the tension of the ether vapor will be increased ; and if the process is con- tinued a point will be reached where all the mercury will be expelled from the tube, and the latter will be filled with the vapor of the ether, the tension of which will then be equal to that of the atmosphere. The temperature at which this takes place is the boiling point of the ether. The ether at any stage of the ex- periment will boil at the temperature it may have attained when the pressure upon its sur- face is equal to that which it sustains under the circumstances, viz., the difference between the column in a barometer and that in the ex- perimental tube. For instance, if the column in the latter is 22 in. while the barometer marks 30 in., then the ether, at the tempera- ture to which its vapor has been raised, will
