Knight's cyclopædia of the industry of all nations, 1851 / [edited by George Dodd].

Date:
[1851]
Catalogue details

Licence: Public Domain Mark

Credit: Knight's cyclopædia of the industry of all nations, 1851 / [edited by George Dodd]. Source: Wellcome Collection.

    965/1000
    1757 WAEMING; VENTILATION. amount of fresh au-, reanisito under any conOition for animal respii-ation, must be more and more increased in proportion to the fuel bm-ned in the room; or, more correctly, there must be one portion of ak to feed combustion, and another portion to aid respiration. Tredgold, Arnott, Reid, and others, have cal- culated the quantity of air required for these purposes. Tredgold states that when a room containing several persons is heated to the average and customaiy degi-ee, it wiU be necessary to supply four times as many cubic feet of fresh air per minute, as there are persons in the room; that is, four feet for each person. But there must be an outlet for the vitiated air equal to the inlet for pure air; and as it is found that respired air ascends to the upper part of the room, it follows that the ceihng or some neighbouring part is the proper place for an outlet. In ordinary English houses no steps what- ever are taken to regulate either the supply of pure air or the exit of vitiated ah; but it is probable that om- large fire-places regulate this matter tolerably well. In crowded rooms however, where the amount of vitiated breath bears a much larger ratio to the cubical con- tents, and where the doors are generally small compared with the height of the room, the impure air cannot escape by these means, and some arrangements must be made near the ceiling for the removal of the air. These methods are chiefly of two different kinds; the one by the use of a revolving wheel or fan-ventilator, and the other by the action of a cMmney or tube. At the Eeform Club- House, London, a steam-engine works a revoMng fan, capable of throwing eleven thousand cubic feet of ah per mmute into a subteiTanean tunnel under the basement story j and the steam from the small steam-engme which works the fan supplies three cast-iron chests with the requisite heat for warmhigtbe whole building. The second mode of effecting ventilation, viz. by the use of a tube or chhnney openmg into the air from the upper part of an apart- ment, depends for its action on the ascensive power possessed by a lofty aerial column. As the heated air of a furnace-chimney carries up the smoke, &c., more rapidly if the chunney be very lofty, so does a lofty chimney exceed a low one in carry ing off vitiated air ; and for the same reason, even if no chimney, properly 30 called, be provided, a lofty room, furnished with appropriate openings in its ceihng, wiU furnish a draught to carry off impure air more rapidly than a low room; and in many of our public buildings this arrangement is deemed sufficient. WATER. ]758 Dr. Amott has made use of the ascending force of the column of heated air in an ordi- nary chimney as a means of ventilating ordinaiy sitting rooms, by placing a balanced valve in an opening from the room into the chimney. He has also introduced very re- cently a mode of ventilating large buildings by applying the pressure of a column of water to work a forcing air-pvimp. These admh-able contrivances, so worthy of the accomphshed physician to whom they are due, ai-e noticed under Aenott's Ventilator. Many forms of ship-ventilation depend on the use of an air-pump. WARWICKSHIRE. The mmerals of this county consist cliiefly of one small coal field, and some quarries of gritstone. There are no less than 170 miles of canal in this county; and it is also well suppUed with rail- ways. Warwickshire stands on the verge of a manufacturing district and contains within itseH many busy towns. The two most notable of these, in an industrial point of view, are noticed elsewhere. [Bibmingham ; COVENTBY.] WATCH. [Clock and Watch Making.] WATER, in its liquid, aeriform, or sohd state, is universally diffused through na- ture. It was once considered as one of the four elements, and is in common language stiU frequently so termed. Water however is now known to be a compound substance con- sistuig of hydrogen and oxygen. It is colour- less, transparent, inodorous, and insipid; it is an imperfect conductor of heat and electri- city ; it is very slightly compressible, jdelding only n,bout 46-65 milhonths of its bulk to the pressure of the atmosphere. Its specific gravity is 1, being the unit to which the den- sity of all hquids and sohds is refen-ed, as a convenient standard, on account of the faci- hty with which it is obtained in a pm-e state. Like all other fluids and substances it expands by exposure to an increase of temperature ; and with a curious exception, the dilatation within certain limits is proportionate to the degree of heat to which it is subjected. When water is heated to a certain point, which is arbitrarily fixed on the scale of Fahrenheit's thermometer at 212°, it acquires the greatest volume it is capable of assuming; it then boUs, and is converted into vapour. Steam at 212° occupies about 1700 times as much space as the water does from which it is generated. It is upon the elastic force of steam commu- nicated by heat, and the instantaneous annihi- lation of it by cold, that the working of the steam-engine depends. Water is seldom found in a state of perfect