CHAMBERS'S INFORMATION FOR THE PEOPLE. 



and a fire, on the other hand, burns much better 

 when surrounded by bricks, than by metal. The 

 bricks act like clothing, and keep in the heat o 

 the coals ; the iron being a good conductor, runs 

 away with the heat as fast as it is generated 

 and passes it into the wall, making the coals that 

 touch it dull and black. 



Products of Combustion. The carbon of the 

 fuel unites with 2$ times its weight of oxygen, 

 forming carbonic acid gas, and the hydrogen with 

 8 times its weight, forming water in the state oi 

 vapour or steam. For the complete combustion 

 of a pound of coals of average quality, about 230 

 cubic feet of air are required ; of which some 46 

 feet are oxygen, and the rest nitrogen, which takes 

 no part in the combustion. This nitrogen mingles 

 with the carbonic acid and vapour before men- 

 tioned, and the whole ascend from the fire in the 

 form of a heated gaseous current, which, when the 

 combustion is complete, is colourless as common 

 air. Were the fuel composed of carbon and 

 hydrogen alone, these would be the only products 

 of perfect combustion ; ashes arise from earthy in- 

 combustible substances in the fuel, which lessen 

 its value. If the fuel contain water, the water is 

 driven off in steam, and carries away a great deal 

 of the heat of the fire in a latent form. From this 

 cause, green wood gives little heat ; and coals 

 when wetted give less than the same quantity 

 burnt dry. 



The really valuable product of combustion is 

 the heat evolved. There are various ways of 

 measuring its amount as by the quantity of ice 

 it melts, or the number of degrees to which it 

 heats a certain quantity of water. Thus, it is 

 found that the burning of one pound of good 

 coal melts 90 pounds of ice ; of coke, 84 pounds ; 

 of wood, 32 pounds ; of charcoal of wood, 95 

 pounds ; of peat, 19 pounds. In speaking of the 

 heating effects of combustion, it is specially neces- 

 sary to bear in mind the different capacities of 

 bodies for heat, or their specific heat. Water, for 

 instance, has great capacity for heat, or is very 

 difficult to warm. The same amount of heat 

 that raises the temperature of a pound of water 

 l, will heat 30 pounds of mercury to the same 

 extent. 



The combustion of fuel is seldom perfect, except 

 in the case of coke, wood-charcoal, and anthracite 

 coal, which are composed of carbon without 

 hydrogen. Common coal consists partly of car- 

 bon, and partly of bitumen or pitch. The bitu- 

 men also contains carbon, but in combination 

 with the volatile gas, hydrogen ; and when heated 

 to a certain degree, it rises or distils off in vapour. 

 If the heat is only about 600, this vapour is thick 

 and black, constituting smoke, and as it cools, it 

 deposits soot, which is carbon in fine powder. A 

 greater heat makes the carbon and hydrogen take 

 another arrangement, and become carburetted 

 hydrogen gas common coal-gas which is trans- 

 parent like air, and does not deposit carbon when 

 cold. It is this highly heated gas, combining 

 with the oxygen of the atmosphere, that consti- 

 tutes flame. The pitchy vapour rising from burn- 

 ing fuel is not hot enough to combine with 

 oxygen, unless it come in contact with flame or 

 hot coals. It thus appears that fuel which burns 

 with flame hds always more or less hydrogen in 

 it ; coke and charcoal, from which the gaseous 

 part has been driven off. burn, without flame. 

 Mi 



We now proceed to consider the application of 

 the heat thus generated to the warming of 

 dwellings, keeping in view rather the illustration 

 of the general principles that should guide every 

 such application, than entering into constructive 

 details of apparatus. 



The great aim, it may be premised, in all plans 

 of warming is, as it is expressed by Dr Arnott, 

 ' to obtain everywhere on earth, at will, the temper- 

 ature most congenial to the human constitution, 

 and air as pure as blows on a hill-top? The 

 obtaining of the desired temperature would be 

 comparatively easy by itself ; the difficulty lies in 

 combining warmth with pure air. The various 

 plans hitherto tried may be classed under the four 

 heads of The Open Fire, Stoves, Gas, Steam and 

 Hot Water. 



THE OPEN FIRE. 



The first application of artificial warmth con- 

 sisted, most likely, in lighting a fire of dried sticks 

 and leaves in a grove, a cave, or other natural 

 shelter. When tents or wigwams came to be 

 erected, the fire would be lighted on the middle of 

 the floor, with perhaps a hole in the roof for the 

 smoke to escape by. This primitive arrangement 

 still exists in Central Asia and Siberia, and may 

 even be seen in some of the cabins of Ireland and 

 the Scottish Highlands. The Romans warmed 

 their apartments chiefly by portable stoves or 

 chafing-dishes, without any regular exit for the 

 smoke and fumes ; and a brasier of charcoal is 

 still the chief means of lighting sitting-rooms in 

 Spain and Italy, which are in general without 

 chimneys. As late as the fourteenth century, the 

 hearth in Britain continued to be in the middle of 

 the apartment, and the smoke escaped by an 

 opening in the roof, called the louvre (Fr. I'ouvert). 

 At last, the fire was placed at the side, in a sort 

 of apartment formed by two projections, within 

 which were placed seats where the warmth might 

 be enjoyed. This recess came gradually to be 

 built in the thickness of the wall, and was thus 

 transformed into the modern chimney. 



It is scarcely necessary to remark, that the mode 

 of heating apartments now most prevalent in 

 Britain is by a fire of coal placed in a grate, 

 having a chimney above, through which the 

 vaporised products of the fuel are carried off. 

 There can be no doubt that this glowing open 

 fire has an air of cheerfulness and comfort, which 

 makes it almost an object of worship ; yet it is not 

 unattended with certain drawbacks and disadvan- 

 tages. The greatest of these is the uneconomical 

 use which it makes of fuel. About one-half of the 

 icat produced by a common fire ascends with the 

 smoke ; the black part of the smoke itself being 

 an unconsumed part of the fuel. Finally, about a 

 "ourth of the heat which is radiated into the 

 apartment is, in ordinary circumstances, carried 

 sack by currents into the chimney between the 

 fire and the mantel-piece, and thus lost. It is 

 calculated by Dr Arnott, that only about one- 

 eighth part of the heat-producing power of the 

 "uel used in common fires is realised, all the rest 

 jeing dissipated into the surrounding atmosphere. 

 Notwithstanding this and other acknowledged 

 evils, the open fire continues to hold its place, 

 Dartly perhaps from prejudice, partly from real 

 points of superiority over other methods as yi 



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