WARMING-VENTILATION-LIGHTING. TH WARMING. 'HE average temperature of the human body is from 98° to 100°; and whether the individual be exposed to a tropical or to an arctic climate, his blood never rises above or falls below the medium more than one or two degrees, whatever his feelings of heat or cold may be. It seems as if this amount of heat, and no other, were consistent with the existence of warm-blooded animals; for if by any means the temperature of an animal's body is reduced below the above limit, its vital action declines, and soon comes to a stand. In like manner, when heated seven or eight degrees above its usual warmth, the vitality is destroyed. The temperature thus necessary for the life of the body, is maintained by the action of that life itself. Objects surrounding the body being in almost all cases colder than it, are constantly stealing part of its warmth; but within the system there is an incessant process of combustion going on, producing fresh heat, exactly as the fire in a grate does. When the heat thus generated is not dissipated fast enough, so that the body tends to become warmer than the due degree, the accumulation finds vent in perspiration, the evaporation of which carries off the excess (see NATURAL PHILOSOPHY). In general, however, the tendency is the other way; the heat of the body, if allowed freely to escape, would be dissipated faster than it is produced; and hence arises the necessity of clothing, houses, and other means of retarding its escape. The lower animals are in general provided by nature with coverings for this purpose, according to the requirements of the climate in which they live. Man is left to the exercise of his inventive faculties to provide clothing and shelter for himself. In the lower animals, too, the heatproducing function is more active than in man. At least, this is true of civilised man ; for there can be no doubt that the naked and painted savages that inhabited these islands 2000 years ago had a power of resisting cold unknown to us their descendants. Even in civilised communities, those that lead a life of activity in the open air require far less protection from the cold than those that live indoors. There is, besides, the greatest difference in this respect between individuals, though placed in exactly similar circumstancesa difference intimately connected with the soundness of the digestion and other nutritive pro cesses. The feelings of buoyancy which most persons in tolerable health experience during a clear frosty day, have led to a general belief in the peculiar healthiness of cold weather. But the statistics of death and disease tell a different tale. The Reports of the registrar-general shew that, exactly as the thermometer sinks, the rate of mortality rises, and certain diseases of the most fatal kind become more prevalent; the vitality, in short, of the community decreases as the warmth of the atmosphere decreases. We believe it to be an established fact, that the means generally taken to arrest the waste of heat from our bodies, or to supplement it, are, for the majority of men and women, insufficient, or injudiciously managed. This is a matter of literally 'vital' moment to one and all. The economy of heat is a primary element in the art of living in health and comfort; and no knowledge of common things' that we can think of, can surpass in importance a right understanding of the principles and facts on which that art rests. We have as yet spoken of arresting the dissipation of the natural heat by clothing and shelter; and this, among some nations, is made to suffice. Where fuel is scarce, the resource against the cold of winter is thick clothing indoors as well as out. This is said to be the regular practice in China; and even in the south of Europe, fires are dispensed with in weather when we should think them absolutely necessary, and additional wrappings are considered as appropriate while sitting in the house, as in the open air. But wherever fuel can be had, it is always preferred to wear within doors much the same clothing in winter as in summer, and to keep the apartments nearly at summer temperature by artificial heat. It is this special branch of the subject, namely, the artificial warming of apartments, that we are at present to consider; that of Clothing will be treated in a subsequent number (see also PRESERVATION OF HEALTH). In order to regulate temperature, we must first know the nature of heat-how it is produced, and what laws it follows. This forms a branch of the science of Physics, and has been briefly treated in NATURAL PHILOSOPHY. But for the better understanding of the present subject, it may be well to say something more here of Combustion, Which is the chief source of artificial heat. Combustion consists in the rapid union of the oxygen of the air with some substance for which it has a strong chemical attraction, and which is called a combustible or fuel. All chemical combination produces heat; but it is only called combustion when the heat is so intense as to produce light. The cheapest combustibles or fuels are coal, wood, peat, coke, and charcoal, which consist chiefly of two simple bodies or elements, carbon and hydrogen (see CHEMISTRY). Before oxygen will unite with the combustible, the latter must be heated to a high pitch; the combustion once begun in one part of the fuel, is then sufficient to keep the rest at the combining temperature, provided the heat is not too rapidly dissipated. One piece of fuel will seldom keep alight alone; a number of pieces require to be burned together, in order to keep one another warm. To blow cold air rashly into a weak fire, puts it out, by suddenly cooling the coal below the combining point. Á cold poker held near the flame of a candle will extinguish it; 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 of 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 of 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 mentioned, 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 incombustible 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. 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 temperature 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 consisted, 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 The really valuable product of combustion is their apartments chiefly by portable stoves or the heat evolved. There are various ways of chafing-dishes, without any regular exit for the measuring its amount-as by the quantity of ice smoke and fumes; and a brasier of charcoal is it melts, or the number of degrees to which it still the chief means of lighting sitting-rooms in heats a certain quantity of water. Thus, it is Spain and Italy, which are in general without found that the burning of one pound of good chimneys. As late as the fourteenth century, the coal melts 90 pounds of ice; of coke, 84 pounds; hearth in Britain continued to be in the middle of of wood, 32 pounds; of charcoal of wood, 95 the apartment, and the smoke escaped by an pounds; of peat, 19 pounds. In speaking of the opening in the roof, called the louvre (Fr. l'ouvert). heating effects of combustion, it is specially neces-At last, the fire was placed at the side, in a sort sary to bear in mind the different capacities of of apartment formed by two projections, within bodies for heat, or their specific heat. Water, for which were placed seats where the warmth might instance, has great capacity for heat, or is very be enjoyed. This recess came gradually to be difficult to warm. The same amount of heat built in the thickness of the wall, and was thus that raises the temperature of a pound of water transformed into the modern chimney. 1°, 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 carbon, and partly of bitumen or pitch. The bitumen 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 transparent like air, and does not deposit carbon when cold. It is this highly heated gas, combining with the oxygen of the atmosphere, that constitutes flame. The pitchy vapour rising from burning 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 th flame has always more or less hydrogen in coke and charcoal, from which the gaseous has been driven off, burn without flame. 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 disadvantages. The greatest of these is the uneconomical use which it makes of fuel. About one-half of the heat 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 fourth of the heat which is radiated into the apartment is, in ordinary circumstances, carried back by currents into the chimney between the fire and the mantel-piece, and thus lost. It is calculated by Dr Arnott, that only about oneeighth part of the heat-producing power of the fuel used in common fires is realised, all the rest being dissipated into the surrounding atmosphere. Notwithstanding this and other acknowledged evils, the open fire continues to hold its place, partly perhaps from prejudice, partly from real points of superiority over other methods as yet practised; and the object of late has been, not so | existing grate by placing over the bars a piece of Grates. One improvement consists in diminishing the quantity of metal in immediate contact with the fuel, and forming the back and sides of the grate of fire-bricks. For the reason given above, this renders the combustion more complete and the yield of heat greater. Another point deserving attention is the shape given to the chimney-mouth, or recess above the grate. When the sides are square with the back, none of the heat falling on them is given out again into the room. With a view, therefore, to throw out the heat better, the sides, or covings, as they are called, are inclined to the back at an angle of about 130°; and sometimes they are made curved and of polished metal, in order that they may reflect the heat without absorbing it. It is questionable, however, if simple brick slabs, placed at the proper angle, do not throw out more heat than the most splendid polished metal plates. Much also depends upon the shape of the firebox, or grate, itself. To see the importance of this, it is necessary to attend carefully to the exact way in which an open fire heats a room. It does so almost entirely by the rays of heat that it throws out; and these rays do not warm the air directly; they pass through it like light through glass, just as the hottest rays of the sun pass through the upper atmosphere, leaving it cold enough to freeze mercury. It is only when the rays of the fire fall on the floor, furniture, and walls of the room, that they give out their heat; and it is by coming in contact with these solid heated bodies that the air is gradually warmed. We may thus see the necessity of having a fire lighted and burning brightly for a considerable time before the hour when the apartment is expected to be comfortable. The law that radiant heat neither affects nor is affected by the surrounding air, also explains the fact that an apartment may feel very cold though the air in it be at high summer heat. A church or other massive stone building in frosty weather may be filled with heated air, and yet retain its chilling effect for many hours. The warmth of the living body is lost in two ways: the film of colder air that touches it receives part of its heat by conduction, and rising up makes room for another film to do the same; a moderately heated body, in cooling, is robbed of about half its heat in this way. The other half is given off in rays, which pass through the air and impinge upon the objects around. These objects are radiating back heat in return; but their temperature being low, the return is small, and the warmer body is colder by the difference. Hence we are chilled by a cold wall or a cold window without touching it, and though the air between us and it may be at 70°.-To return to the shape of the grate. The chief object is to present as large a surface as possible of glowing fire to the front. view, the grate is made long and deep, in proporWith this tion to its width from front to back. This principle, however, is carried too far in many grates; the stratum of fuel is too thin to burn perfectly. The bottoms of grates should be solid, instead of consisting of bars; this, which is the usual construction, causes an excessive draught and a waste of fuel. The error may be corrected in an ing grates almost on a level with the floor is a in a constant wide current of the warm air of the the various forms of grate constructed, with more It would be endless to attempt to enumerate or less success, on the above principles. We shall content ourselves with a notice of the smokeless grate invented by Dr Arnott, to whom the subject any individual since the days of Count Rumford. of warming apartments is more indebted than to It comes nearer to the idea of perfection in an open fireplace than any previous contrivance. Its peculiar advantages will be understood from the following description and diagram : front bars of a grate in a chimney of the usual Arnott's Smokeless Grate.—ab, ef, represent the construction, rswu. The grate has no bottom, น Fig. 1. d W and below it is an iron box, open only at top, into to thirty pounds-is_put. Any kind of coke or which the charge of coal for the day-from twenty quantity of wood is laid on the surface of the fresh coal may be used. To light the fire, the usual. coal at ef, and a thickness of three or four inches of cinders or coked coal, left from the fire of the preceding day, is laid over all. The wood being then lighted, very rapidly ignites the cinder above, and at the same time the pitchy vapour from the fresh coal below rises through the wood-flame and cinders, and becomes heated sufficiently itself 483 to become flame, and so to augment the blaze. When the cinder is once fairly ignited, all the bitumen rising through it afterwards burns, and the fire remains smokeless.' As there is no supply of air but through the bars in front, the box being close underneath, the fire must be gradually raised up as the combustion goes on; and this is effected by having a false bottom, ss, in the box, which can be moved like a piston by means of a rod. The rod has notches in it, and, by means of the poker used as a lever, can be raised up and then retained at any height by a ratchet-catch. 'A remarkable and very valuable quality of this fire is, its tenacity of life, so to speak, or its little tendency to be extinguished.' Even after it sinks below the level of the box, it does not go out, but continues to smoulder slowly for a whole day or night, and is ready to burn up actively when the piston is raised. Another peculiarity of the Arnott grate is the means taken to diminish the proportion of the heat usually carried up the chimney. Of the thick column of smoke that issues from a common chimney-can, only a small fraction is true smoke or burned air; the rest consists of the warmest air of the room, which becomes mixed with the true smoke in the large space usually left between the top of the fire and the throat of the chimney. To remedy this evil is the object of the hood of metal, yab, in the diagram, which prevents the entrance of pure air to mix with the smoke. The saving of fuel in this way is said to be from onethird to one-half. The hood is furnished with a throttle-valve or damper, t, having an external index, shewing its position, so as to give complete control over the current. The provision made for ventilation in this fireplace will be considered in another part of the paper. WARMING BY STOVES. A close stove is simply an inclosure of metal, brick, or earthenware, which is heated by burning a fire within it, and then gives out its heat to the air by contact, and to surrounding objects by radiation. The simplest, and, so far as mere temperature is concerned, the most effective and economical of all warming arrangements, is what is called the Dutch stove; which is simply a hollow cylinder or other form of iron standing on the floor, close at top, and having bars near the bottom on which the fire rests. The door by which the coals are put in being kept shut, the air for combustion enters below the grate; and a pipe, issuing from near the top, carries the smoke into a flue in the wall. If this pipe is made long enough, by giving it, if necessary, one or more bends, the heated gases from the fire may be made to give out nearly all their heat into the metal before they enter the wall; and thus the whole heat of the combustion remains in the room. The great objection to this form of stove is, that the metal is apt to become overheated, which not only gives rise to accidents, but has a hurtful effect upon the air. It cannot be said to burn it, in the proper sense of the word, for none of its oxygen is abstracted; but it gives it a peculiar odour, which is both unpleasant and unwholesome. This is thought to arise in some measure at least from the hot iron burning the particles of dust that light on it, which particles consist of organic matter, such as wool, wood, &c. Part at least of the unwholesomeness of air so heated arises from its excessive dryness; it parches and withers everything it touches, like the African simoom. It must not, however, be supposed that this is peculiar to air heated by contact with metal; air suddenly heated is always unwholesomely dry. This is an important point in regard to the subject of warming, and requires consideration. The relation of vapour to the air is fully explained in METEOROLOGY, which the reader is recommended to consult in connection with this subject. It may be stated shortly here, that a cubic foot of air, say at 32°, can contain a certain quantity of moisture and no more; but if heated to 80°, it is capable of containing five times as much, and has thus become thirsty, and drinks up moisture from everything that contains any. Whenever the temperature within doors is much higher than without, the air is in a too thirsty state, and parches the skin and lungs, unless means be taken to supply the necessary moisture. An evaporating pan or other contrivance is an essential part of warming apparatus; it is specially necessary to attend to this during east winds, which are generally too dry even at their natural temperature. Even in this, perhaps the most economical form of open fire yet contrived, there is still great waste of the heat actually produced by the combustion. To say nothing of what passes by conduction from the fire itself into the wall, and is mostly lost; the quantity carried off in combination with the hot gases, though no more air is allowed to enter than is necessary for complete combustion, is still great. It deserves being noticed, that the proportion thus carried off is greatest in the case of fuel that burns with flame. Experiment shews that a fire of wood radiates one-quarter of its heat, the rest flying up; while the radiation from wood-charcoal is one-half of the whole heat produced. Every one has felt that a blazing fire has far less warming effect than a glowing one. Not that flame has not intense heat in it-more intense even than a glowing fire; but it gives it out only by contact, and not by radiation. It thus appears that any mode of heating that depends upon direct radiation, as the open fireplace chiefly does, necessarily involves great waste of fuel. This can be avoided only by applying the heat on a different principle, which All improvements on this simple and rude form consists in first making the fire heat certain appa- of stove aim at avoiding a high heat in the ratus with considerable surface, which then, by warming surface, and this chiefly by lining the radiation and contact with the air of the apart-fire-box with brick, and inclosing it in several ment, diffuses its heat throughout it. This is the principle of the other methods of warming, which we now proceed to describe. The consideration of methods that combine the two principles, will come most conveniently last. casings, so as to enlarge the heated surface. A general notion of these contrivances may be got from the annexed cut (fig. 2), representing the kind of stove called a cockle. The fire is burned in a small furnace within the inner case, and the air is warmed by circulating between the inner and outer cases. When placed in the apartment or hall to be warmed, the outer casing has perforations about the top for the issue of the warm air. For heating churches and similar buildings, the stove is placed in a separate furnace-room, and the warm air is conveyed to the different parts of the building in pipes or flues, while fresh air is drawn to the stove through a channel or culvert leading from outside the building to the openings in the outer casing, where the arrows are seen entering. Fig. 2. The stove invented by Dr Arnott is upon the same principle of an extensive and moderately warm heating surface. For the description, we must refer to the inventor's own treatise on Warming and Ventilation. For many years, Dr Arnott has had his own dining-room warmed by such a stove. The fire in winter is never extinguished, and a uniform temperature of from 60° to 63° is maintained by consuming at the rate of about a ton of anthracite in six months. In Germany and other northern countries of Europe, the stoves are usually built of brick, covered with porcelain. They are of the size of a large and very high chest of drawers, and usually stand in a corner of the room. The fire is burned in a furnace near the bottom, and the heated smoke is made repeatedly to traverse the structure from side to side, along a winding passage, before it reaches the top, where a pipe conveys it, now comparatively cold, into a flue in the wall. The heated mass of brick continues to warm the room long after the fuel is burned. It is generally sufficient to warm the stove once a day. The same quantity of wood burned in an open grate would be consumed in an hour, and would hardly be felt. excessive temperature of the metal, are known as gill stoves, from the plates having a resemblance to the gills of a fish. They have recently come into considerable use. The idea of having an air-chamber behind and around the fireplace, from which warm air would issue into the room, thus saving part at least of the vast amount of heat that is lost by passing through the wall, is not new, having been put in practice by the Cardinal Polignac in the beginning of last century. But the way to carry the principle out to the full would be to have the open fireplace in a pier of masonry standing isolated from the wall, like a German porcelain stove. A very small fire would keep the whole mass mildly heated. The pier could receive any shape, so as to give it architectural effect; and it might either terminate in the room-the smoke, after parting with most of its heat, being conducted by a pipe into the wall-or it might be continued into the story above, where its heat would still be sufficient to warm a bedroom. An Arnott smokeless grate, set in the pedestal of an ornamental column, which might either stand in front of the wall or in a niche in its depth, might be made the beau-idéal of comfort, economy, and elegance. WARMING BY GAS. When care is taken to carry off the products of combustion by a pipe, and to prevent overheating, gas-stoves will be found economical and pleasant, and capable of being used in situations where a common stove is inadmissible. In stoves, gas should always be burnt with the Bunsen burner, which is generally employed by chemists when they make use of gas for heating purposes. It consists of a small brass cylinder, or chimney, set over the gas-jet, like the glass of an argand lamp, with openings near the bottom to allow air to enter. The gas being admitted into this before lighting, mixes with the air, and when lighted at the top, burns with a pale-blue flame. The most complete combustion and the properly so called, there is none. Still it must not be forgot that there is burnt air-a cubic foot of carbonic acid, besides a quantity of watery vapour, for every cubic foot of gas used; and therefore, even with the Bunsen burner, these gaseous products should, wherever it is possible, be conducted away. STEAM AND HOT WATER. Open-fire Stoves.-As a specimen of the numer-greatest heat are obtained in this way. Smoke, ous plans for combining the advantages of the stove and the open fire, we may take Sylvester's stove or grate, which is thus described in Ronalds and Richardson's Technology: 'The fuel is placed upon a grate, the bars of which are even with the floor of the room. The sides and top of these stoves are constructed of double casings of iron, and in the sides a series of vertical plates, parallel with the front facing, are included in the interior, which collect, by conduction, a great portion of the heat generated from the fire-the mass of metal of which these are composed being so proportioned to the fuel consumed, that the whole can never rise above the temperature of 212° Fahrenheit under any circumstances. The sides and top of the stove are thus converted into a hot chamber, offering an extensive surface of heated metal; at the bottom, by an opening in the ornamental part, the air is allowed to enter, and rises as it becomes warmed, traversing in an ascent the different compartments formed by the hot parallel plates, and is allowed to escape at the top by some similar opening into the room.' Stoves furnished with a series of parallel plates to increase the heating surface and prevent an The immediate warming agent in these two methods is the same as in Arnott's and other lowtemperature stoves-namely, an extensive metallic surface moderately heated; but instead of heating these surfaces by direct contact with the fire, the heat is first communicated to water or steam, and thence to the metal of a system of pipes. This affords great facility in distributing the heat at will over all parts of a building; and these methods are peculiarly adapted to factories, workshops, and other large establishments. advantages are-freedom from dust, and from all risk of overheating and ignition. Other Steam.-Steam-warming is generally adopted in establishments where steam-power is used, as the same boiler and furnace serve both purposes. |