VENTILATION. 



temperature also becomes at times so high as to 

 cause a disagreeable odour. Another objection is 

 its liability to burst ; though, from the tubes being 

 of malleable iron, such an accident causes more 

 inconvenience than serious danger. 



Conservation of Warmth. 



The art of warming embraces not only the pro- 

 duction and distribution of heat, but the construc- 

 tion of apartments with a view to prevent its 

 escape. The way to effect this setting aside in 

 the meantime the necessity of renewing the air 

 is, in the first place, to make the walls, floor, 

 windows, doors, &c. as impervious to air as 

 possible, to prevent the heat from being carried 

 off by currents ; and, in the next place, to make 

 them bad conductors of heat. For this last pur- 

 pose, the walls ought to be sufficiently thick, and, 

 if possible, built of non-conducting materials. 

 Solid iron would make a cold wall ; wood a warm 

 one ; and in this respect brick or porous stone is 

 preferable to hard stone. But the chief element 

 in a warm wall is that it be double, which every 

 wall in effect is, when it is lined by a coating of 

 plaster, kept apart from the wall itself by the 

 laths. The plate of confined air between the two 

 is the most effectual barrier to the passage of 

 the heat outwards that could be contrived. By 

 making iron walls double or cellular, with a lining 

 of plaster, they might be rendered as warm as 

 wished. Windows are a great source of cold, 

 not merely by admitting cold air, but by allowing 

 the heat to pass by conduction through the thin 

 glass. The air of the room that touches the 

 window is robbed of its warmth, and is constantly 

 descending in a cold stream towards the floor. 

 There is thus a cold influence felt from a window, 

 however close it is. This is partly arrested by 

 window-blinds, shutters, and curtains, which check 

 the flow of the air, and retard its carrying power. 

 But a far more effectual plan is to have double 

 windows ; either two frames, or double panes in 

 the same frame. The loss of heat by a double 

 window is said to be only one-fourth of that by a 

 single. Double windows are considered essential 

 in countries where the winters are rigorous. 



By carrying those principles far enough, we 

 might succeed in well-nigh imprisoning the heat, 

 and thus produce a house of ideal perfection, so 

 far as mere temperature is concerned. But for 

 the habitation of living beings, another condition, 

 seemingly antagonistic to the former, is no less 

 requisite ' air, as free as that on a mountain top.' 

 In general practice, the two hostile conditions are 

 not so much sought to be reconciled as com- 

 promised ; and then, as usual, neither object is 

 well attained. Circulation of air is got accident- 

 ally, through the imperfections of structure in our 

 rooms through the chinks and bad fittings of 

 the windows, doors, floors, and the uneconomical 

 fashion of our fireplaces. Neither the airing of 

 our houses, nor the art of building them solid 

 and warm, can advance to perfection, until the 

 former be no longer left to chance, but be in every 

 case secured by special apparatus capable of 

 direct control. We now proceed to consider how 

 this is sought to be attained ; confining ourselves 

 still to the leading principles, and only noticing a 

 few of the specific plans that have been put in 

 practice. 



VENTILATION. 



The importance of constantly respiring pure air 

 is more fully considered in the paper on PRESER- 

 VATION OF HEALTH. For our present purpose, 

 it will be sufficient to bear in mind the following 

 facts. Fresh air is chiefly made up of two gases, 

 which are everywhere found to be in the same 

 proportion : nitrogen forming about four-fifths of 

 its bulk, and oxygen forming one-fifth. It also 

 contains a very variable quantity of vapour of 

 water, and a smaller but pretty constant quantity 

 of carbonic acid gas (see CHEMISTRY) namely, 

 I part in 2000 by measure. When a portion of 

 this air has been once breathed, it is found to 

 have undergone several changes, which render it 

 unfit to be breathed again. The chief vitiation 

 consists in a portion of the oxygen being ab- 

 stracted, and nearly as much carbonic acid gas 

 substituted for it, the carbonic acid having been 

 formed by the oxygen uniting with the carbon of 

 the blood. The average quantity of carbonic acid 

 in expired air or breath is found to be 4-3 per 

 cent, by measure. Now this gas, when taken into 

 the lungs, is a poison, and tends to arrest the vital 

 processes. Like other poisons, however, it can 

 be rendered harmless by dilution. The small 

 proportion naturally existing in the atmosphere is 

 perfectly innocuous, and may be considerably in- 

 creased without sensible effect. But it is decid- 

 edly prejudicial to breathe for a long time air 

 containing I measure in 100 of carbonic acid, 

 and it is considered desirable that the proportion 

 should never exceed i in 500. As about 20 cubic 

 feet of air pass through the lungs of a man in an 

 hour, the respiration of one human being thus 

 vitiates hourly about 500 cubic feet of air. 



In addition to carbonic acid, expired air con- 

 tains an undue amount of watery vapour. Minute 

 quantities of animal matters are also exhaled with 

 the breath, which in close, ill-ventilated apart- 

 ments, form a clammy deposit on the furniture 

 and walls, and, by putrefying, become organic 

 poisons. 



A further necessity for the constant renewal of 

 fresh air arises wherever lights are burnt Every 

 cubic foot of gas consumes the oxygen of ten feet 

 of air, and forms at least one foot of carbonic 

 acid, besides watery vapour, sometimes mixed 

 with sulphurous fumes. The effectual remedy for 

 this is a large glass globe inclosing the light, and 

 having at top a metal tube communicating with 

 the chimney flue. 



In an ordinary apartment heated by a common 

 open fire, there is an imperfect kind of ventilation 

 always going on by means of the fire, which 

 draws in through the door, windows, and other 

 apertures, fresh air to supply that consumed by 

 itself, or which the chimney -draught otherwise 

 carries off. This is impel feet, in many ways ; for 

 one thing, it only operates when there is a fire 

 It therefore becomes desirable that a regulated 

 mode of ventilation, calculated to be thoroughly 

 and at all times effectual, should be applied to 

 ordinary apartments. It is not less necessary 

 that churches, court-rooms, theatres, and all large 

 halls in which great numbers of persons assemble, 

 should be subjected to a mode of ventilation, 

 regular, certain, and complete. Nor is it unworthy 

 of notice that a regular means of ventilation is 



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