VENTILATION. 



the windows. It is a much disputed point where- 

 about in a room the air should be made to enter 

 some advocating openings for it near the floor, 

 others near the ceiling ; and it must be confessed 

 that neither method has yet been rendered un- 

 objectionable. One essential thing is, to prevent 

 the air from rushing in with a strong current, by 

 passing it through minute holes spread over a 

 large space. 



But the great difficulty lies in the coldness of 

 the air directly introduced from the outside, 

 whether by the doors and windows, or through 

 channels in the walls ; and all such plans of 

 ventilation must be considered as imperfect make- 

 shifts. There can be little doubt that our de- 

 scendants will look upon them as little less bar- 

 barous than we now think the arrangements of the 

 palace of Cedric the Saxon, and the ventilation of 

 Rowena's boudoir, as described in Ivanhoe. 



The fresh air ought in every case to be warmed 

 before being admitted, or, at least, before being 

 allowed to circulate in a sitting-room. In the 

 smokeless grate (fig. i), the air is led directly from 

 the outer atmosphere into a channel (i, 2) under- 

 neath the hearth, and escaping below the fender 

 and about the fire, is warmed before spreading 

 through the apartment. With stoves and heated 

 pipes, the air should enter about the heated sur- 

 face ; in stoves on the cockle principle, the fresh 

 air, as it enters, is made to pass between the 

 casings of the stove. With an open fire, a very 

 feasible plan is to make the fresh-air channel pass 

 behind the fireplace, and allow the warmed air 

 to escape from concealed openings about the 

 chimney-piece and jambs, or from behind the 

 skirting. In Condy s Ventilating-grate, the fire- 

 box is constructed of hollow pieces of fire-brick 

 communicating with the external atmosphere and 

 with the room. 



For a house with fireplaces of the usual con- 

 struction, perhaps the simplest and most effective 

 expedient is to admit the fresh air into the 

 entrance-hall, and there warm it by means of a 

 low -temperature stove or by water-pipes ; its 

 passage into the several rooms can then be pro- 

 vided for by regular channels, behind the skirting 

 or otherwise. In America, perforations are 

 frequently made in certain parts of the doors, 

 before which silk curtains are disposed so as to 

 temper the currents. It is almost unaccountable 

 that in this country the plan of warming the lobby 

 and staircase is so seldom resorted to. To say 

 nothing of the comfort thus diffused through the 

 whole house, and the benefit in point of health, 

 especially to weakly constitutions, the economy of 

 the arrangement is beyond dispute. In the sitting- 

 rooms, not more than one-half the usual quantity 

 of fuel requires to be burned in the open fires. 



Ventilation by Fans. The fan-wheel has been 

 for many years used in factories, to which it is 

 particularly applicable, from the readiness with 

 which it can be kept in motion by the engine. 

 It is essentially the same as the barn-fanners ; the 

 air is drawn in at the centre of the wheel, and flies 

 off at the circumference by centrifugal force. The 

 fan is placed at the top of a flue, into which 

 branches from all parts of the establishment pro- 

 ceed ; and when it is set in motion, it draws off 

 the air from every apartment communicating 

 with it. 



Transference of Heat from the used Air to the 



/res/t.We practise this kind of economy when in 

 cold weather we. breathe through the folds of a 

 woollen handkerchief. The breath, raised to the 

 temperature of the blood, leaves a great part of its 

 heat in the handkerchief as it passes through ; the 

 cold inspired air absorbs this heat again, and 

 enters the lungs considerably warmed. The same 

 thing is more effectually done by the wire-gauze 

 respirators invented by Jeffrey. 



This is essentially the principle of the caloric- 

 engine, or, more properly, hot-air engine, brought 

 forward some time ago by Captain Ericsson of 

 New York ; but which is merely a copy of the 

 invention of Dr Stirling of Perth, patented as 

 early as 1816. 



Whatever difficulties or impossibilities, as 

 some maintain there may be in the way of turn- 

 ing this transferred heat into a fresh source of 

 power, nothing seems simpler, in theory at least, 

 than to economise heat in this manner for the 

 warming of dwellings and similar purposes. The 

 idea originated with Dr Arnott, many years ago, 



cD?f 



W 



Fig. 6. 



who thus illustrates it in the case of water : Sup- 

 pose a a vessel of boiling water, with a thin 

 metallic tube issuing from the bottom, and having 

 a stop-cock at d; and b a similar vessel of water 

 at freezing, the tube of which is larger, and en- 

 velops the other. When both are flowing simul- 

 taneously, the hot water, if the tube is long 

 enough, will have lost all its excess of heat before 

 getting to </, while the counter-current will have 

 gained all that the other lost. In an experiment 

 with tubes six feet long, the boiling water from a 

 issued from d at 34, and the freezing water from 

 b issued from c at 210. It is clear that if a were 

 a bath, the warm water in it, after being used, 

 might in flowing out be made to heat the cold 

 water from a reservoir, , flowing into another 

 bath below c. 



It will at once strike the reader how desirable it 

 would be to do the same with the impure heated 

 air which we are obliged to eject from our dwell- 

 ings. Where the ventilation depends upon the 

 draught of a common chimney, it would seem 

 impossible to bring the entering air in contact 

 with that which is escaping; but where the 

 mechanical force of a pump is employed, nothing 

 seems simpler than to make the two currents run 

 counter to one another for a certain distance in 

 close contact through a system of tubes. 



Notwithstanding all the improvements recently 

 effected, it is beyond doubt that this important 

 branch of the art of living is still in a very rude 

 and imperfect condition. A writer in the Quarterly 

 Review for April 1866, in a very suggestive article 

 on Coal and Smoke, points to the radical error of 

 the existing system, when he remarks that ' in a 

 household fire heat is, as it were, manufactured on 

 a very small scale ; and experience has proved 

 that the cost of production of an article has always 

 been inversely proportionate to the scale of its 



489 



