224 



TJie Principles of Ventilation, 



This hall is supplied with fresh air taken from the outside and heated 

 to about G0° by passing over coils of Gold's steam radiators, and thence 

 through a register capable of supplying 12,000 cubic feet of air per 

 hour. This is distributed into all the rooms by means of open doors 

 and transoms. The parlor and sitting-room are each heated by in- 

 direct radiation described for main hall. The dining-room and all the 

 chambers are heated by radiators placed in the room. Each room has 

 an open fire-place, and, to insure perfect circulation in the flue, there 

 is a coil of steam-pipe in each flue, so that in case the fire-places are 

 not used, the process of ventilation is not interrupted. By these means 

 a continuous supply of fresh warm air enters the rooms and the foul 

 air as continuously passes out through the fire-places. All the cham- 

 ber doors have head-lights opening into the hall, which remain open, 

 thus supplying a sufficient amount of warmed, fresh air to all sleeping 

 apartments. The temperature in all rooms is about 65° Fah. 



Ventilation by motors consists in forcing air into the rooms of a 

 building by fans, or drawing it out by fans, or both, or using a fan to 

 supply fresh air and an exhausting chimney to withdraw it. The 

 heating is accomplished by causing the air to pass through a chamber 

 containing steam-pipes, either before it passes through the fan, or, 

 preferably, after. Air may be cooled in summer by passing around 

 pipes containing cold water. The ventilating system of the Ne\v 

 Capitol includes two sets of fans — one forcing air into the rooms and 

 the other drawing air out ; and in addition each office has an open 

 fire-place. In the Johns Hopkins Hospital a fan is used to supply air, 

 and the withdrawal is effected by a stack, at the bottom of which a fire 

 is kept burning. 



Many devices have been patented and are for sale, claiming to be 

 more or less efficient in compelling an air movement in a given direc- 

 tion. Of all of these it may be ^aid that in calm weather they are no 

 better than a simple open pipe, and many of them are worse, by reason 

 of the obstruction they offer to the escape of air. It is equally true 

 that when the wind blows they assist the movement of air very ma- 

 terially. Ecvolving cow^ls are liable to gather rust about the axis, and 

 be sluggish intheirmovement,givingchanceforareversal of the column 

 of air which they control. One piece of apparatus, claimed to be a 

 ventilator, should be mentioned on account of the curious faith in its 

 efficacy shown by numbers of people. It consists of a flat, circular fan- 

 wheel fixed in an aperture in a sheet of metal that replaces a pane of 

 glass in a window. When its cover is removed it commences to re- 

 volve, increasing its speed until, if there is considerable difference in 

 temperature, it whirls very rapidly, emitting a loud hum, and seeming 

 to be very energetically at work. A moment's reflection must convince 



