57^ Of the Salubrity of Warm Rooms. 



before. And even the cold air admitted into the room 

 would in a few minutes become really warm. And 

 as the specific gravity of air is so very small, com- 

 pared with that of the dense solid materials of which 

 the walls, floor, and ceiling of the room are constructed, 

 the warming of this air will not sensibly cool the 

 room. 



Hence we see how easy it is to ventilate warm rooms 

 in cold weather, and also how impossible it would be 

 to live in such a room without the air in it being per- 

 petually changed and replaced with fresh and pure air 

 from without. 



It is those who inhabit cold rooms who are exposed 

 to the danger of breathing confined air, for it would 

 be in vain to open the doors and windows of such an 

 apartment : if the air in it is as cold, and consequently 

 just as heavy, as that without, there is no physical rea- 

 son why it should move out of its place. Part of it 

 may, indeed, be blown out by a wind, or without open- 

 ing the door and windows : a part of it may be forced 

 up the chimney, if there be a fire burning in it ; but 

 this kind of ventilation is not only dangerous in a very 

 high degree to the health of those who are in the room, 

 but it is also partial and very incomplete. As the cur- 

 rents of cold air which supply the draught of an open- 

 chimney fire are confined to the bottom of the room, 

 below the level of the mantel of the fire-place, the same 

 air may remain for weeks in the upper parts of the 

 room, and perhaps for a much longer time in some 

 remote corner, far from the fire. 



I think enough has now been said to prove to the 

 satisfaction of every reasonable person, who is disposed 

 to listen and willing to be convinced, that the air in 



