RELATION OF AIR TO THE HOUSE WE LIVE IN. 205 



grains, or about half a pound, of water. Should there be no change 

 of the air, matters would remain so. But by every fresh 3,530 feet 

 of air coming into the room another half-pound of water would be 

 taken up, and so on. Suppose the change amounts to 353 cubic feet 

 per hour : all the moisture we get rid of per hour would be only 353 

 grains per hour. But if we heat the room to 68 Fahr., for instance 

 we increase the tension of the vapor, i. ., the capacity of the air for tak- 

 ing up water, from four to seven grains per cubic foot, so that each cubic 

 foot of fresh air entering the room is capable of taking up seven instead 

 of four that means four grains in addition to its original humidity 

 In consequence of this increased capacity, the 353 cubic feet of air 

 take up 1,412 instead of 353 grains of water. But by the increased 

 difference of temperature between the room and the open air, ventila- 

 tion rises from 353 to 2,100 cubic feet per hour, and in this way we 

 get rid of more than twenty times as much water as if we left the 

 room unheated. 



All kinds of stoves and charcoal-dishes act only as sources of heat, 

 and not as sources of carbonic acid. The only rational and efficient 

 way is the heating of all the chimneys and stoves, and the coiitinnal 

 ventilation of all the rooms. All other ways are of no use, or decep- 

 tive. 



You have seen that the wall has its physiology, a life of its own. 

 Perhaps you will no longer find it so strange tbat Master Quince intro- 

 duces not only a pale moonshine and a rough lion, but also a " sweet 

 and lovely wall " as a living and talking person. I had many things 

 more to tell you about the wall, but I have still another subject of 

 special importance before me the change of the air in the house, or 

 ventilation. 



We have seen already, in speaking of our clothes, that the well- 

 being of our body requires a continuous current of air to flow round 

 us, and for the same reason a flow of air must take place continually 

 from the open air through our dwellings. It used to be a current be- 

 lief that in the still air of our houses we were separated and shut oft" 

 from the external air. You know that this error arises from our nerves 

 and senses believing the air to be quite calm and motionless, although 

 there may be some movement. We must be thankful to our Crt ator 

 for this our error, else we should probably have ceased to exist. How- 

 ever anxious we may have been to shut ourselves up from the external 

 air, we still remain in connection and intercourse with it. No house 

 can have an atmosphere of its own; it has that by which it is sur- 

 rounded, which travels and flows through it slower or quicker, while 

 the house, and whatever exists and goes on in it, have no other power 

 than to render this air more or less impure. 



This pollution must not overstep a certain line, and this line de- 

 pends on the proportion between the pollution and the change and 

 volume of the air-current. 



