200 ELEMENTARY SCIENCE 



virtue in sleeping either with the windows open, or out-of- 

 doors. Many modern houses have specially constructed 

 sleeping porches, and these usually repay in health far more 

 than they cost in money. 



The health problem in house construction is evidently 

 to provide adequate shelter, and at the same time pro- 

 vide as far as possible the health conditions of out-of-doors; 

 it is to shut out the outdoor conditions which are disagree- 

 able, and to admit those which are agreeable; it is to 

 exclude cold and dampness, and at the same time to admit 

 fresh air. But how are we to shut out the cold, without 

 at the same time shutting out the air? They are, for 

 practical purposes, one and the same thing. It is evidently 

 a rather complicated problem. It is the problem of com- 

 bining good heating with good ventilation. By ventila- 

 tion is meant the delivery of fresh air and the removal 

 of that which is impure. In warm weather, of course, 

 this problem is simple, for then we can leave the doors 

 and windows open as much as we like, closing them only 

 to keep out rain and dust. But in cold weather this prob- 

 lem is always with us, and, to get satisfactory results, 

 every member of the household should understand thor- 

 oughly the heating system which is used, and the rules 

 which should be observed in controlling it. 



Heating. The log cabins of the early settlers were 

 heated by the burning of wood in open fireplaces, and it 

 was around the hearthstone that the family life centered. 

 So the fireplace came to mean more than merely a place 

 to keep warm. It was a place for rest and friendliness; a 

 place for story-telling, and for the entertainment of a guest. 

 It is a place which seems to soothe the heart of man, 



