HOW JACK'S WONDERFUL HOUSE BUILDS ITSELF 7 



use of hickory and mahogany where softer timber 

 would answer the purpose better, how much of his 

 time and money would be wasted ! Like oak, some 

 foods give a great deal of strength and endurance, 

 and so are much needed in the House that Jack Has. 

 Of other foods, our bodies require only a little to assist 

 in their growth. Still others are of very little value 

 in large quantities, because so much labor is required 

 in making use of them. 



We know that water is needed in preparing the 

 plaster and cement in an ordinary house. This fluid 

 is far more important in the House that Jack Has. 

 Indeed, this wonderful house could not get on com- 

 fortably a single day without water. Later we shall 

 see how very useful this sparkling liquid can be 

 made in keeping both the outside and the inside of 

 our bodies clean and wholesome. 



A carpenter could hardly tell the material most 

 necessary for him to have always at hand. He 

 would say that it would depend on the kind oi house 

 he was building. But in these houses of ours that 

 build themselves, the one thing that should always 

 be ready for use, if the best building is to be done, is 

 pure air. We cannot have too much of it, nor is 

 there a moment during the day that we do not need 

 this precious material. 



