THE NEW EARTH 



energy is recorded, so that it will be easy to 

 show just how much heat the man is throwing 

 off from his body in this way, for with every 

 movement of the body some heat is generated. 

 In the room, — a small room, seven feet and a 

 half by four feet in dimensions, and six and a 

 half feet high, — is a stationary bicycle for exer- 

 cise, in case the test is chiefly to show the 

 amount of heat developed in muscular activity. 

 Outside the room is a delicately adjusted ther- 

 mometer, so sensitive, indeed, that it will re- 

 cord any fraction of a degree of heat. The 

 observer who is keeping the record on the out- 

 side of the room does not need to look in or 

 to hear any sound from the man inside to 

 know when he rises from his chair, for instance, 

 for the act, though slight and unaccompanied 

 by any special exertion, is yet sufficient to 

 throw off enough heat to cause an immediate 

 rise in the thermometer. 



The air which the man in the room breathes 

 is tested, also, with the utmost care. It passes 

 in to him absolutely pure. It comes out im- 

 pure from his breathing, and all this impurity 

 is accurately measured by a delicately adjusted 

 apparatus. Sometimes the test will be TOUS- 



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