New Developments in Science 599 



clean, cool, and dry. If too cool, it is slightly reheated, or a little 

 warm air is added to it to bring it to the required temperature. 

 A temperature of twelve to fifteen degrees lower than that of the 

 street has been found to be more comfortable than a fixed temper- 

 ature, which might be on some days thirty degrees cooler than the 

 air outside. The conditioned air is then circulated through the 

 auditorium. An engineer is usually in charge of the air-condition- 

 ing system to watch the temperature and the humidity and to 

 make the necessary adjustments when weather conditions change. 



Air Conditioning in Schools. Probably it has never 

 occurred to you that the air in your classroom may have an 

 important effect on your ability to do good work. Tests made in 

 schools, however, have definitely proved that when the air is too 

 warm students have difficulty in concentrating on their studies. 

 They are dull and sleepy. Likewise, when the air is too cold the 

 students are uncomfortable and cannot concentrate well. A tem- 

 perature of from 68 to 70 has been found to be most satisfac- 

 tory, especially when the air is not too moist or too dry, and is 

 kept circulating. 



The condition of the air may also have important effects on 

 health. If a number of students sit for hours in a stuffy room, 

 breathing and re-breathing the same air, there is a good oppor- 

 tunity for the germs of colds and other diseases to develop and 

 spread. Hence proper ventilation is extremely important in school 

 buildings. 



Few school buildings are yet equipped with air conditioning 

 apparatus, but as time goes on it seems likely that more and more 

 will be air conditioned. It will be a real step in advance in pre- 

 venting the spread of disease and in increasing efficiency when 

 classrooms are provided with fresh, clean air at the proper tem- 

 perature and with just the right amount of moisture. 



Air Conditioning in the Home. Air conditioning in the 

 home, while practicable, has not yet come into general use, chiefly 

 because of the expense involved. It is believed by forward-looking 

 persons, however, that the manufacture of effective home air con- 

 ditioning apparatus within the reach of the average pocketbook 

 will be one of the next great advances in human comfort. 



