18 GENERAL SCIENCE 



Schoolroom " Deserts." A usual cause for nervousness, or 

 " fidgets," among school children is the dried-out, desert-like at- 

 mosphere of the school room, the temperature of which, during the 

 winter months, is usually above 72 F. The introduction of vapor 

 into the room, through the placing of pans of water, wet cloths 

 over the radiators, opening of the steam valves, or throwing open 



FIG. 10. A Hydrodeik. 



the windows when possible, will almost instantly relieve the ten- 

 sion of a schoolroom full of children. On the " perfect days " 

 in May and early June, with all windows open, admitting freely 

 the outdoor air, it is interesting to note that the thermometer stands 

 at about 65 to 68 F., and the hygrometer registers about 60% 

 relative humidity. 



Vertical wicks of felt with their lower ends in water kept hot 



