10 



BULLETIN 951. U. S. DEPAETMEN'T OF AGRICULTUEE. 



The heat-control system installed in the small high-temperature 

 boxes, which are used for the investigation of thermophilic organisms, 

 is identical with that used in the large room, except that on account of 

 the small size of these boxes no means are provided for circulating the' 



inclosed air. These small boxes, the construction of which is shown 

 in figure 7, are placed inside the large room ; consequently the tem- 

 perature surrounding them is that of the large room, 37.5° C. (99.5° 

 F.) . Owing to their small size and to the fact that their temperature 



