92 



BACTERIOLOGY. 



The whole apparatus is encased in either abestos boards 

 or thick felt to prevent radiation of heat and consequent 

 fluctuations in temperature. In the top of the chamber 



FIG. 16. 



is a small opening through which a thermometer pro- 

 jects into its interior. At either corner, leading into the 

 space containing the water are other openings, for the 

 reception of another thermometer and a thermo- regulator, 

 and for refilling the apparatus as the water evaporates. 



