THE INCUBATOR. 



113 



water-gauge for showing the level of the water between 

 the walls. The object of the water chamber, which is 

 formed by the double wall arrangement, is to insure, by 

 means of the warmed water, an equable temperature at 

 all parts of the apparatus — at the top as well as at the 

 sides, back, and bottom, and the apparatus should be 

 kept filled with water, otherwise the purpose for which 

 it is constructed will not be accomplished. When the 

 chamber between the walls is filled with water heat is 

 supplied from a gas-flame placed beneath it. 



Tig. •n. 



Koch's safety burner. 



The burner employed in heating the incubator was 

 originally devised by Koch and is known as " Koch's 

 safety burner " (Fig. 27). It is a Bunsen burner pro- 

 vided with an arrangement for automatically turning 

 off the gas supply and thus preventing accidents should 



