THE INCUBATOK. 



93 



On the side is a 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 arrange- 

 ment, 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. The 

 apparatus should be kept filled with water, otherwise 

 the object for which it is constructed will not be accom- 

 plished. When the chamber between the walls is filled 

 with water the apparatus is heated from a gas-flame 

 which is placed beneath it. 



FIG. 17. 



The burner employed in heating the incubator is 

 known as " Koch's safety burner" (Fig. 17). It is a 

 Bunsen burner provided with an arrangement for auto- 

 matically turning off the gas supply and thus preventing 



