THE INCUBATOR 



147 



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 in 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 

 purpose for which it is constructed will not be served. 

 When the chamber between the walls is filled with water 

 heat is supplied by a gas-flame placed beneath it. 



FIG. 29 



Koch's safety burner. 



The burner employed in heating the incubator was orig- 

 inally devised by Koch, and is known as '* Koch's safety 

 burner" (Fig. 29 1 ). It is a Bunsen burner provided with 

 an arrangement for automatically turning off the gas-supply 



1 There are now many modifications of the original form. 



