"S'PONTA NKO US GEN Eli A TION. 



579 



We have now "to devise a means of testing the action of 

 spontaneously purified air upon putrescible infusions. 

 Wooden chafti'bers, or cases, are accordingly constructed, 

 'having glass fronts, side- windows, and back-doors. 

 'Through -the bottoms of the chambers test-tubes pass air- 



tight; their open ends, for about one-fifth of the length of 

 the tubes, being within the chambers. Provision is made 

 for a free connection through sinuous channels between 

 the inner and the outer air. Through such channels, 

 though open, no dust will reach the chamber. The top of 

 each chamber is perforated by a circular hole two inches in 

 diameter, closed air-tight by a sheet of india rubber. This 



