SCHEKK'S THERMO-IiEGULATOR 23 



tube-shaped vessel, supplied with a suitable amount of 

 mercury, is placed in the water surrounding the incubator. 

 On warming the water the column of mercury ascends so 

 long as the gas flows from one angular tube to the other ; 

 when, however, the temperature becomes so high that the 

 mercury reaches the longer angle tube which is obliquely 

 ground, and closes the end, then the limit of temperature 

 is fixed at which the incubator can be kept constantly. 



Safety aperture 



Mercury 



W 



Glass tube sealed in 

 Air-space 



Mercury 



FiC. 12.— SCIIENK'S THEEMO-KEGULATOn. 



Now, as soon as this opening is covered with mercury, the 

 passage of gas would necessarily cease and the flame of the 

 burner be extinguished, did not enough gas escape through 

 the lateral aperture to keep it burning. Accordingly, 

 the filling of the regulator with mercury must be done in 

 such a way that this limit is reached at the incubating 

 temperature. By pushing in or withdrawing the glass 

 vessel above the test-tube the temperature can be raised or 

 lowered a few degrees according to need. 



If the temperature of the water in which that part of 

 the apparatus containing the mercury is placed rises, then 



