HOT- WAI ER FILTER 



27 



the water circulating in six rubber pipes connected in a 

 water-tight manner with the metal chest. A vertical tube 

 is so attached to the outside that the surface of the water in 

 it ascends as the temperature rises, and it contains a float 

 furnished with a lever which presses upon a bar connected 

 with the lamp and made to regulate the flame of the petro- 

 leum. When the surface of the water sinks the bar is 

 lifted and the flame increased ; 

 when the water ascends the 

 flame is diminished (Bau- 

 meyer's apparatus). 



Water-baths and sand- 

 baths, and such contrivances 

 for warming and boiling, with 

 suitable stands, gas-burners, 

 an ice-tank for refrigerating, 

 flasks, test-glasses, and funnels 

 and dishes of the most various 

 kinds are also included in the 

 equipment necessary for a 

 bacteriological laboratory. 



Hot-water filter. A kind 

 of funnel known as the hot- 



Water filtering' funnel is fre- 



quently in use when it is 

 necessary to filter in the hot state substances which become 

 solid at ordinary temperatures. Such a funnel is made of 

 copper, brass, or sheet-iron, with double walls, and fitted 

 with an appendage at the side which is warmed by means 

 of a flame ; but those hot-water funnels in which the 

 warming is managed by a ring burner surrounding the 

 lower part of the external surface are also very efficient. 

 By filling the space between the walls through an opening 

 above with water, which is then. heated, masses of gelatine 



IS. HOT- WATER FILTER (HEATED BY 

 A RING BURNER). 



