514 SUMMARY OF CURRENT RESEARCHES RELATING TO 
will be found to bang steadily in one position, and on examining the 
thermometer at intervals the inside of the chamber will be found to 
remain steadily at one temperature. 
Fig. 46. 
Hearson’s Patent Cool Biological Incubator for Gelatin Cultures 
— This incubator consists of a water-jacketed chamber, surmounted by 
a vessel B (fig. 47) which contains ice, the whole apparatus being sur- 
rounded by a thick layer of non-conducting material and wood to pro- 
tect it as far as possible from the effects of external influences. The 
regulation of temperature within the chamber is effected by a small 
stream of water which runs continuously through the apparatus in one of 
three directions, the choice being automatically determined by a thermo- 
static capsule. On the top of the apparatus is a lever plate and lever M, 
similar to the one used in the lamp incubator already described, only, 
in this case, the damper is dispensed with. A bracket screwed to this 
plate supports a vertical shaft, pivoted on centres at the top and bottom, 
which carries a horizontal tube C. In the incubating chamber is a cap- 
sule in a holder, supported by a tube screwed to the lever plate. A 
