126 SUMMARY OF CURRENT RESEARCHES RELATING TO 
being connected with the rubber tube b and the other with a clamped 
tube t plunged into a vessel filled with water. The large reservoir C 
is filled with ether and water, the small reservoir h with mercury and 
water. The water in tho apparatus is distilled. The boiler must 
always stand at a lower level than the thermostat, in order that the 
heated water may flow upwards easily. The apparatus is regulated 
Fig. 14. 
for any desired temperature by raising or lowering the small reservoir 1c, 
if the difference do not amount to more than 2°; if, however, higher 
temperatures be desired, the clamp at t is undone and some water 
allowed to escape from the reservoir C ; if a lower temperature be 
required, the petroleum lamp is removed, the clamp at t opened 
and some water allowed to be sucked in from the glass vessel. The 
general principle of the regulator is that as the water in the jacket 
