524 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The examination-chamber may be made of variable sizes by the 
method shown in fig. 63. Two cover-glasses separated by caoutchouc 
rings are fixed together by 
nickel plates with central 
circular apertures, and these 
plates are kept in position 
by the clamps a. 
The temperature of the 
water-bath was found not 
to vary more than 0 • 1° C. 
in 12 hours when the water 
was kept throughout at 
50° C. 
Pfeifer’s Water Thermostat.* — Prof. W. Pfeffer describes a water 
thermostat which, as it maintains a very constant temperature, is very 
Fig. 61. 
Chamber made with nickel plates. Bisected ; 
natural size. 
Zeitschr. f. Wiss. Mikr., vii. (1891) pp. 442-7 (1 fig ). 
