SUMMARY OF CURRENT RESEARCHES RELATING TO 
3S0 
50 
18 
^-2,5 cm 
be as tliin as possible (not too thin as it has to stand the pressure of 
about 5/6 atmosphere), that of the tube FAB should be thick and the 
tap E should be nearer D than B. This 
Fig. 45. arrangement aids first of all in prevent- 
ing the extinction of the flame when the 
thermostat gets too hot and also saves 
the apparatus from getting damaged from 
the action of the mercury on the metal 
if, as is sometimes the case, it rises 
1015 u,Hcm above the level of E. Owing to the 
sensitiveness of the apparatus it is neces- 
sary to have the lateral regulating tube 
G fairly broad, otherwise it would be 
necessary either to let out or put in 
mercury for different temperatures. 
The author then goes on to point out 
that notwithstanding a thermo-regu- 
lator may be extremely sensitive yet 
there are two principal causes which 
prevent the temperature of a thermostat 
from being constant. These are the 
irregular heating of the bottom, and the 
difference in the heat of the water mantle 
owing to imperfect mixture of the cur- 
rents. To obviate these inconveniences 
as far as possible it is necessary that all 
the burners should act simultaneously 
and in concert with the regulator ; 
secondly, that the heating of the bottom 
should be distributed evenly over the 
whole surface by the interposition of 
wire gauze ; and thirdly, that the ther- 
mostat should be covered over with a 
protective such as asbestos. The bottom 
should be somewhat conical as the heat 
is better distributed by this formation 
than when flat. 
Rousselet’s New Compressorium — 
This compressor has been devised for 
the purpose of facilitating the examination of minute living and free- 
swimming animals, such as rotifers, infusoria, &c. The accompanying 
woodcut renders a detailed description 
unnecessary. The advantages claimed 
for it are the following : — 
The glass tablet being fixed flush with 
the lower part of the brass slide, which 
is slightly countersunk, allows high- 
angled condensers to be used to the very 
edge of the tablet for the illumination 
of the. objects. 
The arm carrying the cover-glass is raised and lowered by screw 
adjustment, and is held in position by a spring catch, but can easily be 
Fig. 46. 
