ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 
233 
a stirrer worked by the arm h, the liquid passes through a short 
wide tube a into the observation tube, which is shown in section 
in fig. 18. This tube is contracted and flattened out opposite the 
objective, and the side walls are cut away and replaced by plate glass 
dd, through which the light from the lamp e, after reflection at 
the mirror / and passage through the nicol g, can enter into the body- 
tube A. 
The substance under observation is contained in a thin capillary 
tube c c, w’hich passes through a cork h in tbe cover of the observation 
tube. It is closed below, but terminates above in a funnel-shaped 
opening, i and h are two wires, 
attached to two binding-screws, 
which transmit the electric current 
through the fine wire spirally 
wound round the capillary tube at 
the position of 'observation. By 
the passage of the current the 
temperature is locally and for an 
instant considerably raised. One 
wire h is insulated from, while 
the other is directly connected 
with, the cover. A thermometer 
with small bulb close to the 
capillary tube serves to register 
the temperature. The hot water 
or paraffin passes from the tube a 
(fig. 17) into the exhaust tube 
m m of the pump, and from this 
through the tube n back into the 
reservoir B. To protect the ob- 
server from the hot gas-flame, the 
reservoir is surrounded by a 
screen of asbestos x. The reser- 
voir is provided with a Reichert’s 
temperature-regulator O, which 
automatically keeps the gas-flame 
at the right height. 
The wheel y which drives the 
pump is put in motion by a small 
gas motor stationed on the ground 
away from the wall on which the 
Microscope is mounted. By means of a strap the gas motor also drives 
the stirrer. For examining under high pressures the capillary tube 
c c can be put in connection with a Cailletet pump by means of the 
capillary tube s (fig. 18), which passes into the small metal reservoir v, 
closed above by the cover u screwed on air-tight, and below by the 
stopper t, in which the capillary tube cc is fixed with shellac. t is 
so high that it can be fastened after removal of the cover u. The 
open space w contains glycerin from the Cailletet pump. The whole 
is supported by the clamp 2 :, sliding on the rod D, which is provided 
with a second clamp r for holding the observation tube, while it is itself 
Fig. 18. 
