ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
581 
(3) The rotation about the axis of tlie vertical rod b allows the 
instrument to be moved aside for the purpose of observing the prejiara- 
tion with the naked eye. 
(4) The length of the tube causes 
the head to be at a greater and 
more convenient distance from the 
preparation. 
Instead of the monocular Micro- 
scope, the authors have used with 
much more advantage a binocular of 
the form shown in tig. 83. The two 
tubes, converging on a point about 
25 cm. from the eye of the observer, 
are cast in one piece out of alumi- 
nium bronze. The two objectives 
have a special holder so that they 
■can be adjusted to suit a difference 
in the eyes. The binocular can if 
necessary be converted into a mono- 
cular by removing the two objectives 
and attaching another by means of 
the connecting piece m, as seen in 
tig. 84. The axis of the single tube n is then adjusted parallel to the 
rack by means of a rotating disc. 
C3) Illuminating- and other Apparatus. 
New Hot-Stage with Regulation for Constant Temperature.* — 
Dr. W. Behrens has devised a hot-stage in which the regulation of the 
temperature depends upon an entirely new principle. 
The new stage consists of a metal box (fig. 85) which can be 
firmly screwed to the Microscope stage by the two clamping screws h. 
In the cover in the centre is a hole through which the objective projects. 
On one side of this is a narrow slit closed by a glass plate through 
which can be seen the thermometer t placed in the interior of the box, 
while at c and b are openings closed by metal caps. 
The base-plate has a sufficiently broad piece cut out of it, so that it 
only rests upon the Microscope stage at the front and back, and leaves a 
hollow space in the middle in which the preparation can be inserted. 
On the left side face of the box is the inlet tube a provided with a cock h, 
and opposite to it on the right-hand side is the exit tube d. Both tubes 
are movable inwards and can be fixed in position by the clamping screws 
s and s\ The exit tube possesses also an adjusting arrangement i w'ith 
a division like the correction arrangement on objective-systems. 
The method of using the apparatus in order to obtain a constant tem- 
perature is simple. The reservoir B (fig. 86) which is supplied with water 
by the funnel D is connected by the bent glass tube E and indiarubber 
tubing F with the inlet tube a. A piece of tubing G of convenient 
length is attached to the exit tube d for carrying off the water which 
has passed through the apparatus. The cock h is opened and water 
* Zeitschr. f. wiss. Mikr., xii. (1895) pp. 1-15 (4 figs.). 
2 Q 
Fig. 84. 
1895 . 
