ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
353 
(3) Illuminating- and other Apparatus. 
Fig. 67. 
Apparatus for Demonstrating the Effect of Lenses.*— Herr K. Haas 
describes this apparatus, which is shown in fig. 66. On a metal tripod 
is supported a prismatic box, the long side-walls of which are of glass, 
while the ends are opaque, but provided with windows for the passage 
of the light. In front of the windows 
are grooves for the reception of 
adiathermic glasses. In the box are 
two hollow lenses, one biconvex and 
the other biconcave, to which tubes 
are attached above and below. In 
the upper tubes funnels for filling the 
lenses can be inserted, while the 
lower tubes serve to empty them. On 
the box are also a feed-pipe and an 
exit-tube. When the lenses are filled 
with a refracting liquid and the box 
with smoke, the biconvex lens acts as 
a collective lens and the biconcave as 
a dispersive one, but the reverse is the 
case when the box is filled with the 
liquid. 
(4) Photomicrography. 
Acetylene and Photomicrography-! 
— Dr. H. van Heurck describes the 
acetylene gas lamps recently con- 
structed by M. G. Trouve. In prin- 
ciple they do not differ from the 
Walmsley apparatus described be- 
low, but are made of glass, and have 
no appliance for cooling and dry- 
ing the gas. The arrangement of the 
small apparatus is shown in fig. 67. 
The inner glass vessel containing the 
wire basket holding the calcium car- 
bide has a hole in the bottom, and is 
closed at the top by a caoutchouc 
stopper, through which passes a tube 
which can be closed by a stopcock. 
The inner vessel slides in the outer 
one, which contains water, 
is also made. 
The author considers that acetylene apparatus will render useful 
service to photomicrography. 
A larger 
apparatus with nickel mounting 
* Zeitschr. f. Phys. u. Ohem. Unterr., viii. (1895) p. 
Instrumentenk., xvi. (1896) pp. 94-5. 
t Bull. Soc. Beige de Micr., xxii. (1895-6) pp. 68-73. 
266. See Zeitschr. f. 
