ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
651 
A Microscope built on the plan here outlined need not be e* 
pensive, and would be capable of all but the highest class of angular 
work. It may be conveniently used in its simplest form, and is at the 
same time adapted for the successive addition of those accessories 
essential to the prosecution of advanced researches with the instru- 
ment. Should it prove to answer my expectations I may refer to it 
again.” 
C3) Illuminating: and other Apparatus. 
Altmann’s Thermoregulator.* — Herr P. Altmann has devised 
a very simple instrument for regulating temperatures below 100° C. 
The instrument works with 
great precision, not varying p IG< 72 . 
more than ± 0*05° C. 
From the illustration it is 
seen to be made in a single 
piece. D is the reservoir 
fitted with mercury; this is 
narrowed above to a capillary 
tube, which at the side is in 
connection with a tube fitted 
with an air-tight iron screw S, 
which serves to regulate the 
apparatus for any desired tem- 
perature. 
The way the instrument 
works is easily conceived from 
the illustration. When the 
reservoir D is heated, the 
mercury therein expands, and 
rising, cuts off, in the Y tube 
of A, the stream of gas passing 
along in the direction BAC 
and only allows the transit of 
the small current along B E C. 
At E is a tap for regulating 
the supply of gas for keeping 
the burner just alight, and 
this is adjustable for any size 
of flame. 
The instrument depends for its sensitiveness and accuracy on the 
large surface of the reservoir, so that the tube at A is opened or closed 
with great facility. 
Metallic Thermoregulators.f— M. P. Miquel describes two thermo- 
regulators, the action of which is determined by the expansion and con- 
traction of metal bars. The bars, made of zinc, are from 25 to 50 cm. 
long, and are inserted in porcelain or glass tubes. The tubes are 
* Centralbl. f. Bakteriol. u. Parasitenk., ix. (1891) pp. 791-2 (1 fig.), 
f Annales de Microgr., iii. (189Q) pp. 150-8 (2 figs.); iii. (1891) pp. 241-6 
(2 figs.) and 363-74 (1 fig.). 
