98 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
project two tubes a Z>, the ends of which nearly meet inside, and the 
direction of which is obliquely upwards. Above these internal openings 
is a transverse bar c, from which is suspended the valve c d, and this 
when hanging free covers the mouth of the tube a, and the heat escapes 
through h. When, however, 
Fig. 13. c e is pressed down, the valve 
cd closes the aperture to h, 
and then the heat from the 
lamp escapes through a. If, 
therefore, a thermostat be 
connected with 6, it can be 
warmed or cooled by the action 
of this valve. This action is 
governed by the electro- 
magnet. When the current is 
closed and the bar/drawn down 
by attraction, the latter pulls 
on ge and the valve closes h. 
The opening and closing 
of the current is effected by 
means of a vessel filled with 
500 g. of mercury. This 
vessel, w'hich is placed within 
the water-mantle of the thermostat, has a narrow tube let into it. 
Within the narrow tube, and also in the vessel of mercury, are placed 
two platinum wires ; these are connected with magnet and battery. 
When the temperature rises the mercury ascends in the narrow tube and 
reaches the platinum wire. Hereby the current is closed and the 
entrance to h also, and therefore the access of heat. As the thermostat 
cools the action of the valve is reversed and the heat again enters. The 
apparatus regulates to about 1/2°. 
Krutickij’s Microspectroscope.* — Herr P. Krutickij describes a 
micro-spectroscope which he invented sixteen years ago. Placed between 
the stage and the mirror it throws an objective spectrum on the slide, 
which is seen at the same time as the preparation examined. In order 
to facilitate the employment of any magnification which may be required, 
it is necessary to narrow the slit of the spectroscope in proportion to the 
magnification of the object. This is effected by screwing to the spectro- 
scope an objective of the same power as that with which the object is 
observed. The spectroscope itself consists essentially of a combination 
of three prisms (two of crown-glass, the middle one of heavy flint-glass). 
The light is thrown from the mirror on to the slit (which is protected 
by a glass plate and can be narrowed to any extent by a screw), and is 
then concentrated by a lens on the prisms, dispersed by them, and 
thrown through the objective as a microscopically small spectrum upon 
the slide. The apparatus is provided with a divided ring, by turning 
which the slit is brought into the focus of the objective ; and a con- 
trivance to move the spectrum in a horizontal position in the field of view. 
* Script. Bot. Hort. Univ. Imp. Petropolitanm, ii., pp. 35-40, 1887-8. See Bot. 
Centralbl., xl. (1889) p. 10. 
