[BARNEs ] DEPRESSION OF THE FREEZING-POINT Al 
microscope (0) having a micrometer scale in its eye-piece. Forty div- 
isions of the micrometer scale corresponded to one division on the ther- 
mometer scale, A small incandescent lamp (J), driven by a current from 
five Edison-Lalande cells, was employed to illuminate the thermometer 
stem, so that aclear image of the mercury meniscus might be obtained, 
as the natural light in the basement room was insufficient for this pur- 

Fie. 1. 
pose. The microscope was mounted on a heavy upright stand, and both 
it and the lamp could be raised or lowered according to the position of 
the mercury. 
The freezing-tubes consisted of an inner and outer tube ; the inner 
contained the solution whose freezing-point was measured. In the cork 
of the inner tube the thermometer was firmly fixed, so that when in 
position its bulb was within 2 cm. of the bottom of the tube. The inner 
freezing-tube was 28 cm. in length and 2°8 cm. in diameter, and had its 
lower end re-entrant. The outer tube was 25 em. in length and 3:15 cm. 
in diameter. The thickness of the glass was about 1 mm. The air- 
space of about 1°5 mm. between the tubes was found to be quite sufficient 
to prevent the formation of ice on the wall of the tube. The inner tube 
was supported in the outer by means of two rubber bands, one at the top 
and the other at the bottom. These bands also prevented the walls from 
