424 Chronicles of Science. [July, 
course, is limited to transparent crystals, but might be employed 
when the usual methods are not practicable. At the conclusion of 
the meeting, crystals containing fluid were exhibited under the mi- 
croscopes, and the expansion of the fluid by elevating the tempera- 
ture of the crystal whilst under examination. 
Heat.—The intense heat of the voltaic arc has been utilized by 
M. Le Roux for increasing the amount of light emitted by the 
incandescent carbon poles. By placing the base of a cylinder of 
magnesia, about eight millimetres in diameter, at a little distance 
from the carbon points, so that the are may just touch it, the mag- 
nesia acquires a degree of incandescence comparable to that part in 
the bordering carbon craters. At the same time the light acquires 
a remarkable degree of constancy. 
M. P. Pellogio has described a contrivance by means of which 
the troublesome “ bumping” peculiar to certain liquids when under 
distillation may be entirely prevented. It consists of a glass tube, 
as wide as practicable, inserted through the tubulus, and reaching 
nearly to the bottom of the retort, and having the upper end bent 
at a right angle, and drawn out to nearly capillary dimensions, thus 
establishing a communication between the outer air and the interior 
of the retort. With the help of this arrangement such liquids as 
methylic alcohol, sulphuric acid, petroleum residues, &c., distil as 
smoothly as alcohol or water. 
A memoir on the physical properties and the calorific power of 
petroleum and mineral oils has been brought before the Academy 
of Sciences by M. Deville. The mineral oil was submitted to dis- 
tillation in a copper alembic furnished with a long worm tube, 
and also with a thermometer. By means of this apparatus the 
amount of distillate passing over at various temperatures was - 
estimated. The possible danger by explosion was measured by the 
proportion distilling below 140°. The same experimental fact 
represents as well the loss which must be sustained to remove the 
explosive property of theoil. Another danger is encountered when 
the oils are enclosed in air-tight vessels—explosion by dilation. 
The amount of space necessary to be left above a mineral oil is 
calculated from the co-efficient of dilation. The data M. Deville 
has obtained from each sample are drawn generally from the follow- 
ing determinations. Loss by heating to 100°, to 120°, and so on, 
by intervals of 20° up to 200°; this is expressed in percentages. 
Composition of the oil, ¢7.e. percentages of carbon, hydrogen, and 
oxygen, obtained by combustion. Density at zero, and at 50°, and 
co-efficient of dilation. Composition and density of the oil obtained 
by distillation, and density of the residue. In some cases the 
specific heat has been determined, and the latent heat at the mean 
