530 Progress in Science. (October, 
glass is placed in contact with the flat side of a plano-convex condenser, 
causes perhaps the minimum loss of light. The tinted glass placed under the 
object increases the thickness of the mounting, and prevents very oblique light 
passing through, and also interferes with the use of illuminators, such as the 
achromatic condenser, &c.; glasses within the body cause trouble and loss of 
time in fixing and removing them. The most convenient position seems to be 
above the eye-piece. For this purpose M. Mouchet has constructed a revolving 
diaphragm pierced with nine openings, each 1 centimetre in diameter. Seven 
of the openings are fitted with coloured glasses corresponding to the tin‘s of 
the solar spectrum; another with a silvered glass, according to Foucault’s 
process; and the ninth with a very finely roughed glass, which may be removed 
at will, and thus leave one opening free. This revolving diaphragm is attached 
to a ring placed on the tube which receives the eye-piece. Although M. 
Mouchet considers the apparatus useful in observations by direct sunlight, it 
seems to have been forgotten that in the employment of condensed sunlight 
the object needs protection from heat as much as the eye of the observer, and 
this is effectually done by the cell of ammoniacal sulphate of copper used by 
Dr. Woodward in modifying the illumination of objects to be photographed by 
sunlight. 
HEAT. 
M. Toselli has recently invented a cooling machine, which he terms a 
dynamic refrigerator. It consists of a revolving disc, formed of a metallic 
tube bent into a complete spiral, having one end open, and with the other end 
communicating by a hollow shaft or axis of rotation with an external tube, 
this communicating with a worm contained in a separate vessel. This worm 
terminates in a discharge-pipe, having outlet into another vessel containing 
the revolving disc. The disc is half immersed in cold water, and as the surface 
of the disc above the water is continually wet, there is exposed considerable 
evaporating surface. At the same time a stream of water is forced through 
the hollow spiral, parting with some of its heat under the influence of the 
evaporation and by radiation, assisted by a current of air from a fan worked 
by the same motive power. The stream of water lowered in temperature 
passing through the worm refrigerates the liquid contained in the worm-tub. 
The decrease in temperature is, to a certain extent, dependent upon the hy- 
grometric condition of the atmosphere. The least effect is a diminution of 
4° or 5°F., while the maximum effect in strong sunlight amounts to 32° to 33° F. 
The invention, if found practicable, will be of great service to the brewer, and 
to manufacturers, where large quantities of fluid have to be cooled quickly. 
Experiments on the joint effect of pressure and heat upon paraffin have 
been made by T. E. Thorpe and J. Young on the larger scale. 3} kilos. of 
paraffin (fusing at 46°, sp. gr. at 13° = 0°g06) yielded about 4 litres of fluid hy- 
drocarbons, of which o°3 litre boiled below 100°, 1’o litre at from 100° to 200°, 
and 2:7 litres at from 200° to 300°; there remained a solid residue in the retort, 
which, on being treated with ether, was found to have as constant melting- 
point 41°5, and‘to consist, in roo parts, of—C, 8519; H, 15°34. By the action 
of bromine, this body was found to belong to the CyH2n+2 series. The 
authors next describe the results of the fractional distillation of these fluid 
hydrocarbons. After treating the liquids thus obtained with bromine, these 
substances were found to be—Pentan, boiling-point 35°to37°; hexan, 67° to 68°, 
sp. gr. at 18°=0°6631; heptan, 97° to 99°, sp. gr. at 18°5°=0°6913; octan, 122° 
to 125°, sp. gr. at 15°6°=0°7165 ; nonan, 147° to 148°, sp. gr. at 13°5°=0°7279. 
These hydrocarbons are stated to belong to the series— 
CH,— - —CH3....(nCH2)— - —CHz3. 
To demonstrate the action of water and heat, or of heat only, upon sugar, 
200 grms. of sugar and 1000 grms. of water have been kept for some 
twenty-eight hours at the temperature of boiling water; the optical rotatory 
power of the sugar has then quite disappeared. Sugar and water have 
been enclosed in sealed tubes and kept for about thirty days at the tem- 
perature of boiling water, with the result that the sugar had become entirely 
converted into an uncrystallisable compound, probably identical with that 
