1866. | Physics. 437 
the lowest temperature was — 20°°7 C., and the bulb of the thermo- 
meter became quickly coated with ice, condensed from the atmosphere. 
Water in a test-tube held in front of the jet commenced to freeze 
immediately. With pure ether, sp. gr. *720 C., prepared expressly for 
ansesthetic purposes, a temperature of — 21°-6 C. was produced, and 
a considerable quantity of 1ce condensed round the bulb of the ther- 
mometer, so as to impede the cooling, unless occasionally removed. 
Absolute alcohol gave a temperature of + 8°:0C. Pure methyl 
alcohol, sp. gr. *803, + 1°1C. Solution of ammonia, sp. gr. ‘880, 
— 11°C. Chloroform, — 5°1C. Bichloride of carbon, — 2°2C. Bisul- 
phide of carbon gave a temperature of —17°6 C.; large quantities of 
ice condensed on the bulb, coating it nearly +in. thick. In a few 
minutes the bisulphide of carbon ceased to issue regularly from the 
jet, and miniature snow-balls were blown out at intervals. The 
bisulphide of carbon apparently contained water. The temperature 
of the room was 18°: C. 
Most of our readers are acquainted with the ingenious apparatus 
of M. Carré for the production of a low temperature by means of 
ammoniacal gas. M. Knab has proposed a new process for its 
condensation. Chloride of calcium absorbs its own weight of 
ammoniacal gas, which is again evolved on the application of heat. 
The chloride will serve an indefinite time. M. Knab considers that 
his discovery will be found very useful: 1, Because chloride of 
calcium saturated with ammonia is a dry powder easy of transport ; 
2, because chloride of calcium is of very little value; and 3, while 
water will only hold in solution 20 per cent. of ammonia, the 
chloride will hold 50 per cent., so that the cost of sending ammonia 
about will be greatly diminished. 
Execrriciry.—M. E. Becquerel has presented to the French 
Academy a memoir ‘“ On the Thermo-electric Powers of Bodies, and 
on Thermo-electric Piles.” In his last memoir the author stated that 
bars of sulphide of copper obtamed by fusion were very differently 
endowed with electro-motive energy. He now publishes his dis- 
covery that all these bars may be made to exhibit an equal power 
by simply subjecting them, after fusion, to a dull-red heat for several 
hours. ‘The second part of the memoir is devoted to an account of 
the electro-motive force of various alloys, in which he shows that 
an alloy of equal equivalents of cadmium and antimony may advan- 
tageously replace tellurium in the construction of piles for the study 
of calorific radiation. 
M. Gerardin has described a battery of iron turnings. The 
zinc of a Bunsen’s battery is replaced by iron borings. ‘The iron is 
placed in common water. ‘The porous vessel contains a solution of 
perchloride of iron in aqua regia. The positive pole is made of 
powdered coke agglomerated with paraffine. Such a battery may 
