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POPULAR SCIENCE REVIEW. 
evolving heat : one of them is obtained from a solution of bromide, and 
the other from a solution of iodide of antimony,” and has given “additional 
information respecting the peculiar heating-antimony obtained from the 
aqueous terchloride.” The manifestation of heat is greatest with the one 
from the chloride solution, and least with that from the iodide. An ex- 
planation is also suggested of the mode of formation and action of these 
singular heat-giving substances. 
Dr. Frankland has made various experiments on the“ Igniting Point of 
Coal-gas,” and has found that coal-gas cannot, even under the most 
favourable circumstances, be inflamed at a temperature below that neces- 
sary to render iron very perceptibly red-hot by daylight in a well-lighted 
room, but this is considerably below a red-heat visible in the open air on a 
dull day ; and this high temperature necessary is chiefly due to the 
presence of olefiant gas and other hydro-carbons in the coal-gas. Ex- 
plosive mixtures of coal-gas and air may be inflamed by sparks from 
metal and stone, as from the tools of a workman excavating the ground, 
&c. Explosive mixtures of the gas of coal-mines and air require a far 
higher temperature for ignition than similar mixtures of coal-gas and air ; 
and, therefore, the use of the safety-lamp is far more effectual in the 
former case than it would be in the latter. 
The last ascent of Mr. Glaisher in a balloon, at Wolverhampton, is full of 
interest : he ascended to the unprecedented height of upwards of six miles, 
the reading of the barometer being at that height about eight inches ; the 
temperature of the air was exceedingly low, at least thirty-seven degrees 
below the freezing-point of water ; the readings of the instruments at the 
very highest point were rendered impossible by Air. Glaisher having 
become quite unconscious, and Mr. Coxwell, the aeronaut, nearly so, indi- 
cating that an altitude of between five and six miles is nearly the limit of 
human existence. 
Professor Cliadbourne, of America, has shown that, if a spoonful of 
dry powdered ice or granular snow be thrown into a smooth glass vessel 
nearly filled with water slowly boiling, strong ebullition is produced, the 
particles of ice or snow acting like particles of iron or sand would under 
similar circumstances. 
A discourse was recently delivered, at the Royal Institution, by Mr. 
Faraday, “ On Gas Furnaces,” and was chiefly devoted to an explanation 
of the construction and action of the “ Regenerative Gas Furnace” of 
Mr. W. C. Siemens, of London. This arrangement of heat-generator is 
rapidly becoming employed for all great furnaces where a very high 
degree of heat is required, such as in iron puddling, iron-tube welding, 
glass-making, &c., chiefly in consequence of its economy in enabling the 
very commonest kind of coal (called “slack ”) to be employed instead of 
a better quality, and with the production of a very much greater degree 
of heat, — so great, indeed, that on several occasions, when its manage- 
ment has been neglected, the most refractory clay-vessels have been 
softened and destroyed. 
