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of 
Protection of Persons from Fire. 99 
inflammable substances in contact with it, on the side opposite to that 
of the heating source. This is the principle of safety in the Davy 
lamp, now so extensively used by miners. It is now, we believe, 
generally admitted by chemists, that the effect of metallic gauze is to 
be ascribed to the repulsion of the flame by the metal,* rather than to 
the conducting power of the latter. The flame is thus prevented 
from coming into contact with the wire. ‘The author partakes of this 
Opinion, and he has proved that a gauze of amianthus produces a simi- 
lar effect on fame. "This appears to be the only substance of which, 
without preparation, a tissue can be made suitable for resisting flame. 
Itis true that cotton and linen cloth, well impregnated with certain 
saline solutions, are rendered almost incombustible.. Sulphate of alu- 
mina, carbonate of magnesia, and other salts, have this property; but 
‘lone, according to Gay-Lussac, are equal to phosphate of ammonia. 
na cloth well prepared with this salt is exposed to the fire, the 
salt melts, the ammonia is volatilized, and the vitrified phosphoric 
acid forms around the tissue a varnish which defends it from combus- 
ton. The cloth becomes ignited, but preserves its form and remains 
simply carbonized. 
Cuar. I—On the art of preparing amianthus, and rendering it fu 
sa | for spinning and weaving. 
No substance, artificially prepared, resists the action of heat so 
Well ag amianthus, a property conferred upon it by nature. The 
mans made much use of this material, and appear to have been 
Well acquainted with the means of preparing it, though Pliny and 
_ “tS Consider it as very difficult to work. ‘The author finds that it ° 
Sonly amianthus of a certain consistence that is fit for use. It is of- 
ten very white and shining, but too fragile. It sometimes contains 
"Nps, which cause.the fibres to be too short for spinving. 
When taken from the mine, it contains generally portions of earth 
“ other foreign matters, which must be separated by putting It into 
“tse basins full of water, where it should be left several days, sim- 
bly renewing the water from time to time as it becomes charged with 
farthy or other particles. Hot water is preferable to cold, and it Is 
advantage sometimes to boil it either in pure water or in the lye 
Of ashes, The author has tried weak muriatic acid, and other chem- 
~The metal in this case, but the gases which are evolved from flame, will, by 
“Ballist any substance, eause’a repulsion of the fame. 
