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Scientific Intelligence. 
been long considered as an objection to the ingenious pyrome- 
ter, invented and used by Mr Wedgewood. Mr Sivright of 
Meggetland, has lately made some experiments on the Agalma- 
tolite or figure-stone of China, and has found that it is capable 
of standing a great heat, and of contracting its dimensions very 
considerably. He therefore proposes to substitute it in place 
of clay in Wedgwood’s pyrometer. 
11. Spontaneous Explosion qf Chlorine and Hydrogen. — It 
It has been long known that a mixture of chlorine and hydro- 
gen explodes when exposed to the direct action of the sun’s 
rays. In order to try if this effect could be produced by the 
radiation of a common culinary fire. Professor Silliman filled a 
common Florence oil-flask (well cleaned,) half full of chlorine 
gas, and was in the act of introducing the hydrogen in the 
pneumatic cistern. “ There was not only no direct emanation 
from the sun, but even the diffuse light was rendered much 
feebler than common by a thick snow-storm, which had covered 
the skylight above with a thick mantle, and veiled the heavens 
in a singular degree for such a storm. Under these circum- 
stances, the hydrogen was scarcely all introduced before the 
flask exploded with a distinct flame ; portions of the glass stuck 
in the woodwork of the ceiling of the room, and the face and 
eyes escaped by being out of the direction of the explosion ; 
nothing but the neck of the flask remained in hand. This 
occurrence then proves, that a mixture of chlorine and hydro- 
gen gas may explode spontaneously even in a diffuse light, and 
even in a very dim light.”— Journal of Science.^ 
Vol. III. No. k. p. 343. 
12. Heat produced in the Shin hy Chlorine. — Dr Hare of 
Philadelphia has found, that when the temperature of the air 
is about 60°, the hand, when immersed in chlorine, experiences 
a sensation of heat equal to 90° or 100°, even though the com- 
mon thermometer should not be affected when immersed. Dr 
Hare conjectures, “ that a sort of chemical action may take 
place between the gas and the insensible perspiration of the 
skin, as the power of chlorine in dissolving animal effluvia is well 
known.” — American Journal of Science Vol. III. No. 2. p. 344. 
13. Tests for Arsenic. — Dr Porter of the University of 
South Carolina, considering Scheele’s Green, as a test that has 
