238 Intelligence and Miscellaneous Articles. 



number of insoluble crystalline compounds may be produced similar 

 to tbe natural ones. The first consists in slowly oxidizing a body 

 in a solution of substances, upon which the oxide formed reacts, 

 and whence result oxides and various crystallized insoluble com- 

 pounds. The second relates to the feeble reactions which take place 

 when a slightly soluble body is placed in contact with a solution 

 containing several compounds, giving rise to double decomposition, 

 in which case insoluble compounds are formed, which crystallize. — 

 Comptes Rendus, Feb. 1S52. 



eloin's improved miner's safety lamp. 



Important as was the discovery by Sir Humphry Davy, of the 

 property possessed by [thin wire-gauze to prevent the passage of 

 flame, yet it could hardly be expected that the details of any arrange- 

 ment embodying this principle could be at once made perfect. 

 Attempts to improve the structure of the original Davy lamp have, 

 therefore, been numerous ; but few of them have been generally 

 adopted ; and in most of our collieries the original form of lamp is 

 still used. 



The principal defects of the common Davy lamp are, — first, defi- 

 cient light, rendering the collier always unwilling to use it, unless 

 compelled by the presence of a highly explosive atmosphere ; second, 

 liability of injury to the gauze of the cylinder, either by a blow from 

 a pike, a fall to the ground, or otherwise ; third, the possibility of a 

 current of explosive atmosphere being carried through the gauze 

 cylinder, either by the swinging of the lamp in the hand of a person 

 when walking, or by its being exposed to the powerful blowers of 

 gas, which are sometimes given off with great force ; fourth, the 

 heating to redness of the gauze, by which explosions actually take 

 place, from the contact of the explosive atmosphere with the heated 

 wire. This danger is often increased by the presence of small 

 particles of coal-dust, which, floating in the air of the mine, attach 

 themselves to the gauze ; and also from the deposit of soot on the 

 gauze, arising from the imperfect combustion of the oil, which in 

 the common Davy lamp always gives off a dense column of smoke. 



In the improved lamp of M. Eloin these defects are obviated. In 

 reference to light, the cylinder above the flame is closed, and air is 

 admitted only below the flame, through a narrow breadth of gauze ; 

 but the air which is admitted is brought into actual contact with the 

 flame, by the application of a cap, on the principle of the solar 

 lamp ; and thus perfect combustion is produced and light given off 

 equal to at least five or six ordinary Davy lamps. As to the liability 

 of injury to the gauze, this is obviated by using, first, a strong 

 short cylinder of glass, through which the light passes, capped over 

 the flame with a brass or iron cylinder, which cannot be injured 

 except by actual violence. It might be supposed that the glass 

 portion of the cylinder would be liable to accident; but in practice 

 this is not found to be the case : bound, at top and bottom, by a 

 strong brass ring, if it were even to crack, either from a blow, or from 

 unequal expansion by heat, no danger would result, as the pieces 

 into which it would be separated would still be held together by 



