Chemical Science. 3S3 



inattention to a rule established in the collieries, that no hewer 

 approach his work without a Davy in proper order. Rendered 

 careless by tlie fancied absence of all danger, this precaution 

 was neglected, and the gas which had, from some unforeseen 

 circumstance, accumulated during the night, inflamed. The 

 two surviving men, with a little dog, were taken out thirty-six 

 hours after the explosion, from a cavity in the working, to 

 which they had retreated, where the air was rendered so 

 impure, a light would not burn in it. Five others who retreated 

 with them, had not been able to survive the coldness of the 

 place, the badness of the air, deprivation of food, and the 

 other circumstances that surrounded them in this miserable 

 situation. 



20. Brittleness of Glass. — A method has lately been published 

 of rendering glass less liable to break by sudden changes of 

 temperature within a certain range. It is to be heated in water 

 up to the boiling point, and then allowed to cool slowly. This 

 method, tried experimentally here, has not succeeded in a 

 single instance. 



21. Rotation of Camphor, &c. — M. Virey has, in the Journal 

 dePharmacie, Mai, 1819, attributed the rotation of small pieces 

 camphor, S^c. placed on the surface of clean water to the 

 influence of electricity. His principal argument is, that if a 

 point of iron, or other metal, be brought near one of the re- 

 volving pieces, its motion is arrested immediately in a remark- 

 able manner. From, the circumstances that the particles of 

 some bodies, as camphor, resins, Sfc, attract each other, 

 whilst others, as gum tragacanth, repel each other, an idea of 

 polarity is entertained and advanced. 



22. Effect of the Sun's rays on Magnetism. — Colonel 

 Gibbs, in a letter to the Editor of the American Journal of 

 Sciences, relative to the influence of light on magnetism and 

 magnets, says, that having kept his magnet in the dark, and 

 lying down, for a long time, he determined its power ; he then 

 exposed it to the sun's rays, lying down and remote from the 

 iron support. In forty minutes it gained 12oz. in power, and in 



2 C 2 



