258 ON DYNAMITE. 
hence we find, among the solid bodies floating in the air, crystals 
of nitre and particles of black carbon. 
The injurious influence of gunpowder on the health of miners 
having been established, experiments were made with gun-cotton, 
in 1864, with the view of testing its suitability for replacing 
gunpowder in mining operations ; but without any definite result. 
Since the discovery of Nitro-glycerine by Sobrero, some 25 
years ago, chemists who had been acquainted with the compound 
saw that we had an agent of great power, if means could be 
devised for controlling it during use. It was a mere scientific 
curiosity till the end of 1864, and could not be obtained in com- 
merce. It is prepared from the slow action of nitric and sulphuric 
acids on glycerine. Perfect explosion of the chemically pure 
nitro-glycerine yields aqueous vapour, carbonic acid, oxygen, and 
nitrogen. These gases expand to such an extent as to make an 
equal bulk of nitro-glycerine 13 times stronger than gunpowder. 
Apparently we have here a powerful explosive, forming gases 
which, by Graham’s law of diffusion, would in a short time so 
intermix as to be comparatively harmless. This is, however, 
not the case. Dr. Gladstone ascertained, while engaged in his 
researches on nitro-glycerine, that the compound was safe and 
stable, only when prepared with the purest acids and perfectly 
anhydrous glycerine. Careless manufacture has produced an 
unstable compound, lable to spontaneous decomposition, accom- 
panied by the development of gases, which, by exerting pressure 
on the fluid within, have caused it to explode on such slight 
concussion as shaking the vessel containing it. 
During the slow spontaneous decomposition, various injurious 
products are formed: oxalic-, hydrocyanic-, and glyceric acids, 
ammonia, and some others unknown. From imperfect storage or 
careless manufacture, disastrous accidents became so frequent as 
to induce regulations to be made in most countries with reference 
to its storage and transit; indeed, these are so stringent as to 
almost prohibit its employment in mining or quarrying, unless 
made on the spot. That a valuable agent was in a fair way of 
being lost may be gathered from a statement made by the 
contractor of the Central Pacific Railroad, who said that in driving 
a tunnel they could go 25 per cent. faster with nitro-glycerine than 
by using gunpowder,—smaller holes, drilled in one-third the time, 
