58 Scientific Intelligence. 
gently ignited hy a spark, the cotton, in the form of yarn, smoulders 
lowly away; when set on fire by a flame, it burns up rapidly ; if 
in the form of a charge it is ignited in a mine or fire-arm, it ex- 
plodes like gunpowder similarly placed, while, lastly, . fired — 
great violence with a few grains of fulm inate of mercur y, it 1 
detonated with as much force and with the same terrible effect as 
its instigator 
More recently, our investigators have succeeded in exploding 
gun-cotton to the best advantage, when damp; and in this state 
the explosion is every bit as violent as when the — is dry. 
This discovery is of the utmost importance, as when very wet, gun- 
cotton is not only non-explosive, but positively wine 
In fact it would be as serviceable as a wet towel in extinguishing a 
fire. When Laan sk in contact, however, with a cake of dry gun- 
will explode sep _— as much energy as when confined ina 
water-tight stee 
If a line of ne cakes, placed so as to touch each other, 
are detonated at one end, the explosion will travel with a velocity 
exceeding anything we are cognizant of, with the exception of light 
and electricity. In one experiment, forty-two feet of the material 
was fired, and the velocity measured for every six feet by a Noble’s 
chronoseope. In this case the results were most uniform, for the 
velocity only varied from nineteen to twenty pee "feet per 
second.— Nature, p. 534, ee 1873. B.C. Pi 
9. Heat generated by the pl heh of hydrogen by platinum 
—: Favre claims that the dene set free ae gag 
