L. MECHANICS AND ENGINEERING. 457 



twist, as ordinarily constructed, the pressure varies from 

 twenty- nine tons at the beginning to twenty -six tons at the 

 muzzle. Among the other results at which he arrives, he 

 states that in the ten-inch gun the pressure on the studs due 

 to rifling is but a small fraction (about two and a quarter 

 per cent.) of the pressure required to give translation to the 

 shot, and that the increment of the gaseous pressure^ or the 

 pressure tending to burst the gun, due to rifling, is exceed- 

 ingly small. Both in the case of the uniform and the para- 

 bolic rifling these theoretical results are entirely confirmed 

 by the experiments of the Explosive Committee of the Ord- 

 nance Bureau, who have found no sensible difference of press- 

 ure in the ten-inch gun as fired in the rifled and unrifled 

 state. 3Iiniits of Royal Artillery Institutioii^Ylll., 367. 



SILICATE COTTON. 



Krupp, of Essen, the well-known cannon manufacturer of 

 Germany, employs a preparation which, under the name of 

 silicate cotton, he considers to be a most admirable non- 

 conductor. It is made from blast-furnace slag, and is in the 

 form of a spongy or cotton-like fibrous elastic substance, and 

 is so liojht that one ton will cover five hundred and sixtv 

 square feet to a depth of two and a half inches. One of its 

 advantacjes as a non-conductino; coverimx for steam-boilers, 

 heated pipes, etc., besides its absolute indestructibleness, is 

 that it is very porous, and allows the ready passage of moist- 

 ure, so as to show at once the existence and position of any 

 leak. In application it is wn-apped around the article, bound 

 with wire, and covered with canvas. 



The same substance under the name of " mineral w' ool " 

 has been in use in the United States for similar purposes. 

 18 A, Jan. 7, 1876, 422. 



LIGNOSE, A NEW EXPLOSIVE. 



According to the Indiistrie-Zeitiing^ the new explosive, lig- 

 nose, apparently woody fibre prepared with nitro-glycerine, 

 invented by Triitzschler-Falkenstein, is a very light powder, 

 which in a loose condition burns very slowly. The cartridges 

 made of it are larger than those of ordinary blasting-powder 

 of the same power. As it does not withstand moisture, it 

 can not replace dynamite. It lias been employed in a Dum- 



U 



