MECHANICS AND USEFUL ARTS. 125 



with detonating composition. The material being rotten was es- 

 pecially unfavorable lor the exertion of explosive force, for the 

 force had, so to speak, nothing to act against. But wh-it could 

 be dono was done. The hugi; bed was shattered, and particl.s 

 thiW in all directions. Tiie mortar, although it altered its posi- 

 tion, refused, however, to fall, being held, to some extent, by a 

 thick wrought-iron screw-bolt. The next experiment was made 

 upon this bolt. A one-lb. disc of compressed gun-cotton was tied 

 to the belt and exploded. The explosion was then wholly un- 

 co'nfined. Nevertheless the bolt was broken in two places, a re- 

 sult which exceeded the most sanguine anticipations. Still the 

 huge mortar remained in its position. A third operation had, there- 

 fore, to be made. This time two one-lb. charges were disposed 

 under the left trunnion, and a one-lb. charge was so placed as 

 to give the mortar a kick behind. The explosion of the charges 

 completed the work. The monster mortar slowly and gracefully 

 bowed forward and fell to the ground. The gun-cotton had thor- 

 oughly done its work, at a cost of lis. 6d. — Scientific Review. 



PICRATES. THEIR USE AS GUN AND BLASTING POWDERS. 



In 1867, Designolle, of Paris, made powder for firearms and 

 for blasting purposes by means of picrates. Both kinds consist 

 of a mixture of picrate and nitrate of potassa ; the only difference 

 being that the former contains in addition an admixture of char- 

 coal. Their manufacture, as may be inferred from the accident 

 which recently took j^lace in Paris, appears to be carried on to a 

 considerable extent, and the well-known chemist, Payen, in a re- 

 port to the SociiU d'Encouragement^ ascribes to them. several ad- 

 vantages over the ordinary powder. He points out that various 

 kinds of powder may be manufactured by means of them, the 

 relative effects of which may be varied between the limits 1 -.10, 

 namely, that, on one hand, a powder may be made, which 

 will possess 10 times the effect of common gunpowder of equal 

 weight ; while, on the other hand, it is just as easy to prepare an 

 explosive of the same projectile force, but of a less bursting ten- 

 dency compared with ordinary powder. It is said that between 

 these limits all desirable kinds can be made. If so, the long- 

 sought-fSr problem is solved ; that is, an explosive can be pre- 

 pared in a charge of a certain weight, which will impart a defi- 

 nite velocity to a projectile from a firearm of stated dimen- 

 sions. 



Other advantages of the picric-acid compound are that its pro- 

 jectile force can be increased without enhancing its blasting 

 force, or changing its manner of manufacture ; the velocity of 

 combustion may be regulated at will ; and its ignition is not at- 

 tended with the generation of disagreeable gases, as they consist 

 simply of steam. 



The manufacture of the powder from picrates proceeds as fol- 

 lows : The various ingredients are powdered in a stamping 

 mill for at least 3 or at most G hours, under addition of 6 to 14 



11* 



