L. MECHANICS AND ENGINEERING. 469 



only about 1300 feet, and sound only 1090 feet, per second, 

 we can partially realize this extraordinary velocity. Only 

 the speed of the planets in their orbits, and the rapidity of 

 light and of radiant heat, can be compared with it. Another 

 remarkable feature is that, by means of fulminating powder, 

 wet gun-cotton may be exploded as readily as dry. Wet gun- 

 cotton has hitherto been considered absolutely non-explosive, 

 and, indeed, is so as far as regards flame : thrown upon a fire 

 it acts like a wet blanket. But to the fulminating powder 

 the cotton, though soaking wet, responds instantaneously. 

 A quantity of it inclosed in a common fishing-net, and pro- 

 vided with a dry primer and a fulminate fuse, will explode 

 under water as violently as if confined within a water-tight 

 steel case. Here opens a new field for the makers of subma- 

 rine torpedoes. Some other new applications of gun-cotton 

 have been suggested. If several mines are to be exploded 

 simultaneously, they can be connected by lines of gun-cotton 

 cakes, and the velocity already mentioned made useful. If 

 palisades are to be destroyed, disks of gun-cotton exploded 

 against them will do the work effectually. And if a large 

 tree is to be cut down, a necklace of such disks hung around 

 the trunk will, when detonated, act as thoroughly and as 

 neatly as an axe. 12 A^October 23, 1873. 



PREVENTION OF BOILER INCRUSTATION. ^ 



The process of Dr. De Haen, consisting in the treatment of 

 the feed water with the proper amount of baric chloride and 

 milk of lime, as determined by quantitative analysis, seems to 

 grow in favor for locomotive and stationary engines, and is 

 to be employed for the 310 boilers of Krupp's steel foundry 

 at Essen. 6 C, March 5, 1874, 94. 



DANGER-NOTICE TO LOCOMOTIVE ENGINEERS. 



According to General Morin, a method has been in success- 

 ful operation for a year on the line of the Northern Company 

 of France for informing the driver of a train whether the way 

 is open or not; According to this arrangement, the signal- 

 man, when he turns the disk, sends an electric current, in the 

 direction of the coming train, to a bar placed between the 

 rails ; and when the engine reaches the spot, a metal brush, 

 placed between the wheels, sweeps the cross-bar, the current 



