K. MECHANICS AND ENGINEERING. 419 



EXPLOSIVE BALLOONS. 



An interesting and amusing philosophical experiment may 

 be made by filling the new-fashioned collodion balloons with 

 a mixture of oxygen and hydrogen gases, and, after closing 

 the mouth of the balloon tightly with a string, allowing it to 

 rise into the atmosphere. A fuse of filter-paper, about an 

 inch long and half an inch broad, is to be previously gummed 

 to the side of the balloon, near the mouth, and allowed to dry. 

 When ready to ascend, a drop of the so-called Greek fire, or 

 of a solution of phosphorus in disulphide of carbon, is placed 

 on the filter-paper, the thread cut, and the balloon left to it- 

 self. After rising for about half a minute, during which time 

 a considerable ascent is accomplished, the fuse reaches the 

 collodion, and ignites it with a violent explosion of the gases, 

 and the whole completely disappears, leaving no trace behind. 

 1 i?, April 17, 251, and 6 A, April 11, 773. 



LITHOFEACTEUE FOE BURSTING GUNS. 



An explosive substance a modification of nitroglycerine 

 known as lithofracteur, has been highly recommended for 

 blasting. We learn that it has been put to a special use by 

 the German army in destroying the iron guns in the Paris 

 forts. For this purpose, about two pounds of the lithofrac- 

 teur mass, of a pasty consistency, are inserted in the muzzle, 

 and a layer of clay an inch or two thick smeared over it. 

 Through this, and into the mass of the explosive, is thrust a 

 detonating fuse, and after the explosion the end of the gun 

 is found to be either broken off or cracked so as to unfit it 

 for further use. 3 A, March 3, 159. 



PEETUISET POWDEE. 



A new kind of powder, invented by Mr. Pertuiset, has re- 

 cently excited much attention in consequence of its enor- 

 mously explosive power when used to fill projectiles. In one 

 instance a target was prepared by fastening two plates, one 

 of four and a half inches, and the other of four and three 

 fourths inches in thickness, to a backing of ten inches of 

 wood, followed by an iron skin of one and a half inches, and 

 with twelve inches of oak behind this. A gun of eight inches 

 calibre was loaded, first, with a solid projectile, and fired at 



