MECHANICS AXD USEFUL AETS. 97 







either of these substances set fire " promptly to the benzine, by becoming 

 inflamed through contact with water. 



In two experiments, made each time with 300 grammes of benzine, and 

 halt' a gramme of potassium, contained in glass vessels, the breaking of 

 these vessels, as they floated on the water, caused the benzine to spread 

 over a large surface ; the potassium taking fire, produced an immense 

 flame, which was very hot, and continued for about one minute, notwith- 

 standing a strong wind in one case, and a smart shower of rain in the 

 second. 



By request of the Minister of War, M. Xiepce undertook to' examine 

 into liquids susceptible of burning when used in the interior of hollow 

 projectiles. He set himself at work, and obtained the following results : 

 A mixture consisting of three parts of benzine, and one of sulphuret of 

 carbon, bting put into a hand grenade, previously heated to a temperature 

 below that of boiling water, produced a disengagement of vapor, which 

 took fire on contact with a small flame ; and a fine jet of flame was 

 obtained, much less smoky than that of pure benzine, and which con- 

 tinued to burn until the whole was consumed. For heating this hollow 

 projectile, either a moment's immersion in boiling water, or contact with 

 burning coals, may be employed. This mixture of benzine and sulphuret 

 of carbon, of the proportions mentioned, floats on water, and its flame has 

 remarkable burning ._ properties when the sulphuret has some phosphorus 

 in solution ; and it is proposed to use it in setting fire to wood. Oil of 

 naptha and oil of petroleum, highly rectified, are nearly as inflammable as 

 benzine, and burn on water as readily ; but their flames are not so hot. 

 The oil of petroleum, benzine, and sulphuret of carbon, as they are not 

 expensive, it is proposed to use in war, either for burning an enemy's ves- 

 sel, or for defending a place. 



Coupled Cannons, This is another weapon of war, the effects of which 

 may be terrible. Two cannon have the same breech, and diverge at a 

 given angle ; they have a common charge of powder, a single touch-hole 

 and a single cap. In each of these cannons, which are accurately bored 

 and polished, a piston of a cylindrical form is fitted, having the same 

 caliber as the cannon, carefully turned, polished and greased. These two 

 pistons are xmited together by an iron cord or wire, when used with a 

 musket, or an iron chain from a meter to a hundred meters in length, when 

 with cannon. These pistons serve as projectiles ; when fired, they straight- 

 en the chain between them, and flying through the air, they sweep every 

 thing before them. Sillimans Journal, Paris Correspondence. 



THE COURAGE OF SCIENCE. 



Courage in the battle-field is celebrated in history and in song, but little 



is said of the courage exhibited in pursuing scientific investigations, though 



often displaying more real elements of bravery than ever were called into 



action in war. It is said that when Arago and Dulong were employed 



o 



