114 ANNUAL OP SCIENTIFIC DISCOVERY. 



as a shell ; and, third, that its form renders it useless for pene- 

 tration under water. 



GREEK FIRE. 



True Greek fire is simply a solid, highly combustible composi- 

 tion, very similar to *' Carcass Composition." What is now com- 

 monly called Greek fire consists of a solution of phosphorus or of 

 sulphur and phosphorus in a very volatile liquid, the bisulphide 

 of carbon, to which is sometimes added a mineral oil with the 

 view of increasing its incendiary powers. When this liquid is 

 thrown on to any surface exposed to the air, the solvent evapor- 

 ates, leaving a film of the phosphorus or sulphide of phosphorus, 

 which will then inflame spontaneously, but will not very readily 

 set fire to wood or combustible materials. The proper mode of 

 extinguishing the flame is to throw upon the burning surface a 

 quantity of wet or damp sand, ashes, sawdust, lime, or other 

 powder, wet sacking or carpeting, — any material, in short, by 

 which the flame can be stifled by exclusion of air. No attempt 

 should be made to remove the covering for some time after the 

 flame has been extinguished ; the place should afterward be 

 thoroughly scoured by a pawerful jet of water. 



ARMSTRONG GUN. 



This was the result of an idea of Sir William Armstrong ; namely, 

 that of enlarging the ordinary rifle to the standard of a field gun, 

 and using elongated projectiles instead of spherical balls. It is 

 made by twisting bars of wrought iron round a steel core, and 

 welding them too:ether while white-hot. Over this tube another 

 cover of twisted bar, but with an opposite turn of the spiral, is put ; 

 another, and sometimes a fourth, follows, till the requisite strength 

 is obtained. The power of the gun, as compared with those 

 formerly in use, may be roundly stated thus : for the same weight 

 of projectile the Armstrong gun is only half the weight, requires 

 only half the charge of powder, and sends the shot or shell 3 

 times as far. 



PEABODT SYSTEM OF BREECH-LOADING FIRE-ARMS. 



The Peabody rifle in its form is compact and graceful, and the 

 symmetry of its lines is nowhere infringed upon by unseemly pro- 

 jections, which, besides being offensive to the eye, are often prej- 

 udicial to the comfort of the soldier on the march, or in the per- 

 formance of its necessary manipulations. 



This symmetry is preserved while performing the operation of 

 loading, as the whole movement of the breech-block is performed 

 within the stock, the end of the trigger-guard falling but little 

 more than an inch, whereas, in most breech-loaders, the guard 

 must describe a curve of 90 degrees, and assume a position at a 



