65 



the hull, however, this provision would hardly answer, therefore Mons. 

 Jouvin coats it with composition composed of the following : Turbith 

 mineral (S0 3 3HgO), mixed with Prussian blue (3Fe Cy + 2Fe 2 Cy 3 ), 

 producing by its contact with the " alkaline chlorides" of sea- water one 

 of the most violent poisons known to mineral chemistry, viz., the 

 cyanide of mercury (HyCy) in the shape of chloro-cyanide of mercury 

 and sodium. He therefore first mixes 55 parts of turbith mineral and 

 45 parts Prussian blue, and composes the paint as follows : — Boiled 

 linseed oil, 250 parts ; red lead, 679 parts ; and the aforesaid mixture, 

 100 parts ; but this mixture must not be applied to the bare hull, which 

 on the contrary must first receive a coating of zinc paint of not less 

 than Jo inch in thickness. I believe, of all the various compositions 

 invented for the purpose, this of M. Jouvin to be the best. 



The metal Mr. Whitworth uses in the construction of his ordnance 

 is known as homogeneous iron, very much of the same nature as mild 

 steel. It is chiefly composed of bars of Swedish iron, cut into short 

 lengths, melted in crucibles, and cast into a large cylindrical ingot, 

 which is subsequently forged under a tilt hammer into the required 

 form. The guns are forged solid, bored out in the usual manner, and 

 rifled uniformly throughout their length, without leaving any chamber 

 at the breech end. The pitch in the rifling of a 1 2 pounder is one turn 

 in 60 inches. Mr. Whitworth's favourite projectile is a " fiat-headed" *~ 

 hexagonal bolt. To give an idea of its force, it may be stated, that when 

 it was fired at the "Alfred" target ship at Portsmouth, the gun being 

 laid at 450 yards, the shot passed through 30 feet of water diagonally, 

 and eight inches of oak, piercing the timber three feet below the surface 

 of the water ; when spherical shot, or long projectiles with rounded fronts, 

 are fired in the water, they do not penetrate below the surface, but 

 turn and come back again ; the flat- fronted shot seems the best for 

 traversing iron plates. If the round-fronted form of shot is fired 

 against a thick wrought iron plate, it displaces the particles of the iron 

 plate in a lateral direction, and has to overcome the great lateral resis- 

 tance they offered to its passage. In the case of the flat- fronted shot 

 the resistance is confined to the exact spot on which the flat front of 

 the shot strikes, the resistance then becomes direct, and not lateral ; and 

 if the " momentum" of the shot is sufficient, it displaces the particles of 

 the iron plate, and forms a vacuum in the shape of around punched hole. 

 "With regard to the question of rifling the bores of guns, which seems to 

 be generally assumed as an indispensable theory in these days, there 

 are many opinions. Mr. Adams regards it as simply a contrivance for cor- 

 recting the defects of badly constructed projectiles at a considerable 

 waste of propelling power. If the centre of gravity of a conical shot is 

 not placed at the junction of the major and minor axes, the resultant of 



* This kind of shot is said to have been used with great success by the captain of a 

 whaling ship, to kill seals, many years ago. 



E. I. A. PEOC. VOL. IX. K 



