1879. 1 on Recent Detonating Agents. fi5 



of J oz. of gun-cotton fitted to a detonating fnzo, the sliell being 

 tlioroiig])ly closed by means of a screw ping, the force developed 

 by the dotoniition of the small charge of gun-cotton is transmitted 

 instantaneously in all directions by the water, and the shell 

 is thus broken up into a number of fragments averaging fourteen 

 times the number produced by bursting a shell of the same size by 

 means of the full amount of jiowder which it will contain (13 oz.). 

 Employing 1 oz. of powder, in place of ^ oz. of gun-cotton, in the 

 shell filled with water, the comparatively very gradual ex])losion 

 of the powder charge is rendered evident by tlie result; the shell 

 being broken up into less than twenty fragments by the shock 

 produced by the first ignition of the charge, transmitted by the 

 water. In tliis case the shell is broken up by the minimum amount 

 of force necessary for the purpose, before the explosive force of the 

 powder charge is properly developed. Extensive comparative exjDeri- 

 ments carried on not long since by the Royal Artillery, at Oke- 

 hampton, demonstrated that this simple expedient of filling common 

 shells with water and attaching a small charge of gun-cotton with 

 its detonator to the fuze usually employed, allowed of their appli- 

 cation as efficient substitutes for the comparatively complicated and 

 costly shrapnel and segment shells. 



Another illustration of the sharpness of action developed by 

 detonation as compared with explosion, consequent upon the almost 

 instantaneous character of the metamorphosis which the explosive 

 agent undergoes in the case of detonation, is afforded by a method 

 which the lecturer applied some years since for comparing the violence 

 of action of charges of gun-cotton and of dynamite arranged in 

 different ways. The charges (5 lb.) to be detonated were freely 

 suspended over the centres of plates of very soft steel of the best 

 quality, which rested upon the flat face of a massive block, or anvil, 

 of iron, having a large central circular cavity. The distance between 

 the upper surface of the plate and the charge suspended over it, was 

 4 feet. The sharp blow delivered upon the plate by the air 

 suddenly projected against it by the force of the detonation when the 

 charge was fired, forced the metal down into the cavity of the anvil, 

 producing cup-shaped indentations, the dimensions of which afforded 

 means of comparing the violence of the detonation. A much larger 

 charge of powder exploded in actual contact with the plate, would 

 produce no alteration of form in the metal, and the same negative 

 result would be furnished by the explosion over the plate of a heap of 

 loose gun-cott(m of the same or greater weight than the charges 

 detonated. The above method of experiment was devised, in the first 

 instance by Mr. Abel, in July 1875, for comparing the quality of some 

 specimens of Llandore steel proposed to be used by the Admiralty 

 for ship-building purposes, with samples of malleable iron, and it has 

 since been employed by Mr. Adamson in carrying out a very useful 

 series of experiments, recently communicated to the Iron and Steel 

 Institute. 



Vol. IX. (No. 70.) f 



