Optical and Physical Effects of High Explosives

By R. W. wood, For. Mem. R.S., Professor of Experimental Physics, Johns Hopkins University

(Received 15 June, 1936)

My interest in the study of the effects produced by high explosives originated in the investigation of " evidence " in a number of murders by bomb, and more especially in connexion with a most unfortunate and unusual accident which resulted in the almost instant death of a young woman who, on opening the door of the house furnace to sec if the fire was burning properly, was struck by a small particle of metal which flew out of the Src and penetrated the breast bone, slitting a large artery and causing death in 2 or 3 minutes from internal haemorrhage. The particle, which was not much larger than a pin-head, was submitted to me for identification, and though its form resembled nothing with which I was familiar, I surmised that it was probably a part of a dynamite-cap or " detonator " used for exploding the dynanutc charges in the mines, which, by some carelessness on the part of a miner, had been delivered intact with the coal.

These detonators are spun from very thin. sheet copper and consist of a tube about 5 mm. in diameter and 40 mm. in length. The head is formed into a shallow cup/as shown in cross-section in. fig. 1, and the tabe is charged wuh mercury fulminate and fired by an electrically heated wire. It seemed probable that the solid pellet of^copper, recovered during the autopsy, had been formed in some way from the concave head of the detonator by the enormous instantaneous pressure developed by the detonation of the fulminate.

I accordingly suspended one about 2 feet above a large earthenware jar holding about five gallons of water, pointing the head downwards. On firing the detonator 'the jar was shattered into a dozen or more pieces by the pressure wave exerted in tlie water by the passage of the small copper fragment (the head of the detonator) entering the water with three limes the velocity of a rifle bullet, just as a milk can filled with water is burst open when the bullet of a high powered rifle is fired through it... .

Proceedings, Royal. Society,(London) 1936