168 Mr. F. A. Abel on the [Feb. 5, 



garded as similar to that which would be presented by a perfectly solid 

 mass. Similarly, if the strong vessel be completely filled with a mixture of 

 water and a solid (e. g. a fine powder or a fibre reduced to a fine state of 

 division), such a mixture should also, at the instant of detonation, 

 behave as a very compact solid with regard to the resistance which it 

 opposes to the detonating charge which it surrounds. If this be so, a 

 mixture of finely divided gun-gottoii with water, if enclosed in a shell, 

 should be in a condition readily susceptible of detonation, because at the 

 instant of explosion of the initiative charge, the particles of gun-cotton 

 must offer great resistance to mechanical motion. Experiment has fully 

 established the correctness of this conclusion, having demonstrated that, 

 while it is indispensable to employ gun-cotton in a highly compressed 

 form, to ensure its detonation under all other conditions, it may, if en- 

 closed in strong vessels, such as shells, be employed with equal efficiency 

 in a finely divided state, provided the spaces between the particles be 

 completely filled with water, the small detonating charge being immersed 

 in the aqueous mixture. 



The results obtained in the several experiments bearing on the trans- 

 mission of detonation led the author to attempt to determine its velocity, 

 or the rate at which it proceeds along a continuous mass, or from one 

 mass of an explosive body to another, under various conditions. For 

 this purpose he availed himself of the electric chronoscope devised by 

 Captain A. Noble, F.R.S., which had furnished satisfactory results in 

 determinations of the rate of motion of projectiles in the bore of a gun, 

 made by the Government Committee on explosive substances. The ex- 

 periments were carried out with compressed gun-cotton in the dry and 

 wet state, with " nitrated " gun-cotton, with nitroglycerine and dynamite, 

 and with small charges of gun-cotton inserted into tubes, with considerable 

 intervening spaces*. The disks of gun-cotton, dry, wet, and nitrated, 

 were arranged either in continuous rows or trains, the disks either 

 touching each other, or a definite and uniform space or interval 

 intervening between each. At the commencement of the row a fine in- 

 sulated wire, forming part of the primary circuit (by the sudden severance 

 of which the electric record of the rate of transmission was obtained on 

 the chronoscope), was tightly stretched across the first disk. Other 

 wires were similarly fixed at uniform distances (of one, two, four, or six 

 feet) from each other. In determining the velocity of transmission of 

 detonation through tubes, wrought iron gas-pipes of O032 metre 

 (1'25 inch) diameter were used, with small perforations at the desired 

 intervals, through which the insulated wires were passed ; the disks of 

 gun-cotton, to which detonation was to be transmitted, were inserted 

 into the tubes so as to be in close contact with these tightly stretched 



* In carrying on these experiments, Mr. Abel received valuable assistance at dif- 

 ferent times from Captain Singer, R.N., Major Maitland, B.A., and Captains W. H. 

 Noble and Jones, R.A. 



