82 Professor Ahel [March 21, 



was all but blown out, the cavity produced was considerably the largest, 

 and the suddenness and violence with which motion was imparted to 

 the water tamping caused the top of the block also to be blown off 

 in the form of a cone. An excellent illustration was obtained, by 

 comparing this result with those furnished by the gelatine in its 

 normal plastic state, of the influence exercised by the physical con- 

 dition of an explosive substance upon the rajndity and completeness 

 with which detonation is transmitted through its mass. 



The difficulties attending the application of blasting gelatine, in 

 some directions in which explosive agents are applied, on account of 

 the uncertainty attending the development of its explosive force, even 

 with the use of a comj)aratively powerful detonator, unless it be very 

 strongly confined, has led to attempts to reduce its non-sensitiveness 

 to detonation by mixing it with materials intended to operate either 

 by virtue of their comparatively great sensitiveness, or of their pro- 

 perty, as solids, of reducing the very yielding character of the sub- 

 stance, or in both ways. 



Some of these attempts have been attended with considerable 

 success. Thus the incorporation of about 10 per cent, of the most 

 explosive form of gun-cotton or trinitrocellulose, in a very finely 

 divided state, with the gelatine, renders it so much more sensitive that 

 it can be detonated with certainty in the open air by means of the 

 strongest detonating cap now used for exploding dynamite. This 

 effect appears to be less due to the comparative sensitiveness of gun- 

 cotton to detonation than to the modification effected in the consistency 

 of the material, which, though still plastic, offers decidedly greater 

 resistance to a blow than the original gummy substance. The par- 

 ticles of hollow fibre of the gun-cotton appear also to have the effect of 

 absorbing small quantities of nitro-glycerine which are less perfectly 

 united with the soluble gun-cotton than the remainder, and which, 

 existing as they do in somewhat variable proportions in the gelatine, 

 have occasionally an objectionable tendency to exudation, if the in- 

 corporation of the ingredients has been less perfect than usual. The 

 substance, when modified as described, has no longer that great adhe- 

 siveness which is exhibited by it in the original state, and which 

 renders it less easy to manipulate. 



Lastly, its explosive force appears to be in no way diminished by 

 this modification of its comj)osition, on the contrary, its superiority in 

 this respect to compressed gun-cotton becomes more manifest, as 

 demonstrated by some of the experiments with lead blocks, while its 

 action partakes of that sharpness peculiar to the detonation of the 

 rigid gun-cotton, as indicated by the fissure of that part of the metal 

 situated beneath the charge. Finely divided cotton fibre has a similar 

 effect to trinitrocellulose in modifying the physical character and 

 increasing the sensitiveness to detonation of the blasting gelatine, but 

 its explosive force is, of course, proportionately reduced with its 

 dilution with an inert substance. 



Nobel has made the interesting observation, that an addition to the 



