6a 



NATURE 



IMay 15, 1879 



■was well illustrated; the base of the lead block 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. 



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 ex- 

 plosive force, even with the use of a comparatively 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 compara- 

 tively great sensitiveness or of their property as solids, of re- 

 ducing the very yielding character of the substance, 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 

 efTected in the consistency of the material, wliich, though still 

 plastic, offers decidedly greater resistance to a blow than the 

 original gummy substance. The particles 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 adhesiveness 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 composition - on the contrary, its 

 superiority in this respect to compressed gun-cotton becomes mere 

 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 blasting gelatine of small proportions of certain substances 

 rich in carbon and hydrogen, which are soluble in nitroglycerine, 

 such as benzol and nitro-benzol, increases to a remarkable extent 

 the non-sensitiveness to detonation of the original material ; and 

 this observation has led to experiments being conducted by 

 engineer officers in Austria, with a view of endeavouring to con- 

 vert the blasting gelatine into a material which should compete, as 

 regards some special advantages in point of safety, with wet gun- 

 cotton in its application to military and naval purposes, and 

 especially as regards non-liability to detonation or explosion by 

 the impact of rifle bullets. If boxes containing dry compressed 

 gun-cotton are fired into from small arms even at a short range, 

 the gun cotton is generally inflamed, but has never been known 

 to explode. It is scarcely necessary to state that wet gun-cotton, 

 containing even as little as 15 per cent, of water, is never 

 inflamed under these conditions. On the other hand, dynamite 

 is invariably detonated when struck by a bullet on passing 

 through the side of the box, and blasting "gelatine, though so 

 much less sensitive than dynamite, behaves in the same way in 

 its ordinary as well as in the frozen condition. The Austrian 

 experiments indicated that the gelatine when intimately mixed 

 with only i per cent, of camphor, generally.though not invariably, 

 escaped explosion by the impact of a bullet, but that when the 

 proportion of camphor amounted to 4 per cent, the material was 

 neither exploded nor inflamed, though, in the frozen state, it 

 was still liable to occasional explosion. These results were con- 

 sidered indicative of a degree of safety in regard to service 

 exigencies, approaching that of wet compressed gun-cotton. 

 The camphoretted gelatine still labours, however, under the 

 disadvantage of being readily inflammable and of burning 

 fiercely, and consequently of giving rise, like dynamite and dry 

 gun-cotton, to violent explosion, or detonation, if burned in con- 



siderable bulk. Moreover, the camphoretted blasting gelatine 

 is so difficult of detonation by the means ordinarily applied that 

 a large initiative charge of a specially violent detonating mixture 

 is prescribed by the Austrian experimenters as being indispens- 

 able to its proper detonation. 



The action of camphor and of other substances rich in carbon 

 and hydrogen in reducing greatly the sensitiveness to detonation 

 of the preparation of soluble gun-cotton and nitro-glycerine is 

 not to be traced to any physical modification of that material 

 produced by the addition of such substances, and no satisfactory 

 theory can at present be advanced to account for it on chemiod 

 grounds. 



The camphoretted gelatine, like Nobel's original gelatine itself, 

 may be kept immersed in water for a considerable time without 

 any important change ; the surface of the mass thus immersed 

 becomes white and opaque, apparently in consequence of some 

 small absorption of water, but no nitro-glycerine is separated, 

 and on re-exposure to the air the material gradually assumes once 

 more its original aspect. It has consequently been proposed to 

 render the storage of blasting gelatine comparatively safe by 

 keeping it immersed in water till required for use, but the test of 

 time is still needed to establish the unalterableness of the material 

 under this condition. 



There can be little question that this interesting nitro-glycerine 

 preparation, either in its most simple form, or modified in variotjs 

 ways, by the addition of other ingredients, promises, by virtue 

 of its great peculiarities as a detonating agent, to present means 

 for importantly extending the application of nitro-glycerine to 

 industrial purposes ; and it is not improbable that, through its 

 agency, this most violent of all explosive agents at present pro- 

 ducible upon a large scale may also come to acquire special value 

 for important war-purposes. 



It has been pointed out that the complete solidification, by 

 freezing, of plastic preparations containing nitro-glycerine, such 

 as dynamite and the blasting gelatine has the effect of facilitating 

 the transmission of detonation tlu'oughout the mass under certain 

 conditions of their applications, ;>., when they are either freely 

 exposed to air or not very closely or rigidly confined. But while, 

 under circumstances favourable to the detonation of these sub- 

 stances, when in the frozen state, their full explosive force is 

 thus much more readily applied than when they are in their 

 normal (thawed) condition, the frozen substances are less sensi- 

 tive to detonation by a blow or an initiative detonation. On the 

 other hand, if subjected to the rapid application of great heat (as 

 for example by the burning of portions of a mass of the explosive 

 substance itself), a detonation is much more readily brought 

 about with the frozen material than if it be in its normal con- 

 dition. Thus a package containing 50 lb. of cartridges of plastic 

 dynamite, when surrounded by fire, burned away without any 

 indication of explosive action ; on submitting lo lb. of frozen 

 dynamite to the same treatment, that quantity also burned with- 

 out explosion, though at one time the combustion was so fierce 

 as to indicate an approach to explosive action ; but when the 

 experiment was repeated on the same occasion with 15 lb. of 

 frozen dynamite a very violent detonation took place after the 

 material had been burning for a short time. 



The following is offered as the most probable explanation of 

 this result. When a mass of dynamite, as in these cartridges, is 

 exposed to sufficient cold to cause the nitro-glycerine to freeze, it 

 does not become uniformly hardened throughout, partly because 

 of slight variations in the proportion of nitroglycerine in different 

 portions of the mixture composing the cartridge, and partly 

 because unless the exposure to cold be very prolonged the external 

 portions of the cartridges will be frozen harder or more thoroughly 

 than the interior. It may thus arise that portions of only par- 

 tially frozen or still unfrozen dynamite may be more or less com- 

 pletely inclosed in hard crusts, or strong envelopes, of perfectly 

 frozen and comparatively very cold dynamite. On exposiure of 

 such cartridges to a fierce heat very rapidly applied, as would 

 result from the burning of a considerable quantity of the material, 

 some portion of one or other of the cartridges would be likely to 

 be much more readily raised to the igniting or exploding point 

 than the remaining more perfectly frozen part in which it is 

 partly or completely imbedded. If the ignition of this portion 

 be brought about (which it will be with a rapidity proportionate 

 to the intensity of heat to which the cartridge is exposed), the 

 envelope of hard frozen dynamite by which it is still more or 

 less completely surrounded and strongly confined, will operate 

 like the metal envelope of a detonator, in developing the ihitial 

 pressure essential for the sudden raising of the more readily in- 



