Ma}' I, 1879] 



NATURE 



19 



The additions to the Zoological Society's Gardens during the 

 past week include a Black-handed Spider Monkey (v^/z-fo melan- 

 ochii) from Central America, presented by Mr. D. R. Comyn ; 

 two Prairie Marmots {Cyiiomys ludovicianus) from North Ame- 

 rica, presented by Mr. W. G. Marshall ; a Guilding's Amazon 

 {Ckrysotis guilJtitsi) from St. Vincent, West Indies presented 

 by Mr. G. Dundas, C.M.Z.S. ; a Cuvier's Podargus (Podargus 

 cinieri) from Australia, prcenlcd by Mr. R. S. C. Eaber ; a 

 Lesser Long-eared Bat (Plecctus liirvimanus), British Isles, pre- 

 sented by Mr. J. Ward; a thre -toed Amphiuma (Amphiwna 

 means) from North America, presented by Mr. A. C. Cole ; a 

 Bonnet Monkey (Macactis radiaUis) from India, an Egyptian 

 Cat {Felis chaus) from North Africa, a Common Ass (Asinus 

 vulgaris) from Persia, a Grey-headed Torphyris (Porphyris polio- 

 cephalus) from South Asia, a Puff Adder ( Vipera arutans) from 

 the Cape of Good Hope, deposited. 



RECENT CONTRIBUTIONS TO THE HISTORY 

 OF DETONA TING AGENTS ' 



A MONG the many explosive preparations which have during 

 ■"• the last thirty years been proposed ns sul-stitutes fur gun- 

 powder, on account of greater violence and other special merits 

 claimed for them, not one has yet competed wiih it succes-^fuUy 

 as a propelling agent, nor even as a safe and sufficiently reliable 

 explosive agent for use in shells ; for industrial api^lications and 

 for very important military or naval uses, depeiiJeit upon the 

 destructive effects of explosives, it has had, however, to give 

 place, to a very important extent, and in some instances 

 altogether, to preparations of gun-cotton and nitro-glycerine. 



But there appeared little prospect that either gur.-ooiton or 

 nitro-glycerine, whether used in their most simple c );idition or 

 in the forms of various preparations, would assume positions of 

 practical importance as explosive agents of reliable, and there- 

 fore uniformly efficient, character, until the system of developing 

 their explosive force through the agency of a detonation, instead 

 ef through the simple agency of heat, was elaborated. 



Before the first step in this important advance in the appli- 

 cation of explosive agents was made by Alfred Nobel, about 

 twelve years ago, the very variable behaviour of such substance ■> 

 as gun-cotton and nitro-glycerine, when exposed to the heat 

 necessary for their ignition under comparatively slight n\odifica 

 tions of attendant conditions (e.g. as regards the completeness 

 and strength of confinement or the position of the source of 

 beat with reference to the main mass of the material to be 

 exploded) rendered them uncertain in their action, and at any 

 rate, only applicable under circumstances which confined their 

 usefulness within narrow limits. The employment by Nobel of 

 an initiative detonation, produced by the ignition of small 

 quantities of mercuric fulminate or other powerful detonating 

 substances, strongly confined, for developing the violent explosion, 

 or detonation, of nitro-glycerine, opened a new field for the 

 study of explosive substances, and the first practical fruit was 

 the successful application of plastic preparations of nitro-glycerine 

 and of compact forms of compressed gun-cotton, witli simplicity 

 and certainty, to the production of destructive effects much more 

 considerable than could be accomplished through the agency of 

 much larger amounts of gunpowder, applied under the most 

 fevourable conditions. Whereas very strong confinement has 

 been essential for the complete explosion of these substances, so 

 long as the only known means of bringing about their explosion 

 Consisted simply of the application of fire or sufficient heat, no 

 confinement whatever is needed for the development, with 

 certain' V, of a decidedly more violent explosive action than they 

 are i,-.»ljle of exerting when thus applied, if they are detonated 

 by .-uimitting some portion of the mass to the blow or concus- 

 sion developed by a sharp detonation, such as is produced by 

 tile ignition of a small quantity of strongly confined mercuric 

 fulminate. 



The conditions essential to the development of detonation in 

 masses of nitroglycerine and gun-cotton, or preparations of 

 ftem, and the relations to and behaviour towards each other of 

 these and other explosive bodies, in their character or functions 



^ Weekly Evening Lecture at the Royal Institution, Friday, March 21, 

 rt79. By Professcr Abel, C.B., F.R.S. Revised by the Author. 



as detonating agents, have been made the subject of study by 

 the lecturer during the last ten years, and some of the earlier 

 results published by him in connection with this subject also led 

 to the pursuit of experimental inquiries of analogous character 

 by Champion and Pellet and others. 



Some of the chief results attained by Mr. Abel's experiments 

 may be briefly summarized. 



It was found that the susceptibility to detonation, as distin- 

 guished from explosion, through the agency of an initiative 

 detonation, is not confined to gun-cotton, nitro-glycerine, and 

 preparations containing those substances, but that it is shared, 

 though in very different degrees, by all explosive compounds 

 and i.ixtures. 



It was demonstrated that the detonation of nitro-glycerine and 

 other bodies, through the agency of an initiative detonation, is 

 not ascrihal lie simply to the direct operation of the heat developed 

 by the chemical changes of the charge of detonating material, 

 and that the remarkable property possessed by the sudden explo- 

 si )nof small quantities of certain bodies (the mercuric and silver 

 fulminates) to accomplish the detonation of nitro-glycerine and 

 gun-cotton, is accounted for satisfactorily by the mechanical 

 force thus suddenly brought to bear upon some part of the mass 

 operated upon. Most generally, therefore, the degree of facility 

 with which the detonation of a substance will develop similar 

 change in a neighbouring explosive substance, may be regarded 

 as proportionate to the amount of force developed within the 

 shortest period of time by that detonation, the latter being in 

 fact an ilogous in its operation to that of a blow from a hammer 

 or of the impact of a projectile. 



Thus, explosive substances which are inferior to mercuric 

 fulminate in the suddenness, and the consequent momentary 

 violence of their detonation, cannot be relied upon to effect the 

 detonation of gun-cotton, even when used in comparatively 

 considerable quantities. Percussion cap composition, for 

 example, which is a mixture of fulminate with potassium 

 chlorate, and is therefore much less rapid in its action than 

 the pure fulminate, must be used in comparatively large 

 quantities to accomplish the detonation of gun-cotton. 



The essential difference between an explosion and what we 

 now distinguish as a detonation lies in the comparative sud- 

 denness of the tran^formation of the solid or liquid explosive 

 substance into gas and vapour. 



The gradual nature of the explosion of gunpowder is illustrated, 

 in its extreme, by burning a train of po«der in open air ; the 

 rapidity and consequent violence of the explosion is increased 

 in proportion to the degree of confinement of the exploding 

 charge, or to the resistance opposed to the escape or expansion 

 of the gases generated upon the first ignition of the confined 

 substance. 



In the case of a very much more sensitive and rapidly ex- 

 plosive substance than gunpowder, such as mercuric fulminate, 

 the increase in the rapidity of its transfjrmation, by strong 

 confinement, is so great that the explosion assumes the character 

 of a detonation in regard to suddenness and consequent destruc 

 tive effect. A still more sensitive and rapidly explosive material 

 (such as the silver fulminate and iodide of nitrogen) produces 

 when exploded in open air effects akin to those of detonation ; 

 yet even with these bodies, confinement operates in increasing 

 the rapidity of the explosive to suddenness, and consequently 

 I in devel iping a mire purely detonative action. 



Detonation, developed in some portion of a mass, is trans- 

 mitted with a velocity approaching instantaneousness throughout 

 any quantity, and even if the material is laid out in the open 

 ! air in long trains composed of small masses. The velocity with 

 which detonation travels along trains thirty or forty feet in length, 

 composed of distinct masses of gun-cotton and of dynamite, 

 has been f)und to range from I7,cx30 to 24,000 feet per second. 

 Even when trains of these explosive agents were laid out with 

 intervening spaces of half an inch between the individual 

 masses composing the trains, detonation was still transmitted 

 along the separated masses with great though diminished 

 velocity. 



The suddenness with which detonation takes place has been 

 applied as a very simple means of breaking up shells into small 

 fragments and scattering these with considerable violence, with 

 employment of very small charges of explosive agent. Thus by 

 filling a l6-pr. common shell completely with water and insert- 

 ing; a charge of \ oz. of gun-cotton fitted to a detonating fuze, the 

 shell being thoroughly closed by means of a screw plug, the 

 force developed by the detonation of the small charge of gun- 



