444 



NATURE 



[September 4, 1890 



shell thereby entailed, pla!?e it at a disadvantage, especially since 

 some other very violent explosive agents have come to be applied 

 with comparative safety in shells. 



Between four and five years ago intelligence first reached us 

 of marvellously destructive effects produced by shells charged 

 with an explosive agent which the French Government was 

 ela borating. The reported results surpassed any previously re- 

 cord ed in regard to violently destructive effects and great velocity 

 of projection of the fragments of exploded shells, and it was 

 asserted that the employment of this new material, Melinite, 

 was unattended by the usual dangers incident to this particular 

 application of violent explosive agents, an assertion scarcely 

 consistent with accounts which soon reached us of several 

 terrible calamities due to the accidental explosion of shells 

 loaded with Melinite. 



Although the secret of the precise nature of Melinite has been 

 extremely well preserved, it transpired ere long that extensive 

 purchases were made in England, by or for the French authorities, 

 of one of the many coal-tar derivatives which for some years past 

 has been extensively manufactured for tinctorial purposes, but 

 which, although not itself classed among explosive bodies until 

 quite lately, had long before been known to furnish, with some 

 metals, more or less highly explosive combinations, some of 

 which have been applied to the production of preparations sug- 

 gested as substitutes for gunpowder. 



The product of destructive distillation of coal from which, by 

 oxidation, this material is now manufactured, is the important 

 and universally-known antiseptic and disinfectant, carbolic acid, 

 or phenol. Originally designated carbazotic acid, the substance 

 now known as picric acid was first obtained in small quantities 

 as a chemical curiosity by the oxidation of silk, aloes, &c., and 

 of the well-known blue dye indigo, which thus yielded another 

 dye of a brilliant yellow colour. To the many who may regard 

 this interesting phenol-derivative as a material concerning the 

 stability and other properties of which we have little knowledge 

 it will be interesting to learn that it has been known to chemists 

 for more than a century. It was first manufactured in England 

 for tinctorial purposes by the oxidation of a yellow resin 

 {Xanthorrhaa hastilis), known as Botany Bay gum. Its pro- 

 duction from carbolic acid was developed in Manchester in 1862, 

 and its application as a dye gradually extended, until, in 1886, 

 nearly 100 tons were produced in England and Wales. 



Although picric acid compounds were long since experimented 

 with as explosive agents, it was not until a very serious accident 

 occurred, in 1887, at some works near Manchester where the 

 dye had been for some time manufactured, that public attention 

 was directed in England to the powerfully explosive nature of 

 this substance itself. The Fi-ench authorities appear, however, 

 to have been at that time already engaged upon its application 

 as an explosive for shells. It is now produced in very large 

 quantities at several works in Great Britain, and it has been 

 extensively exported during the last four years, evidently for 

 other than the usual commercial purposes. Large supplies of 

 phenol, or carbolic acid, have, at the same time, been purchased 

 in England for France, and lately for Germany, doubtless for 

 the manufacture of picric acid, very extensive works having been 

 established for its production in both those countries. It has 

 been made the subject of experiment by our military authorities, 

 and its position has been well established as a thoroughly stable 

 explosive agent, easily manufactured, comparatively safe to deal 

 with, and very destructive when the conditions essential for its 

 detonation are fulfilled. 



The precise nature of Melinite appears to be still only known 

 to the French authorities : it is asserted to be a mixture of picric 

 acid with some material imparting to it greater power ; but 

 accounts of accidents which have occurred even quite recently 

 in the handling of shells charged with that material appear to 

 show that, in point of safety or stability, it is decidedly inferior 

 to simple picric acid. Reliable as the latter is in this respect, 

 its employment is, however, not unattended with the difficulties 

 and risks which have to be encountered in the use, in shells, of 

 other especially violent explosives. Future experience in actual 

 warfare can alone determine decisively the relative value of 

 violent explosive agents, like picric acid or wet gun-cotton, and 

 of the comparatively slow explosive, gunpowder, for use in 

 shells ; it is certain, however, that the latter still presents dis- 

 tinct advantages in some directions, and that there is no present 

 prospect of its being more than partially superseded as an 

 explosive for shells. 



With regard to submarine mines and locomotive torpedoes, 



NO. 1088. VOL. 42] 



such as those marvels of ingenuity and constructive skill, the 

 Whitehead and Brennan torpedoes, the important progress 

 recently made in the practical development of explosive agents 

 has not resulted in the provision of a material which equals wet 

 compressed gun-cotton in combining with great destructive 

 power the all-important essential of safety to those who have 

 to deal with these formidable weapons, and to man the small 

 vessels which have to perform the very hazardous service of 

 attacking ships of war at short distances by means of locomotive 

 torpedoes. 



Although the subject of the development of explosive force 

 for purposes of war has of late received from workers in applied 

 science, from seekers of patentable inventions, and even from 

 the public generally, a somewhat predominating share of atten- 

 tion, considering that we congratulate ourselves upon the enjoy- 

 ment of a period of profound peace, yet the production of new 

 explosive agents for mining and quarrying purposes, which 

 present or lay claim to points of superiority over the well- 

 established blasting-agents, has been by no means at a standstill. 

 For many years the main object sought to be achieved in this 

 direction was to surpass, in power or adaptability to particular 

 classes of work, the well-known preparations of nitro-glycerine 

 and gun-cotton, which, during the past twenty years, have been 

 formidable competitors and, in many directions, absolutely 

 successful rivals, of black powder. It is both interesting and 

 satisfactory to note, however, that this object has of late, and 

 especially since the publication of the results of labours of 

 English and foreign Commissions on the causes of mioe-acci- 

 dents, been prominently associated with endeavours to solve the 

 important problems of combining, in an explosive agent, efficiency 

 in point of power with comparative non-sensitiveness to explo- 

 sion by friction or percussion, and of securing its effective opera- 

 tion with little or no accompaniment of projected flame. Safety- 

 dynamites, flameless explosives, water-cartridges, and other 

 classes of materials and devices connected with the getting of 

 coal, the quarrying of rock, or the blasting of minerals, have 

 claimed the attention of those who guide the miner's work ; in 

 some of these directions the practical results obtained have been 

 beyond question important, and, indeed, conclusive as regards 

 the great diminution of risks to which men need be exposed in 

 those coal-mines where the ordinary use of explosives, although 

 not altogether inadmissible, may at times be attended with 

 danger. It is to be feared that those results are still far from 

 receiving the amount of application which might reasonably be 

 hoped for ; but, at any rate, there are, among the extensive 

 mining districts where the employment of explosives in connec- 

 tion with the getting of coal cannot be dispensed with, several 

 of importance where the use of gunpowder has almost entirely 

 given place to the adoption of blasting-agents or methods of 

 blasting, the employment of which is either not, or only very 

 exceptionally, attended by the projection of flame or incandescent 

 matter into the air where the shot is fired. 



The mining public is especially indebted to German workers 

 for much of the success which has been obtained in this direction, 

 and also to the eminent French authorities, Mallard and Le 

 Chatelier, for their thorough theoretical and practical investiga- 

 tions bearing upon the prevention of accidental ignition of fire- 

 damp during blasting operations. Having arrived at the conclusion 

 that fire-damp- and air-mixtures are not ignited by the firing of 

 explosive preparations which develop by their detonation tem- 

 peratures lower than 2220° C., they found that ammonium- 

 nitrate, although in itself susceptible of detonation, does not 

 develop a higher temperature than 1130° C., while the tempera- 

 ture of detonation of nitro-glycerine and gun-cotton are, respec- 

 tively, 3170° and 2636°. The admixture of that salt with nitro- 

 glycerine or gun-cotton in sufficient proportion to reduce the 

 temperature of detonation to within safe limits allows, therefore, 

 of the employment of those explosive agents in the presence of 

 fire-damp mixtures without risk of accident, and this fact has 

 led to the effective use of such mixtures as safe blasting-agents 

 in coal. 



Those who have been content to labour long and arduously 

 with the objects steadily in view of advancing our knowledge 

 of the causes of mine-accidents and of developing resources 

 and measures for removing or combating those causes, can 

 cherish the conviction that recent legislation in connection with 

 coal-mines, based upon the results of those labours, has been 

 already productive of decided benefits to the miner, even al- 

 though it has fallen short of what might reasonably have been 



