July 28, 19 10] 



NATURE 



109 



northern Bushmen into two groups — that of the 

 Kaukau of southern Damaraland and that of the 

 Ngami, which would include the click-using peoples 

 as far north as the Kwando River. Between the 

 two groups there is very considerable linguistic differ- 

 ence, though there exist equally undeniable affinities. 

 In Herr Seiner's photographs, however, only two 

 examples of so-called Bushmen are recognisable as 

 such, the remainder (though their language was 

 "Bush"! are obviously true negroes, and must be the 

 result of hybrids ancient and modern with the true 

 negro stock, as exemplified by the recent Bantu in- 

 vaders (Bechuana and Zambezian) and the Berg- 

 Damara. Seiner classifies the Zambezians as 

 "Bantu," and the Bechuana as a class apart. There 

 is no justification for this distinction. The Bechuana 

 tribes are just as much " Bantu " in languages as the 

 Zamt>i?'zians, though some of them have obviously 

 absorbed a good deal of Bushman blood during the 

 last twelve or fifteen hundred years. 



The descriptions and beautiful pictures of the Kili- 

 manjaro glaciers (in parts ii. and iii. of Band xxii.) 

 are of the highest interest ; so also are the equally 

 careful, illustrated reports on the " volcanelli " (if one 

 may coin a word to describe the lesser craters which 

 break out on the mass of a huge volcano) of the 

 Cameroons. This article, by Dr. Otto Mann, de- 

 scribes the renewed activities of the Cameroons 

 volcanic mass in igog. H. H. Johnston. 



CORDITE. 



THE recent discussion in Parliament on our sup- 

 plies of cordite and our productive capacity for 

 this type of smokeless powder has naturallv directed 

 public attention to these important questions. The 

 production of a smokeless powder was ever the dream 

 of the military strategist, and with the discovery of 

 gun-cotton the conclusion was hastily arrived at that 

 the ideal propellant was found, only to be rudely 

 dissipated bv numerous serious disasters. Gun-cotton 

 for many years resisted all attempts to render its com- 

 bustion sufficiently under control for it to be adopted 

 as a propellant, yet to-day it is the basis of the smoke- 

 less powders of all nations. Its early failures were 

 entirely due to the retention in the nitrated cotton of 

 the physical characters of the parent cotton, for even 

 after reduction to an extremely fine state of division 

 during the process of manufacture, the fibrous nature 

 of the cotton persisted. Success has only been at. 

 tained by the destruction of this fibre, and the smoke- 

 less powders of all nations may be classed either as 

 simple gelatinised gun-cottons in which soluble nitro- 

 celluloses have been gelatinised by treatment with an 

 ether-alcohol mixture, or as nitrocellulose-nitroglycerine 

 colloids, in which the nitrocellulose employed may be 

 of the soluble variety, as in ballistite, or the insoluble 

 (true gun-cotton), as in the case of cordite. 



The introduction of blasting gelatin bv Nobel (1875), 

 consisting of some go per cent, nitroglycerine with 

 10 per cent, of soluble nitrated cotton in a gelatinised 

 form, was the first step towards the production of 

 powders of the cordite type. The high percentage of 

 nitroglycerine rendered blasting gelatin unsuitable for 

 use in guns, but by incorporating the two consti- 

 tuents in equal quantities, Nobel gave to the world 

 the first successful smokeless powder of this class, 

 ballistite. Cordite was the outcome of the work of a 

 committee presided over by the late Sir Frederick 

 Abel, and was patented a year later than ballistite, in 

 i88q. The essential difference between ballistite and 

 cordite is that whilst the former contains soluble nitro- 

 celluloses, cordite contains the insoluble or tri-nitro- 

 cellulose. This change in the character of the nitro- 

 NO. 2126, VOL. 84] 



cellulose employed entailed the introduction of acetone 

 in the manufacture of cordite. Soluble nitrocotton 

 and nitroglycerine can be thoroughly incorporated 

 under proper conditions in the presence of water with- 

 out the aid of any solvent, but the ingredients of 

 cordite can only become perfectly incorporated in the 

 presence of a mutual solvent. It is essential that the 

 solvent shall be sufficiently volatile to permit of its 

 removal at reasonably low temperatures from the 

 finished powder, and acetone, vihich boils at 56° C, 

 fulfils all the conditions best. 



It is important to note that nitroglycerine is the only 

 explosive containing an excess of oxygen, all nitro- 

 celluloses being theoretically deficient in this element to 

 give complete combustion of carbon to carbon dioxide 

 and hydrogen to water. There are therefore admir- 

 able theoretical grounds for the incorporation of these 

 two explosives with each other. The total change in 

 physical characters of both nitroglycerine and nitro- 

 cellulose brought about entirely alters the character 

 of their explosion ; singly, both constituents are be- 

 yond control once combustion is started; gelatinised 

 together, combustion is regularly progressive through- 

 out the mass, an essential condition for a propellant. 



The earlier form of cordite consisted of nitro- 

 glycerine, 68 per cent. ; nitrocellulose, 37 per cent. ; 

 vaseline, 5 per cent. It was soon found that serious 

 erosion took place in the guns, and Sir Andrew Noble 

 showed this to be due to the rapid motion of the 

 gaseous products at very high temperature. Since the 

 temperature is a function of the nitroglycerine content, 

 combustion to carbon dioxide taking place to greater 

 extent with its accompanying higher calorific intensity, 

 it followed that reduction of the nitroglycerine would 

 lower the temperature of the products and lessen the 

 erosion. This led to the introduction of modified 

 (M.D.) cordite of the following composition : — Nitro- 

 glycerine, 30 per cent. ; nitrocellulose, 65 per cent. ; 

 vaseline, 5 per cent. — practically a reversal of the 

 former proportions of the chief ingredients. The in- 

 troduction of the vaseline was inade to overcome 

 metallic fouling in the gun, arising from surfaces of 

 metal in practically a clean condition rubbing against 

 each other as the projectile moved outward. The 

 vaseline decomposition products provided just the 

 slight lubrication needed. It has performed another 

 important office, little thought of on its introduction, 

 in acting as a "stabiliser" in the cordite. 



In the manufacture of cordite, the gun-cotton 

 employed is thoroughly dried at a temperature of 

 40° C, and is then mixed by hand with the proper 

 proportion of nitroglycerine, the mixture being finally 

 passed through a sieve. The "paste" obtained is 

 transferred to an incorporating machine of an exactly 

 similar type to that employed in a machine bakery, 

 except that temperature control is arranged for, and 

 thereworked into a thorough dough with the requisite 

 quantity of acetone. The first kneading occupies 

 about three and a half hours ; then the vaseline is 

 added and a further kneading for a similar period 

 takes place. "Cordite dough," in which every trace 

 of the fibrous character of the gun-cotton has dis- 

 appeared, results, and this dough is then shaped into 

 the finished threads, cords, or rods by pressure 

 through suitable dies. As the thinner makes pass 

 from the press they are wound on drums, thicker 

 qualities being cut into suitable lengths as they pass 

 out on an endless band. The acetone remaining must 

 now be removed bv drving in suitable rooms at a 

 temperature of 1 10° F. The removal of solvent from 

 the larger sizes of all smokeless powders offers con- 

 siderable difficulty owing to their horny nature ; the 

 odour of acetone is readily detected in freshly ground 

 cordite after long storage. 



