83 



NATURE 



[May 24, 1900 



cotton and 95*6 per cent, of insoluble; as used, it contained 

 2 '25 per cent, of moisture. 



The service cordite consists of 37 per cent, trinitro-cellu- 

 lose, with a small proportion of soluble gun-cotton, 58 per 

 cent, of nitro-glycerme and 5 per cent, of the hydrocarbon 

 vaseline. 



The ballistite I principally used was composed of 50 per cent, 

 dinitro-cellulose (collodion cotton) and 50 per cent, of nitro- 

 glycerine. The whole of the cellulose was soluble in ether 

 alcohol, and the ballistite was coated with graphite. 



The French B.N. powder consisted of nitro-cellulose partly 

 gelatinised, and mixed with tannin, and with barium and potas- 

 sium nitrates. The transformation experienced by some of these 

 explosives is given in Table I., while the pressures in relation to 

 the gravimetric densities of some of the more important are 

 shown in Fig. i. 



DENSITY OF PRODUCTS OF EXPLOSION 



Fig. I. — Pressures observed in closed vessels w 



Table I. 



explosives. 



The decomposition experienced by these high explosives on 

 being fired is of much greater simplicity than that experienced 

 by the old powders, and is, moreover, not subject to the con- 

 -siderable fluctuations in the ultimate products exhibited by 

 them. 



The products of explosion of gun-cotton, cordite, ballistite, 

 &c., are at the temperature of explosion entirely gaseous, con- 

 sisting of carbonic anhydride, carbonic oxide, hydrogen, nitrogen 

 and aqueous vapour, with generally a small quantity of marsh 

 gas. 



The water collected, after the explosion vessel was opened, 

 always smelt, occasionally very strongly, of ammonia, and an 

 appreciable amount was determined in the water. 



In examining the gaseous products of the explosion of various 

 samples of gunpowder, it was noted that as the pressure under 

 which the explosion took place increased, the quantity of car- 

 bonic anhydride also increased, while that of carbonic oxide 

 decreased. The same peculiarity is exhibited by all the ex- 

 })losives with which I have experimented. I show in Table II. 

 the result of a very complete series of a sample of gun-cotton 

 fired under varying pressures, and it will be noted that the 

 voluines of carbonic oxide and carbonic anhydride are, between 

 the highest and lowest pressures, nearly exactly reversed. 



There are slight changes as regards the 

 other products, but they do not compare 

 in importance with that to which I have 

 referred. 



But before drawing your attention to 

 other points of interest, it is desirable to 

 give you an idea of the advances in bal- 

 listics which have been made both by im- 

 provements in the manufacture of the old 

 powders and by the introduction of the 

 new. 



On Fig. 2 is placed the results as regards 

 velocity of nine explosives, commencing 

 with the R.L.G. powder, which was in 

 use in the latter part of the fifties, and 

 terminating with the cordite of the present 

 day. 



The experiments I am now referring 

 to were made in a gun of 100 calibres 

 in length, and were so arranged that 

 in a single round the velocities couki 

 be measured at i6-points of the bore. 

 The chronoscope with which these velocities were taken has 

 been already described, and I will now only say that it is capable 

 of registering time to the millionth of a second with a probable 

 error of between two and three millionths. One curious fact 

 connected with the mode of registration I may mention. In the 

 early experiments with the old powders, where the velocities did 

 not exceed 1500 or 1600 feet-seconds, the arrangement for 

 causing the projectile to record the time of its passing any par- 

 ticular point was efi"ected by the shot knocking down a small 

 steel knife or trigger which projected slightly into the bore ; but 

 when the much higher velocities, with which I subsequently ex- 

 perimented, were employed, this plan was found to be unsatis- 

 factory, the steel trigger, instead of being immediately knocked 

 down by the shot, frequently preferred instead to cut a groove 

 in the shot, sometimes nearly its whole length, before it acted. 

 Hence another arrangement for cutting the primary wires had to 

 be adopted. 



The diagram I am now showing you is, however, both inter- 

 esting and instructive. The intention, among other points, was 

 to ascertain for various calibres in length in a 6-inch gun the 

 velocities and energies that could be obtained, the maximum 

 pressures, whether mean or wave, not exceeding about 20 tons 

 on the square inch. The horizontal line or axis of abscissae re- 

 presents the travel of the shot in feet, the ordinates or perpen- 

 diculars from this line to the curve represents the velocity at tljat 



NO. 1595, VOL. 62] 



point. 



The lowest curve on the diagram gives, under the conditions 

 I have mentioned, the velocities attainable with the powder 

 which was used when rifled guns were first introduced into the 

 service, and you will note that with this powder the velocity 

 attained with 100 calibres was only 1705 foot- seconds, while with 

 40 calibres it was 1533 foot-seconds. Next on the diagram 

 comes pebble powder with a velocity of 2190 foot-seconds ; next 

 comes brown prismatic with a velocity of 2529 foot-seconds. 



The next powder is one of considerable interest, and one 

 which might have arisen to importance had it not been super- 

 seded by explosives of a very diff'erent nature. It is called 

 Amide powder, and in it ammonium nitrate is substituted for a 

 large portion (about half) of the potassium nitrate, and there is 

 also an absence of sulphur. You will observe the velocity in 

 the 100 calibre gun is very good, 2566 foot-seconds. The pres- 

 sure also was low and free from wave action. It is naturally not 



