410 Capt. Noble. Note on the Energy absorbed [Feb. 4, 



For example, the nature of the powder employed may, depending 

 on the deposit or fouling left in the bore, affect appreciably the 

 friction. Again, the friction may be considerably modified by the 

 form and diameter of the ring itself, while a variable amount of 

 energy must be absorbed by the methods employed to give rotation, 

 and by the amount of that rotation. 



In the preliminary experiments three descriptions of powder were 

 employed (1) the powder known as P, or the pebble powder of the 

 English Service ; (2) an amide powder in which the nitrate of 

 potassa of ordinary powder is largely replaced by nitrate of ammonia, 

 and which powder, in addition to other valuable properties, gives rise 

 to a smoke much less dense and much more rapidly dispersed than 

 is the case with pebble and other similar powders ; and (3) a true 

 smokeless powder. The form of smokeless powder employed in this 

 country is best known under the name of cordite, a propelling agent 

 which promises to be of great value, and for which we are indebted 

 to the labours and experiments of Sir F. Abel and Professor Dewar. 

 A somewhat similar explosive is employed abroad under the name 

 of " ballistite," and with this explosive also I have been able to 

 make an interesting series of experiments. These experiments do 

 not, however, come within the scope of the present note. 



The preliminary experiments having shown that a very consider- 

 able amount of friction was, in the case of pebble powder, due to the 

 foaling of the gun, while no such result was observed either in the 

 case of the amide powder or the cordite, it was determined to carry 

 out the subsequent experiments with the amide powder, firing, how- 

 ever, for purposes of corroboration an occasional round with the 

 cordite, of which a small quantity only was available. 



It may be of interest to note the loss of velocity and energy due to 

 the fouling with pebble powder. The charge of powder in a 12-cm. 

 gun being 12 Ibs., and the weight of the shot 45 Ibs., the velocity of 

 the shot, the gun being carefully cleaned and oiled, was, in three 

 trials, respectively, 1877 ft.-secs., 1877 ft.-secs., and 1878 ft.-secs. 

 The two rounds fired immediately afterwards, the bore then being 

 foul, were respectively 1850 and 1868 ft.-secs., 1848 and 1847 ft.-secs., 

 1852 and 1847 ft.-secs., or, taking the means of the whole series, the 

 mean velocity with the gun clean was 1877'3 ft.-secs., with the bore 

 foul 1852 ft.-secs., or, to put the result in another form, the mean 

 energy realised from the pebble powder, the bore being carefully 

 cleaned, and allowance being made for the energy of rotation, was 

 1102 ft.-tons, while the mean energy similarly realised with the 

 bore foul was only 1072 ft.-tons, showing a loss of 30 fb.-tons or of 

 2' 73 per cent, of energy attributable to the extra friction due to the 

 powder deposit in the bore. 



For the purposes of the subsequent experiments, three 12-cm. 



