338 Sir Andrew Noble [March 23, 



I mentioned to you some time ago the time in which a charge 

 would be consumed in the chamber of a gun — if a charge of 500 lbs. 

 of these slabs were effectively detonated, this charge would be con- 

 verted into gas in less than the 20,000th part of a second. 



No such result would follow were I to try a similar experiment 

 with a slab of compressed gunpowder of the same dimensions. I do 

 not say the experience would be pleasant, but there would be nothing 

 of the instantaneous violent action which marks the decomposition of 

 the guncotton. 



To give you an idea of the extraordinary violence which accom- 

 panies detonation, I have fired, for the purpose of this lecture, with 

 fulminate of mercury, a charge of lyddite in a cast-iron shell, and 

 those who are sufficiently near, can see for themselves the result. By 

 far the greater part of the cast-iron shell, weighing about 10 lbs., is 

 reduced to dust, some of which is so fine that I assumed it to be de- 

 posited carbon until I had tested it with a magnet. I may add that the 

 indentation of the steel vessel by pieces of the iron which were not 

 reduced to powder would appear to indicate velocities of not less 

 than 1200 foot-seconds, and this velocity must have been communi- 

 cated to the fragments in a space of less than two inches. 



For the sake of comparison I place beside it a cast-iron shell 

 burst by gunpowder. You will observe the extraordinary difference. 

 I also have on the table two small steel shells exploded, one by 

 a perfectly detonated the other by a partially detonated charge. I 

 may remark that in the accounts of correspondents from the seat of 

 war, frequent mention is made of the green smoke of lyddite. This 

 appearance is probably due to imperfect detonation — to a mixture 

 in fact of the yellow picric with the black smoke. I do not say 

 however that imperfect detonation is necessarily an evil. 



To another experiment I draw your attention. 



For certain purposes I caused to be detonated, in the chamber of a 

 12-pounder, a steel shell charged with lyddite. The detonation was 

 not perfect, but the base of the shell was projected with great violence 

 against the breech screw. You may judge of how great that violence 

 was when I tell you that the base of the shell took a complete im- 

 pression of the recess for the primer, developing great heat in so 

 doing ; but, what was still more remarkable, the central portion of the 

 base also sheared, passing into the central hole through which the 

 striker passes. This piece of shell is upon the table, and open to 

 your inspection. 



One other instance, to illustrate the difference between combustion 

 and detonation, I trouble you with. Desiring to ascertain the difference, 

 if any, in the products of explosion between combustion and deto- 

 nation, I fired a charge of lyddite in such a manner that detonation 

 did not follow. The lyddite merely deflagrated. But a similar 

 charge differently fired shortly afterwards detonated with such 

 extreme violence as to destroy the vessel in which it was exploded. 

 The manner in which the vessel failed I now show you (Fig. IV.) ; 



