340 Sir Andrew Noble [March 23, 



being successively in the proportions of 60, 50, 40, 30, 20 and 

 10 per cent., and with each of these cordites I determined the follow- 

 ing points : 



1. The quantity of permanent gases generated. 



2. The amount of aqueous vapour formed. 



3. The heat generated by the explosion. 



4. The erosive effect of the gases. 



5. The ballistic energy developed in a gun and the correspond- 

 ing maximum pressure. 



6. The capacity of the cordite to resist detonation when fired with 

 a strong charge of fulminate of mercury. 



The results of these experiments were both interesting and in- 

 structive. 



To avoid wearying you with a crowd of figures, I have placed on 

 Fig. VI. the results of the first five series of experiments. 



On the axis of abscissae are placed the percentages of nitro- 

 glycerine, while the ordinates show the quantities of the gases 

 generated, the amount of heat developed, the erosive effect of this 

 explosive, the ballistic energy exhibited in a gun, and the maximum 

 gaseous pressure. 



You will note that with the smallest proportion of nitro-glycerine 

 the volume of permanent gases is a maximum, and that the volume 

 steadily decreases with the increase of nitro-glycerine. On the other 

 hand the heat generated as steadily increases with the nitro-glycerine, 

 and if we take the product of the quantity of heat and the quantity 

 of gas, as an approximate measure of the potential energy of the 

 explosive, the higher proportion of nitro-glycerine has an undoubted 

 advantage ; but in this case, as in the case of every other explosive 

 with which I have experimented, the potential energies differ less 

 than might be expected from the changes in transformation, as the 

 effect of a large quantity of gas is to a great extent compensated by a 

 great reduction in the quantity of heat generated. 



This effect is, of course, easily explained, and was very strikingly 

 exhibited in the much more complicated transformation experienced 

 by gunpowders of different compositions, a long series of which were 

 very fully investigated by Sir F. Abel and myself. 



Looking at this diagram you will have observed that the energy 

 developed in the gun is very much smaller with the smaller propor- 

 tions of nitro-glycerine, but if you will look at the" corresponding 

 maximum-pressure curve you will note that the pressures have de- 

 creased nearly in like proportion. Hence it is probable that the 

 lower effect is mainly due to a slower combustion of the cordite, and 

 it follows that this effect may be, to a great extent, remedied by 

 increasing the rate of combustion by reducing the diameter of the 

 cordite to correspond with the reduction in the quantity of nitro- 

 glycerine. 



To test this point I caused to be manufactured a second series of 

 cordites of the same composition, but with the diameters successively 



