1900.] on Some Modern Explosives. 341 



reduced by *03, as you see with the samples I hold, and this diagram 

 (Fig. VII.) shows at a glance tlie result. The energies you see are, 

 roughly, practically the same, but if you look at the pressure curve 

 you will observe that I have obtained a curve in which, on the 

 whole, the pressures vary in the contrary direction, that is to say, in 

 this case the pressures increase as the nitro-glycerine diminishes. 



Taking the two series into account, they show that by a proper 

 arrangement of amount of charge and diameter of cord, it would he 

 possible to obtain the same ballistics and approximately the same 

 pressure from any of the samples I have exhibited to you. 



But I have to draw your attention to another point. From the 

 curve showing the quantities of heat you will note that in passing 

 from 10 per cent, nitro-glycerine to 60 per cent., the heat generated 

 has increased by about 60 per cent. But if you examine the curve 

 indicating the corresponding amount of erosion, you will see that while 

 the quantity of heat is only greater by about 60 per cent., the erosion 

 is greater by nearly 500 per cent. 



These experiments entirely confirm the conclusion at which I 

 have previously arrived, viz. that heat is the principal factor in 

 determining the amount of erosion. 



In experimenting with a number of alloys of steel, the greatest 

 resistance was shown by an alloy of steel with a small proportion 

 of tungsten, but the difference between the whole of these alloys 

 amounted only to about 16 per cent. 



The whole of these cordites were, as I have mentioned, subjected 

 to detonation tests. None of them, so far as my experiments went, 

 exhibited any special tendency in this direction. 



I will now endeavour to describe to you a most interesting and 

 important series of experiments which, I regret to say, is still a long 

 way from completion. 



The objects of these experiments were (1) to ascertain the time 

 required for the combustion of charges of cordite in which the cordite 

 w r as of different thicknesses, varying from 0*05 inch to 0-6 of an 

 inch ; (2) the rapidity with which the explosives part with their 

 heat to the vessel in which the charge is confined; and (3) to ascer- 

 tain, if possible, by direct measurement, the temperature of explosion 

 and to determine the relation between the pressure and temperature 

 at pressures approximating to tliose which exist in the bore of a gun, 

 and which are, of course, greatly above any which have yet been 

 determined. 



As regards the first two objects I have named, I have had no 

 serious difficulties to contend with, but as regards the third, I have so 

 far had no satisfactory results, having been unable to use Sir W. 

 Boberts-Austen's beautiful instrument owing to the temperature at the 

 moment of explosion being greatly too high, high enough indeed to 

 melt and volatilise the wires of the thermo junction. 



I am, however, endeavouring to make an arrangement by which 



