460 Sir Andreiv Nolle [Jan. 18, 



The conduct of the experiment is as follows : All connections 

 being made, the chronometer is coupled up, the pen carriage beating 

 seconds, but no mark yet being made, as the pen is held up from the 

 recording paper by the detent. 



The drum is started, and when it has reached the desired speed, as 

 shown by the tachometer, the button is pressed and the circuit "is 

 completed at the beat of the next second. The current simultaneously 

 releases the pen and fires the charge. Between one and two seconds 

 after firing, the speed lever is raised, and the speed of the motor 

 reduced. The chronometer continues to beat seconds, thus giving 

 the relation between time and pressure until the experiment is con- 

 cluded. 



Having now described the principal apparatus employed, I proceed 

 to give you some of the results obtained ; but, before doing so, I 

 draw your attention to the samples, not only of the six explosives of 

 which I am giving you details, but some other interesting samples 

 showing, among other things, the variety of forms under which high 

 explosives have been introduced in different countries. I am afraid 

 you will have to wait till the conclusion of the lecture to examine 

 closely the samples, but I draw your attention to the finish and 

 accuracy of dimension of the Norwegian Ballistite, which I have not 

 seen elsewhere equalled. 



It is desirable to give you an idea of the difference of pressures 

 at different densities of some of the explosives shown in the tables, 

 and upon this diagram I have placed curves giving the relation of 

 pressure to density of six of the modern explosives, and for purposes 

 of comparison I have also given the same relation for Amide powder 

 and the old gunpowder. 



Taking first the density of '4, and I need hardly point out that, 

 so far as modern explosives are concerned, the pressures at that 

 density are far above what is permissible in guns ; but at that density 

 Mark I. Cordite gives 41 tons per square inch (6241) atmospheres) ; 

 Italian, and 167 Norwegian (about 39 tons per square inch) ; M.D. 

 and Norwegian, 165 — 88'?) tons; Nitrocellulose, :-')4 tons (5182 

 atmospheres); Amide, 16 '5 tons per square inch (2515 atmo- 

 spheres), and Gunpowder, 7*8 tons per square inch (1181) atmo- 

 spheres). 



If we take the density which gives approximately the pressure 

 permissible in guns — say density '20 — the comparative pressures are 

 as follow : — 



Cordite, a little over 20 tons per square inch (3048 atmo- 

 spheres) ; Italian Ballistite and M.D., a little under 19 tons per 

 square inch (2896 atmospheres) ; the two Norwegian and Nitro- 

 cellulose, between 16*5 and 17 "5 tons (2515 and 2667 atmospheres). 



I may observe, in passing, that, although the figures I have given 

 represent as nearly as possible the pressures due to the samples with 

 which I have experimented, the pressures would vary somewhat, 



