230 



Messrs. W. Macnab and E. Eistori. 



deflecti-on when the thmnest wii^e was used should be about the maxi- 

 mum that the photographic plate could record. 



The explosive used for this series of experiments was Ardeer 

 ballistite, composed of 70 per cent, gun-cotton and 30 per cent, nitro- 

 glycerine, and was in the form of thin square flakes. In each case 

 three experiments were made, and the results are shown in Table III. 



Table III. 



Charge, 4 grammes Ardeer Ballistite, 70 per cent. Gim-cotton, 

 30 per cent. Xitro-giycerine. 



Xo. of couple. 



Deflection in mm. 



Mean. 



Maximum. 



1 



85, 



81 -5, 



83 



•5 



83 



85 



2 



102, 



90-5, 



98 



'5 



97 



102 



3 



109, 



115-5, 







112 -5 



115-5 



4 



131, 



128-5, 



138 



'5 



132 -5 



138-5 



5 



1-19, 



149, 



147 





148 



149 



6 



152-5, 



158 -5, 



151 





154 



158 -5 



7 



161, 



170, 



166 





165 -5 



170 i 



8 



185-5,* 



192 







189 



192 



* After the first experiment, tlie -wire was partially fused, but not broken. 



It M-ill be seen that the results are fairly imiform, the average 

 variation from the maximum to mean being only between 2 and 2|- per 

 €ent. 



In the case of couple Xo. 8, which is only 0-015 inch in diameter, we 

 four^ that after the first experiment it was partially fused but not 

 broken, thus showing that we had reached the practical limit of fineness 

 of wire for this particular explosive. 



The character of the increase of the deflection in inverse proportion 

 to the diameter of the couple is clearly shown in Diagram 3, where two 

 similar ciu-ves are shown for two diff'erent explosives. 



The curve A shows the results given in Table III, and the curve 

 B the results of a similar series of experiments made vriih gun-cotton 

 fired with couples 2, 5, 8, 9, and 10. 



In the case of giui-cotton, the temperatm-e being so much lower, as 

 clearly shown in the diagram, we have been able to use thinner couples, 

 and there was no fusion up to Xo. 10, which is 0*01 inch diameter, but 

 a thinner couple (0-005 inch) was fused. The ciuves have been drawn 

 as nearly as possible following the actual measurements, which are 

 indicated by dots surrounded by circles ; as it will be seen, the ciu-ves 

 are very regular, and it is particularly noticeable that the curves of the 

 two explosives are very similar in character. 



In order to get comparative data for several explosives, we made 



