548 APPENDIX. 



At low densities of charge, 0'67 and 0'73, the mean velocities 

 varied from 



3767 m. to 3795 m. 



This reduced velocity is evidently occasioned by the greater 

 discontinuity of the explosive resulting from the diminished 

 density of charge. 



Abel, operating with dry compressed gun-cotton placed in 

 continuous trains in the open, observed velocities of 



5320 m. to 6080 m. 

 with gun-cotton containing 20 per cent, of water 



6090 m. 

 with "nitrated " gun-cotton 



4712 m. and 4865 m. 



With charges of gun-cotton placed in an iron tube and separated 

 by spaces of 1 mm., he found 



1800 m., 

 the transmission being retarded on account of the discontinuity 



IY. "STARCH" POWDER. 



The average velocities observed with this powder, density of 

 charge about 1'2 in a tin tube 4 mm. external diameter, were in 

 two experiments 5222 m. and 5674 m. 



In a tin tube 5'5 mm. external diameter, the velocity was 5816 m. 



In a leaden tube, for density of charge between I'l and 1*2, the 

 average velocity was 5006 m., and for 1'35 density 5512 m. All 

 other things being equal, the velocity increases with the density of 

 charge. The process employed for making these tubes does not 

 permit of the interior diameter being sufficiently guaranteed to 

 authorise definite conclusions being drawn from the difference in 

 velocities observed in tubes of tin and lead. 



Y. NlTROMANNITE. 



Compressed pulverulent nitromannite fired in leaden tubes 4 mm. 

 external diameter, density of charge 1'58 and 1'53, gave average 

 velocities of 6911 m., 7082 m., and 6965 m. At higher density of 

 charge, 1*9, the average velocity was 7705 m. ; and this is the 

 highest average velocity which has been observed. 



VI. NlTROGLYCERIN. 



Liquid nitroglycerin detonates with difficulty in narrow tubes 

 at low temperature, it having been found impossible to detonate it 

 in a leaden tube of less than 3 mm. diameter at 12 to 13. 



In tubes of lead or Britannia metal of 3 mm. to 4 mm. diameter, 

 temperature 14, when placed in the shade, the detonation was only 

 transmitted a short distance ; but when the tubes were placed in 

 the sun, and thereby heated to 18 to 20, the detonation was 

 transmitted the whole length of the tube. 



