Experiments with Explosives 243 



A 100 pounds projectile could acquire a velocity of 3400 feet 

 per second, but a 40 pounds one a velocity of 4930 feet, and 

 that could be considerably increased by enlarging the 

 chamber and increasing the gravimetric density of the 

 charge. The solid products of combustion of brown prismatic 

 powder (one of the above six) favoured deposit in the tube, 

 for it became fluid at the temperature of the explosion. A 

 dirty gun made a sensible difference in the velocity, amount- 

 ing to a loss of 9-5 per cent, of energy. Cordite and ballistite 

 produced no deposit. In the experiments three guns had 

 been used of 50, 75, and 100 calibre (ratio of length to 

 diameter) that of 75 calibre, fired with brown prismatic 

 powder, gave, when clean, the same velocity as that of 

 100 calibre, when foul. He indicated how the velocities 

 were measured, and said that higher could be obtained, but 

 they were not practically useful, because of the high resistance 

 of the air. He also mentioned that when nitroglycerine is 

 mixed with diatom-earth, or any inert substance, detonation 

 takes place as if it were not so mixed, but when gun-cotton 

 is dissolved in nitroglycerine, as in the manufacture of 

 cordite, this will not detonate. The difference of action 

 between gun-cotton and cordite is shown by filling a cast-iron 

 shell with each. When exploded by a fulminate,, the one is 

 broken to pieces, the other reduced to powder. 



Oct. 26th, 4i6th meeting. Dr. Giinther described the 

 habits of a small ant (Occophylla sp. ?) found on the west 

 coast of Africa. Colonies of it form nests, double the size of 

 a man's fist, in young shoots of the coffee plant. When a 

 nest is complete, the ants capture a small spider Gastracantha 

 curvispina to cover it with a web, and construct for this a 

 separate cell, opening into the interior of the nest, where 

 they keep it a prisoner and feed it, to repair or renew the 

 external web. Eight or nine of the spiders have been 

 examined, and all prove to be males. 



Mr. Galton said that early in the year he had made 

 experiments to ascertain whether he could work sums in 

 arithmetic by other faculties than sight or hearing, on one 

 or other of which some calculators depend. He taught 



