1894.] Researches on Modern Explosives. 11 



The large one consists of a steel cylinder of great thickness, closed at 

 both ends by conical screw-plugs. One plug is provided with a crusher- 

 gauge of the well-known pattern by which the compression of a small 

 cylinder of copper serves to measure the pressure developed. The 

 other plug is provided with an insulated conical core, by means of 

 which an electric current can be passed for the purpose of firing the 

 charge. A small hole on the side of the cylinder, bushed with 

 iridium- platinum, and closed by a coned screw-plug, serves to control 

 the escape of the gases produced by the explosion. 



The capacity of the chamber was carefully measured, and was 

 found to be 247'6 c.c. 



The small vessel is of the same pattern as used by Berthelot, and 

 was made by Golaz, of Paris. It has given great satisfaction, and is 

 in excellent order, although it has been used for more than two 

 hundred explosions. 



This bomb, which is made of mild steel and is cylindrical in shape, 

 consists essentially of three parts a bowl, a conical lid which is 

 accurately ground into the bowl, and a tightening cap which screws 

 on to the bowl over the lid. 



There is a small hole in the lid provided with a delivery tube, 

 which can be opened and closed by means of a finely-threaded conical 

 plug. There is also an insulated platinum cone inserted from under- 

 neath in the lid, which admits of the charge in the bomb being fired 

 by a platinum wire heated to redness by electricity. 



From the lid depend platinum supports which carry a platinum 

 capsule, in which the explosive is placed and suspended in the middle 

 of the chamber. 



The capacity of this bomb is 488 c.c., and the total weight, includ- 

 ing a small stand, when ready for immersion in the calorimeter, is 

 5633-28 grams. 



The calorimeter is made of thin sheet brass, and a helicoidal 

 stirrer of the same metal (Berthelot's pattern), driven by a small 

 electromotor during the experiment, serves to thoroughly mix the 

 water. 



The calorimeter stood in the centre of an annular water-jacket 

 covered with felt. The quantity of water used in the calorimeter 

 each time was 2,500 grams, and the equivalent in water of the bomb, 

 stirrer, and calorimeter, due allowance having been made for the 

 different specific heats of the different metals, is 623'4 grams. 



The different thermometers employed were specially made by 

 Casella, capable of being read to OO05 of a degree centigrade, and 

 the weights of their stems, bulbs, and mercury were known. 



Various experiments were made in the large vessel, especially for 

 the purpose of determining the pressure of the gases under different 

 densities of charge. 



