12 Messrs. W. Macnab and E. Ristori. [May 10, 



These trials were carried out in a field, the bomb being lowered 

 into a hole in the ground before firing. 



Various difficulties were encountered, and in one experiment con- 

 siderable damage was done by the heated gases effecting their escape 

 at the moment of explosion, and "washing away" part of the thread 

 of one of the screw plugs. 



With a density of loading of A = O'l, i.e., with a charge of 24' 76 

 grams, the average of the pressures measured was 6'3 tons per square 

 inch ; with density A = 0'2 the pressui'e rose to 15 tons, and with 

 A = 0'3 the pressure inci'eased to 25 tons. These results are very 

 similar to those published by Sir A. Noble, F.R.S. 



With the small bomb were ascertained the amount of heat gene- 

 rated by the explosion, the volume and composition of the permanent 

 gases resulting, and the quantity of aqueous vapour produced. 



As most of the explosives contained no mineral matter beyond a 

 trifling percentage of " ash," it has been possible to analyse them in 

 this way, the products of explosion when calculated from the analysis 

 and volume of permanent gas and aqueous vapour agreeing closely 

 with the weight of matter in the bomb before firing. 



A few of the explosives left a carbonaceous or mineral residue ; 

 but these will be specially noticed further 011 in connexion with the 

 tables of the results. 



The heat evolved was measured by placing the bomb containing 

 the charge of explosive in the calorimeter containing 2500 grams of 

 water, and it was arranged that the temperature of the air, the water 

 jacket, and the calorimeter closely approximated each other. The 

 stirrer was set in motion, and the thermometer in the calorimeter 

 was read with a kathetometer. Observations of the temperatures 

 were made every minute for the five minutes preceding the firing of 

 the charge, and continued at intervals of a minute until the maximum 

 was reached, and for five minutes longer. The correction for loss of 

 heat due to radiation of heat during the experiments amounted in 

 general to about O'Ol of a degree. The increase in temperature varied 

 from about 1 to 2^ C. according to the charge and explosive 

 used. 



The gas generated by the explosion was passed through weighed 

 drying tubes connected with the valve on the lid of the vessel, and 

 then collected and measured in a calibrated glass cylinder over 

 mercury. The reading of the barometer and thermometer was noted, 

 and the volume reduced to C. and 760 mm. 



The water was determined by immersing the bomb in a vessel 

 containing boiling water. A three-way glass stop-cock intervened 

 between the valve of the bomb and the drying tubes, and the other 

 end of the drying apparatus was connected with a water vacuum 

 pump. 



