24G 



MAJOR .T. H. MANSELL: INVESTIGATION OF 



in these experiments made 500 vibrations a second. The electro-magnet H and cam 

 K are for the purpose of momentarily allowing the stylus on the end of the tuning- 

 fork to trace a record on the drum and so give its speed the spring N pulling the 

 arm (which carries the cam) away from the electro-magnet. 



The use of the apparatus is as follows : The charge having heen placed in the 

 vessel, the copper is placed in position and M is screwed home. The stylus on C is 

 then adjusted on the drum, as is also the stylus on G in the position of release. 

 The circuit of the electro-magnet H is carried by an adjustable joint to C in such a 

 manner that the circuit is broken by the first movement of C as the copper 

 compresses. The circuit being complete, the electro-magnet holds the arm O and 

 lifts the stylus off the drum. When the circuit is broken the arm is revolved by 

 the spring N, and the cam K thus lowers the stylus G on to the drum and then lifts 

 it off again. We thus obtain a record of the speed of the drum at the actual 

 moment of firing. All being ready, the drum D is set in motion by the motor, 

 whose speed can be regulated by a rheostat. The tuning-fork is started in the usual 

 way, and the charge is then fired. 



An example of an actual record is subjoined. These records are measured under a 

 micrometer with a telescopic eye-piece carrying cross wires, the telescope being 

 carried on a compound lathe rest. It measures centimetres to four places of decimals 

 in both directions of movement. 



Characteristics of the Explosive. 



1. If elation of Pressure and Density, The first step in the investigation of the 

 burning of an explosive is to find the relation between the maximum pressure and 

 the density at which the explosive is fired. The explosive I have experimented with 

 is the latest British one, known as modified cordite. The Service abbreviation for 

 this is M.D. cordite, and it will be so called throughout this paper, the original type 

 of cordite being referred to as Mark I. In a closed vessel the maximum pressure is 

 independent of the temperature of the cordite, but temperature has an influence on 

 the time taken by the cordite to develop that pressure. The higher the temperature 



