EXPERIMENTS ON SOLID AND GASEOUS EXPLOSIVES. 359 



At first sight it may appear to be over ambitious on the part of the author to 

 attempt to add to the edifice built up by such able investigators. Closer consideration 

 will, however, show that there is a gap in the structure ready to be filled by the small 

 stone which he has quarried out. 



In the case of solid explosives, thanks to NOBLE'S crusher gauge, the actual 

 maximum pressure attained can be accurately measured. The mechanism of the 

 explosion itself and the rate at which the pressure rises from the moment of ignition 

 need, however, further investigation. 



For gaseous explosives the same criticism holds true, more especially for mixtures 

 which are highly compressed before they are fired. The first case has a bearing on 

 all ballistic problems, the second provides some of the data necessary to the designers 

 of the modern gas engine, and thus both are of considerable practical, as well as 

 scientific importance. 



PART I. METHODS AND APPARATUS. 

 Explosive Pressure Gauges. 



At the time this research was started, some six years ago, there was no instrument 

 by means of which the variation of pressure during the course of such explosions 

 could be satisfactorily recorded. Numerous attempts have been made, but without 

 success, to reduce the moment of inertia of the existing types of recording manometers 

 sufficiently to make them of service for this work. The natural period of oscillation, 

 however, invariably proved to be too slow. In consequence, the curves traced out did 

 not record the rise of pressure in the enclosure, but merely the vibrations set up in 

 the mechanism of the gauge by the sudden shock to which it was subjected. To 

 design a satisfactory instrument it was, therefore, necessary to start ab initio. 

 Before, however, the work could be carried out, some further knowledge of the 

 conditions prevailing during the explosion was necessary, and this more especially in 

 the case of highly compressed gaseous mixtures, the behaviour of which was at the 

 time practically unknown. 



Maximum Pressure Gauge. 



For this work a gauge was employed the construction of which will easily be 

 understood from the drawing given in fig. 1. In principle the apparatus is the same 

 as that used by BUNSEN, and consists of a piston closing an aperture in the explosion 

 chamber, the piston lifting if the pressure of the explosion rises above the load for 

 which it is set. 



To reduce the inertia to a minimum, the weights, used in BUNSEX'S apparatus, are 

 replaced by a gaseous pressure. The moving part consists of a double-headed piston 



