536 



REPORT — 189i. 



The first curves represented in the diagram are the time curves. So 

 far as the eye can see, the time curves in all cases pass through the 

 observed points. From the time curves the velocity curves are deduced, 

 and I have given for each velocity curve the observed velocities, so that 

 the accordance of the computed curve with the observed velocities will be 

 seen. The velocity curve being fixed, the pressure curve of necessity 

 follows, and the diagram shows both the accordance of the two rounds 

 fired under the same circumstances, and the slight discordance in the 

 forward part of the curve of the round with the bore clean is very dis- 

 tinctly shown. 



Comparing now the methods of determining the pressures which hare 

 been chiefly used in this country — I mean the chronoscope and the crusher 

 gauge — if the object sought be merely to determine the maximum pressure 

 developed with the powders now generally in use, no instrument can be 

 simpler than the crusher gauge, and, when properly used, its indications 



Fig. G.— Improved Apparatus for Cutting Wire by Moving Shot. 



may be taken as very approximately correct, but it cannot be relied on t& 

 give accurate results when placed in positions where the products of 

 explosion are moving with a high velocity. 



The maximum pressures under the conditions I havg supposed are 

 very approximately confirmed by the chronoscope, as may be seen by 

 comparing the pressures shown on the diagram giving the results as to 

 pressure obtained with certain new explosi-\'es, to which I shall presently 

 advert. As a general rule it may be said that, where the powders are 

 slow in lighting and no wave action exists, the chronoscope pressures are 

 generally somewhat higher than those of the crusher gauge ; but the case 

 is very difierent where the powder is of a highly explosive or quick- 

 burning description. With such powders not only are the crusher-gauge 

 pressures greatly above those of the chronoscope, but the widest difierence 

 frequently exists between the pressures indicated in diflTerent parts of the 



