1895.] Measurement of Pressures by the Crusher- Gauge. 407 



cylinders were readily placed in position on the iron plate (held hori- 

 zontal by wedges until cylinders and weights were in position) by 

 means of a movable crane. 



The firiog of the cordite charge was effected by means of a wire- 

 bridge heated to redness by an electric current ; on the centre of the 

 wire-bridge a small piece of the cordite was firmly hung. One end 

 of the wire-bridge was soldered to the end of a steel pin forming part 

 of the stopper, the other end was soldered to the end of a steel wire 

 of -^ in. diameter cemented by a suitable resinous cement in a hole of 

 -^ in. diameter passing through the length of the stopper. By 

 reducing the area of the insulated wire to this small amount, the 

 cement held the wire gas-tight against the highest pressure (16 tons 

 per sq^ in.) employed. In the 14-ton and 16-ton experiments, the 

 stopper was cooled by a little ice placed on its upper surface, to pre- 

 vent softening of the cement. 



The area of the mouth of the hole in the stopper was measured by 

 means of a microscope with a cross-wire, the microscope moving 

 horizontally on a graduated scale and carrying a vernier. The pres- 

 sure of the weights on the steel ball and stopper slightly bevels the 

 mouth of the latter ; at the commencement of a series of experiments, 

 weights to about the maximum amount to be used were placed on the 

 steel ball, and four diameters of the inner and lower circle of the 

 bevelled contact-ring were then measured with the microscope- 

 vernier. The area was re-measured in the course of several of the 

 series, and found to be unchanged. 



One hundred and twenty-six experiments in all were made ; a few 

 of these were lost by the weight required having been under- estimated 

 and the gases blowing out on the first experiment of a series being 

 made. A few of them also were lost by the blowing out of the 

 insulated wire, or by other causes. The remainder form twenty-seven 

 series (a series consisting of at least two experiments : in one of which 

 the gases were kept in, and were blown out in the following one), 

 the results (viz., the mean of the last two experiments) of which are 

 given below. Eight series consisted of two experiments, two of 

 three, six of four, three of five, six of six, one of seven, one of eight. 



The gases were either wholly kept in, or wholly blown out of, the 

 explosion vessel. In the former case there was no report and no 

 damage to the steel ball, which could be used for all the experiments 

 of a series ; in the latter case there was a loud report, and the mouth 

 of the hole in the stopper was slightly injured (the steel being melted 

 and blown away by the gases), and a ring melted in the steel ball. 

 A new steel ball was, of course, used for each series of experiments. 

 For the experiments at the lower pressures of 5 and 6 tons, the hole 

 in the stopper was (after damage by the blown-out gases) enlarged 

 at the top (to a depth of J in.) to 0'35 in., and subsequently to 0'40 in. 



