36(5 



ME. J. E. PETAVEL ON THE PRESSUEE OF EXPLOSIONS. 

 Spherical Explosion Chamber. 



The first explosion chamber is a nearly perfect sphere, 4 inches in diameter (see 

 fig. 5). The measurements made in a plane passing through the axis of rotation 



Fig. 5. Spherical enclosure. 



The recording gauge screws in at A, the firing plug at B, and two valves at C and D respectively. The 

 spigots, which are turned on the forging at either end (A and 13), fit into a cast-iron stand, to which 

 the enclosure is firmly bolted. 



when in the lathe (i.e.., in the plane in which any variation from the spherical shape 

 would be a maximum) showed that the greatest divergence from the mean diameter 

 did not exceed one hundredth of an inch. 



The cavity was cut out of a solid block of rolled steel through an opening only 

 1|- inches diameter, a clever piece of engineering, for which I am indebted to 

 Messrs. LEXNOX and Co. Exceptional care was also taken to give the inner walls a 

 smooth polished surface. 



The internal volume of the cavity was redetermined by weighing the mercury 

 required to fill it. From these determinations the diameter of the sphere is 10'20 

 centims. The volume is, therefore, 556 cub. centims. and the internal surface 327 

 sq. centims. 



The minimum thickness of the walls is 2|- inches, and the apparatus would doubtless 

 withstand a pressure of 2000 atmospheres. As, however, the experiments had to be 

 carried out in an ordinary laboratory, under conditions which would have rendered 



