72 
THE HON. SIR CHARLES ALGERNON PARSONS: EXPERIMENTS ON 
A very light piston made of tool steel was carefully fitted to the barrel of a Duck- 
gun of 0'9-inch bore ; the piston was flat in front, lightened out behind, and fitted 
with a cupped copper gas check ring, the cup facing forward; the total travel of the 
piston was 36 inches. To the muzzle of the gun was fitted a prolongation of the 
barrel, formed out of a massive steel block, the joint being gas-tight. The end of the 
bore in tire block was closed by a screwed-in plug made of tempered tool steel, also 
with a gas-tight collar. A small copper pin projected from the centre of the plug to 
give a record of the limit of travel of the piston. 
The gun was loaded with 2 drachms of black sporting powder, which amount had 
been calculated from some preliminary trials. The barrel in front of the piston was 
filled with acetylene and oxygen, with a small excess of acetylene. It was estimated 
that this mixture would explode when the piston had travelled about lialf-way along 
the bore ; when fired the piston travelled to within -y--inch of the end, as had been 
estimated, giving a total compression ratio of 288 to 1. 
Result. —The surfaces of the end plug, the fore end of the piston, and the circum¬ 
ference of the bore up to f-inch from the end of the plug had been fused to a depth 
of about 0'01-inch and were glass hard, the surface of the copper pin had been 
vaporized and copper sprayed over the surface of the end plug and piston. 
The end plug showed signs of compression, and the bore of the block for 
|-inch from the plug was enlarged by 0'023-inch in diameter, both deformations 
indicating that a pressure of above 15,000 atmospheres had been reached. A 
little brown caiHon was found in the chamber, which was easily destroyed by 
boiling sulphuric acid and nitre with no residue. There was a small crystalline 
residue from the melted layer of the end plug, from which was isolated one 
non-polarizing crystal, probably diamond, but too small to identify with absolute 
certainty. 
Considering the light weight of the piston and the short duration of the exposure 
to heat, also the small diameter and volume of the end clearance space, the observed 
effects would seem to indicate that a very abnormal temperature had been reached, 
many times greater than exists in the chambers of large guns. There was, however, 
no evidence of any melting and re-crystallization of the free carbon present. In the 
Appendix is given a calculation from which it seems that the temperature reached 
was probably above 15,250° C. 
Experiments with High Velocity Bullets. 
As it seemed desirable toffry the effect of still higlier pressures, a rifle, 0'303-inch 
bore, was fitted with a specially strong breech mechanism by Rigby, capable of 
withstanding a charge of cordite 90 per cent, in excess of the service charge. 
The gun (fig. 6) was fixed in a vertical position on the wall of the armoured 
press house, with its muzzle 6 inches from a block of steel, in which a hole 
