82 
THE HON. SIR CHARLES ALGERNON PARSONS: EXPERIMENTS ON 
consisted of 95 per cent, carbon monoxide, 1 per cent, hydrogen, 2 per cent, hydro¬ 
carbon, 2 per cent, nitrogen. 
The carbon which formed the crucible and cover contained a large percentage of 
silica, but the carbon monoxide was produced chiefly by the action of sand (of which 
there was a thick layer on the bottom of the container to protect the insulating 
joint from iron spilled from the crucible) on the carbon of the stem of the crucible. 
About one half of the iron had been evaporated, and there remained an ingot about 
the size and shape of a broad bean. It contained rather large graphite crystals and 
was easily broken. The analysis gave the largest residue of diamond in proportion 
to the amount of iron of any of our experiments, the largest crystals being 0‘7 inm. 
in length. 
This experiment was repeated several times with the same result. Tlie time of 
cooling of the crucible, fi-om switching off the current to the temperature of setting, 
was 15 seconds, and probably sufficiently rapid to allow of a skin to be formed 
around the ingot before the centre was solidified, for the configuration of the crucible 
and cover were such as to ensure nearly equal and simultaneous cooling on all sides 
of the ingot. At the time, vacuum was erroneously thought to be the chief 
contributory cause and not the presence of carbon monoxide in large proportion. 
High Vacuum Experiments. 
The molecular pump not having yet been evolved, a powerful pumping system was 
arranged, consisting of three steam-jet exhausters in series, the last ejector of the 
series discharging into a jet condenser witli separate air and water pumps, the former 
assisted by a steam jet. The two steam-jet exhausters nearest to the exhausted 
chamber were fed with highly superlieated steam at 200 lbs. pressure, and the 
suction pipe to the chamber was 4 inches in diameter—the chamber 2 feet 
6 inches diameter—of spherical shape (fig. ll). A vacuum of j- mm. absolute could 
be reached. 
The crucible was placed on a large block of carbon, resting on the base of the 
chamber, and forming the bottom pole. The cover was insulated from the chamber, 
and through an oil-sealed gland passed a 2-inch brass rod, carrying a crown holder, 
with four 2-inch carbons which rested on the Up of the crucible for resistance heating. 
An observation window was placed at the apex of a long iron cone, projecting from 
the side of the cover, which gave a good view of the crucible and its contents. The 
whole of the chamber was submerged in a tank of water, up to the level of the gland 
in the cover. 
Iron and iron alloys were boiled and allowed to cool slowly by radiation, or were 
rapidly quenched by admitting water through a large valve from the tank into the 
vacuum vessel. The iron and carbon vapour from the boilings deposited dust and 
globules on the cover and sides and bottom of the chamber. A very small diamond 
