78 
THE HON. SIR CHARLES ALGERNON PARSONS; EXPERIMENTS ON 
smelted by the heating carbon rod or by the associated hydrocarbons, &c., when such 
were added, and iron globules were formed. In these, diamond was occasionally 
found when cooling was rapid and they were centrally situated in the charge. 
Very Quick Cooling. —-To test the action of very quick cooling a carbon crucible of 
2-inch internal diameter charged with iron, sugar carbon, 2 per cent, silicide of carbon, 
well boiled by resistance heating under atmospheric pressure and 2 per cent, of iron 
sulphide added, was quickly placed on asbestos mill-board resting on a steel table 
frictionally held in the bore of the 4-inch mould, below being placed 2 lbs. of carbon 
dioxide snow, and the plunger quickly brought down by the press, subjecting the 
whole to 6000 atmospheres pressure. When taken out the crucible was intact, the 
contents had divided into a lower portion consisting of a large grained crumbling 
mass of graphite admixed witli granules of very hard iron, in the centre a rounded 
pillar of white iron equally hard. The cooling seemed to have been unusually rapid. 
The experiment was repeated, the crucible being charged with iron, sugar carbon, 
5 per cent, manganese, 5 per cent, cobalt, 2 per cent, silicide of carbon, boiled, and 
2 per cent, iron sulphide added. 
It was also repeaterl with water instead of carbon dioxide snow. The result of all 
these experiments was similar to the first. No diamond was found in any part. 
An experiment which seemed to give practically instantaneous cooling was as 
follows :—A small carbon crucible containing iron, with traces of silicon, aluminium, 
calcium, magnesia and sulphur, was floated on a carbon block on a bath of mercury, 
all contained in a vessel exhausted to 2 mm. absolute. The crucible was heated 
by an arc from an upper carbon, the holder passing through a stuffing box. When 
the crucible was sufficiently hot and the contents carburized, the upper carbon was 
thrust down, submerging the crucible under the mercury; the cooling was almost 
explosive and instantaneous—the finely divided iron and graphite on analysis yielded 
no diamond. 
Extremely rapid cooling does not, therefore, seem to be a direct cause in the 
production of diamond. 
Experiments at Atmospheric Pressure. 
A convenient method of studying the effect of the association of other elements 
with iron on a small scale uncontaminated by the vapours of a furnace lining 
suggested itself, and a series of experiments were made as follows :—A deep iron dish 
was packed tightly with Acheson graphite with a slight dimple in the centre to hold 
the ingot, above, graphite was filled in loosely to a depth of half an inch covering the 
ingot. An arc was struck by a carbon on to the ingot submerged in the loose 
graphite. When the iron was well boiled the surrounding graphite with the ingot 
in it was dug out entire and thrown into a bowl of mercury covered with water. 
The results showed that, using ordinary mild steel, no diamond ever occurred on 
analysis, but that a small percentage of silicon is absolutely essential; small 
