it
is remarkable I have never seen a complete crystal. All appear
shattered, as if on being liberated from the intense pressure under
which they were formed they burst asunder. I have singular evidence of
this phenomenon. A fine piece of artificial diamond, carefully mounted
by me on a microscopic slide, exploded during the night and covered
the slide with fragments. Moissan's crystals of artificial diamond
sometimes broke a few weeks after their preparation, and some of the
diamonds which cracked weeks or even months after their preparation
showed fissures covered with minute cubes. This bursting paroxysm is
not unknown at the Kimberley mines.
"
So far, these specimens are all microscopic. The largest artificial
diamond is less than 1 m.m. across. These laboratory diamonds burn in
the air before the blowpipe to carbonic acid. In lustre, crystalline
form, optical properties, density, and hardness, they are identical
with the natural stone.
"
In several cases Moissan separated ten to fifteen microscopic diamonds
from a single ingot. The larger of these are about 0*75 m.m. long ; the
octahedra being 0"2 m.m."
Again, to quote from Sir William Crookes' paper :—
" A New Formation of Diamond.
"
I have long speculated as to the possibility of obtaining artificially
such pressures and temperatures as would fulfil the above conditions.
In their researches on the gases from fired gunpowder and cordite, Sir
Frederick Abel and Sir Andrew Noble obtained in closed steel cylinders
pressures as great as 95 tons to the square inch, and temperatures as
high as 4,000° C. According to a paper recently
