CARBON—LITTLE 239 
the Latin adamare, to love, may account for the frequency with 
which diamonds are offered at the shrine of Venus. In Sanskrit the 
diamond is vajra, the thunderbolt, a designation not without appro- 
priate significance, for diamonds of small size are often found in 
meteorites. 
Whereas graphite is a good conductor, the diamond has about the 
same electrical resistance as glass. Its refractive index, upon which, 
with proper cutting, its brilliancy depends, is far higher than that 
of glass, and the diamond is transparent to X rays, whereas paste is 
opaque. Some diamonds, at least, are luminous in a dark room after 
exposure to sunlight, and Sir William Crookes has shown that the 
diamond may acquire and retain indefinitely the property of radio- 
activity. A diamond which he embedded for some months in radium 
bromide became olive green and so highly radioactive that it was 
luminous in the dark after nine years. The same distinguished 
chemist ascertained that after exposure in a vacuum tube to a high- 
tension electrical discharge diamonds phosphoresce in various colors. 
Most South African diamonds shine with bluish light, while those 
from other localities emit bright blue, apricot, red, orange, or yellow- 
ish green. 
Owing to the anomalous fact that the boiling point of carbon at 
atmospheric pressure is below its melting point, carbon volatilizes at 
about 3,600° C. without melting. Sir William Crookes has, there- 
fore, calculated that under a pressure of only 17 atmospheres carbon 
would liquefy at a temperature of 4,130° C. and on cooling crystal- 
lize out as diamond. The process is not patented and is commended 
to any who may be contemplating a diamond wedding. 
Many curious associations and beliefs have grown up around the 
diamond. In the Middle Ages it was thought to afford protection 
from plague and pestilence; to warn its wearer of the presence of 
poison by turning dark; and by some subtle homeopathy to be an 
antidote for poisons, though in itself a deadly one. It insured vic- 
tory to its possessor, banished ghosts and dispelled the devil; brought 
friends and riches, and deferred old age. Though diamonds are 
expensive, one seldom gets so much for his money, and, in view of 
these accruing benefits, it is difficult to understand why it is fashion- 
able in Siam to wear your diamonds on Fridays only. 
Diamonds occur in nature in the so-called “ blue clay ” of volcanic 
pipes and are believed to have been formed by the slow crystalliza- 
tion of carbon from iron or molten rock through the combined action 
of high temperature and great pressure. The theory finds support 
in the results obtained by Moissan, who produced diamonds, though 
very small ones, by raising molten iron to very high temperature in 
the electric furnace, introducing carbon within the molten mass, and 
