On the other hand there would appear to be an arrangement between the diamond merchants of London, Paris, and Amsterdam, by which the uniform value for a diamond carat is fixed at ·205 of a gram. This value, which was suggested in 1871, by a syndicate of Parisian jewellers, goldsmiths, and others engaged in the commerce in precious stones, was subsequently (1877) confirmed. But, in spite of all efforts to secure uniformity in the standard by which diamonds are bought and sold, very serious discrepancies in sets of carat weights as turned out by different makers still exist.
It may be imagined that the diamond does not lend itself readily to the art of the gem engraver, still several engraved diamonds exist. Of these two signets are preserved in the Royal collection at Windsor. One representing the Prince of Wales plumes was cut for Charles I. when Prince of Wales, the other and more important specimen is the armorial signet-ring of Queen Henrietta Maria. This had found its way into the last Duke of Brunswick's collection and then became the property of the city of Geneva. The late Dr. Drury Fortnum bought it and presented it to Queen Victoria. It was engraved in January 1629 to the order of Charles I. by one Francis Walwyn, who received the sum of £267 for his work and for the cost of the boart used. There are other engraved diamonds, mostly of the seventeenth century, of European workmanship in various museums and Royal treasuries. But neither from the artistic nor mineral ogical standpoint are they of much importance.
CORUNDUM.
Sapphire, Ruby, and Oriental Amethyst.
Next to the diamond in hardness must be placed the many varieties of the species called corundum. This includes the sapphire, the ruby, the oriental amethyst, the oriental topaz, and a whole