Exposed to the intense heat of the voltaic arc

the diamond becomes converted into graphite, Besides its value as a gem it is of 'great use in the arts and manufactures. Diamond dust is used for cutand polishing other gems. riginally diamonds were preserved in their natural form, but in 1456 Louis de Berguin_ or Bruges discovered the art of polishing them on rotating disks with diamond dust. These circular disks are at the present time of soft steel covered with diamond dust and ojl, and made to revolve at 3,000 revolutions a minute. This gives the diamonds the artistic smooth surfaces and sharply defined edges. The proce is slow and tedious, and requires great skill to produce fine results. Until a few years ago Amsterdam was the great diamond-cutting center of the world, but the finest cutting is now done in the United States, and in a great measure by machinery. The finest brilliant in the world today is the “ Jubilee ” diamond, shown at the Paris Exposition of 1900; this was a brilliant of 239 carats of wonderful brilliancy and -purity, and was found at the Jagers fon tein mine in South Africa. Diamonds of from 1 to 22 carats each have been found in 24 localities in the United States, mapped by Kunz for the United States Geological Survey. Authors and composers of Eastern tales long wrote of diamonds as being found in India only, and chiefly in the mines of Golconda —a misnomer, as Golconda was the market not the mine; and diamonds from many mines were sold there. But since the year 1728 these stones have been found in great abundance in Brazil. In 1829 a vein of diamonds was discovered in the Ural Mountains; and in 1867, in the S. of Africa, John O’Reilly, a trader and hunter, reached the junction of two rivers, and stopped for the night at the house of a farmer named Van Niekerk.