removed all signs of eruptive activity. The principal minerals which are associated with diamond in the blue ground are magnetite, ilmenite, chromic pyrope, which is put on the market as a gem under the misnomer ‘Cape-ruby,’ ferriferous enstatite, which also is sometimes cut, olivine more or less decomposed, zircon, kyanite, and mica. The evidence produced by an examination of the blue ground and the walls of the pipes proves that the pipes cannot have been volcanoes such as Vesuvius. There is no indication whatever of the action of any excessive temperature, while, on the other hand, there is every sign of the operation of enormous pressure; the diamonds often contain liquid drops of carbonic acid. Crookes puts forward the plausible theory that steam has been the primary agency in propelling the diamond and its associates up into the channel through which it has carved its way to freedom, and holds that molten iron has been the solvent for carbon which has crystallized out as diamond under the enormous pressures obtaining in remote depths of the earth’s crust. It is pertinent to note that, by dissolving carbon in molten iron, the eminent chemist, Moissan, was enabled to manufacture tiny diamond crystals. Water trickling down from above would be immediately converted into steam at very high pressure on coming into contact with the molten iron, and, in its efforts to escape, the steam would drive the iron and its precious contents, together with the adjacent rocks, upwards to the surface. The ferriferous nature of the blue ground and the yellow tinge so common to the diamonds lend confirmation to this theory. The process by which the carbon was extracted from shales or other carboniferous rocks and dissolved in iron still awaits elucidation. Diamonds were found in New South Wales as long ago as 1851 on Turon River and at Reedy Creek, near Bathurst, about ninety miles (145 km.) from Sydney, but the find was of little commercial importance. A more extensive deposit came to light in 1867 farther north at Mudgee. In 1872 diamonds were discovered in the extreme north of the State, at Bingara near the Queensland border. Another discovery was made in 1884 at Tingha, and still more recently in the tin gravels of Inverell in the same region. In their freedom from colour and absence of twinning the New South Wales diamonds resemble the Brazilian stones. The average size is small, running about five to the carat when cut; the largest found weighed nearly 6 carats when cut. They are remarkable for their excessive hardness; they can be cut only with their own dust, ordinary diamond dust making no impression.