PLUMBAGO, black lead, graphite.
Blyant, . . . DAN. Tshernyi Karandash, Rue.
Potloot , HUT. Lapiz plomo, . . SP. Plombagine ; Potelot, FR. Carburetto de hierro, „ Reisblei pottloth, . GER. Engelsk blyerts, . Sw. Piombaggine,. . . Ir.
Plumbago, a carburet of iron, is used for making leads for pencils and for crucibles. Barrowdale, in Cumberland, was long the only known mine that produced lead of that fine quality requisite for the manufacture of drawing-pencils. The Cumberland mines had been wrought since Queen Elizabeth's time ; pure Cumberland lead costing as much as from 30 to 40 shillings a pound, being found in detached pieces, so that the supply was occasionally irregular, and the search for it labori ous and often fruitless. Inferior descriptions come from Spain. Veins occur in the hills near Nambrapane in Ceylon. These are largely worked. The best kind of plumbago for crucibles is Ceylon, as it resists the action of fire better than any other substance, except asbestos, and the -export has risen from less than 24,000 cwt., valued at £1000, in 1850, to 136,000 cwt., valued at nearly £44,000. Lieut. Evans, 51st Regiment M.N.I., exhibited plumbago of indifferent quality from beds of shale that accompany iron-ore at Malacca. Indifferent plumbago was also exhibited along with iron-ore and slaty shales from Cuddapah. It was found by Captain Boswell, of the 52d Regiment, in the hills of Paparassam, where it occurs in con siderable quantities. Darjiling and Burma are also mentioned as localities from which it has been brought ; it is found to the east of Nat-taik in large quantities on a low range of hills near the village of Nyokestoke. It is not utilized. Finely powdered graphite can, by an extreme degree of pressure, be rendered nearly as compact as the best mineral graphite. The great manufac turers of pencils in England reported the Kamaon and Travancore specimens as quite useless for the manufacture of black lead pencils, observing that they could not use the specimens in the state in which they had been sent without damaging their machinery, at the same time they could not con ceive why purer specimens should not be found in the same locality. General Cullen, Resident
of Travancore, reported that two varieties were found, one in thin laminae, another granular. The granular or fibrous variety he had discovered in two localities, and both of them in laterite, a few feet only below the surface. One locality is about 5 or 6. miles N.E. of Trevandrum, and the other about 12 or 14 miles N.E. ; he brought in from this latter locality, on his visit to it, about 3 cwt. Some small deposits are also found immediately on the "W. of the town of Trevandrurn. Graphite in thin scales or laminae is common nearly through out the laterite tracts of Travancore and Cochin, but more or less abundant in particular places. It is found in some places in laminae of consider able size, particularly in a laterite hill about 25 miles N.E. of Trevandrum at a place called Cavi attencudul, near the foot of the Ghat mountains. It is also found in laminar of good size in the disintegrated gneiss of the ghats on the Tinnevelly side, also common in the kunkur or travertine deposits near Culdacoorchy and Amba-samudrum. The Vizagapatam graphite is probably also found in laterite, of which there was a large deposit at Bimlipatam. Plumbago mixed with boiled oil, and applied to canvas and other cloths, renders it non-combustible. A powdery plumbago has been obtained from Jammu territory. It was discovered by Dr. W. J. Thornton, Civil Assist ant-Surgeon, Gurgaon, in October 1861. It is found in masses of variable sizes, and in general detached, though in some cases the rock ' II round is full of plumbago mixed with finely ivided micaceous partieles.—Cat. E.r., 1862 ; On e Graphite of It by Dr. Boyle ; Letter from e Resident of Travancore, Oth February 1857, ombay Gazette ; M. L. S. Journal; Rolale's MS.; 411. C. C.; 11/. K.T. R. ; Simmonds.