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Updated: June 13, 2025
The rocks of Ceylon are primitive, consisting of granite, gneiss and quartz. Of these the two latter predominate. Dolomite also exists in large quantities up to an elevation of five thousand feet, but not beyond this height. Plumbago is disseminated throughout the whole of both soil and rocks in Ceylon, and may be seen covering the surface in the drains by the road side, after a recent shower.
It tastes strongly of iron, which flavours almost every spring in the country, yet the most likely places do not show this incrustation. Sometimes it looks like a matrix in which pudding- stone has been imbedded; it may be two or three lines in thickness and it does not colour the inside. At other times it hardly measures the thickness of paper, coating the gneiss slabs like plumbago.
It consists of a series of silk disks saturated with a sizing of plumbago and well dried. The disks are compressed by means of an adjustable screw; and in this manner the resistance of a circuit can be varied over a wide range. In like manner Edison developed a "pressure" or carbon relay, adapted to the transference of signals of variable strength from one circuit to another.
The speaker laughed and told the story. The discoverer had stolen off by night, got an expert to come and examine it, and would tell the result only to one friend, and in a whisper. "'You haven't got much plumbago, the expert had said, 'but you've got dead oodles of silica. You know, Barb, silica's nothing but flint, ha-ha!" Fair smiled.
Victor could have stopped, but the rock on which he had fallen seemed to be covered with plumbago. While frantically clutching and vainly trying to grasp some obstruction that would overcome his momentum, he slid over the edge and dropped into the boiling cauldron below. The accident was begun and finished, as may be said, in the twinkling of an eye.
Edison found that the same property might be applied to regulate the strength of a current in conformity with the vibrations of the voice, and after a great number of experiments produced his 'carbon transmitter. Plumbago in powder, in sticks, or rubbed on fibres and sheets of silk, were tried as the sensitive material, but finally abandoned in favour of a small cake or wafer of compressed lamp-black, obtained from the smoke of burning oil, such as benzolene or rigolene.
Presently she started up, exclaiming that they would be late for breakfast; and they hurried back to the tumble-down house with its pointless porch and unpruned hedge of plumbago and pink geraniums where the Wellands were installed for the winter. Mr.
Lovers of racial traits like to remember that Thoreau's grandfather was an immigrant Frenchman from the island of Jersey, and that his grandmother was Scotch and Quaker. His father made lead pencils and ground plumbago in his own house in Concord. The mother was from New Hampshire. It was a high-minded family. All the four children taught school and were good talkers.
It exists in such quantities, in the gneiss rocks that upon their decomposition it is seen in bright specks like silver throughout. This gneiss rock, when in a peculiar stage of decomposition, has the appearance and consistency of yellow brick, speckled with plumbago.
When any substance was introduced into this arch, it instantly became ignited; platina melted as readily in it as wax in a common candle; quartz, the sapphire, magnesia, lime, all entered into fusion; fragments of diamond and points of charcoal and plumbago seemed to evaporate in it, even when the connection was made in the receiver of an air-pump; but there was no evidence of their having previously undergone fusion.
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