by underground wires, electric discharges which fuse the fine wires of the lightning guards. These accidents are much less frequent and less severe than in the cases where the wires are aërial, and they do not seem to be of such a nature as to interfere with the transmission of dispatches. They correspond always to storms which occur in the country, at some distance from towns where the underground wires are protected by the net of water and gas pipes below which they are placed. If the wire is buried only at a slight depth in a badly conductive soil, the coating, under the influence of storm-clouds, takes a more or less considerable electric charge, even when the internal wire remains in a neutral condition. At the moment when the lightning flashes, this charge is suddenly liberated, at least in part, and escapes into the earth, following the metallic coating in two opposite directions.
Coal-Dust and Mine-Explosions.—We have already given an account of the experiments of the Prussian Fire-Damp Commission at Neunkirchen, with reference to explosions in coal-mines, and of the conclusion of Mr. W. Galloway, from the observation of some of them, that the explosions are chiefly or very largely promoted by coal dust. A French commission has reported upon this subject that they consider it established that "coal-dust in the absence of fire-damp does not constitute an element of danger," although it may play an important part in aggravating the consequences of an explosion. Mr. Galloway is now able to cite, in support of his view of the importance of the agency of coal-dust, the expression of Herr Hilt, in the official preliminary report of the Prussian commission, who, speaking of the dust from Pluto mine, in Westphalia, says that "there can be no doubt that with this kind of dust the flame could be lengthened out to any desired extent, provided the gallery and the layer of dust on its floor were made equally long;" also the statement that "the dust of New Iserlohn behaves in the same way." Mr. Galloway further cites a table of dusts of different degrees of fineness, published in the same report, to show that the explosive property of coal-dust increases with its fineness. He believes that the French commission were not accurate or thoroughgoing enough in their experiments. We mention also, as bearing on this subject, and going to confirm Mr. Galloway's views, that the Clifton Hall colliery, near Manchester, England, where a fatal explosion occurred in June last, was at the time dry and dusty, and very free from fire-damp.
Mutilations of the Teeth.—The practice of filing the teeth is still in vogue among the Mohammedan Malays. The individual may choose, according to his fancy, among three fashions: that of simply rubbing away the front surface of the tooth; that of filing away the sides so as to leave the front of the tooth standing out in a triangular relief; and a sharpening of the tooth—for all of which styles considerable variety in patterns exists. As all the Mohammedan islanders set much store on having their teeth properly "improved," the tooth-filer is an important personage among them. His outfit includes a hammer, a bracing-stone or anvil, chisels, files, and saws. The person to be operated upon prepares his teeth for the purpose by chewing raw rice and turmeric, and, prostrating himself on the ground, lays his head, blindfolded, upon the operating-bench. The operator demonstratively repeats an unintelligible incantation phrase, and, wedging the subject's mouth open, performs his work. The filing done, the teeth are blackened, and the pain is quieted with cocoanut-water in which an iron, inserted red-hot, has been standing for several days. For some time after the operation, the patient must avoid eating things unpleasant to sore teeth. As a recompense, he has come into full credit in society, and may marry. The legendary origin of the custom is a miraculous escape Mohammed is said to have once had from the pursuit of a redoubtable antagonist. After having eluded his pursuer by being overshadowed by a swarm of bees, he was nearly overtaken again, and hid in a dry well. Some of the pursuing party thought he might be in the well, and threw stones into it. He was looking up at the time, and the stones knocked out four of his upper teeth. The fashion of filing down the teeth is, however, probably older than Mohammedanism. M. E. T. Hamy has made a study of
