858 



THE POPULAR SCIENCE MONTHLY. 



by underground wires, electric discharges 

 which fuse the fine wires of the lightning- 

 guards. These accidents are much less fre- 

 quent and less severe than in the cases 

 where the wires are aerial, 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 conduct- 

 ive soil, the coating, under the influence of 

 storm-clouds, takes a more or less consider- 

 able 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 direc- 

 tions. 



Coal-Dnst and Mine-Explosions. We 



have already given an account of the ex- 

 periments of the Prussian Fire-Damp Com- 

 mission at Neunkirchen, with reference to 

 explosions in coal-mines, and of the conclu- 

 sion of Mr. W. Galloway, from the observa- 

 tion 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 es- 

 tablished 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 impor- 

 tance of the agency of coal-dust, the expres- 

 sion of Ilerr 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 ex- 

 tent, 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 fine- 



ness. Ee believes that the French commis- 

 sion were not accurate or thoroughgoing 

 enough in their experiments. We mention 

 also, as bearing on this subject, and going 

 to confirm Mr. Galloway's viuws, that the 

 Clifton Hall colliery, near Manchester, Eng- 

 land, 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 re- 

 lief ; and a sharpening of the tooth for all 

 of which styles considerable variety in pat- 

 terns exists. As all the Mohammedan isl- 

 anders set much store on having their teeth 

 properly " improved," the tooth-filer is an 

 important personage among them. His out- 

 fit includes a hammer, a bracing-stone or an- 

 vil, chisels, files, and saws. The person to be 

 operated upon prepares his teeth for the pur- 

 pose 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 un- 

 intelligible 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 Mohammed- 

 anism. M. E. T. Hamy has made a study of 



