1 873.] Metallurgy. 263 



an explosive atmosphere, the transmission of a sound-wave, produced by a 

 slight explosion of gunpowder, is sufficient to determine the communication 

 of flame from the lamp to the surrounding atmosphere. Hitherto it has been 

 generally assumed that the occurrence of a colliery explosion, after firing a 

 shot, is due to actual communication of flame from the gunpowder to the 

 fire-damp; but Mr. Galloway's experiments show that it is much more likely 

 that the explosion is determined by the noise of the shot being propagated 

 through the galleries of the mine to the safety-lamps. An admirable experi- 

 ment to illustrate this point was exhibited by Dr. W. Spottiswoode at a recent 

 lecture at the Royal Institution. A lighted Davy lamp was surrounded by 

 streams of coal-gas issuing from a number of jets round the base of the lamp. 

 One extremity of a long tin tube, open at both ends, was placed in connection 

 with the lamp, while a pistol was fired at the other end, a caoutchouc 

 diaphragm being interposed in the tube to prevent the transmission of a direct 

 current of air. The sound-wave, generated by the report, travelled along the 

 tube, and, as soon as it reached the flame, caused ignition of the surrounding 

 atmosphere — the lamp being immediately enveloped in flames. 



An improved self-extinguishing safety-lamp, which appears to combine 

 security, simplicity, and strength, has been patented by Mr. Yates, of Duke 

 Street, Westminster. The lower part of the lamp, containing the reservoir of 

 oil, is furnished with a locking-bolt, which bears against some ratchet teeth 

 fixed to the base of the upper portion, or cage of wire-gauze. While the lamp 

 is being screwed into its cage the bolt runs readily over these teeth, but when 

 the two parts are screwed together it is impossible to unscrew them until this 

 bolt has been withdrawn. This is effected by turning a milled head attached 

 to the unlocking screw at the base of the lamp, but the very act of turning 

 this screw causes the wick to be so depressed in its socket that before the 

 lamp can be opened the flame is effectually extinguished. It therefore becomes 

 impossible for the miner to tamper with his lamp without immediate extinction 

 of the light. Nor is there any inducement to open the lamp for lack of light, 

 for unusual brilliancy is obtained by a silver-plated concave reflector fixed 

 behind the light, and a strong well-annealed glass lens secured in a metal 

 frame in front. It is further claimed for the Yates lamp that, though giving a 

 brilliant light, it consumes much less oil than is usually burnt in the ordinary 

 Davy lamp. 



A description of the remarkable deposits of Fossiliferous Iron Ore in 

 Southern Pennsylvania, by Prof. B. Silliman, has been published in the 

 " Journal of the Iron and Steel Institute." These deposits occur in a group 

 of Silurian rocks, known locally as the " Surgent Shales " — the equivalent of 

 our Wenlock beds. Three zones of ore are found on three distinct horizons in 

 these shales — the Levant ore, the Twin beds of fossil ore, and the Haematites 

 at the top of the series. By far the most important of these iron ores are the 

 Twin beds of fossil ore, — an ore notable for its purity, its uniformity of 

 structure, and its wide distribution. " It is believed," says Prof. Silliman, "to 

 be, of all deposits of iron ore in the known world, the most extensive and 

 important." 



Attention has been called, by Prof. Hull, the Director of the Geological 

 Survey of Ireland, to the brown haematite occurring in the Lower Silurian 

 rocks, at several localities in the counties of Longford and Cavan. 



A description of the iron ores of Nova Scotia, and the manufacture of 

 Acadian iron, has appeared in the " Mining Journal." It seems likely that 

 the present high price of iron may lead to the development of the iron- 

 producing resources of this colony. 



METALLURGY. 



Some improvements in effecting the removal of phosphorus from pig-iron, 

 during the process of puddling, have been introduced by Prof. Scheerer, of the 

 Mining Academy of Freiberg, in Saxony. Chloride of calcium and chloride 

 of sodium are mixed in about equal proportions, and the two salts fused 



