through a few meshes, the glass globe preventing the entry of any air or gas from the sides: therefore only a small proportion of gas can enter the interior of the lamp: hence, never being filled with flame, the wires of the gauze remain uninjured. Upon these principles, various modifications have been made to these lamps, until they now number a hundred or more. The Clanny lamp consists of a cylinder of glass around the flame, and a wire-gauze top. A better light is produced by this combination (Fig. 2). The figures show the different lamps, with permutation-lock capable of many thousand changes, so that no one but the fire-boss. can unlock the lamps. The Mueseler lamp, used in Belgium, has a glass cylinder for the light, and a gauze top (Fig. 4). There is a copper chimney to carry off the smoke of the burner, and to force the air downward between the glass cylinder and the chimney upon the flame of the burner, admitting the air through the gauze at the top. The Boty lamp has a glass cylinder with a gauze top, but the air is admitted through a perforated copper ring at the bottom of the lamp. The Eloin lamp has a glass cylinder, admitting air through wire gauze near the bottom of the lamp, which is thrown against the burner by a thin copper cap. No other air enters the lamp, and consequently it is easily extinguished. Many lamps are constructed to give increased light by using glass globes. The Hall lamp, with diaphoretic lens, is the most noteworthy, on account of its construction. The Williamson double safety-lamp is a Clanny and Boty lamp combined (Fig. 5). The illuminating power of the various lamps in most common use has been given as below; the standard being a wax candle, six to the pound: 14. The South Shields Committee considered the Davy absolutely unsafe. Mr. Darlington came to the same conclusion, and in answer to the question, "Is it not fact that dust will fly off in sparks, and that one spark would create an explosion?" said, "There are very many instances of accidents taking place that we could attribute to nothing else." Experiments made by Mr. N. Wood at Killingworth Colliery, in 1853, to ascertain at what velocity the flame may be passed in an explosive mixture of fire-damp, were as follows: Davy lamp when moving 13′ per second. Boty lamp passed flame when moving at 15' per second. Hall lamp did not pass flame at 13′ per second. Stephenson lamp was extinguished at less than 13′ per second. Eloin lamp went out as soon as it was filled with gas. Upton and Roberts lamp went out as soon as it was filled with gas. The Belgium Commission, appointed by the king in 1868, observed, that "the Davy and Deputy lamps, when exposed for two minutes to an explosive mixture of air and lighting-gas, moving at a velocity of 4.264' per second, do not pass the flame through the gauze; but, when the velocity reaches or surpasses 7.38', the explosion is always produced on the outside, save in cases of extinction by asphyxia, caused by the admission of a large quantity of gas. It was also noticed that explosion takes place after from five to ten seconds when the velocity is 9.84', and after from two to five seconds when the speed is 19.68'. "With the Mueseler lamp, out of a one hundred and fifteen experiments, there were twenty-one cases of complete extinction at a velocity of 19.68' per second. "The Morison lamp was considered of very complicated construction, and as giving a very bad light in stagnant air. Out of eleven experiments at a velocity of 19.68′ per second, these lamps caused neither exterior explosions, nor any inflammation of gas in the exterior cylinder. 66 Rapid currents of air are dangerous when their action manifests itself by the crushing of the flame upon the wicks: indeed, the relative security of the Mueseler lamp does not depend alone on the smallness of the section of the chimney at the top, or on its height, but rests essentially in the regularity of the draught." The North of England Institute of Mining Engineers, which has been so instrumental in the furtherance of mining knowledge, appointed a committee, who rendered in their report the following concerning the velocity at which the various lamps would explode : — |