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on Flame:" "In reasoning upon the various phenomena brought about by my various experiments, it occurred to me, -as considerable heat was required for the inflammation of the fire-damp, and as it produced, in burning, a comparatively small degree of heat, that the effect of carbonic acid or azote, and of the surfaces of the small tubes in preventing its explosion, depends upon their cooling powers, or their lowering the temperature of the exploding-mixture so much that it was no longer sufficient for its continuous inflammation."

Mr. Stephenson's lamp has been much improved. It consists of a glass cylinder above the lamp, covered by a cylinder of wire gauze; and, instead of air passing through the perforated plate, it passes through the meshes of the gauze (Fig. 1).

The Davy lamp differs from the Stephenson, inasmuch as the former admits air through the meshes of the wire on all sides: consequently, when immersed in an inflammable mixture, the whole cylinder becomes filled with flame, and ultimately the wires become red-hot. Yet they radiate sufficient heat to keep the temperature of the wires below that required for the passage of flame through the meshes, and the lamp continues to burn with safety if kept in a still atmosphere.

Stephenson's lamp, on the contrary, only admits air



§ 13.

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

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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

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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:

Davy lamp (gauze)
Stephenson, or Georgie
Upton and Roberts

Clanny (glass)

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Parish (gauze)
Mueseler's (glass)

Davy (without gauze)

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Candle-power. 8

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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 a 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.
Clanny lamp went out at 17′ 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

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