I venture to claim for this method of detecting fire-damp among other advantages:  1.  The detecter, on account of its size, can be placed in a break in the roof where an ordinary lamp—­even a small Davy—­could not be put, and a purer sample of the suspected atmosphere is obtained than would be the case even a few inches below the level of the roof, 2.  The obtaining and testing of a sample in the manner above described takes away the possibility of an explosion, which might be the result if a lamp with a defective gauze were placed in an explosive atmosphere.  No one knows how many explosions have not been caused by the fire-trier himself.  This will now be avoided. (Although lamps fitted with a tin shield will be subjected to the same strict examination as hitherto, still they do not admit of the same frequent inspection as those without shields, for in the latter case each workman can examine his own lamp as an extra precaution; whereas the examination of the tin shield lamps will rest entirely with the lamp man.) 3.  The lamp can be kept in a pure atmosphere while the sample is obtained by the detecter, and at a greater height than the flame in a safety-lamp could be properly distinguished.  The test can afterward be made in a safe place, at some distance from the explosive atmosphere; and, owing to the vacuum formed, the ball (without closing the mouthpiece) has been carried a mile or more without the gas escaping. 4.  The detecter supplies a better knowledge of the condition of the working places, especially in breaks and cavities in the roof; which latter, with the help of a nozzle and staff, may be reached to a height of ten feet or more, by the detecter being pressed against the roof and sides, or by the use of a special form of detecter. 5.  Being able at will to force the contents of the detecter on to the flame, the effects of an explosion inside the lamp need not be feared.  (This danger being removed, admits, I think, of the glass cylinder being made of a larger diameter, whereby a better light is obtained; it may also be considered quite as strong, when used with the detecter, as a lamp with a small diameter, when the latter is placed in an explosive atmosphere.) 6.  The use of the detecter will permit the further protection of the present tin shield lamp, by an extra thickness of gauze, if such addition is found advantageous in resisting an increased velocity. 7.  In the Mueseler, Stephenson, and other lamps, where the flame is surrounded by glass, there is no means of using the wire for shot firing.  The detecter tube, although protected by two thicknesses of gauze, admits of this being done by the use of a special form of valve turned by the mouthpiece of the detecter.  The system of firing shots or using open lamps in the same pit where safety lamps are used is exceedingly objectionable; still, under certain conditions shots may be fired without danger.  Whether safety lamps or candles are used, it is thought the use of the detecter will