400 
GAEFORTH: FIRE-DAMP DETECTOR. 
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 lampman). 
3. — The lamp can be kept in a pure atmosphere, whilst the 
sample is obtained by the Detector, and at a greater height than the 
flame in a safety lamp could be properly distinguished. The test 
can afterwards 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 Detector supplies a better knowledge of the condition 
of ihe 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 Detector being pressed against 
the roof or sides, or by the use of a special form of Detector. 
5. — Being able at will to force the contents of the Detector on 
to the flame, the effects of an explosion inside the lamp need not be 
feared. 
6. — The use of the Detector 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 testing for gas with a safety lamp, there is a fear of the 
light being extinguished, when the lamp is suddenly placed in a 
quantity of gas, or in endeavouring to get a very small hght ; this 
is especially the case with some kinds of lamps. With the Detector 
this is avoided, as a large flame can be used, which is considered by 
some a preferable means of testing for small quantities, and the test 
can be made without risk. Where gas is present in large quantities, 
the blue flame at the end of the test tube will be found a further 
proof. This latter result is produced by the slightest compression 
of the ball. 
(I need not point out the inconvenience and loss of time in 
having to travel a mile or more to re-light. 
Although the question of safe lighting is one of the most impor- 
tant connected with coal mining (for without a light no work could 
