GARFORTH: FIRE-DAMP DETECTOR. 
399 
qualifications can ever be combined in one lamp. The writer believes 
they cannot, and with a view of making the Tin shield or any other 
description of protected lamp as equally sensitive as the Davy, he 
has invented the Detector as the most suitable adjunct or second 
vessel to the lamp. 
The Detector, as will be noticed from the one exhibited, simply 
consists of an India rubber ball, so small that all the air within it is 
expelled by the compression of one hand, and a pure sample of the 
suspected atmosphere obtained. If the ball were larger, and a portion 
of the air remained, the sample would then be diluted. It has been 
found by a great number of trials that it obtains quite sufficient gas 
for testing purposes. That only one hand should be engaged in 
testing is an indispensible condition, on account of holding the lamp, 
&c. It will be apparent that by the ordinary action of compressing 
the ball and then allowing it to expand, a vacuum is formed within 
it, and a sample of the suspected atmosphere drawn from the breaks 
and cavities of the roof or any part of the mine. 
When the sample is forced through the tube near the flame, 
gas, if present, at once reveals itself by the elongation of the flame 
in the ordinary way ; at the same time burning with a blue flame at 
the top of the test tube. If gas is not present, the distinction is easily 
seen by the flame keeping the same size, but burning with greater 
brightness owing to the increased quantity of oxygen forced upon it. 
The advantages claimed for this method of detecting fire-damp 
are : — 
1. — The Detector, 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 method of obtaining and testing a sample as 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. 
(Although lamps fitted with a tin shield will be subjected to 
the same strict examination as hitherto, still they do not admit of 
