most likely led to the invention of the ball and protected tube were
probably never thought of until recently; indeed, Mr. Garforth writes that
he has only learned about them since his paper was read before the Midland
Institute, and some weeks after his patent was taken out.

No one, says Mr. Garforth, in his paper read before the Midland Institute,
will, I presume, deny that the Davy is more sensitive than the tin shield
lamp, inasmuch as in the former the surrounding atmosphere or explosive
mixture has only one thickness of gauze to pass through, and that on a
level with the flame; while the latter has a number of small holes and two
or three thicknesses of gauze (according to the construction of the lamp),
which the gas must penetrate before it reaches the flame. Moreover, the tin
shield lamp, when inclined to one side, is extinguished (though not so
easily as the Mueseler); and as the inlet holes are 6 inches from the top,
it does not show a thin stratum of fire-damp near the roof as perceptibly
as the Davy, which admits of being put in almost a horizontal position.
Although the Davy lamp was, nearly fifty years ago, pronounced unsafe, by
reason of its inability to resist an ordinary velocity of eight feet per
second, yet it is still kept in use on account of its sensitiveness. Its
advocates maintain that a mine can be kept safer by using the Davy, which
detects small quantities of gas, and thereby shows the real state of the
mine, than by a lamp which, though able to resist a greater velocity, is
not so sensitive, and consequently is apt to deceive. Assuming the Davy
lamp to be condemned (as it has already been in Belgium and in some English
mines), the Stephenson and some of the more recently invented lamps
pronounced unsafe, then if greater shielding is recommended the question
is, what means have we for detecting small quantities of fire-damp?

It would seem from the foregoing remarks that in any existing safety-lamp,
where one qualification is increased another is proportionately reduced; so