On January 11th, 1816, he read a second paper to the Royal Society, entitled, “An account of an invention for giving light in explosive mixtures of fire-damp in coal mines by consuming the fire-damp,” in which he shows that the tubes or canals as well as the sides of the lanterns may be replaced by cages or cylinders of wire gauze. The inflammable mixture will readily pass through the meshes of the gauze and will burn within it, filling the cylinder with a bright flame, but no explosion will pass outwards, even although the wire becomes heated to redness.
A fortnight later he read a third paper to the Society, “On the Combustion of Explosive Mixtures confined by Wire Gauze, with some Observations on Flame,” in which he gives the results of further inquiries respecting the limits of the size of the apertures, and of the wire in the metallic gauze required to shield the flame of an oil-lamp, and describes a number of illustrations of the action of the gauze in lowering the temperature of the explosive mixture below the point of ignition. Some of these illustrations are now among the stock experiments of the lecture theatre. He offers some observations concerning the essential nature of flame, and concludes by informing the Society that his “cylinder lamps [i.e. lamps of which the flames are enclosed within a cylinder of gauze: see [Fig. 11], p. 199] have been tried in two of the most dangerous mines near Newcastle with perfect success.”
The form which the lamp finally took in the hands of Mr. Newman, the instrument-maker, is seen on p. [200].
The trials above referred to were first made by Mr. Matthias Dunn and the indefatigable Mr. Hodgson in the Hebburn Colliery, and shortly afterwards by Mr. John Buddle in the Wall’s End Colliery. Mr. Buddle has placed on record his impressions of his first experience.
“I first tried it,” he says, “in an explosive mixture on the surface; and then took it into a mine; ... it is impossible for me to express my feelings at the time when I first suspended the lamp in the mine and saw it red hot.... I said to those around me ‘We have at last subdued this monster.’”
Some months afterwards Davy accompanied Mr. Buddle into the pit and saw his lamp in actual use.
“Sir Humphry was delighted,” says Mr. Buddle, “and I was overwhelmed with feelings of gratitude to that great genius which had produced it.”
Further testimony of Mr. Buddle’s appreciation of this memorable invention may be seen from the following extract from a letter by him to Davy. It is not only interesting in view of Davy’s remark that “the evidence of the use of a practical discovery is of most value when furnished by practical men,” but also as showing the rapidity with which the discovery was taken advantage of:—
“Walls End Colliery, Newcastle, June 1st, 1816.
“After having introduced your safety lamp into general use in all the collieries under my direction, where inflammable air prevails, and after using them daily in every variety of explosive mixture, for upwards of three months, I feel the highest possible gratification in stating to you that they have answered to my entire satisfaction.
“The safety of the lamps is so easily proved by taking them into any part of a mine charged with fire-damp, and all the explosive gradations of that dangerous element are so easily and satisfactorily ascertained by their application, as to strike the minds of the most prejudiced with the strongest conviction of their high utility; and our colliers have adopted them with the greatest eagerness.
“Besides the facilities afforded by this invention to the working of coal mines abounding in fire-damp, it has enabled the directors and superintendents to ascertain, with the utmost precision and expedition, both the presence, the quantity, and the correct situation of the gas. Instead of creeping inch by inch with a candle, as is usual, along the galleries of a mine suspected to contain fire-damp, in order to ascertain its presence, we walk firmly in with the safe lamps, and with the utmost confidence prove the actual state of the mine. By observing attentively the several appearances upon the flame of the lamp, in an examination of this kind, the cause of accidents which have happened to the most experienced and cautious miners is completely developed; and this has been, in a great measure, matter of mere conjecture.
“I feel peculiar satisfaction in dwelling upon a subject which is of the utmost importance, not only to the great cause of humanity, and to the mining interest of the country, but also to the commercial and manufacturing interests of the United Kingdom; for I am convinced that by the happy invention of the safe lamp large proportions of the coal mines of the empire will be rendered available, which otherwise might have remained inaccessible, at least without an invention of similar utility, which could not have been wrought without much loss of the mineral, and risk of life and capital.
“It is not necessary that I should enlarge upon the national advantages which must necessarily result from an invention calculated to prolong our supply of mineral coal, because I think them obvious to every reflecting mind; but I cannot conclude, without expressing my highest sentiments of admiration for those talents which have developed the properties, and controlled the power, of one of the most dangerous elements which human enterprise has hitherto had to encounter.”