the wick of the lamp, in the wire-gauze cylinder, the coal miner, there is every reason to believe, will be supplied with light in mixtures of fire-damp no longer explosive; and should his flame be extinguished by the quantity of fire-damp, the glow of the metal will continue to guide him; and by placing the lamps in different parts of the gallery, the relative brightness of the wire will show the state of the atmosphere in these parts. Nor can there be any danger with respect to respiration whenever the wire continues ignited; for even this phenomenon ceases when the foul air forms about two-fifths of the volume of the atmosphere.

"I introduced into a wire-gauze safe lamp a small cage made of fine wire of platinum, of the one-seventieth of an inch in thickness; and fixed it by means of a thick wire of platinum, about two inches above the wick, which was lighted. I placed the whole apparatus in a large receiver, in which, by means of a gas holder, the air could be contaminated to any extent with coal gas. As soon as there was a slight admixture of coal gas, the platinum became ignited; the ignition continued to increase till the flame of the wick was extinguished, and till the whole cylinder became filled with flame; it then diminished, when the quantity of coal gas was increased, so as to extinguish the flame. At the moment of the extinction the cage of platinum became white-hot, and presented a most brilliant light. By increasing the quantity of the coal gas still further, the ignition of the platinum became less vivid: when its light was barely sensible, small quantities of air were admitted; its heat speedily increased; and by regulating the admission of coal gas and air, it again became white

hot, and soon after lighted the flame in the cylinder, which, as usual, by the addition of more atmospherical air, rekindled the flame of the wick.

"This experiment has been very often repeated, and always with the same results. When the wire for the support of the cage, whether of platinum, silver, or copper, was very thick, it retained sufficient heat to enable the fine platinum wire to rekindle in a proper mixture half a minute after its light had been entirely destroyed by an atmosphere of pure coal gas; and by increasing its thickness, the period might be made still longer.

"The phenomenon of the ignition of the platinum takes place feebly in a mixture consisting of two of air and one of coal gas, and brilliantly in a mixture consisting of three of air and one of coal gas: the greater the quantity of heat produced, the greater may be the quantity of the coal gas; so that a large tissue of wire will burn in a more inflammable mixture than one made red-hot. If a mixture of three parts of air and one of fire-damp be introduced into a bottle, and inflamed at its point of contact with the atmosphere, it will not explode, but will burn like a pure inflammable substance. If a fine wire of platinum, coiled at its end, be slowly passed through the flame, it will continue ignited in the body of the mixture; and the same gaseous matter will be found to be inflammable, and to support combustion.

"There is every reason to hope that the same phenomena will occur with the cage of platinum in the fire-damp as those which have been described in its operation on mixtures of coal gas. In trying experiments in fire-damp, the greatest care must be taken

that no filament, or wire of platinum, protrudes on the exterior of the lamp, for this would fire externally an explosive mixture. However small the mass of platinum which kindles an explosive mixture in the safe lamp, the result is the same as when large masses are used: the force of the explosion is directed to, and the flame arrested by, the whole of the perforated tissue.

"When a large cage of wire of platinum is introduced into a very small safe lamp, even explosive mixtures of fire-damp are burnt without flame; and by placing any cage of platinum in the bottom of the lamp round the wick, the wire is prevented from being smoked."

The discovery announced in this paper was soon followed by that of M. Doebereiner of the property possessed by platinum, in a very finely divided state, of becoming ignited at ordinary temperatures in a mixture of oxygen and hydrogen; and so strongly ignited, owing to the rapidity of combination which it effected, as to inflame the mixture. And this fact, further investigated, soon led to a large number of other curious results relative to the influence of metals in producing chemical combinations, hardly less extraordinary and interesting than the power exhibited in the voltaic pile of the same bodies in different forms and arrangements, of separating the elements of compounds or occasioning decomposition.

To return to the safety lamp.-After pointing out, in the fourth and last section of his work, various precautions in different circumstances to ensure the perfect security of the lamp, deduced from his researches on flame, and for improving its light, and after having described various applications of it as

indicated in the title page, he concludes with observing:

"Whatever may be the fate of the speculative part of this inquiry, I have no anxiety as to the practical results, or as to the unimpassioned and permanent judgment of the public on the manner in which they have been developed and communicated; and no fear that an invention for the preservation of human life, and the diminution of human misery, will be neglected or forgotten by posterity. When the duties of men coincide with their interests, they are usually performed with alacrity: the progress of civilisation ensures the existence of all real improvements; and however high the gratification of possessing the good opinion of society, there is a still more exalted pleasure in the consciousness of having laboured to be useful."

These remarks were dictated by strong feeling, arising from a perfect knowledge of what he had effected, and from a perfect confidence of the efficiency of his invention. In no part of his work, which he designed as a permanent record of his labours in the cause, does he make any allusion to various attempts unworthily engaged in to detract from the merit and originality of his invention. That they annoyed him at the moment, was certain; he must have been more than human had he been indifferent to them; but, fortunately, they had no lasting influence on his mind. He thus expresses himself, in relation to them, in some lines which were hastily written in a notebook:

"Though good

Has been repaid with evil, and a gift
Of science and humanity received
With stern ingratitude; yet have I not

In further illustration, I shall insert a letter already published by Dr. Paris, in which the principal attempt to deprive him of the honour of the discovery is represented in its true light.

"To J. G. Lambton, Esq.

"MY DEAR SIR,

Queen Square, Bath, October 29. 1816.

"The severe indisposition of my wife has altered my plans. Your letter slowly followed me here.

"Mr. is one of the persons who, after I had advanced a principle of security for a lamp, came upon the ground to endeavour to jockey me. I was not looking to a prize; I merely came forward to show an animal, the breed of which might be useful, when Mr. &c. brought their sorry jades, which had never before been seen or heard of, to kick at my blood mare.

Dr.

"I never heard a word of George Stephenson and his lamps till six weeks after my principle of security had been published; and the general impression of the scientific men in London, which is confirmed by what I heard at Newcastle, is, that Stephenson had some loose idea floating in his mind which he had unsuccessfully attempted to put in practice till after my labours were made known: then he made something like a safe lamp, except that it is not safe; for the apertures below are four times, and those above twenty times too large. But even if Stephenson's