large as a pea, or the point of a small iron nail, was found fully adequate to preserve forty or fifty square inches of copper; and this, wherever it was placed, whether at the top, bottom, or in the middle of the sheet of copper, and whether the copper was straight or bent, or made into coils. And where the connection between the different pieces of copper was completed by wires, or thin filaments of the fortieth or fiftieth of an inch in diameter, the effect was the same; every side, every surface, every particle of the copper remained bright, whilst the iron, or the zinc, was slowly corroded. A piece of thick sheet copper, containing, on both sides, about sixty square inches, was cut in such a manner as to form seven divisions, connected only by the smallest filaments that could be left, and a mass of zinc, of the fifth of an inch in diameter, was soldered to the upper division. The whole was plunged under sea-water; the copper remained perfectly polished. The same experiment was made with iron; and after the lapse of a month, in both instances, the copper was found as bright as when it was first introduced, whilst similar pieces of copper, undefended, in the same sea-water, underwent considerable corrosion, and produced a large quantity of green deposit in the bottom of the vessel. Numerous other experiments were performed, and with results equally conclusive of the truth of the theory which had suggested them. It remained only that the experiments should be conducted on a large scale. The Lords Commissioners of the Navy accordingly gave Sir Humphry permission to ascertain the practical value of his discovery by trials upon ships of war; and the results, to use his own expression, even surpassed his most sanguine expectations. Sheets of copper, defended by from 1-40th to 1-1000th part of their surface of zinc, malleable and cast iron, were exposed, for many weeks, in the flow of the tide in Portsmouth harbour, their weights having been ascertained before and after the experiment. When the metallic protector was from 1-40 to 1-110, there was no corrossion nor decay of the copper; with small quantities it underwent a loss of weight. The sheathing of boats and ships, protected by the

being the first person on whom his Royal Highness conferred that dignity.

We now arrive at one of the most important results of Sir Humphry Davy's labours, viz. the invention of the safety-lamp for coal mines, which has been generally and successfully adopted throughout Europe. This invention has been the means of preserving many valuable lives, and preventing horrible mutilations, more terrible even than death. The general principle of the discovery may be described as follows:

The frequency of accidents, arising from the explosion of the fire-damp, or inflammable gas, of the coal mines, mixed with atmospherical air, occasioned the formation of a committee at Sunderland, for the purpose of investigating the causes of these calamities, and of endeavouring to discover and apply a preventive. Sir Humphry received an invitation, in 1815, from Dr. Gray, one of the members of the committee; in consequence of which he went to the north of England, and visiting some of the principal collieries in the neighbourhood of Newcastle, soon convinced himself that no improvement could be made in the mode of ventilation, but that the desired preventive must be sought in a new method of lighting the mines, free from danger, and which, by indicating the state of the air in the part of the mine where inflammable air was disengaged, so as to render the atmosphere explosive, should oblige the miners to retire till the workings were properly cleared. The common means then employed for lighting the dangerous part of the mines consisted of a steel wheel revolving in contact with flint, and affording a succession of sparks but this apparatus always required a person to work it, and was not entirely free from danger. The fire-damp was known to be light carburetted hydrogen gas; but its relations to combustion had not been examined. It is chiefly produced from what are called blowers or fissures in the broken strata, near dykes. Sir Humphry made various experiments on its combustibility and explosive nature; and discovered, that the fire-damp requires a very strong heat for its inflammation ; that azote and carbonic acid, even in very small proportions,

diminished the velocity of the inflammation; that mixtures of the gas would not explode in metallic canals or troughs, where their diameter was less than one seventh of an inch, and their depth considerable in proportion to their diameter ; and that explosions could not be made to pass through such canals, or through very fine wire sieves, or wire gauze. The consideration of these facts led Sir Humphry to adopt a lamp, in which the flame, by being supplied with only a limited quantity of air, should produce such a quantity of azote and carbonic acid as to prevent the explosion of the fire-damp, and which, by the nature of its apertures for giving admittance and egress to the air, should be rendered incapable of communicating any explosion to the external air. These requisites were found to be afforded by air-tight lanterns, of various constructions, supplied with air from tubes or canals of small diameter, or from apertures covered with wire-gauze, placed below the flame, through which explosions cannot be communicated, and having a chimney at the upper part, for carrying off the foul air. Sir Humphry soon afterwards found that a constant flame might be kept up from the explosive mixture issuing from the apertures of a wire-gauze sieve. He introduced a very small lamp in a cylinder, made, of wire-gauze, having six thousand four hundred apertures in the square inch. He closed all apertures except those of the gauze, and introduced the lamp, burning brightly within the cylinder, into a large jar, containing several quarts of the most explosive mixture of gas from the distillation of coal and air; the flame of the wick immediately disappeared, or rather was lost, for the whole of the interior of the cylinder became filled with a feeble but steady flame of a green colour, which burnt for some minutes, till it had entirely destroyed the explosive power of the atmosphere. This discovery led to a most important improvement in the lamp, divested the fire-damp of all its terrors, and applied its powers, formerly so destructive, to the production of a useful light. Some minor improvements, originating in Sir Humphry's researches into the nature of flame, were afterwards effected. Experiments

being the first person on whom his Royal Highness conferred that dignity.

We now arrive at one of the most important results of Sir Humphry Davy's labours, viz. the invention of the safety-lamp for coal mines, which has been generally and successfully adopted throughout Europe. This invention has been the means of preserving many valuable lives, and preventing horrible mutilations, more terrible even than death. The general principle of the discovery may be described as follows: —

The frequency of accidents, arising from the explosion of the fire-damp, or inflammable gas, of the coal mines, mixed with atmospherical air, occasioned the formation of a committee at Sunderland, for the purpose of investigating the causes of these calamities, and of endeavouring to discover and apply a preventive. Sir Humphry received an invitation, in 1815, from Dr. Gray, one of the members of the committee; in consequence of which he went to the north of England, and visiting some of the principal collieries in the neighbourhood of Newcastle, soon convinced himself that no improvement could be made in the mode of ventilation, but that the desired preventive must be sought in a new method of lighting the mines, free from danger, and which, by indicating the state of the air in the part of the mine where inflammable air was disengaged, so as to render the atmosphere explosive, should oblige the miners to retire till the workings were properly cleared. The common means then employed for lighting the dangerous part of the mines consisted of a steel wheel revolving in contact with flint, and affording a succession of sparks but this apparatus always required a person to work it, and was not entirely free from danger. The fire-damp was known to be light carburetted hydrogen gas; but its relations to combustion had not been examined. It is chiefly produced from what are called blowers or fissures in the broken strata, near dykes. Sir Humphry made various experiments on its combustibility and explosive nature; and discovered, that the fire-damp requires a very strong heat for its inflammation; that azote and carbonic acid, even in very small proportions,

:

Royal Society for 1815, and are extremely interesting. The concluding observations, in which he impresses the superior importance of permanency to brilliancy, in the colours used in painting, are especially worthy the attention of artists. On his examination of the Herculaneum manuscripts at Naples, in 1818-19, he was of opinion they had not been acted upon by fire, so as to be completely carbonised, but that their leaves were cemented together by a substance formed during the fermentation and chemical change of ages. He invented a composition for the solution of this substance, but he could not discover more than 100 out of 1265 manuscripts, which presented any probability of success.

Sir Humphry returned to England in 1820, and in the same year his respected friend, Sir Joseph Banks, President of the Royal Society, died. Several discussions took place respecting a proper successor, when individuals of high and even very exalted rank were named as candidates. But science, very properly in this case, superseded rank. Amongst the philosophers whose labours had enriched the transactions of the Royal Society, two were most generally adverted to, Sir Humphry Davy and Dr. Wollaston; but Dr. Wollaston, who had received from the council of the Society the unanimous compliment of being placed in the chair till the election by the body in November, declined any competition with his friend Sir Humphry Davy. Sir Humphry retained his seat as President till the year 1827, when, in consequence of procrastinated ill health, in great measure brought on by injuries occasioned to his constitution by scientific experiments, he was induced, by medical advice, to retire to the Continent. He accordingly resigned his seat as President of the Royal Society, the chair being filled, pro temp. by Davies Gilbert, Esq. who at the anniversary meeting, November 30. 1827, was unanimously elected President.

During his retirement on the Continent, Sir Humphry continued to communicate the results of his labours to the Royal Society; and at the anniversary meeting of the year 1827, one of the royal medals was awarded to him for a series of brilliant