was known to be nothing more than the hydrogen of the chemists, had its explosive tendencies very much restrained, by being mixed with a small quantity of carbonic acid and nitrogen, (the ingredient which, along with oxygen, forms atmospheric air ;) and that, moreover, if it did explode, when so mixed, the explosion would not pass through apertures less than one-seventh of an inch in diameter. Proceeding, therefore, upon these ascertained facts, he contrived his celebrated Safety Lamp. It consists of a small light, fixed in a cylindrical vessel, which is every where air-tight, except in the bottom, which is formed of fine wire gauze; and in the upper part, where there is a chimney for carrying off the foul air The air admitted through the gauze suffices to keep up the flame; which, in its combustion, produces enough of carbonic acid and nitrogen to prevent the fire-damp, when inflamed within the cylinder, from communicating the explosion to what is without. The heretofore destructive element, thus caught and detained, is therefore not only rendered harmless, but actually itself helps to furnish the miner with light, the whole of the interior of the cylinder being filled with a steady green flame, arising from the combustion of the hydrogen, which has been admitted to contact with the heat, but cannot carry back the inflammation it has received, to the general volume without. Armed with this admirable protection, therefore, the miner advances without risk, and with sufficient. light to enable him to work, into recesses which formerly he could not have dared to enter. The safety lamp has already been the means of saving many lives, and has enabled extensive mines, or portions of mines, to be wrought, which but for its assistance must have remained unproductive. The coal-owners of the northern districts, invited Sir Humphrey, in 1817, to a public dinner, and presented him with a service of plate, of the value of £2000, [$8,888,] in testimony of what they felt to be the merit of this invention.

We will mention only another of this eminent individual's ingenious practical applications of those scientific truths with which he enriched the philosophy of his age.

About the year 1823, the attention of the Commissioners of the British Navy was so strongly excited, to the fact of the rapid decay of the copper sheathings of ships, when exposed to the action of the salt water, that they applied to the Royal Society, to take the subject into consideration, and endeavor to devise a remedy for the evil. On this occasion, Davy again had recourse to those principles of electro-chemistry, of which he had himself been the discoverer, and by the application of which, he had already obtained so many brilliant results. One of the laws of electrical agency, which he considered himself to have ascertained, was, that two substances can only combine, by what is called chemical affinity or attraction, when they are in opposite electrical states,—that is to say, when the one is positively, and the other negatively, electrified. The copper and the water, therefore, he concluded, were naturally in these circumstances; and all that would be required, consequently, to prevent the action of the one upon the other, would be, to change the electrical condition of that one of them, namely, the copper, which it was possible to submit to the necessary treatment. He thought of various ways of effecting this object; but, at last, he determined to try the effect of merely placing a quantity of zinc or iron in contact with the copper; the former metals being more positive than the latter, and therefore fitted, by induction, to repel a portion of its electricity, and so to render it negative like the water. The result surpassed his expectations. So powerfully did the one metal act, in reversing the electrical state of the other, that a bit of zinc or iron, no larger than a pea, was found sufficient to protect from corrosion, forty or fifty square inches of copper. Nothing, therefore, could be more perfect, than the success of this contrivance, for the particular purpose it was intended to serve. But, unfortunately, it has been found, by experience, that, although Davy's method completely answers for preventing the wasting of the copper, the sea-weeds and marine insects accumulate, in such quantities, upon the bottoms of ships so protected, that they become, after a short time, scarcely navigable. For the present, therefore, the

use of the zinc and iron is of necessity abandoned. It is by no means improbable, however, that some expedient may be contrived, for counteracting this consequence of the application of Davy's invention; in which case, it will be entitled to rank as one of the most valuable discoveries, ever made.

6

We have thus, guided chiefly by the Memoir,' of which mention has been made above, pursued the principal triumphs of Sir Humphrey's splendid career, and described what he achieved, although cursorily and briefly, in such a manner, we trust, as to put even the unscientific reader in possession of a tolerably just view of the great discoveries on which his fame rests. In 1827, as we have already mentioned, his health had become so bad, that he found it necessary to resign the presidency of the Royal Society. Immediately after this, he proceeded to the Continent. During his absence from England, he still continued to prosecute his chemical researches, the results of which he communicated, in several papers, to the Royal Society. He also, notwithstanding his increasing weakness and sufferings, employed his leisure in literary composition, on other subjects, an evidence of which appeared in his Salmonia,' a treatise on fly-fishing, which he published in 1828. This little book is full of just and pleasing descriptions of some of the phenomena of Nature, and is imbued with an amiable and contented spirit. His active mind, indeed, continued, it would seem, to exert itself, to the last, almost with as unwearied ardor as ever. Besides the volume we have just mentioned, another work, entitled The Last Days of a Philosopher,' which he also wrote during this period, has been given to the world, since his death. He died at Geneva, on the 30th of May, 1829. He had only arrived in that city the day before; and having been attacked by apoplexy, after he had gone to bed, expired at an early hour in the morning.

No better evidence can be desired, than that we have in the history of Davy, that a long life is not necessary to enable an individual to make extraordinary advances in any intellectual pursuit, to which he will devote himself with

all his heart and strength. This eminent person was, indeed, early in the arena, where he won his distinction ; and the fact, as we have already remarked, is a proof, how diligently he must have exercised his mental faculties, during the few years that elapsed between his boyhood and his first appearance before the public, although, during this time, he had scarcely any one to guide his studies, or even to cheer him onward. Yet, notwithstanding that he had taken his place, as we have seen, among the known chemists of the age, almost before he was twenty-one, the whole of his brilliant career in that character, embracing so many experiments, so many literary productions, and so many splendid and valuable discoveries, extended only over a space of not quite thirty years. He had not completed his fifty-first year, when he died. Nor was Davy merely a man of science. His general acquirements were diversified and extensive. He was familiar with the principal continental languages, and wrote his own with an eloquence not usually found in scientific works. All his writings, indeed, show the scholar, and the lover of elegant literature, as well as the ingenious and accomplished philosopher. It not unfrequently happens, that able men, who have been their own instructers, and have chosen for themselves some one field of exertion, in which the world acknowledges, and they themselves feel, their eminence, both disregard and despise all other sorts of knowledge and acquirement. This is pedantry, in its most vulgar and offensive form; for it is not merely ignorant, but intolerant. It speaks highly in favor of the right constitution and the native power of Davy's understanding, that, educated as he was, he escaped every taint of this species of illiberality; and that, while, like almost all those who have greatly distinguished themselves in the world of intellect, he selected and persevered in his one favorite path, he nevertheless revered wisdom and genius, in all their manifestations.

INTELLECTUAL EXCELLENCE.

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CHAPTER VI.

Diversities of Intellectual Excellence :-English Painters :-Spencer; Highmore; Hannam; Wright; Gilpin; Gainsborough; Barry; Lawrence.

THE ambition of intellectual excellence is, in truth, the same passion, by whichsoever of the many roads that lie open to it, it may choose to pursue its object. The thing that is interesting and valuable is the purity and enduring strength of the passion. These are the qualities that make it both so inestimable in the possession, and so instructive in the exhibition. The mere department of study in which it displays itself, is of inferior importance; for, even if it should be contended that, of the various pursuits which demand the highest degree of intellectual application and devotion, one is yet better calculated than another to promote, by its results, the general improvement or happiness of mankind, it will scarcely be argued, that even those of inferior value, in this respect, should not also have their followers. The arrangements of Providence, by forming men at first in different moulds, and placing them afterwards in different circumstances, regulate, doubtless with more wisdom and success than could be attained by any artifice of human polity, the distribution of taste, and talent, and enterprise, over the varied field of philosophy and art, no part of which is thus left altogether uncultivated. One man, from his original endowments, or his particular advantages of training or situation, is more fit for one line of exertion, another for another; and, although the pursuits to which they are in this manner severally attracted, may not, in the largest view, be of equal importance, that is no reason why we should regret that there are laborers to engage in each. Indeed, the more truly enlightened any mind is,