dividual'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 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 endeavour to devise a remedy for the evil. On this occasion, Davy again had recourse to those principles of electro-chymistry, 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 chymical 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 pur

pose 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 seaweeds 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.

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 chymical researches, the results of which he communicated 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 ardour 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 chymists 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 favour 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 a world of intellect, he selected and persevered in his one favourite path, he nevertheless revered wisdom and genius in all their manifestations.

CHAPTER IV.

Diversities of Intellectual Excellence.-Artists.-Benjamin

West.

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 afterward 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 labourers to engage in each. Indeed, the more truly enlightened any mind is, the less ready will it be to look with a feeling either of contempt or of slight respect upon any pursuit, which has had power to call forth, in an eminent degree, the resources of the human intellect. The farther the domain of science is explored, the more, in all probability, will it be found to be pervaded and connected, in all its parts, by a principle of order, consistency, and unity; and the more confirmations shall we discover of what are almost already universally admitted axioms of philosophy, that no truth is without its worth, and no sort of knowledge without some bearing upon every other.

We are now about to notice the exertions made in pursuit of knowledge by some individuals whose paths have been very different from those of the distinguished discoverers and inventors with whom we have just been engaged. But we shall find that, in every variety of intellectual enterprise, the same devotion and diligence have been exhibited by ardent and generous spirits; and that everywhere these qualities are the indispensable requisites for the attainment of excellence. By no class of students, perhaps, has a greater love of their chosen