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the infusible nature of the earths; the strong affinity of their bases for oxygen made it unavailing to act upon them in solution in water; and the only methods that proved successful, were those of operating upon them by electricity in some of the combinations, or of combining them at the moment of their decomposition by electricity, in metallic alloys, so as to obtain evidences of their nature and properties. It is impossible to follow the philosopher through all the intricate paths of this investigation: suffice it to say, that, although he was unable to produce the metallic bases of the earths in the same unequivocal form as he produced those of the alkalies, he furnished sufficient evidence of their being metallic oxides.

Sir Humphrey Davy's Bakerian Lecture of 1808, entitled, "An Account of some new Analytical Researches on the Nature of certain Bodies, particularly the Alkalies, Phosphorus, Sulphur, Carbonaceous Matter, and the Acids hitherto undecomposed; with some general Observations on CHEMICAL THEORY," abounds in elaborate experiments with the Voltaic apparatus, made with the hope of extending our knowledge of the principles of bodies, by the new powers and methods arising from the applica. tion of electricity.

Shortly after the close of the war, the commissioners of the navy, fully impressed with the evil arising from the destructive influence of sea-water upon the copper sheathing of his majesty's ships of war, applied to the council of the Royal Society, in the hope that some plan might be suggested for arresting, if not for preventing, the decay of so expensive an article. Sir

H. Davy charged himself with the inquiry; and presented its results in a paper, which was read before the society on the 22d of January, 1824, and which was continued in another communication dated 17th of June, 1824, and concluded in a third, read 9th of June, 1825. We shall endeavour briefly to state the principal facts elicited by this inquiry. We have already stated, that Davy had advanced the hypothesis, that chemical and elec. trical changes were identical, or dependant upon the same property of matter; and that he had shown that chemical attractions may be exalted, modified, or destroyed, by changes in the electrical states of bodies; that substances will only combine when they are in differ. ent electrical states; and that, by bringing a body, naturally positive, artificially into a negative state, its usual powers of combination are altogether destroyed: it was, in short, by an application of this ve ry principle that he decomposed the alkalies; and it was from the same energetic instrumentality that he now sought a remedy for the rapid corrosion of copper sheathing. When a piece of polished copper is suffered to remain in sea-water, the first effects are, a yellow tarnish upon the surface, and a cloudiness in the water, which take place in two or three hours: the hue of the cloudiness is at first white, and it gradually becomes green. In less than a day a bluish-green precipitate appears in the bottom of the vessel, which constantly accumulates; this green matter, appears principally to consist of an insoluble compound of copper (a sub-muriate) and hydrate of magnesia. Reasoning up. on these phenomena, Davy arrived at the conclusion that copper could

act upon sea-water only when in a positive state; and since that metal is only weakly positive in the elec. tro-chemical scale, he considered that, if it could be only rendered slightly negative, the corroding action of sea-water upon it would be null.

A piece of zinc, as large as a pea, on 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 connexion between the different pieces of copper was completed by wires, or thin filaments of the fortieth or fif. tieth of an inch in diameter, the ef. fect 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 divi. sions, connected only by the small. est 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 deposite in the bottom of the vessel. It remained only that the ex

periments 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 corrosion nor decay of the copper; with small quantities it underwent a loss of weight. The sheathing of boats and ships, protected by the contact of zinc, cast and malleable iron, in different proportions, compared with that of similar boats and sides of ships unprotected, exhibited bright surfaces, whilst the unprotected copper underwent rapid corrosion, becoming first red, then green, and losing a part of its substance in scales. In overcoming one evil, another, however, has been croated; by protecting the copper,

the accumulation of sea weeds and marine insects has been favoured, and the ships thus defended by iron or zinc have become so foul, as scarcely to continue navigable. This would seem to depend upon several causes, especially upon the deposition of saline and calcareous matter, arising from the decomposition of marine salts. Had Davy's health remained unimpaired, his genius would, without doubt, have suggested a remedy; but he unfor. tunately declined in health, at the

very moment his energies were most required. Future philosophers may propose successful expedients to obviate the evil, but the glory of the discovery will justly belong to him who first developed the principle. Whether or not that principle can be rendered subservient to the protection of copper sheathing, it must at least be admitted that the results obtained by him are of the most interesting description, and capable of various useful applications; several of which he has himself suggested, whilst others have been discovered by the ingenuity of contempory chemists. By introducing a piece of zinc, or tin, into the iron boiler of the steam engine, we may prevent the danger of explosion, which generally arises, especially where salt water is used, from the wear of one part of the boiler. Another important application is in the prevention of the wear of the paddles, or wheels, which are rapidly dissolved by salt water. Mr. Pepys has extended the principle, for the preservation of steel instruments, by guards of zinc; and razors and lancets have been thus defended with perfect success.

In 1812 Mr. Davy married. The object of his choice was Jane, daughter of Charles Kerr, of Kelso, and widow of Shuckburgh Ashby A preece.

We now arrive at one of the most important results of Sir Humphrey Davy's labours, viz. the invention of the safety lamp for coal mines, which has been generally and successfully adopted throughout Eu

rope.

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:

Sir

The common means formerly 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. Humphrey 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 Humphrey 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 afford. ed by air-tight lanterns, of various constructions, supplied with air from tubes or canals of small di ameter, or from apertures covered with wire-gauze, placed below the flame, through which explosions cannot be communicated, and hav. ing a chimney at the upper part, for carrying off the foul air. Sir Humphrey soon afterwards found that a constant flame might be kept up from the explosive mixture is. suing from the apertures of a wireHe introduced a vegauze seive. ry 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. The coal owners of the Tyne and Wear evinced their sense of the benefits resulting from this invention, by presenting Sir Humphrey with a handsome service of plate worth nearly 2000l., at a public dinner at Newcastle, October 11, 1817.

In 1813, Sir Humphrey was elected a corresponding member of the Institute of France, and vice-presi

dent of the Royal Institution. He was created a Baronet, October 20, 1818. In 1820, he was elected a foreign associate of the Royal Academy of Sciences at Paris, in the room of his countryman Watt; and in the course of a few years, most of the learned bodies in Europe enrolled him among their members.

Many pages might be occupied with the interesting details of Sir Humphrey Davy's travels in different parts of Europe for scientific purposes, particularly to investigate the causes of volcanic phenomena, to instruct the miner of the coal dis tricts in the application of his safety lamp, to examine the state of the Herculaneum manuscripts, and to illustrate the remains of the chemical arts of the ancients. The results of all these researches were published in the transactions of the 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 espe. cially 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 carbonized, but that their leaves were cemented together by a substance formed during the fermentation and chemical changes 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 Humphrey returned to England in 1820, and in the same year his respected friend, Sir Joseph Banks, President of the Royal So

ciety, died, when he was elected his successor. Sir Humphrey retained his seat till the year 1827, when, in consequence of procrastinated ill health, he resigned his seat as President of the Royal Society.

Sir Humphrey Davy was, in eve. ry respect, an accomplished scho. lar, and was well acquainted with foreign languages. He always retained a strong taste for literary pleasures; and his philosophical works are written in a perspicuous and popular style, by which means he has contributed more to the dif fusion of scientific knowledge than any other writer of his time. His three principal works are, "Chemical and Philosophical Researches," "Elements of Chemical Philosophy," and "Elements of Agricul. tural Chemistry," and the two last are excellently adapted for eiementary study.

The results of his investigations and experiments were not pent up in the laboratory or lecture-room where they were made, but by this valuable mode of communication, they have realized, what ought to be the highest aim of science, the improvement of the condition and comforts of every class of his fel. low-creatures. Thus, beautiful theories were illustrated by inventions of immediate utility, as in the safety lamp for mitigating the dangers to which miners are exposed in their labours, and the application of a newly-discovered principle in preserving the life of the adventurous mariner.

Apart from the scientific value of Sir Humphrey's labours and researches, they are pervaded by a tone and temper, and an enthusias. tic love of nature, which are as ad. mirably expressed as their influ.

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ever seen.

Not a few of the most beautiful phenomena of nature are here lucidly explained, yet the pages have none of the varnish of philosophical unbelief.

Sir Humphrey spent nearly the whole of the summer of 1828 in fowling and fishing in the neighbourhood of Laybach; and it has been related by a gentleman who accompanied him on a shooting excursion, that the relative weight of the various parts of each bird, the quantity of digested and undigested food, &c. were carefully noted down by the observant naturalist. It is believed that he was preparing for a large work on natural history.

The great philosopher closed his mortal career at Geneva. He had arrived in that city only the day before, namely, Friday, the 29th of May, 1829; having performed his journey from Rome by easy stages, without feeling any particular inconvenience, and without any cir. cumstances which denoted so near an approach to the payment of the last debt of nature. During the night, however, he was attacked with apoplexy; and he expired at three o'clock on the morning of the 30th.

JOHN JAY.

May 17th, 1829. At Bedford, Westchester county, N. Y. John Jay, formerly Chief Justice of the United States, in the 85th year of his age.

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