until I shall have satisfactorily explained those anomalies by fresh experiments. On account of this scepticism, and for other reasons, I shall in future use the common nomenclature; excepting that, as my discoveries concerning the gaseous oxide would render it highly improper to call a principle, which in one of its combinations is capable of being absorbed by venous blood, and of increasing the powers of life, azote,-I shall name it, with Dr. Pearson, Chaptal, and others, NITROGENE; and the gaseous oxide of azote I shall call NITROUS OXIDE."

The same feeling is expressed at the conclusion of his Third Research."It would be easy to form theories referring the action of blood impregnated with nitrous oxide, to its power of supplying the nervous and muscular fibre with such proportions of condensed nitrogen, oxygen, light, or ethereal fluid, as enabled them more rapidly to pass through those changes which constitute their life; but we are unacquainted with the composition of dead organized matter; and new instruments of experiment, and new modes of research, must be found, before we can ascertain even our capabilities of discovering the laws of life."

There is one circumstance connected with the views entertained in this work which must not be passed over without notice. In several passages he advocates the theory of the atmosphere being a chemical compound of oxygen and nitrogen; whereas, in later years, he was amongst the first to insist upon its being simply a mechanical mixture of these gases.

In consequence of the highly deleterious experiments which have been already described, and of the constant labours of the laboratory, and the repeated inhalation of acid and other vapours, his health began visibly to decline, and he retired into Cornwall, where he informs us that "the associations of ideas and feelings, common exercise, a pure atmosphere, luxurious diet, and a moderate indulgence in wine, in the course of a month restored him to health and vigour."

I find an allusion to this visit in a letter from his sister. "He had," she says, "written to his mother of his intention to visit her, but before the post had quitted Bristol, he was already on his way to Penzance, and would have reached it before his letter, had not his aunt, on whom he called in the neighbouring town of Marazion, struck with his appearance of ill health, insisted on his remaining there till the next day, lest his mother should be doubly alarmed at his unexpected visit, and altered looks." Miss Davy adds, "This

one fact will serve, at the same time, to illustrate his attachment to home, and the impetuosity of his mind, which never rested till the object he proposed was accomplished."

The following letter is inserted in this place, for the purpose of fixing the period at which he first ascertained those new facts in Voltaic electricity, which formed the basis of a future communication to the Royal Society, and which may be said to have paved the way to his grand discoveries in that branch of science; the dawning of that glorious day, which we shall presently view in all its splendour and glory.

There is, moreover, something extremely interesting in receiving from himself a simple and unadorned statement of results, as they successively presented themselves to his observation-" Truths plucked as they are growing, and delivered to you before their dew is brushed off.”

TO DAVIES GIDDY, ESQ.

Pneumatic Institution, October 20, 1800.

BE assured, my respected friend, that your last letter, though short, was highly gratifying to me. At the moment it was brought to me, I was about to depart with King and Danvers on an excursion to the banks of the Wye. Our design was to see Tintern Abbey by moonlight, and it was perfectly accomplished.

After viewing for three hours all the varieties of light and shade, which a bright full moon and a blue sky could exhibit in this beautiful ruin; and after wandering for three days among the many-coloured woods and rocks surrounding the river, between Monmouth and Chepstow, we arrived on the fourth day at Bristol, having to balance against the pleasure of the tour, the fatigue of a stormy voyage down the Wye, across the mouth of the Severn, and the Avon.

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On analysing, after our return, specimens of the air collected from Monmouth, from the woods on the banks of the Wye, and from the mouth of the Severn, there was no perceptible difference; they were all of similar composition to the air in the middle of Bristol, that is, they contained about twentytwo per cent. of oxygen. The air from the bladders of some sea-weed, apparently just cast on shore, at the Old Passage, likewise gave the same results so that, comparing these experiments with those made by Cavendish, Ber

thollet, &c. and by myself on other occasions, at different temperatures, in different weather, and with different winds, I am almost convinced that the whole of the lower stratum of the atmosphere is of uniform composition.

No test can be more fallacious and imperfect than nitrous gas, on account of the different composition of nitrous acid, formed in the different manipulations of eudiometrical experiments.

The eudiometer that I have lately employed gives, in a few minutes, the proportions of oxygen without correction.

In pursuing experiments on galvanism, during the last two months, I have met with unexpected and unhoped-for success. Some of the new facts on this subject promise to afford instruments capable of destroying the mysterious veil which Nature has thrown over the operations and properties of ethereal fluids.

Galvanism I have found, by numerous experiments, to be a process purely chemical, and to depend wholly on the oxidation of metallic surfaces, having different degrees of electric conducting power.

Zinc is incapable of decomposing pure water; and if the zinc plates be kept moist with pure water, the galvanic pile does not act; but zinc is capable of oxidating itself when placed in contact with water, holding in solution either oxygen, atmospheric air, or nitrous or muriatic acid, &c.: and under such circumstances, the galvanic phenomena are produced, and their intensity is in proportion to the rapidity with which the zinc is oxidated.

The galvanic pile only acts for a few minutes, when introduced into hydrogen, nitrogen, or hydro-carbonate; that is, only as long as the water between its plates holds some oxygen in solution; immerse it for a few moments in water containing air, and it acts again.

It acts very vividly in oxygen gas, and less so in the atmosphere. When its plates are moistened by marine acid, its action is very powerful, but infinitely more so when nitrous acid is employed. Five plates with nitrous acid gave sparks equal to those of the common pile. From twenty plates the shock was insupportable.

I had almost forgotten to mention, that charcoal is a good galvanic exciter, and decomposes water, like the metals, in the pile; but I must stop, without being able to expatiate on the connection which is now obvious between galvanism and some of the phenomena of organic motion. I never consider the subject without having forcibly impressed upon my imagination your

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observations on the science of the ethereal fluids, and I cannot help flattering myself that this age will see your predictions verified. I remain with sincere respect and affection, Yours,

HUMPHRY DAVY.

That a work, of the character of the "RESEARCHES," replete with ingenious novelty, and rich in chemical discovery, proceeding from the pen of so young a man, should have excited very general admiration in the philosophic world, is a circumstance that cannot surprise us; but in a majority of cases, precocious merit enjoys only an ephemeral popularity; the sensations it excites are too vivid to be permanent, and the individual sinks into an obscurity rendered ten times more profound by the brilliancy of the flash which preceded it; but every event of Davy's life would appear as if created, and directed for his welfare, by some presiding genius, whose activity in throwing opportunities in his way was rivalled only by the address with which he converted them to his advantage. Fortune and talent, then, were both equally engaged in accomplishing the elevation of Davy, and it is probable that eminent success generally requires a combination of these elements for its production, and that the maxim of Plautus is therefore as remote from truth as that of Theophrastus, the one assigning all to fortune, the other all to talent.

The experiments to which allusions have been frequently made during the present chapter, favourably as they were received, might have shared the fate of many other discoveries which did not admit of an immediate and obvious application to the purposes of common life; for statistical value is a necessary passport to popular favour. Fortunately, however, for Davy, before the vivid impression produced by his new work had lost the glow of novelty, Count Rumford was anxiously seeking for some rising philosopher, who might contribute his energies towards the support, and farther increase, of the chemical fame of the recently established “INSTITUTION OF GREAT BRITAIN.”

It is not surprising that his attention should have been readily directed to one whose genius had been so lately displayed, and whose views regarding Caloric † were in such exact conformity with his own opinions.

On conversing with Mr. Gilbert on the above passage, I understand that it is an allusion to his opinion, that the discovery of Galvanic power would ultimately lead to a knowledge of the nature of light and heat.

+ Mr. Gilbert no sooner discovered the tendency of Davy's opinions, respecting the immateriality of Caloric, than he urged him to communicate them to Count Rumford, but he considered himself

As the philosophical public must feel a lively interest in every incident connected with a transaction so important to the interests of science, as that by which Davy was placed in the chemical chair of the Institution, I am fortunate in being able, through the kindness of his two friends, Mr. Thomson and Mr. Underwood, to present a clear and satisfactory statement of all its circumstances and details.

pledged to Dr. Beddoes, and his Essays were accordingly printed in the West Country Contributions. Count Rumford, it may be observed, maintained that Caloric, like Phlogiston, was merely a creature of the chemist's imagination, and had no real existence. He considered heat as nothing more than the motions of the constituent particles of bodies amongst themselves,-an hypothesis which has no claims to novelty; being, perhaps, one of the most ancient on record.-See his paper on Heat, Phil. Trans. for 1804.