As to the claim of priority which has been urged by several philosophers in favour of the French chemists, Davy, in speaking of Gay Lussac's paper, published in the "Annales de Chimie" for July 1814, observes, that "the historical notes attached to it are of a nature not to be passed over without animadversion. M. Gay Lussac states, that he and M. Thénard were the first to advance the hypothesis that chlorine was a simple body; and he quotes M. Ampère as having entertained that opinion before me. On the subject of the originality of the idea of chlorine being a simple body, I have always vindicated the claims of Scheele; but I must assume for myself the labour of having demonstrated its properties and combinations, and of having explained the chemical phenomena it produces; and I am in possession of a letter from M. Ampère, that shows he has no claims of this kind to make."[95]

The question of priority appears to me to be readily settled by a reference to printed documents. Davy published his "Elements of Chemical Philosophy" in 1812, containing a systematic account of his new doctrines concerning the combinations of simple bodies. Chlorine is there placed in the same rank with oxygen, and finally removed from the class of acids. In 1813, M. Thénard published the first volume of his "Traité de Chimie Elémentaire Théorique et Pratique," in which he states the composition of oxymuriatic acid as follows:—"Composition. The oxygenated muriatic gas contains the half of its volume of oxygen gas, not including that which we may suppose in muriatic acid." It was not until the year 1816, that, by a note in his fourth volume, he appears to have at all relaxed in his attachment to the old theory of Lavoisier and Berthollet; and it will presently appear, that at the period above mentioned, iodine had been discovered, and its analogies to chlorine fully established, by the sagacity of Davy.

Having, as I trust, offered an impartial view of his claims to the establishment of the chloridic theory, I shall resume my narrative of those events which more immediately connect themselves with his personal history at this period.

The great fame of Davy, and the high importance of the discoveries which had bestowed it, became a general theme of admiration throughout the scientific circles of Europe, and induced the members of the Dublin Society to invite him to that city, for the purpose of delivering a course of lectures. From the authentic documents which have been placed in my hands, I am enabled to give a particular account of this transaction.

At a meeting of the Dublin Society held on the 3rd of May 1810, the following Resolutions were proposed and unanimously carried, viz.

1. "That it is the wish of the Society to communicate to the Irish public, in the most extended manner consistent with the other engagements of the Society, the knowledge of a Science so intimately connected with the improvement of Agriculture and the Arts, which it is their great object to promote; and that, with this view, it appears to them extremely desirable to obtain the fullest information respecting the recent discoveries made by Mr. Davy, in Electro-chemical science.

2. "Resolved, That application be made to the Royal Society, requesting that they will be pleased to dispense with the engagements of Mr. Davy, so far as to allow the Dublin Society to solicit the favour of his delivering a course of Electro-chemical Lectures in their new Laboratory, as soon as may be convenient after their present course of chemical lectures shall have been completed by their Professor Mr. Higgins.

3. "That the sum of four hundred guineas be appropriated out of the funds of the Society, to be presented to Mr. Davy, as a remuneration for the trouble and expense which they propose he should incur, and as a mark of the importance they attach to the communication which they solicit."

Mr. Leslie Foster having stated to the Dublin Society that the "Farming Society of Ireland" were desirous of availing themselves of this opportunity to apply to Mr. Davy to repeat before them the six lectures on the application of chemistry to agriculture, which he delivered this year (1810) to the Board of Agriculture in England, and that they requested the Dublin Society would accommodate them with the use of their Laboratory for that purpose, all the members of the Dublin Society having free admission to such lectures—

The following Resolutions were passed by the Dublin Society:—

"That in the event of Mr. Davy coming over to Ireland, and consenting to deliver the Course referred to, the Farming Society shall be accommodated with the use of the Laboratory, according to their request.

"That it be referred to the Committee of Economy to consider on what terms, and under what regulations, it may be expedient to issue tickets of admission to the Electro-chemical Course, so as to reimburse to the Society the expenses attendant on the arrangement; and that, in order to give the fullest effect to such regulations, the members of the Society renounce any claim to gratuitous admission to this course."

A letter having been addressed to Mr. Davy by the Secretary of the Society, inviting him to Dublin, for the purpose of delivering courses of lectures, in conformity with the foregoing resolutions, the following answer was received from him:—

On the commencement of the Course, on the 8th of November 1810, three hundred and seventy-one admission tickets had been issued; and the Committee of Chemistry having expressed their opinion to the Society, that the lecture-room would not afford accommodation for a greater number of persons, the Assistant Secretary was directed to limit his tickets to that number. On the 15th instant, however, the number was increased to four hundred, without inconvenience.

At the close of the Course, on the 29th of November, the Dublin Society passed the following Resolutions:—

"Resolved, That the thanks of the Society be communicated to Mr. Davy for the excellent Course of Lectures which, at their request, has been delivered by him in their Laboratory; and to assure him that the views which led the Society to seek for these communications, have been answered even beyond their hopes;—that the manner in which he has unfolded his discoveries has not merely imparted new and valuable information, but further appears to have given a direction of the public mind towards Chemical and Philosophical enquiries, which cannot fail in its consequences to produce the improvement of the Sciences, Arts, and Manufactures in Ireland.

"That the thanks of the Society be communicated to the Royal Society for their ready compliance with our request, in dispensing with the engagements of Mr. Davy, during the last six weeks.

"That Mr. Davy be requested to accept the sum of five hundred guineas from the Society."[96]

The following letter appears, from the date, to have been written about a week before his arrival in Dublin.

In the following year, Davy was again solicited by the Dublin Society to deliver lectures in their laboratory; and at a meeting of the members on the 13th of June 1811, a series of resolutions were passed, by which he was empowered to procure copies of many of the geological sketches referred to in a course of lectures he had delivered on Geology at the Royal Institution; and also to superintend the construction of a large Voltaic battery, for the illustration of the proposed lectures.

In compliance with this request, Davy delivered two distinct courses; one on the Elements of Chemical Philosophy, the other on Geology, for which he received the unanimous thanks of the Society, and as a more substantial testimony of their gratitude, the sum[97] of seven hundred and fifty pounds; the receipt of which Davy acknowledged by the following letter.

Before he quitted Dublin, the Provost and Fellows of Trinity College conferred upon him the honorary degree of LL.D., as an expression of the high admiration which his eminent scientific merits had so universally commanded.

In the month of August, in the same year, his opinion was requested by a committee, as to the best method to be adopted for ventilating the House of Lords; to which circumstance he alludes in the following note to his friend Mr. Pepys.

This undertaking, it must be allowed, was on Davy's part a most complete failure: whether he had miscalculated the diameter and number of the apertures necessary for establishing a current, it is difficult to say, but it was obvious that the stream of fresh air thus introduced was by no means adequate to the demand for it.[98]

The failure, so vexatious to Davy, became to others a fertile source of pleasantry, and numerous epigrams, not exactly of a character to meet the public eye, were very generally circulated, and which, in recording the miscarriage of science, displayed the triumph of wit.

The scientific renown of Davy having attracted the attention of his late Majesty, at that time Prince Regent, he received from his Royal Highness the honour of Knighthood, at a levee held at Carlton House, on Wednesday, the 8th of April 1812; and it may be remarked, that he was the first person on whom that honour had been conferred by the Regent.

On the day following this occurrence, Sir Humphry delivered his farewell lecture before the members of the Royal Institution; for he was on the eve of assuming a new station in society, which induced him to retire from those public situations which he had long held with so much advantage to the world, and with so much honour to himself. How far such a measure was calculated to increase his happiness I shall not enquire; but I am bound to observe, that it was not connected with any desire to abandon the pursuit of science, nor even to relax in his accustomed exertions to promote its interests. It was evident, however, to his friends, that other views of ambition than those presented by achievements in science, had opened upon his mind: the wealth he was about to command might extend the sphere of his usefulness, and exalt him in the scale of society: his feelings became more aristocratic, he discovered charms in rank which had before escaped him, and he no longer viewed Patrician distinction with philosophic indifference.

On the 11th of April 1812, Sir Humphry married Mrs. Apreece, the widow of Shuckburgh Ashby Apreece, Esq. eldest son of Sir Thomas Apreece: this lady was the daughter and heiress of Charles Kerr, of Kelso, Esq. and possessed a very considerable fortune.

Immediately after the celebration of the marriage, Sir Humphry and his bride proceeded to the hospitable mansion of Sir John Sebright, and afterwards made a tour through Scotland, receiving wherever they went the most flattering marks of attention.

During their excursion, Davy wrote various letters to his scientific friends, several of which I shall introduce; but, in order that those to Mr. Children may be understood, it will be necessary that the reader should be made acquainted with a transaction which occurred in the year 1811.

In consequence of some conversation on gunpowder, during which Davy observed that its composition might be greatly improved by rendering it less hygrometric, a proposition was started, that he should join Mr. Children and Mr. Burton in establishing a manufactory for its preparation upon chemical principles. Whether Davy considered himself, in the strict commercial sense, a partner, or merely a chemical adviser, it is perhaps not easy to determine; but it is quite clear that both Mr. Children and Mr. Burton considered him in the former light, although it is an act of justice to those gentlemen to state, that the very moment Davy expressed his disinclination to such an arrangement, they immediately, without the slightest hesitation, released him from all responsibility. This I am enabled to assert, after a most careful investigation of all the correspondence that passed upon the occasion.

On his return to town, after this tour, the following letter was addressed to his friend at Tonbridge:—

CHAPTER IX.

Davy's "Elements of Chemical Philosophy" examined.—His Memoir on some combinations of Phosphorus and Sulphur, &c.—He discovers Hydro-phosphoric gas.—Important Illustrations of the Theory of Definite Proportionals—Bodies precipitated from water are Hydrats.—His letter to Sir Joseph Banks on a new detonating compound.—He is injured in the eye by its explosion.—His second letter on the subject.—His paper on the Substances produced in different chemical processes on Fluor Spar.—His work on Agricultural Chemistry.

The "Elements of Chemical Philosophy," a work to which he has alluded in several of the preceding letters, was published in June 1812. It is dedicated to Lady Davy, to whom he offers it "as a pledge that he shall continue to pursue Science with unabated ardour."

This work, although only a small part of the great labour he proposed to accomplish, must be considered as one of high importance to the cause of science. It has not perhaps announced any discoveries which had not been previously communicated to the Royal Society, but it has brought together his original results, and arranged them in one simple and digested plan—it has given coherence to disjointed facts, and has exhibited their mutual bearings upon each other, and their general relations to previously established truths.

Very shortly after the publication of this first part, it was asserted by a scientific critic that the work could never be completed upon the plan on which it had commenced, which was little less than a system of chemistry, in which all the facts were to be verified by the author: an undertaking far too gigantic for the most intrepid and laborious experimentalist to accomplish. There was too much truth in the remark:—the life of the Author has closed—the work remains unfinished.

Although it bears the title of "Elements," its plan and execution are rather adapted for the adept than the Tyro in science; it has, however, enabled the discoverer to expand several of his opinions with a freedom which is not consistent with the studied compression and elaborate brevity that necessarily characterise the style of a Philosophical Memoir,—and thus far it may have served the more humble labourer.

The first impression which this volume must produce, is that of admiration at the rapid and triumphant progress of Chemistry, during the period of a very few years; while a comparison of this work with others, even of very recent date, will show how much we are indebted for this progress to the unrivalled labours of Davy.

The first part of his projected system, which constitutes the volume under review, extends only to the general laws of chemical changes, and to the primary combinations of undecompounded bodies. It is resolved into seven divisions, upon each of which I propose to offer some remarks.

The First Division embraces the consideration of the three different forms of matter, viz. Solidity, Liquidity, and elastic Fluidity; and that of the active powers on which they depend, and by which they are changed, such as Gravitation, Cohesion, Calorific repulsion, or Heat, and Attractions chemical and electrical;—the laws of which he has expounded in a lucid and masterly manner; although it will be only necessary to quote the following passage, to show that the greatest philosopher may occasionally slide into error. "In solids, the attractive force predominates over the repulsive; in fluids, and in elastic fluids, they may be regarded as in different states of equilibrium; and in ethereal substances, the repulsive must be considered as predominating over and destroying the attractive force." A reviewer has very justly observed, that it is difficult to conceive how so much error and confusion could have been collected, by such an author, into so short a sentence. It is a solecism to say that two forces may exist in different states of equilibrium; besides, it is generally admitted that the repulsive force alone exists in elastic fluids, and that it is only compensated by external pressure, or gravitation.

In treating the subject of Heat, he maintains the same opinion, though in a manner somewhat more subdued, as that which he had formed at the very commencement of his scientific career,[101]—that it is nothing else than motion, and that the laws of Heat are the same as the laws of Motion.

In taking a general view of the subject of Chemical Attraction, there is a remarkable clearness in his enunciation of its several propositions, and a great felicity in the selection of its illustrations. He combats the theory of Berthollet, respecting the influence of mass, with singular success, and confirms the general law, that all bodies combine chemically, in certain definite proportions to be expressed by numbers; so that, if one number be employed to denote the smallest quantity in which a body combines, all other quantities of the same body will be as multiples of this number; and the smallest proportions in which the undecompounded substances enter into union being known, the constitution of the compound they form may be learnt; and the element which unites chemically in the smallest quantity being expressed by unity, all the other elements may be represented by the relations of their quantities to unity. Unfortunately, however, there has existed amongst philosophers a want of agreement as to the unit to which the relative values of the other numbers shall be referred. Mr. Dalton selected Hydrogen as the unit; Davy followed his example, but doubled the weight of oxygen; while Wollaston, Thompson, and Berzelius, have proposed oxygen as the most convenient unit, since that element enters into the greatest number of combinations.

To Dalton is now universally conceded the glory of having established the laws of definite proportions; but in unfolding them, he has employed expressions which involve speculations as to their physical cause, and has thus given to that, which is nothing more than a copious collection of facts, the appearance of a refined theory. It may be perfectly true, as Mr. Dalton supposes, that all bodies are composed of ultimate atoms; but in the present state of our knowledge, we can neither form any idea of the nature of such atoms, nor of the manner in which they may be grouped together. We are therefore indebted to Davy for having, by his early and powerful example, taught the chemist how to disentangle fact from hypothesis, and to investigate the doctrine of proportionals, without any reference to the atomic theory which has been proposed for its explanation.

The Second Division treats of Radiant or Ethereal Matter, and of its effects in producing vision, heat, and chemical changes. It contains some refined speculations respecting the possible conversion of terrestrial bodies into light and heat, and vice versâ.

The Third Division presents us with an account of "Empyreal undecompounded Substances," or those which support combustion; together with that of the compounds which they form with each other. Upon this occasion, Davy has completely rescued us from the trammels of the Anti-phlogistic theory, and has shown that, so far from the process of combustion depending upon the position or transfer of oxygen, it is a general result of the actions of any substances possessed of strong chemical attractions, or different electrical relations, and that it takes place in all cases in which an intense and violent motion can be conceived to be communicated to the corpuscules of bodies, without any regard to the peculiar nature of the substances engaged. The announcement of the general law is followed by a history of the only two undecompounded bodies included under this arrangement, viz. Oxygen, and Chlorine.[102] In naming a class of bodies by their relations to combustion, he distinctly states that he merely intends to signify that the production of heat and light is more characteristic of their actions, than of those of any other substances; and that they are, at the same time, opposed to all other undecompounded substances by their electrical relations, being always in Voltaic combinations attracted to, or elicited from the positive surface; whereas all other known undecompounded substances are separated at the negative surface.

The Fourth Division comprises the history of Undecompounded Inflammables, or Acidiferous Substances, not Metallic, and that of their binary combinations with oxygen and chlorine, or with each other.

The bodies considered under this division, are the following:—Hydrogen, Azote, Sulphur, Phosphorus, and Boracium, or Boron. Under the history of Sulphur, he gives us the true theory of the process by which sulphuric acid is produced by the combustion of that body in mixture with nitre, and which had never before been explained in any chemical work.

The Fifth Division contains the Metals; their primary combinations with other undecompounded bodies, and with each other.

In the order of classification adopted on this occasion, the newly discovered inflammable metals, producing by combustion alkalies, alkaline earths, and earths, commence the series; next come those which produce oxides; and lastly, those which produce acids. Thus are we presented with a chain of gradations of resemblance which may be traced throughout the whole series of metallic bodies.

The Sixth Division comprehends certain bodies (the Fluoric Principle, and the Ammoniacal Amalgam) which present some extraordinary and anomalous results. It is worthy of remark, that, at the period at which this work was written, Davy considered the peculiar acid developed from fluor spar, by the action of sulphuric acid, as a compound of an acid unknown in a separate state, and water; whence he proposed to call it Hydro-fluoric acid,—a term extremely objectionable from its ambiguity, since it would indicate either hydrogen or water as one of its constituents. At the conclusion, however, of this chapter, in consequence of having observed certain phenomena displayed by this gas, when in combination with silica and boracic acid, he for a moment seems to have caught the truth, but it as quickly eluded his grasp, and he dismisses the conjecture which it was his good fortune some years afterwards to verify, viz. that the fluoric acid is a compound of an unknown principle, analogous to chlorine, with hydrogen and water, and that fluor spar is a compound of the same principle with calcium, or the base of lime.

The Seventh Division offers to the chemical enquirer various speculations, as to the probable nature of certain bodies hitherto undecompounded. He observes, that "we know nothing of the true elements belonging to nature; but as far as we can reason from the relations of the properties of matter, that hydrogen is the substance which approaches nearest to what the elements may be supposed to be. It has energetic powers of combination, its parts are highly repulsive of each other, and attractive of the particles of other matter; it enters into combination in a quantity very much smaller than any other substance, and in this respect it is approached by no known body. After hydrogen, oxygen perhaps partakes most of the elementary character: it has a greater energy of attraction, and, with the exception just stated, enters into combination in the smallest proportion."

In conclusion, he hints at the possibility of the same ponderable matter in different electrical states, or in different arrangements, constituting substances chemically different, and he thinks that there are parallel cases in the different states in which bodies are found connected with their different relations to temperature: thus, steam, ice, and water, are the same ponderable matter; and certain quantities of steam and ice mixed together produce ice-cold water.

"That the forms of natural bodies may depend upon different arrangements of the same particles of matter, has been a favourite hypothesis, advanced in the earliest era of physical research, and often supported by the reasonings of the ablest philosophers. This sublime chemical speculation, sanctioned by the authority of Hooke, Newton, and Boscovich, must not be confounded with the ideas advanced by the alchemists, concerning the convertibility of the elements into each other. The possible transmutation of metals has generally been reasoned upon, not as a philosophical research, but as an empirical process. Those who have asserted the actual production of the precious metals, or their decomposition, or who have defended the chimera of the philosopher's stone, have been either impostors, or men deluded by impostors. In this age of rational enquiry, it will be useless to decry the practices of the adepts, or to caution the public against confounding the hypothetical views respecting the elements founded upon distinct analogies, with the dreams of alchemical visionaries, most of whom, as an author of the last century justly observed, professed an art without principles, the beginning of which was deceit, and the end poverty."

On the 18th of June 1812, Davy presented to the Royal Society a paper entitled "On some Combinations of Phosphorus and Sulphur; and on some other subjects of Chemical Inquiry."

By the researches detailed in this Memoir, he accomplished three important objects: he established the existence of some new compounds—furnished additional evidence in support of the doctrine of definite proportions—and ascertained that most of the substances obtained from aqueous solutions by precipitation, are compounds of water, or Hydrats. In the first place, he recognised the formation of two distinct compounds of phosphorus and chlorine: one, solid, white, and crystalline in its appearance; the other, fluid, limpid as water, and volatile. The latter body he found to contain just double as much chlorine as the former.

On experimenting upon this latter body with water, he obtained a crystallized substance which he proposed to call Hydro-phosphorous acid, since it consists of pure phosphorous acid and water. By decomposition in close vessels, it is resolved into phosphoric acid, and a peculiar gas, consisting of one proportional of phosphorus and four of hydrogen, and for which he proposed the term Hydro-phosphorous gas. The reader, no doubt, will be immediately struck with the impropriety of a nomenclature in which the prefix Hydro is made to express water in the former, and hydrogen in the latter instance.

In examining the results of the mutual decomposition of water and the phosphoric compounds of chlorine, Davy remarks, that it is scarcely possible to imagine more perfect demonstrations of the laws of definite combination: no products are formed except the new combinations, (phosphoric acid from the solid, phosphorous acid, from the liquid compound, and in both muriatic acid;) neither oxygen, hydrogen, chlorine, nor phosphorus, is disengaged; and therefore the ratio in which any two of them combine being known, the ratio in which the rest combine, in these cases, may be determined by calculation.

Lastly, he ascertained that most of the substances obtained by precipitation from aqueous solutions are compounds of water: thus zircona, magnesia, and silica, when precipitated and dried at 212°, still contain definite proportions of water; and many of the substances which had been considered as metallic oxides, he found, when obtained from solutions, to agree in this respect; and that their colours and other properties are materially influenced by this combined water.

On the 5th of November 1812, was read before the Royal Society a letter addressed by Davy to Sir Joseph Banks, on the subject of the detonating compound already alluded to in his communications to Mr. Children. He expresses his anxiety to have the circumstances made public as speedily as possible, since experiments upon the substance may be connected with very dangerous results.

He had some time before received information from Paris of a combination having been effected between chlorine and azote, and that it was distinguished by detonating properties; but he was wholly ignorant of the mode by which it had been prepared, and he could not obtain any information upon this point from any of the French journals.

So curious and important a result could not fail to interest him, as he had himself been long engaged in experiments on the action of azote and chlorine, without gaining any decided proofs of their power of combining with each other. It was evident from the notice, that this new body could not be formed in any operations in which heat is concerned; he therefore attempted to combine the elements by presenting them to each other artificially cooled, the azote being in a nascent state. For this purpose he introduced chlorine into a solution of ammonia; a violent action ensued, and minute films of a yellow colour were observed on the surface of the liquor, but they immediately resolved themselves into gas. As he was about to repeat the experiment with some other ammoniacal compounds, Mr. Children reminded him of the circumstance which he had previously communicated to him in a letter, that Mr. James Burton, jun^r, on exposing chlorine to a solution of nitrate of ammonia, had observed the formation of a yellow oil, but which he had not been able to collect. Davy availed himself of the hint, and obtained the substance in question: on examining its properties by the application of heat, the tube in which it was contained was shivered to atoms by its explosion, and he received a severe wound in the transparent cornea, which was followed by inflammation, and disabled him from pursuing his enquiry.

In the following July, however, he communicated in a second letter to Sir Joseph Banks, the continuation of this enquiry, and furnished a full and satisfactory history of the body in question. Having procured it in sufficient quantity, he attempted to effect its analysis by the action of mercury, but a violent detonation occurred, and he was again wounded in the head and hands; fortunately, however, the injury was slight, in consequence of his having taken the precaution to defend his face by a plate of glass attached to a proper cap.

In a subsequent experiment, by using smaller quantities, and recently distilled mercury, he succeeded in obtaining results without any violence of action: the mercury united with the chlorine, and the azote was disengaged; from which he was enabled to conclude that it was composed of four volumes of chlorine and one volume of azote. For this new body Davy suggested the name of Azotane; but I have already observed, that his nomenclature of the compounds of chlorine has never been adopted; the detonating substance is now very properly denominated Chloride of Nitrogen.

Shortly after the publication of this paper, M. Berzelius, in a letter to Professor Gilbert, asserted that "Azotane" is nothing more than dry nitro-muriatic acid, since it dissolves slowly in water, and forms a weak aqua regia. "These few observations," says he, "show clearly that Davy's analysis of this substance is inaccurate, and that he corrected his results in consequence of theoretical views."

This was an imputation upon the philosophical character of Davy, which excited in him no small degree of indignation. In reply he says, "It is difficult to discover what meaning M. Berzelius attaches to the term dry nitro-muriatic acid; and it is wholly unnecessary to refute so unfounded and vague an assertion."

On July 8, 1813, a paper was read by Davy before the Royal Society, entitled "Some Experiments and Observations on the Substances produced in different chemical processes on Fluor Spar."

The views which he formerly entertained with respect to the fluoric acid have been already noticed:[103] in the present paper he renounces his previous opinions, and establishes, by experiments of the most satisfactory character, that the base of fluoric acid is a highly energetic body not hitherto obtained in an insulated form, and the properties peculiar to which are as yet unknown. It appears, however, to belong to the class of negative electrics, and, like oxygen and chlorine, to have a powerful affinity for hydrogen and metallic substances. With hydrogen, it constitutes the peculiar and very powerful acid long known by the name of fluoric acid,—with boron, the fluoboric, and with silicium, the silicated-fluoric, acids. Although this theory had originally suggested itself to the mind of Davy, yet the chemical world is unquestionably indebted to M. Ampère for establishing it; and the English chemist has very justly acknowledged the obligation. "During the period that I was engaged in these investigations," says he, "I received two letters from M. Ampère, of Paris, containing many ingenious and original arguments in favour of the analogy between the muriatic and fluoric compounds. M. Ampère communicated his views to me in the most liberal manner: they were formed in consequence of my ideas on chlorine, and supported by reasonings drawn from the experiments of MM. Gay Lussac and Thénard."

It has been stated that Davy gave his last public lecture on the 9th of April 1812; he however afterwards delivered an occasional lecture to the Managers, on his own discoveries, and did not formally resign his professorship until the next year.

The following record has been extracted from the Journal of the Institution.

"Minutes of the Proceedings of a general Monthly Meeting of the Members of the Royal Institution, held on Monday, April 5, 1813.

"Earl of Winchelsea, President, in the Chair.

"This being the meeting appointed by Article 2. chap. xix. of the bye-laws, for putting in nomination from the chair the professors for the year ensuing, Sir Humphry Davy rose, and begged leave to resign his situation of Professor of Chemistry; but he by no means wished to give up his connection with the Royal Institution, as he should ever be happy to communicate his researches, in the first instance, to the Institution, in the manner he did in the presence of the members last Wednesday, and to do all in his power to promote the interest and success of this Institution.

"Sir H. Davy having retired, Earl Spencer moved, That the thanks of this Meeting be returned to Sir H. Davy, for the inestimable services rendered by him to the Royal Institution. This motion was seconded by the Earl of Darnley, and on being put, was carried unanimously.

"Earl Spencer further moved, That in order more strongly to mark the high sense entertained by this Meeting of the merits of Sir H. Davy, he be elected Honorary Professor of Chemistry; which, on being seconded by the Earl of Darnley, met with unanimous approbation.

"The Chairman having declared the Professorship of Chemistry vacant, put in nomination William Thomas Brande, Esq. F.R.S. as a candidate for that office, with a salary of 200l. per annum.

"On Monday, June 7, 1813, William Thomas Brande, Esq. was unanimously elected."

In March 1813, Davy published his "Elements of Agricultural Chemistry," being the substance of a course of lectures which he had, for ten successive seasons, delivered before the members of the Board of Agriculture, to whom the work is inscribed, as a mark of the author's respect.

This work, which may be considered as the only system of philosophical agriculture ever published in this country, has not only contributed to the advancement of science, but to that for which he has an equal claim upon our gratitude,—the diffusion of a taste amongst the higher classes for its cultivation; for it has been wisely remarked, that not he alone is to be esteemed a benefactor to mankind who makes an useful discovery, but he, also, who can point out an innocent pleasure.

It has been already stated, that Davy became early impressed with the importance of the subject:—that in future life its investigation should have been to him so fertile a source of pleasure, may be readily imagined, when it is remembered with what passionate delight he contemplated the ever varying forms of creation. "I am," said he, "a lover of Nature, with an ungratified imagination, and I shall continue to search for untasted charms—for hidden beauties." In unfolding, then, the secrets of vegetable life, he did but remove the veil from his mistress. From the same poetical feeling sprang his love of angling: it was a pursuit which carried him into the wild and beautiful scenery of Nature, amongst the mountain lakes, and the clear and lovely streams that gush from elevated hills, or make their way through the cavities of calcareous strata.[104] In the early spring, it led him forth upon the fresh turf in the vernal sunshine, to scent the odour of the bank perfumed by the violet, and enamelled with the primrose, while his heart participated in the renovated gladness of Nature.

I had hoped that, amidst the voluminous correspondence of my late friend Mr. Arthur Young, some important letters might have been found from Davy on agricultural subjects; but the communications which took place between them were generally in conversation, and I have therefore only been able to procure two letters, which I shall here insert: the first will show that, during his tours, his attention was alive to the practices of husbandry; and the second will prove that he had once seriously contemplated the labour of writing the agricultural history of his native county.