BIOGRAPHY OF SIR IIUMPI-IRY DAVY, CONTINUED. CHAPTER THIRD.
IF the observations we ventured to offer, in a late number, upon the style and character of DAVY'S lectures at the Royal Institution, should have failed in justifying the propriety of that florid diction which dis- tinguished them, we have a satisfaction in feeling, that, superficial as must be our review of his labours, it will at least show, that this illustrious philosopher could never have required, for his own distinc- tion, thee aid of such foreign ornament. A path of flowers may be very agreeable to those who labour up the ascent, but the glory of the mountain consists alone in its immensity. As the advantages afforded by the history of any great scientific discovery, consist as munch in exhibiting, step by step, the intellectual operations by which it was accomplished, as in detailing its nature, or in examining its relations with previously-established truths, so must it prove highly interesting to lix the period at which DAVY'S mind was first directed to the subject of Voltaic Electricity. In ro- ferring to the " Additional Observations," appended to his " Chemical Researches," we shall find that he had no sooner heard of the curious experiments of VOLTA upon the effects produced by the contact of two inorganic bodies, than, with his characteristic quickness of percep- tion, lie proceeded to inquire whether the fact, previously noticed by himself, of the conversion of Nitrous Gas into Nitrous Oxide by ex- posure to wetted zinc, might not depend upon galvanic action. It was the early habit of his mind, not only to originate new inquiries, but without delay to examine the novel results of other philosophers ; and in numerous instances it would seem that he only required to con- firm their accuracy, before he succeeded in rendering the application of them subservient to further discovery.
In examining the numerous memoirs which he presented to the Royal Society, we cannot preserve their chronological succession, without losing sight of that fine intellectual thread by which the mind of their author was conducted through the intricate labyrinths of Nature : we shall therefore, in the first place, present to the reader a brief analysis of these several memoirs, in which the laws of Electricity have been so profoundly investigated, and its chemical agency so suc- cessfully and beautifully displayed in the separation of the elements of hitherto undecompounded bodies. It is impossible to enter upon the subject of Galvanic Electricity, without recurring to the circum- stance which first demonstrated the existence of such an energy, and to the sanguine expectations which it excited. It was natural to believe, when we witnessed the powerful contraction of a muscular fibre by the contact of a metal, that the nature and operation of the mysterious pourer of vital irritability would be at length developed by a new train of research. It is a curious fact, that an experiment so full of promise to the physiologist should hitherto have failed in afford-
ing him any assistance the chemist, to whom it did not appear lo otter one sin:le point of interest, has derived from it a new and im- portant histrument of research, which has already, under the guidance of DAVY, multiplied discoveries with such rapidity, and to such an ex- tent, that it is impossible to anticipate the limits of its power. We have here, then, another striking instance of a great effect produced by means apparently insignificant. Who could have imagined it pos- sible that the spasmodic action produced in the limb of a frog, by the accidental contact of a pair of scissars, should have been the means of chaneing the whole system of chemistry—of discovering sub- stances whose very existence was never suspected—of elucidating the theory of Volcanoes and Earthquakes, and, may we not add, of lead- ing the way to a knowiedee of the laws of Terrestrial Magnetism !- Such an unexpected extension of an apparently useless fact, should dispose us to entertain a kinder regard for the labours of one another, and teach us to judge with diffidence of the results of science. A dis- covery which may appear incapable of application to-day, may be our glory to-morrow, and even wield the destiny of nations. The Conic Sections of A eoer.oxi us Peeoseus remained useless for two thousand years : who could have supposed that, after the lapse of twentycen- turies, they would have formed the basis of Astronomy ; a science giving to navigation safety, guiding the pilot n11.01:2;11 unknown seas, and tracing for him in the heavens an unerring- path to his native shores !—Wc beg the indulgence of the reader for this digression. The subject is one which has long engaged the attention of the writer; and he hopes, at some future period, to fulfil the wishes of the accomplished author of Lettres n Sophie: " Tehistoire des grand efiets par les petits causes ferait un lirre leen curieux."
The first memoir presented to the Royal Society by DAVY, was read on the 18th of June 1801 ; and is entitle,1 " An Account of sonic Galranic Combinations, formed by the arrangement of Single Metallic Plates and Fluids., analogous to the new Galvanic Apparatus
of l'qta ; b11 Mr. Humphry Davy, Lecturer on Chemistry in the Ronal Institution: Communicated by Benjamin, Count of Rumford, V.P.R.S.- In order to appreciate the value of this paper, it must be
remembered, that the agencies of two metals in exciting galvanic phamomena were at that time supposed to be directly connected with the different powers of such metals to conduct electricity. DAVY was the first philosopher who corrected this error, and, in the paper before us, showed that the evolution of galvanic energy was connected with chemical action ; an inference which he deduced from some experi- ments, by which he found that an accumulation of galvanic influence (exactly sinflar to that in the common pile, where two metals are used) might be produced by the arrangement of single metals, with
different strata of fluids. This theory he established by a great va-
riety of experiments, and showed that the alternation of two metals with fluids was no further necessary to the prdduction of accumulated galvanic influence, than as it furnished two conducting surfaces of dif- ferent degrees of oxidabilit# ; and that this production would take place, if single metallic plates were connected together by different fluids, in such a manner that one of their surfaces only should undergo oxidation, the arrangement being regular. He moreover ascertained that many of these arrangements could be made active, not only when oxidation, but likewise when other chemical changes were going on in some of their parts. Here then appeared the dawn of the Etectro-chemical theory. The main fact stated in Davy's paper, namely, the relation between the energy of the pile and the oxidation of one of its metals by Ile interposed thud, was readily admitted ; but a question arose, whether the oxidation, instead of being the primary cause, night not be the effiTt of the electricity, set in motion by the contact of metals, endowed with ditent conducting powers. Upon this occasion, with an aiaciiey melees:ending with the importance of the subject, Dr. WOLLASTON antxtited in the arena, and at the meet- ing succeeding that at which D'eve's paper was read, related to the Society a series of ceperiments, which fully confirmed the views of DAVY, and set the question for ever at rest. We are particularly anxious to direct our readers' attention to this fact : it illustrates one of the Most prominent features in the scientific character of Wormas- emv—the quickness of his perception, the solidity of his judgment, and above all, the liberality and candour with which he lent his pow- erful aid for the promotion and advantage of a rival philosopher.
An interval of nearly five years now elapsed before DAver threw any further light upon this branch of science ; but his energies had not slumbered—he had been engaged in experiments of the most arduous and complicated description ; and in presenting their results, he un- folded the mysteries of voltaic action, and as far as its theory goes, might almost be said to have perfected our knowledge of the galvanic pile. This grand display of scientific light burst upon Europe like a meteor, throwing its radiance into the darkest recesses, and opening to the view of the philosopher new and unexpected regions. The me- moir in which these discoveries were announced constituted the Bakerian Lecture ; and was read before the Royal Society on the 20th November 1806. We shall endeavour to offer as popular a review of its contents as the abstruse nature of the subject will allow. It had been observed during some of the earliest chemical experiments with the voltaic pile, that when the purest water was submitted to the ac tion of a current of electricity, acid and alkaline matter was separated at the opposite electrified surfaces. A fact so extraordinary neces- sarily excited various conjectures ; and many believed that the bodies were actually generated by the action of the pile. DAVY, however, soon negatived so unphilosophical a conclusion, and showed that they merely arose from the decomposition of the materials employed : he found, for instance, that the glass vessel, at its point of contact with the wire, was corroded ; a, fact which sufficiently explained the source of the alkali ; while the animal or vegetable materials, employed as conductors, might be readily supposed to furnish the acid. He ac- cordingly proceeded to work with cups of agate, and, at the sugges- tion of Dr. WOLLASTON, whom we again hail as a Mentor, he formed the connecting parts of well-washed asbestos. Thus then was every source of fallacy connected with the apparatus removed ; but still the same production of saline matter appeared—what could be its origin ? He repeated the experiments in cups of gold, and examined the purity of his water by evaporation in vessels of silver. At length he succeeded in recognizing the source of this matter : it was of foreign origin— partly derived from the contents of the water, and partly from new combinations of gaseous matter. This was curious, but after all, a discovery in itself of insignificant value, when compared with those which immediately flowed from it. The acid and alkaline matter then produced, it has been already stated, collected in the water round opposite poles ; the former always appearing at the positively electrified, the latter at the negatively electrified surface. Was this a universal law ? It was necessary to decide this question by more extended inquiries. The first series of experiments which he instituted for this purpose, embraced the decomposition of solid bodies, in- soluble, or difficultly soluble in water. From the effects of the electrical agency on glass, already mentioned, he very reasonably expected that various earthy compounds might tlins undergo changes under similar circumstances ; and his conclusion was just. From Sulphate of Lime he obtained sulphuric acid in the positive, and a solution of lime in the negative cup. These experiments were ex- tended to a great variety of other compounds, such as Snlphate of Strontia, Fluate of Lime, Sulphate qf Baryta, &c. and with parallel results. Having thus far established the general law, he proceeded to inquire into the mode and circumstances under which these constituent parts were transferred to their respective poles ; and he discovered, first, that acid and alkaline bodies, (luring the time of their electrical transfer, would pass through water containing vegetable colours, with- out affecting them, or combining with them ; and, secondly, that such bodies would even pass through chemical menstrua having stronger attractions for them, thereby showing that the same power which destroyed elective affinity in the vicinity of the metallic points, would likewise destroy or suspend its operation, throughout the whole of its circuit. Thus, proceeding step by step, with philosophic caution and unwearied perseverance, did he develope all the particular pimp- nomena and details of his subject ; his genius then took flight, and with an eagle's eye caught the plan of the whole. A new science was created; and so important and extensive were the applications of its principles in producing chemical composition and decomposition, that it justly derived the name of ELECTRO-CITEMISTRY. Its illustrious author, reasoning upon the pleenomena it displayed, arrived at the plausible conclusion, that the power of electrical attraction and repul- sion must he identical with chemical affinity. If this be true, we at once obtain a solution of the problem, and can explain the action of the electric fluid in disuniting the elements of chemical combinations ; for it is evident, that if two bodies be held together by virtue of their electrical states, by changing their electricity we shall disunite them. In this view of the subject, every substance, it is supposed, has its own inherent electricity, some being positive, others nwalive. When, therefore, bodies in such opposite states are eresented to each other, they will combine.
We will venture, with perfect confidence, to rest the fame of DAVY as a philosopher upon this single memoir. It is true that the dis- coveries immediately resulting from the application of the principles therein contained are more dazzling to ordinary minds, but in our judgment far less glorious. Does not Sir ISAAC NEWTON deSel-VC greater fame for his invention of Fluxions than for the calculations performed by the application of them ? We do not hesitate in com- paring these great philosophers, since each has enlightened us with discoveries alike effected by means of his own creation. Not.oniy did both unlock the choicest casket of Nature, but they had the superior merit of planning and constructing the key.
In our next number, we shall proceed to the consideration of DAVY'S Bakerian Lecture of 1807 ; in which is announced the discovery of the metallic basis of the Alkalies and Earths, obtained through the agency of Electricity, directed in accordance with the laws which he had esta- blished in his lecture of the preceding year.
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