Page images
PDF
EPUB

deed, it is somewhat remarkable, that throughout the whole book, we are never once introduced into the polite circles about court, The author might have managed this very easily for Don Manuel ; and in a work professing to give an account of the manners of a nation, it is a very important omission. The picture he gives us of a fop, seems to be drawn entirely from his own fancy, and is a complete caricature; our readers may judge of the whole, from the following sketch of their intellectual endowments.

Their souls might be lodged in a nutshell without incommoding the maggot who previously tenanted it ; and if the whole stock of their ideas were transferred to the maggot, they would not be sufficient to confuse his own. It is impossible to describe them, because no idea can be formed of infinite littleness; you might as reasonably attempt to dilo Icet a bubble, or to bottle moonshine, as to inveftigate their characters; they prove satisfactorily the existence of a vacuum : the sum total of their being is composed of negative quantities.' NI. 302, 303..

There is a great deal of this flippant, affected style of writing in these letters, and many abortive attempts at wit and satire, which is often directed to subjects far above the author's reach, as in the following instance.

" At present the Englith philosophers and politicians, both male and female, are in a state of great alarm. It has been discovered that the world is over peopled, and that it always must be so, from an error in the consticution of nature ;-that the law which says “ Increase and multiply,” was given without sufficient consideration ;---in short, that He who made the world does not know how to manage it properly, and therefore there are serious thonghis of requesting the English parliament to take the business out of his hands.' lll. 316, 317.

This, to say the least of it, is very pitiful impertinence. In the journey to Falmouth there is nothing that particularly attracts our attention. We have short descriptions of Bath and Bristol, interspersed with a variety of anecdotes in his usual taste, from which we shall make no further extracts, as we believe our readers wi}l think we have been already sufficiently liberal.

Upon the whole, though we cannot complain of Don Manuel for being a dull or tedious companion, we part from him without any feeling of regret or respect. He is very conceited, shallow, and dogmatical; full of exaggerations and discontents, and quite destitute of that tone of good company which can make trilling graceful, and presumption inoffensive. His pleasantries and 2necdotes, are such as might be collected in the traveller's apartment of any well frequented inn; and the greater part of his reasonings are evidently the productions of a micid accustomed either to indulge in solitary and unchecked speculation, or to predominate in a society of still humbler qualifications. There is a good deal of cleverness displayed in the work, and for the most part a tone of right feeling ; but the petulance of the author's mannet entirely destroys his respectability; and the value he evidently sets on the odd and minute observations it contains, makes them appear, to an indifferent reader, still more insignificant perhaps than they really are. No one, we conceive, who reads the book, can for a moment suppose it to be the work of a foreigner. We have seldom seen a character, indeed, worse dressed or supported; .and no one is in any danger of being imposed on by the Spanish title, who would not believe in the reality of ghosts at the playhouse, or vestal virgins at the masquerade. We have not thought it nécessary to produce any proofs of a deception which we cannot imagine intended to be effectual. The whole strain of the sentiment and diction is manifestly English; and the author cannot even refrain from indulging himself in a variety of puns and verbal pleasantries, to which it would not be easy to find an equivalent in the original Spanish.'

tone tuted

Art, VIII. The Bakerian Lecture on some Chemical Agencies of

Electricity. By Humphry Davy, Esq. Sec. R. S. M. R. I. A. Prof. Chem. R. J.

(From the Phil. Trans. for 1807. Part I.)

IT is no small proof of Mr Davy's natural talents and strength

of mind, that they have escaped unimpaired from the enervating influence of the Royal Institution; and indeed grown prodigiously in that thick medium of fashionable philosophy. The paper now before us is by far the most important addition which his labours have yet made to the stock of physical science; it contains one or two discoveries of considerable intrinsic value, and opens a field of research almost new and altogether unbounded. He has, since the publication of it, if we are not misinformed, begun to enter upon this field, and has been rewarded for his toil and ingenuity, by the most brilliant discovery which has adorned the annals of chemistry from the foundation of the new theory to the present day. As soon as his own account of these experiments is given to the world, we shall call the attention of our readers to it. In the mean time, it will both prepare the way for examining that discovery, and divert somewhat of the impatience which our readers, in common with ourselves, cannot avoid feeling, until the details of it are made known, if we endeavour to make them acquainted with the substance and merits of the present communication. The first set of experiments described in this paper was insti

tuted with a view to ascertain, with greater accuracy than had hi. therto been attained, the squrces of the acid and alkali observed to be produced when distilled water is submitted to the action of the galvanic fluid: Mr Davy, with several of our best chemists, had ascribed this phenomenon to certain impurities in the water, and ingredients in the composition of the glass and the conductors; which others of inferior note had denied. The ques. tion is now discussed in a very satisfactory manner; and, we may say, set completely at rest. We cannot pretend to follow the train of the experiments, but shall endeavour to give a general outline of them.

Two cups, tubes, cones, or other vessels capable of containing water, and made of various substances successively, were connected together by films of pure amianthus, and connected with the positive and negative ends respectively of the pile of Volta, by means of platina wires. The pile was a strong one, generally consisting of 100 or 150 plates of zinc and copper, six inches square, and moistened with alum, or alum and diluted sulphuric acid. The water in the vessels being exposed to the action of this pile, after a certain time became acid in the positive vessel, and alkaline in the negative. When the vessels were of glass, the alkali was much greater in quantity (about twenty times) than when they were of agate. The same process, too, in the latter case, being repeatedly tried with the same cups, though the acid continued to be abundaptly produced on the positive side, the quantity of the alkali was diminished greatly in the negative tube. Still, however, some was produced; and, after several repetitions of the process, the quantity continued stationary, being extremely small, though perceptible. It was natural, therefore, to suspect the water of having some alkaline impurities. The process was now repeated with small vessels of . pure gold, and in ten minutes the negative vessel had attained its maximum of alkali; for the action being continued for fourteen hours, while the water in the positive vessel became constantly more acid, the water in the negative side was not sensibly changed; and after three days more had elapsed, the acid became still stronger, the alkali remaining as before. By evaporating a quart of the same distilled water, seven tenths of a grain of solid matter were obtained, consisting of nitrate of sada, and nitrate of lead, the latter apparently from the still. The galvanic experiment was then repeated in agate vessels much used, and in gold vessels," with the water thus purified by evaporation; and no alkali was produced in the negative vessel. The substances of the vesseis being varied, different acids and alkalis were produced in the opposite sides of the circuit. Thus wax tubes gave for the acid matter, a mixture of sulphuric, muriatic, and nitric acids;

for

for the alkaline, soda and potash; and Carrara marble gave limewater continually, and at first a mixture of limewater and fixed alkali. But in all the experiments nitrous acid was produced in the positive side, constantly to the end of the process; and a small quantity of ammonia was regularly formed in the negative side, at the beginning of the process. For the purpose of rendering still more indubitable the inference to which all these experiments point, the process with purified water in golden vessels was performed during many hours in the receiver of an air pump, exhausted sixty-four times; and then in a receiver filled with hydrogen gas. In neither case was there the smallest particle of alkali produced; in the former, there was a most minute portion of acid ; in the latter, none whatever..

Nothing, certainly, can be more satisfactory than the result which all these most elaborate experiments concur in pointing out; and we may conclude with perfect confidence, that wherever an acid, or an alkaline matter is produced by subjecting water to the action of the galvanic fluid, the latter of these bodies is evolved, either from the impurities of the water, or from the materials of the vessels; and the former from the vessels, or the impurities of the water, or the union of one of the constituent parts of the water with the azote which it has absorbed from the air. And the only case in which an alkali is really formed, is where ammonia results from the union of the hydrogen of the water with the azote dissolved in it. .

There is one fact common to every one of these experiments, which indeed had attracted some attention from the first application of galvanism to chemical inquiries, but was never placed in so striking and steady a light as by the processes just now analyzed. We allude to the uniform and exclusive appearance of the alkali, where any was evolved, at the negative surface; and of the acid at the positive surface. Mr Davy's first set of experiments, being made with a view to explain what effects certain impurities and extraneous substances produced on water in the galvanic circuit, had no immediate or direct reference to the action of the huid on these substances, which were, indeed, accidental to the different processes. But the observation of the fact now mentioned, naturally led him to examine more fully the laws of this action, by exposing to it a variety of known substances. He began with a set of experiments upon insoluble bodies, containing large quantities of acid and alkaline matter, repeating, in fact, the process so often referred to, with two cups made successively of sulphates of lime, strontites, and barytes, and fluate of lime, connected together either by pieces of the same earths, or by asbestus. The water in the positive cup, was always, as the process went on, mixed with more and more sulphuric or fluoric acid; and in the

negative

negative cup, it was uniformly converted into limewater, or had a mixture of strontites, or a crust of barytes, carbonated by the contact of the atmosphere. Insoluble substances, containing very minute portions of acid and alkali, were next exposed to a similar process; and the negative side uniformly extracted the alkali, the positive side the acid, be the quantities ever so small. Soluble bodies were then examined in like manner, being subjected to the galvanic fluid in agate cups, and dissolved in pure water. The separation here went on much more rapidly, but it followed the same rules. The negative cup contained a solution of alkali, or a deposite of earth or metallic crystals, according to the compound neutral employed; the positive cup uniformly contained a great excess of acid ; a muriatic salt gave oxymuriatic acid in the positive cup. The stronger the solution exposed in these experiments, the, quicker was the change produced; but the smallest portion of acid and alkali was always detected; and the separation, at the end of the process, was as complete as at first. • Two foreign chemists of reputation, Messrs Hisinger and Berselius, had made an experiment, in which muriate of lime being exposed in the positive side of a siphon, and pure water in the negative, the action of the galvanic fluid made lime appear in the water: so extraordinary a discovery, merited every degree of attention. Mr Davy immediately pursued it, upon the plan of his former experiments. His first inquiry was into the manner of the passage here remarked, through a menstruum not chemically attracting the substance which passed over. An agate cup, for example, filled with water, was connected with a cup of sulphate of lime, by moistened asbestus: if the former was positively electrified, acid soon came over ; if negatively, lime came over. Metals and metallic oxides passed over to the negative cup, like alkalis and alkaline earths; and, in one beautiful experiment, where nitrate of silver was placed in the positive side, the amianthus between the cups appeared covered with a thin silver film. The transference went on slower, in proportion to the body of water through which it was performed: when the wires were only an inch asunder, sulphuric acid came over from sulphate of potash in five minutes; nor was contact with either electrified surface, necessary in these experiments. A vessel of solution of muriate of potash, being connected by amianthus with two glass tubes filled with water, the one negatively, the other positively electrified; by degrees, the alkali went over into the former, and the acid into the latter. But one of the most singular parts of this process, is, that the acid and the alkali, in passing from one vessel to another, through any intermediate body of water, or over the surface of the amianthus, do not change the vegetable colours in their way, except in so far as they come in contact with them at the positive VOL. XI. NO. 22. Cc

and

« PreviousContinue »