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This laft process furnishes an eafy teft by which a perfon may at once discover whether quickfilver be pure or not: for if it be impure, the water becomes opaque almost immediately after the agitation commences; which is by no means the case when pure quickfilver is employed.
The rationale of thefe proceffes, at least with refpect to the principal circumftances attending them, is pretty evident. They fhew in a clear and fingular manner the great power of the air in reducing certain metals into the state of a calx, even in the common temperature of the atmosphere. By their previous dif folution in the mercury, they are in fact brought into a fluid ftate, or, as it were, into a ftate of fufion; and by the agitation they are broke into extremely small globules: fo that a large quantity of furface, which is every inftant changing, is fucceffively expofed to the action of the air included in the vial with them. Under thefe circumstances they readily part with their phlogiston to the air, and receive from it, in return, that portion of fixed air, or other principles, to which they, in part, owe their calciform ftate; and they accordingly acquire, just as happens in calcinations by fire, a weight greater than that of the metal originally employed; as the Author found, on weighing the imperfect calces (for they are far from being pure) produced in this mode of experimenting.
It is much more difficult to give a fatisfactory explanation of the effects related in the fucceeding fet of experiments, made with pure mercury. On its being agitated in pure water, without accefs of air, in a vial, one-fourth of which was occupied by the quickfilver, and the remaining space filled up with water; the water becomes opaque, by means of innumerable particles of a black matter fufpended in it. Suffering this matter to subfide, and pouring off the clear water, the fame phenomena occur, on agitating the mercury with fresh water. If the water that had been poured off is again ufed with the fame mercury, the black powder is produced much more readily, or in greater quantity, than when it was employed the first time, or than when pure water is used.
The moft fingular circumftance relating to the black powder, into which mercury is thus converted, by agitating it with water, without the prefence of air, is, that on the total evaporation of the water, the powder is, in an inftant, converted into running mercury. The turbid water likewife is rendered tranfparent, on heating it: nor can this powder be produced, if hot water is employed in the experiment.
This black mercurial powder differs, with refpect to its state or conftitution, in a very effential circumftance, from that above mentioned, obtained in the agitation of impure mercury. This laft required air, and a repeated renovation of air, for its proGg 4 duction,
duction, and for the reducing it to the ftate of a calx: whereas the former is not only produced without the intervention of air, but on being immediately, or directly, expofed to it, on its being freed from moisture, it inftantly affumes its former metallic ftate. On viewing a little of the moift powder with a microfcope, the change is almoft inftantaneous, when it becomes dry. In this fmall quantity, the particles of the black powder are inftantly converted into white and polished globules.
Further, in the former procefs, the lead appears evidently to have loft a great part of its phlogifton. On the contrary, in the black mercurial powder, the quickfilver feems to have affumed that form, in confequence of its having acquired phlogiston; and that, too, in a greater proportion than is neceffary to its metallic ftate: though it is certainly difficult to determine whence it has acquired it.-That it has, however, got an overcharge of that principle, feems to be fully afcertained by the following experiment:
I took,' fays the Author, a glafs tube, about 18 inches long, and half an inch wide, and pouring into it a quantity of the water and black powder of mercury, turned it every way till it had got a black coating in all places. I then inverted it, and placed it in a cup of water near the fire; but not so near as to convert the water within the tube into steam, and thereby expel too much of the air. In this fituation I perceived, after fome time, that the quickfilver was revivified; all the tube to which the heat had reached having now got a white coating, and having the appearance of a looking-glafs. I then examined the air in the infide of the tube, and found it to be very fufficiently phlogisticated. For one measure of it, and one of nitrous air, occupied the space of 1.66 measures, notwithstanding a confiderable part of the tube had not been so much heated as to have had all the mercury on it revivified.'- We should obferve that it appears, from a preceding experiment, that fimilar proportions of common and nitrous air occupied the space. only of 1.27 measures; fo that the air in the tube must have been confiderably phlogisticated, on the black powder's returning to a metallic ftate. The Author accordingly is led to confider this powder as mercury fuper-phlogisticated, or which has acquired more phlogifton than is neceflary to its state of white running mercury.
It is difficult to conceive whence the mercury can have acquired this phlogifton, from mere agitation in the pureft water. This difficulty is fo great, that, had not the Author fhewn that the air was phlogifticated, on the reduction of this powder into mercury, we fhould have fuppofed either that a part of the quickfilver had acquired this blacknefs merely by the extreme fubdivifion of fome of its particles; or that the powder was a
new and fingular combination of mercury and water, effected by bringing the extremely comminuted particles into which each of them is divided by the agitation, within the fphere of each other's attraction; fo as to caufe both of them to lose their character or form of a fluid, and to conftitute, by their combination, a folid and powdery fubftance. It might be further alleged, that this union is deftroyed by the evaporation of the water, in consequence of its fuperior affinity to air, or by the operation of heat; and that when the watery particles thus quit the mercury, the particles of the latter naturally and instantly unite together, and reaffume their metallic ftate.-But the experiment above recited will not countenance these fpeculations. The water, too, is faid to acquire a peculiar smell and tafte, not eafy to be defcribed; and to leave, on evaporation, a particular kind of matter.
One of the Author's conjectures on this fubject is, that the mercury acquires this phlogifton from the water. He does not diffemble, however, the great ftrength of an objection to this hypothefis, furnished by an obfervation which we have already recited; that a portion of water is fo far from having its power exhaufted, or even diminished, on having been repeatedly employed in this procefs; that, on the contrary, when it has been previously used in the experiment, it has a much quicker and greater effect, than when it was employed for the firft time. The Author accordingly propofes other conjectures, on which, however, we cannot with propriety dwell; unless we had room to recite his many other curious experiments on this fubject: as they contain circumftances, the knowledge of which is abfolutely neceflary to enable the Reader to form a judgment concerning it.
We shall take an early opportunity of extracting some further interefting particulars from this work.
ART. VII. The Injured Iflanders; or, the Influence of Art upon the Happiness of Nature. 40. 2 s. Murray. 1779.
HE heroic Epifle is fuppofed to have been invented by Ovid. It is fingular that a fpecies of compofition, so beautiful, and, at the fame time, fo capable of variety, fhould have been fo little cultivated by fucceeding writers, Of all his cotemporaries (Sabinus excepted, whofe works, unfortunately, are loft) Propertius is the only one, whom we know of, that hath followed his example. His Epiftle from Arethusa to Lycotas abounds with many exquifite ftrokes of paffion and tenderness. It is to be lamented that this is the only poem of the kind that he has left us. Among our own countrymen his imitators have been few; and of thofe few Mr. Pope is the only one who has
hitherto been eminently fuccessful. It must be confessed, indeed, that Drayton, who first revived this fpecies of poetry among us, has left fome pieces, that, confidering the times in which he wrote, have confiderable merit. Drayton was a man of genius, and by no means deficient in judgment; but failing in thofe powers which the dramatic nature of his fubject demanded from him, his England's heroical Epifiles want that warmth of colouring fo effential to a true reprefentation of the characters he alfumes.
In modern times this mode of writing has been adopted, and in fome inftances not unfuccefsfully, as the vehicle of fatire and wit, for which, indeed, it seems not ill adapted. In the prefent inftance, however, it is employed according to the original purpose intended by its inventor. The poem before us is fuppofed to be written by Queen Oberea to Capt. Wallis. It is founded, as the Author informs us in his preface, on the remembrance of their mutual affection - a sense of her subsequent misfortunes-and a patriotic feeling for the fate of her country. The juft and liberal fentiments with which this performance abounds, do great honour to the Author's feelings as a man; and they are expreffed in language that will not injure his reputation as a poet.
The subject opens with the following lines:
Remov'd from power, from all its pomp retir'd,
No fuppliant crowds attend my fav'reign will
Where the green turtle flutters through the glade;
Where the pure ftream precipitates in foam,
There as I fit above the level plain,
After explaining whence this indifference to external objects arifes, the proceeds,
To thee alone, on Fancy's rapid wing,
I hafte impatient to the crowded shore :
In vain I haste,-no WALLIS meets me there,
The above lines are natural, and adapted to her fuppofed fituation. Nor is her character ill fupported in the following paffages:
Canft thou forget? can Memory e'er betray
To Heav'n and me alternately address'd,