Though Dr. VAN MARUM was convinced, by M. Lavoifier's experiments, that metals, calcined in atmospherical air, abforb from it that principle, which renders it fit for refpiration; yet he refolved further to investigate this point, by trying what would be the effect of a difcharge of the battery through a piece of wire confined in phlogifticated air. For this purpose, he took air, in which a burning coal had been extinguished, and which had afterwards ftood eight days upon water, that it might be entirely cleared from fixed air; with this, he filled a glafs cylinder, four inches in diameter, and fix inches high, clofed at the upper end with a brass plate; from the center of this plate the wire was fufpended, on which the experiment was made. The cylinder was fet in a pewter difh filled with water, and, to prevent its being broken by the expanfion of the air, its lower edges were fupported by two pieces of wood half an inch high. The lower end of the wire refted on the difh, which was connected with the outfide coating of the battery.

On tranfmitting the charge, in this manner, through wires of lead, tin, and iron, of only half the length of those which were calcined by an equal explosion in atmospheric air, no calcination took place. The first was reduced to a fine powder, which, upon trial by spirit of nitre, appeared to be merely lead; the two other metals were melted into small globules.

The Doctor then tried the fame experiment in pure, or dephlogisticated air, obtained from red precipitate; thinking that, in this, the metals would be more highly calcined, than in common air. His expectation was anfwered only by the lead, which was entirely reduced to a yellow calx, perfectly refembling mafticot. The other metals were not more highly calcined in this, than in common air; but the globules of iron acquired fo great a heat, as to retain it for fome feconds, even in the water, and to melt holes in the pewter dish into which they fell.

In nitrous air, calcination took place as eafily as in common, or in dephlogisticated air; this was contrary to Dr. VAN MARUM's expectation; but he accounts for it, by obferving that, from the experiments of Mr. Cavendish, and of M. Lavsifier, pure air appears to be one of the component parts of the nitrous acid.

In order to illuftrate M. Lavoifier's theory, Dr. VAN MARUM refolved to examine the phenomena refulting from the calcination of metals in water. This he tried with both iron and lead, and found that, in the moment of the explofion, a number of air-bubbles appeared on the furface, and the calx rofe, like a cloud, through the water. This, he thinks, is not fo easily accounted for, by the theory of Stahl, as by that of M. Lavoifier, because, according to the former, water does not readily:

10

readily either receive, or part with phlogifton; whereas the latter fuppofes this fluid to be compofed of the oxiginous principle, united with that of inflammable air: if this be true, nothing more is neceffary to calcination, than that the metal fhould acquire a greater affinity with the oxiginous principle, than fubfifts between this, and that of inflammable air, united with it in the composition of water. To collect the air, generated by these calcinations, was no eafy matter; as the violence of the fhock broke the glafs receivers employed for this purpose; at last, however, the Doctor contrived a method of receiving it in a glazed stone bafon. From the first calcination of lead, about a quarter of a cubic inch of air was produced, which fhewed no figns of inflammability; but, on every repetition of the experiment, a lefs quantity of air was generated; and, on an accurate trial of that produced by the fourth calcination in the fame water, it was found to confift of one part of inflammable, and three of atmospherical air. Our author defigns to repeat these experiments with water deprived of its air, by being boiled.

In order to imitate the phenomena of earthquakes, this ingenious philofopher followed Dr. PRIESTLEY'S method, and made the electrical explofion pafs over a board, floating on water, on which feveral columns of wood were erected; but this fucceeded only once. Reflecting that the electric explosion exerts the greatest lateral force when it paffes through imperfect conductors, and that water is, probably, its principal fubterraneous conductor, he laid two fmooth boards upon each other, moistening the fides in contact with water; upon the uppermoft, he placed pieces of wood, in imitation of buildings, the bafes of which were 3 inches long, and 1 broad. When the charge of the battery was tranfmitted between the boards, all these were thrown down by the tremulous and undulatory motion of that on which they stood.

In the next chapter, Dr. VAN MARUM gives an account of his attempt to repeat that interefting experiment, made by Mr. Cavendish, in which he produced the nitrous acid, by a mixture of pure, with phlogifticated air. Inftead of a fyphon, the Doctor made ufe of a glafs tube, one-fixth part of an inch in diameter, closed at one end, into which an iron wire, of an inch in diameter, had been inferted into this tube, filled with mercury, and fixed in a vertical pofition, was introduced the air, with which the experiment was to be tried. The dephlogifticated air was obtained from red precipitate, and had been thoroughly purified, by alkaline falts, from any acid it might have contained. With a mixture of five parts of this, and

* See Monthly Review, vol. lxxiv. p. 321.

three

three of common air, the tube was filled to the height of three inches, to which was added of an inch of lixivium, of the fame kind with that ufed by Mr. Cavendish. The refult was, that, after tranfmitting through the tube a continued ftream of the electrical fluid during fifteen minutes, two inches of the air were abforbed by the lixivium: more air being introduced into the tube, till it was filled to the height of three inches, it was again electrified. This process was repeated, till 8 inches of air had been abforbed by the lixivium: this was now examined, and found to be, in fome degree, impregnated with the nitrous acid; but it was very far from being faturated. With the fame lixivium, of which a quarter of an inch remained in the tube, the experiment was continued till 14 inches more of air had been abforbed; but its diminution was not perceived to decrease, though the lixivium had now abforbed 77 measures of air, each equal to its own; whereas, in the experiment related by Mr. Cavendish, only 38 meafures of air were abforbed by the alkali. But, notwithstanding this greater abforption, the lixivium was yet far from being faturated.

The experiment was repeated with pure air, produced by minium, moistened with the vitriolic acid, and deprived of its fixed air; seven parts of this were mixed with three of phlogifticated air, and lixivium added to the height of of an inch. Here, as in the former experiment, the diminution continued without any decreafe; and the lixivium, after it had abforbed 22 inches, and confequently 178 times its own measure of air, was very far from being faturated with the nitrous acid.

On this, Dr. Van Marum wrote to Mr. Cavendish, and finding, by his anfwer, that this gentleman had ufed pure air, obtained from a black powder produced by thaking mercury with lead, he requested to be informed of the process by which it is generated; but Mr. Cavendish, not chufing to communicate this at prefent, he determined to defer the repetition of the experiment, till this ingenious philofopher fhall have publifhed his mode of obtaining the pure air used in it.

The following chapter contains a relation of fome experiments made by fuffering the electric fluid to pass in a continued ftream through various kinds of air, inclofed, for this purpose, in the little glafs tube ufed in the laft experiments.

Pure air, obtained the week before from red precipitate, being placed over mercury, and electrified for thirty minutes, was di minished by one-fifth, the furface of the quickfilver foon began to be calcined, and, towards the end of the experiment, the glafs tube was fo lined with the calx as to cease to be transparent. By introducing a piece of iron, the electric ftream was made to pafs through the air without immediately touching the mercury; yet this was equally calcined. This phenomenon the Doctor

afcribes

afcribes folely to the diffolution of the pure air, the principle of which unites itself with the metal; as, in thefe experiments, the mercury had not acquired any fenfible heat. Two inches and three-quarters of the fame kind of air being placed over water, and electrified in the fame manner during half an hour, loft a quarter of an inch; and being fuffered to ftand twelve hours in the tube, was found to have loft one-eighth of an inch more. This was very nearly the fame diminution of the air that had taken place, when it was electrified over mercury; but, in this cafe, the process appears to be more flow, and the detached principle not fo readily abforbed. The air remaining after these experiments, being tried by the eudiometer, did not differ from unelectrified pure air taken from the fame receiver.

To determine whether the pure air retained any of the acid employed in its production, the Doctor repeated the experiment with air, obtained from red precipitate, confined by an infufion of turnfole, but could not perceive in it the leaft change of colour. He alfo electrified air, obtained from minium and the vitriolic acid, placed over fome diluted vinegar of lead, but this was not rendered at all turbid.

Three inches of phlogisticated air being electrified, during the first five minutes, were augmented to 3 inches, and, in the next ten minutes, to 3 inches: fome lixivium was then introduced to try whether this would abforb it; but, upon being electrified fifteen minutes, the column rofe to the height of 3 inches. It was fuffered to stand in the tube till the next day, when it was found to have funk to its original dimenfion.

Nitrous air, confined by lixivium, being electrified during half an hour, loft three-quarters of its bulk; the lixivium appeared to have abforbed a great deal of nitrous acid; and the air remaining in the tube did not feem to differ from common phlogisticated air. Some of the fame nitrous air, confined by lixivium, was, by ftanding three weeks, diminished to half its bulk, and this refiduum alfo proved to be phlogisticated air. Thus electricity very fpeedily effects that feparation of the nitrous acid from nitrous air, which is flowly produced by the lixivium alone.

Inflammable air, obtained from fteel filings and the diluted vitriolic acid, being confined by an infufion of turnfole, was electrified for ten minutes without any change of colour in the infufion, or any alteration in the dimenfion of the air. The tube, being filled with the fame air to the height of 2 inches, and placed in diluted vinegar of lead, was expofed to the electric ftream during twelve minutes, in which time the inclosed air rofe to five inches; but the vinegar remained perfectly clear. Three inches of inflammable air, obtained from a mixture of Spirits of wine with oil of vitriol, on being electrified for

fifteen

fifteen minutes, rofe to ten inches; thus dilated, it loft all its inflammability, and when nitrous air was added, no diminution enfued.

A column of alkaline air, obtained by heat from spirit of fal ammoniac, three inches high, was electrified four minutes, and rofe to fix inches, but did not rife higher when electrified ten minutes longer. It appears that this air is not expanded more by the powerful electric ftream from this machine, than by the common fpark. Water would not abforb this electrified

air, which was in part inflammable.

The tube, being filled, to the height of an inch, with spirit of fal ammoniac, and inverted in mercury, was electrified four minutes; in which time, the tube was filled with eight inches of air, which proved to be equally inflammable, and as little abforbed by water, as the alkaline air. Hence Dr. VAN MARUM Conjectures that this air is only the volatile alkali rendered elaftic.

The last chapter contains an account of a very ingenious experiment to illuftrate fome phenomena obferved in thunderftorms. Two balloons, made of the allantoides of a calf, were filled with inflammable air, of which each contained about two cubic feet. To each of thefe was fufpended, by a filken thread about eight feet long, fuch a weight, as was juft fufficient to prevent it from rifing higher in the air; they were connected, the one with the pofitive, the other with the negative conductor, by fmall wires about thirty feet in length, and being kept near twenty feet asunder, were placed as far from the machine, as the length of the wires would admit. On being electrified, thefe balloons rofe up in the air as high as the wire allowed, attracted each other, and uniting, as it were, into one cloud, gently defcended. The rifing of these artificial clouds is afcribed to the expansion of the air they contained, in confequence of the repulfive force communicated to its particles by electricity: when in contact, their oppofite electrical powers deftroyed each other, and they recovered their specific gravity, by lofing the caufe of its diminution. In order to render this experiment more perfectly imitative, the Doctor fufpended to the balloon which was connected with the negative conductor, a bladder filled with a mixture of inflammable and atmospherical air, which, being kindled by the fpark that took place on the union of these clouds, gave a confiderable explofion. From these experiments, the Doctor explains the fudden elevation of the clouds, and the violent fhowers of rain and hail, which often accompany thunder-ftorms.

Dr. VAN MARUM intends to make confiderable additions to his battery, as he finds that the machine is capable of charging a larger furface of coated glafs; and defigns, in his next pub

lication,