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that the whole of this diminution is not to be attributed to this caufe.

In the preceding catalogue of fubftances and proceffes, that diminish and injure common air, we have purpofely omitted the electric matter, in order that we might treat more particularly of the Author's curious difcoveries relating to this fubject. A thunder ftorm has popularly been fuppofed to purify the air, and we know not but that it may ultimately, or in its confequences, produce that falutary effect. But from the Author's experi ments it appears that the electric fluid, in its paffage through air, diminishes it, and renders it in the highest degree noxious: for a portion of common air, through which it has paffed for fome time, is rendered incapable of effervefcing with nitrous air, or of being diminished any further by a mixture of that fluid. In fhort, it appears to be reduced to the fame noxious and diminished state, as that to which it is brought by the burning of charcoal, or any of the other proceffes above mentioned,

The Author detected this fingular and unexpected quality of the electric matter, by means of an experiment, in confequence of which he, at the fame time, afcertained the real exiftence and origin of the acid, which had been fuppofed to accompany, or even to conftitute a part of the electrical fluid :-principally, we apprehend, on account of the fenfation of acidity, which is excited on receiving upon the tongue the fmall fparks, or pencil, iffuing from a pointed body when electrified. For though fome writers have spoken pretty confidently of the electrical acid, we are not acquainted with any who had proved its existence, by exhibiting it to view, by means of a chemical combination with other bodies. The Author's former unfuccefsful attempts, and fome of our reflections on this fubject, may be seen in our 37th volume *.

In order to detect this fuppofed acid, by its effects on the blue vegetable juices, and by a method different from that which he had before followed, the Author made ufe of a glass tube, into the upper end of which he inferted and cemented a piece of wire, the upper extremity of which terminated in a brafs knob. Into this tube was introduced a fufficient quantity of water, tinged blue with the juice of turnfole or archil, which stood at fuch a height, as that its furface was within the friking diflance from the lower end of the wire, when the latter was electrified. The lower end of the tube, which was open, was immerged in a veffel of the tinged water.

After having caufed the electric fpark to pafs about a minute from the lower extremity of the wire to the furface of the liquor in the tube, he perceived that the upper part of the tinged fluid

*December 1767, P. 457.

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began to look red, and in about two minutes it was very manifeftly fo; and the red part, which was about a quarter of an inch in length, did not readily mix with the reft of the liquor.' He observed alfo, that if the tube lay inclined while he took the sparks, the redness extended twice as far on the lower fide as on the upper.'


While he obferved thefe figns of an acid acting on the tinged fluid, he perceived likewife that in proportion as the liquor became red, it advanced nearer to the wire, fo that the space of air in which the fparks were taken was diminished; and at length found that the diminution was about ore fifth of the whole fpace; after which, more electrifying produced no fenfible effect.'

Without changing the air contained in the tube, the Author changed the liquor, in order to determine whether the fame effects would be produced by caufing the electric matter to act on a fresh quantity of the blue fluid, while it paffed through the fame portion of air. He, therefore, by means of an air pump, rarefied the air contained in the tube, juft fo much as to expel all the liquor; and then admitted fresh blue liquor into its place. But now, on repeating the electrification, the electric matter, paffing through the fame air as before, produced no change of colour in the fluid, or any variation in the height of it.

From this part of the experiment Dr. Priestley concludes that the former figns of acidity, and change of dimenfions, proceeded from fome matter contained in the air confined in the tube; and that this portion of air had been decompounded, as far as poffible, by the electric matter, in the firft ftage of the experiment; and that it had been made to depofit fomething that was of an acid nature.-Had this acid refided in the electric matter, it is reasonable to expect that it would have continued to produce the fame change of colour, in fresh portions of the coloured fluid, on every fubfequent repetition of the experiment, as at firft.

That the wire did not, in any degree, contribute to these effects, otherwife than as a conductor of electricity, was made evident by the Author's diverfifying the experiment, in fuch a manner, as to caufe the electric fpark to pafs through a portion of air, contained in the upper arched part of a bent glass tube, from one furface of the tinged fluid, contained in one of the legs of it, to the surface of the liquor contained in the other; each. of the extremities of the tube at the fame time standing in a bason of quickfilver. The effect was, that the liquor, in both the legs, became red, and the space of air between them was contracted, as before."

From thefe and other experiments and confiderations, the Author concludes, that the electric matter either is, or contains, phlogifton: for common air is diminished by it, and brought into a ftate fimilar to that to which it is reduced by every other phlogistic process. The diminution of the common air, in the preceding experiment, appears evidently to have been owing to its having been decompounded by the electric matter, and made to part with the fixed air, which appears from the Author's experiments to be at all times contained in, and combined with it : for, on taking the electric fpark on lime water put into the tube, instead of the blue liquor, the lime was precipitated, as the air diminished.

This theory explains the precipitation of the calcareous earth in lime-water, on breathing into it. This effect, according to the Author, is not produced by any fixed air exhaled immediately from the lungs; but is caufed by the common air inhaled into them, which is decompounded by the phlogifton that is dif charged from that organ. This phlegifton, uniting with the other principles that conftitute common air, precipitates the fixed air contained in it, which is now left at liberty to combine with the lime.

These observations confirm the Author's conjecture, that animals die in confined air, not becaufe they have exhaufted the fuppofed pabulum vite contained in it; but because the neceffary difcharge of the phlogistic matter from the lungs is prevented, by the air's becoming foon faturated with that principle, fo as not to be a fufficient menftruum to take it up.

At the end of this fection, the Author, in a letter very properly addreffed to Sir John Pringle, controverts the doctrine maintained by Dr. Alexander, (in his Experimental Enquiry into the Caufes of putrid Difcafes) who, on the ftrength of certain experiments, denies or doubts of the infalubrity of putrid marshes, and does not allow that they can produce thofe putrid diseases, which almost universally have been attributed to them. We are glad to find the objections which we made to this novel and dangerous doctrine, confirmed by the experiments of Dr. Priestley; who found that the air iffuing fpontaneously from water, which appeared only to be moderately putrid, was in the highest degree noxious. He found likewife, that when even wholesome air was agitated only one minute in this water, a candle would not burn in it; and that good air was likewife so far injured, as to extinguifh a candle, after it had been kept only in contact with this water, without any agitation, for the space of two days.

* See M. REV. vol. xlviii. June 1773, P. 443.

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• Thefe

These facts,' fays the Author, certainly demonftrate, that air which either arifes from ftagnant and putrid water, or which has been for fome time in contact with it, muft be very unfit for refpiration; and yet Dr. Alexander's opinion is rendered fo plaufible by his experiments, that it is very poffible that many perfons may be rendered fecure, and thoughtless of danger, in a fituation in which they must neceffarily breathe it. On this account, I have thought it right to make this communication as early as I conveniently could; and as Dr. Alexander appears to be an ingenuous and benevolent man, I doubt not but he will thank me for it.'

This letter, which is likewife printed in the last volume of the Philofophical Tranfactions, is there followed by another, written by the ingenious Dr. Price; which confirms Dr. Prieftley's obfervations on this fubject, by deductions from Mr. Muret's tables of the rates of mortality, in a certain parish fituated among marshes, in the diftrict of Vaud, compared with fimilar registers kept in different parts of the Alps. We cannot any where more properly give a fhort extract of Dr. Price's obfervations, than in the prefent place.

From a comparison of thefe tables it appears, that the proba bilities of life are higher, in a remarkable degree, in the hilly country, than in the marshy parifh above mentioned. One half of all born in the mountains, live to the age of 47: in the marshy parish, one half live only to the age of 25. In the hills one in 20, of all that are born, live to 80: in the marshy parish, only one in 52 reaches this age. In the hills, a perfon aged 40 has a chance of 80 to 1, for living a year in the marthy parish, his chance is not 30 to 1.-In the hills, perfons aged 20, 30, and 40, have an even chance for living 41, 33, and 25 years refpectively in the fenny parifh, perfons, at these ages, have an even chance of living only 30, 23, and 15 years.

For the many curious additional obfervations made by the Author, with refpect to the nature and properties of nitrous, acid, inflammable, and fixed air, we muft refer the reader to the work itfeif; as well as for his conjectures, contained in the laft fection, with refpect to the conftituent principles of thefe different kinds of air, and the conftitution and origin of the atmosphere. We cannot however refift the temptation of giving fome, though an imperfect account of the Author's fpeculations on the nature, or rather on one of the supposed functions, of the electric matter.

Thefe random thoughts' he has thrown together into a fection by themselves; that readers of lefs imagination, and ho care not to advance beyond the regions of plain fact, may, they please, proceed no further, that their delicacy be not



offended.'-One who has fo largely added to the stock of philofophical facts, as the Author, has acquired a right, we think, to more than ufual indulgence for his opinions; how excentric foever they may appear at first fight, and however diftant may be the analogies on which they are founded.

There is nothing, as he obferves, in the hiftory of philofophy, which appears more ftriking, than the rapid progress that has been made in our knowledge of the operations of the electric matter; when we confider the firft trifling effects produced by it, that were attended to, and compare them with the lately discovered diverfified operations of this extenfive and powerful agent; which fhew that it bears a confiderable part in many of the most important proceffes in nature, differing apparently very effentially from each other. The electrical operations of the Torpedo, performed in a conducting element, have lately fhewn us how far we are, even yet, from being acquainted with all the modifications of this fluid.

These last mentioned phenomena, together with the facts which the Author has obferved, concerning the identity or near relation of the electric fluid, and phlogifton, lead him, in fpeculating on this fubject, to confider the electric matter as the probable caufe of muscular motion. In fupport of this conjecture, he alleges, among other reafons, the well known effects of the electrical fluid, when directed through the mufcles of a living animal, which it inftantly forces to contract. He obferves, that every article of nourishment (from which the materials of all mufcular motion must be derived) contains phlogifton. He fuppofes, that animals have a power of converting this phlogifton, from the ftate in which they receive it in their nutriment, into that other form or modification, in which it perfonates, and is called, the electric fluid; that the brain,

befides its other proper ufes, is the great laboratory and repo fitory for this purpose; that by means of the nerves this great principle, thus exalted, is directed into the mufcles, and forces them to act, in the fame manner as they are forced into action when the electric fluid is thrown into them ab extra.'


He further fuppofes, that the generality of animals have no power of throwing this generated electricity any farther than the limits of their own system; but that the torpedo, and animals of a fimilar conftruction, have likewife the power, by means of an additional apparatus, of throwing it farther, fo as to affect other animals, and other fubftances at a distance from them.'

These are the outlines of Dr. Priestley's excurfions into the regions of conjecture. Thofe who think deeply will not perhaps confider them as too bold and excentric. Muscular mo tion is one of thofe grand and recondite proceffes of nature, which do not lie in the common tract of obfervation. It is one

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