killed in the methods of examining the pro perties of mineral waters.

17. Doctor Brownrigg, who made his experiments on Pyrmont water at the fpring head, never found that it contained fo much as one half of an equal bulk of air; but in this method the water is eafily made to imbibe an equal bulk. For it must be observed, that a confiderable quantity of the most soluble part of the air is incorporated with the water, as it firft afcends through it, before it occupies its place in the upper part of the veffel.

18. The heat of boiling water will expel all the fixed air, if a phial containing this impregnated water be held in it; but it will often require above half an hour to effect it compleatly.

19. If any person would chufe to make this medicated water more nearly to resemble genuine Pyrmont water, Sir John Pringle informs me, that from eight to ten drops of Tinctura Martis cum fpiritu falis must be mixed with every pint of it. It is agreed, however, on all hands, that the peculiar virtues of Pyrmont, or any other mineral water which has the fame brifk or acidulous tafte, depend not

upon

upon its being a chalybeate, but upon the fixed air which it contains.

But water impregnated with fixed air does of itself diffolve iron, as the ingenious Mr. Lane has difcovered; and iron filings put to this medicated water make a ftrong and agreeable chalybeate, fimilar to fome other natural chalybeates, which hold the iron in folution by means of fixed air only, and not by means any acid, and these chalybeates, I am informed, are generally the moft agreeable to the tomach.

of

20. By this procefs may fixed air be given to wine, beer, and almost any liquor whatever: and when beer is become flat or dead, it will be revived by this means; but the delicate agreeable flavour, or acidulous tafte communicated by the fixed air, and which is manifeft in water, will hardly be perceived in wine, or other liquors which have much taste of their

1own.

21. I would not interfere with the province. of the phyfician, but I cannot intirely fatisfy myfelf without taking this opportunity to fuggeft fuch hints as have occurred to myself, or my friends, with refpect to the medicinal uses

.U

of

of water impregnated with fixed air, and also of fixed air in other applications.

In general, the diseases in which water impregnated with fixed air will moft probably be ferviceable, are those of a putrid nature, of which kind is the fea-fcurvy. It can hardly be doubted, alfo, but that this water must have all the medicinal virtues of Pyrmont water, and of other mineral waters fimilar to it, whatever they be; efpecially if a few iron filings be put to it, to render it a chalybeate, like genuine Pyrmont water. It is poffible,

however, that, in fome cafes, it may be defirable to have the fixed air of Pyrmont water, without the iron which it contains.

Having this opportunity, I fhall also hint the application of fixed air in the form of clyfters, which occurred to me while I was attending to this fubject, as what promises to be ufeful to correct putrefaction in the intestinal canal, and other parts of the system to which it may, by this channel, be conveyed. It has been tried once by Mr. Hey above-mentioned, and the recovery of the patient from an alarming putrid fever, when the ftools were become black, hot, and very fetid, was fo circumftanced, that it is not improbable but that it might be owing, in fome measure, to those

clyfters.

clyfters. The application, however, appeared to be perfectly eafy and fafe.

I cannot help thinking that fixed air might be applied externally to good advantage in other cafes of a putrid nature, even when the whole system was affected. There would be no difficulty in placing the body fo, that the greatest part of its furface fhould be expofed to this kind of air; and if a piece of putrid flesh will become firm and fweet in that fituation, as Dr. Macbride found, fome advantage, I should think, might be expected from the fame antiseptic application, affifted by the vis vita, operating internally, to counteract the fame putrid tendency. Some Indians, I have been informed, bury their patients, labouring under putrid diseases, up to the chin in fresh mould, which is also known to take off the fœtor from flesh meat beginning to putrify. If this practice be of any use, may it not be owing to the fixed air imbibed by the pores of the skin in that fituation? Following the plough is also an old prescription for a confumption, as alfo is living near lime kilns. There is often fome good reason for very old and long continued practices, though it is frequently a long time before it be difcovered, and the rationale of them fatisfactorily explained.

Being no phyfician, I run no rifque by throwing out thefe random hints and conjectures. I fhall think myself happy, if any of them fhould be the means of making those perfons, whom they immediately concern, attend more particularly to the fubject. My friend Dr. Percival has for fome time paft been employed in making experiments on fixed air, and he is particularly attentive to the medicinal ufes of it; and from his knowledge as a philofopher, and fkill in his profeffion, I have very confiderable expectations.

PART