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have supposed, that they produce this deleterious effect folely by the exclufion of the oxygen of the atmosphere. Between these airs there feems a remarkable difference in their power to produce infenfibility and death. Hydrogen, or inflammable air, appears the leaft noxious, both when infpired alone, or mixed with atmospheric air. Azote comes next; then fixed air; and the hydrocarbonate appears extremely active, and I prefume, adds Dr. BEDDOES, that for recovery from afphyxia in water (when but little goes down the wind-pipe *) hydrogen air and azote will be much more easy, than from af

*As the intention of this work is to fet forth TRUTH, and not to combat erroneous opinions, the reader will not be furprised to find this question, "Whe"ther the introduction of water into the wind-pipe is, or is not, the imme ❝diate cause of death in drowning?" as mentioned by DE HAEN, and others, wholly overlooked in the Section profeffedly treating on the recovery of drowned perfons. We will however confider it for a few moments in this place. If an artificial dropfy of the chest be produced by injecting two ounces of water into the lungs, through the wind-pipe of a healthy animal, it immediately causes oppreffion, and difficulty of breathing, but no fatal afphyxia enfues: but the water is gradually abforbed, and the fymptoms foon disappear. In drowning, the cafe is very different, fince a few minutes fubmerfion is fufficient to destroy the life of the animal, even whether water enter the wind-pipe, or not, for in many cafes none is found in the lungs after death. This is decifively proved by the justly celebrated Dr. GOODWIN. He placed animals in quickfilver and in ink, and fo little of this weighty metal or coloured fluid was found in the lungs as left no doubt of it not being the proximate cause of drowning. In one experiment after expiration the animal was drowned in ink, and no fluid whatever was found in the lungs. Vide Dr. GOODWIN's Effay on Life as connected with Refpiration,to which was adjudged the gold medal. PROPTER optimam DISSERTATIONEM DE RESUSCITATIONE.

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phyxia

phyxia occafioned by other unrefpirable mediums. It may be reasonably conjectured, that fixed air, and hydrocorbonate, act by combining with the oxygen already in the blood, as well as by its excluding this principle: and this conjecture is fupported by the hydrocarbonate poffeffing a much less effect, when it has depofited fome part of its charcoal; as alfo from the alteration which it is found to produce upon the blood*.

Mines and coal-pits are frequently infefted with two fpecies of noxious air. The first is termed by the miners Choke-damp, which is fixed air, which being specifically heavier than atmofpheric air, occupies the bottom of the mine. The other is called the Fire-damp, which is inflammable air, and being ten times lighter than common air, afcends to the upper region of the mine. The former is probably formed from the charry matter in the bowels of the earth, the latter from a fine

*Having, fays this ingenious experamentalift, put two fowls, the one in fixed air, and the other in hydrocarbonate; to my great furprife, I found in the former the fame appearances as in drowned or ftrangled animals, only the liver appeared a fhade paler. But in the latter the whole flefh was throughout of a light pink colour when boiled, and the marrow of a fine red. The former tasted nearly as ufual, the latter was certainly much more tender. Other acids, befide the carbonic acid, produce the fame change on venal blood, rendering it of the arterial colour. The hydrocarbonate air is the happy discovery of the ingenious Mr. WATT, one of the firft chemifts of the age.

aqueous

aqueous exhalation, and fpontaneous decompofition. But here we are to confider the manner in which thefe evils are to be remedied, rather than the mystery of their formation.

To obviate the fire-damp, miners are in the habit of crawling on their hands and feet, and with a taper affixed to a long stick for setting fire to the inflammable air*, which sometimes goes off with a terrible and sometimes fatal explosion.

With respect to the choke-damp, no means has yet been devised but ventilation, it being fuppofed to be stagnated air.

With refpect to the mode of ventilation, and the correction of this fpecies of air, we will offer but a few words.

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* Some years back a scheme was projected at WHITEHAVEN to light up that town by means of the inflammable air in the pits, which was to be conveyed by pipes throughout every street. As chemistry advances, may not the water of the THAMES be decompofed in certain appropriated places, and the inflammable air conveyed throughout Strand and City, and this part of the town be fplendidly illuminated each night at a very moderate expence ?-Since the discovery of the nature of combuftion, and the constituent principles of water, it is hoped that the candid reader will not confider this hypothefis as a mere rhapsody. Were a person to survey London now illuminated as it is by Argent's lamps, and the product of the Greenland fisheries, and compare it with what it was five hundred years back, and he will perhaps feel inclined to extend his views on the prospect of future improvements !

A Shaft,

Afhaft*, as it is called, fhould be carried down fomewhat flanting, and the funnel conveyed to the bottom of the pit, whereby the heavier and purer air from above would defcend; while a perpendicular shaft, or chimney, with its mouth arifing from the top, would carry up the lighter and corrupted air together with the inflammable.

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* Vide Vol. I. page 67. It is curious to obferve the knowledge which our ancestors had of the nature of air. KAY, in a work, entitled The Wisdom of God manifefted in the Works of Creation, written in the last century, fays, page 73, in speaking of air-fhafts, " Indeed, were there no damps in minés, yet the nitrous part" (the NITROGEN or OXYGEN as it is now called)" of "the air being spent and consumed by the breathing of the miners, the re“maining part” (the AZOTIC)" would be unfit for respiration, unless new

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and fresh air were to fucceed."-In another place he says, page 72, "The "air is the fewel of the VITAL FLAME, without which it would speedily « languish and go out.”—Again he says, p. 73, “ Fishes, and other water “animals, cannot support life without it, for if you put your hand or any ❝ cover over a vessel containing fish, so as wholly to exclude the air, they will "be fuddenly fuffocated."-Again, page 74, "Neither is it less neceffary to

infects, for if you put oil upon them, fo as to obftruct thofe orifices that "draw in air, if you obftruct only fome, the parts that are fupplied with air ❝ from them are shortly deprived of lƆTION, while the reft of the parts "that are untouched retain it."-Again, page 75, he says, "I am perfuad❝ed, with my learned friend Dr. HULSE, that the chief use of the circulation "of the blood, through the cotyledons of a calf in the womb (which I have ❝ often diffected), and by analogy through the placenta uterina, seems to be

THE IMPREGNATION OF THE BLOOD WITH AIR" (he has above explained the fpecies of air)" for the feeding the vital flame: for if it 66 were only for nutrition, what need of two fuch great arteries to convey the "blood

Should fixed air, notwithstanding this, ftagnate in fome parts of the pit, an engine, fuch as they water gardens with, fhould be used to abforb the fixed air, or else water fhould be kept continually boiling; for as the fteam condenses, it would become impregnated with the fixed air. This ought conftantly to be observed, where charcoal fires are employed. A tea-kettle boiling by the fide would obviate the chief, if not the whole, of the evil.

In the Hift. de L'Academie des Sciences, Anno 1710, we are told of a baker of Chartres, going along with his son, a robust young man, into a cellar 36 stairs deep, who followed him with a candle, the candle went out on the middle of the stairs. Having lighted it afresh, he was no fooner got into the cellar, than he cried out for help, and they heard no more of the son or father. His brother, an able youth, ran immediately after him, cried out he was dying, and was heard no more. He was followed by his wife, and the by a maid, and still it

"blood thither? Secondly, I have observed the umbilical vessels to terminate in a multitude of PAPILLA. Now thefe PAPILLE do refemble the "RADII of a FISH'S GILLS, and most probably have the fame use, viz. To SECRETE AIR, and convey it to the foetus, fo that the fœtus in the womb "doth resemble a fish in its mode of living, or elfe why should there be such "an inftant neceffity of refpiration fo foon as the fœtus is fallen off from the ❝ womb ?"

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