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lead to such important conclusions, that it becomes necessary, especially in a new and fingular case, to inquire whether there may not exist some particular exceptions to the general rule; or whether it may not be possible that air, saturated with the effluvia of certain bodies, may not thereby be rendered incapable of affecting, or being affected by, nitrous air, and yet may continue perfectly falubrious.
Though it may be true universally that, on the admixture of nitrous air with any kind of mephitic or perfectly noxious air, no diminution will be produced ; it does not necessarily follow that the converse of this proposition must be likewise universally true; or that, in every cafe whatever, when no diminution is observed, the air exposed to the nitrous test must neceffarily be mephitic or perfectly noxious. It was till lately universally believed that air, in which a candle would burn, was wholesome and fit for respiration. Dr. Priestley has however discovered one remarkable exception to this general and long established test of the purity of air. He has, by more than one process, reduced nitrous air into such a state as to perfonate common air, in this very quality, so that a candle would burn in it quite naturally; and yet, he found that this air continued as highly noxious as ever. (See particularly his Observations on Air, vol. iii. pag.
We shall only relate some of the results of another class of the Author's experiments, made with a view to ascertain the effects of the effluvia arising from moist and marshy soils upon air ; and which are known to be the source of the most dangerous putrid diseases.
Two ounces of black mud, taken from a stinking morass at York, occasionally overflowed by a brook, being put into an 8 ounce yial of air, affected it so in 12 hours as to reduce it, according to the test of nitrous air, from about 60° or 62° to 34° or 36. When this mud was made perfectly dry, so as to be reduced to a powder; it affected the air which was exposed to it so litile, that the diminution, in several experiments, proceeded only from 62° to 60°:-—But the very fame powder being again reduced to the consistence of mud, by the addition of a little was instantly extinguished on putting it into a quart of air in which various flowers and leaves of vegetables had remained 48 hours. This air was found to be perfectly noxious, according to the nitrous teft.-The Reviewer of the present Article, not choosing to take such liberties with a mouse, as with his own proper person, inspired this air more than once, through a bent tube of a large bore ; but was not sensible of any inconvenience, nor did he perceive any thing par. ticular in it. No stress, however, can be laid upon this trial; as this air must have been greatly diluted by that contained in the fauces and trachea of the Experimenter.
water, and inclosed in a similar vial of air, affected the latter so far as to reduce the diminution from 62° to 49°; and on standing longer, the diminution was reduced from 62° to 29o. Again, when more water was added to this mud, so as to swim to a considerable height above the powder, after the latter had subsided, the air again tried by the test was in no instance found to produce a greater reduction of the diminution than from 62° to 56o.
The results of these and other experiments, which we omit, correspond with the observations of Sir John Pringle, and other practical medical writers; who have remarked that the diseases peculiar to low and marshy situations ' seldom begin to appear, till the water is so far evaporated, as to leave a black and slimy mud ;-that these diseases cease when the bogs and marshy grounds have been drained, and are become perfectly dry ;--and that, on the other hand, the danger arising from marshes and bogs, is, in a great measure, obviated, on their being laid wholly under water. In this last case, the Author observes that the putrid fermentation is either prevented by too much moisture; or the eMuvia are absorbed in passing through the fuperincumbent bed of water.' Article 9. Observations on the Population and Diseases of Chester,
in the Year 1774. By J. Haygarth, M.D. This paper contains some judicious and useful observations, which are fucceeded by several accurate tables of mortality, diseases, &c. The most striking of the Author's remarks relates to the very uncommon healthiness of the city of Chester. In one of these tables, the Author has collected from different wri. ters the proportionable number of inhabitants that die annually in various places; and, in the table that precedes it, has given the annual average, during ten years, of the deaths in the city of Chester. From the latter, we collect that only 1 in 58 dies annually in the fix parishes within the walls, and, in the whole town collectively, i in 40: whereas from the other it appears that there die annually-at Jamaica, i white person in 5;-at Vienna, í in 191 ;-at London, I in 204 ;-at Edinburgh, i in 20, &c. We omit the ratio of deaths in other large towns, and proceed to Manchester, the last and healthiest set down in this table, where the proportion is 1 to 28. It appears, too, that the healthiness of the city of Chester, within the walls, exceeds even that of any of the country parishes set down in the abovementioned table; where we find that in the Pais de Vaud, and some country parishes in Brandenburgh, there dies i in 45. The highest number here given is 1 in 54, opposite to Stoke Damerel, in Devonshire.
The causes of this fingular degree of healthiness in Chester may, perhaps, be partly ascertained, by attending to some pe
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culiarities in its situation and structure, which the Author ac. cordingly describes; and from which it appears that it is probably exempted, in consequence of these circumstances, from two of the principal sources of diseases; ftagnant moisture, and putrefaction. It is seated on a rising promontory, formed of a sandy, porous rock, through which water quickly filters. The streets likewise descend, in every direction, from the summit of this rock, with a gentle declivity, to the edge of it; whence there is every way a perpendicular fall of several yards.-The clearness of the air too appears to be extraordinary, from a register kept the last four years; during which interval, there were observed only 32 hazy, and 6 foggy, mornings.
PAPERS relating to ELECTRICITY. Article 5. A Cure of a Muscular Contraction by Electricity. By
Miles Partington, in a Letter to William Henly, F.R.S.
The subject of this extraordinary, and seemingly indisputable, cure, effected by electricity, was a Miss Lingfield, who, in consequence of a cold contracted above two years before, was seized with a violent pain in the back of her head, which terminated in an obstinate contraction of the muscles of her neck, by which it was drawn down over her right shoulder.-- The back part of it was twisted so far round, that her face turned obliquely towards the opposite fide, by which deformity she was disabled from seeing her feet, or the steps as she came down stairs.'On the other side, she felt a continual and sometimes violent pain, occafioned by the extreme tension of the teguments, &c. on that side. She was subject to frequent febrile attacks; and was sometimes slightly paralytic. Notwithstanding all the endeavours of the faculty to procure her relief, the little alteration obfervable in her disorder was rather on the unfavourable fide.
Mr. Partington first insulated and electrified her on the 18th of February; drawing strong sparks from the Mastoideus muscle and the other parts affected, for about four minutes. The electrification was repeated on the 24th and 27th, and on March the 3d, 5th, 6th, 7th, and gth. Some amendment was perceived after the first trial, and some advantage was evidently gained on each repetition. In consequence of particular circumitances, the process was afterwards continued by Mr. Henly; who daily repeated it (three evenings excepted) during the space of a fortnight; at the end of which time, the disorder appears to have been completely removed,
Mr. Henly drew strong sparks from the muscles on both sides of the neck, during ten minutes; and likewise generally added two shocks from a bottle containing 15: square inches of coated surface fully charged, through her neck and one of her arms, crossing the neck in different directions.
Article 15. Sundry Papers relative to an Accident from Lightning
at Purfleet, May 15, 1777 ;- particularly new Éxperiments and Obfervations on the Nature and Use of Conductors. By Benjamin Wilson, F.R.S. &c.
The accident which befel the house built for the occasional accommodation of the Board of Ordnance at Purfleet is, in general, well known to our philofophical Readers. This house was furnished with a pointed conductor; at the distance of quo feet from the point of which, a corner of the building received some damage from a flash of lightning, which struck off a piece of stone, and one brick, and loosened a few other bricks; which it removed less than half an inch from their places. This damage, small as it is, hath rendered it problematical, with some, whether the conductor with which this house was furnished had executed any part of its office.
Mr. Willon, who had originally opposed the erection of this and other pointed conductors at Purfleet, was led, on the prefent occafion, to make the experiments, the relation of which constitutes the principal part of this long Article. An immense conductor was fitted up, at the expence of the Board of Ord. nance, and suspended in the Pantheon ; consisting of a great number of drums covered with tinfoil, which formed a cylinder of above 155 feet in length, and above 16 inches in diameter. This, when properly charged, was intended to represent a thunder-cloud; and there were occasionally added to it 4800 yards of wire. A model of the Board-House at Purfleet was likewise constructed, to which was occasionally annexed a pointed, or a blunt, conductor, and which by means of weights, &c. was made to pass under the artificial cloud, with a determinate velocity, supposed to be equal to that with which thunderclouds in general move.-In his estimation of this velocity, however, we must observe that the Author has attended only to the real, and has overlooked what we may call the relative, or angular, velocity.
It is impossible for us to give any satisfactory account of the various experiments made with this magnificent apparatus ; or of the Author's conclusions from several of them. It
be fufficient to observe, that his inferences from them are drawn so as to strengthen his former opinion with respect to the danger of employing elevated conductors, armed with pointed wires; on a supposition that they invite the lightning. They will not however, we apprehend, appear so satisfactory to others as they appear to the Author,
The firing of gunpowder by this apparatus, by the electric aura or blast, without a spark, or the affistance of the Leyden charge, is perhaps one of the most notable effects produced by it. Upon a staff of baked wood a stem of brass was fixed,
which terminated in an iron point at the top. This point was put into the end of a small tube of Indian paper, made somewhat in the form of a cartridge, about one inch and a quarter long, and about two-tenths of an inch in diameter. When this cartridge was filled with common gunpowder (unbruised) the wire of communication with the well' (i.e. the earth) & was then fastened to the bottom of the brass stem. Being fo circumstanced, and whilst the charge in the great cylinder and wire was continually kept up by the motion of the wheel, the top of the cartridge was brought so near to the drums as frequently to touch the metal. In this situation, a small faint lu. minous stream was observed between the top of the cartridge and the metal drum.
« Sometimes this stream would set fire to the gunpowder at the instant of the application ; at others it would require half a minute or more before it took effect. But this difference in time might probably arise from some difference in the circumstances; for any the least moisture
the least moisture in the filk lines, the powder, or in the paper itself, was unfavourable to the experiment.'
This new method of firing gunpowder, by a luminous stream of the matter of lightning, surely merits the most serious actention; and more especially in those cases where pointed conductors are fixed to secure magazines of gunpowder from such accidents.'—Tinder was still more readily fired by the electric blast.
Instead of giving any opinion of our own on the Author's experiments, and deductions from them ; it will be more fatisfactory to our Readers if we give that of the Committee appointed by the Royal Society, to consider of the most effectual method of securing the powder magazines at Purfleet against the effects of lightning, in compliance with the request of the Board of Ordnance,
The Committee, among other things, declare, that having attentively examined the experiments and observations of Mr. Wilson, and having maturely considered the subject at large, it is their opinion that it is very improbable that the powder magazines, guarded in the manner in which they are at present, that is, with elevated pointed conductors, should receive any damage from lightning. They even recommend to the Board of Ordnance the erection of several additional rods, as acutely pointed as possible, on the roofs and some other parts of each of the magazines ; and, for the sake of greater security, they propose that the intire roofs and the tops of the end walls should be covered with lead connected with the said rods. They propose these and other directions, under a persuasion that elevated rods are preferable to low conductors terminated in rounded ends, knobs, or balls of metal ;'--and that the experiments and reasons,