« AnteriorContinuar »
lead to fuch important conclufions, that it becomes necessary, efpecially in a new and fingular cafe, to inquire whether there may not exist fome particular exceptions to the general rule; or whether it may not be poffible that air, faturated 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 univerfally that, on the admixture of nitrous air with any kind of mephitic or perfectly noxious air, no diminution will be produced; it does not neceffarily follow that the converse of this propofition must be likewise univerfally true; or that, in every cafe whatever, when no diminution is obferved, the air expofed to the nitrous teft muft neceffarily be mephitic or perfectly noxious. It was till lately univerfally believed that air, in which a candle would burn, was whole fome and fit for refpiration. Dr. Prieftley has however difcovered one remarkable exception to this general and long established test of the purity of air. He has, by more than one procefs, reduced nitrous air into fuch 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 [See particularly his Obfervations on Air, vol. iii. pag. 132, &c.]
We fhall only relate fome of the refults of another clafs of the Author's experiments, made with a view to ascertain the effects of the effluvia arifing from moist and marshy foils upon air; and which are known to be the fource of the most dangerous putrid difeafes.
Two ounces of black mud, taken from a ftinking morals at York, occafionally overflowed by a brook, being put into an 8 ounce vial of air, affected it fo in 12 hours as to reduce it, according to the teft of nitrous air, from about 60° or 62° to 34° or 36°. When this mud was made perfectly dry, fo as to be reduced to a powder; it affected the air which was expofed to it fo little, that the diminution, in feveral experiments, proceeded only from 62 to 60°.-But the very fame powder being again reduced to the confiftence of mud, by the addition of a little
was inftantly 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 prefent Article, not choosing to take fuch liberties with a moufe, as with his own proper person, infpired this air more than once, through a bent tube of a large bore; but was not fenfible of any inconvenience, nor did he perceive any thing particular in it. No ftrefs, 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 inclofed in a fimilar vial of air, affected the latter fo far as to reduce the diminution from 62° to 49°; and on ftanding longer, the diminution was reduced from 62° to 29°. Again, when more water was added to this mud, so as to swim to a confiderable height above the powder, after the latter had fubfided, the air again tried by the teft was in no inftance found to produce a greater reduction of the diminution than from 62° to 56°.
The refults of these and other experiments, which we omit, correfpond with the observations of Sir John Pringle, and other practical medical writers; who have remarked that the diseases peculiar to low and marthy fituations feldom begin to appear, till the water is fo far evaporated, as to leave a black and flimy mud; that thefe difeafes ceafe when the bogs and marshy grounds have been drained, and are become perfectly dry;-and that, on the other hand, the danger arifing from marshes and bogs, is, in a great measure, obviated, on their being laid wholly under water. In this laft cafe, the Author obferves that the putrid fermentation is either prevented by too much moisture; or the effluvia are absorbed in paffing through the fuperincumbent bed of water.'
Article 9. Obfervations on the Population and Difeafes of Chester, in the Year 1774. By J. Haygarth, M. D.
This paper contains fome judicious and useful observations, which are fucceeded by feveral accurate tables of mortality, difcafes, &c. The moft ftriking of the Author's remarks relates to the very uncommon healthiness of the city of Chefter. In one of these tables, the Author has collected from different writers 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 Chefter. 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 perfon in 5;-at Vienna, 1 in 191;—at London, 1 in 204;—at Edinburgh, 1 in 20, &c. We omit the ratio of deaths in other large towns, and proceed to Manchester, the last and healthieft fet down in this table, where the proportion is 1 to 28. It appears, too, that the healthinefs of the city of Chefter, within the walls, exceeds even that of any of the country parishes fet down in the abovementioned table; where we find that in the Pais de Vaud, and fome country parishes in Brandenburgh, there dies 1 in 45. The highest number here given is 1 in 54, oppofite to Stoke Damerel, in Devonshire.
The causes of this fingular degree of healthinefs in Chester may, perhaps, be partly afcertained, by attending to some peEe 3 culiarities
culiarities in its fituation and ftructure, which the Author ac-
Article 5. A Cure of a Mufcular Contraction by Electricity. By Miles Partington, in a Letter to William Henly, F.R.S. The fubject of this extraordinary, and feemingly indifputable, cure, effected by electricity, was a Mifs Lingfield, who, in confequence of a cold contracted above two years before, was feized with a violent pain in the back of her head, which terminated in an obftinate contraction of the muscles of her neck, by which it was drawn down over her right fhoulder. The back part of it was twifted fo far round, that her face turned obliquely towards the oppofite fide, by which deformity fhe was difabled from feeing her feet, or the fteps as the came down stairs.'On the other fide, fhe felt a continual and fometimes violent pain, occafioned by the extreme tenfion of the teguments, &c. on that fide. She was fubject to frequent febrile attacks; and was fometimes flightly paralytic. Notwithstanding all the endeavours of the faculty to procure her relief, the little alteration obfervable in her diforder was rather on the unfavourable fide.
Mr. Partington firft infulated and electrified her on the 18th of February; drawing ftrong 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 9th. Some amendment was perceived after the first trial; and fome advantage was evidently gained on each repetition. In confequence of particular circumftances, the procefs 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 fides of the neck, during ten minutes; and likewife generally added two shocks from a bottle containing 15 fquare inches of coated furface fully charged, through her neck and one of her arms, croffing the neck in different directions.
Article 15. Sundry Papers relative to an Accident from Lightning at Purfleet, May 15, 1777;-particularly new Experiments and Obfervations on the Nature and Use of Conductors. By Benjamin Wilfon, F. R. S. &c.
The accident which befel the house built for the occafional accommodation of the Board of Ordnance at Purfleet is, in general, well known to our philofophical Readers. This houfe was furnished with a pointed conductor; at the diftance of 46 feet from the point of which, a corner of the building received fome damage from a flash of lightning, which ftruck off a piece of stone, and one brick, and loofened a few other bricks; which it removed less than half an inch from their places. This damage, fmall 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 oppofed the erection of this and other pointed conductors at Purfleet, was led, on the prefent occafion, to make the experiments, the relation of which conftitutes the principal part of this long Article. An immense conductor was fitted up, at the expence of the Board of Ordnance, and suspended in the Pantheon; confifting 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 occafionally added to it 4800 yards of wire. A model of the Board-House at Purfleet was likewise conftructed, to which was occafionally annexed a pointed, or a blunt, conductor, and which by means of weights, &c. was made to pafs under the artificial cloud, with a determinate velocity, fuppofed to be equal to that with which thunderclouds in general move.-In his estimation of this velocity, however, we muft obferve that the Author has attended only to the real, and has overlooked what we may call the relative, or angular, velocity.
It is impoffible for us to give any fatisfactory account of the various experiments made with this magnificent apparatus; or of the Author's conclufions from several of them. It may be fufficient to obferve, that his inferences from them are drawn fo as to ftrengthen his former opinion with respect to the danger of employing elevated conductors, armed with pointed wires; on a fuppofition that they invite the lightning. They will not however, we apprehend, appear fo fatisfactory to others as they appear to the Author.
The firing of gunpowder by this apparatus, by the electric aura or blaft, without a fpark, or the affiftance of the Leyden charge, is perhaps one of the most notable effects produced by it. Upon a ftaff of baked wood a ftem of brafs 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 fomewhat 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 (unbruifed) the wire of communication with the well' (i. e. the earth)
was then fastened to the bottom of the brafs ftem. Being fo circumftanced, and whilft 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 fo near to the drums as frequently to touch the metal. In this fituation, a small faint luminous ftream was obferved between the top of the cartridge and the metal drum.
Sometimes this ftream would fet fire to the gunpowder at the inftant 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 circumftances; for any the leaft 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 ftream ' of the matter of lightning, furely merits the most serious attention; and more especially in thofe cafes where pointed conductors are fixed to fecure magazines of gunpowder from fuch accidents.'-Tinder was ftill more readily fired by the electric
Instead of giving any opinion of our own on the Author's experiments, and deductions from them; it will be more fatiffactory to our Readers if we give that of the Committee appointed by the Royal Society, to confider of the most effectual method of fecuring 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 obfervations of Mr. Wilson, and having maturely confidered the fubject at large, it is their opinion that it is very improbable that the powder magazines, guarded in the manner in which they are at prefent, that is, with elevated pointed conductors, fhould receive any damage from lightning. They even recommend to the Board of Ordnance the erection of feveral additional rods, as acutely pointed as poffible, on the roofs and fome other parts of each of the magazines; and, for the fake of greater fecurity, they propofe that the intire roofs and the tops of the end walls fhould be covered with lead connected with the faid rods. They propofe thefe and other directions, under a perfuafion that elevated rods are preferable to low conductors terminated in rounded ends, knobs, or balls of metal ;'-and that the experiments and reafons,