Imatges de pÓgina

be difcerned in them. These three fered, however, confiderably in {pots are plainly to be distinguish. magnitude and brightness; for the ed from the rest of the inarrs upon vulcano of the year 1783, though the moon; for the reflection of the much briglicer than that which is fun's rays from the earth is, in its now burning, was not nearly lo prefent lituation, fufficiently bright large in the dimensions of its erupwith a ten-feet reflector, to niew tion: the former seen in the te. the moon's spots, even the darkeit leicope resembled a ítar of the of them : nor did I perceive any fourth magnitude as it appears to fimilar plıænomena lait lunation, the natural eye; this, on the conthough I then viewed the same trary, thews a visible disk of kro places with the famie instrument. minous matter, very different from

“ The appearance of what I the sparkling brightness of itarhave called the actual fire or erup- light. tion of a volcano, exally resem- P. S. M. Méchain having fa. bled a small piece of burning char- voured me with an account of the coal, when it is covered by a very discovery of his coinet, I looked thin coat of white ashes, which fre- for it among the Pleiades, quently adhere to it when it has ing its track lince the oth of this been some time ignited; and it had month to lie that wiy; and saw it a degree of brightneís, about as April 19th, at 10 h. 10' fidereal Itrong as that with which such a time, when it preceded Fl d coal would be seen to glow in faint Pleiadum about st" in time, with daylight.

nearly the fame declination as that All the adjacent parts of the flar; but no great accuracy was volcanic mountain seemed to be attempted in ibe determination of faintly illuminated by the eruption, its place. As I have mentioned and were gradually more obscure the comet in a foregoing paragraph as they lay at a greater distance of this paper, I thought it proper from the crater.

here to add my oblervation of ir. This eruption resembled much " The cornet is ne.rly round, with that which I saw on the 4th of a small tail towards the north May, in the year 1783 ; an ac- fullowing part: thc chevelure count of which, with many remark- " extends to about four or five able particulars relating to vulca- cu minutes ; and it has a central, nie mountains in tue moon, I Mall “ very small, ill.defined nucleus, take n erts opportunity of com- " of no great brightness." municating to this fociety. It dif

EXPERIMENTS on the MÕISTURE absorbed from the ATMO.


[From the fame Work.] EING engaged in a course of with respect to heat, and particu


ducting powers of various bodiesmoniy made use of for cloathing,

in order to see if I could discover hours, upon a table placed in the any relation between the conuucting middle of a room, the air of the powers of those subitances, and roum being at the temperature of their power of absorbing moisture 45° F.; atter which they were carefrom the atmosphere, I made the fully weighed (in the room and following experiments.

were found to weigh as under men“Having provided a quantity of tioned. each of the undermentioned sub- " They were then removed into itances, in a state of the moit per- a very damp cellar, and placed upfect cleanness and purity, I exposed on a table, in the middle of a vault, them, spread out upon clean China- where the air, which appeared by plates, twenty-four hours in the the hygrometer to be completely dry air of a very warm room (which faturated with moisture, was at the had been heated every day for fe- temperature of 45° F. ; and in this veral months by a German stove), situation they were suffered to rethe last fix hours the heat being main three days and three nights, kept up to 85° of Fahrenheit's the vault being hung round, during thermometer; after which I entered all this time, with wet linen cloths, the room with a very accurate ba- to render the air as damp as puttible, lance, and weighed equal quantities and the door of the vault being of thele various subítances, as ex

shut. prefled in the following table. " At the end of the three days I

“ This being done, and each entered the vault, with the balance, fubftance being equally spread out and weighed the various fubitances upon a very clean China plate, they upon the ipot, when they were were removed into a very large un- found to weigh as is expressed in the inhabited room upon ihe second third column of the following table. door, where they were exposed 48

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N.B. The weight made use of tract the watery vapour diffolved in in these experiments was that of the air with the greatest force. Cologne, the parts or leatt divisions " Perhaps the apparent dampness being = risto part of a mark, con- of linen, to the touch, arises inora fequently 1000 of these parts make from the case with which that subabout 52 grains of Troy.

fance partswith the water it contains, 6 I did not add the filver wire to than from the quantity of water it the bodies above mentioned from actually holds : in the same manany idea that that substance could ner as a body appears hot to the possibly inbibe muisture from the touch, in consequence of its parting atmosphere; but I was willing to freely with its heat, while ano her see whether a metal, placed in air body, which is actually at the same faturated with water, is not capable temperature, but which witholds of receiving a small addition of its heat with greater obftinacy, afweight from the moitlure attracted feets the sense of feeling much less by it, and attached to its furface; violently. from the result of ihe experiment, " It is well known, that woollen however, it Thould seem that no clothes, such as flannels, &c. worn such attraction sublists between the next the tkin, greatly promote in. metal I made use of, and the watery sensible perfpiration. May not this vapour diffolved in air.

arise principally from the strong " I was totally mistaken in my attractiçn which subfilts between conje&tures relative to the results of wool and the watery vapour which the experiments with the other sub. is continually itluing from the hu. ftances. As linen is known to at. man body? tract water with fo inuch avidity; “ That it does not depend entireand as, on the contrary, wool, hair, ly upon the warmth of that coverfeathers, and other like animal sub. ing, is clear ; for the fame degree Itances, are made wet with so much of warmth, produced bv wearing difficulty, I had little doubt but more clothing of a different kind, that linen would be found to attract does not produce the same effect. moisture from the atmosphere with " The perfpiration of the human much greater force than any of those body being absorbed by a covering fubilances ; and that, under fimilar of Aannel, it is immediately difiricircumstances, it would be found to buted through the whole thickness contain much more water: and I of that substance, and by that means was much confirmed in this opinion exposed by a very large surface to upon recollecting the great difter, be carried off by the atmosphere; ence in the apparent dampels of and the loss of this watery vapour, linen and of woollen clothes, when which the flannel fustains on the they are both exposed to the fame one tide, by evaporation, being atmosphere. But these experiments immediately restored from the other, have convinced me, that all my fpe- in consequence of the strong attrac. culations were founded upon erro- tion between the flannel and this neous principles.

vapour, the pores of the skin are, " It Mould feem, that those be- dilencumbered, and they are contidies which are the most easily wet, : nually surrounded by a dry, warm, or which receive water, in its une and falubrious atmosphere. elastic form. with the greatea eale, " I am astonished, that the cusare not those which in all cases üle tom of wearing flaunel next the skin

should not have prevailed more uni. I have said, or donc, upon the verially. I am confident it would subject, should induce others to prevent a multitude of diseases; make a trial of what I have so long and I know of no greater luxury experienced with the greate: ada than the comfortable sensation vantage, and which, I am confident, which arises from wearing it, espe- they will find to contribuie greatly cially after one is a little accustomed to health, and confequently to all to it.

the other comforis and cnjoyments “ It is a mistaken notion, that it of life. is too warm a cloathing for summer. " I Mall then think these expe. I have worn it in the hottest cli. riments, trifling as they may appear, mares, and in all seasons of the by far the moít fortunate, and the year, and never found the least in- most important ones I have ever convenience from it. It is the made. warm bath of a perspiration con- " With regard to the origina! fined by a linen fhirt, wet with object of these experiments, the sweat, which renders the summer discovery of the relation which I heats of southern climates fo insup- thought might possibly fublitt beportable ; but flannel promotes per- tween the warmth of the sub{piration, and favours its cvapora- ítances in qucition, when inade uso tion; and evaporation, as is well of as clothing, and their powers known, produces positive cold. of attracting moisture from the at.

I first began to wear flannel, mosphere ; or, in other words, benot from any knowledge which I tween the quantities of water they had of its properties, but merely contain, and their conducting pown upon the recommendation of a very ers with regard to heat; I could able physician (fir Richard Jebb); not find that these properties de and when I began the experiments pended in any manner upon, or of which I have here given an were in any way connected with, account, I little thought of dif- each other. covering the physical cause of the " The result of my experiments good effects which I had experienced upon the conducting powers of these from it; nor had I the most distant fubitances, I reserve for a future idea of mentioning the circumstance. communication.' I Mall be happy, however, if what

On the PRODUCTION of BORAX. In a Letter from WILLIAM



(From the fame Work.] Y journey to the northern informed of, the production and

mountains in January last, manufacture of borax. The place in attendance upon the vizier, gave which his excellency visited is called me an opportunity of fatisfying, in Betowle, and is a small principality some degree, my curiofity on the in the first of the northern mounsubject you are so defrous of being tains, where they rise from the 1787


plains plains of Hindostan, and is distant into small reservoirs, by raising it from Lucknow about two hundi ed into banks about fix inches bigh ; miles N. E. The town is a prin- when these are filled with snow, the cipal mart, where the cominoditics hot water from the lake is thrown of the mountains are exchanged for upon it, which, together with the those of the plain. The raja, or water from the melted snow, remains prince of the country, holds his in the reservoir, to be partly abpiflessions in the hills as an inde- sorbed by the earth, and partly pendent fovereign ; but for those un evaporated by the fun ; aiter which the plain he owes fealty, and pays there remains at the bottoin a cake tribute to the vizier. He there- of fometimes half an inch thick, fore embraced this opportunity of of crude borax, which is taken up paying homage in perfon to bis lord. and reserved for use. It can only During his stay at court, I had an be made in the winter season, beopportunity of making the enquis caute the falls of Inow are indispenries I withéd from his people, and fably requisite, and also because particularly from his dewan or mi- the 'saline appearances upon the nifer, who had with him some of earth are strongest at that season. the inhabitants of the place where When once it has been made upon the borax is made.

any ipot, in the manner above de. “ This faline substance, called in fcribed, it cannot be made again the language of this country fwa. upon the same place, till the snow gah, is brought into Hindollán from hall have fallen upon it and disthe mountains of Tibbet. The folved three or four times ; aiter place where it is produced is in the which the fa'ine efflorescence rekingdom of Jumlate, distant from appears, and it is again fit for the Betowle about thirty days journey operation. north. Juinlate is the largest of 6. The borax in the fate above the kingdoms in that part of the described, is transported from bill Tibbet mountains, and is considered to hill upon goats, and paties through as holding a superiority over all the many ditterent hands before it reít.

reaches the plains, which increases “ The place where the borax is the difficulty of obtaining authentic produced is described to be in a information regarding the original finall valley, surrounded with snowy manufacture. When brought down mountains, in which is a lake, about from the bills, it is refined from the fix miles in circumference, the wao caith and grofs impurities by boil. ter of which is constantly hot, so ing and crystallisation.

I could much so that the hand cannot be obrain no answers to any question held in it for any time. The ground regarding the quality of the water, round the banks of the lake is per- and the mineral productions of the testly barren, not producing even foil. All they could say of the a blade of grifs; and the earth is former was, that it was very hot, tull of a faline master in such plenty very foul, and as it were greasy; that, after fulls of rain or inow, it that it boils up in many plices, and concretes in white takes upon the has a very offensive imell: and the surface, like the natron in Hindof- latter remarkable only for the faline

Upon the banks of this lake, appearances above described. That in the winter scaton, when the falls country, however, in general, proof inow begin, the earth is formed duces coliderable quantities of iron,



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