Art. XXX. On a new Method of preparing a Teft Liquor to fhew the Prefence of Acids and Alkalies in chemical Mixtares. By Mr. James Watt, Engineer. Every person has, in their turn, been deceived by the tefts for alkalies, though the changes, from the prefence of acids, have been fufficiently decifive. Phlogifticated nitrous acid, with an alkali, by the teft of litmus, will appear acid, when other tests determine it to be alkaline. This ambiguity may lead the chemift into many errors; and it is of ufe, therefore, to be informed, that an infufion of the leaves of the common red cabbage, was very fenfible in the changes of colour, both from alkalies and acids; and not liable to be influenced by the presence of phlogifton. Mr. Watt advises chemists, to preserve them by means of acids, and, when they are ufed, to neutralize the acid by means of chalk or fixed alkali. He afterwards found,

that, in hot weather, fpirits of wine were neceffary to prevent moulding. Since reading this paper, we have found cloves equally useful; and they have preferved the liquor, without any other addition, in the late warm weather; but perhaps the heat has not yet been great enough, to give this method a fair trial.

Art. XXXI. An Account of a new Plant of the Order of Fungi. By Thomas Woodward, Efq.--We fhould prefer forming a new genus for this peculiar plant, at least till it has been more accurately examined: it is however nearly allied to the lycoperdon. It has not been before noticed, becaufe its growth is very rapid, and its volva generally buried from fix to eight inches in the earth. Plants have been found in a decaying state, where, the day before, there had been no appearance of any; and it has fince appeared probable, that they fometimes come to perfection, before they rife above the furface.

Art. XXXII. Experiments to investigate the Variation of Local Heat. By James Six, Efq.--In our fifty-fifth volume, page 361, we explained the conftruction of Mr. Six's thermometer, and then objected to it, that the refiftance of the index, with the neceffary bulk of the fpirits, would diminish its fenfibility. It must be owned, however, that the force of thefe objections is leffened when it is afed in comparative experiments; we do not think that they are entirely removed. Mr. Six, as ufual, found, that the heat diminished as the thermometers were raised from the earth during the day time; but, in the night, the order was frequently reverfed. The ftate of the atmosphere was found to influence this change; for when the fky, during the night, was dark and cloudy, all the thermometers agreed very nearly with each other. In the day time, the variation, at different heights, feemed not to be. VOL. LX. July, 1785. affected

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affected by the state of the air, except as it was cold or hot. In the cold weather it was lefs obfervable. It is not allowable to enter on long difcuffions; but if Mr. Six reflects on the folvent power of the air, or rather, to avoid difputes, on the effects of evaporation, combined with those of the heat reflected from the earth, the greater number of appearances will be explained. He fhould confider too, that air is a bad conductor of heat, and that his thermometers are not fo eafily affected as the smaller inftruments; confequently, a little variety will arife from their being fixed to a large body, or fufpended in the open air.

Art. XXXIII. Account of fome Obfervations tending to inveftigate the Conftruction of the Heavens. By William Herschel, Efq. F. R. S.-Mr. Herschel has now applied a new telescope of confiderable powers, though weaker than one he defigned to conftruct, to the more diftant fixed ftars. It was always prefumed that the nebulæ and milky-way were clusters of stars, because the better our inftruments were, the more clearly we perceived the bodies of which fome of the nebula were compofed. This powerful telescope has feparated many of these clusters into their component ftars; and the milkyway appears, through it, to be of the fame kind. From an actual enumeration of fome fields of view, Mr. Herschel computes that a belt of 15° long and 2o broad cannot contain lefs than fifty thoufand ftars, which may be diftinctly counted. Befides this astonishing number, our author has difcovered four hundred and fixty-fix new nebula, which, fo far as we know, have not yet been seen by any other perfon.

The attempt to investigate the conftruction of the heavens is of an aftonishing magnitude. We entered on it with doubt and hesitation, and we now follow our author's steps with refpectful timidity. It is the privilege of genius to express its fublime conceptions in a clear, comprehenfive, and peculiar language; fo that, from the difficulty of the fubject, and the want of diagrams, we almost despair of conveying any accurate. idea of Mr. Herfchel's obfervations. But, we fhall make the attempt. A flight reflection will convince us, that the spherical appearance of the heavens is an optical deception; and that the stars are more properly fcattered indiscriminately, or arranged in an order very different from that in which we perceive them. Mr. Herfchel feems to affume it as a position, that they are arranged in ftrata, and then examines how far this opinion agrees with the appearances. If a number of stars are arranged between two parallel planes indefinitely extended, but at a given confiderable distance from each other, an eye placed any where within it, will fee the stars in the direction

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of its length and height, with all those in the intermediate fituations projected into a great circle. This exacly agrees with the appearance of the milky-way, and Mr. Herfchel thinks it highly probable that the fun is in the fame ftratum, But, if a fmaller ftratum interfect the great one, the eye, at no great distance from the point of interfection, will fee the smaller stratum as a lucid branch; fo that it is probable this great ftratum is interfected by another, and that our fun is in a part of it not far distant from the point of interfection. This is confirmed by what our author calls a star-gage; for he, who talks of collecting bundles of stars of two or three hundred at a time, and ⚫ offering them to the Royal Society,' may be allowed to affume the rule, and gage the heavens. In the parallel from 92° to 94' north polar distance, and 15h 10' right afcenfion, the ftar-gage runs up from 9.4 ftars in a field of view to 18.6. But in the parallel from 789 to 80°, and right afcenfion 11, 12, 13, and 14", from 3.1 it feldom rifes above 4. We just now obferved, that, in this stratum, those stars which are in the direction of the length and height of the plane, with those in the intermediate fituations, appear in the form of a great circle; thofe in the direction of its fides neceffarily appear to be scattered without any particular arrangement. From this it feems to follow, that the milky-way, and the distinct stars of different magnitudes belong to the ftratum, or perhaps more properly fpeaking, the groupe to which the fun belongs. We are by no means clear refpecting Mr. Herfchel's opinion of the other ftrata; in one paffage he seems to confider each nebula as a diftinct ftratum.

'If the eye were placed fomewhere without the ftratum, at no very great distance, the appearance of the stars within it would affume the form of one of the lefs circles of the sphere, which would be more or less contracted to the distance of the eye; and if this distance were exceedingly increased, the whole ftratum might at laft be drawn together into a lucid spot of any thape, according to the pofition, length and height of the ftra

tum.'

In another paffage, he is rather inclined to think the ftrata formed of groupes of nebule; and this feems by much the most probable opinion.

A very remarkable circumftance, attending the nebule and clusters of fears is, that they are arranged into ftrata, which feem to run on to a great length; and fome of them I have already been able to purfue, fo as to guefs pretty well at their form and direction. It is próbable enough, that they may fur-. round the whole apparent sphere of the heavens, not unlike the milky-way, which undoubtedly is nothing but a ftratum of

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fixed ftars. And as this latter immenfe ftarry bed is not of equal breadth or luftre in every part, nor runs on in one straight direction, but is curved and even divided into two streams along a very confiderable portion of it; we may likewife expect the greatest variety in the ftrata of the clusters of stars and nebulæ. One of these nebulous beds is fo rich, that, in paffing through a fection of it, in the time of only thirty-fix minutes, I detected no less than thirty-one nebulæ, all diftinctly visible upon a fine blue sky. Their fituation and shape, as well as condition, feem to denote the greatest variety imaginable. In another ftratum, or perhaps a different branch of the former, I have feen double and treble nebulæ, variously arranged; large ones with fmall, feemingly attendants; narrow but much extended, lucid nebulæ or bright dafhes; fome of the shape of a fan, refembling an electric brufh, iffuing from a lucid point; others of the cometic fhape, with a feeming nucleus in the center; or like cloudy ftars, furrounded with a nebulous atmos phere; a different fort again contain a nebulofity of the milky kind, like that wonderful, inexplicable phenomenon about 0 Orionis; while others fhine with a fainter, mottled kind of light, which denotes their being refolvable into ftars.'

There are many other curious particulars in this paper, but we have already extended our account of it far enough.

Art. XXXIV. An Account of a new Species of the BarkTree, found in the Island of St. Lucia. By Mr. George Da vidfon,In the fixty-feventh volume of the Philofophical Tranfactions, p. 504. we received an account of a species of cincona, found in Jamaica. This feems very much to resemble it, fo far as we perceive from the imperfect description in that volume; and both are varieties of the Cincona Caribbæa of Linnæus, in the laft edition of the Species Plantarum. Its properties we had occafion to describe in our review of Dr. Kentifh's pamphlet, vol. lix. p. 15.

Art. XXXV. An Account of an Obfervation of the Meteor of August 18, 1783, made on Hewit Common, near York. By Nathaniel Pigott, Efq. F. R. S.-This is the fame meteor obferved by Meffrs. Cavallo, Aubert, Cooper, and Blagden, of which we have already given a full account.

Art. XXXVI. Obfervations of the Comet of 1783. By Edward Pigott, Efq.-This comet was observed the 19th of November, 1783. It had exactly the appearance of a nebula, and its light was very faint. Mr. Mechain, at Paris, difcovered it the 26th of November, feven days after Mr. Pigott's firft obfervation.

Art. XXXVII. Experiments on mixing Gold with Tin. By Mr. Stane by Alchorne, of his Majefty's Mint.-Dr. Lewis had obferved that the fmalleft proportion of tin and lead, or

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even their vapours, though they did not add weight enough to the gold, to be fenfible in the tendereft ballance, rendered it fo brittle, that it flies in pieces under the hammer. Mr. Alchorne has examined this fubject by experiment, and found that even one twenty-fourth part of tin did no very effential injury to the malleability of gold, and the fumes had no effect. The mixtures grew more hard and harsh, in proportion to the quantity of alloy; but not one of them had the appearance of what workmen call brittle gold. Mr. Alchorne therefore thinks, with great reason, that the brittleness arose from the impurity of the tin., Twelve grains of regulus of arfenic will deftroy the malleability of as many ounces of gold.

Art. XXXVIII. Sur un moyen de donner le Direction aux Machines Aeroftratiques. Par M. Le Comte De Galvez, -On the Means of directing Areoftatic Machines. By the Count of Galvez. The count of Galvez having communicated to us his ideas on the means of directing areostatic machines at pleasure, by a certain rhumb-line in the air, founded on different obfervations on the ufe which birds make of their wings in flying, and fishes of their fins and tail when they fwim,- We the undersigned certify' What? that

we failed on the canal of Manzanares in a boat with very little wind, by the help of moveable fails like wings. Adieu Meffrs, and, in return for your laborious certificate, and the very accurate plate which accompanies it,-may you receive a fuperior portion of difcernment, and a little more philofophical accuracy!

Art. XXXIX. An extraordinary Cafe of a Dropfy of the Ovarium, with fome Remarks. By Mr. Philip Meadows Martineau, Surgeon.-The quantity of water drawn from this poor woman was greater than that related to have been taken from lady Page. The whole was fix thousand fix hundred and thirty-one pints, or upwards of thirteen hogsheads. On an average, fhe might collect about two-thirds of a pint each day, and fometimes probably between two and three pints. She lived, in this ftate, twenty-five years, and was tapped 80 times. On diffection, all the parts were much thickened by the preffure; but generally found, except the left ovarium, which was the original feat of the disease, and was enlarged into an immenfe pouch.'

Art. XL. Methodus inveniendi Lineas Curves ex proprietatibus Variationis Curvaturæ. Pars fecunda. Auctore Nicolas Landerbeck, Matthes. Profeff. in Acad. Upfalienfi. This is the fecond part of the author's Method of find