Imatges de pÓgina

der proceeds to its maximum, the hygroscope moves from 80 to 100, and sometimes a little farther. Then we have also a certain proof that extreme moisture exists in the air ; for every solid body exposed to it is wet. But it is only in that moment we can depend on extreme moisture existing; for, if in the other described stages of the phænomenon, the appearance of water on the surface of some folids has proceeded from a spontaneous precipitation in the air, all the other solids ought to have been wet; but they only become wer in a certain succession, and in the mean time the Rip of quill, and all the other above mentioned hygroscopes, move more and more towards their point 100, in sign of moisture increasing in the air. Confequently (as I had concluded from my first observations), inAtead of having in dew an hygrojcopic standard for the bygrometer, we have in its phænomena many circumstances which will only be explained with the assistance of that instrument.'

The general conclusion is,

• The maximum of evaporation in a mass of inclosed air is far from being identical with the maximum of moisture; this being dependent also, even to a very great degree, on the temperature of the space, supposed to be the fame, or nearly so, as that of the wa. ter which evaporates in it. Moisture may arrive to its extreme in an inclosed air, if that common remperature is near the freezing point; but it becomes less and less, even to a very dry state, as that temperature rises, though the product of evaporation, thereby increafing, continues to be at its different maxima, correspondent to the diferent temperatures.'

The different claffes of hygroscopes are either slips or threads; in other words, laminæ cut across the fibres of animal or vegetable substances; or these substances divided lengthways. The former are most steady in their march, for the latter, as analogous to the twisted strings, are found to be anomalous in their motions, and shortened by the moisture which at other periods lengthens them. The rest of the paper relates to the formation of hygrometrical scales, and the different marches of flips and threads. Like many of M. de Luc's works, it is too copious. It is needless to relate experiments which have failed; ideas, which been given up; and fancies which a little retlection has shown to be visionary. On the whole, those who have read our author's former work, and M. de Saussure's elrays, will not think that much is added to our knowledge of laygrometry from the lucubrations before us.

Art. II. On the Production of Ambergris. A Communieation from the Committee of Council appointed for the Confideration of all Matters relating to Trade and Foreign Plantations; with a prefatory Letter from William Fawkenex, Esq.


to Sir Joseph Banks, Bart. P.R.S.—Three hundred and fixty two ounces of ambergris were found in one whale, and it is certainly the cause or effect of disease. Cow whales are chiefly found in low latitudes, where they seemingly go to calve. Whales, our author tells us, often are seen in scools; he has • seen from 15 to perhaps 1000 together.' This ambergris was sold for nineteen Ihillings and nine pence per ounce: about one half was bought for exportation to Turkey, Germany, and France.

Art. III. Obfervations on the Affinity between Basaltes and Granite. By Thomas Beddoes, M. D.; communicated by Sir Joseph Banks, Bart. P. R. S. – Dr. Beddoes, we think, fails in almost every step of his proof. He sees granite in every stone, where he can discern mica and feld spar, and where, as in one instance, he fancies that he perceives quartz (note to p. 51.) In general, he does not advert to the slight connection between lavan and basaltes; the real difference between stones, compounded of mica, &c. where black and whice shining spots are discernible, and the true compacted granites; between pieces of real granite, accidentally combined with tufa or lava, and this substance in a fused state. These different circumstances will, in general, explain the approximations which our author has adduced; though it would have been fufficient to have observed, that Dr.Beddoes' ideas seem to have been taken wholly from specimens : he appears never to have examined granite, basaltic or volcanic countries, and sometimes not to have attended with sufficient accuracy to descriptions. He would not surely, unless blinded by his eagerness in the pursuit of an hypothesis, have told us that, in the usual situations, basaltes takes the place of granite, supporting fuccellively fchiftus and limestone? Basaltes are often found, particularly in the Giant's Causeway, and in some of the basaltic countries in Germany, refting on limestone. If our author would attend to Sauffure's Travels, and Dolmieu's Memoir, in a late volume of the Journal de Physique *, he would find that much the greater part of his doctrine, and of course of his conclusions, was visionary,

Art. IV. Nebulous Stars, properly so called. By William Herschell, LL.D.F.R.S.-The apparent nebulæ, resolvable by good telescopes, were found to consist of the accumulated light of fixed stars, and it was no unprobable supposition, that the more diftant ones were of the same kind. Numerous phænomena have, however, occurred to our very able and enterpriGng observer, to render this conclusion doubtful. In many inftances, the star has been in the center, and the nebulofity

* Shortly noticed in our Foreign Intelligence of last month.

O 3


around it fo diluted, faint, and equable, that he hesitates not to suppose it luminous matter connected with the flar, collected perhaps from myriads of rays darted into the vast expank, and designed probably for the formation or regeneration of a sun. This vast and fublime idea is highly interesting, and fills the mind with the most awful views of a superintending providence. Yet, though the object is specious, we must be allowed to hesitate; and, as it is a well founded rule in philosophy, to admit of no other causes for phænomena than are neceílary, we may be allowed to suggest, that it is poslible, on a starry ncbulosity, too distant to be resolvable, to have by accident'a star in the line drawn from the center to the eye, as there are certainly stars which coincide with other points of a diftant nebula. Thefe nebulous stars also are the very small ones; and we suspect, that even Mr. Herschell's skill cannot determine, in such valt distances, that the one is equally near with the other. Let us attend, however, to his conclusions,

• But what a field of novelty is here opened to our conception ! a shining fluid, of a brightness fufficient to reach us from the remote region of a ftar of the 8th, 9th, Toth, 11th, or 12th, magnitude, and of an extent so conliderable as to take up 3, 4, 5, cr 6 minutes in diameter! Can we compare it to the corufcations of the electrical fluid in the aurora borealis ? Or to the more mgnificent co ne of the zodiacal light, as we see it in spring or autumo? The latter, notwithstanding I have observed it to reach at least go degrees from the sun, is yet of so little extent and brightness as probably not to be perceived even by the inhabitants of Saturn or the Georgian planet, and must be utterly invisible at the remoteness of the nearelt fixed star.

• More extensive views may be derived from this proof of the existence of a shining matter. Perhaps it has been too hastily furmised that all milky nebulofit', of which there is so much in the heavens, is owing to starlight only. These nebulous stars may ferve as a clue to unravel other mysterious phenomena. If the shining fluid that surrounds them is not so effentially connected with thele nebulous itars but that it can aifo exist without them, which . seems to be sufficiently probable, and will be examined hereafter, we may with great facility explain that very extensive, telescopic nebulosity, which, as I mentioned before, is expanded over more than fixiy degrees of the heavens, about the contellation of Orion ; a luminous matter accounting much better for it than clustering ftars at a dittance. In this case we may also pretty nearly guefs at its ficuation, which mult commence somewhere about the range the fars of the 7th magnitude ; or a little farther from us, and extend unequally in some places, perhaps to the regions of those of the gth, roth, 11th, and 12th. The foundation for this surmise



is, that, not onlikely, some of the fixed stars that happen to be fituated in a more condensed part of it, or that perhaps by their own attraction draw together some quantity of this fuid, greater than what they are intitled to by their situation in it, will, of course, assume the appearance of cloudy stars; and many of those I have named are either in this itratum of lumincus matter, or very near it.

* We have said above, that in nebulous stars the existence of the thining Auid does not seem to be so effentially connected with the central points that it might not also exist without ther. For this opinion we may allign leveral reasons. One of them is the great resemblance between the chevelure of these stars and the diffused extensive nebulofity mentioned before, which render it highly p:0. bable that they are of the same nature. Now, if this be admit. ted, the separate existence of the luminous matter, or ils“ independence on a central ftar, is fully proved. We may also judge, very confidently, that the light of this shining fluid is no kind of reflection from thé ítar in the center; for, as we have already obferved, reflected light could never reach us at the great distance we are from fuch objects. Besides, how impenetrable would be an atmosphere of a fufficient density to reflect so great a quantity of light? And yet we observe, that the ouiward parts of the chevelure are nearly as bright as those that are close to the Itar; lo that this supposed atmosphere ought to give no obstruction to the passage of the central rays. If, therefore, this matter is felf-luminous, it seems more fit to produce a star by its condensation than to depend on the star for its existence.'

On the whole, in whatever light we view the subject, it must lower the pride of grovelling terrestrial mortals, who think the universe their own, and dare to dictate to the unie versal Lord what he ought to do, or explain minutely what he has done.

Art. V. Abstract of a Register of the Barometer, Thermometer, and Rain, at Lyndon in Rutland. By Thomas Barker, Efq. with the Rain in Hampshire and Surrey; for the year 1789. Communicated by Thomas White, Efq. F.R.S.The thermometer was from 78 to 131 ; the mean heat of April 48. The barometer from 30.25 to 28; each cecurring in January. The rain at Lyridon was 28.002 ; at Selborne 42.00; at Fyfield 35.61 inches. Our author compares the cold of the winter 1740 with the present, and finds the effect of the former more considerable ; but, in the influence on vegetables, he does not advert to the previous wet autumn of 1739. Fish were less commonly killed in ponds in 1740, which he very properly attributes to this cause.


Art. VI.

Art. VI. Observations on certain horny Excrescences of the human Body. By Everard Home, Esq. F.R.S.-Our author's list of these phenomena is very incomplete; and he attributes horn to an extraordinary and superfluous effort of nature to extend the cuticle over a wound. The gritty substance found in the previous swelling, from the bottom of which the horn usually rises, he does not explain. The subject is yet very little understood ; and it is first necessary to enquire what the nature of this horny substance is, and how it is connected with the bones. Our author has not facts sufficient before him; nor is it, for this reason, surprising that his difquisition ends in words.

Art. VII. Considerations on the Convenience of measuring an Arch of the Meridian, and of the Parallel of Longitude, having the Observatory of Geneva for their common Interfection. By Mark Augustus Pictet, Professor of Philosophy in the Academy of Geneva ; in a Letter to Sir Joseph Banks, Bart. P. R. S.-The polar and equatorial diameters of the earth, as ascertained by different mensurations of a degree of the meridian, differ greatly. These numbers are so distant as it, and yo for the difference between the two diameters; and we now know that many irregularities must have arisen from the hygroscopic or pyrometrical affinițies of the substan. ces employed to measure the base. Since general Le Roy's experiments, in the late attempt, greater accuracy will be at, tained. It is necessary, however, to proceed anew with the mensuration ; and M. Pictet gives many reasons, generally sa. tisfactory ones, for preferring the neighbourhood of Geneva for the operation. He proposes to 'measựre 84" of the arch, and the parallel of longitude eastward.

• The re-union of the two measurements (of latitude and lon. gitude) in the same spot, is an advantageous circumstance; and the more so, if we consider that this spot lies between the 45th and 46th degree, that is, in the mean latitude between the pole and the equator, near which latitude the mean radius of the earth takes place in the well founded supposition of its being a spheroid. This radius, found by the most accurate measurement hitherto attempted, would become a standard, and to which the results of the equatorial and northern measurements being compared, the true figure of the earth would be the better ascertained.

• The pofition or relative longitude of the meridian of Geneva is well determined by a great number of observed immersions and emerfions of the satellites of Jupiter, and by some ocultation of fars by the moon. These observations were performed by the late profeffor J. H. Mallet, Mr. J. Trembley, and myself. The greater part of them are already calculated, and their mean result



« AnteriorContinua »