Art. IX. Obfervations of a new variable Star. By John Goodricke, Efq.-Another variable ftar. This is B Lyræ, and its period is faid to be twelve days, nineteen hours. From the particular observations, it appears fomewhat lefs,

As Lyræ is a quadruped ftar, No 3, of Mr. Herfchel's fifth clafs of double stars. I was defirous to fee if any of the fmall ftars near it would be affected by its different changes; but they feemed not to fuffer any alteration, either when it was at its greatest or at its leaft brightnefs. I attended to this the more particularly because the loss of the ftar's light was very confiderable, and the phenomenon feemed to be occafioned by a rotation on the ftar's axis, under a fuppofition that there are feveral large dark spots upon its body, and that its axis is inclined to the earth's orbit.'.

Art. X. On the Motion of Bodies affected by Friction. By the Rev, S. Vince, A..-The object of this very ingenious author was to determine

"Ift, Whether friction be a uniformly retarding force.

zdly, The quantity of friction.

3dly, Whether the friction varies in proportion to the pref fure or weight.

6

4thly, Whether the friction be the fame on which ever of its furfaces a body moves.'

It is well known how much philofophers have differed on this fubject, and experiments have been scarcely more conclufive. Thofe of Mr. Vince are lefs exceptionable than many others, though fome doubts may ftill be raised. They are, however, inconfiderable; and his conclufions may be fafely looked on as a very near approximation to truth. In the first experiments it was found, that in hard bodies, friction really was an uniformly retarding force. When the bodies were covered with cloth, woollen, &c. the retarding force increased with the velocity; when covered with paper, it was again uniform. From the event of thefe experiments, the quantity of friction is eafily determined by the laws of motion.

To determine the third question, the experiments are very properly directed, and it appears very conclusively, that the quantity of friction increases in a lefs ratio than the quantity of matter, or weight of the body. This determination entirely decides the last queftion; for if the quantity of friction increases in a lefs ratio than the weight, there must be less friction on any given portion of the fmaller furface. But, as this opinion was very different from that generally received, it was put to the teft of experiment; and it appears very clearly that, with a given weight, the smallest furface has the leaft friction. Mr. Vince thence thews the fallacy of his predeceffors' experi

ments;

ments; and, as the proportional increase of friction, to the increase of weight, was different in different bodies, he purposes to examine the fubject by future experiments, to determine the law of the increase. The paper concludes with five propofitions to establish a theory on the former principles. Even to mention these more generally, would lead us too far. [To be continued.]

FOREIGN ARTICLES.

Hiftoire de l'Academie Royale des Sciences Année 1781, avec les Memoires de Mathematique & de Phyfique pour la même Annèe, Paris, 4to. 1784:

As

S we have lately added to our Journal an account of the more remarkable and useful foreign publications, it would be inexcufable if we omitted the public tranfactions of the Royal Academy, and the Royal Society of Medicine. The object of the former inftitution is well known; and though we now again refume it, after a long feries of fucceffive publications, yet we need not go back to explain its origin, or to trace its progrefs. We purpose to follow the academy in their enfuing volumes; and where it may be neceffary, fhall explain any particular fubject, by an account of what has been done in the former parts of this extenfive feries. The volume before us is not the laft; but accounts only of that published about a month fince, have reached England. We fhall not fail to attend to it as foon as we receive it.

In the department of General Phyfics, the first article is by M. Tillet, on the proportional Prices of Wheat, Meal, and Bread. This fubject indeed belongs rather to economics than to phyfics; and we need not enlarge on it, because though fome of the facts may be applied generally, yet a great part of the memoir is local.

The fecond effay, on the Comparison of Combustibles, is nearly of the fame kind; but it is the work of Mr. Lavoifier, and deferves attention. He examined the heat produced, by the time which a given quantity of any combuftible would fupport the ebullition of a given quantity of water, to which Fresh water was continually added, to fupply what was lost by evaporation; or, fecondly, by the quantity of the combustible employed. Each method produced the fame refults: foffil charcoal was the ftrongest, charred wood next in order, and then wood itself.

The ftate of every body, with respect to its principles, is attended with a change of its ftate of temperature and electri city. In feparating inflammable and nitrous air from metals, and fixed air from chalk, the remainder acquires a very fen

fible

fible negative electricity. Water in evaporation is almost always pofitive. This is the only memoir on the subject of electricity.

In lighting public theatres, Mr. Lavoifier recommends eliptical reverberators in the cieling, that no light may be loft, and the view of the ftage not impeded.

In Anatomy, the first memoir, by Mr. Vicq d'Azyr, contains a description of the brain, fpinal marrow, and origin of the nerves, in man. This will be a most important work: it is now only begun, and is illuftrated by plates; but it cannot be abridged. In the future Numbers, the brains of different animals will be defcribed. In Italy, confumptions are confidered as infectious, and no body, to whom this difeafe has proved fatal, is allowed to be diffected in the public fchools. Mr. Portal, with much reafon, opposes this opinion, and contends, that the complaint is rather hereditary than infectious. He makes a distinction between accidental and hereditary phthifis, which we believe to be juft: in the firft the bronchial glands are primarily affected, and the pulmonary ones in confequence: the hereditary phthifis probably first appears with an affection of the glands of the lungs. The fame author oppofes the ufual distinction of apoplexy into fanguine and ferous. He very properly urges phyficians to overlook it, and treat the patient according to the circumftances in which they find him.

On the Natural History of Animals, M. Daubenton describes the trachea arteria of birds. This memoir we have already noticed in our review of Mr. Latham's Synopfis. In the fwan the trachea paffes through the fternum; in cranes it rifes, and is turned back through this bone twice, fo that it has four curvatures. In the Paragua, an American bird, it paffes through the whole length of the fternum, and rifes to the top of it again, before it paffes into the lungs. In the ftone-bird, fo called from a hard excrefcence at the beginning of its beak (the cufhew bird of Edwards) the trachea rifes and finks twice on the outfide of the fame bone. This configuration is not to affift the voice, for herons and cranes are not remarkable in this refpect; it is not to facilitate their diving, for the ftonebird never dives. We must wait for the explanation, till we have received more obfervations on the fubject.

In the Botanical department, Meffrs. Fougeroux and Daubenton correct a common error, that fome very old timber work is formed of chefnut, which was on that account fuppofed to be formerly more common than at prefent, as well as larger. They fhow, that it is compofed of a peculiar fpecies of oak, very hard, durable, and uncommon, but of flow growth.

In Mineralogy, Mr. Gentil gives the obfervations fuggefted by long journeys and extenfive obfervations, on the formation of mountains. The principal novelty, in this memoir, is, that correfponding angles between two neighbouring mountains are never found, but where the valley feems to have been formed

by

by the course of a river. The inclination of the ftrata, he tells us, is fometimes fo regular, that it may be employed to measure the height of the mountain with tolerable exactness.

The next memoir contains the obfervations on mines of coal inflamed by accident, by the imprudence of the miners, or heat raised by fpontaneous fermentation. The author defcribes feveral of thefe, which burn as long as any fuel remains. When a brook has been conducted into the mine, to extinguish the fire, whofe heat is very fenfible on the furface, it occafions a little eruption, the nature of which we now very well understand, and fhall explain in another part of this article.

Some Mifcellaneous obfervations follow. The first is on calces of iron, found in the fchiftus that lies over coal. They refemble precipitations of that metal by acids, and one, produced by M. Sage, was like the precipitate obtained by the faccharine. The fecond relates to the means of making fœtid bitumens aromatic: afphaltum, expofed to a ftrong fun, in a clofe veffel (we fuppofe of glafs), refembles in its odour benzoin. In the laft volume, M. Fougeroux defcribed fulphur found in the rakings near the gate Saint Antoine: the ground was that on which a flaughter-house formerly stood. M. Morand found the fame in the ruins of a houfe fituated near an old fewer.

The aventurine, in M. Sage's opinion, is a kind of quartz. It is chiefly made up of fmall grains of this ftone, and to it owes its peculiar property, which is found too in fome fpecies of feld-fpath. M. Daubenton thinks that the ftone, formerly called aventurine, was rather of the latter fpecies.

The Chemical part of this volume is very interefting, and we have often had occafion to hint at it; we must therefore rest on it with unusual care. In the first article, • On Vegetable Analyfis,' count de Milli explains the method by which he intends to analyfe vegetable fubftances, and afterwards to extend it to the animal kingdom. There is a candour and generofity in his conduct in explaining the method, which fhews that he is more folicitous for the advantage of science than for the honour of discovery. He now only explains his apparatus, and may be followed by chemifts of different nations. We lately, in our review of Fourcroy's Lectures, mentioned how little we were really acquainted with animal fubftances; but we recom mended an attention to the fpontaneous changes, and an examination of the different parts, rather than to the more violent feparation by means of heat: we know that in this field a rich harvest of difcovery may be reaped. The count's plan is not, however, very different. He employs a lamp furnace, by which he gives the substance to be examined a conftant heat, from the temperature of the air to that of boiling water. The degree is known by the number of threads in the wick, which must be near, but not very exactly reach to the truth. In this apparatus the fubftances underwent the different fermentations;

a part

fible negative electricity. Water in evaporation is almost always pofitive. This is the only memoir on the subject of electricity.

In lighting public theatres, Mr. Lavoifier recommends eliptical reverberators in the cieling, that no light may be loft, and the view of the ftage not impeded.

In Anatomy, the first memoir, by Mr. Vicq d'Azyr, contains a defcription of the brain, fpinal marrow, and origin of the nerves, in man. This will be a most important work: it is now only begun, and is illuftrated by plates; but it cannot be abridged. In the future Numbers, the brains of different. animals will be defcribed. In Italy, confumptions are confidered as infectious, and no body, to whom this difeafe has proved fatal, is allowed to be diffected in the public schools. Mr. Portal, with much reafon, oppofes this opinion, and contends, that the complaint is rather hereditary than infectious. He makes a distinction between accidental and hereditary phthifis, which we believe to be juft: in the firft the bronchial glands are primarily affected, and the pulmonary ones in confequence: the hereditary phthifis probably first appears with an affection of the glands of the lungs. The fame author oppofes the ufual distinction of apoplexy into fanguine and ferous. He very properly urges phyficians to overlook it, and treat the patient according to the circumftances in which they find him.

On the Natural Hiftory of Animals, M. Daubenton defcribes the trachea arteria of birds. This memoir we have already noticed in our review of Mr. Latham's Synopfis. In the fwan the trachea paffes through the fternum; in cranes it rifes, and is turned back through this bone twice, fo that it has four curvatures. In the Paragua, an American bird, it paffes through the whole length of the sternum, and rifes to the top of it again, before it paffes into the lungs. In the stone-bird, fo called from a hard excrefcence at the beginning of its beak (the cufhew bird of Edwards) the trachea rifes and finks twice on the outfide of the fame bone. This configuration is not to affist the voice, for herons and cranes are not remarkable in this refpect; it is not to facilitate their diving, for the ftonebird never dives. We must wait for the explanation, till we have received more obfervations on the fubject.

In the Botanical department, Mefirs. Fougeroux and Daubenton correct a common error, that fome very old timber work is formed of chefnut, which was on that account fuppofed to be formerly more common than at prefent, as well as larger. They fhow, that it is compofed of a peculiar fpecies of oak, very hard, durable, and uncommon, but of flow growth.

In Mineralogy, Mr. Gentil gives the obfervations fuggefted by long journeys and extenfive obfervations, on the formation of mountains. The principal novelty, in this memoir, is, that correfponding angles between two neighbouring mountains are never found, but where the valley feems to have been formed

by