the heavens; so that they cannot bear any confiderable diminution of their light, by a contrast with a more luminous object, without becoming invifible. If then the sphere of illumination of our new planet be limited to 18 or 20', we may fully account for the loss of the fatellites when they come within its reach; for they have very little light to lofe, and lose it pretty suddenly.

'This contraft, therefore, between the condition of the Georgian fatellites and those of the brighter planets, feems to be fufficient to account for the phænomenon of their becoming invifible.

We may avail ourselves of the obfervations that relate to the distances at which the fatellites vanifh, to determine their relative brightness. The 2d fatellite appears generally brighter than the ift; but, as the former is usually loft farther from the planet than the latter, we may admit the 1ft fatellite to be rather brighter than the 2d. This feems to be confirmed by the observation of March 9, 1791; where the 2d appeared to be smaller than the ift, though the latter was only 25" from the planet, while the other was 30",8.

The first of the new fatellites will hardly ever be seen otherwife than about its greatest elongations, but cannot be much inferior in brightness to the other two; and, if any more interior fatellites fhould exift, we shall probably not obtain a fight of them; for the fame reafon that the inhabitants of the Georgian planet perhaps never can discover the existence of our earth, Venus, and Mercury.

The 2d new or intermediate fatellite is confiderably smaller than the 1ft and 2d old fatellites. The two exterior, or 5th and 6th fatellites, are the smallest of all, and must chiefly be looked for in their greatest elongations.' P. 77.

This explanation we find fcarcely adapted to the relative brightness of the first and fecond of the fatellites; and it is not applicable to fixed ftars, which probably thine with their own light, and therefore could not be obfcured by the faint reflected light of the planet.

IV. An Inquiry concerning the Source of the Heat which is excited by Friction. By Benjamin Count of Rumford, F. R. S. M. R. I. A.'

In the experiments of count Rumford, the heat produced by friction was obferved in boring cannon at Munich. The author's object is to fhow, that, as fo much heat is produced without any evident fource, heat mare probably confifts in motion than in the feparation of an igneous fluid, which, in modern chemistry, is called caloric. After the operation had continued 30', the mercury rofe to 130°; and it cooled only to 1100, when forty-one minutes had elapfed from the conclufion of the experiment. The heat excited in the whole mafs

would have melted fix pounds of ice, or have brought near five pounds of ice-cold water to the ftate of boiling; for the body of heated metal weighed 113 pounds. The heat was not produced from the iron; for the metallic chips had their сараcity for heat unchanged. It could not be from the air; for, in varying the experiment by an exclufion of the external air from the cavity in which the borer acted, the heat was the fame; in boring under water, it was ftill the fame; and, by a continuance of the action, the water was made to boil. Two wine gallons and a quarter (more than eighteen pounds of water) boiled in two hours and a half. All the heat excited would have brought more than twenty-fix pounds of ice-cold water to a boiling heat. Nine wax candles of threefourths of an inch in diameter, would not, in the most favourable circumftances, have excited fo much heat in the fame time.

From whence came the heat which was continually given off in this manner, in the foregoing experiments? Was it furnished by the small particles of metal, detached from the larger folid maffes, on their being rubbed together? This, as we have already seen, could not poffibly have been the cafe.

Was it furnished by the air? This could not have been the cafe; for, in three of the experiments, the machinery being kept immerfed in water, the accefs of the air of the atmosphere was completely prevented..

Was it furnished by the water which furrounded the machinery? That this could not have been the cafe is evident; firft, becaufe this water was continually receiving heat from the machinery, and could not, at the fame time, be giving to, and receiving heat from, the fame body; and fecondly, because there was no chemi'cal decompofition of any part of this water. Had any fuch decompofition taken place, (which indeed could not reasonably have been expected,) one of its component elaftic fluids (moft probably inflammable air) muft, at the fame time, have been fet at liberty, and, in `making its efcape into the atmosphere, would have been detected; but, though I frequently examined the water, to fee if any air bubbles rofe up through it, and had even made preparations for catching them, in order to examine them, if any should appear, I could perceive none; nor was there any fign of decompofition of any kind whatever, or other chemical procefs, going on in the water.

Is it poffible that the heat could have been supplied by means of the iron bar to the end of which the blunt fteel borer was fixed? or by the small neck of gun-metal by which the hollow cylin der was united to the cannon? Thefe fuppofitions appear more improbable even than either of those before mentioned; for heat was continually going off, or out of the machinery, by both thefe paff ages, during the whole time the experiment lafted,

And, in reasoning on this fubject, we must not forget to confider that most remarkable circumftance, that the fource of the heat generated by friction, in these experiments, appeared evidently to be inexhauftible.

It is hardly neceffary to add, that any thing which any infulated body, or fyftem of bodies, can continue to furnish without limitation, cannot poffibly be a material substance: and it appears to me to be extremely difficult, if not quite impoffible, to form any diftinct idea of any thing, capable of being excited, and communicated, in the manner the heat was excited and communicated in these experiments, except it be motion.' P. 98.

We beg leave to enter our caveat against this conclufion. One fact cannot militate against a feries of observations, which confirm the existence of an igneous fluid; and various fources of the heat, which count Rumford has not noticed, may yet be traced. The chips, indeed, had not loft the capacity of heat which they poffeffed before the operation; but much of the metal must have been broken into duft, or into very minute parts; and it was not the whole, but a portion only, that was examined. Other fources of heat, viz. compreffion and condenfation, have not been confidered. The force with which the borer acts is immenfe; and its whole power is exerted in compreffing the parts which it enters and cuts out. As Mr. Pictet's experiments feem to prove that two hard incompreffible bodies in friction do not excite heat, we fhould rather look for the fource of the heat (in the present experiments) in the caloric of the metal than in the motion.

V. Obfervations on the Foramina Thebefii of the Heart.

By Mr. John Abernethy, F. R. S. Communicated by Everard Home, Efq. F. R. S.'

Anatomists well know that the coronary veffels of the heart feem occafionally to terminate in its cavity, or at least that their fubftance is fo tender, as often to allow their being ruptured. On the former fuppofition, the terminations have been called, from their original obferver, Foramina Thebefii. They are principally obferved on the right fide; and, as, from the peculiar termination of the coronary vein on that fide, the veffel is fometimes fubjected to the danger of obftruction from too great diftenfion of the right auricle and ventricle, Mr. Abernethy feems to confider these foramina as a wife provifion of nature, to prevent ftagnation in the nutrient vefels of the organ. The diftention must particularly take place in an obftruction of the circulation through the lungs.

6

Having been attentive to fome very bad cafes of pulmonary confumption, from a defire to witnefs the effects of breathing medicated air in that complaint, I was led to a more particular examination of the heart of thofe patients who died. In these cafes, I

found, that by throwing common coarte waxen injection into the arteries and veins of the heart, it readily flowed into the cavities of that organ; and that the left ventricle was injected in the first place, and most completely. When the ventricle was opened, and the effufed injection removed, the foramina thebefii appeared both numerous and large, and diftended with the different coloured wax which had been impelled into the coronary arteries and veins. Upon eight comparative trials, made by injecting the veffels of hearts taken from fubjects whose lungs were either much. diseased, or in a perfectly found ftate, I found, that in the former, common injection readily flowed, in the manner which I have defcribed, into all the cavities of the heart, but principally into the left ventricle; whilst, in many of the latter, I could not impel the least quantity of fuch coarfe injection into that cavity.' P. 104.

As our author's arguments lead rather to an explanation of the neceffity that the veffels fhould open into the cavities of the heart on the right fide, we do not perceive the reason which, in difeafed lungs, fhould make them particularly large on the left. It may be admitted that, on that fide alfo, there is a neceffity for the fame contrivance, when the circulation is greatly accelerated; but this affords no peculiar reafon for their enlargement there in pulmonic cafes, where, though the pulfe is quick, it is alfo fmall. We allow, that they fhould rather open, in a natural ftaté, into the right cavities, as the blood requires, after circulation, to be again expofed to air in the pulmonary veffels; but this would render it more neceffary, that, in pulmonic difeafes, the foramina on the right fide should be enlarged. On the whole, the apertures are more probably excretory veffels enlarged from difeafe, than openings for the relief of diftended veffels; fince we find, in other mufcular organs, no great neceffity for obviating the effects of occafional obftruction, and no part of the ftructure of a coronary veffel is fo delicate and minute, as to lead us to think that its functions, at least its uninterrupted functions, are of great importance in the fyftem.

In difeafes of the lungs, Mr. Abernethy has found the foramen ovale frequently open. This he properly explains from a deficiency of blood in the left auricle, and a redundancy in the right. As the foramen is originally clofed by membranes overlapping each other, this unequal diftenfion may again form an aperture. This accounts alfo for the blue colour fometimes obfervable in the complexions of hectic perfons; for, if all the blood paffes through the lungs, whatever may be the pain and oppreffion to the patient, the whole muft receive its portion of oxygen.

VI. An Analysis of the earthy Subftance from New South Wales, called Sydneia or Terrà Auftralis. By Charles Hatchett, Efq. F. R.Ś.' · ···

- The earthy fubftance from New South-Wales seems to be certainly the Growan clay, that is, decompofed granite, without any admixture of a new earth. Mr. Klaproth had formed that opinion in confequence of his experiments; but fome chemists of credit fufpected that Mr. Wedgwood and Mr. Klaproth had tried different kinds of earth. The subject is now fully cleared. Mr. Hatchett undoubtedly tried the true earth from New Holland, and even a portion of that, from which the fpecimen examined by Mr. Wedgwood was taken.

• VII. Abstract of a Register of the Barometer, Thermometer, and Rain, at Lyndon, in Rutland, for the Year 1796. By Thomas Barker, Efq. Communicated by Mr. Timothy Lane, F. R. S.'

The barometer was highest in October, viz. at 30.07, and lowest in May, 28.33; the mean height was 29.2. The range of the thermometer, abroad, was from 80 to 14. The mean heat of April, as ufual, was about 51°; the quantity of rain, 22.082. In the journal of the fociety for 1797, the mean height of the barometer was 29.92; the mean height of Six's thermometer, 49.4; of the common thermometer about 50; of the hygrometer 79.2; the quantity of rain was 22.697. The mean heat of April was 47.8. This is much below the ftandard of the mean heat of the whole year, with which in general the mean heat of April, according to the ob fervation of Mr. Kirwan, nearly coincides.

• VIII. An Account of fome Endeavours to afcertain a Standard of Weight and Meafure. By Sir George Shuckburgh Evelyn, Bart. F. R. S. and A. S.'

This excellent paper being incapable of fatisfactory abridgment, we fhall merely notice the author's object, and the refults. To avoid all the difficulties which arife from determining the centre of motion and ofcillation in pendulums, our author propofed to make the ftandard meafure the difference of vibrations of a pendulum, compared with the difference of length; or thence to determine its abfolute length; and to afcertain the weight of a certain bulk of diftilled water, in a given state of the atmosphere. The various delicate machinery for this purpofe, fir G. S. Evelyn defcribes at length."

6

• In conclufion,' (he fays) it appears that the difference of the length of two pendulums, fuch as Mr. Whitehurft ufed, vibrating 42 and 84 times in a minute of mean time, in the lati tude of London, at 113 feet above the level of the fea, in the temperature of 60°, and the barometer at 30 inches, is 59,89358 inches of the parliamentary ftandard; from whence all the meafures of fuperficies and capacity are deducible.

That, agreeably to the fame fcale of inches, a cubic inch of pure distilled water, when the barometer is 29,74 inches, and ther