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the heavens; so that they cannot bear any considerable diminution of their light, by a contrast with a more luminous objekt, without becoming invisible. 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 satellites when they come within its reach; for they have very little light to lose, and lose it pretty suddenly.
• This contrast, therefore, between the condition of the Georgian satellites and those of the brighter planets, seems to be sufficient to account for the phænomenon of their becoming invifible.
• We may avail ourselves of the observations that relate to the distances at which the fatellites vanish, to determine their relative brightness. The 2d satellite appears generally brighter than the ift; but, as the former is usually fost farther from the planet than the latter, we may admit the ist fatellite to be rather brighter than the 2d. This seems to be confirmed by the observation of March 9, 1791; where the ad 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 satellites will hardly ever be seen otherwise than about its greatest elongations, bụt cannot be much inferior in brightness to the other two; and, if any more interior fatellites thould exist, we Ihall probably not obtain a light of them; for the same reason that the inhabitants of the Georgian planet perhaps never can discover the existence of our earth, Venus, and Mercury.
• The 2d new or intermediate satellite is considerably smaller than the 1st and 2d old satellites. The two exterior, or 5th and 6th satellites, are the smallest of all, and must chiefly be looked for in their greatest elongations.' P. 77.
This explanation we find scarcely adapted to the relative brightness of the first and second of the fatellites; and it is not applicable to fixed stars, which probably thine with their own light, and therefore could not be obscured 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.J. A.'
In the experiments of count Rumford, the heat produced by friction was observed in boring cannon at Munich. The author's object is to show, that, as so much heat is produced without any evident fource, heat more 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 rose to 130° ; and it cooled only to 110°, when forty-one' ininutes had elapsed from the conclufion of the experiment. The heat excited in the whole mass
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 capacity for heat unchanged. It could not be from the air ; for, in varying the experiment by an exclusion of the external air from the cavity in which the borer acted, the heat was the same; in boring under water, it was still the same; 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 excitèd 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 circunstances, have excited so 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 solid masses, on their being rubbed together? This, as we have already seen, could not possibly have been the case.
"Was it furnithed by the air ? This could not have been the case ; for, in three of the experiments, the machinery being kept immersed in water, the access of the air of the atmosphere was completely prevented..
• Was it furnished by the water which surrounded the machinery? That this could not have been the case is evident; first, because this water was continually receiving heat from the machinery, and could not, at the same time, be giving to, and receiving heat from, the fame body; and secondly, because there was no chemi'cal decomposition of any part of this water.
fuch decomposition taken place, (which indeed could not reasonably have been expected,) one of its component elastic fluids (inost probably inflammable air) must, at the same time, have been set at liberty, and, in making its' escape into the atmosphere, would have been detected ; but, though I frequently examined the water, to see if any air bubbles rose 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 process, going on
in the water.
• Is it possible that the heat could have been supplied by means of the iron bar to the end of which the blunt steel borer was fixed? or by the small neck of gun-metal by which the hollow cylin, der was united to the cannon? These suppositions appear more improbable even than either of those before mentioned ; for heat was continually going off, or out of the machinery, by both thefe parlages, during the whole time the experiment lasted,
• And, in reasoning on this subject, we must not forget to con lider that most remarkable circumstance, that the source of the heat generated by friction, in these experiments, appeared evidently to be inexhaustible.
It is hardly necessary to add, that any thing which any insulated body, or system of bodies, can continue to furnish without limitation, cannot possibly be a material substance : and it appears to me to be extremely difficult, if not quite impossible, to form any distinct 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 conclusion. One fact cannot militate against a series of observations, which confirm the existence of an igneous fluid; and various sources of the heat, which count Rumford has not noticed, may yet be traced. The chips, indeed, had not lost the capacity of heat which they possessed before the operation ; but much of the metal must have been broken into dust, or into very minute parts ; and it was not the whole, but a portion only, that was examined. Other sources of heat, viz. compression and condensation, have not been considered. The force with which the borer acts is immense; and its whole power is exerted in compressing the parts which it enters and cuts out. As Mr. Pictet's experiments seem to prove that two hard incompressible bodies in friction do not excite heat, we should rather look for the source of the heat (in the present experiments) in the caloric of the metal than in the motion.
• V. Observations on the Foramina Thebesii of the Heart. By Mr. John Abernethy, F.R.S. Communicated by Everard Home, Esq. F. R. S.'
Anatomists well know that the coronary vessels of the heart seem occafionally to terminate in its cavity, or at least that their substance is so tender, as often to allow their being rupcured. On the former supposition, the terminations have been called, from their original observer, Foramina Thebefii. They are principally observed on the right side; and, as, from the peculiar termination of the coronary vein on that side, the vessel is sometimes subjected to the danger of obstruction from too great distension of the right auricle and ventricle, Mr, Abernethy seems to consider these foramina as a wile provifon of nature, to prevent stagnation in the nutrient veliels of the organ. The distension must particularly take place in an obstruction of the circulation through the lungs.
• Having been attentive to some very bad cases of pulmonary consumption, from a desire to witness the effects of breathing medicated air in that complaint, I was led to a more particular examination of the heart of those patients who died. In these cases, 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 effused injection removed, the foramina thebefii appeared both numerous and large, and distended with the different coloured wax which had been impelled into the coronary arteries and eins. Upon eight comparative trials, made by injecting the vessels of hearts taken from subjects whose lungs were either muci, diseased, or in a perfectly found state, I found, that in the former, common inje&tion readily fowed, in the manner which I have described, into all the cavities of the heart, but principaliy into the left ventricle ; whilst, in many of the latter, I could not impel the least quantity of such coarse injection into that cavity.' P. 104.
As our author's arguments lead rather to an explanation of the necessity that the vessels fhould open into the cavities of the heart on the right side, we do not perceive the reason which, in diseased lung's, should make them particularly large on the left. It may be admitted that, on that fide also, there is a necessity for the same contrivance, when the circulation is greatly accelerated; but this affords no peculiar reason for their en' largement there in pulmonic cases, where, though the pulse is quick, it is also small. We allow, that they should rather open, in a natural state, into the right cavities, as the blood requires, after circulation, to be again exposed to air in the pulmonary vessels; but this would render it more necessary, that, in pulmonic diseases, the foramina on the right side should be en, larged. On the whole, the apertures are more probably excretory vessels enlarged from disease, than openings for the relief of diftended vessels ; lince we find, in other inuscular organs, no great neceffity for obviating the effects of occasional obstruction, and no part of the structure of a coronary vessel is so delicate and minute, as to lead us to think that its functions, at least its uninterrupted functions, are of great importance in the system. * In diseases 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 closed by membranes overlapping each other, this unequal distension may again form an aperture. This accounts' also for the blue colour fometimes observable in the complexions of hectic persons ; for, if all the blood passes through the lungs, whatever may be the pain and oppreffion to the patient, the whole must receive its por
tion of oxygen.
• VI. An Analysis of the earthy Substance from New South Wales, called Sydneia or Teria Australis. By Charles Hatchett, Esq. F.R.S.'
The earthy substance from New South Wales seems to be certainly the Growan clay, that is, decomposed granite, withqut any admixture of a new earth. Mr. Klaproth had formed that opinion in consequence of his experiments; but fone chemists of credit suspected that Mr. Wedgwood and Mr. Klaproth had tried different kinds of earth. The subject is pow fully cleared. Mr. Hatehert undoubtedly tried the true earth from New Holland, and even a portion of that, from which the specimen examined by Mr. Wedgwood was taken.
• VII. Abstract of a Register of the Barometer, Thermo meter, and Rain, at Lyndon, in Rutland, for the Year 1796. By Thomas Barker, Esq. 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 141. The mean heat of April, as usual, 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 standard 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 some Endeavours to ascertain a Standard of Weight and Measure. By Sir George Shuckburgh Evelyn, Bart. F.R.S. and A.S.
This excellent paper being incapable of satisfactory abridge ment, we shall inerely notice the author's object, and the refults. To avoid all the difficulties which arise from determin, ing the centre of motion and ofcillation in pendulums, our author proposed to make the standard measure the difference of vibrations of a pendulum, compared with the difference of length ; or thence to determine its absolute length ; and to ascertain the weight of a certain bulk of distilled water, in a given state of the atmosphere. The various delicate machinery for this purpose, fir G. S. Evelyn describes at length.
• In conclusion,' (he says) • it appears that the difference of the length of two pendulums, such as Mr. Whitehurit used, 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 sea, in the temperature of 60°, and the barometer at 30 inches, is = 59,89358 inches of the parliamentary standard; from whence all the measures of superficies and capacity are deducible.
· That, agreeably to the farne scale of inches, a cubic inch of pure distilled water, when the barometer is 29,74 inches, and ther