usually accompanies the separation of the soul and body, as was possible, under any circumstances whatever.

The above-mentioned appearances (as they showed the immediate cause of his Majesty's death) were thought sufficient to form the report to his present Majesty, and his Council. But as the very eininent and amiable character of his late Majesty must make the nature of his death the object of every one's attention and inquiry and as the case was exceedingly singular and extraordinary in itself; and as the heart must have been merely passive, and consequently there must have been some other concurrent circumstances necessary to produce such an effect; I judged, at the time when the report was drawn, that a more minute and exact detail would not only be expected by the world, but would be highly proper, as our inquiry furnished sufficient matter.

Two questions naturally arise on the face of our report; viz. by what means the right side of the heart became so charged with blood, as to be under a necessity of bursting? and how it could happen, that, as the ventricle (when under great distentions) generally makes one continued cavity with the auricle, and is much thicker and stronger than the auricle, the blood should nevertheless force its way, by bursting the ventricle, rather than the auricle, seemingly in contradiction to the known property of fluids, to force their way where the resistance is least.

On examining the parts, we found the two great arteries, (the aorta and pulmonary artery, as far as they are contained within the pericardium) and the right ventricle of the heart, stretched beyond their natural state; and, in the trunk of the aorta, we found a transverse fissure on its inner side, 14inch long, through which some blood had recently passed, under its external coat, and formed an elevated ecchymosis. This appearance showed the true state of an incipient aneurism of the aorta; and confirmed the doctrine, which I had the honour to illustrate, by an experiment, to the satisfaction of the R. s., in the year 1728; (See Phil. Trans. N° 402) viz. that the external coat of the artery may (and does) often controul an impetus of the blood, capable of bursting the internal or ligamentous coat; although this last is by much the thickest, and seemingly the strongest. In regard to this distention of the aorta; as his Majesty had, for some years, complained of frequent distresses and sinkings about the region of the heart; and as his pulse was of late years observed to fall very much on bleeding; it is not doubted, but that this distention of the aorta had been of long standing, at least to some degree; and as the pulmonary artery was thereby necessarily compressed, and a resistance, greater than natural, thereby opposed to the blood's discharge out of the right ventricle, it is reasonable to conclude, that a distention and consequent weakness of the pulmonary artery and right ventricle, to some degree, were nearly coeval with that of the aorta. But that the aorta had suffered a more

extraordinary and violent distention, immediately antecedent to the bursting of the ventricle, is evident, from the recent fissure of the aorta, and the consequent extravasation of blood between its coats. Now as this increased and violent distention of the aorta must have been attended with a proportionate pressure on the pulmonary artery, and consequently an increased opposition to the passage of the blood out of the right ventricle; so that distention of the aorta must be considered as the immediate cause of the right ventricle's being surcharged with blood, and consequently of its bursting.

The immediate cause of this distention of the aorta, as also of its being determined to that particular time, are naturally explicable, from his Majesty's having been at the necessary-stool; as the office then required cannot be executed but by such a pressure on all the contents of the lower belly, and consequently on the great descending artery, as must of necessity subject the trunk of the aorta, and all its upper branches, to a surcharge with blood continually increasing, in proportion as the pressure may happen to be continued longer, or exerted with greater violence, in consequence of a costive habit, or any other resistance.

its

As to the ad question; viz. how it could happen that the blood should force way rather through the side of the ventricle than of the auricle? since it is well known that when the ventricle is fully distended with fluids, they will easily pass back into the auricle; so that under such a distention as the ventricle must have suffered before it burst, it should seem to have made one continued cavity with the auricle; of which cavity, the auricle being by much the weakest part, must have been the most liable to a rupture. This certainly is the circumstance in which the very great singularity of the case before us consists; and many difficulties offer against any obvious explanation.

Two circumstances however seem to throw some light on this obscure and difficult question. The first consists in the texture, connexions, and capacity of the pericardium; the 2d in the order in which the several surcharges must have arisen.

The pericardium is a strong tendinous membrane, inelastic in every direction, containing the 2 auricles, the 2 ventricles, and the 2 great arteries, as in a purse; it is fixed to its contents at the back of the 2 auricles, where, by its connexion, it surrounds the 2 vena cava : hence, passing along the arch formed by the aorta, it descends to the pulmonary artery, and continues round the orifices of the pulmonary veins, firmly attached to these several parts in its passage. By these connexions, these parts are all fixed in their several stations, incapable of separating from each other, or shifting their situations, however they may happen to be compressed. The pericardium is generally said to serve as a defence to the heart; but that defence seems to consist chiefly, in preventing the right auricle from being stretched by the depressions (or complanations) of the diaphragm in

hunger and inspiration, and, by its bearing firmly against the sides of the auricles, to support and strengthen them against too great distentions: for the cavity of the pericardium seems to be but little more than commensurate to the bulk of its contents, when one half of them are filled and the other half empty. This will appear on endeavouring to fill the heart, with its auricles, and its 2 great arteries, with wax, at the same time while it is inclosed in the pericardium; in which experiment, one or other of these cavities will be found to have been so compressed by the pericardium, as to have refused a free admittance to the wax, and will therefore be found proportionably empty.

The elastic texture, connexions, and capacity of the pericardium, being thus stated, let us now consider the order in which the several distentions must have arisen in the two great arteries and cavities of the heart, with the necessary effects of those distentions on the pericardium and the parts which it contains.

The first distention (and this a great and violent one) must have arisen in the aorta; and the consequent pressure on the pulmonary artery, by the aorta so distended, must have been sufficient (either by degrees or at once) to stop the blood's discharge out of the right ventricle and pulmonary artery, and to distend both those cavities beyond their natural state of repletion. So that under these circumstances the 2 great arteries and the right ventricle, must have been under an extraordinary and continual distention, and consequently an increase of bulk at the same time; whereas, in the natural state of the body, these 3 cavities are alternately dilated and contracted, and the right ventricle is always proportionally diminished in bulk, as the pulmonary artery is increased, and vice versa. So that with respect to these three great cavities, (supposing that their several distentions had been no greater than natural) the pericardium must have been obliged to contain one third more in proportion than its capacity was formed to receive. During this time, the blood being stopped in its passage through the lungs, and its afflux to the left auricle and ventricle being thereby suspended, the left auricle and ventricle must have remained in a contracted state; in consequence of which the right ventricle had ample space in the pericardium, to admit that degree of distention, which was previously requisite for its bursting. But the right auricle (being fixed to its station by its connections with the left auricle and the pericardium, and being firmly compressed against the pericardium, by the aorta, the pulmonary artery, and the right ventricle, all which appear to have been, at this time, greatly distended beyond their natural bulk) must have been thereby deprived of the space in the pericardium necessary to admit of its being distended; and the whole surcharge and distention must, by the pressure of the pericardium on the auricle, necessarily have been confined to the right ventricle till it burst.

Had these surcharges arisen in any other order, their effects must have been

greatly different: as for instance, if the surcharge in the right ventricle had arisen from any other pressure than from such a distention of the aorta, the extraordinary bulk of the aorta, and its pressure against the pulmonary artery, would not have existed, and the right auricle, not being then compressed against the pericardium, would have been at liberty to distend, till the blood had made its way through its sides.

In confirmation of this power here attributed to the pericardium, of strengthening and supporting its contained parts, let it be observed that, in the case under consideration, the place of the fissure in the aorta is precisely where the pressure of the pericardium is kept off from the aorta, to a considerable degree, by the situation of the right auricle and the pulmonary artery.

LII. Of the Irregularities in the Planetary Motions, caused by the Mutual Attraction of the Planets. By Charles Walmesley, F.R.S., and Member of the Royal Academy of Sciences at Berlin, and of the Institute, at Bologna. p. 275.

Finding that the influence which the primary planets have on one another, to disturb mutually their motions, had been but little considered, Mr. W. thought it a subject worthy of examination. The force of the sun to disturb the moon's motion, flows from the general principle of gravitation, and has been fully ascertained, both by theory and observation; and it follows, from the same principle, that all the planets must act on one another, proportionally to the quantities of matter contained in their bulk, and the inverse ratio of the squares of their mutual distances; but as the quantity of matter contained in each of them, is but small when compared to that of the sun, so their action on one another is not so sensible as that of the sun on the moon. Astronomers generally contented themselves with solely considering those inequalities of the planetary motions, that arise from the eliptical figure of their orbits; but as they have been enabled of late years, by the perfection of their instruments, to make observations with much more accuracy than before, they have discovered other variations, which they have not indeed been able yet to settle, but which seem to be owing to no other cause but the mutual attraction of those bodies. In order therefore to assist the astronomers in distinguishing and fixing these variations, Mr. W. endeavours to calculate their quantity, from the general law of gravitation, and reduce the result into tables, that may be consulted whenever observations are made.

He offers at present the first part of such a theory, in which he has chiefly considered the effects produced by the actions of the earth' and Venus on each other. But the same propositions will likewise give, by proper substitutes, the effects of the other planets on these two, or of these two on the others. To ob

viate in part, the difficulty of such intricate calculations, he has supposed the orbits of the earth and Venus to be originally circular, and to suffer no other alteration but what is occasioned by their mutual attraction, and the attraction of the other plancts. Where the forces of two planets are considerable with respect to each other, as in the case of Jupiter and Saturn, it may be necessary in such computations to have regard to the excentricity of their orbits; and this may bé reserved for a subject of future scrutiny. But the supposing the orbits of the earth and Venus to be circular, may, in the present case be admitted without difficulty, as the forces of these two planets are so small, and the excentricity of their orbits not considerable. On these grounds therefore he has computed the variations which are the effects of the earth's action: 1st, the variation of Venus's distance from the sun; 2dly, that of its place in the ecliptic; 3dly, the retrograde motion of Venus's nodes; and 4thly, the variation of inclination of its orbit to the plane of the ecliptic.

The similar irregularities in the motion of the earth, occasioned by its gravitation to Venus, are here likewise computed : but it is to be observed, that the absolute quantity of these irregularities is not here given, it being impossible, at present, to do it; because the absolute force of Venus is not known to us. He has therefore stated that planet's force by supposition, and has accordingly computed the effects it must produce: with the view that the astronomers may compare their observations with the motions so calculated, and from thence discover how much the real force differs from that which has been supposed. But the exact determination of the force of Venus must be obtained by observations made on the sun's place, at such times when the effect of the other planets is either null or known.

The influence of Venus on the earth being thus computed, that of the other planets on the same may likewise hereafter be considered: by which means, the different equations, that are to enter into the settling of the sun's apparent place, will be determined; the change of the position of the plane of the earth's orbit will also be known; and consequently the alteration that thence arises in the obliquity of the ecliptic, and in the longitude and latitude of the fixed stars. These matters of speculation are reserved for another occasion, in case what is here offered should deserve approbation. But the later more accurate calculations and astronomical observations have rendered a further account of this elaborate paper unnecessary.

LIII. An Account of a Treatise in French, presented to the Royal Society, intitled, Lettres sur l'Electricité, by the Abbè Nollet, Member of the Royal Academy of Sciences, &c. &c. By William Watson, M.D., F.R.S. p. 336. About 8 years since, the learned and ingenious author of the work before us