VOL. LII.J PHILOSOPHICAL TRANSACTIONS. 57p 



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 ex- 

 traordinary 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. 



■J. 'In confirmation of this power here attributed to the pericardium, of strength- 

 ening 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 situ- 

 ation of the right auricle and the pulmonary artery. 



LII. Of the Irregularities i7i the Plarietary Motions, caused by the Mutual At- 

 traction 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 

 t 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 ascer- 

 tained, 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 mu- 

 tual 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 them- 

 selves with solely considering those inequalities of the planetary motions, that 

 arise from th^ 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. en- 

 deavours 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 SLteh 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- 



4 K 2 



