46a PHILOSOPHICAL TRANSACTIONS. [aNNO 1740. 



1. A single spring, fixed to a moveable horizontal table, is made to commu- 

 nicate to the same body, degrees of force unquestionably equal, while the de- 

 grees o£ velocity communicated at the same time are also undoubtedly equal; 

 therefore the forces are proportional to the velocities. 



, 2. In Mr. Mariotte's experiments, the impressions made upon equal surfaces 

 in the same point of time, are found to be in the duplicate ratio of the velo- 

 cities; but the masses or numbers of impinging particles are in the simple ratio 

 of the velocities; consequently, the masses and velocities conjunctly being in 

 the duplicate ratio, i. e. as the impressions, must also be as the forces which 

 made them; which is the old opinion. 



3. A complicated or bent spring interposed between two unequal bodies, 

 acting on each with an equal pressure, and during an equal time, must commu- 

 nicate equal moving forces to each; but their velocities are by experiment reci- 

 procally proportional to their masses: therefore their masses, drawn into their 

 respective velocities, are also equal, as were their moving forces; and by con- 

 sequence their moving forces are as the masses and velocities conjunctly; which 

 is the generally received opinion. 



In the appendix, the author answers some of the principal arguments brought 

 in favour of the contrary side. 



The last of these arguments is founded on Poleni's experiments, in which 

 equal cavities are formed in soft substances, by equal bodies falling from heights 

 reciprocally proportional to their masses. This the author sets aside, as insuffi- 

 cient, since the times of forming these equal cavities are unequal, and unequal 

 causes may produce equal effects in unequal times. Poleni does indeed reply, 

 and say, that the formation of these cavities seems to be instantaneous; but 

 the ingenious author shows the contrary, and that from a position allowed of 

 by Poleni himself, in his reply. 



Of some remarkable Stones, taken out of the Kidneys of Mrs. Felles, on opening 

 her Body after her Decease. By Noah Sherwood, Surgeon. N" 45Q, p. 6 10. 



Mr. S. found nothing amiss in any of the viscera, till he came to the kid- 

 neys, both of which were considerably enlarged, and of an oblong figure, and 

 had several protuberances bunching out, which made the surface appear almost 

 like a beeve's kidney. On feeling them externally, he could plainly perceive 

 they were caused by stones; he took them out of the body, and laid them open 

 longitudinally, and found in the right kidney several stones o( an irregular 

 figure, branched like coral : they had extended themselves beyond the capacity 

 of the pelvis on every side, though that was greatly enlarged, so as each of 

 them to contain half a pint of pus, or inore, forming for themselves cells in 



