566 PHILOSOPHICAL TRANSACTIONS. [aNNO 1748. 



by the same means to prove what might be granted, making some allowance for 

 impropriety of expression, but can never be proved. 



If some mathematician should take it in his head to affinn, that the velocity 

 of a body is not as the space it passes over in a given time, but as the square of 

 that space ; you might bring mathematical arguments and experiments to con- 

 fute him ; but you would never by these force him to yield, if he was ingenuous 

 in his way ; because you have no common principles left you to argue from, and 

 you differ from each other, not in a mathematical proposition, but in a mathe- 

 matical definition. 



Suppose a philosopher has considered only that measure of centripetal force 

 which is proportional to the velocity generated by it in a given time, and from 

 this measure deduces several propositions. Another philosopher in a distant 

 country, who has the same general notion of centripetal force, takes the velocity 

 generated by it, and the quantity of matter together, as the measure of it. 

 From this he deduces several conclusions, that seem directly contrary to those 

 of the other. Thereupon a serious controversy is begun, whether centripetal 

 force be as the velocity, or as the velocity and quantity of matter taken together. 

 Much mathematical and experimental dust is raised , and yet neither pai-ty can 

 ever be brought to yield ; for they are both in the right, only they have been 

 unlucky in giving the same name to different mathematical conceptions. Had 

 they distinguished these measures of centripetal force as Newton has done, calling 

 the one vis centripetae quantitatis acceleratrix, the other quantitatis motrix ; all 

 appearance of contradiction had ceased, and their propositions, which seem so 

 contrary, had exactly tallied. 



Concerning a large Piece of a Lath being thrust into a Man's Eye, who Reco- 

 vered of it. By Rich. Hassel, Esq., F.R.S. N° 480, p. 520. 

 Henry Halsey, of South Mims, labourer, thrust a long lath with great vio- 

 lence into the great can thus of the left eye of Edward Roberts of the same place, 

 labourer, which broke off quite short ; so that a piece near 2^ inches long, half 

 an inch wide, and above a quarter of an inch thick, remained in his head, and 

 was so deeply buried there, that it could scarcely be seen, or laid hold of. He 

 rode thus with the piece of lath in his eye from Kick's end, where the thing was 

 done, to Barnet, which is above a mile, to the house of Mr. Morse, a surgeon 

 there, who extracted it with difficulty ; it sticking so hard, that others had been 

 baffled in attempting to extract it. Roberts c^ontinued dangerously ill a long 

 time ; but at last recovered entirely, and has the sight of the eye, and the use 

 of the muscles. But some time after he seemed well, he told Mr. H. that, on 

 leaning down forward, he felt great pain in his head. The piece is supposed to 

 have passed behind the right eye. 



