VOL. XLI.] PHILOSOPHICAL TRANSACTIONS. 46I 



6. ^t Rosehi/l, Smsex. By John Fuller, Esq. jun. F. R. S. p. 6o6. — It was 

 a strong and very steady light, nearly of the colour of red ochre. It did not 

 seem to dart or flash at all, but continued going on in a steady course against 

 the wind, which blew fresh from the south-west. It began about north north- 

 west, in form of a pillar of light, at about 6^ 15"" in the evening; in about 10 

 minutes, a 4th part of it divided from the rest, and never joined again; in 10 

 minutes more it described an arch, but did not join at top; exactly at 7, it 

 formed a bow, and soon after quite disappeared. It was all the while lightest 

 and reddest at the horizon. It gave as much light as a full moon. 



At 8'' it began again exactly north ; it was very light then, but not near so 

 light as before: in half an hour it made an arch from east to west, and went 

 quite away to the south, when it ended much with the same appearance as it 

 began in the north, but not quite so red. 



Jl short Account of Dr. Jurins ninth and last Dissertation, De Fi Motrice. By 

 Mr. John Fames, F. R. S. N° 45Q, p. 607. 



The last* dissertation is new, and treats of the motive forces of bodies, 

 whether they are to be estimated by the velocities, or the squares of the velo- 

 cities, when the masses are equal. The original of this dispute among the ma- 

 thematicians, the author ascribes to a slip committed by the celebrated Mr. 

 Leibnitz, in the year 1686; and the continuance, to the neglect of the times, 

 in which equal effects are produced. The one side asserts all causes to be equal, 

 whose effects are so, whether the times, during which the causes act, are 

 shorter or longer. The other, on the contrary, maintains, that equal effects 

 may arise from unequal causes, if the times of action are unequal ; that con- 

 sequently ^he times, as well as the effects, ought to be taken into the account. 



He wishes the gentlemen on the other side of the question would produce 

 some experiment in their favour, where the equality of the times is preserved; 

 since all the experiments they have hitherto made, and argued from, may 

 justly be set aside, as incompetent, on account of the inequality of the times of 

 action. 



The author then proceeds to prove the truth of the common opinion of the 

 forces in equal bodies, being proportional to their velocities. This he does by 

 three mediums, the first taken from the action of a single spring on the same 

 body; the second from some experiments of Mr. Mariotte; the third from the 

 joint action of several springs on two unequal bodies. 



* The eight preceding dissertations had been before printed separately ; but were now all collected 

 togetherj with the addition of this ninth, and published in one volume in 8vo. London, 1732. 



