( >43 ) 
XIII. An Account of an Experiment contrived by 
G. J. s’Gravefande, Trof.Matb. at Leyden, 
E <^.S. relating to the Force of moving Bo- 
dkSyJbeum to the Royal Society, by J. T, 
Defaguliers, LL. T>. and E <S. 
H Aving la ft Year (hewn feveral Perfons in Hol- 
land the Experiment contrived by Mr. Geo. 
Graham , to explain the Do&rine relating to the Mo- 
mentum of Bodies (viz. That the Momentum or 
Quantity of Motion in Bodies is always as the Mafs 
multiplied into the Velocity) which Experiment is 
made with a flat, pendulous Body, that receives the 
Addition of a Weight equal to itfelf at the lower 
Part of its Vibration, and by the Reception of that 
equal Quantity of Matter always lofes half its Ve- 
locity. Dr. Mufchenbroeh, Profeflor of Mathe* 
maticks and Aftronomy at Utrecht , communica- 
ted to me the following Experiment, made in Op- 
pofition to that which I (hewed, by Mr. Profeflor 
s'Gravefande. In this laft a Spring equally bent 
every time, pulhes forward, unequal Quantities of 
Matter fucceflively, and in every Experiment the Pro* 
du£t of the Mafs of the Body by the Square of the 
Velocity is the fame ; and therefore, as the Quantity 
of Motion muft always be the fame from the fame 
Caufe ( viz. the fame Tenfion of the Spring) it fol* 
lows, by every Experiment, that it is as the Mafs mul- 
liplied intothe Square of the Velocity. 
Exp. i.] 
) 
