208 PHILOSOPHICAL TRAJMSACTIONS. [aNNO 1/05. 



Experiments on the Resilition of Bodies in common Air, also in Vacuo and in 

 condensed Air; made at a Meeting of the Royal Society at Gresham College. 

 By Mr. Francis Haukshee. N° 298, p. 1946. 



Having provided a tall glass receiver, in the upper part of which I had a con- 

 trivance to lodge 4 marbles, and from whence I could at pleasure drop them 

 successively on a plane. The distance descended by each marble to the plane, 

 was about 134- inches; the weight of two marbles 59 grains, of the other two 

 63 grains; being all of the sort usually sold at toy shops. The plane on which 

 they fell, was a round flat piece of solid glass, about an inch thick, and S-^ over 

 the upper surface being well ground and polished. It was fixed in a tin frame, 

 contrived on purpose to keep its lower surface from being contiguous to the 

 plate or leather, on which the recipient was placed. On dropping the marbles 

 on the said glass plane, their resilition then was something more in vacuo than 

 in common air; and those dropped in common air had likewise some small ad- 

 vantage in their rebound, above those let fall in condensed air; the condensa- 

 tion being but one atmosphere; not daring to venture more, the breaking of 

 the recipient being very hazardous. The resilition of the marbles from the 

 plane in vacuo vt^as about 1 04- inches, which was something more than -f- of their 

 descent: in condensed air their rebound was about 10 inches: so that we must 

 account their resilition in common air to be the medium of the other two, it 

 being difficult to judge to a nicety in so sudden a motion. But there was a 

 sensible difference between the rebound of those dropped in vacuo, and those 

 in condensed air. I could not observe that the small difference in the weight 

 of the marbles made any discernible alteration in their resilitions. 



An Experiment on t/ie Descent of Malt Dust in the evacuated Receiver, at 

 Gresham College. By Mr. Fr. Hauksbee. N° 298, p. 1948. 



I took some malt dust, and having dried it well, put a quantity of it into a 

 fine muslin bag, where being loosely inclosed, it would upon shaking discover 

 itself plentifully in the open air, undulating and floating a considerable time 

 before it would descend ; but being included within a receiver, from which the 

 air was well exhausted, and then shaken, the dust decended like a ponderous 

 body, precipitating in straight lines from the top to the bottom of a tall 

 receiver. 



