TRACT 36. THE WHIRLING-MACHINE.

1-73

Arru .tn.£weights

Time of

12 ‘unis

'Pi me of

1 turn

oz dr

2 8

2 94 -

2 loi

2 11

2 12

158"

1 46 ~

1 ‘12

H li140

13 %

124

I

11 4

Hence then, with the velocity of 1 turn in 1I-| seconds,the arm and plane side of the body are resisted with theforce or weight of 2 oz 12 dr; but, on the 2d of May, theresistance to the arm and round side of the body was 1 oz12 dr; and, on the 3d of May, the resistance to the armalone was 12 dr; all with the same velocity nearly. Sub-tracting now 12 dr, the resistance on the arm, from each ofthe other two, there remain 2 oz for the resistance to the flatside, and 1 oz nearly for that on the convex side; the latterbeing nearly the half only of the former, and therefore, inthis case, nearly agreeing with the theory.

Dividing now this 2 oz by 51 • 1, the ratio of the radii of

20

the barrel and centre of the body, there results j- = ‘039 oz,for the absolute resistance of the flat surface of a circle,moved perpendicularly through the air, with a velocity of2*394 feet in a second, the area of the circle being 32 squareinches, or J. of a square foot.

May 8, 1786.

Barometer 29*66 ; Thermometer 56.

15. Tried several different weights, to bring the largehemisphere flat side, also the arm without it, to revolve eachtime in 10 seconds. Then again, the same body, both sidesforemost, and the arm alone, all in 8 seconds, each turn:The particulars are as follows.