19S

EXPERIMENTS WITH

TRACT 36,

other; the first position being 0°, or horizontal, with itsedge to the air ; and the last 90°, or the plane vertical, withits face directly opposed to the path or resistance of the air.In the second line are the intervals of time in performingeach revolution, expressed in seconds and hundredth parts;each number, as usual, being a medium of several repetitions.

Note, The area of the plane is 32 square inches, or J sq.foot, and = the circle of the large hemisphere.

The radius of revolution to centre of the plane 53-J inches.

Circumference described by its centre in 1 revolution 337'7inc. or 28'14 feet.

Ratio of radius of axis to radius of revolution, as 1 to51 *51, accounting the radius of axis to the middle of thethread, 1044 inches.

July 25, 1788.

Barometer 60'10; Thermometer 66.

48. Used the same brass plane again, set at various an-gles as Before, but fixed on the contrary wav, viz, the breadthor shorter dimension in the direction of the arm; but stillhaving its centre at the same distance of 53-J- inches from thecentre of motion; to try if there be any difference by suchchange of position ; the actuating weight being still the same32 ounces.

Times of Revolution, with the Plane crosswise.

0° orhoriz.

5°

10°

20°

80°

o

o

45°

b

60°

70°

80°

90° „ r

U'l-f.

l-00"il-] 7'

l *: 5'

1-69"

2-00"

2-30"

2'57"

2-80"

2-()3"

3-00"

3-08'

Here, as before, the first line contains the inclination ofthe plane to the direction of motion, and the second the me-dium times of revolution. The inclination of 45° was notused this day ; but it was tried in two different ways the daybefore, viz, inclined 45* backwards, thus \ , and then inclined45° forward, thus/', when the result was the same in bothcases: whence it may be concluded, that the resistance is thesame, whether the plane is inclined forward or backward, ateach angle of inclination, as indeed it might be expected.