1 38 Mr. edgeworth’s Experiments upon 
Having fattened a ttrong joitt of wood from one fide of a 
large room to the other, fo as to form a kind of bridge at fome 
diftance from the floor, I erefled a perpendicular fliaft or 
roller, which turned freely in brafs fockets fixed into the floor 
and bridge upon pivots of hardened fieel one-fixteenth of an inch 
in diameter. On each fide of this roller was extended an arm 
of deal, feather-edged, and fupported by flays of the fame 
material, feathered in the fame manner, to oppofe as little 
furface as pofllble to the air when in motion. 
Round the upper part of this roller was wound a firing of 
cat-gut, which, patting over putties properly difpofed, was 
fattened to a fcale that delcended into the well of an adjoining 
flair- cafe. 
The extremity of thefe arms defcribed a fpace of more than- 
forty feet in every revolution, the weight defcending in the 
fame time only fix inches. The time in all the following ex- 
periments was the fame ; and, as each revolution was per- 
formed in four feconds, the velocity of the end of the arm on 
which the furface was fixed, was at the rate of about feven 
miles an hour. 
The firft figure that I tried was a parallelogram of tin, nine 
inches long, and four inches wide. Its longeft fide was placed 
parallel to the floor, at the extremity of one of the arms. Its 
fhortettlides were inclined to an angle of forty-five degrees from 
the perpendicular, and in this fituation it was carried round 
with its furface againfl the air. 
After rufrering it to revolve until I was fatisfied that its mo- 
tion was become uniform, I put as much weight into the fcale 
as moved it with a velocity of five turns in twenty feconds. I 
then changed the fituation of the parallelogram, placing its 
fhorteft fides parallel to the floor, and inclined to the fame 
3> angle 
