( $ 44 ) 
*4 *■ »« ‘ j T ^ • 
V. An Experiment to illuftrate what has been /aid 
in the [ Vhilofophical Tranf actions , N°. 3 86 , 
387, 388, concerning the Figure of the Earth , 
0{fV. J. T. Deiaguliers, L.L.D.F.R.S. 
U P O N an Axis of Iron, that cou’d be made to 
turn fwiftly (by means of a Wheel, whofe 
String went round a Pulley fix’d to the Paid Axis) I 
flipp’d on two Iron Hoops, whofe Planes interfecied 
at right Angles, reprefenting two Colures, which, be- 
ing of a fpring Temper, fprung in fuch Manner as to 
be Part longer in that Diameter that coincided with 
the Axis, than in their ./Equatorial Diameter j this Pro- 
portion being the fame that Mr. Cafjlni fuppofes to 
be between the Axis and ./Equatorial 'Diameter of the 
Earth. Two circular Plates, to which the Paid Hoops 
were riveted, had fquare Holes, thro’ which the 
Axis pafs’d, fo that the two Poles of the oblong 
Spheroid, which the Hoops defcribe in their Revolu- 
tion, might approach together in fuch Manner, as to 
let them put on the Form of a true Sphere, when, by 
the Whirling, the /Equatorial Diameter of the Ma-. 
chine fwell’d and over-power’d the Elafticity of the 
Hoops. A greater Degree of Swiftnefs turn’d the 
Sphere into an oblate Spheroid of Sir Ifaac Fewton's 
Figure. A Velocity Hill greater makes the Difpropor- 
tion of the Diameters, fuch as thofe of Jupiter • ^and 
hill the Equatorial Diameter encreafes with the cen- 
trifugal Force. 
Another Hoop with a Catch, reprefenting the /Equa- 
tor, {hews (m the Experiment) the Increafe of the 
Equatorial Circumference, and an Index applied to 
the Frame, {hews the Increafe of the Diameter. 
As 
