( 5 5 5 ) 
For want of a rnore convenient Inftrument, I took a 
Whirligig of Wood, fomewhat more than t of an Inch 
thick, and in Diameter at lead i.s Inch. It was turn- 
ed truly round, and had in its Diameter nigh to, and 
equidiftant from the Centre two Holes made, into 
which, as ufual, was a Thread put, of about 40 Inches 
long, and about 20 when it was put in, and the two 
Ends tied together. I went with it to a Clock, whofe 
Pendulum ofcillated Seconds, and working the Whirli- 
gig ftrong enough to make its Returns, or Vibrations, 
keep equal Times with the Pendulum’s Ofcillations, I 
fuddenly caught the Whirligig at the End of one Vi- 
bration before it began another, and then (unt wilting 
the double Thread gradually with my Fingers) I told 
how many Turns or Revolves it had made in that one 
Vibration, and found the Thread untwilled with 58 
Turns (which is but half the Number in one Vibra- 
tion, becaufe in the whole Vibration it was twilled the 
like Number of Turns the other Way) which doubled 
makes 116 Turns in each Vibration, and in one Se- 
cond of Time. I computed the mean Velocity of the 
Circumference thereof in each Second of Time to be 
about 5*4 Feet 7 Inches 9 645', 4606, ^c. Parts. By 
this it is plain, that a Globe (as well as a Wheel) of 
6 Inches in Circumference, if truly centered, is eafily 
capable of being kept in Motion on its Poles, fo fwift 
that its Equator (hall have the Velocity of 5'! Feet 
5*410, 4419, 8, Parts, by making 103.0820.8859, 
(fc. Turns in one Second. This is the proper Velo- 
city for fuch an Experiment, becaufe it is nearly equal 
to that of the North magnetick Pole of the internal 
Loadftone along the Parallel of 13^ Degrees from the 
Poles of its Rotation. 
Z z 
The 
