( 338 ) 
or jarring, which the latter, when in a rapid Motion, 
is fubjed to, and therefore I cannot approve of it, nor 
is the multiplying Power of the Wheels m F, being 
10.3082, c. fo nearly to be calculated for a Wheel 
and Pinion ^ but, if good Work, it may be allowed in 
the Wheels /a, which move flower: But that I ap- 
prehend will needlefly encreafe the Charge. The Di* 
ameter of each Wheel at the Bottom of the Trench, 
where the String touches it, is mentioned in the 
Draught. The whole may be made to turn with one’s 
Hand, either with a Crank in the Arbour of the 
Wheel CL, or with a Turner like that of a Grinding- 
Bone R. 
Mr. JV‘ //, Page 78, makes one Revolution 
of the central Magnet, in refped of the Earth, to be 
not lefs than 1910 Years, which I have reduced to 
701180 Days, to which I add 1910 Days, which 
makes the Sum 703100, being the Number of Revo* 
lutions, nearly, which the Earth and the faid Magnet 
with it, makes in 1910 Years in refped of the fixed 
Stars.* Now fincethe magnetick Pole of a Terrella 6 
Inches in Circumference, centered as above is direded, 
and moving with the Velocity of 5*1 Feet 5'4io-44i9, 
Parts in the Time of one Second, by making 
103.9820,8859, ^c. Turns, moves equally rapid with 
that of the central Magnet, it may be expeded that 
703200 of its Revolutions fhould gradually tranflate 
each of its Poles one entire Circle, which 703100 Re- 
volutions (at 103.0820, Second) will be fi- 
nifhed in the Time of 6811 Seconds 7476,9171,396 
parts, or i 5*3' 41" 44'" 51"" 41""'. Or, 
3 5*1600 Re volut. tranflate it ^ a Circle in 3410.8738, 
4636,198'', or o. 56' 50" 5*1'" 2- 5"" 
175^00 
