( ) 
The Velocity of the faid raagnetical Pole of the 
internal Loadftone is, as above, in the Time of 4 Mi- 
nutes, in Inches and Decimal Parts 148438.1075,7963, 
52.51, 
And therefore in the Time of one Minute 37109. 
5518,9490,8813,0469,786^ and in one Second 618.4925,5158,181 3, 
5507,82973 which 618.4925, ^c. Inches reduced to Feet 
and Decimal Parts, is 5' 1.5410,4429,8, 
Suppofe then a TerreJla was made of jufl 6 Inches 
in Circumference N.« S;? (^Fid. Fig. i. -P/.) con- 
trived to gyrate on Poles n chofen in any two oppo- 
lite Points of its magnetical Tiquator, and the Axis of 
its Rotation n fituated (as near as Art can do it) in 
the magnetical Line , for in this Pofture of the Axis the 
magnetical Poles of the Terrella will be equally 
wrought on by the Earth’s attradive Point all the 
Way as it is turned round, which can be in no other 
Pofture whatfoever ; , For if the Axis of its Rotation- 
makes the leaft Angle with the magnetical Line, as 
the Terrella is turned round, the magnetick Poles of 
it will be attraded and repelled more when on one 
Side than when on the other, which ought not to be, 
becaufe it is probable it may have the fame Effed which 
a large Magnet would have, if held within the At- 
tradion, and confequently change the Polarity, as 
by a Touch, and not purely by the Gyration there- 
of. 
The Circle N .s Sn reprefents the Terrella in Cir- 
cumference juft 6 Inches (having both, or at leaft one, 
of its attradive Poles nicely marked) cemented, or 
bound with Thread fall: to a cylindrical Veftel of Wood, 
or Brafs pretty thin, that it may not be too heavy, 
with its Polarity N S tranfverfe to the Axis of the 
faid: 
