as in the other; and that Like Parts of their Surfaces are Cap'd or Arm'd
with Iron; then the Weights they sustain will be as the Squares of the Cube
Roots of the Weights of the _Loadstones_; that is, as their Surfaces."

Upon lifting-power see also D. Bernoulli, _Acta Helvetica_, iii., p. 223,
1758; P. W. Haecker, _Zur Theorie des Magnetismus_, Nuernberg, 1856; Van
der Willigen, _Arch. du Musee Teyler_, vol. iv., Haarlem, 1878 ; S. P.
Thompson, _Philos. Magazine_, July, 1888.

In the book of James Hamilton, p. 5, he mentions a small terrella weighing
139 English grains, which would sustain no less than 23,760 grains, and was
valued at L21 13s. 10-3/4d.

{49} In the _Musaeum Septalianum_ of Terzagus (Dertonae, 1664, p. 42) is
mentioned a loadstone weighing twelve ounces which would lift sixty pounds
of iron.

Sir Isaac Newton had a loadstone weighing 3 grains, which he wore in a
ring. It would lift 746 grains.

Thomson's _British Annual_, 1837, p. 354, gives the following reference:
"In the _Records of General Science_, vol. iii., p. 272, there is an
interesting description of a very powerful magnet which was sent from
Virginia in 1776 by the celebrated Dr. Franklin to Professor Anderson, of
Glasgow. It is now in the possession of Mr. Crichton. It weighs 2-1/2
grains, and is capable of supporting a load of 783 grains, which is
equivalent to 313 times its own weight."

[180] PAGE 99, LINE 10. Page 99, line 11. _Manifestum est._--In this, as in
many other passages, Gilbert uses this expression in the sense that _it is
demonstrable_ rather than meaning that _it is obvious_: for the fact here
described is one that is not at all self-evident, but one which would
become plain when the experiment had been tried. For other instances of
this use of _manifestum_ see pages 144, line 20; 158, line 19; 162, line
10.

[181] PAGE 100, LINE 20. Page 100, line 24. _si per impedim[=e]ta ...
pervenire possunt._--All editions agree in this reading, but the sense
undoubtedly requires _non possint_. Compare p. 91, line 21.

[182] PAGE 102, LINE 4. Page 102, line 4. _capite_ 4.--This is a misprint
for _capite_ 40, and is retained in the later editions. In the quotation
from Baptista Porta, where the English version of 1658 is adhaered to, the
words "& deturbat eam" have been omitted by the translator.

[183] PAGE 107, LINE 16. Page 107, line 18. _Cardanus scribit._--The
alleged perpetual motion machine is mentioned in _De rerum var