equire a magnetic object in order
to render their presence sensible.

[166] PAGE 78, LINE 14. Page 78, line 16. _Orbem terrarum
distinguunt._--The editions of 1628 and 1633 here add a figure of a globe
marked with meridians and parallels of latitude, but with an erroneous
versorium pointing to the south. These editions also both read
_existentiam_ for the word _existentium_ in line 20.

[167] PAGE 83, LINE 5. Page 83, line 5. _magnes longior maiora pondera
ferri attollit._--Gilbert discovered the advantage, for an equal mass of
loadstone, of an elongated shape. It is now well known that the specific
amount of magnetism retained by elongated forms exceeds that in a short
piece of the same material subjected to equal magnetizing forces.

[168] PAGE 83, LINE 24. Page 83, line 28. _Non obstant crassa
tabulata._--Gilbert has several times referred (_e.g._, on p. 77) to the
way in which magnetic forces penetrate solid bodies. The experimental
investigation in this chapter {47} is the more interesting because it shows
that Gilbert clearly perceived the shielding action of iron to be due to
iron conducting aside or diverting the magnetic forces.

[169] PAGE 85, LINE 26. Page 85, line 31. _non conveniant._--The editions
of 1628 and 1633 both read _et conveniant_.

[170] PAGE 86, LINE 3. Page 86, line 3. _illud quod exhalat._--Literally,
_that which exhales_, in the sense of that which escapes: but in modern
English the verb exhale in the active voice is now not used of the
substance that escapes, but is used of the thing which emits it. It must
therefore be rendered _that which is exhaled_ (_i.e._, breathed out).

[171] PAGE 86, LINE 13. Page 86, line 15. _Ita tota interposita moles
terrestris._--Gilbert's notion that the gravitational force of the moon in
producing the tides acts _through_ the substance of the earth may seem
curiously expressed. But the underlying contention is essentially true
to-day. The force of gravity is not cut off or screened off by the
interposition of other masses. A recent investigation by Professor
Poynting, F.R.S., has shown that so far as all evidence goes all bodies,
even the densest, are transparent with respect to gravitational forces.

[172] PAGE 86, LINE 18. Page 86, line 20. _Sed de aestus ratione
alias._--There is no further discussion of the tides in _De Magnete_. But a
short account is to be found in Gilbert's posthumous work _De Mundo nostro
Sublunari Philosophia nova_ (Amsterdam, E