s sive de Arte Magnetica_ (Coloniae, 1643),
and other writers of the seventeenth century. Curiously enough, its
adoption to denote the pivotted magnetic needle led to the growth of an
erroneous suggestion that the mariners' compass was known to the ancients
because of the occurrence in the writings of Plautus of the term
_versoriam_, or _vorsoriam_. This appears twice as the accusative case of a
feminine noun _versoria_, or _vorsoria_, which was used to denote part of
the gear of a ship used in tacking-about. Forcellini defines _versoria_ as
"funiculus quo extremus veli angulus religatur"; while _versoriam capere_
is equivalent to "reverti," or (metaphorically) "sententiam mutare." The
two passages in Plautus are:

EUT. Si huc item properes, ut istuc properas, facias rectius,
Huc secundus ventus nunc est; cape modo vorsoriam;
Hic Favonius serenu'st, istic Auster imbricus:
Hic facit tranquillitatem, iste omnes fluctus conciet.
(in _Mercat._ Act. V., sc. 2.)

CHARM. Stasime, fac te propere celerem recipe te ad dominum domum;
. . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . Cape vorsoriam
Recipe te ad herum.
(in _Trinum._ Act. IV., sc. 3.)

The word _magneticum_ is also of Gilbert's own coinage, as a noun; as an
adjective it had been certainly used before, at least in its English form,
_magneticall_, which appears on the title-page of William Borough's
_Discourse of the Variation of the Compasse_ (London, 1596). Gilbert does
not use anywhere the noun _magnetismus_, _magnetism_. The first use of that
noun occurs in William Barlowe's _Magneticall Aduertisements_ (1616), in
the _Epistle Dedicatorie_, wherein, when speaking of Dr. Gilbert, he says
"vnto whom I communicated what I had obserued of my selfe, and what I had
built vpon his foundation of the _Magnetisme_ of the earth." Gilbert speaks
of the _virtus magnetica_, or _vis magnetica_; indeed, he has a rich
vocabulary of terms, using, beside _virtus_ and _vis_, _vires_, _robur_,
_potestas_, _potentia_, _efficientia_, and _vigor_ for that which we should
now call _magnetism_ or _the magnetic forces_. Nor does he use the verb
_magnetisare_, or its participle, _magnetisatus_: he speaks of _ferrum
tactum_, or of _ferrum excitatum a magnete_. In spite of certain
obscurities which occur in places in his work, he certainly sh