is historical. The church was dedicated to St. John,
but in the custody of the Augustinian monks. The following is the account
of it given by Aldrovandi, _Musaeum Metallicum_ (1648, p. 134), on which
page also two figures of it are given:

"Aliquando etiam ferrum suam mutat substantiam, dum in magnetem
conuertitur, & hoc experientia constat, nam Arimini supra turrim templi S.
Ioannis erat Crux a baculo ferreo ponderis centum librarum sustentata, quod
tractu temporis adeo naturam Magnetis est adeptum, vt, illivs instar,
ferrum traheret: hinc magna admiratione multi tenentur, qua ratione ferrum,
quod est metallum in Magnetem, qui est lapis transmutari possit;
Animaduertendum est id a maxima familiaritate & sympathia ferri, & magnetis
dimanare cum Aristoteles in habentibus symbolum facilem transitum semper
admiserit. Hoc in loco damus imaginem frusti ferri in Magnetem transmutati,
quod clarissimo viro Vlyssi Aldrouando Iulius Caesar Moderatus diligens
rerum naturalium inquisitor communicauit; erat hoc frustum ferri colore
nigro, & ferrugineo, crusta exteriori quodammodo albicante." And further on
p. 557.

"Preterea id manifestissimum est; quoniam Arimini, in templo Sancti
Ioannis, fuit Crux ferrea, quae tractu temporis in magnetem conuersa est, &
ab vno latere ferrum trahebat, & ab altero respuebat." See also Sir T.
Browne's _Pseudodoxia Epidemica_ (edition of 1650, p. 48), and Boyle's
tract, _Experiments and Notes about the Mechanical Production of Magnetism_
(London, 1676, p. 12).

{54} Another case is mentioned in Dr. Martin Lister's _A Journey to Paris_
(Lond., 1699, p. 83). "He [Mr. Butterfield] shewed us a Loadstone sawed off
that piece of the Iron Bar which held the Stones together at the very top
of the Steeple of _Chartres_. This was a thick Crust of Rust, part of which
was turned into a strong Loadstone, and had all the properties of a Stone
dug out of the Mine. _Mons. de la Hire_ has Printed a Memoir of it; also
Mons. _de Vallemont_ a Treatise. The very outward Rust had no Magnetic
Virtue, but the inward had a strong one, as to take up a third part more
than its weight unshod." Gassendi and Grimaldi have given other cases.

Other examples of iron acquiring strong permanent magnetism from the earth
are not wanting. The following is from Sir W. Snow Harris's _Rudimentary
Magnetism_ (London, 1872, p. 10).

"In the _Memoirs of the Academy of Sciences_ for 1731, we find an account
of a large bell at Marseilles h