[210] Theophrast. De Lapidibus, edit. Heinsii, fol. p. 395, and Plin.
lib. xxxvii. c. 3, and lib. viii. c. 38.
[211] Epiphanius De XII Gemmis.
[212] J. de Laet De Gemmis. 1647, 8vo, p. 155.
[213] Phil. Trans. vol. li. 1. p. 394.
[214] Recueil de Mem. sur la Tourmaline, par Æpinus. Petersb. 1762,
8vo, p. 122.
[215] Gemm. et Lapidum Historia. 1647, 8vo, p. 441, 450.
[216] Plin. lib. xxxvii. c. 7.
[217] India produces also the lychnites, the splendour of which is
heightened when seen by the light of lamps; and on this account it
has been so called by the Greeks. It is of two colours; either a
bright purple, or a clear red, and if pure is thoroughly transparent.
When heated by the rays of the sun, or by friction, it attracts
chaff and shavings of paper. It obstinately resists the art of the
engraver.--Solinus, c. lii. p. 59. Traj. 1689, fol.
[218] “Hager albuzedi is a red stone, but less so than the hyacinth,
the redness of which is more agreeable to the eye, as there is no
obscurity in it. The mines where this stone is found are in the
East. When taken from the mine it is opake; but when divested of its
outer coat by a lapidary, its goodness is discovered, and it becomes
transparent. When this stone has been strongly rubbed against the hair
of the head it attracts chaff, as the magnet does iron.”--Serapionis
Lib. de simplicibus medicinis. Argent. 1531, fol. p. 263.
[219] Curiöse Speculationes bey Schlaf-losen Nächten, 8vo, Chemnitz,
1707. The author’s name appears to be expressed by the initials I. G.
S. This work consists of forty-eight dialogues, each twelve of which
have a distinct title.
[220] Frankf. 1713, 8vo.
[221] I shall here lay before the reader the whole passage, taken from
Histoire de l’Académie for 1717, p. 7:--“Here we have a small magnet.
It is a stone found in a river of the island of Ceylon. It is of the
size of a denier, flat, orbicular, about the tenth part of an inch in
thickness, of a brown colour, smooth and shining, without smell and
without taste, which attracts and afterwards repels small light bodies,
such as ashes, filings of iron, and bits of paper. It was shown by M.
Lemery. It is not common, and that which he had cost twenty-five livres
(about twenty shillings sterling). When a needle has been touched with
a loadstone, the south pole of the loadstone attracts the north pole
of the needle, and repels its south pole: thus it attracts or repels
different parts of the same body, according as they are presented to
it, and it always attracts or repels the same. But the stone of Ceylon
attracts, and then repels in the like manner, the same small body
presented to it: in this it is very different from the loadstone. It
would seem that it has a vortex....”
[222] “I must not omit to mention that the rivers contain the electric
stone, which is of the size of a halfpenny, flat, orbicular, shining,
smooth, of a brown colour, one-tenth of an inch in thickness, without
smell and without taste, and which attracts light bodies, such as
ashes, filings of iron, shavings of paper, &c., and afterwards repels
them. A wonderful and singular property, discovered and observed in
this stone alone, when neither heated by motion nor by friction.”
[223] [Light is called polarized, which, having been once reflected
or refracted, is incapable of being again reflected or refracted in
certain positions of the second medium. Ordinarily, light which has
been reflected from a pane of glass or any other substance, may be a
second time reflected from another surface, and will also freely pass
through transparent bodies. But if a ray of light be reflected from a
pane of glass at an angle of 57°, it is rendered totally incapable of
reflexion from the surface of another pane in some positions, whilst it
will be completely reflected by it in others. If a plate of tourmaline,
cut in the manner described above, or a Nichol’s prism be held between
the eye and a candle, and turned slowly round in its own plane, no
change will take place in the image of the candle; but if the plate or
prism be fixed in a vertical position, on interposing another of the
same kind between the former and the eye, parallel to the first, and
turning it round slowly in its own plane, the image of the candle will
be found to vanish and re-appear alternately at each quarter turn of
the plate, varying through all degrees of brightness down to total or
almost total evanescence, and then increasing again by the same degrees
as it had before decreased. These changes depend upon the relative
positions of the plates; when the longitudinal sections of the two
plates are parallel, the brightness of the image is at its maximum; and
when the axes of the sections cross at right angles, the image of the
candle vanishes. Thus the light, in passing through the first plate of
tourmaline, has acquired a property totally different from the ordinary
light of the candle; the latter would penetrate the second plate
equally well in all directions, whereas the altered light will only
pass through it in particular positions, and is altogether incapable of
penetrating it in others. The light is polarized by passing through the
first plate or prism. Thus, one of the properties of polarized light is
proved to be the incapability of passing through a plate of tourmaline
perpendicular to it in certain positions, and its ready transmission in
other positions at right angles to the former.]