[260] De Arte Amandi, lib. iii. v. 629.
[261] Ausonii Epist. xxiii. v. 21. The poet afterwards teaches other
methods of secret writing, and Gellius, lib. xvii. cap. 9, mentions the
like.
[262] Colum. De Re Rust. x. 354. and xi. 3, 60.
[263] Plin. lib. xxvi. cap. 8. p. 400.
[264] The sixth observation of the second century is as follows:
_Magnetic waters which act at a distance_. An astonishing effect,
indeed, is produced by the contest of the following waters, which
are thus made. Let quick-lime be quenched in common water, and while
quenching, let some orpiment be added to it (this however ought to
be done by placing warm ashes under it for a whole day), and let the
liquor be filtered, and preserved in a glass bottle well corked. Then
boil litharge of gold well pounded, for half an hour with vinegar in
a brass vessel, and filter the whole through paper, and preserve it
also in a bottle closely corked. If you write any thing with this last
water with a clean pen, the writing will be invisible when dry; but if
it be washed over with the first water it will become instantly black.
In this, however, there is nothing astonishing; but this is wonderful,
that though sheets of paper without number, and even a board be placed
between the invisible writing and the second liquid, it will have the
same effect, and turn the writing black, penetrating the wood and
paper without leaving any traces of its action, which is certainly
surprising; but a fetid smell, occasioned by the mutual action of the
liquids, deters many from making the experiment. I am, however, of
opinion, that I could improve this secret by a more refined chemical
preparation, so that it should perform its effect through a wall. This
secret I received, in exchange for others, from J. Brosson, a learned
and ingenious apothecary of Montpelier.
[265] Tachenii Hippocraticæ Medicinæ Clavis, p. 236. 1669.
[266] Collectanea Chymica Leydensia, edidit Morley. Lugd. Bat. 1684,
4to, p. 97.
[267] For an account of various kinds of secret writing see Halle,
Magie oder Zauberkräfte der Natur. Berlin, 1783, 8vo, v. i. p. 138.
[268] Hist. et Mém. de l’Acad. des Sciences à Paris, 1737, pp. 101 and
228.
[269] Historia Cadmiæ fossilis, sive Cobalti. Berl. 1744.
[270] This account, together with Teichmeyer’s receipt for preparing
it, may be found in Commercium Litterarium Norimbergense, 1737, p. 91.
[271] “Copiosius minera bismuthi tam ab aqua forti quam ab aqua
regia dissolvitur, restante pulvere albo corroso; solutio in aqua
forti roseum colorem sistit, quæ si sali in aqua soluto, secundum
præscriptum D. J. W. in clave, affundatur, abstrahatur, ex residuo
extrahitur sal roseum, quod pulverisari et cum spiritu vini extrahi
potest: adeoque hæc autrix jam anno 1705 publice totum processum et
fundamentum sic dicti atramenti sympathetici, quod a calore viridescit,
evulgavit.”--Pot, Observ. Chym. collectio prima. Berolini, 1739, p. 163.
[272] So thinks Gesner in Selecta Physico-œconomica, or Sammlung von
allerhand zur Naturgeschichte gehörigen Begebenheiten. Stutgard, vii.
p. 22.
[273]
[_Inks formed of solutions _and washed with solutions
of the following salts_, of_ _become_
Muriate of antimony, tincture of galls, yellow.
Green vitriol, tincture of galls, black.
Nitrate of cobalt, oxalic acid, blue.
Subacetate of lead, hydriodic acid, yellow.
Arseniate of potash, nitrate of copper, green.
Nitrate of copper, prussiate of potash, brown.
Solution of gold, muriate of tin, purple.
Perchloride of mercury, hydrochlorate of tin, black.]