61. Reaumur conceived the grains in question to be the eggs or spawn of some fish, but e hether of the buc cinum or any other species, he was uncertain, and under this uncertainty he proposed calling them ce ufs de pour pre, eggs of purple. The colour which they produced was at least equal, if not superior, in beauty, as well as durability, to that of the buccinum ; though the colour ing matter of the latter was much thicker; and passed less quickly through the different shades of colour, on exposure to the light of the sun. He also found that the liquor of the buccinum tasted as hot as the hottest pepper, whilst that of the purple eggs was stiffish. But even the latter was so viscid, that, when topically ap plied to linen, it did not run ; and as the grains were, according to his accounts, so plentiful, that one man might collect half a bushel of them in a few hours, there is certainly reason to conclude, says Dr Bancroft, that they would be highly useful, at least in calico printing, where their liquor might he applied with the greatest facility, both for penciling and printing, as a substantive topical colour, and where a small quantity would go far, especially upon fine muslins.
62. About the beginning of the year 1736, Duhamel discovered the purpura in great abundance upon the coast of Provence. He found the viscid colouring mat ter of the fish to be white, except in a few instances in which it was green, an appearance which he ascribed to disease. The white liquor being exposed to the sun's rays, assumed the following colours : t. A pale yellowish green ; 2. An emerald green ; 3. A dark blueish green; 4. A blue with a tinge of red ; 5. A purple; and these changes all happened in less than five minutes. In all the experiments which were made with the purpura, the presence of light was lound essential to the forma tion of the purple colour; and the effect was produced most expeditiously when the influence of the sun's rays was most powerful.
63. Little doubt can now be entertained of the identity of the shell-fish employed by the ancients, and those dis covered by Cole, Heauniur, and Duhamel. Both Ari stotle and Pliny have informed us, that the liquor of the purpura was white ; and the latter also remarks, that the purple colour which it afforded was not instanta neously produced, but after a succession of several co lours, of which green* was one. We have also a de scription of the manner of catching the shell-fish, em ployed for the purple dye, written by an eye witness, Eudocia Macrembolitissa, daughter of the emperor Constantine the Eighth, who lived in the eleventh cen tury, while the knowledge of dyeing the Tyrian purple still remained; and from which it appears, that the ancient purple did not acquire its due lustre and per fection until it had been exposed to the sun's rays.
64. Berthollet is inclined to believe, that the changes, which the liquor of the purpura and buccinum under goes by exposure to the sun's rays, are owing to the absorption of oxygen ; but Dr Bancroft, who has exa mined this subject very minutely, has ascertained that the purple colour is produced without the access of air, and that its formation is more probably owing to the extrication of oxygen. Having procured, in the month
of September 18u3, a large quantity of shell-fish, ap parently of the same species with those which Mr Cole had employed, and agreeing in their specific characters with the buccinum laldllus of Linnaeus, he made a great number of experiments with the liquor which yielded the purple colour, from which he found reason to con clude, that the presence of light was essentially neces sary to its production, and that the change of colour was effected most speedily when the substances stained with the liquor were exposed to the deoxidizing rays. Some bits of muslin which he had stained with the liquor, and preserved between the leaves of a book, re tained their original yellowish colour for nearly nine years ; and on being exposed after that time to the rays of the sun, they were found as capable as ever of exhi biting all the changes of colour, and at last becoming purple.
65. A species of buccinum has also been found on the coasts of Guayaquil and Guatemala in South Ame rica, which appears to have been long used by the na tives for dyeing or staining cotton. Don Antonio Ulloa describes them as larger than a nut, and containing a juice, which, when expressed, is the true purple ; for,. he adds, if a thread of cotton, or the like, be dipped into this liquor, it becomes of a most vivid colour, which repeated washings are so far from obliterating, that they rather improve it ; nor does it fade by wearing. He mentions also, that the purple colour does not appeal immediately, the juice being at first of a milky colour, Ir %r r h it el- s to a •reem a al Lott) to this ee 1 bt. t,..d I yr; Ic. I. t. p. 2 "i 06 it the Bahama Islands, (soI. t p tit ) m nuns ng the shells found there, a p• a tea of buectnum w h )1cItled a pulpit.: liquor like not_ murcx, and %%bleb did not wash out of linen st 1 w an it. Joss, lyn also, in his .Veta England res- a biac,vcred... p. 37. say s, at l'aschataway, a plan ut.J1, ab..ut league. by sea eastward of Boston, in a son c•‘e called Baker's Cove, they found this kind of mus. Ic, which hats a purple vein, which being prick ed a Ith a needle, yieldeth a perfect purple or scarlet jut e, d)eing linen so that no washing will wear it out, but Let ps its lustre many years : we mark our hand Iscrehiels and s iirts with it." Mr John also relates, that abundance of purple snails are found in the islands over against Bata% ia." "They are boiled," sass he, " and eaten by the Chinese, who have a way of polishing the shells, and pick out of the middle of the swill a certain purple-coloured substance, which they use in colouring, and in making red ink.