[554] Paris, 1753, 12mo, i. p. 368, tab. 6. Duhamel has committed a double error. He speaks of the invention as if the first experiments were made in Spain, and as if those in Austria had been later. He says also, that the latter were made _dans le Luxembourg in Istria_. The English account also says erroneously Luxembourg, instead of Lachsenburg or Laxemburg, which is in Austria, and not in Istria. [555] Of Segni an account may be found in Notizie degli Scrittori Bolognesi raccolte da Giovanni Fantuzzi. In Bologna 1784-1794, 9 vols. 4to, vii. p. 377. Segni, who died in 1610, wrote a great many ascetic books, the names of which are there given. [556] Dell’ agricultura, dell’ arti e del commercio. Lettere di Antonio Zanon. In Venezia 1764, 8vo, vol. iii. p. 325. [557] Prodromo, overo saggio di alcune inventioni nuove, premesso all’ arte maestra. In Brescia 1670, fol. p. 96, fig. 26. [558] See the excellent account of the agriculture in Suffolk in my Journal, the Beytragen zur Oekonomie, &c., i. p. 1. It was written by M. F. Wild, of Durlach, who in the year 1767 was one of my pupils, and afterwards became teacher in the Institute of Education at Colmar. But alas! I do not know whither he has now been swept by the vortex of the revolution. [559] Leske Reise durch Sachsen. Leipzig, 1785, 4to, p. 319. [560] Sylva Sylvarum, cent. 5, § 442. MANGANESE[561]. That the art of glass-making may have arisen from an accident, such as that mentioned by Pliny[562], I am ready to admit; but by what accident were artists made acquainted with the use of manganese, a mineral the outward appearance of which seems to announce nothing that could be useful to the glass-maker? It is not found in such abundance as to allow us to suppose that it naturally presented itself; nor do we know that any older application of it may have induced the ancients to employ and examine it in such a manner that the present use of it might be accidentally discovered. In general, it resembles some kinds of iron-stone, which it was considered to be till a very late period. That iron, however, colours glass must have been very early remarked; and therefore it could occur to no one to employ manganese for depriving frit[563] of its colour. It produces this decoloration only when it is added sparingly, and according to a determinate proportion; otherwise it gives to the glass a violet colour, something similar to that of the amethyst.