It was for a long time believed that the Dutch prepared their lacmus from those linen rags which in the south of France are dipped in the juice of the _Croton tinctorium_[89]; and this idea appeared the more probable, as most of this _tournesol en drapeaux_ was bought up by the Hollanders: but, as they are the greatest adulterators of wine in Europe, they may perhaps have used these rags to colour Pontack and other wines. It is however not improbable that they at first made lacmus of them, as their dye approaches very near to that of archil. At present it is almost certainly known that _orseille en pâte_ is the principal ingredient in _orseille en pierre_, that is in lacmus[90]: and for this curious information we are indebted to Ferber[91]. But whence arises the smell of the lacmus, which appears to me like that of the Florentine iris? Some of the latter may, perhaps, be mixed with it; for I think I have observed in it small insoluble particles, which may have been pieces of the roots. The addition of this substance can be of no use to improve the dye; but it may increase the weight, and give the lac more body; and perhaps it may be employed to render imperceptible some unpleasant smell, for which purpose the roots of that plant are used on many other occasions. Another kind of lichen, different from the roccella, which in commerce is known by the names _orseille de terre_, _orseille d’Auvergne_, is used also for the like purpose; but it contains fewer and weaker colouring particles. This species, in botany, is called _Lichen Parellus_ (_Lecanora Parella_), and is distinguished from the roccella by its figure, as it grows only in a thin rind on the rocks. It is collected in Auvergne, on rocks of granite and volcanic productions, and in some parts of Languedoc; the greater part of it is brought from St. Flour. Its name, _perelle_, comes from an old Languedocian word _pére_ (_pierre_, a rock); as _roccella_, afterwards transformed into _orseille_, is derived from _rocca_. The use of _perelle_ is very trifling: the Dutch purchase it to make lacmus, perhaps on account of its low price. This lichen has been found also in Northumberland[92] and other mountainous districts of Great Britain, but it is not collected there for any purpose. FOOTNOTES [66] In the Dictionary of the Academy della Crusca the word _oricello_ is thus explained: Tintura colla quale si tingono i panni, che si fa con orina d’uomo, e con altri ingredienti. [67] Historia Muscorum, Ox. 1741, 4to, p. 120. [68] Hist. Plant. iv. c. 7. [69] Lib. iv. c. 95. [70] Lib. xxvi. c. 10; xxxii. c. 6.