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ening agents (in most cases added as adulterations : — Gypsum, chalk, 

 flour, kelp, lime, and some siliceous and argillaceous matters ; and, in 

 some kinds of litmus, according to Pereira, indigo is frequently added, 

 to heighten the colour." 



The author entered somewhat minutely into the details of the 

 modifications of the typical process of manufacture (as above men- 

 tioned), according to the country where such manufacture is carried 

 on, the species from which the colour is to be extracted, and accord- 

 ing as the dye is prepared on the large or small scale, &c. ; and as 

 instances of these local and other modifications, he referred to the 

 mode of preparing " scrottyie" and " korkalett" by the Shetland pea- 

 santry ; of various kinds of " corkir," by the Scotch, Irish, and Welsh ; 

 and various kinds of orchil and litmus, on the Continent, as detailed 

 by BerthoUet, Hellot, Micheli, Neumann, Willemet, and others. 



Mordants are necessary for the fixation of the colour of most, if not 

 all, of the lichen-dyes, which are characteristically very fugitivS ; 

 these accessories, however, seldom acting as mere media of con- 

 nexion between the fabric and dye, but usually also brightening, or 

 otherwise modifying, the natural colour of the latter. Westring depre- 

 cated mordants, under the impression that they would destroy the 

 gummy constituents of the lichens, which he supposed to be the 

 source of the fixation of the colouring matters. That mordants are 

 not essential adjuncts to the process of dyeing, is rendered probable 

 by the statements of Westring and others, as to their having obtained, 

 without such aid, colours, if not absolutely permanent, still sufficiently 

 so to resist the action both of acids and alkalies, and long exposure 

 to the solar rays. From the transient character of the colours yielded 

 by the lichen family, it happens that the part they play in the art of 

 dyeing is but secondary, being used chiefly to contribute a peculiar 

 bloom and richness to other days. But this may perhaps be due, in 

 great measure, to the little we at present know of the chemistry of 

 these colouring matters ; and we may yet discover means of rendering 

 them equal to our cochineals, logwoods, and indigoes ; while they are 

 (or might, at least, be) far superior in point of cheapness. And we 

 have yet to acquire a very great amount of infomiation as to the 

 colour-yielding powers of the lichens (apart altogether from the ques- 

 tion of fixity, or permanence, of tint), which we never shall obtain till 

 this family has been extensively examined, with this special object in 

 view, both at home and abroad. Hoff'mann mentions that the nature 

 of the water used in making the various baths, through which the 

 fabric is passed in the process of dyeing, is important. In Franco 



