USES OF LICHENS. 



85 



are bound to confess, is in a most unsatisfactory condition : 

 we stand much in want of a series of investigations on the 

 composition and products of the Lichens before it can be 

 properly understood; for hitherto scientific evidence has 

 either been excessively vague or contradictory. In their 

 commercial form the purple colouring matters of Lichens 

 constitute the pigments termed respectively Orchill, Cud- 

 bear, and Litmus, which may be practically regarded as 

 various names for the same substance, which differs in 

 character according to differences in the mode of its pre- 

 paration, — Orchill being its English, Cudbear its Scotch, 

 and Litmus its Dutch name, — the first being manufactured 

 in the form of a liquid or paste of a rich purple colour, the 

 second occurring in the form of a powder of a crimson or 

 carmine tint, and the third being met with only in the 

 form of small oblong cakes of an indigo-blue colour. Their 

 colour is naturally reddish : the blue tint is communicated 

 by the addition of alkalies, while consistence is produced 

 by chalk, gypsum, and similar substances in a state of pow- 

 der. These colouring matters, in some of their forms, have 

 probably been known from remote antiquity. There is 

 reason to believe that the dye mentioned in Ezekiel (c. xxvii. 

 v. 7) — "Blue and purple from the isles of Elishah was 



