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I. Certain genera and species of lichens, which are abundant in 
Scotland, and could be collected with comparative facility, and ~ 
at a very moderate expense, might be tried with advantage on 
the large scale, as substitutes for the foreign lichens used in 
the manufacture of orchil, cudbear, and litmus. I have already 
indicated a favourable result in investigating native lichens on 
the small scale; but it remains for the manufacturer to test the 
permanence and utility of colours, which may merely look 
brilliant, without having any fixity. 
If. This subject is worthy of being followed out by the manufac- 
turer on the one hand, and the chemist on the other. 
a. On account of scientific interest—the field being comparatively 
new and open, and at the same time most promising of good 
results. 
b. Were it only with the view of further developing the economic 
resources of our own country. 
c. Because the speculation [7. e., the substitution of home for foreign 
dye-lichens], promises to be remunerative, as the Roccellas have 
frequently reached the high price of £1000 per ton in the 
London market. 
ILI. The collection and transport of lichens, for the purpose of ex- 
amining their colorific powers is very easy, viz. :— 
a. By simple desiccation and packing. 
b. By drying and pulverizing. 
c. By precipitating the colorific principles from a lime-solution or a 
decoction by acetic or muriatic acids. 
IV. The colour of the thallus and that obtained by the action 
of Stenhouse’s or Helot’s tests on solutions of the lichen-colorific 
principles do not always correspond in tint; more frequently 
the reverse obtains: hence, it is impossible from the colour or — 
other external character of the thallus of a lichen to predicate 
the nature of the reaction of its alcoholic solution with chloride 
of lime, or the tint it will yield on ammoniacal maceration. 
V. The lichens richest in colorific principles, capaple of yielding 
valuable colouring matters, are crustaceous and foliaceous spe- 
cies, of a pale or whitish colour — whose alcoholic or aqueous 
infusion is nearly devoid of colour, which grow on rocks or 
stones, and in mountainous countries, or on the sea-coast. 
VI. The lichens most devoid of the same principles are species 
having a showy foliaceous thallus, attaining a considerable size, 
whose alcoholic and aqueous solutions are generally of the 
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