902 



4. Tests and processes for estimating qualitatively and quantita- 

 tively the colorific powers of individual species, with their practical 

 applications. 



5. Processes of manufacture of the lichen-dyes, on the large and 

 small scale, in different countries, with the principles on which they 

 are founded. 



6. Nomenclature of the dye-lichens, and of the lichen-dyes. 



7. Botanical and commercial sources of the same. 



8. Special applications of the lichen- dyes in the arts. 



9. Commercial value of the dye-lichens, and their products. 



10. Geographical distribution of the dye-lichens, with the effect of 

 climate, situation, &c., on their colorific materials. 



In the former part of this paper, the subjects mentioned under the 

 1st and 2nd of these heads were considered, and on the present occa- 

 sion those included in the 3rd and 4th. Of these four sections of the 

 paper, the following is a very short summary, or synopsis : — 



Under the 1st head, the author spoke of chlorophylle, and various 

 organic and inorganic substances which enter into the formation of 

 the colours of the thallus and apothecia of lichens, and of the modi- 

 fications of these colours depending on various degrees of — 1. Expo- 

 sure to air and light. 2. Temperature. 3, Moisture, &c. 4. Atmos- 

 pheric vicissitudes. 5. Season of the year. 6. Natin-e of the gonidic 

 reproduction {i. e., gemmation). 7. Nature of habitat. 8. Organic 

 decomposition. 9. Coalescence of parts, monstrosities, &c. 



Under the 2nd section, he traced historically the manufacture of 

 lichen-dyes, and the native use of lichens as dye-agents, among diffe- 

 rent nations, from the times of Theophraslus, Dioscorides, and Pliny 

 down to the present day j sketching briefly the ancient and modern 

 history of orchil, cudbear, and litmus, and specifying the native use 

 of lichen-dyes in different countries of Europe, Asia, and America. 

 He alluded more particularly to their application to the dyeing of 

 yarns, &c., by the Scotch highlanders, under the name of " crottles." 

 " The process of manufacture of the various crottles, generally con- 

 sisted in macerating the powdered lichen for two or three weeks in 

 stale urine ; exposing the mass freely to the air, by repeated stirring, 

 and adding lime, salt, alum, or argillaceous and other substances, 

 either to heighten the colour, or impart consistence. To such an 

 extent did this custom at one time prevail, that, in several of our 

 northern counties, each farm and cottage had its tank or barrel of 

 putrefying urine, — a homely, but perfectly eflicient, mode of generat- 

 ing the necessary amount of ammonia. In the county of Aberdeen 



