300 Royal Society, 



lava and trachyte, vast masses of matter containing the alkalies, 

 lime and magnesia, in what I have termed a dormant condition, that 

 is, so united by the force of cohesion and of chemical affinity as not 

 to be readily disengaged and carried off by water. * * * * 



" Now nature has provided, in the carbonic acid which is so 

 copiously evolved from volcanos, and which consequently impreg- 

 nates the springs in those very countries, more particularly where 

 volcanic products are found, an agent capable, as completely as 

 muriatic acid, though more slowly, of acting upon these descriptions 

 of rock, of separating the alkali and alkaline earths, and of present- 

 ing them to the vessels of plants in a condition in which they can 

 be assimilated. 



" Thus every volcanic as well as every granitic rock contains a 

 storehouse of alkali for the future exigences of the vegetable world, 

 whilst the former is also charged with those principles which are 

 often wanting in granite, but which are no less essential to many 

 plants — I mean lime and magnesia. 



" Had the alkalies been present in the ground in beds or isolated 

 masses, they would have been speedily washed away, and the vege- 

 tables that require them would by this time have been restricted to 

 the immediate vicinity of the ocean." — P. 701. 



XLIII. Proceedmgs of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 231.] 



Feb. 10, " "JpXAMINATION of the Proximate Principles of the 

 1848. -L* Lichens." By John Stenhouse, Esq., Ph.D. 



The author, after adverting to the labours of Robiquet, Heeren, 

 Dumas, and Kane in the investigation of the i^roximate principles of 

 the lichens, especially of those which yield red colouring matter with 

 ammonia, and also of the more recent inquirers on this subject, such 

 as Schunck, Rochleder, Heldt and Knop, M'ho have greatly extended 

 our knowledge of this interesting but difficult department of organic 

 research, proceeds to state that nearly two years ago his attention 

 was directed by Dr. Pereira to a kind of Orcella weed, which had 

 been recently imported into London from the Cape of Good Hope, 

 but which had been rejected by the London archil manufacturers 

 as being unfit for their use, from the small quantity of colouring 

 matter it yields M'hen subjected to the usual process. With a view 

 to ascertain whether or not the red dyes obtained from the various 

 lichens result from the action of ammonia on a certain crystalline 

 principle, described by Schunck under the name of Iccanorine, the 

 author procured quantities of the several lichens usually employed 

 by the archil makers, and subjected them to investigation ; the minute 

 details of Avhich, together with the results, are given at length in the 

 present paper. 



The specimens examined are the following : — 



