86 



carbonic acid and water under the influence of light, and consequent 

 purification of the atmosphere ; and he insisted chiefly on the fol- 

 lowing points : — 



1. That this change is probably gradual; the carbonic acid being 

 taken into the juices of the plant and slowly decomposed there, more 

 or less completely, according to circumstances, whence result not only 

 starch or its allied compounds, but likewise different organic acids 

 and various oils. 



2. That the formation of sugar in plants is probably to be regarded 

 rather as a simply chemical action than as a result of vital affinities ; 

 or that it is a first proi" t of the decomposition of starch by the 

 agency of water and oxygen. 



3. That, on the other hand, the formation of lignin, containing 

 more carbon and less oxygen, from starch or from cellulose, and from 

 the carbonic acid and water brought into the cells, appears to be the 

 result of a strictly vital affinity, strongest at the period of greatest 

 vigour of the plant. 



4. That in this, as in other of the metamorphoses which take 

 place in living beings, and which he proposes farther to examine, 

 the carbon, thus originally fixed on the earth's surface from the at- 

 mosphere, appears to be the chief material employed by nature for 

 the formation of all organized structures, and to be invested, for that 

 purpose, with peculiar and transient vital affinities, while oxygen 

 hardly appears to exert any chemical powers in living bodies, dif- 

 ferent from those which it manifests elsewhere ; but is taken into 

 the interior of all living bodies, only that it may support the excre- 

 tions which are continually going on in them, and resolving organized 

 into inorganic matter ; and thus, that it gradually resumes its power 

 over the carbon which had been temporarily separated from it for 

 the formation of the animated part of creation. 



The following Donations to the Society's Library were an- 

 nounced : — 



The Journal of Agriculture, and the Transactions of the Highland 

 and Agricultural Society of Scotland, for March 1846. — By 

 the Society. 



Journal of the Asiatic Society of Bengal. No. 160, for 1845. — By 

 the Society. 



Life and Correspondence of David Hume. From the Papers be- 

 queathed by his Nephew to the Royal Society of Edinburgh, 



