328 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 17, 



molecules in solution. The spicula so abundant in the greensand of 

 Maidstone and its neighbourhood, and in the fossil sponges of Wilt- 

 shire, are never in an unaltered condition ; their surface is always 

 more or less eroded, and sometimes, in parts, nearly eaten through, 

 by the solvent action of the water and carbonic acid ; and I have 

 never yet seen an instance in which a detached spiculum has formed 

 the nucleus for a crop of the radiating crystals of the calcedony, but 

 I have frequently found detached sponge fibres under such circum- 

 stances ; and as we observe them when imbedded in the masses of 

 flint or agate, the deposit most frequently assumes the form of a se- 

 ries of distinct centres of crystallization. Fig. 5. PI. VIII. represents 

 one of these cases from the interior of a flint, and in this instance the 

 deposit has been arrested, and we therefore have the first crops of 

 the crystals covering the fibre in such a form as to give it completely 

 a moniliform aspect. 



If the views which I have endeavoured to establish in this and my 

 former papers on these subjects be correct, we may justly consider 

 the attractive power of organic matter for silex, as one of the great 

 agents established by nature for the consolidation of the soluble sili- 

 cates, liberated and dispersed through the ocean by the gradual decom- 

 position of the compound mineral masses which form the crust of the 

 globe. Vast as these decomposing masses may be, the process ap- 

 pears to be so slow and modified as to render the results as regards 

 the silex scarcely if at all appreciable in the waters of the great rivers, 

 through the means of which it is poured into the ocean ; and how- 

 ever continuous the supply, it is evident that the rapidity and ex- 

 tent of the process of fossilization and of animal assimilation are 

 amply sufiicient to preserve that wise and beautiful equilibrium, 

 which is apparent throughout nature in everything connected with 

 the decomposition and reconstruction of both animal and mineral 

 forms. 



January 17, 1849. 



The following communication was then read : — 



On the Geological Structure of the Alps, Apennines and Car- 

 pathians, more especially to prove a transition from Secondary 

 to Tertiary rocks, and the development of Eocene deposits in 

 Southern Europe. Part II. By Sir Roderick Impey Mur- 

 CHisoN, F.R.S. G.S. L.S., Hon. Mem. R.S. Ed., R.I. Ac, Mem. 

 Imp. Ac. Sc. St. Pet., Corr. Mem. Ac. France, Berlin, Turin, 

 &c. &c. 



[Printed with Part I. in No. 19 of the Journal, p. 157, above.] 



