ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixxxix 



acid from the decaying vegetable matter has united with protoxide of 

 iron to form the carbonate*. 



On the theory of the formation of the ironstone bands and nodules 

 of the coal-measures, which, as you know, often contain impressions 

 of plants and also freshwater shells, our author makes the following 

 observations : — '' The clay or argillaceous ironstones are formed of 

 carbonate of iron, mingled mechanically with earthy matter, com- 

 monly corresponding with that constituting the shales with which 

 they are associated. In many of the underclays of the coal the ore oc- 

 curs in nodules irregularly distributed. Mr. Hunt, of the Museum of 

 Economic Geology, instituted a series of experiments to illustrate the 

 production of these clay ironstones, and he found that decomposing 

 vegetable matter prevented the further oxidation of the protosalts of 

 iron, and converted the peroxide into protoxide of iron, by taking a 

 portion of its oxygen to form carbonic acid. Under the conditions 

 necessary for the production of the coal distributed among the asso- 

 ciated sand, silt and mud, the decomposition of the vegetable matter 

 would necessarily form carbonic acid among other products. This 

 carbonic acid mixed with water would spread with it over areas of dif- 

 ferent dimensions accordingtocircumstances; forming salts and meeting 

 with the protoxide of iron in solution, it would unite with the protoxide 

 and form a carbonate of iron. The carbonate of iron in solution would 

 mingle with any fine detritus which might be held in mechanical sus- 

 pension in the same water, and hence when the conditions for its deposit 

 arose, which would happen when the needful excess of carbonic acid 

 was removed, the carbonate of iron would be thrown down mingled 

 with the mud f ." If not in sufficient quantity to form continuous 

 beds, it would aggregate into nodules, and be arranged in planes amid 

 the mud, in the same maimer as is so commonly seen to be the case 

 with argillaceous limestones and nodules of various geological ages. 



PALEONTOLOGY. 



During the course of the past year several important contributions 

 have been made to this department of our science, both at home and 

 abroad. Through the liberality of Mr. Richard Griffith, a valuable 

 account has been published of the Silurian fossils of Ireland, drawn up 

 by Mr. McCoy, and illustrated by excellent figures. Numerous new 

 species, many of them of great interest, are described, and the locali- 

 ties from whence the specimens had been collected are fully stated. 

 This work throws new light on the relations of the English and Irish 

 Silurian strata. 



In the Journal of our Society for the year 1846 are many contri- 

 butions to British palaeontology, but to these it is unnecessary for me 

 to refer. In the course of the year, the first number of a new peri- 

 odical work appeared, ' The London Geological Journal and Record 

 of Discoveries in British and Foreign Palaeontology,' which contains 

 some interesting communications respecting new British fossils from 

 Eocene, Cretaceous and Permian strata. We find in it a memoir by 

 Mr. Series Wood, in which he has announced the discovery of an 

 * Pages 51, 52, 53, 255, 264. t Page 185. 



