Coal : a new Explanation of its Formation. 395 



to one which, has consisted mainly of olivine, she maintains that 

 this appearance is far more consonant with partial differentiation of 

 the original magma, followed by flnxional movements and flow- 

 brecciation. It is not that a mass of amphibolite passes into one of 

 serpentine, but that a specimen of the latter is occasionally streaked 

 by the former. 



By comparison with other serpentines of the Yosges and else- 

 where, which are admittedly developed from olivine-rocks, so much 

 likeness is found between them and the Rauenthal mass, that the 

 origin must be similar. 



2. ' On Two Boulders of Granite from the Middle Chalk of 

 Betchworth (Surrey).' By W. P. D. Stebbing, Esq., F.G.S. 



The author notices cases of occurrence of boulders in Chalk 

 which have been previously described ; and records the occurrence 

 of two boulders which were obtained from the Chalk of the Tere- 

 bratidina-gracilis zone. The largest weighed 7 lb. 7 oz., measured 

 5"*8x 6"*25x4"-125, and consisted of decomposed granite ; valves 

 of Sjoondylus latus and Serjiula were still attached. The other, 

 also granite, though of a different character, weighed 3 lb. 12 oz., 

 and measured 3"*6 X 5"*8 X 4"*5. Prof. Bonney has furnished a 

 description of the microscopic characters of the two boulders, 

 which are possibly of Scandinavian origin. The author discusses 

 the mode of transport to their present position, and favours the 

 agency of floating ice. 



3. ' Coal : a new Explanation of its Formation ; or the Phe- 

 nomena of a New Eossil Plant considered with reference to the 

 Origin, Composition, and Eormation of Coal-beds.' By W. S. 

 Gresley, Esq., E.G.S. 



The author argues that the brilliant black laminae in coal and 

 similar materials to those that form these laminae, which are found 

 in earthy coals, shales, and clays, point to the former existence of 

 an aquatic plant, having the general shape of the modern Platy- 

 cerium alcicorne, which grew in situ. He believes that much coal 

 was formed by this aquatic ' coal-plant,' which grew amongst the 

 mechanical sediments and the debris of the terrestrial vegetation 

 that accumulated on the floors of sheets of water. 



March 10th.— Dr. Henry Hicks, E.B.S., President, 

 in the Chair. 



The following communications were read : — 



1. ' Volcanic Activity in Central America in relation to British 

 Earthquakes.' By A. Gosling, Esq., H.M. Minister & Consul- 

 Generalin Central America. 



The author of the communication points out that the volcano of 



