Correspondence — Mr. Mellard Eeade. 143 



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

 appearance is fai* more consonant with partial differentiation of 

 the original magma, followed by fluxional movements and flow- 

 brecciation. It is not that a mass of arapbibolite 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 Vosges 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 wlaich were obtained from the Chalk of the zone of Tere- 

 hraltd'ma gracilis. The larger weighed 7 lb. 7 oz., and measured 

 5''-8 X 6"-25 X 4""125, and consisted of decomposed granite; valves 

 of Spondyhis latns and Serpula were still attached. The other, also 

 granite, though of a different cliaracter, weighed 3 lb. 12 oz., and 

 measured 3"-6 x 5"*8 x 4:"-5. Professor 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 Fossil Plant considered with reference to the 

 Origin, Composition, and Formation of Coal-beds." By W. S. 

 Gresley, Esq., F.G.S. 



The author argues that the brilliant black lamina in coal and 

 similar materials to those which 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 Platycerinm 

 alcicome, whicli 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 

 which accumulated on the floors of sheets of water. 



coI^I^:E]s:F035^x):EIs^o:E. 



THE GEEAT SUBMERGENCE "AGAIN." 



Sir, — Has Mr. Dugald Bell adopted this title to show his surprise 

 that the so-called " Submerger " has not been extinguished by his 

 numerous writings on the subject ? 



Unless I have completely misunderstood the tenour of these com- 

 munications, Mr. Bell formerly attached great importance to the 

 supposed absence of high-level shelly Boulder-clay in the South of 

 Scotland, as favouring his view that the Drift was due to land-ice : 

 hence his strenuous endeavours to prove that such shelly beds did not 



