44 Reports and Proceedings — Geological 8ociety of London. 



the latter is traversed by the central or northern part of cyclones 

 during the whole year. The area of Pleistocene glaciation in 

 America and Europe coincides with the areas now traversed by the 

 most regularly frequented storm-tracks. There seems to have been 

 about the same difference between the mean annual temperatures of 

 Europe and North America in the Great Ice Age as now, and it 

 is generally agreed that a lowering of the present snow-line by 

 1,000 metres would give rise to a similar Ice Age. The hypothesis 

 that a glaciation of North America would raise the temperature of 

 Europe, and vice versa, seems to the author physically untenable. 

 The positions and movements of anticyclones are not generally ruled 

 by the ground temperature in our latitudes : they are in most cases 

 eddies formed by the air- circulation in general, and in this the 

 greater area and receipt of heat by the Equatorial regions must 

 always be a preponderating factor. The author considers that the 

 influence of the Glacial Period on atmospheric circulation would 

 probably be similar to that of a cold Winter nowadays. The cyclones 

 would be gradually deviated into a more and more southerly track, 

 while an anticyclone would be formed in the north, not, however, 

 a stationary one, but travelling like a cyclone, only more slowly and 

 irregularly. The Summer must have been cold and stormy, with 

 frequent fogs, somewhat like that of Cape Horn or Kerguelen Island 

 at the present day. The author considers that Mr. Harmer under- 

 rates the effect of isolation and overrates that of the winds. " The 

 temperature of the Summer only is essential for the phenomenon of 

 glaciation." 



3. " On the Origin of certain Concretions in the Lower Coal- 

 measures." By H. B. Stocks, Esq., P.I.C, F.C.S. (Communicated 

 by Professor W. W. Watts, M.A., F.G.S.) 



In certain of the Lower Coal-measures of Lancashire and York- 

 shire and in the ' hard-bed coal,' peculiar concretions known as 

 ' coal-balls ' occur, which have a considerable interest because they 

 contain well-preserved plant-remains. The author's analysis shows 

 that they consist mainly of calcium-carbonate and iron-pyrites, 

 in varying proportions. Carbonate of lime appears to have been 

 introduced by osmosis through the cell-walls ; and that it was 

 introduced in small quantity and under exceptional circumstances 

 appears to be proved by the comparative rarity of the concretions 

 and their presence in this seam of coal only. During the decay of 

 the vegetable matter of which coal is formed, in contact probably 

 also with animal matter, some of the organic matter would pass 

 into solution in water, causing the absorption of the oxygen in 

 solution ; the result of this is that further decay would take place 

 under anaerobic conditions. This, occurring in water containing 

 sulphates, would give rise to sulphuretted hydrogen and mud 

 blackened by the presence of ferrous sulphide, while carbonates 

 would also be produced. Experiments were tried (1) on the pre- 

 cipitation of carbonate of lime under varying conditions (in presence 

 of organic matter, etc.) ; (2) on the action of salts of lime and of 



