Geology and Physical Geography, 313 



Sir R. Murchison remarked on the small physical extent 

 of the Purbeck strata compared with their palaeontological 

 importance, confirming the belief that a whole epoch may be 

 represented by a few feet of deposit. — Professor Owen con- 

 firmed the inference of Professor Forbes respecting the 

 connection of the Wealden with the oolites ; of the large 

 Wealden Reptilia, all except the Iguanodon were oolitic and 

 not cretaceous. — Professor Ramsay stated that the whole 

 oolitic series had been deposited in a diminishing area, with 

 the land rising to the west, and the last of the series, the 

 Wealden, had been deposited in the estuary of a great river, 

 which must have flowed from the north-west at a time when 

 what is now Wales and Derbyshire was very high land. — 

 Professor Forbes observed, that no inference as to the age 

 of the Purbecks could be drawn, without the evidence of 

 geological position ; the freshwater mollusca and Cyprides 

 diff*er less from living British species than the living species 

 differed from those of other countries ; the Wealden of Scot- 

 land was not identical with that of England, but probably 

 belonged to an older period. 



Mr Ormerod next read a paper " On the Gradual Sub- 

 sidence of a Portion of the Surface of Chat Moss, in Lanca- 

 shire, by Drainage." — This was the continuation of a paper 

 read at the Swansea meeting. It was shown by a series of 

 levellings made in the last four years, over an extent of about 

 200 acres, where drainage was carried on, that a subsidence 

 had taken place to the amount of one foot per annum. 



Mr Bryce described " the Lesmahago and Douglas Coal 

 Field," and exhibited maps and sections. — This coal-field 

 forms a distinct barrier from all the rest, being separated by 

 a barrier of old red sandstone ; it measures about ten miles 

 by five or six, and contains twelve or fourteen beds of coal, 

 amounting in all to sixty-five feet, one bed being fifteen feet 

 thick, and another nine. In some of tlie deep valleys the 

 coal is worked on a level Several beds of clay-ironstone 

 occur, averaging eight inches thick, and one black band (bitu- 

 minous ironstone) eleven inches thick, is found throughout 

 the northern part. Fire-clays have been noticed under some 



