GEOLOGICAL MAPS. 



389 



been gradually enlarged and converted into a fissure, giving exit to the 

 metal, -^hicli would, besides undergoing rapid transport by water and 

 its own gravity, be quickly disseminated through the porous vegetable 

 soil by capillary attraction. Adopting this causation, I see no reason 

 why the mercury in Tertiary sands, as noticed by the late Mr. Sharpe, 

 in Portugal, or in the fissures of the calcareous conglomerate at Mont- 

 pellier, or even the Lombardian deposit (Cividale), should not be con- 

 sidered as derived from adjacent formations of, if I may use the expres- 

 sion, a more congenial antiquity. It would be well if those who have 

 observed this metal in recent deposits would extend their examination 

 to neighbouring rocks (supposing such to exist) of an older date ; and 

 there would scarcely be, I conceive, a more interesting, or certainly 

 more practically useful, branch of physical geology than would result 

 from a gathering and arrangement of the facts relating to the age of 

 metalliferous deposits, and the distinguishing of those rocks to which 

 they are specially restricted for their matrix, from those in which they 

 have become reintegrated, as it were, after being transported from other 

 formations. 



CATALOGrE OF THE GOYEENMEl^T SUEYEY MAPS AND 



SECTIONS. 



{Continued from page 345.) 



SHEETS OF THE GOVEENMENT GEOLOGICAL MAP OF ENGLAND AKD WALES, 

 WITH THE CHIEF GEOLOGICAL FEATURES IN EACH SHEET, AND ITS PRICE. 



No. 



10 Isle of Wight. Wealden Beds. Cre- 

 taceous Strata. Lower Greensand. 

 Gault. Upper Greensand. Clialk. 

 Eocene Strata. London and Plas- 

 tic Clays. 3s. 



14 Oolites (nine subdivisions). Purbeck 



Beds. Lower Greensand. Gault. 

 Upper Greensand. Chalk. Plastic 

 Clay. 6s. 



15 Oolites. Coral Bag. Kimmeridge 



Clay. Portland Beds, to the Pur- 

 beck Beds of the Vale of Wardour 

 inclusive. Hastings Sands. Yfeald 

 Clay. Gault. Upper Greensand. 

 ChaUi. Eocene Strata (seven sub- 

 divisions). 6s. 



16 Oolite Beds. Cretaceous and Eocene 



Strata. 6s. 

 Yert. Sect, sheet 22. 



No. 



17 Lias. Oolites. Cretaceous Beds. 



Outliers of Plastic Clay. 6s. 

 Hor. Sect., sheets 19, 20, 21, 22. 

 Vert., Sect., sheet 22. 



18 ISTew Red Sandstone. Lias. Oolite. 



Cretaceous Beds. 6s. 



Hor. Sect., sheets 19, 20, 21, 22. 



19 Mendip Hills. Somerset Coal Fields. 



Oolitic and Chalk deposits. 6s. 

 Hor. Sect., sheets 14, 15, 16, 17, 

 20, 21, 22. Vert. Sect., sheets 

 11, 12. 



20 Carboniferous Limestone of the Men- 



dips across Bleadon Hill to the 

 Bristol Channel. Bounds of Lias, 

 New Bed Sandstone, and Devonian, 

 in Somerset, of Lias and Carboni- 

 ferous Limestone in Glamorgan, 

 &c. 6s. 

 Hor. Sect., sheet 11. 



