GEOLOGICAL MAI'S. 
389 
been gradually enlarged and converted into a fissure, giving exit to the 
metal, which 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. 
CATALOGUE OF THE GOVERNMENT SUflYEY MAPS AND 
SECTIONS, 
(Continued from imga 345.) 
SHEETS OF THE GOVERNMENT GEOLOGICAL MAP OF ENGLAND AND WALES, 
WITU THE CHIEF GEOLOGICAL FEATUllES IN EACH SHEET, AND ITS PRICE. 
No. 
10 Isle of Wight. Wealden Beds. Cre- 
taceous Strata. Lower Greensand. 
Gault. Upper Greensand. Chalk. 
Eocene Strata. London and Plas- 
tic Clays. 3s. 
I I Oolites (nine subdivisions). Purheck 
Beds. Lower Greensand. Gault. 
Upper Greensand. Chalk. Plastic 
• ■ Clay. 6s. 
15 Oolites. Coral Rag. Kinimeridgo 
Clay. Portland Beds, to the Pur- 
beck Beds of the Vale of Wardour 
inclusive. Hastings Sands. Weald 
Clay. Gault. Upper Greensand. 
Chalk. 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 New 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 Red Sandstone, and Devonian, 
in Somerset, of Lias and Carboni- 
ferou.s Limestone in Glamorgan, 
&c. Gs. 
Hor, Sect., sheet 11. 
