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some early period of the earth's history, that which we know as the South Wales 

 Coalfield extended very many miles northward and eastward of its present site, 

 and included in its area the carboniferous formations of the Dean Forest, the Clee 

 hills, and other places, at a time when much of the Old Red Sandstones of Here- 

 fordshire was overlaid by some important mineral. 



A few minutes more may perhaps be usefully occupied in considering the 

 manner in which coal was formed and deposited. It is a subject which has been 

 much discussed, but upon which geologists are by no means agreed. On exam- 

 ining sandstone and shale, it is easy to perceive from their texture and composi- 

 tion, that they must at one time have been )espectively loose sand and mud, borne 

 down by, and deposited from, water; but the case is somewhat different with Coal. 

 This mineral being chiefly composed of carbon, hydrogen, and- oxygen, and reveal- 

 ing in its mass evidence of vegetable structure, no doubt is entertained of its 

 organic origin. But whether the plants of which it is composed were drifted 

 down by rivers, and deposited along with layers of mud and sand in estuaries, or 

 whether dense forests and peat mosses were submerged, and then overlaid by 

 deposits of sand and mud, are the two main questions at issue. According to the 

 latter hypothesis, the vegetable matter must have grown and accumulated in 

 dense jungles and peat mosses for many years ; then the land must have sunk 

 and become the basin of a lake or estuary, into which rivers carried mud and 

 sand ; these covered the vegetaljle matter itself, which then underwent the pro- 

 cess of bituminisation and mineralisation, and was converted into Coal. This 

 being done, or while in process of being done, it is supposed that the area of 

 deposit was again elevated, or at least so far silted up and rendered so shallow 

 as to become once more the scene of luxuriant vegetation ; again submerged in 

 the process of gradual subsidence, and overlaid by new deposits of sandstone and 

 shale ; once more shoaled and covered witli plants, and then submerged ; and 

 this alternating process of submergence and shoaling is presuined to have taken 

 place as often as there are beds of Coal in any jiarticular coalfield. The other 

 hypothesis is, that while partial elevations and submersions of land might have 

 taken place, as at the present day, and jungles, pine-swamps, and peat mosses 

 been thereby thrown beneath the waters, the great masses of the Coal Measures 

 were deposited as drift and silt in lakes and estuaries, that the vegetable matter 

 of which Coal is composed was carried into these estuaries by rivers and inun- 

 dations, and that various rivers might discharge themselves into one estuary, 

 some chiefly carrying down sand, while others transported plants, mud, and 

 heterogeneous debris. This hypothesis also supposes that the transporting rivers 

 were subject — like the Nile, Ganges, &c. — to periodical inundations, and that 

 during the intervals of overflow the deltas were choked with a rank growth of 

 vegetation which, in conjunction with the vegetable drift from inland, went to 

 the formation of beds of Coal. These hypotheses are known as the " terrestrial " 

 (or " peat-moss ") and "drift " theories. There is truth in both. We see in some 

 thick, continuous, and pure beds of Coal, the remains of submerged j)eat-mosses 

 or pine swamps ; in others the matted [masses of drift vegetation, enclosing shells 

 and fish-bones ; in some, the upright trunks and accumulated foliage of gigantic 



