38 The Carboniferous Formation. 



been furnished with an inexhaustible supply of sediment, which 

 clearly implies the drainage of a large Continent or Island. 3. 

 That large forests must have existed in the swamps of the delta, 

 which must have lived and died without being disturbed, while 

 their remains were deposited without the intermixture of earthly 

 particles. The absence of all earthly particles from a body of 

 water sufficient to carry away the roots, stems, and leaves of trees 

 and of ferns, may at first sight seem a difficuly, but when we look 

 at the state of existing deltas, our problem will be immediately 

 solved. In the delta of the Mississippi for instance, we find the 

 forest covered swamps surrounded by a belt of reeds, which filter 

 the water before it passes through the swamps, and therefore the 

 vegetable matter in these swamps is accumulated with the same 

 absence of foreign materials. 



The association of fresh and brackish water with marine strata 

 is common both in the British Isles and America. Thus in the 

 mountain limestones of East Lothian beds of sandstone, replete with 

 the remains of lepidodendron and stigmaria, are found alternating 

 with bands of limestone entirely composed of corals or beds of 

 shale filled with brachiopoda of the genera productus, spirifei', etc., 

 and other marine mollusca. In the limestones at Burdie House, near 

 Edinburgh, ferns and other vegetable remains occur in beds which 

 are at the same time rich in the remains of large predacious fishes. 

 It would seem, therefore, that these strata were formed in an 

 estuary, parts of which may have been covered by the sea for 

 centuries together, and then again turned into dry land. 



Botanists used to consider, says Sir C. Lyell, that the flora of 

 the coal implied a hot temperature, but it seems probable that it 

 must have needed a moist rather than an equatorial atmosphere. 

 The preponderance of ferns indicates a humid and even tem- 

 perature, combined with freedom from frost, and we know too 

 little of the sigillaria and other peculiar forms of the coal to 

 speculate what temperature they may have required. 



The second division of the carboniferous period is the " moun- 

 tain limestone." It will, perhaps, be better to describe the 

 mountain limestone as displayed in East Lothian, rather than give 

 a general description of it. 



The mountain limestone of this county can be divided into two 

 sections : the upper consisting of seams of coal, with two beds of 

 limestone ; and the lower of beds of limestone, alternating with 

 strata of sandstone and shale. In the uppermost portion of the 

 upper division there are two beds of limestone, the upper one 

 characterized by the presence of various corals (cyathophyllum, 

 clysiophyllum, etc.), and the lower by containing several species of 

 productus and enorinites. The beds which are below these contaia 



