Notices of Memoirs — E. Wethered on Formation of Coal. 469 



VII. — On the Fokmation of Coal, By Edward Wetheked, 



F.C.S., F.G.S. 



i~pHE author first reviewed the researches of Hutton, Goeppert, 

 J_ MacCullocli, Sir James Hall, Sir W. Logan, and Dr. Dawson, 

 and then summed up the conclusions now entertained as to the 

 formation of Coal, as follows : — 



1st. That the beds of fii'e-clay which underlie all seams of coal 

 represent the original land-surfaces upon which the coal-forming 

 vegetation grew. 2nd. That the Stigmaria found in the underclays 

 were the roots of that vegetation, which implies that the plants were 

 of the Lepidodendroid order. 3rd. That the vegetation grew near 

 the mouths of great rivers, in swampy ground, and there underwent 

 submergence ; changes then took place which converted the vegetable 

 matter into coal. 4th. That the change of coal from one variety to 

 another, even in the same seam, is the result of metamorphism, and 

 is indirectly caused by the contortion of the surrounding strata, 

 wherebj^ facilities for the escape of gases evolved by the vegetable 

 decomposition have been produced. 



The author's exceptions to the above were — 1st. That coal was 

 not formed from trees of the Lepidodendroid type, and that therefore 

 the Stigmaria found in the underclays are not the roots of the 

 vegetation which gave rise to the coal, unless it was from the 

 spores of such plants, which the author considered wanting in proof, 

 though some coal did undoubtedly contain spores of some kind. 

 2nd. That the varieties of coal, and the change which sometimes 

 takes place in one and the same seam, are not due to metamorphism, 

 nor are they dependent upon the contorted state of the surrounding 

 strata, but arise from the greater or less chemical decomposition of 

 the vegetable mass, influenced by the circumstances under which it 

 was submerged. 



The reasons which had led up to these conclusions were : — 1st. 

 That we have proof of other vegetation during the coal-pei'iod besides 

 the Lepidodendra, but their roots have not been preserved, owing to 

 their being of a more perishable nature than the Stigmaria. 2nd. 

 Beds of underclay are frequently met with, full of Stigmaria, but are 

 not followed by seams of coal. 3rd. Coal must have been formed 

 from a compact mass of vegetation, such as could not have been 

 produced by large trees (as the Lepidodendra were) growing in situ. 

 The uniform thickness and comparative freedom from inorganic con- 

 tamination would demand a mass of vegetation into which only a 

 limited amount of sediment could penetrate. 4th. The finding of 

 a fossil tree standing in situ, upon which so much stress had been 

 laid by some authors, is a rarity. Though the author had spent 

 much time underground in collieries, and seen hundreds of fossil 

 trees drifted into the position in which they have been found, he had 

 only twice seen instances of them standing where they have grown. 

 6th. If seams of coal were formed from Lepidodendroid trees, the 

 tough bas-layer would be easily detected, which has never been the 

 case in any true bed of coal. 6th. If the Stigmaria found in the 



