624 REPORT— 1881. 



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, whereby 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 

 vegetation 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, 

 ainless it was from the spores of these plants, which the author considered by no 

 means proved, though coal undoubtedly did contain spores. 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-period besides the Lepidodendroids, 

 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 Lepidodendroids were) growing in situ. The uniform thickness 

 and comparative freedom from inorganic contamination, would demand a mass of 

 •vegetation into which only a limited amount of sediment could penetrate. 4th. The 

 finding of a fossil tree standing m situ, upon which so much stress had been laid 

 by some authors, is a rarity. Though the author had spent much time under- 

 ground 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. 5th. If seams of coal were formed from Lepidodendroid trees 

 the tough bast layer would be easily detected, which has never been the case in 

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

 roots of the coal- forming vegetation, we should e.xpect to find the fructifications 

 immediately over the coal, which is not the case ; with the exception of Cordaites 

 (which in the author's opinion was a Reed), remains of the fossil flora are not found 

 for the first two feet or so over the coal. 



After a careful investigation underground of the conditions under which coal 

 was formed the author has arrived at the following conclusions : — On the land 

 grew the vegetation of the period, represented by the Lepidodendrons, Sigillaria, 

 Calamites, &c. As the land sank and tlie waters encroached, the land vegetation 

 gradually disappeared, but the roots remained in many cases, and those which 

 offered the greatest resistance to decay are the ones preserved in a fossil state — 

 hence the occurrence of Stigmaria. As the waters advanced, the ground would 

 become swampy, and then we might expect to see spring up reeds, mosses, and 

 other vegetation suitable to the changed condition ; it is to vegetation of this 

 kind that the author ascribes the formation of coal. 



Reference was then made to the Presidential address of Professor Ramsay to 

 the British Association in 1880, in which the recurrence of the same kind of 

 incident through geological time was advocated. The author then asked, why the 

 coal-formations of the Carboniferous period should be an exception, seeing that the 

 modern lignites and deposits of peat were instances of coal in the process of for- 

 mation. It was then pointed out that these deposits were not composed of large 

 trees, but of a lower order of plants. 



Coming to the varieties of coal and the change which sometimes takes place in 

 this respect in one and the same seam, it was shown that the difference between 

 bituminous and anthracite coal was, that the latter contained a greater proportion 

 of carbon and a less amount of volatile matter than the former. It was then con- 

 tended that if the decomposition of the coal-forming vegetation took place without 

 being affected, to any extent, by minerals capable of oxidising the carbon, that a 

 coal would be formed having a large proportion of carbon with a less proportion of 

 volatile matter than is found in bituminous coals. The author explained this by 

 Ijriefly reviewing the process by which vegetable matter has been converted into 



