50 SECTIONAL ADDRESSES. 



call allochthony ; more simply by drift ; or were they formed, like peat, 

 by the growth of vegetable material in its place — the process of 

 autochthony ? 



I do not intend to labour the answer to this question. Categorical 

 arguments in favour of the growth in place origin of the coal-forming 

 vegetation are on record, and they have never been as categorically 

 answered. Many arguments in favour of the Drift Theory seem to me 

 clearly to have arisen from confusion between cannel and true coal. 

 This distinction is again fundamental. True coal-seams are charac- 

 terised by : • — • 



(1) Wide extent. 



(2) Uniformity of thickness and character over extensive areas. 



(3) Freedom from intermingled detrital mineral matter. 



(4) Constant presence of a seat-earth or rootlet bed. 



(5) Entire absence of remains of aquatic animals within the seam. 

 Substitute affirmatives for negatives, and negatives for affirmatives, 



and the characteristics of cannel are as truly set forth. The whole 

 subject has been exhaustively reviewed with all the resources of wide 

 study and great field experience in Professor J. J. Stevenson's memoirs 

 or monographs entitled I'espectively The Formation of Coal Beds and 

 Inter-relation of Fossil Fuels, volumes which are treasure-houses of 

 facts. Without a familiar knowledge of these two masterpieces of 

 scientific induction, no geologist is fully equipped for an inquiry into 

 the Geology of Coal. Not the least ai-resting chapters are those in 

 which the author demonstrates the inadequacy of river-drift to provide 

 materials for the formation of a coal-seam. He shows that even when 

 in high flood the gross amount of timber, drift-wood and general raffle 

 of plant detritus carried along and available for the purpose of coal- 

 seam formation is quite insignificant. He gives many citations from 

 reports of geologists and others, as well as from his own experience, 

 to show that when a flooded river sweeps through a forest it scarcely, 

 if at all, disturbs the humus. 



Haigh-Moor or Deltaic Swamp. 



Granted, therefore, that coal-seams were, in the main, formed by 

 the growth, death, and accumulation on the spot of plant tissues after 

 the general manner of beds of peat, our next inquiry must be into the 

 further and consequent question : What type of modern peat-growth 

 most nearly i-epresents the conditions of the old peat areas? Were 

 they upland or lowland peats ; were they wet or dry ? If in search of 

 an answer to this question we examine a section of Coal Measures 

 strata in which coal-seams are included, we find a series of well- 

 stratified layers of sandstones, shales, and the like, exhibiting general 

 regularity of bedding, fine lamination of the layers, and the frequent 

 occurrence of beds charged with the remains of aquatic animals, some 

 marine and some of fresh-water habitat. We cannot fail to recognise 

 in this the inexpugnable evidence of a lowland area undergoing inter- 

 mittent depression, such as would bring in, at one time, the muds and 

 sands of an area of alluvial drainage, and, at another time, even the 

 sea. We are presented, then, with a clear initial conception of a vast 



