1XXXV1 PROCEEDINGS OF THE GEOLOGICAL SOCIETY". [May 1911, 



present-day representative of the growth and preservation of car- 

 bonaceous matter on the scale of the Coal-Measures has yet been 

 found. The nature of the vegetation must have been such that it 

 could spread and nourish under the peculiar swamp conditions that 

 prevailed, and yet be suitable to provide the class of material which 

 would give origin to coaly matter. Last, but not least, the climate 

 must have been such as to encourage rapid growth of rank vege- 

 tation ; yet it must have allowed, in place of ordinary decay, a 

 decomposition capable of permitting the storage of the numerous 

 hydrocarbons which go to make up the coal. 



Several of these conditions may have occurred more than once 

 during geological ages in single localities and for short periods 

 of time, and to this must be due the lignite seams of several 

 of our formations. But the coincidence of them all and for the 

 enormous period of timo comprehended by the strata of our Coal- 

 Measures is likely to be only a rare event; and it is remarkable 

 that, during the Jurassic Period in Britain, there should be so near 

 an approach to a recurrence of the conditions necessary to make a 

 valuable coalfield. 



The study of our British Coalfields seems to show that, even with 

 the conditions so highly favourable as they were in our area, the 

 most favourable conditions of all were concentrated in particular 

 and limited regions. Tracing such a seam as the Thick Coal of 

 South Staffordshire towards the border of its area of deposition, 

 we find it rapidly passing into irregular and worthless carbonaceous 

 sediment. Tracing it away from this line, we find it passing into its 

 most concentrated and highly valuable condition. Beyond this, its 

 constituent seams become divided and spread apart by the inter- 

 vention of wedges of sediment which thicken out towards the 

 north. Others of the coal-seams take on similar changes until, 

 as Prof. Charles Lapworth pointed out in his valuable report 

 to the Coal Commission, the coal-seams of North Staffordshire are 

 contained in three or four times as much mechanical sediment as 

 in the South Staffordshire Field. 



In "the same way, at approximately like distances from the 

 southern land-barrier, the coal-seams of the Warwickshire Coalfield 

 undergo a like change from south to north. Thus there would 

 appear to occur, even in the regions of favourable sedimentation, a 

 condition of things approximately parallel to the coast-line, capable 

 of giving origin to a concentration of vegetable accumulation, 

 correlated perhaps with less and more steady and regular move- 

 ment than elsewhere. Mr. Wade has published evidence from the 



