AUSTEN EXTENSION OF THE COAL-MEASURES. 39 



was one of contracting areas, by the conversion of sea-bed into 

 land-surface. This process was one of almost endless alternation 

 from one state to the other ; but the general tendency was to an in- 

 crease on the side of dry land. It is only towards the upper portions 

 of the palaeozoic group that we acquire any definite boundaries for 

 areas of land and water : it is on the correct restoration of these lines 

 that the following speculations are mainly founded. With respect to 

 those terrestrial masses which are represented only by the oldest 

 palaeozoic groups, it may suffice to say that they have mostly disap- 

 peared. We can, however, ascertain something as to their mineral 

 composition, and the spaces they occupied ; and in this way we can 

 sketch out the surface of the Northern Hemisphere under its earliest 

 arrangements. These differed widely from such as obtain now. The 

 land was mainly extra-European ; and it must be obvious to every geo- 

 logist who has a clear view present to him, of the large proportion in 

 which sea-bed of subsequent date constitutes the present European 

 land-area, at how early a date some of these early features began to 

 be effaced. Any restoration of the European surface for this very 

 early period must be purely ideal ; whilst the restoration of the many 

 land-surfaces of the true Carboniferous period is real, — what was dry 

 land then has, in many instances, continued so ever since, and is so 

 now. 



2. Of the widely spread terrestrial surface of the true coal-measure 

 period, portions attained a considerable vertical elevation. The evi- 

 dence of this may be derived either from the character of part of the 

 vegetation of the period ; or from the scale of the alluvial action of 

 that time. In contrast to this, there is a feature which seems to 

 distinguish this period physically from all subsequent periods, and 

 which consists in the vast expanse of continuous horizontal surface 

 which the land-area presented, bordering on, and at very slight ele- 

 vations above, the sea-level. 



3. All coal may be taken as the product of a vegetation which grew 

 on the spots where it is now found : the extreme purity of the car- 

 bonaceous matter, however thin the seams may be, is sufficient proof 

 of this. There may have been accumulations of drifted vegetable 

 matter then, as now ; but no true coal-stratum was ever so formed. 

 The botanical character of the coal- vegetation does not belong to this 

 inquiry ; it can, however, be divided into upland and lowland ; and as 

 to that of the low-level surface, it must have been composed of dense 

 growths of like plants, such as were capable of maintaining them 

 selves, like the peat-vegetation of modern times, for indefinite periods 

 over the same spots. 



From the Valley of the Roer to that of the Scheldt, near Valenciennes, 

 there extends for 170 miles from E. to W. a continuous band of pro- 

 ductive coal-measures. This great coal-field has usually been de- 

 scribed as situated on the north-west edge of a mass of older rocks, 

 of which a principal part is known as the Ardennes range : such is, 

 however, rather a geographical than a geological account of its posi- 

 tion, as it omits considerations of some importance. On the north- 



