13" THE QUESTION OF WORKAIiLE 



Now, as the detritus derived from the higher land regions 

 together with the vegetable matter of the Coal accumulated along 

 the margins of the earlier continental regions of elevation to a 

 thickness in the British area of over 15,000 feet (and equal to the 

 aggregate of maximum thicknesses of all the British Secondary and 

 Tertiary formations), certain mechanical results must have followed. 

 The enormous additional burden thus imposed upon these areas of 

 deposition would tend to depress them. Such a force acting verti- 

 cally downwards would be resolved partly into lateral thrusts tending 

 (i) to pinch-up in places the Carboniferous limestone floor of the 

 sea at greater distance from the land, giving rise to new and minor 

 axes of elevation ; (2) to increase the elevation of the land-regions 

 from which the detrital material had been derived followed or 

 accompanied by increased degradation of their materials. There is 

 evidence of the latter having actually occurred, in the conglomerates 

 and sandstones of earlier Permian strata (known as the Rothlie- 

 gendes), some of which are shore deposits, while others of vast 

 thicknesses, as in Thuringia and in Devonshire, bear evidence (us 

 shown in my recent papers on the Devon Red Rocks in the 

 " Journal of the Geological Society ") of having accumulated on the 

 flanks of great mountain regions of older land. In parts of 

 Germany and Austria these Rothliegende strata even contain work- 

 able Coal-seams, a fact which testifies to their land origin ; in other 

 cases the Coal-Measures proper are worked beneath them, as they 

 are in Notts and elsewhere beneath the red strata of the Trias, 

 which in many cases overlap both Permian strata and Coal- 

 Measures. But we cannot go here into details. 



Further movements of the crust occurred during that long 

 period in which the sandstones, pebble-beds, and marls of the Trias 

 (one of the most puzzling of all geological systems) were deposited, 

 by which large marine basins were formed, the outline of which we 

 can, in the hght of the accumulated evidence furnished by geology, 

 trace as far back as the Jurassic period. Such were, in the 

 European area, the Anglo-Gallic Basin, in which the secondary 

 strata of the south east of Britain and the north of France were 

 deposited ; the North Sea Basin (continuous with the former) 

 covering all of what is now North Germany and Denmark ; the 

 Aquitanian Basin of the South of France; the Helveto- Germanic 

 Basin, which, as a narrow sea extending over Northern Switzerland 

 and Southern Bavaria, connected the Pannonian Sea of the great 



