1XXX PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [MayiQII. 



received the sediments that build up its formations from that con- 

 tinent. It has, on the other hand, grown in the main south-eastwards 

 since Palaeozoic times, from the more ancient Laurentian land-mass 

 on the west. What may have been the original extent, composition, 

 or outline, of this land-mass we do not and perhaps can never know 

 for certain ; but it seems to have begun to undergo denudation in 

 Torridonian times, and to have been gradually disintegrated until 

 a mere wreck in the north-west of our Islands is all that is now 

 left of it. Wave after wave of movement from the eastward has 

 broken against the old continent, or off its edge, shore-line after 

 shore-line has formed farther and farther eastwards : the present 

 great northern plain of Europe representing the deeper sea into 

 which the finer sediments were swept. Thus in Britain the 

 deeper-water and finer-grained sediments are the least common, and 

 the lithological facies of our formations is mostly coarse-grained, 

 shallow, shoreward, and even terrestrial. This it is which has 

 invested them with so much of exceptional interest, and has 

 stimulated among British Geologists the practice of reasoning in 

 the direction of palseogeography. 



Innumerable oscillations and even great orogenic movements have 

 occurred, varying the monotony of formational succession, but it 

 was long before the western land was completely broken down, the 

 newer features formed out of the relics of its earlier denudations 

 acting in a sense as groynes on which the destructive forces were 

 spent. The Caledonian movement first drew off the forces of 

 marine attack, denudation being mainly concentrated on the newly 

 formed and highly ridged mountains. Then followed the Pennine 

 and Armorican movements with corresponding effects, and, finally, 

 such minor elevations and dislocations as are due to the almost 

 spent force of the Alpine disturbance drove the forces of the attack 

 still farther to the east. 



(c) Movement and Infilling. 



While, when acting on rocks which have not been affected by 

 previous movements, each distinct crust-movement in Britain has 

 imposed its own definite direction or directions, in other cases the 

 direction of older movements has been taken up again in the newer 

 rocks. Thus the strikes of the Carboniferous rocks of the Pennine 

 and Armorican regions are those of the trend of the local axes 

 of elevation characteristic of those movements. But the strikes of 

 those caught in the Central Valley of Scotland, in the Vale of Clwyd, 



