Ixviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



more ancient rocks. From the mention made of the accumulations 

 emerging on the north-west, from beneath the trappean groups of 

 Snowdon and the more ancient beds of Anglesea, it will also have 

 been seen that there had not improbably been a still more ancient 

 movement of rocks in the North "Welsh area. Taking that area, we 

 would appear to have had many important movements of rocks in it. 

 First the old micaceous and chloritic slates of Anglesea, apparently 

 moved, (the evidence is not yet complete, though the probabilities 

 are considerable,) prior to the Bangor conglomerates and sandstones. 

 After which, whatever minor disturbances there may have been 

 during the period when igneous agency was so common, and the 

 trappean group was accumulated, no marked and great movement is 

 apparent until the date of the Bala beds. We then find the Caradoc 

 sandstone series reposing upon the disturbed and older beds. All 

 the deposits of the Wenlock and Ludlow accumulations continued 

 tranquilly, making all allowance for minor movements. 



The Wenlock and Ludlow series then became included in the great 

 movement which took place anterior to the deposit of the old red 

 sandstone and mountain limestone. In Flintshire, Denbighshire and 

 Caernarvonshire, we see these rocks overlapping disturbed beds from 

 the Ludlow rocks to the Anglesea micaceous and chloritic slates in- 

 clusive. The region was again disturbed after the deposit of the coal- 

 measures, and the new red sandstone series was deposited upon the 

 uplifted, bent, or contorted beds, as the case might happen to be, of 

 all the first-formed rocks. The new red sandstone itself was not 

 destined to remain quiet, and taking in the adjoining district- of 

 Cheshire, we find it also bent and broken, anterior to the drift, in- 

 cluding large boulders, too often spread over the rocks beneath to be 

 pleasing to the geologist. 



When we contemplate the many strange twists and complication of 

 fractures which must exist in the rocks of such an area, particularly 

 among the older accumulations, those consequently the longest ex- 

 posed to these various movements and breaks, there is enough to 

 point out how much caution is needed in our explanations of minor 

 portions of such an area, particularly when we reflect upon the com- 

 plicated arrangements produced by denudations at different times in 

 parts of the general mass, as at various periods it became elevated, so 

 that breaker action and atmospheric influence wrought out coasts 

 and all the modifications of dry land — mountains, hills, valleys and 

 plains ; or depressed in various ways beneath the sea, it became coated 

 with the detritus derived from portions of the still dry land. 



While lately in this country. Professor Henry Rogers brought 

 before the Society a comparison of the structural features of the Ap- 

 palachians of the United States with those of the Alps and other 

 disturbed districts of Europe. He divided his communication into facts 

 in connexion with flexures and fractures of the rocks composing the 

 Appalachians, the Alps, the Jura, and the palaeozoic districts border- 

 ing the Bhine, and the manner in which he and his brother. Pro- 

 fessor W. B. Rogers, of Virginia, proposed to account for the pro- 

 duction of such flexures and fractures. 



