ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixv 



examples occur near Tremadoc, at the north-eastern termination of 

 the Merioneth anticKnal elevation, and near the northern extremity 

 of Bala Lake. 



I do not wish on this occasion to intrude upon you my own 

 theoretical views, but I may be allowed, perhaps, to observe, that 

 the phsenomena now described are strictly in accordance with the 

 theory of elevation which I have so frequently advocated, and with 

 the hypothesis that the disturbances and dislocations of the strata 

 above described are of contemporaneous origin. The parallelism of 

 the southern portions of the two great longitudinal faults which I 

 have described as embracing the Denbighshire basin on opposite sides, 

 and their continuity, afford strong proof that they are of the same 

 age throughout their whole lengths ; and that their divergency of 50° 

 or 60° from each other in their more northern portions is due to the 

 particular conditions under which the elevating forces acted, and not 

 to the circumstance of these latter portions being referable to viddely 

 different geological epochs, while their southern portions are to be 

 referred to the same epoch. 



The structure of the district on the north, the east, and the south 

 of the Berwyns is very complicated. On the north the beds dip, 

 with numerous dislocations and irregular disturbances, under the 

 Upper Silurians of Denbighshire, as already stated. On the south 

 they dip in a similar manner under the Upper Silurians contained in 

 a geological depression similar to that of Denbighshire, but smaller 

 in extent, and extending in an east and west direction from Welch- 

 pool to Mallwyd, a place nearly on the same meridian as the southern 

 end of Bala Lake. Sections parallel to the Berwyns, N.E. and S.W., 

 and to the east of those mountains, exhibit an anticlinal line, the 

 direction of which is somewhat N. of W. and S. of E., and therefore 

 nearly perpendicular to the Berwyns anticlinal. The northern and 

 southern extremities of such sections exhibit what is considered as 

 Caradoc Sandstone, and has been coloiu'ed as such on the Ordnance 

 Map. The beds more immediately on each side of the nearly east and 

 west anticlinal are those which rise from beneath the north and south 

 synclinal trough containing the mass of the Berwyns, and must 

 therefore consist of beds the equivalents of others existing to the 

 west of the Berwyns anticlinal. 



If we again recur to the surface of our hypothetical stratum, we 

 now observe that the great geological valley on the eastern side of the 

 great fault of Dolgelly and Bala not only descends into the deep 

 depression of Denbighshire on the north, but also into a similar one 

 on the south between the Severn at Welchpool and the Dyffi at 

 Mallwyd. To the east of Bala Lake, in the central portion of the 

 space intermediate to these two great geological depressions, our 

 hypothetical stratum rises again under the Berwyns to form the 

 east and west ridge running from that range to the borders of 

 Shropshire, where these older beds become hidden beneath superin- 

 cumbent and unconformable strata. On the S.W. both the great 

 geological valleys east of the Merioneth anticlinal are continued into 

 VOL,. IX. e 



