ANNIVERSARY ADDRESS OF THE PRESIDENT. xliii 



precisely the same geological age ; for, while in South Wales and 

 Shropshire the Old Eed Sandstone directly succeeds and seems to 

 pass into the Ludlow beds, the Devonian rocks in the south-west 

 of England rest on Lower Silurian strata. Again, in our islands, 

 not only have we few or no terms of comparison between them 

 derivable from fossils*, but also their lithological characters are 

 remarkably distinctf . 



3rd. In the opinion of several geologists of note, our Old Eed 

 Sandstone proper ought to be broken up as a group and attached 

 partly to the Silurian and partly to the Carboniferous series. 



Under these circumstances, the remarks I venture to make must 

 be brief for want of definite data, which can only be obtained after 

 the areas have been carefully surveyed with the light that recent 

 discovery has thrown on the subject, and with the aid of new and 

 better topographical maps. 



These areas for the Old Eed Sandstone are England and Wales, 

 Scotland, and the south of Ireland, and Devon and Cornwall for the 

 Devonian rocks. 



In Shropshire and in neighbouring districts in South Wales 

 there is no sign of unconformity, nor any sudden break between the 

 Ludlow rocks and the Old Eed Sandstone. On the contrary, they 

 pass into each other, this passage being accompanied by a rapid but 

 not quite sudden disappearance of the uppermost Silurian fossils, in 

 a manner that suggests, not that there was any disturbance of the 

 strata, accompanied by unconformity, but rather that, by some lesser 

 but still broad change in physical geography, the succeeding con- 

 ditions were in some manner rendered adverse to a plentiful Silu- 

 rian life X- 



Again, when we rise to the top of the Old Eed Sandstone round 

 the Eorest of Dean and the greater part of the South Wales coal- 

 fields, we find that there is no sign of absolute unconformity be- 

 tween it and the Carboniferous series, although in Pembrokeshire 

 the limestone does creep across the Old Eed Sandstone in a manner 

 suggestive of overlap rather than of break and unconformity. If then 

 there be perfect conformity, through the intervening Old Eed Sand- 

 stone, between the Upper Silurian and Carboniferous Eocks, how did 

 it happen that the life of the two periods was so perfectly distinct ? 



1st. The old reply would have been that the Silurian life was 

 destroyed at the commencement of the Old Eed Sandstone epoch, 

 and that bye-and-bye, above the same area, the Carboniferous epoch 

 was ushered in by a special and completely new creation. Eut the 

 idea that special faunas were created and annihilated periodically 

 en masse has so long ceased to be the creed of most English geolo- 



* In Eussia, however, Devonian fossils and Old Eed Sandstone Fishes are said, 

 by Sir E. I. Murchison, to occur in the same bed. 



t In North America the Old Eed Sandstone of the Catskill Mountains lies 

 above the Devonian rocks ; but perhaps this only represents our Upper Plant- 

 bearing Old Red Sandstone. 



| See Sir R. I, Murchison's ' Siluria,' and Sir H. De la Beche on the " Forma- 

 tion of the Rocks in South Wales," &c, Memoirs of the Geological Survey, 

 vol. i. p, 51, 



d2 



