OLD RED SANDSTONE AND DEVONIAN. II5 



of the Devonian rocks are more complex. The Upper 

 Devonian strata in North Devon shade off into the Lower 

 Carboniferous rocks ; but in South Devon, owing to the many 

 disturbances in the rocks, there is no evidence of this passage. 

 Indeed, there is evidence to show that the Culm Measures 

 overlap the Upper Devonian strata, and rest in places directly 

 on the Middle Devonian Limestone. It appears, however, 

 highly probable that the lowermost Devonian rocks represent 

 the passage-beds between the Lower Old Red Sandstone and 

 Silurian, if they do not actually include rocks of undoubtedly 

 Silurian age. The evidence on which these remarks are 

 based will be noted further on, but it may be stated now 

 that the following groupmg seems the most in accordance 

 with the ascertained facts :^— 



Devonshire and Cornwall. South Wales, etc. 



jT -p. . ( Lower Carboniferous and 



^^ ■ ( Upper Old Red Sandstone. 



Middle Devonian. (Break.) 



T -n> • ( Lower Old Red Sandstone, Passage Beds, 



-Lower L)evonian. I , . ci ■ 



( and uppermost Silurian. 



The conclusion to be drawn is that in the Devonshire area 

 there is a conformable sequence of strata, and that the Middle 

 Devonian (marine) beds bridge over the interval between the 

 Upper and Lower Old Red Sandstone in South Wales, etc. 



Prof. Hull has, indeed, suggested that the Cornstone Group 

 (Lower Old Red Sandstone) of South Wales, etc., represented not 

 merely the Lower Devonian, but also the Middle Devonian, thus 

 making the series complete in that area. And he maintained that 

 the beds were formed in an estuary, quoting the opinion of Prof. 

 Dewalque that the Cornstone beds might be marine." This view, 

 of course, is more or less conjectural, and for the present we may 

 be content with linking the English and Welsh Lower Old Red 

 Sandstone with the Silurian rocks, and the Upper Old Red Sand- 

 stone with the Carboniferous. The same view was suggested as 

 early as 1839 by Thomas Weaver.^ Hence now-a-days, as in the 

 time of Hugh Miller (1841), the Old Red Sandstone has come 

 to be regarded "as a sort of debateable tract, entitled to no 

 independent status," or as a " common which should be divided 

 as proprietors used to divide commons in Scotland half a century 

 ago, by giving a portion to each of the bordering territories."* 



The grouping now adopted must be regarded as provisional. The 



^ See also R. A. C. Godwin-Austen, Brit. Assoc. 1870. 



^ Q. J. xxxviii. 200, 205. See also Q. J. xxxvi. 259-273, and G. Mag. 1881, 

 p. 508. 



3 Phil. Mag. 1839, p. 118. 



* The Old Red Sandstone, p. 19. 



