106 " Present State of the Devonian Question. [January, 



up the whole of the interval between the top of the old red 

 sandstone and the base of the coal-measures. Here he con- 

 tended was the clue to determine the structure of North 

 Devon ; the order of sequence appeared to him the same in 

 both localities, so that the so-called Devonian rocks were 

 really the lower portion of the carboniferous system, resting, 

 as in Ireland, upon a base of the old red sandstone.* 



In 1867 Mr. Jukes published a small map, which more 

 clearly expressed his ideas. The true old red sandstone he 

 considered to occur at the North Foreland, Minehead, and 

 Croydon Hill, also at the north-western end of the Quantock 

 Hills ; then succeeded the carboniferous slate at Lynton, 

 Combe-Martin, Ilfracombe, Mortehoe, and the Brendon 

 Hills ; while stretching from Pickwell Down to Haddon 

 Down, Mr. Jukes identified another band of old red sand- 

 stone, to account for which he considered that a great fault, 

 with a downthrow to the north, occurred along this line 

 and repeated the beds to the south, — the carboniferous slate 

 coming conformably over this band of old red sandstone, 

 and then again passing gradually into the culm-measures 

 above. 



Mr. Jukes's views met with great opposition at the time, 

 but as few, if any, of his opponents had a personal know- 

 ledge of the geology of the South of Ireland, they could not 

 perhaps fully realise all the facls which guided him in his 

 inferences. 



Mr. Etheridge,t however, took up the question in great 

 detail, and though perhaps he laid greatest stress upon the 

 palseontological evidence, he yet disputed the conclusions 

 of Mr. Jukes on physical and stratigraphical grounds, and 

 maintained that there was no evidence of any fault, as the 

 succession of the strata and the groups of associated fossils 

 from the North Foreland to Barnstaple was continuous and 

 natural. The area he considered to be occupied by three 

 well-defined groups — the Upper, Middle, and Low 7 er De- 

 vonian, chronologically equivalent to the whole of the old 

 red sandstone, but deposited under different mineral and life 

 conditions, and in a different geographical area. The fossil 

 evidence, in his opinion, was against any repetition of the 

 beds, and nowhere justified the proposition that the Devonian 

 beds were synchronous with the carboniferous. In discus- 

 sing this question, however, Mr. Jukes argued that the 

 difference between the fossils from different parts of the so- 

 called Devonian rocks did not differ more markedly from 



* Vide Jukes and Geikie, Manual of Geology, 1872, p. 762. 

 f Quart. Journ. Geol. Soc, vol. xxiii., p. 56S. 



