﻿448 Horace B. Woodward — Notes on the Devonian Rocks. 



them to produce sketch-maps, and in most cases to grasp the main 

 geological features of the country when they could not attempt to 

 follow out all the local points of structure ; and when we remember 

 that they had to start as it were in a terra incognita, we may well 

 speak with admiration of the grand work that was achieved in field- 

 geology in the early part of this century. 



While the greater portion of England and Wales has now been 

 worked out in considerable detail, and its rocky structure repre- 

 sented upon the Geological Survey maps, our knowledge of the 

 Palseozoic country of West Somerset, Devon, and Cornwall, is almost 

 entirely confined to sketch-maps, showing the general grouping 

 of the strata ; the determination and correlation of minor sub- 

 divisions in the rocks, and the tracing out of their exact boundary- 

 lines, having been as yet attempted only in a few localities. 



Thus the geological picture sketched partly by Sedgwick and 

 Murchison and Godwin-Austen, remains for the most part very 

 much as it was when left by the master-hand of De la Beche. And 

 here it is only right to observe that the maps of this district, which 

 were those first published by the Geological Survey, were the work 

 of De la Beche as an amateur, assisted only by the voluntary contri- 

 butions of other private workers. Consequently the same attention 

 to minute accuracy with which he subsequently directed the labours 

 of his staff, could not possibly have been given to this early work, 

 which covered an extent of ground that no one man could have 

 thoroughly investigated in a lifetime. 



Another grand version has, however, been given to the geological 

 outline of this district, and by a man whose experience put him at 

 least on a par with any of his predecessors. A considerable modifi- 

 cation in the classification of the rocks, as maintained by the majority 

 of those who had previously studied the country, was proposed in 

 1863 and subsequent years by Jukes. And his observations, based 

 to a large extent upon an intimate knowledge of the Carboniferous 

 rocks and Old Red Sandstone in the south of Ireland, coupled with 

 some previous acquaintance with the district, and with the advantage 

 of the labours of those who had gone before him, gave to his 

 opinions and conclusions a foi'ce which belonged to no other writer 

 upon the subject. He attempted no more than others had done, but 

 he drew a different outline, and instead of regarding the whole of 

 the Devonian rocks as equivalent in time to the Old Red Sandstone, 

 he maintained that only the lower divisions of the group could be 

 classed with this formation, the slates and limestones representing 

 the lower portions of the Carboniferous system. 



It is needless to enter here into all the labyrinths of this con- 

 troversy, as the subject has been elsewhere reviewed on several 

 occasions during the past few years.' It is scarcely to be expected 

 that a settlement of the question can be gained until the whole of 

 the country has been thoroughly worked out, and the accumulated 

 observations of many observers have been carefully arranged and 

 digested. It may not, however, be altogether fruitless if, while 

 ' Quart. Journ. Science, Jan. 1873; Trans. Plymouth Inst., vol. v. p. 450. 



