Notices of Memoirs — The Oeological 8urvey. 317 



buildings are being constructed, whereby fresb light is obtained as 

 to the rocks below. Geological lines which were traced with the 

 imperfect evidence formerly available can thus be corrected, and 

 new lines which perhaps were not originally suspected can be 

 inserted. If this kind of obsoleteness overtakes geological maps 

 even where only superficial openings are concerned, still more does 

 it affect those which depict the structure of mineral-fields still 

 actively worked. The geological maps of Devon, Cornwall, and 

 South Wales, made some two generations ago by De la Beche 

 and his associates, were for their time admirable in conception 

 and excellent in execution. Nothing approaching to them in merit 

 had then been produced in any part of the" world. But the mineral 

 industry of the country has not been standing still all these years. 

 Enormous progress has been made in working the ores of the 

 western counties, and in developing the great South Wales Coalfield. 

 Yet most of the maps still remain as they were originally published, 

 though their revision is now in progress. 



It is absolutely necessary, if the value of the labour and expense 

 bestowed on the Geological Survey of the United Kingdom is not 

 to be impaired and lost, that the maps should be revised and 

 brought up to date as frequently as may be required. The necessity 

 for such revision has been pressed on the attention of Government 

 by influential memorials from various districts of the country; and, 

 hitherto, as far as the other requirements of the Survey permit, 

 these requests have been complied with. Thus, in consequence of 

 an urgent representation from the proprietors and lessees of the 

 coalfield of South Wales, and from others locally interested in the 

 development of that region, steps were taken a few years ago 

 to place there a staff of surveyors, and the revision of the ground 

 is actively advancing. Already three sheets of the new series of 

 Ordnance Maps of South Wales have been published, and one other 

 is now in the hands of the engraver. The inhabitants of Cornwall, 

 likewise, recently memorialized the Science and Art Department 

 to undertake a revision of the geological maps of that county ; and, 

 in response to their request, a beginning of the woi'k has been 

 started. The people of North Staffordshire, anxious for the proper 

 development of their coalfield, made a representation that the time 

 had come when a revision of the maps of their district was 

 necessary, and this task has been undertaken by the Geological 

 Survey. Other districts have sent in similar petitions for re-survey 

 with which it has been hitherto impossible to comply, owing to 

 the smallness of the staff. All these tracts of country were 

 originally surveyed on the old and imperfect sheets of the one-inch 

 Ordnance map. But the revisions are conducted on the modern 

 six-inch scale, and the reductions are made upon the new series of 

 one-inch sheets. There can be no doubt that all the other mineral- 

 fields of the country require similar treatment. 



The revision of that large part of England and Wales where the 

 superficial deposits were not originally mapped, in order to complete 

 the Drift survey of the whole country, is carried on upon the six-inch 



