Notices of Memoirs — The Geological Survey. 359 



found to be sufficient. One of these editions shows all the super- 

 ficial deposits, and only the parts of the underlying formations as 

 lie bare at the surface. The other edition presents the underlying 

 formations as these would appear if the superficial accumulations 

 could be stripped off. Each of these editions has its value for 

 special purposes. In all questions of sanitation, water supply, 

 agriculture, and building, it is obviously the "Drift" edition that 

 sliould be consulted, while, on the other hand, wliere the informa- 

 tion desired has reference to what lies deeper beneath the surface, 

 as in the sinking of deep wells and mines, it is the " Solid" edition 

 that will be most usually consulted. The difference between the 

 two is merely one of colouring, for they are printed from the same 

 copperplate, and as far as the engraving goes are exact duplicates. 



The total number of six-inch maps published by the Geological 

 Survey up to the present time is for England and Wales, 223 sheets ; 

 Scotland, 127 sheets; Ireland, 10 sheets. The number of one-inch 

 ■whole-sheets and quarter-sheets (Old Series) for the whole of 

 England and Wales amounts to 261 ; 238 of these are published 

 only as " solid " maps ; 95 are issued in two editions, " solid " and 

 "drift"; of 23 only the "drift" edition is published. Of maps on 

 the one-inch scale, belonging to the New Series, 15 sheets have been 

 published, 11 of which are issued in two editions with and without 

 drift. The number of sheets published of Scotland is 60, and of 

 Ireland 205. The whole of Ireland has been completed and pub- 

 lished. Every effort is now being made to complete at as early 

 a date as possible the survey of Scotland, but the extraordinary 

 complication of the geological structure of the Highlands, being 

 far greater than was ever anticipated, i-enders the progress less rapid 

 than was originally expected. 



The desirability of having a general geological map of the country 

 on a smaller scale than that of one-inch to a mile has long been 

 recognized. When the mapping of England was completed, ad- 

 vantage was taken of the existence of an index Ordnance Survey 

 map on the scale of four miles to an inch (a-o-a-fTo)- This map, 

 based on the old one-inch maps, had been laid aside ; incomplete 

 by the Ordnance Survey, but it was likely to be so useful for 

 geological purposes that at the request of the Director-General it 

 was finished at Southampton. The work of the Geological Survey 

 has been reduced upon this map, of which there are for England 

 and Wales 15 sheets. The whole of these sheets have now been 

 l)ublished in chrorao-lithography, and when mounted in one sheet 

 present at a glance a clear and vivid picture of the geological 

 structure of the whole country. The price of each sheet is 2s. Qd., 

 and the total cost of the map is £1 17s. 



The value of reduced index-maps for geological purposes was 

 recognized long ago by the preparation of a general map of Wales. 

 When the Geological Survey of the Principality was finished the 

 whole work was reduced to the scale of four miles to an inch and 

 engraved in six sheets, which include parts of the W^est of Euglaud. 

 This map has been on sale tor many years. 



