156 
The Work of the Geological Survey. 
The total number of 6-inch maps published by the Geological 
Survey up to the present time is for England and Wales, 217 sheets ; 
Scotland, 130 sheets ; Ireland, 10 sheets. The number of 1-inch 
whole-sheets and quarter-sheets published for England and Wales 
amounts to 258 ; 142 of these are as yet published only as “solid ” 
maps; 89 are issued in two editions, “solid” and “drift”; of 23 
only the “ drift ” edition is published. Four quarter-sheets of the 
map of England yet remain to be published, but will be issued this 
year. The number of sheets published of Scotland is 48, 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 com- 
plication of the geological structure of the Highlands, being far 
greater than was ever anticipated, renders the progress less rapid 
than could be wished. 
The desirability of having a general geological map of the country 
on a smaller scale than that of 1 inch to a mile has long been 
recognised. When the mapping of England was completed, 
advantage was taken of the existence of an index Ordnance Survey 
map on the scale of 4 miles to an inch. This map, based on the old 
1-inch maps, had been laid aside incomplete by the Ordnance 
Survey, but it was likely to be so useful for geological purposes that 
at my request it was finished at Southampton. The work of the 
Geological Survey is now being reduced upon this map, of which 
there are in England and Wales 15 sheets. Four of these sheets 
have now been published with the geology, embracing the east of 
Yorkshire and the southern counties from Essex to Torquay. Other 
sheets are in progress, and the whole map when completed will 
present at a glance a clear and vivid picture of the geological 
structure of the entire country. 
The value of reduced index-maps for geological purposes was 
recognised long ago by the preparation of a 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 West of England. This 
map has been on sale for many years. 
(b) Sections . — A geological map can for the most part express 
only what lies at the surface, though it may afford information, 
more or less definite, as to what lies below. To supplement the map 
it is needful to construct sections to show the arrangement of the 
rocks beneath the surface. A complete and detailed map should 
contain sufficient data to allow such sections to be plotted in outline, 
but these details can usually be filled in only from the notes of the 
sections examined in the course of the mapping. Two kinds of 
sections are prepared and published by the Geological Survey — 
vertical and horizontal. They are drawn to scale, and engraved and 
published in sheets measuring 3 feet by 2 feet. But, besides these, 
numerous measured and also diagram sections are inserted in the 
text of the printed Memoirs. 
