174 TRANSACTIONS OF SECTION C. 



greatly improved in recent years. In particular, the introduction of a longi- 

 tudinal section on each map and the substitution of the vertical section drawn 

 to scale for the old colour index must greatly assist those into whose hands 

 it comes in obtaining a correct view of the succession of the strata and the 

 structure of the country. Some of the maps are, it is true, so crowded with 

 information— topographical and geological— that it is frequently difficult, even 

 for the trained geologist, to read them without a lens. This is largely duo 

 to the fact that they are printed over the ordinary topographical maps_ in 

 which there is a great amount of detail that is not required in geological 

 maps. In India the Trigonometrical Survey are always ready to supply, as 

 a basis for special maps, copies of their own maps printed off plates from 

 which a portion of the topographical features have been erased. 



The best remedy, however, would be to extend the publication of the maps 

 on a scale of 6 inches to a mile (1 : 10,560). For many years all geological 

 survey work has been, in the first place, carried out on maps of this scale, 

 but they have not been published except in coal-mining areas. There the 

 geological boundaries are printed, but the colouring is added by hand, which 

 makes the maps comparatively expensive. In other localities manuscript 

 copies of the geological line.s and colouring on the Ordnance Survey maps can be 

 obtained at the cost of production, which is necessarily considerable. 



There is, I believe, a wide sphere of usefulness for cheap colour-printed 

 6-inch geological maps, especially in the case of agricultural and building land, 

 for which the 6-inch Ordnance maps are already in demand. They afford ample 

 room for geological information, and, accompanied by longitudinal sections on 

 the same scale without vertical exaggeration, their significance would be more 

 readily apprehended than that of maps on a smaller scale. It may be noted 

 that this is the favourite scale employed by those engaged in independent 

 geological research for their field work, and, when the area is not too great, 

 for the publication of their results. 



It would be of gTeat advantage if there were a uniform usage by which the 

 position in the stratigraphical series of rock outcrops were indicated by colour 

 and their lithological character by stippling (in black or white or colour) 

 following the ordinarily accepted conventions. This course has been pursued 

 by Professor Watts in the geological map prepared by him to illustrate his 

 'Geography of Shropshire.' This increases the practical value of the map 

 for many purposes, but is only possible when it is not overburdened with 

 topogi-aphical detail. 



Some explanation, apart from the maps themselves, is however needed if 

 they are to be rendered, as they should be, intelligible to the general public. 

 The official memoirs which deal with the same areas as the maps do not afford 

 a solution of the difficulty. Excellent as they are from the technical stand- 

 point and full of valuable' information, they convey little to the man who has 

 not already a considerable acquaintance with the subject. What is needed is 

 a short explanatory pamphlet for each map, presuming no previous geological 

 knowledge, describing briefly and in simple popular language the meaning of 

 the boundary lines and symbols employed, and the nature and compoeition of 

 the different sedimentary or igneous rocks disclosed at the surface or known to 

 exist below it in the area comprised in the map. A brief account of the fossils 

 and minerals visible without the aid of a microscope should also be included. 

 The probable mode of formation of the rocks and their relation to one another 

 and the subsequent changes they have undergone should be discussed, and at 

 the same time their influence on the agriculture value of the land and its 

 suitability for building sites, as well as on the distribution and level of under- 

 ground water, should be pointed out. Some account too should be given of the 

 economic mineral products and their applications. 



These pamphlets should be illustrated by simple geological sections, views 

 of local quarries and cliffs showing the relntive positions of the different rocks, 

 figures of the commoner fossils at each horizon, and, where they would be 

 useful, drawings of the forms assumed by the minerals. Each pamphlet would 

 be complete in itself. This would involve a considerable amount of repetition, 

 but it must be remembered that different pamphlets would have as a rule 

 different readers. An alternative plan would be to follow the example of the 

 United States Geological Survey and reprint the same brief resume of geological 



