218 FIELD GEOLOGY. 



area of their deposition, the beds must abut on the 

 flanks of such elevation. Also if such high ground 

 consists of the lower part of any series, the upper 

 members should also be found on either flank, with 

 their denuded edges covered by the newer formations. 

 Mr. Godwin-Austen has shown that if the rock under- 

 lying the Gault beneath London be, as it probably is, 

 Old Eed Sandstone, then the Coal-measures, the New 

 Eed Sandstone, &c., must occur on either flank of the 

 anticlinal that has brought it up to that position. That, 

 in fact, the ridge is part of an extension of the South 

 Wales anticlinal to that of Belgium, therefore the Coal- 

 measures must occur on either flank, and will probably 

 be found, as in those areas, at a moderate depth, unless 

 removed by an ancient denudation. 



The way in which geological knowledge and reasoning 

 may be turned to practical account is shown also in the 

 two following sections on Water-supply and Soils 

 selected from many subjects upon which their bearing 

 is of great importance. 



WATER-SUPPLY, &c. 



An improvement in the water-supply of a district is 

 one of the practical results that may be expected to 

 arise from the working out of its geological structure 

 that is, from the knowledge obtained of its rocks and of 

 their relation to each other. The phenomena of springs 

 and the sources of supply to artesian wells are so 

 entirely dependent on stratigraphical and physical 

 features that an acquaintance with their principles can 

 not fail to be of use to the student of " Field Geology." 



