214 



OUTLINES OF FIELD-GEOLOGY PART u 



of diagrammatic way the order of ilic formations, heedless 

 of the utterly unnatural shape of his hill. The other 

 section (B) shows the true outline of the ground, on t he- 

 scale of six inches to a mile, vertical and horizontal, \\ith 

 the relative position of the rocks correctly inserted. 



N.FLOET2 TRAP 



SANDSTONE 



FIG. 86. Illustrations of geological section drawing. 



A further and familiar illustration of the effects of this 

 neglect of the true proportions of the ground is offered 

 to us by the case of the " London Basin." I presume 

 most readers, when they meet with that phrase, think of 

 a deep bowl-shaped hollow filled with clay and surrounded 

 by a rim of chalk hills, and they probably recall one of 

 the sections in popular manuals and text-books by which 

 this impression was originally given to them. If, how- 



