32 



FIELD GEOLOGY. 



it may be a generalisation can be based thereon, with a 

 reasonable faith in its soundness and truth. 



Symbols. Three sets of symbols are here appended,, 

 and may be found useful, but of course any other letters, 

 figures, or devices, would answer the same purpose. 

 Those in the first column (Greek letters) can be recom- 

 mended for simplicity and convenience, as the tail 

 possessed by each letter when prolonged, is serviceable 

 in marking the exact spot at which a section is visible. 



Limestone A L , D 



Sandstone. Sand 



Gault 



Chalk 



Thanet beds 



Eeading beds 



London clay 



Boulder clay 



Brickearth. Loam 



Gravel 



Clay 



Two or more symbols may be so arranged as to indi- 

 cate at a glance the relative position in which the beds 

 are seen in section, by a line between them indicating 

 the inclination (if any) of the divisional planes of strati- 

 fication or of a fault. Thus a section of gravel, over 

 Thanet beds faulted against chalk, would be shewn - r - 

 and a bed of Limestone resting on Sandstone, and dip- 

 ping in the same direction . (WhitaJcer.) 



The following table gives the symbols or signs en- 

 graved on the published maps of the Government Geo- 

 logical Survey, to indicate the occurrence at the points 



