OUTLINES OF FIELD-GEOLOGY 



PART I 



inferred lhat they indicate m I of the land. The 



terrace or raised-beach, as it is called, is then said to 

 mark an upheaval of the coast to the extent of 100 feet. 

 Barnacles adhering to rocks, and living shells which have 

 perforated them (Fig. 19) furnish similar proof of a 

 change of level and probably, in the great majority of 



r . 





FIG. ao. Section of a buried land-surface (De la Beche). et, rocks underneath ; 

 dd, old vegetable soil ; aa, stumps of trees still erect in position of growth ; 

 l>, prostrate tree-trunk ; cc, horns of oxen and deer. The whole buried under 

 silt and modern soil./ 



cases, point to an actual elevation of the land. On the 

 other hand, a submergence may be demonstrated to have 

 taken place when a terrestrial surface, with its tree-stumps 

 in situ y old soil and sylvan leaf mould, is found below 

 high-water mark. The trees must have grown above the 

 limit of ordinary tidal action, so that the amount of 

 depression must always more or less exceed the vertical 

 distance between the line of the submerged trees and 

 the upper edge of the beach. Here again the same 

 difference of opinion exists as to whether the apparent 

 subsidence has been caused by an actual sinking of the 

 land or a rise of the sea. Both causes no doubt from 



