: *> 



OUTI.IM's OF l n 





raised bea< .irply-cut rock j)latt 



are strikingly conspicuous, those at 50 feet and ioot.it 



being specially well marked (Fig. 82). 



Surface Mounds. In many districts the field-geologist 

 meets with mounds, as to the origin of which he at first 

 may be puzzled, if indeed he ever comes to any satis- 

 factory conclusion regarding them. The first qiu 



FIG. 82. Rock terraces (Setrr) marking ancient shore lines on the south 

 the IslandofMi.il. 



he will ask is, Are they of human construction ? Having 

 satisfied himself that they are not, he may try to find 

 some other origin for them by examining their composi- 

 tion, where any available section of them can be found, and 

 the nature of the surrounding ground. Mounds close to 

 the level of a river must always be regarded with a pre- 

 liminary suspicion of being relics of a formation elsewhere 

 removed by the erosive action of the stream. Mounds 

 of sand and gravel scattered across a district may be due 

 either to the irregular denudation of a once continuous, 

 though perhaps unequal, covering of these loose materials. 

 or to shapes assumed at the time of deposition. In 

 the former case, we should expect to find that sections 

 of the mounds would show the present slopes to have 



