1892.] Cause* Which Influence Top<>graj>hic<i/ Changes. 3 



advent of the whites, the aboriginal tribes have become ex- 

 tinct, and the introduction of sheep and cattle, to the pa>turage 



shells ot a snail peculiar to these island* (Helix ayrctiana 

 ), the bleaching bones of the aborigines, and the vast ac- 

 lations of the refuse of their camps, together with the 

 rf dead trees and shrubs, whose places in the soil appear 

 ve been filled by concretionary columns of sandstone 

 stand erect, sometimes projecting from two to four feet 

 the present surface, like gravestones in a cemetery, 

 ng how the soil in which they grew has been blown 

 These again will be covered by sand dunes, which may 

 tally become solid rock and puzzle geologists of future 



