A Monoo;raph of Marcus Island. 



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The condition existing at 

 the north point (Fig. 5) was 

 such as to leave no doubt in 

 my mind that the reef here 

 exposed had been formed and 

 elevated at a period after the 

 first described beach had been 

 raised above the sea. Thus 

 are we able to account for two 

 successive elevations. The 

 consequent change in the 

 topograph}- is perhaps best 

 observed in the step or bench- 

 like beaches, referred to above 

 and delineated in cross sec- 

 tion drawings A to B ( Fig. 6 ) , 

 along the east coast. The 

 uniformit}' of these beaches, 

 taken in conneclion with the 

 character of the material com- 

 posing them, can only be ac- 

 counted for by acceptance of 

 a theory admitting of two or 

 more periods of elevations in 

 the island's history. It was 

 interesting to observe that 

 the northern and eastern por- 

 tions of the laud were most 

 generally composed of the 

 coarsest materials. No doubt 

 this was due to the exposure 

 of that side to the most ex- 

 treme action of wind and sea, 

 and the correspondingly nar- 

 row reef on that side ; for, 

 other conditions being equal, 

 the relative size of the ma- 

 terials composing a beach is 

 direclly in proportion to the 

 width of the surrounding reef. 

 By consulting the map it wil} 



