U»: 



Ji*k. 



'"•^ 







i 



m 



- - 1 



Soil 



1 1 



-a : i 



^ h 



Ht 



^tii, 



.^ i< 



^ 



» 



W 





thick 



£ 



tl..: 



2 



-^) of 





ri from the 



m 



f^A f 



llowiiij 



ford islandi o; 



perf 'tki 

 s ]im inequality 



ii being 





- 1 



ire 



from 



re 



It I' o» 



-. tber may l« 



jaip the la?«"^ 

 •-J as at ^^ 



. . fl-be!'^" 



gels ^^'^■'!, # 



Cii. XLIX.] 



ORIGIX OF THEIR FORM. 



rv( 



•o 'J V 



' 111 wliat manner is tliis singular conformation to be ac- 

 counted for ? The action of the waves is seen to be the 



ca 



ward 



some re 

 : masses 



w 



thrown up by the breakers ; but there is a variety of cases 

 here this cause alone is inadequate to solve the problem ; 

 for reefs submerged at considerable depths, where the move- 

 ments of the sea cannot exert much power, have, neverthe- 

 less, the same conformation, the leeward being much lower 



than the windward side.^ 



' I am informed by Captain King, that, on examining the 

 reefs called Eowley Shoals, which lie off the north-west 

 coast of Australia, where the east and west monsoons prevail 

 alternately, he found the open side of one crescent-shaped 

 reef, the Imperieuse, turned to the east, and of another, the 

 Mermaid, turned to the west ; while a third oval reef, of the 

 same group, was entirely submerged. This want of con- 

 formity is exactly what we should expect, where the winds 

 vary periodically. 



seems impo 



uniformity 



of submarine volcanos, on the summits of which we may 

 suppose the coral reefs to grow; for although it is very 



down 



cannot imagine any cause that should breach them all in the 

 same direction. But the difficulty will, perhaps, be removed, 

 if we call in another part of the volcanic agency— subsidence 

 by earthquakes. Suppose the windward barrier to have been 



r 



mechanical 



of 2 or 3 yards above the wall on the leeward side, and 

 then the whole island to sink down a few fathoms, the ap- 

 pearances described would then be presented by the sub- 

 merged reef. A repetition of such operations, by the alter- 



mass 



mi2" 



efilux 



of tlie tide has probably a strong tendency to check the 



* Voyage to the Pacific, &c., p. 189. 



*' 



