1474 Australian Natural History. 



scribed. Its outer margin is formed by a moderately steep beach, of 

 course calcareous sand mixed with larger fragments of coral and shells, 

 extending back for twenty yards or more, with a few scattered tufts of 

 grass and other herbage. The higher or vegetated portion of the 

 island is surrounded by a more or less continuous, low, wall-like bor- 

 der of coral rock, its faces much decomposed by the weather, and 

 hollowed out in a singular manner into innumerable intricate wind- 

 ing openings, some of which are large enough to admit a man's body. 

 This rock, which varies from a conglomerate to a coarse sandstone, is 

 in general soft and crumbles readily in the hand, but at one end of the 

 island, blocks of sufficient size and hardness to be used for building 

 purposes were obtained in abundance. This bed of sandstone is not 

 more than a few feet in thickness, and exhibits proof of its recent for- 

 mation, by containing shells and fragments of coral, specifically iden- 

 tical with living inhabitants of the reef, and occasionally eggs of tur- 

 tle,* apparently as if, while in situ in the loose sand of what was then 

 a mere sand-bank, some chemical agency had converted the whole in- 

 to a bed of stone. The centre of the island is considerably lower 

 than the margin, the highest part of which is about twenty-four feet 

 above high-water mark. Various attempts were made to procure 

 fresh water by digging, but without success. One pit, dug to a depth 

 of sixteen feet near the centre of the island, presented the following 

 succession of strata : — lstly, a layer, three inches thick, of rather fine 

 coral sandstone ; 2ndly, a deposit, nine inches in thickness, of moist 

 pulverulent black earth, resembling peat, but without any traces of 

 woody fibres ; 3rdly, and extending to the depth of thirteen feet from 

 the surface, are successive deposits, varying from coarse coral conglo- 

 merate and sandstone to unconcreted calcareous sand mixed with a few 

 small scattered fragments of coral and shells ; 4thly, a layer of masses 

 and large fragments of coral (of species now alive on the reef), bleached 

 and water- worn, loosely imbedded in coarse sand ; and here the boring 

 was discontinued in consequence of the ingress of salt water, which 

 ebbed and flowed with the tides. The greater portion of the centre of 

 the island affords a superstratum of rich black mould, well manured 

 with the dung of sea-fowl ; and in a small garden established there, 

 many culinary vegetables were found to thrive well. 



Owing to the slight range of tide at Raine's Islet, the reef is com- 

 pletely uncovered only at low-water spring-tides, the rise and fall 



* A specimen of this description from Ascension is exhibited in the Museum of 

 the Geological Society. 



