APPENDIX. 221 



Abrolhos (lat. 2 8° S. on west coast) have lately been 

 surveyed by Capt Wickham (as described in Naut. Mag., 

 1 84 1, p. 511): they lie on the edge of a steeply shelving 

 bank, which extends about 30 miles seaward, along the 

 whole line of coast. The two southern reefs, or islands, 

 enclose a lagoon-like space of water, varying in depth from 

 5 to 15 fathoms, and in one spot with 23 fathoms. The 

 greater part of the island has been formed on their inland 

 sides, by the accumulation of fragments of coral ; the sea- 

 ward face consisting of nearly bare ledges of rock. Some 

 of the specimens, brought home by Capt. Wickham, con- 

 tained fragments of marine shells, but others did not ; and 

 these closely resembled a formation at King George's 

 Sound, principally due to the action of the wind on 

 calcareous dust, which I shall describe in a forthcoming 

 part. From the extreme irregularity of these reefs with 

 their lagoons, and from their position on a bank, the usual 

 depth of which is only 30 fathoms, I have not ventured 

 to class them with atolls, and hence have left them un- 

 coloured. — Rowley Shoals. These lie some way from the 

 N.W. coast of Australia : according to Capt. King (Narra- 

 tive of Survey, vol. i. p. 60), they are of coral-formation. 

 They rise abruptly from the sea, and Capt. King had no 

 bottom with 170 fathoms close to them. Three of them 

 are crescent-shaped; they are mentioned by Mr. Lyell, on 

 the authority of Capt. King, with reference to the direction 

 of their open sides. " A third oval reef of the same group 

 is entirely submerged " (Principles of Geo log., book iii. 

 chap, xviii.); coloured blue. — Scoffs Reefs, lying north of 

 Rowley Shoals, are briefly described by Capt. Wickham 

 (Naut. Mag., 1841, p. 440) : they appear to be of great 

 size, of a circular form, and " with smooth water within, 

 forming probably a lagoon of great extent," There is a break 



