Sect. I. KEELING ATOLL. 11 



fathoms, the "bottom is exceedingly rugged and seems 

 formed of great masses of living coral, similar to 

 those on the margin. The arming of the lead here 

 invariably came up quite clean, but deeply indented, 

 and chains and anchors which were lowered, in the 

 hopes of tearing up the coral, were broken. Many 

 small fragments, however, of Millepora alcicomis 

 were brought up ; and on the arming from an eight- 

 fathom cast, there was a perfect impression of an 

 Astrsea, apparently alive. I examined the rolled 

 fragments cast on the beach during gales, in order fur- 

 ther to ascertain what corals grew outside the reef. 

 The fragments consisted of many kinds, of which the 

 Porites already mentioned and a Madrepora, apparently 

 the M. corymbosa, were the most abundant. As I 

 searched in vain in the hollows on the reef and in the 

 lagoon, for a living specimen of this Madrepore, I con- 

 clude that it is confined to a zone outside, and beneath 

 the surface, where it must be very abundant. Frag- 

 ments of the Millepora alcicomis and of an Astrsea 

 were also numerous ; the former is found, but not in 

 proportionate numbers, in the hollows on the reef; but 

 the Astrsea I did not see living. Hence we may infer, 

 that these are the kinds of coral which form the rugged 

 sloping surface (represented in the wood-cut by an 

 uneven line) round and beneath the external margin. 

 Between 12 and 20 fathoms the arming came up an 

 equal number of times smoothed with sand, and in- 

 dented with coral : an anchor and lead were lost at the 

 respective depths of 13 and 16 fathoms. Out of 



