in the Solomon Islands. 461 
shore-reefs which fringe this island attain their greatest 
width on the weather or east side, where they receive the 
brunt of the trade-swell. On the lee side, however, around 
the shores of Selwyn Bay, corals thrive in considerable pro- 
fusion ; and here my soundings were taken. Out of fourteen 
casts in depths less than 25 fathoms and more than 5 fathoms, 
sand was only brought up on the arming on two occasions; 
whilst out of fifteen casts in depths beyond 25 fathoms and 
extending to 50 fathoms, there was only one instance, viz. 
a cast of 26 fathoms, in which sand or gravel was not found 
on the arming. On examining the results of the four lines 
of soundings which I took, I am inclined to place the limit 
of depth at which coral thrives in this bay at between 20 and 
25 fathoms. The branching Madrepores and corals of the 
genus Serdatopora appeared from the broken fragments 
brought up in the arming to have a vertical range extending 
through the whole zone of coral-growth; the Madrepores, 
however, apparently lived under more favourable conditions 
in the shallower water; whilst the Sertatopore* seemed 
to prefer the lower limits of the zone. This accords with 
Mr. Darwin’s experience on the leeward coast of Mauritius 
(‘Coral Reefs,’ 1842, p. 81). 
2. Port Mary, on the west side of Santa-Anna Island.— 
This small island, which les off the eastern extremity of 
St. Christoval, is an upraised coral-atoll, about 450 feet in 
height, and completely girt by shore-reefs which on the west 
side of the island almost enclose a large circular lagoon known 
as Port Mary. My soundings were taken off the outer edge 
of the reef enclosing this harbour. ‘They extended to depths 
of between 70 and 80 fathoms, and included sixty-three casts. 
The conclusions to be deduced from the indications given by 
the arming of the lead may be briefly stated. The most 
favourable conditions for the growth of coral existed in depths 
less than 12 fathoms. Down to 20 fathoms living coral 
flourished, but in less profusion. Beyond that depth sand 
and gravel were more frequently brought up on the arming, 
and a depth varying between 20 and 30 fathoms represented 
the lower limit of the coral-zone. From the absence of 
branching corals, no fragment of living coral was brought up 
during the soundings. In only one cast was I able to recog- 
nize the nature of the coral from the form of the impression, 
when, from a depth of 17 fathoms, the arming preserved the 
prints of the large cells of one of the Astreide. From ex- 
perimental observation I have found that in the majority of 
soundings the unavoidable swaying of the lead renders the 
* Probably a new species. 
