of Edinburgh , Session 1885 — 86 . 
881 
would be more favourable conditions for the growth of coral. My 
soundings afford evidence that such is the disposition of the detritus 
on the outer slope of this reef. Living corals flourished on the 
upper part of the submarine slope down to the base of the declivity : 
here in depths of 15 to 20 fathoms (marked by a + in the section) 
sand and gravel had accumulated, and there was but little living 
Sections showing the Seaward Slopes of Reefs in the Solomon group. 
( Drawn on a true scale to the \0§-fathom line , inch— 100 
feet.) The crosses mark the bases of the declivities where the 
sand collects. 
Sea-level. 
Sea-level. 
Section 2. Reef of Onua Islet, Shortland Islands. 
Sea-level. 
coral. On carrying the soundings further seaward on the broad 
ledge beyond, I found that the sand and gravel began to disappear 
and that the armings in the greater proportion of the casts made in 
depths of from 23 to 40 fathoms showed the presence of living 
coral. This disposition of the detritus is readily to be explained. 
Sand and gravel, derived from the constant action of the rollers 
VOL. XIII. 3 M 
