OBJECTIONS TO THE THEORY OF SUBSIDENCE. 283 
rock and finer material occurs at depths between 240 and 
600 feet; (3) that, a mile out, the bottom has the slope 
nearly of the adjoining land, and in this part is covered with 
the remains of pelagic life. i 
- From the second of these facts, —the great accumulation 
of coral blocks below a level of 240 feet, — Mr. Murray draws 
the conclusion that, in the making of fringing, barrier, and 
atoll reefs, the widening goes forward (a) by making first 
upon the submarine slopes outside of the growing reef a 
pile of coral debris up to the lower limit of living reef-corals ; 
and then (6) by building outward upon this accumulation as 
a basement. 
b. But these observations fail to prove that an accumu- 
lation of coral blocks over the slopes below the reef-coral 
limit is a result of the process appealed to. In truth they 
set aside his conclusion by making the fact of a subsidence 
unquestionable. 
That belt of coarse debris — including “ masses 20 to 30 
feet” long — was found over the steeply sloping bottom at 
below the limit of forcible wave-action. They are depths 
where the waters, however disturbed above by storms, have 
no rending and lifting power, even when the bottom is grad- 
ually shelving; depths, in this special case, against a slope 
which for 100 yards is 75° in its upper part, and in no part 
under 45°, the vertical fall being 360 feet in the 100 yards. 
Strokes against the reef-rock thus submerged, and under such 
conditions, would be extremely feeble. Waves advancing up 
a coast, whether storm-driven waves or earthquake waves, 
do little rock-rending below the depth to which they can bare 
the bottom for a broadside plunge against the obstacle before 
them, although the velocity gives them transporting power 
/ . 
depths between 240 and 600 feet. These depths are far ~ 
