302 Hicks on the ^Reef=(Builders. 
simply a mass of debris^ of which the very coarse and angular 
fragments form the steep slope just below the zone of living 
corals, and the finer sand forms the gentle sloj^e down to the 
seaward base of the reef. Dana corroborates the facts, and re- 
marks that they "sustain instead of correcting those announced 
by earlier observers. Beecher and Darwin make the mean slope 
about 45°, and my report says 40° to 50°."^ But he main- 
tains that the talus of large blocks from 40 to 100 fathoms is 
"positive proof of much subsidence" because it is "far below the 
limit of forcible wave action." This is not conclusive. These 
blocks have descended by falling or sliding down the sea-ward 
face of the reef — how far may be doubtful, possibly from any 
part of the slope a b. If they have descended at all their present 
depth below the line of any wave action forcible enough to 
break them off does not ap^Dear to furnish the positive proof of 
'■'■much subsidence'''' which is claimed for them. Dana has him- 
self stated that when subsidence is not in progress "the coral 
and shell material produced that is not lost by currents, serves, 
to widen the reef and to steepen in consequence of the widen- 
ing, the upper part of the submarine slopes." The tendency 
of this action would be to broaden the life zone a b, until 
it became very steep or even overhanging at b, like the 
"coral heads" described by Whipple and Hartt.* In that case 
no very forcible wave action would be required to dislodge 
the huge blocks which form the talus b c. Tahiti has not been 
subsiding, but rather rising, in recent times, as shown by the 
breadth of shore plain underlaid with coral somewhat above 
sea level. If we grant that the talus of large blocks does not 
prove subsidence, then there is no evidence of it known to me^ 
except that the Darwinian theory demands it. 
Plainly the Tahitian reefs may have been formed without 
subsidence. The seaward slope is not too steep for the pos- 
sibilities of debris-accumulation in deep and, therefore, quiet 
water. The part composed of coral sand is even less steep 
than slopes of the same material observed by Agassiz at the 
Florida Keys. In the steepest part the fragments are coarse 
and angular, and the cementing effect of the calcareous matter 
'Am. Journal of Science, Sept. 1885, p. 175. 
* See Corals and Coral Islands. Dana pp. 139, 141. 
