OBJECTIONS TO THE THEORY OF SUBSIDENCE. 293 
The basement, according to Mr. Murray, may be a vol- 
-eanic cone or a submerged mountain-peak at the proper level; 
and if too low, it may be raised up to it by pelagic life-relics ; 
if too high, like the “emerged volcanic mountains situated in 
the ocean basins,’ it may be razed by abrading agencies to 
the water-level and finally lowered by the waves and cur- 
rents to the needed depth. It is true that the basement for 
growing corals may be anything that has the proper depth. 
But this shaving off of a mountain and carrying the erosion 
to a few fathoms below the sea without a change of level is 
beyond physical possibility. Land-waters cut out valleys or 
gorges, and indefinite time would be required for the final lev- 
elling. Waves are too shallow in their action, the rising, tidal 
waters too protective, and the rocks under a cover of water too 
resisting, for the marine part of the degradation. 
But this making of atolls and barrier reefs on banks sub- 
merged at the right distance without submergence, encoun- 
ters a fatal difficulty wherever there are deep lagoons and 
deep channels, which difficulty has not been overcome though 
various methods have been suggested. 
4. Lagoon basins and channels made largely by abrading 
and solvent action. It is urged, in agreement with Darwin, 
that the outer portions of reefs increase faster than the inner, 
owing to the purer water about them and the more abundant 
life for food; that the inner parts are not only at a disadvan- 
tage in these respects, but suffer also from coral debris thrown 
over them. Some writers have considered this of itself suffi- 
cient, saying that the edges of the bank will thus reach the 
surface, while the interior makes little progress; and so 
comes the lagoon basin. But the above authors add to the 
causes of unequal growth mentioned by Darwin the solvent 
and abrading action of the waters. 
