64 CORAL FORMATIONS. 
the depths of the lagoon. The growing reefs within lagoons, are in 
the condition of the ¢nner reefs about high islands. The corals grow 
but little disturbed by the waves, and the reef-rock often contains 
them in the position of growth. At Taputeouea (Tarawan Group), 
reefs very similar to those of the Feejees occur; they present the 
same large Astreas, 10 to 12 feet in diameter, which once were growing 
where they stand, but are now a part of the solid lifeless rock. 
Beach formations of coral sandrock are common on the coral islands, 
and they present the same features in every respect, as those described. 
They were observed among the Paumotus, on Raraka, Honden, 
Kawehe, and other islands. The stratified character is always distinct 
and the layers slope toward the water at the usual small angle, 
amounting to 5—7 degrees bordering the lagoon, and 7—8 degrees 
on the seashore side of the land. They often occupy a breadth of 30 to 
50 yards, appearing like a series of outcrops, yet not unfrequently they 
are mostly concealed by the sands of the beach.* The rock is a fine 
or coarse sandrock, or a coral pudding-stone, and consists of beach 
materials. Occasionally it is quite compact, and resembles common 
limestone, excepting in its white colour; but generally its sand origin 
is very apparent. 
The drift sandrock was not met with by the writer on any coral 
islands visited, and probably for the reason that opportunities were 
not favourable for a thorough exploration. It has been stated that 
the more exposed points towards the trades, especially the northeast 
and southwest, are commonly a little higher than other parts; and it 
is altogether probable that some of the sand-heaps, there formed, will 
prove on examination to afford examples of this variety of coral-rock. 
Such situations are exactly identical with those on Oahu, where they 
occur on so remarkable a scale. Mr. R. H. Schomburgh states that 
on the island of Anegada in the West Indies, the drift banks on the 
windward shores are forty feet in height. 
Although in these descriptions of atolls, we have dwelt on some 
points more at length than when describing barrier reefs, still it will 
be observed that the former have no essential peculiarities of structure 
apart from such as necessarily arise from the absence of high rocky 
* On the northern atolls of the Maldives, the beach sandrock is said to be quarried out 
in square blocks and used for building.—Journ. Geog. Soc. v. 400. 
t Journal of the Royal Geographical Society, 11. 152. Mr. Schomburgh describes the 
sandhills as 40 feet in height, and behind the first range, a second, and even a third. 
