184 CORALS AND CORAL ISLANDS. 
Beach formations of coral sand-rock are common on the 
coral islands, and they present the same features in every re- 
spect as those described. They were observed among the Pau- 
motus, on Raraka, Honden, Kawehe, and other islands. The 
stratified character is always distinct, and the layers slope to- 
ward the water at the usual small angle, amounting to 5-7 
degrees bordering the lagoon, and 6—8 degrees on the seashore 
side of the land. Agassiz gives the same angle for the sea- 
ward slope of similar deposits at Key West. The rock is 
largely a fine odlite. They often occupy a breadth of thirty 
to fifty yards, appearing like a series of outcrops; yet they are 
frequently covered by the sands of the steep part of the beach. 
The rock is a fine or coarse sand-rock, or odlite, or coral 
pudding-stone, and consists of beach materials. Occasion- 
ally it is compact, and resembles common limestone, except- 
ing in its whiter color; but generally its sand origin is 
apparent. Deposits of sand and fragments of corals and 
shells cover the top of a reef-bank underneath what there 
is of soil; and they are horizontal instead of having the dip 
of the beach. 
In borings by Lieutenant Johnson, of the Wilkes Explor- 
ing Expedition, on Aratica or Carlshoff’s Island, in the Pau- 
motus, ten or eleven feet were passed through easily, and then 
there was a sudden transition from this softer rock (probably 
the beach sand-rock), to the solid reef-rock. 
The drift sand-rock was not met with by the author on any of 
the coral islands visited. The time for exploration on these 
islands allowed by the Expedition was too short for thorough 
work. It has been stated that the more exposed points toward 
the trades, especially the northeastern and southwestern, are 
commonly a little higher than other parts; and it is altogether 
probable that some of the sand heaps there formed will prove 
