Doan CORALS AND CORAL ISLANDS. 
consequent to its deposition, may come to assume the degree 
of consolidation usually observed in beach-rock. On the 
south shore of the main island, near Spanish Rock, I ob- 
served strata perfectly continuous dipping toward the water, 
exceedingly hard at the margin of the water, but becoming 
considerably softer as they were traced upward and landward. 
Mr. Ebenezer Bell, who some years ago had charge of some 
works in progress on Boaz Island, informed me that he found 
that the reck, so soft as to crumble in one’s fingers, became 
quite hard on immersion for a week or a fortnight im sea- 
water. Some of the hardest rock which I observed in Ber- 
muda was shown by other characters to be unmistakably 
drift-rock. A more reliable distinction is found in the lami- 
nation, the beach-rock showing a general and uniform dip 
toward the water, while the drift-rock shows the high and 
extremely irregular dips which are characteristic of wind- 
blown sands. But not every section exhibits characters sufti- 
ciently marked to settle the nature of the rock, since the 
beach-structure admits of a considerable degree of irregu- 
larity in dip, while wind-blown sands in a long ridge or dune 
may have for long distances a gentle and nearly uniform dip. 
The indication furnished by the fossil contents of the rock is 
important. The beach-rock is often richly fossiliferous, con- 
taining shells and pieces of coral of considerable size. The 
drift-rock will, of course, ordinarily contain no relics of 
marine animals except fragments so small as to be blown 
by the wind. A high wind can, however, sweep along pieces 
of shell and coral larger than one would at first suppose. . 
“While the presence of marine fossils in a sand-rock Is 
an indication that it is a beach-rock, the drift-rock 1s quite 
apt to contain the shells of land snails. The presence of 
snail shells cannot, however, be regarded as a sure proof of 

