184 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
on the east shore of a continent than on the west shore,’ and as Murray 
points out, this favors the growth of corals along the eastern shores of 
the continents. It must also favor the yielding up of carbon dioxide, 
The conclusion seems warranted from these facts that the warming of 
the sea-water of the South Atlantic equatorial current that sets against 
the northeast coast of Brazil is capable of supplying all the carbon 
dioxide necessary for the hardening of the stone reefs, 
Is the process wniversal ?— But if the hardening of these beaches is 
produced by the sea-water alone, why is it that the process is not a uni- 
versal one, at least in the tropics? 
From what has gone before, it might appear that it was simply a mat- 
ter of carbon dioxide, either of volcanic origin or derived from cold sea- 
waters by warming them, in which case we might expect such beaches 
in almost any part of the world. 
Now the relations of ocean currents and temperatures to carbonic acid 
are not new, but must have existed for a long time. If the sands of 
tropical shores have been consolidated by the aid of carbonic acid brought 
in by ocean currents, this process of consolidation must have been going 
on ever since the present currents were established, and it must be 
going on to-day. Confining ourselves to the Brazilian coast, we should 
expect to find, therefore, not a single or double line of stone reefs, but a 
continuous series of hardened beaches overlapping each other, wherever 
the coast line has been extended seaward by accretion, or exposed wher- 
ever the ocean tends to encroach upon the land. As a matter of fact, 
this is not the case in Brazil. 
Dr. Dall says? that in Florida “ Coquina rock, frequently composed 
more of sand grains than of shell, . . . is doubtless being formed at 
many points along the Gulf.shore, though in small quantities at each 
place, and not at all in the lagoons and harbors.” He mentions a recent 
rock that contains land and marine shells, in some places soft and in 
other places (without fossils) ringing under the hammer. What cements 
this rock he does not state. Another is said to be hardened by iron 
brought out in spring waters ; still another is hardened by lime coating 
the sand grains. (Loc. cit., p. 164.) 
In order to ascertain whether recently consolidated beaches were 
known about the British Isles, I have corresponded with Mr. W. Whita- 
ker, lately President of the Geological Society of London, and some 
1 Murray and Irvine. Nature. June 12, 1890, XLIL, p. 163. 
2 W. H. Dall, Notes on the geology of Florida. Amer. Journ. Sci., 8d ser., 
XXXIV. p. 163. 
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