38 Dr Chamisso on the Coral hlunds of the Pactjic Ocean. 
Their situation with respect to each otherj-a^ they often form 
rows, their union in several places in large groups, and their to- 
tal absence in other parts of the same seas, induce us to conclude, 
that the corals have founded their buildings on shoals of the 
sea ; or, to speak more correctly, on the tops of mountains lying 
under water. On tb.e one side as they increase, they continue 
to approach the surface of the sea, on the other side they en- 
large the extent of their work. The larger species of corals, 
which form blocks measuring several fathoms in thickness, seem 
to prefer the more Violent surf on the external edge of the reef; 
this, and the obstacles opposed to the continuation of their life, 
in the middle of a broad reef, by the amassing of the shells 
abandoned by the animals, and fragments of corals, are probably 
the reason that the outer edge of the reef first approaches the 
surface. As soon as it has reached such a height, that it re- 
mains almost dry at low water, the corals leave off building 
higher ; sea-shells, fragments of coral, shells of echini, and 
their broken off prickles, are united by the burning sun, through 
the medium of the cementing calcareous sand, which has arisen 
from the pulverisation of the above-mentioned shells, into one 
whole or solid stone, which, strengthened by the continual 
throwing up of new^ materials, gradually increases in thickness, 
till it at last becomes so high, that it is covered only during 
some seasons of the year by the high tides. The heat of the 
sun so penetrates the mass of stone when it is dry, that it splits 
in many places, and breaks off in flakes. These flakes, so sepa- 
rated, are raised one upon another by the waves at the time of 
high water. The always active surf throws blocks of coral 
(frequently of a fathom in length, and three or four feet thick,) 
and shells of marine animals, between and upon the foundation 
stones; after this the calcareous sand lies undisturbed, and 
offers to the seeds of trees and plants cast upon it by the waves, 
a soil upon which they rapidly grow, to overshadow its dazzling 
white surface. Entire trunks of trees, which are carried by the 
rivers from other countries and islands, find here, at length, a 
resting place, after their long wanderings ; with these come 
some small animals, such as lizards and insects, as the first in- 
habitants. Even before the trees form a wood, the real sea- 
birds nestle here ; Ttiavcd land-birds take refuge in the bushes , 
