40 On Coral Reefs and Islands. 
3. Rate of Growth of Reefs. 
The formation of a reef has been shown to be a very differ- 
ent process from the growth of a zoophyte. Its rate of progress 
is a question to be settled by a consideration of many distinet 
causes, and the rapid voyage of an Expedition affords no oppor 
tunity for definite conclusions. __ 
a. The rapidity of the growth of zoophytes is an element in 
this question of great importance, and one that should be deter- 
mined by direct observation with respect to each of the species 
which contribute largely to reefs, both in the warmer and colder 
parts of coral-reef seas. : 
6. The character of the coral plantation under consideration 
should be carefully studied: for it is of no little consequence 
know whether the clusters of zoophytes are scattered tufts over 
a barren plain, or whether in crowded profusion. Compare the 
debris of vegetation on the semideserts of California with that of 
regions buried in foliage; equally various may be the rate of 
growth of coral rock in different places. Some allowance should 
also be made for the shells and other reef relics. The amount 
he course and extent of fresh waters from the land, and — 
their detritus, should be ascertained. , | 
he strength and height of the tides, and general force of 
the ocean waves, will have some influence. 
Owing to the action of these causes, barrier reefs enlarge and 
extend more rapidly than inner reefs... The former have the full 
action of the sea, and are farther removed from the deleterious | 
influences which may affect the latter. ae 
As stated above, no results were arrived at from observations — 
made in the course of the voyage through the Pacific. The get 
eral impression that their progress is slow, was fully sustained: — 
The facts, with regard to the growth of zoophytes, give some- 
data, though by no means satisfactory. bs pn ee 
nee bai 
pals 
