Hicks on the ^Reef=^uilders. 301 
But the Florida reefs are perhaps the least favorable to the 
Darwinian theory of any that could be selected. How is it pos- 
sible, without subsidence, to account for some of thq reefs of 
the Pacific ocean, which are five or ten times as thick as the 
Florida reefs? The reef along the north shore of Tahiti, hav- 
ing a thickness several times the depth at which the reef polyps 
will live, may serve for a test of the two theories as applied to 
a thick reef. This is a barrier reef three fourths of a mile from 
land. The lagoon channel is not too deep for polyp-life, so 
that the reef may have begun where its inner base now rests. 
There is no need of invoking the solvent action of sea water to 
account for the depth of this lagoon. All the interest is con- 
centrated upon the seaward face of the reef, of which the ac- 
companying illustration (fig. i) will give a better notion than 
can be conveyed by words. 
S'E.^- V^^tV. 
o 50 100 ioo 3oo 
» 
Fig I. Diagram of seaward face of the barrier reef at Tahiti, on a true 
■scale vertical and horizontal. After Murray. (A portion of the reef be- 
low d is omitted. The slope diminishes to 6° at the bottom of the portion 
omitted). 
a to b, slope of 18° with colonies of living coral polpys. 
b to c, talvis of large blocks (some 20 and 30 feet long) of reef rock. Av- 
erage slope 45° , maximum slope 75° . 
c to d, slope of 30° composed of coral sand. 
Depth at b, 40 fathoms, at c, loo fathoms, at d, 425 fathoms. 
Horizontal distance from a to b, 250 j^ards, from b to c, 100 yards. 
Murray maintains that the slope from a to b is the great lab- 
oratory for the production of reef matter, all below being 
