Page 265 - Travels in Arabia (Vol 2)

m '246 COAST OF ARABIA. [cm.

i hazard a conjecture, it would be that the
cause must be looked for in the coral being:
more porous on the outer part of the reefs;

this part being composed of the branched
variety, by which the force of the sea is
m
broken, in the same manner as that of a body
4 of water when dashed against a sieve.
*
But, whatever be the cause, it is of practi­
cal importance that the mariner should be
made acquainted with the fact; for, in stand­
ing towards those reefs at night, he may be
lulled into false confidence, and border too

closely on them, under an impression that he
would either hear or see the surf. In the
neighbourhood of, and amidst the clusters,
a chart can avail the mariner no further than
in marking the outer boundary, to which our
attention was therefore especially directed;
within this, the navigator must be directed by
the eye, as the only and the best pilot; and
a short acquaintance with the manner of pro­
ceeding here laid down will enable him to
distinguish the dangers, and also to estimate

from the various shades the changes in the
depth of the water.
In the northern part of the sea, during the