RED SEA. 
263 
tion is more probably due in great part to currents having 
drifted sediment over an uneven bottom. It is almost 
certain that their form cannot be attributed to the growth 
of coral. The greater number of banks on the eastern 
side of the Red Sea seems to have originated in nearly the 
same manner, whatever this may have been, as the Dlialac 
and Farsan archipelagoes. I judge of this from their 
similar configuration (in proof of which I may instance a 
bank on the east coast in lat. 22°) and from their similar 
composition. The depth, however, within the banks north- 
ward of lat. 17° is usually greater, and their outer sides 
shelve more abruptly (circumstances which seem to go 
together) than in the Dlialac and Farsan archipelagoes; 
but this may have been caused by a stronger action of the 
currents during their formation : moreover, the greater 
abundance of living coral on the northern banks, tends to 
give them steeper margins. 
From this account, brief and imperfect as it is, we can 
see that the great chain of banks on the eastern side of the 
Red Sea, and on the western side of the southern portion, 
differ greatly from true barrier-reefs, which are wholly 
formed by the growth of coral. Elirenberg also concludes 
(Ueber die, &c. pp. 45 and 51) that these banks owe their 
origin in a quite secondary manner to the growth of coral. 
He remarks that the islands off the coast of Norway, if 
worn down level with the sea, and merely coated with 
living coral, would present a nearly similar appearance. 
It seems, however, from information given me by Dr. Mal- 
colmson and Captain Moresby, that Elirenberg has rather 
under-rated the influence of corals on the formation of the 
tertiary deposits of the Red Sea. 
The West Coast of the Bed Sea between Lat. 19° and 22°. 
— Reefs exist here, which, if I had known nothing of the 
others in the Red Sea, I should unhesitatingly have con- 
sidered as barrier-reefs. One of these reefs, in 20° 15', is 
