masXmarhu island. 
319 
To the arguments advanced by the author already 
quoted we add the diagrams annexed, for the use of which 
we are indebted to the courtesy of Messrs. Macmillan & Co. 
They appeared in Nature (vol. xxxvi. p. 413), illustrating a 
communication from Captain Wharton, and represent two 
sections on a true scale, made by Captain Maclear (H.M.S. 
‘Flying Fish,’ of the slope of the coral reef surrounding 
the small island of Masdmarliu, situated in the Red Sea 
in lat. 18° 49' N., long. 38° 45' E. The dotted lines show 
where the soundings were obtained, and the words indicate 
the nature of the bottom. 
It will be observed that there is a remarkable and 
significant correspondence between these two sections, 
which, as the plan indicates, are taken nearly half a mile 
apart. In each the surface of the fringing-reef, after 
shelving very gently dowmwards to a depth of about three 
or four fathoms, is bounded by a submarine cliff. This in 
one section (No. I.) continues almost unbroken to a depth 
of about 500 feet, except that a kind of ledge or terrace is 
clearly indicated at a depth of rather less than 100 feet. 
In the other section (No. II.) the foot of a great submarine 
cliff is found at about 500 feet, but in this case the cliff is 
distinctly divided into two precipices by a shelving bank oi 
coral and sand, which begins at a depth of about 140 feet 
and reaches the brow of the lower precipice at about 260 
feet. This bank is covered by ‘ sand and coral.’ At this 
depth in each section the island is, as it were, defended 
by a deep and narrow ditch, the edge of its steep glacis 
being formed by a sharp arete of coral which in one case 
rises into soundings of about 250 feet. From this the 
former section shows a second rapid fall down to another 
ditch, the bottom of which lies more than 1,200 feet below 
the sea level. This in section resembles the other one, 
and the height of its counterscarp is more than 300 feet. 
From the edge of this the glacis for a short distance is nearly 
