THE FORMATION OF THE MALDIVES AND LACCADIVES. 183 
group in the pictorial method of expression by means of the accompanying diagrammatical 
section of the outside of a bank (fig. 33) as I suppose it to have been formed :— 

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Fie. 33. Scale in fathoms. 

A. Basis of primitive rock, cut down by the action of the currents to this depth. This is 
deeper in the central basin of the plateau and in the channels between the several banks 
on account of additional erosive action since the latter commenced to grow up. 
B. Upgrowth of a shoal by means of deep sea corals assisted somewhat by nullipores and 
other organisms. The more densely shaded area at the top shows the line in which the 
deep corals cease to grow and the reef forms commence; the reef, however, is in this 
part mainly built up by the intermediate depth corals and other organisms, 
Outward extension of the reef by means of detritus, swept off the reef above by the currents. 
Surface reef formed by true corals, nullipores, ete. 
Land, formed by elevation or a change of level of the ocean. 
Lagoon, formed partially by the more rapid growth of the organisms on the edge of the 
bank, building up an encircling reef, and partially by the subsequent solution of the central 
parts. 
So les 
(To be continued.) 
G. 24 
