442 Mr. (1. C. Bourne. The Atoll of Diego Garcia [Mar. 22, 



obvious after a short examination that some parts of the land are 

 older than others, and that the great strip of land was formerly a 

 series of disconnected islets which have since been joined together by 

 the accumulation of sand and coral debris between them. In the 

 older parts of the island, which have apparently been covered with 

 vegetation for a considerable period, a thick peaty mould has been 

 formed by the decay of fallen leaves and stems of trees and shrubs. 



Throughout the island the outer or seaward shore is higher than 

 the inner or lagoonward shore, owing to the pile of coral boulders 

 thrown up in the form of a low rampart along the former by the 

 action of the waves. In most places a flat reef extends fully 60 yards 

 seaward of the rampart; and this reef is just uncovered at low spring 

 tides. As a rule the inner shore slopes gently down into the lagoon 

 for some distance and then pitches down rather suddenly to a depth 

 of 10 or 12 fathoms, but in some places there is a depth of 6 or 8 

 fathoms close up to the inner shores. Marshy pools of fresh or 

 brackish water are found in the centre of the strip of land on the 

 S.E. and W. sides of the island ; into these the sea enters in many 

 cases during the highest spring tides, and at the S.E. and S. ends of 

 the island it has established permanent breaches into some of these 

 pools, through which the tide runs in and out regularly from the 

 lagoon. Thus there are formed sheets of water like secondary lagoons 

 within the strip of land ; these are known on the island by the name of 

 barachois, and they are of some importance when one comes to con- 

 sider the amount of change which is continually going on in the 

 island. 



Externally the shores slope away very rapidly to considerable 

 depths, the sounding line giving depths of 250 fathoms and upwards 

 at a distance of a few hundred yards from the edge of the reef, 

 excepting at Horsburgh Point at the S.E. side, where a depth of 45 

 fathoms is found at a distance of 1 mile from the shore. Unfortu- 

 nately I had not the apparatus wherewith to make a series of 

 sectional soundings outside the island, nor if I had had the apparatus 

 should I have had the means of making use of it. The depths within 

 the lagoon have been accurately determined by H.M.S. "Rambler " in 

 1885 ; they vary up to 19 fathoms. After a stay of two or three 

 months on the island one cannot fail to be impressed with the im- 

 mense amount of change which is continually in progress. Large 

 masses of sand are in the space of a month deposited in one spot to 

 be swept away during the next month and deposited in another. 

 Everywhere there is evidence that the sea has encroached upon the 

 land or that the land has in its turn gained upon the sea. In one 

 place numerous dead and fallen coco-nut palms show where old 

 established land has been carried away ; in an adjoining spot tracts of 

 sand, either bare or covered with a scanty growth of young shrubs, 



