From W. J. L. Wharton   14 August 1878

Dear Sir

With reference to your Coral Reefs 2^nd Ed. Page 243. 244. I am in a position to inform you as to the true facts regarding the Nature of the Farquhar I^s (Juan de Nova) Cosmoledo, & Aldabra having just completed a survey of those islands.¹

They are all true atolls elevated from 10 to 20 feet Aldabra the most; hence I imagine the shallowness of their lagoons none of which are navigable.

Farquhar has had its upraised coral nearly entirely washed away, but it remains it places still to prove its existence. The islands of this small group are all low & covered with blown sand and are reduced nearly to a condition which will not alter.

Cosmoledo Islands are still in many places faced by coral cliffs about 10 ft high, washing away. When these have disappeared the islands are also sand covered. Isolated and undermined rocks & islets of coral connect the main islands on the ring and mark the line of original upheaved reef very distinctly

Aldabra presents externally a uniform face of coral cliff to the sea of course undermined and in process of destruction by the waves. Inside the mangrove is destroying the coral even more rapidly and reducing it to that white mud which is so familiar to me on the East Coast of Africa. I could not level from the highest part to the sea but it must be at least 20 feet above low water.² The entire ring is perfect with the exception of three breaks, two apparently original, and one recently formed by the disintegration of the coral, for it is quite shallow. There is little or no sand on this island. It is covered with a stiff & tangled brush.

The coast on the North part of Madagascar is faced with upraised coral about 15 feet high. Behind is basalt.

Apparently the upheaval in this part of the world has had a tilting motion, as the coast of Africa is raised in places to over 100 feet.

While mentioning Aldabra it may interest you to know that the tortoises are now very scarce.³ Fishing parties from Seychelles have nearly exterminated them but we got one after much search & trouble. We found a little water in this the dry season in the cavities of the rocks and doubtless there is more at other seasons. There is a succulent aloe on which the reptiles probably feed, but the life of a tortoise or any thing else in Aldabra is not enviable for the surface of the island is rock, rough & jagged to a degree, so that it puzzles me how they get about. Our searchers were simply torn to pieces, boots, clothes & bodies. I think I am safe in saying that no one will inhabit Aldabra for thousands of years.

Believe me Sir | Yours truly | W J L Wharton | Commander R.N.

C. Darwin Esq. | L.L.D. FRS.