FRYER— FORMATION OF ALDABRA, ETC. 399 



appear to exist, but we know that during the French occupation of Mauritius there was 

 a regular trade in land-tortoises, which were much esteemed as food both in the Seychelles 

 and Mascarenes ; it is from the captains and ships employed in this trade that the names 

 of the various places on Aldabra have been obtained. 



As the tortoises became scarce the trade fell off, and eventually, after the Seychelles 

 became British, was prohibited altogether. 



Of scientifically -trained observers the first to visit Aldabra was Dr Abbott, who spent 

 some months there in 1893, and obtained fairly complete collections of the larger forms of 

 life*. Dr Voeltzkow, in the course of his travels in East Africa t, spent a month on the 

 atoll, and made observations on its structure ; but neither of these explorers in the time at 

 his disposal was able to penetrate the dense jungle with which it is clothed, and so then- 

 observations only apply to scattered areas. 



A bird collector for the Tring museum spent a year there, and in 1906 Lord Crawford 

 in the " Valhalla "J touched for a day or two; in 1907 Messrs Thomasset and Dupont 

 made a short visit, and obtained samples of the flora, rocks and guano. From a structural 

 point of view, however, the atoll was quite unknown, and as the late Professor A. Agassiz 

 even thought of investigating it himself §, no doubt was felt as to the advisability of 

 further exploration. 



Politically all the islands of the series are dependencies of the Seychelles, with the 

 exception of Farquhar, which is under the administration of Mauritius. They are leased 

 by the Crown at an annual rent, the lessee importing labourers and deriving what profit 

 he can from the export of guano, mangrove bark and green turtle. The present lessee is 

 M. D'Emmerez de Charmoy, of Mahe, to whom I am very grateful for permission to visit 

 the islands, and for much assistance when there. 



To complete this introduction a few more words must be said as to the general 

 topography of the Aldabra series. Their position has already been roughly defined ; it 

 may be pointed out in addition that the neighbouring lands are the Seychelles to the 

 north-east, the Amirantes to the north, Africa to the west, the Comoros, volcanic islands, 

 to the south-west, Madagascar to the south, and the Saya de Malha Bank and the open 

 expanse of the Southern Indian Ocean to the east. Of the various islands, Aldabra is the 

 most westerly ; Assumption lies 20 miles to the south-east, and Cosmoledo 70 miles to the 

 east (E. by S.) ; Astove, the most southerly, is some 20 miles south of Cosmoledo, while 

 180 miles to the east is Farquhar, to the north of which at distances of about 70 miles are 

 Providence and St Pierre. 



Unlike the Maldive or the Seychelles series of islands, the Aldabra series has no 

 shallow bank from which its various members arise, though it may be mentioned that 

 there are indications of a deep bank some 1000 fathoms from the surface of the sea; all 

 the islands therefore are separated by depths of at least 1000 fathoms. 



* A short account of Aldabra by Dr Abbott is to be found in the Proc. of the U.S.A. Mus. Vol. xvi., 

 p. 597 : in the same volume are papers on the mammals, birds and reptiles which he obtained. 



t Wissenschaftliclie Ergebnisse der Reisen in Madagaskar und Ost-Afrika. 



| Vide Three Voyages of a Naturalist, Nicoll. 



§ The Geographical Journal, Sept. 1910, "The South- West Indian Ocean" (discussion on), Prof. J. Stanley 

 Gardiner. 



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