354 TRANSACTIONS AND PKOCEEDINGS OF THE [Sess. lix. 



and 20° 24' south latitude. On their south-east or wind- 

 ward side the sea becomes suddenly deep, and the 100- 

 fathom line of soundings is reached at a distance of 2 

 miles from the shore. The surf breaks with considerable 

 force on the windward side of the islands, and it con- 

 tinually bathes them with fine clouds of saline spray. 



The islands range from 40—300 yards in length, and 

 from 12—40 feet in height above sea-level at the highest 

 part. They are all formed of the same kind of coralline 

 limestone, and their formation is entirely different from the 

 igneous basaltic rock of the main island of Mauritius. 

 The surface of the limestone is considerably honeycombed 

 by the action of the weather and sea-spray, and in many 

 places the rock projects upwards in numerous sharp 

 pinnacles. Beyond a little limestone debris here and there 

 and a sprinkling of blown calcareous sand at some parts, 

 there is no soil covering the surface of the rock ; and, at 

 some parts of the islands, it is remarkable to see how well 

 the rocky surface is clothed with luxuriant vegetation of a 

 littoral character. 



There are no springs of fresh water on any of the 

 islands, and when rain falls it quickly disappears through 

 the porous limestone. 



The mean annual temperature in the shade is about 75° 

 Fahr. The mean annual rainfall at Anse Jonchee on the 

 adjacent coast of Mauritius, for the 9 years 1880-1888, 

 was 88*58 inches, and the mean annual number of days 

 of rainfall, during the same period, was 142 ; but it is 

 probable that the rainfall of these islands is less, on 

 account of their greater distance from the hills of 

 Mauritius. 



I visited the islands of the group on three occasions, 

 viz., in the cool dry season in October 1888 and September 

 1889, and in the hot rainy season in March 1890, and I 

 thoroughly investigated the flora at these different seasons. 

 During my last two visits I resided for four days on each 

 occasion in the lighthouse on He aux Fouquets. 



I am not aware of any published report on the flora and 

 physical features of these islands, and I have, therefore, 

 entered more into detail than I otherwise would have 

 done, had the flora of the group been better known. 



