the Island of Tristan da Citnha, SfC. 491 



We arrived at the cantonment about sun-set, after a most fatiguing 

 journey of fourteen hours. 



In viewing the general structure of the island, and comparing 

 its diminutive size with the great number of spiracles crowning 

 its summit, and which must all have been at one time or another 

 in a state of activit}^ there can remain little doubt that the whole 

 of it is of igneous origin. The solid foundation on which it stands 

 is undoubtedly lava. 'J'he platform which forms the plain is also 

 a sheet of lava ; and though the face of it at one part breaks into 

 prismatic columns, after the manner of basalt, yet the bed of 

 semivitrified rock on which it rests seems to leave no room for 

 doubt with regard to its origin. An entire hill, seven or eight 

 hundred feet high, near the centre of the plain, is composed of 

 nothing but stratified tufa. The plain is encumbered with large 

 detached masses of porphyritic stone, and with others, inclosing 

 crystals of sulphur or of augite, which seem to have been ejected 

 in their present state from the interior of the mountain ; and in 

 one instance I met near the base of the mountain, and under one 

 of its strata, with a specimen of the convoluted lava, so common 

 in the Pays-br(ile of the island of Bourbon. 



The climate of Tristan da Cunho is ao mild, that the herbage 

 remains unimpaired throughout the year. Snow is never seen on 

 the low land ; and the only indicaton of winter is a transient 

 sprinkling of hoar frost, too slight to give any serious check to ve- 

 getation. The thermometer during summer rarely ascends beyond 

 74 degrees in the shade, and stands at about 110° when exposed 

 to the meridian sun. At night it occasionally falls as low as 48 

 or 50 degrees. 



If we may give credit to the information of a man of the name 

 of Currie, who has lived on the island for the last six years, its 

 climate may be regarded as one of the most rainy in the world. 



VOL. XII. 3 s According 



