the Island of Tristan da Cunha, 4c. 491 
Wearrived 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 activity, there can remain little doubt that the whole 
of it isof igneous origin. The solid foundation on which it stands 
is undoubtedly lava. The 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-brûlé of the island of Bourbon. 
The climate of Tristan da Cunha is so 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. 
YOL. XII. : 3s According 
