614 Extracts from the Minute Book of the Geological Society. 
I could not proceed further until it was enlarged, when it opened 
into a cavern in the grauwacke, of perhaps twenty yards in length, 
six to ten yards in breadth, and from three to six feet in height 
towards the middle : the roof, forming an irregular arch, running 
down to the floor on each side. About one-third of the surface 
of this roof I found studded and frosted over in patches with 
stalactites of coralloidal arragonite, the branches of which extended 
to a great length in all directions, in straight and variously curved 
lines. The cause of the difference observable between the common 
calcareous stalactites of the outer fissure and those of the inner 
cavern, which consist of coralloidal arragonite only, appears to 
me worthy of investigation. 
<c The fissures and cavern are kept in a constant state of humidity 
by water penetrating through the superincumbent ground, which 
is but a few yards in depth. The vapour arising from this in the 
cavern is considerable, and I am informed, often appears issuing 
from the mouth of the fissure in cold weather. ,, 
1818, January % 
An extract of a letter from Capt. D. Carmichael, F. L. s. on the 
geological structure of part of the Cape of Good Hope, was read. 
“ The Table mountain and the Lion’s head rest upon a base of 
granite; Green-point, Table valley, and the Devil’s hill, on a base 
of schistus, of which the whole of the Lion’s back is likewise 
composed. The granite extends up to the rocky crown of the 
Lion’s head, an elevation of nearly 1500 feet ; and the declivity of 
the mountain is strewed with enormous masses of it, rounded by 
successive exfoliations, and entirely detached from the soil. On 
the side of the Table mountain, the space on which the granite is 
visible is contracted to about 500 feet, and occupies the centre of 
the declivity. 
