18 Rev. R. Baron — Rock Cavities in Granite. 



The porpliyritic felspars often show a slight fluxional arrange- 

 ment. The rock, except superficially, is quite fresh, and at the 

 localities where the cavities occur the weathering has not proceeded 

 further, neither in depth nor degree, than in other places. 



The above is a brief description of the granite in which the 

 cavities to be described are found. It must be remembered, how- 

 ever, that many more cavities are known than those here mentioned, 

 and that all these together doubtless form but a very small fraction 

 of those which exist throughout the granitic area. 



The first hole I shall describe is situated in the middle of a per- 

 pendicular face of rock some two-thirds of the way up one of the high 

 hills close by the village of Alarobia. The lower edge of the hole- 

 is 8 or 10 feet above the foot of the rock, and cannot be reached 

 without the aid of a small ladder or other contrivance. The rock 

 at its surface is somewhat weathered, but not more so than in other 

 places. The entrance is nearly round, and some 5 or 6 feet 

 in diameter. Inside, from the roof downwards, the hole measures 

 12 feet, the width is 10, and the depth inwards and horizontally 

 from the entrance is 9. It is in part divided into two portions 

 by a projecting ridge ; these two portions are together roughly 

 separated into eight rounded divisions ; and these again into some 

 three dozen smaller ones, the average being more than sufficient 

 to contain a man's head. The walls are not smooth, and not specially 

 weathered ; in fact, they are much the same as the rock outside. 

 A white powder may be seen here and there on the surface, which, 

 possessing an alkaline taste, may be a potash salt derived from 

 the felspar. 



At the foot of the hill there is a fallen rock, in the face of 

 which are two holes, each about the size of a very large straw 

 beehive. 



Another hole is to be found on the east side of the mountain of 

 Ambohibory, about half-way up. The entrance is about 4 ft. high 

 by 2 ft. 6 in. in width, and of a rounded shape, like that of the large 

 cavity mentioned above. The interior measures 5 ft. 2 in. from the 

 roof downwards ; from the mouth inwards to the back is 4 ft. ; 

 the direction at right angles to this being 4 ft. 10 in. The wall 

 of the cavity contains thirteen or fourteen rounded depressions. 



On the same hill, a little farther south, is to be found another but 

 smaller cavity. Its dimensions are as follows : height 1 ft. 6 in., 

 horizontal diameters 3 ft. by 3 ft. 10 in. There are two entrances 

 near to each other, one 2 ft. 4 in. wide by 1 ft. 9 in. high, the other 



1 ft. wide by 1 ft. 6 in. high. In the interior there are three or four 

 nest-like depressions. 



Not far awa3r, on the same side of the hill, there is another cavity 

 having a comparatively small entrance (about 2 ft. by 2 ft.). The 

 height of the interior is about 3 ft., its breadth from right to left 



2 ft., and its depth from the mouth inwards 5 ft. 5 in. In the wall 

 are six or eight smaller cavities. 



There is another hole a few yards further south on the under 

 side of an overhanging mass of granite. Tiioagh it is small, it 



