of Salem and Barramahal. 169 



south, coinciding with the direction of the lamination of gneiss 

 formations, and other stratified rocks in general. I have 

 never seen one of these cavities on the side of a rock ; but 

 wherever I have seen them they have been generally so 

 situated as to serve as tanks for containing water ; and in the 

 hill forts they have been enlarged and walled round to con- 

 tain the supplies for the garrison. 



Similar cavities, but of smaller size, are sometimes pro- 

 duced by the decay of portions of porphyritic syenite, and 

 both these and the gneiss cavities often have the shape 

 of the print of a bull's foot, when they have often been made 

 the subject of adoration by the Hindoo natives of the 

 country. 



When these cavities occur in the granite in the beds of 

 rivers, they are frequently enlarged and worked into circu- 

 lar vertical holes by the action of the torrent, giving the 

 stones and sand which lodge in them a revolving motion: 

 thus making what have been called " rock basins" in Eng- 

 land, and have been mistaken for works of art. Dr. Benza 

 (Madras Journal, vol. iv., page 292) gives a complete 

 description and dissertation upon them, and therefore it is 

 only necessary for me here to mention, that in the bed of the 

 Cavery I have often traced the progress of the erosion of 

 these basins through all the stages, from the commencement 

 of a hole not four inches long, to where they have been eight 

 feet and more in depth. 



Rocks and Minerals embedded. 



Besides the syenite, a schorlaceous felspar, porphyry, or 

 grains of black schorl, disseminated in a paste of earthy fel- 

 spar, may be frequently seen embedded in the granite ; but 

 generally in such small quantities, and the grains of schorl so 

 minute, as to render it difficult to distinguish the mineral 

 from the hornblende porphyry ; but it may be identified by 

 its action before the blowpipe, before which it melts much 



