112 



Geology of Ban(jalore, and of 



[Jan. 



full of elegant moss-like impressions, most likely oxide of manganese; 

 the blue kind does not seem to possess them, but both contain imbedded 

 small crystals of glassy quartz. On the other side of the bridge, the 

 bed of the river is very rocky, and the rock exposed is a gneiss with 

 much red felspar, black or blueish black mica, white quartz, and veins 

 and patches of a light green substance, actynolite. Near this last and 

 forming the bank of the river is a large quantity of kunkar, having a 

 decomposed water-worn and almost osseous appearance. The surface 

 rock on the island is hornblende, and in one place, opposite the Banga- 

 lore gate, leading to the public bungalow, it is hornstone, in large tabular 

 masses. From observing the quantity of hornstone in the walls of the 

 fort, I am led to imagine that it must have once prevailed much. The 

 ditch shows gneiss rock decomposing, with beds or dyke-like masses of 

 hornstone traversing it— some of these having a vertical, others an hori- 

 zontal, position. There are also numerous trap dykes. From trap being 

 the common surface rock, with hornstone and the red porphyry above 

 described, we may I think call the locality an igneous one. It is per- 

 haps needless here to mention, that igneous, or rather volcanic, countries 

 like Italy, &c. &c. &c. are highly miasmatous. There is one point it is 

 necessary to touch on, connected with the subject of the geology of the 

 neighbourhood, I mean the soil. To the east and south-east of the fort 

 there is much cultivation. I observed the sugar-cane in particular, and I 

 may in passing just remark the general unliealthiness of those West 

 India Islands where the sugar-cane is cultivated to a great extent. The 

 soil in this direction is of a black colour, which I have no doubt arises 

 from the constant state of cultivation it is kept in, and from the quan- 

 tity of water obtained so easily from the neighbouring river. Where 

 there is much cultivation, and where much water is mixed up with a 

 soil, that soil is generally of a black colour. This water it must be 

 borne in mind passes through an immense tract of jungly country, and 

 must contain a very large proportion of vegetable matter. There is 

 another point also. The bed of the Cauveri is full of large rocks which 

 have a clean and healthy look, at least what would not be imagined 

 miasmatous ; but may not these large rocky masses with pools of water 

 about them generate miasma ? May they not absorb the water and ex- 

 tricate a gaseous and miasmatous principle from the rents and cracks 

 produced by the sun's rays upon the in ? The granite statue of Memnon 

 is well known to have emitted sounds when the morning beams darted 

 upon it, and M. Humboldt, the greatest authority as a scientific travel- 

 ler, mentions that from some of the granite rocks of the Orinoco sub- 

 terranean sounds have been heard, resembling those of an organ, and 



