96 



Geo^ofjy of Batiffalore, and of 



[Jan. 



says " since neither sort of basalt found at present in Central and South 

 *' India, decomposes into a black soil, what kind of trap and under 

 what circumstances different from the present, could this basalt give 

 rise to such a different product ? Is the general ojdnion of the black 

 soil having resulted from the decomposition of the basalt one of those 

 *' that are repeated only because once tohL" It appears to me that the 

 kind of trap decomposing into black soil is that which contains much 

 lime; for on the Neilgherries, where it decomposes into a yellow clay, 

 no lime has been found; but in the Hyderabad district, described by 

 Vovsey, he mentions as one of the peculiarities of the part, the abun- 

 dance of the carbonate of lime with the wacken, the basalt &c. &c. &c. 

 and in another place he says '* carbonate of lime is intermixed with the 

 rock whether sienite, greenstone, granite, basalt orwacken." 



Bangalore is situated on one of the most elevated ridges of the high 

 table land of Mysore, nearly three thousand feet above the level of the 

 sea. The principal rocks in the neighbourhood are gneiss, granite and 

 trap, the formation being entirely primitive. The grand fundamental 

 rock all over the Mysore may be called a sienitic gneiss, for where 

 deep and extensive sections are opened up to view, the rocky masses 

 are distinctly stratified, and contain more or less of cjuartz, felspar, mica 

 and hornblende. In these sections sometimes beds of quariz and felspar 

 only meet the eye, forming a pegmatite — then again we may find quartz, 

 felspar and mica, forming a true granite or gneiss, and then beds of 

 hornblende and felspar, or hornblende and quartz, forming a hornblende 

 slate. 



All the strata around Bangalore, and also throughout Mysore, run 

 more or less north and south, sometimes north-west and south-east, or 

 north-east and south-west, and the trap dykes and basaltic dykes or 

 veins, which are numerous, and cut through the gneiss, have an east and 

 west direction, but sometimes, as near the Madras road, before entering 

 the cantonment, north-west and south-east. A mass of gneiss, about a 

 mile south of the road, and about two from the village of Ulsoor, runs 

 north-east and south-west, and a basaltic dyke cuts through it, running 

 about north-west and south-east or rather N. N. W. and S. S. E. Some 

 very large nullahs, principally towards the west end of the cantonment, 

 one, two or three miles distant however, show well the constitution of the 

 decomposing gneiss, better than can be seen on the surface, where only 

 the more solid and less perishable portions of the rocks remain. In 

 these nullahs we meet with crumbling masses of felspar — large beds of 

 mica or hornblende, and numerous veins of quartz. The common 

 colour of the mica in the undecomposed rock is black, but exhibiting a 

 variety of shades in decomposition— first, it becomes of a brownish 



