1810.] Notes illusfraiive of the Geology of Southern India. 319 



rugged nakedness, bound the view on every side, and the traveller, fol- 

 lowing the road which winds along their bases, passes through a series 

 of valleys vhere, kaleidescope-like, each turning brings new beauiies 

 before lnm» On approaching Kisnagherry, the principal town in this 

 district, the distant hills occasionally exhibit the ribbed-like appearance 

 characteristic of columnar basalt. The town itself is overhung by one 

 of these, but an examination of it, effected with considerable difficulty 

 and risk, proved that the ribbed appearance was due, not to the exist- 

 ence of coliiuins, but to linear deposits of earthy and fungoid matter, 

 the dark colour of which, alternating with the natural colour of the 

 rock, produced when viewed from a distance exactly the effect of a 

 columnar arrangement. These deposits were formed along the lines by 

 which little streamlets of water trickled down from the summit of the 

 hill, these having doubtless led to the partial decomposition of the rock, 

 and the formation of soil sufficient for the fungi to vegetate in. Nests 

 of hornblende and greenstone were abundantly met with, and the whole 

 of the sienitic mass was traversed by veins of pure quartz. 



The cause of the constant occurrence in primary formations of these 

 segregations of simple minerals in the rocks of which they form constitu- 

 ent parts, is a most interesting, but as yet unsolved question, and one at- 

 tended with peculiar difficulties when experimentally investigated, from 

 the circumstance that the phenomena in question require periods of such 

 extent for their development, as to make it impossible to institute in the 

 laboratory any experiments which would be strictly, and in all points 

 analogous to what obtains in nature. In their original state of igneous 

 fluidity, the operation of the attractive affinities of the molecules of 

 which the different minerals forming granitic rocks are composed would 

 be free and uninterrupted, as has been satisfactorily shewn by the 

 ** pyrochemical" experiments of Maesterlich, and others, who have 

 succeeded in obtaining crystals of the minerals alluded to, from the 

 igneous fusion of their constituents. But, the obtaining of these in 

 their crystalline state, only as detached and individual substances, leaves 

 us still in doubt as to the causes of some of them occurring massive 

 and disseminated. Thus, among others, a curious and most inter- 

 esting fact stated by Mr. Babbage in his " Economy of Machinery," 

 appears to warrant the conclusion, that such segregations take place 

 wben the substances are in a state of aqueous fluidity; for he remarks, 

 " Flints after being burned and ground are suspended in water in order 

 to mix them intimately with clay, which is also suspended in the same 

 fluid for the formation of porcelain. The water is then in part evapo- 

 rated by heat, and the plastic compound, out of which our most beautiful 



