Dec. 1861.] Geology of the Neilgherries. 259 



have at first mistaken concave masses in the neighbourhood of 

 larger rocks for separate pieces, but on proceeding to excavate the 

 soil, have discovered them to be merely the concentric coatings of 

 the mass, joined to it below. 



The depth to which decomposition has extended is very con- 

 siderable ; in many cases whole hills have been converted from 

 rock into an earthy soil, in which beds of porcelain-clay are fre- 

 quently met. 



There are many other agents at work in degrading the surface 

 such as roots striking into the fissures of rocks, kc. not necessary 

 to mention, because their operations are well known and every 

 where met with. I have enumerated those which I considered of 

 the greatest importance, and have now mentioned, I believe, most 

 of the leading features which would enter into a geological history 

 of the Neilgherries, condensing the subject as much as possible 

 for the readers and for my own sake. 



In a more complete account of these Hills, the minor geological 

 details of districts and their mineralogical characters, would be 

 inserted between the different heads. The observations of Dr. 

 DeBenza, and my own papers entitled " Contributions to Indian 

 Geology and Mineralogy," would furnish such particular accounts. 

 The foregoing history of causes that have produced existing 

 effects, is for the most part inductive, being the result of nearly a 

 year's careful study of the prevailing geological state of the Neil- 

 gherries. 



