1835.] Geological Sketch of the Neilgherries. 415 



is, which gives those hills the rounded form they exhibit, will be 

 ehown hereafter. 



With the exception of some vertical cliffs and mural precipices, seen 

 in the boundaries of this elevated plateau, and a few projecting 1 masses 

 of the fundamental rocks on the summits and declivities of these 

 hills, the whole group is uniformly covered by a thick stratum of ve- 

 getable earth (No. 1*), which overlying a thicker stratum of red earth, 

 (to be described in the sequel,) supports numerous plants, chiefly grasses, 

 which, growing most luxuriantly in thick contiguous tufts, give the 

 surface a smooth carpet-like appearance. This vegetable earth in 

 general is clayey, and of a grey colour, and very friable. On this 

 soil we occasionally see small rounded pieces of the decomposed 

 subjacent rock, bestrewed particularly on those spots where blocks of 

 the decomposing rock are seen jutting through the soil. 



This vegetable soil is replaced in the low valleys and fiats at the 

 foot of the hills, by a black soil, such as we frequently see forming 

 the peat- bog in swampy grounds, in which a large quantity of vege- 

 table matter is decomposing (No. 2). 



This soil is of a black, or deep brown, colour ; of tenacious consist- 

 ence, when moist ; crumbling into powder, and often splitting into 

 prismatic masses, when dry. At first sight, it resembles the black soil 

 of the plains of India. From this last, however, it seems to differ 

 greatly, in containing a large quantity of carbonaceous matter, and 

 much oxide of iron. 



To deprive this black soil of the greater portion of its humidity, I 

 exposed it to a heat, sufficient to melt lead, and after having weighed 

 a certain quantity of it, subjected it to an intense heat for an hour ; 

 after this, it had lost more than 25 per cent, of the original weight, and 

 had changed into an ochrey red powder (No. 3), without undergoing 

 any vitrification, as is the case with the black soil of the Deccan, 

 (Voysey.) It would therefore appear, that the loss is owing to the oxidi- 

 fication and consequent volatilization of the carbonaceous matter. 



This soil, although more frequently found in low situations, is often 

 seen in a thick stratum on the declivities of the hills, such as on the 

 slope of one of the Dodabetta group, facing the cantonment; on that 

 of the Elk Hills, (S.) above South Downs ; near the Kaiti Pass, and 

 in many other localities, where I have remarked about it, a most luxu- 

 riant vegetation of innumerable ferns, of which the roots are seen 

 decaying into a black powder. 



In many places below this black soil, and sometimes under the 



* The figures refer to specimens deposited in the As. Soc. museum ; the letters 

 to the accompanying Map. — Ed. 

 3 h 2 



