DECCAN TRAP IRON-CLAY. '209 



and having larger vermiform and pipe-like hollows ramifying through 

 it, which last are generally rudely vertical." " On the bund of Gopen- 

 pully tank and thence through the village and down to the lower pla- 

 teau leading towards Yekali there are numerous sections exposed of this 

 ferruginous rock. At the surface or towards the top of the cliffs the 

 rock is like the ordinary brown pisolitic laterite. This graduates down- 

 wards to a yellower clayey variety with irregular sinuous vermiform 

 cavitieSj and below this is a purple clayey rock with yellow and brown 

 mottlings. I saw no trace of conglomerate or of detrital matter in the 

 faces of the cliffs. There are, moreover, indications of globular weather- 

 ing as of trap and of vertical jointing at wide intervals.''^ No signs of 

 bedding exist, except such as are due to the presence of the three not 

 sharply-defined bands of color above described. Mr. King arrived at 

 the conclusion that the iron-clay was the result of decomposition in situ 

 of trappean rocks, the same conclusion as forced itself upon me in the 

 Sahyadri mountains. The iron- clay of the Bidar plateaux occupies a 

 position corresponding precisely with that of the ''summit bed^^ in those 

 mountains. 



There is a difference in the mineral condition of the iron-clays of the 

 two regions, which is noteworthy, — namely, that in the ghats the ferru- 

 ginous constituent of the rock is very largely, mainly indeed, in the 

 condition of haematite, the red anhydrous peroxide of iron, while in 

 the Eastern Deccan it consists of limonite, the hydrous or brown peroxide 

 of iron. The color varies accordingly, being red of various shades in 

 the ghat region and brown in the Bidar plateaux. The red color is 

 very conspicuous in the former region, so much so that the native 

 (Mahratta) name is " Tamara Donda,-'-' or " the red rock.^^ 



Beside the great deposit of '' lateritoid" iron-clay just described, 



are others in the ghat region at lower levels, but 

 Other iron-clay beds. 



all apparently of similar origin and presenting no 



differences recognizable by ordinary inspection. All the peculiar dif- 



lerences of structure noted in the '' summit bed'" can be paralleled in 



2 c ( 309 ) 



