66 



SKETCH OF THE 



occurring at and near Siana. The hill fort of Sdhar is situated on an 

 isolated rock of this formation. The hill exhibiting an exactly similar 

 shape to those oiNakum, (see section p. 50.) The rocks of this belt I look 

 upon to be the last formed of the great primitive series of Central India, 

 and they deserve more than any others which I have seen to be consi- 

 dered as belonging to the submedial class. 



It would appear that the cause which operated in forming the strata 

 of this district was liable to great, though not to sudden, alterations, — that 

 the purest variety of rock formed was quartz,^ — ^that to this, under pecu- 

 liar circumstances, other ingredients were added, — sometimes mica alone, 

 sometimes felspar, hornblende, &c., and sometimes alumina, and that 

 this forming cause had a constant tendency to revert to that state to which 

 pure siliceous rocks owed their formation,' — ^the original constituents 

 of felspar, argillaceous rocks, &c. being occasionally superadded to 

 those of the siliceous rocks, modifying their external structure, color, &c. 

 according as the former were more or less abundant. I here merely state 

 the broad principle without speculating on the nature of this forming 

 cause. The granitic rocks might have been first formed, and the forming 

 cause might have gradually acquired that state to which the pure sili- 

 ceous rocks owed their formation ; this cause might undergo another 

 gradual alteration, and thus, from the superabundance of one or other of the 

 original ingredients, constituting the solid strata of the earth, various 

 modifications of these might have been produced. 



The wonderful powers of cliemical affinity — powers to which it is 

 impossible to assign any limits, — and the changes which result from the 

 absence, or presence, or superabundance of particular ingredients, all of 

 which circumstances modify the attractions and repulsions of the original 

 atoms of bodies for each other, are well known to every Chemist, and it 



