■so ON THE GEOLOGY 



The upper part of the trap of *S'a oar, like that of Patteriya, is fre- 

 quently globular, the nuclei of the decaying masses varying in size from 

 an egg, tea large bomb-shell ; and their decomposing concentric lamellae, 

 being generally very thin, and often very numerous ; the best specimens 

 are too heavy to send, but that which accompanies this paper, will per- 

 haps serve to explain my description. 



Under the stratum of globular trap which usually occupies the 

 highest part, is a bed of indurated wacken, or amorphous trap, of a 

 rusty brown colour ; sometimes scoriform, or of a small cavernous 

 structure, and sometimes columnar ; but this last form I have only observ- 

 ed in the beds of streams, or on the borders of the formation ; under the 

 amorphous trap is a stratum of lime-stone, white as chalk, which is observ- 

 able at Sagar, and in the hills near Pattariya. 



I have termed this white rock earthy lime-stone, because I know not 

 what other name to give it ; its principal component is carbonate of lime, 

 and next to that is alumine ; it also contains silex, and when it abounds, the 

 rock is converted into chert : felspar does not seem to be abundant, and 

 though the rock occasionally assumes the texture of indurated clay, and 

 sometimes, though very rarely, the hardness of clink-stone, yet, generally 

 speaking, it appears as if partially calcined, and when the ^rajowith which 

 it is associated reposes on sand-stone, as is the case in the district of Sagar, 

 it contains nodules of sand-stone imbedded in it ; the accompanying speci- 

 mens exhibit its most ordinary changes above the surface ; but several wells 

 have been dug at Sdgar, and its changes below the surface are shewn in 

 a second series, sent herewith, one of which appears to be almost pure 

 alumine; a thin ja^pery stratum sometimes intervenes between the 

 and the limestone^ 



Below 



