120 Dr Christie (yii the Meteorology, Geology, ^c. 



ny *, and occasionally also zeolites. In the hot season, it is every- 

 where traversed by deep fissures ; which, in some cases, have a^ 

 great appearance of regularity, like that observed in dried starch ; 

 but most commonly they are perfectly irregular. The late Dr. 

 Voysey, when at Hydrabad, subjected some of this clay or cotton 

 ground to the heat of a steel furnace, which fused it into a black 

 glass. 



The black colour of this clay, the carbonate of lime, agates, 

 and zeolites found in it, and its conversion into a black glass by 

 heat, all indicate that it has originated from the disintegration! 

 of trap-rocks. The extensive distribution of the trap-rocks makes 

 this inference still more conclusive. The soil which covers, the 

 trap-hills, and which we are certain has originated from the dis- 

 integration of the subjacent rock, exactly resembles the cotton 

 ground of the extensive plains. Were this cotton ground to be 

 again consolidated, it would form an immense overlying forma- 

 tion of a substance resembling basalt or wacke. Its very great 

 importance in the agriculture of India will be considered here- 

 after. 



Several deposites of calcareous tufaoccur in the Darwar district; 

 There is one of considerable extent near Badamy. It is covered 

 by the soil, and appears to rest upon the transition rocks. Some- 

 times nodules of calcareous tufa are found disseminated through 

 the cotton ground, and materially affect its agricultural proper- 

 ties. From its being thus associated with the cotton ground;"! 

 think it is highly probable that the calcareous tufa has, in many 

 instances, owed its origin to the calcareous spar of the trap-rocks, 

 of those rocks the debris of which now forms the cotton ground. 

 The tufa is used for the preparation of mortar. 



In concluding these observations, I have much pleasure in ex- 

 pressing my acknowledgment to Professor Jameson for having 

 corrected some of my observations, and for his valuable re- 

 marks upon my specimens of the rocks of the Southen Mah- 

 ratta country. 



• The same circumstance is noticed by Dr Adams in regard to the black soil 

 ^f the Nerbudda valley* Memoirs of the Wernerian Society, vol. iv. p. 52. 



( To be continued.) 



