1845.] Notes on the South Mahratta Country, fyc. 287 



varieties seldom contain silex sufficient to give them the character of 

 Kaolin. The whole mass is sometimes reticulated by veins of a brown 

 ferruginous quartz and impure iron ore, (often split in the centre, and 

 the sides of the fissure lined with quartz crystals) having apparently 

 no decided direction. Iron pyrites are seen in the chloritic schists; 

 this rock, particularly in the vicinity of trap dykes, has a tendency to 

 the prismatic and rhomboidal forms, in which the lamination, though 

 generally obscure, is sometimes still distinctly traceable. A system of 

 joints running nearly at right angles with those of lamination, often in- 

 tersect the whole group of these schists. These jointed portions are not 

 capable of that indefinite subdivision into similar solids by which Pro- 

 fessor Sedgwick justly observes, the true cleavage planes may generally 

 be distinguished from the joints. The difficulty in the schists of the 

 S. Mahratta country is to discriminate between the planes of cleavage, 

 and those of mechanical deposition, or chemical precipitation, for 

 which there are three good tests, viz. the interstratification of another 

 bed of rock, the coloured bands of successive deposition, and a pecu- 

 liar, but slightly dimpled appearance on the surfaces of the planes 

 never seen on those of cleavage. From the occurrence of the latter 

 on the planes of the lamina of the Darwar rocks, and from the iron and 

 dip of the large interstratified beds of quartz and silicious schists, I 

 am inclined to consider that the true lines of stratification run nearly 

 parallel with that of elevation, viz. nearly N. W. and S. E. } and that the 

 laminae are those of deposition ; while the microscopic fissures by which 

 the rock is cleft into rhomboidal and prismatic forms may be received 

 as those of true cleavage. 



My friend Captain Allardyce, who has minutely examined the rocks 

 about Darwar, writes me that the direction of the laminae and that of 

 stratification keep very constant to one point of the compass, viz. N. W. 

 by N. for a great distance, perhaps over an area of from fifty to one hun- 

 dred miles. One may pick up a fragment of chlorite slate of a trian- 

 gular, pyramidal outline, the external planes of which will be ferrugi- 

 nous, while the interior is divided into minute laminae not ferruginous, 

 and coincident with only one of the planes. On examination of the 

 rock in situ, this minute lamination is found to be vertical, and invari- 

 ably divided N. W. by N., conformable, in short, to the line of eleva- 

 tion. The chloritic schist N. of Darwar is of a bluish green tinge, 



2 s 



