oct. — dec. 1856.] of the Southern Division. 93 



of titanium in nodular concretions of recent limestone are found 

 here. 



The same kind of granite as mentioned above is found to under- 

 lie all this region to within about 10 miles of the Coleroon ; in some 

 places it is associated with the common granite as its frequent 

 outcrop and disintegrating fragments in the soil plainly show. 

 Nearly all the mountains and hills, however, and most of the vast 

 blocks that nearly cover the surface in some places are syenitic. 

 The granite near the river Coleroon is of the common kind and 

 highly porphyritic. 



At the junction of these two kinds of granite and crossing the 

 road from Madras to Trichinopoly, near the 182nd mile stone from 

 the former place, is a bed of finely and evenly stratified grey sand- 

 stone. The strata are from 2 or 3 inches to T - 0 th of an inch in 

 thickness, and they separate with a fracture so smooth and even 

 that the pieces resemble smooth plates of slate. A specimen ob- 

 tained there is about 2 feet long, one foot wide and 1 inch thick 

 and nearly as even and smooth as a board. The small crystals of 

 felspar contained in it are of the orthaclase species, and of a dull 

 flesh colour. 



The extent of this bed has not been ascertained; it has been 

 traced, however, more than a mile in length, but the width of the 

 outcrop is not more than 10 or 15 yards ; and it runs in a direction 

 nearly east and west. The strata on the south side of the bed are 

 crossed by joints which pass through it nearly parallel to each other 

 and about two feet apart and at an angle of about 50° with the 

 line of direction ; the dip of the strata appeared to be about 60° 

 on the south side and nearly 20° in the centre, while that of the 

 north side was not satisfactorily determined. A singular charac- 

 teristic of this bed is, that the strata on the south side of it are 

 composed of nearly pure silicious sandstone ; in the middle they 

 were porphyritic, containing felspar, while those on the north side 

 were composed almost entirely of a greenish black hornblende, 

 these thin strata forming a beautiful hornblende slate. This ap- 

 peared to be the junction of the two minerals hornblende and mica ; 

 to the north of this, hornblende, either in a free state, or combined 



