162 On the Granite formation 



this district, the granite ranges generally take a ramified 

 form ; spurs branching off form the sides of the principal 

 ridges, and these again branch off into other spurs. 



Associated with the granite rocks and hills, and answer- 

 ing in every point with the peculiarities of general appear- 

 ance and outward form of granite, are found in several 

 points, hills of white quartz near Denkanicottah ; of black 

 trap at Yepsundrum and Rasheegootah, four miles south 

 of Royacottah ; of hornblende rocks and greenstone at 

 Soodnoor in the same direction ; of syenite and porpheri- 

 tic syenite near Salem ; of pegmatite largely laminated with 

 black mica at Arnagherry ; but as these hills rise from the 

 plain of the schistous series by which they are surrounded, 

 I have been unable to find any clue to the mode of junction 

 with the granite, except in the case of the hornblendic rock 

 and greenstone hill at Soodnoor, and the black trap hill at 

 Yepsundrum ; in both of which the junction is by a sudden 

 division between the two, without the slightest graduation 

 or alteration of either rock in structure, mode of aggregation, 

 or composition. 



Structure of Hills. 

 I have above remarked that a common structure of gra- 

 nite hills is of rounded blocks piled together, of a loose 

 heap of irregular masses. Dr. McCulloch, and writers in 

 general, have referred the origin of these piles of loose 

 block to the prismatic division of the granite by joints, and 

 to the rounding of these masses by the action of the weather 

 upon the angles. 



Dr. Christie, in his description of the Marhatta country, 

 has referred the origin of this structure to erosion of the 

 softer parts of the granite, and has pointed out that the 

 rounded blocks, although apparently thrown together by 

 chance, are still in situ; for that veins of quartz may be 

 traced through all the blocks, intersecting them all in the 

 same line. An accurate examination of these hills would have 



