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On the Geological characters of the 



[July* 



The only localities in the immediate vicinity of Madras, as far as I 

 have been able to explore personally, or ascertain from others, where 

 the laterite is found, are the Red Hills and Guindy. Nearer than these 

 two places no hillock arises to break the level uniformity of the plain, 

 on which Madras and its' widely scattered gardens are spread out. This 

 flat character of the neighbourhood has most likely given rise to the 

 former of the two places being dignified with the name of hills ; under 

 that system of baptismal paradox, which frequently operates in 

 giving names to things for qualities which they do not possess — on the 

 lucus a non lucendo principle. 



The so-called Red Hills are situated about eight miles to the north 

 west of Madras. They are mere undulating grounds, scarcely of ap- 

 preciable elevation above the surrounding country, the highest emi- 

 nence not attaining a greater elevation than fifty or sixty feet above the 

 level of the plain. The whole laterite formation occupies a tri- 

 angular area of about fifty square miles, extending nearly ten miles 

 to the westward of the gravel pits on the east side, the nearest point 

 to Madras, and about seven or eight miles in a northerly direction, 

 towards the Cortillyaar at Jermootapolliam. Of this extensive tract I 

 have only been able to explore an area of not more than three or four 

 square miles. 



The line of bearing of these undulations is very irregular, though 

 they generally have, more or less, a direction from S. W. to N. E. 

 From these rising grounds the land descends to what is termed the 

 Lake, which is bounded on three sides by the eminences described 

 above, the waters (when there are any) being confined, on the greater 

 portion of the eastern side, by an artificial embankment, or Bund, but 

 for which there would be no lake at all, as the country descends on that 

 side towards the sea, it is believed about two and a half feet per mile. To 

 the north east a natural drain for the waters from the higher grounds 

 existed, but it has been filled up, at the place of junction with the lake, 

 by a dam and water sluice, after the manner of an ordinary tank, for the 

 irrigation of the country. The old channel, however, remains, and the 

 banks, in some places fifteen feet high, show the mineral structure of 

 the spot. They are composed of a dark ferruginous stone, arranged in 

 a stratiform manner, presenting seams or partings, two or more feet 

 asunder, parallel to each other, and nearly horizontal. Vertical fis- 

 sures intersect the seams at right angles, and thus produce prismatic 

 masses of the rock, which give these natural walls something of the 1 

 semblance of huge artificial masonry. On breaking into the interior 

 of these masses, the rock is palpably a conglomerate. Nodules of 

 various sizes are observed, embedded in a clayey paste, which is very 

 hard and tenacious. These nodules may be picked out, without much 



