486 PBOCEEDIKGS OF THE GEOLOaiCAL SOCIETY. [June 17, 



at many points by the different rivers falling into the Bay of Bengal. 



This belt has been examined and surveyed by my colleagues, 

 Messrs. Blanford, Charles Oldham, King, and myself, from the 

 neighbourhood of Tanjore northward, very nearly up to Ongole, a 

 distance of upwards of 300 miles. 



To the southward of Tanjore the laterite is said to extend over 

 great part of the Tondiman Rajah's country, and, with interruptions, 

 nearly down to Cape Comorin ; but it has not been examined by any 

 members of the Ueological Survey of India for more than 10 miles 

 south of Tanjore. To the north of Ongole it will no doubt be found 

 again, occurring in patches along the coast, until it joins the laterite 

 of Orissa, so well described by Mr. William T. Blanford in the ' Me- 

 moirs of the Geological Survey of India ' *. 



The width of the belt of laterite varies considerably, but rarely ex- 

 ceeds from 8 to 10 miles; in very many places, however, small outlying 

 patches, a few acres, or sometimes only a few square yards in extent, 

 occur at considerable distances to the westward, showing how much 

 has been removed by denudation. The seaward or eastern margin 

 of the belt has generally a well-defined edge ; indeed it frequently 

 terminates in a low but abrupt scarp. 



The western boundary, on the contrary, is often very ragged, the 

 deposit having thinned very much, and its continuity having been so 

 much broken by denudation that it often becomes impossible to se- 

 parate it from the highly ferruginous red soil of the country, this 

 red soil being itself in very many places nothing but reformed lateritic 

 debris. 



No organic remains having as yet been found in the lateritic 

 formations, some fragments of silicified wood excepted, the only thing 

 to guide us in determining their origin is their position, which is 

 that of a great fringe along the eastern flanks of the high land. 

 This is quite analogous to the geographical position of the underlying 

 Jurassic, Cretaceous, and Postcretaceous rocks, all of which are of 

 unquestionably marine origin. This analogy of position holds good 

 also with reference to the recent coast-alluvium, and is, it appears 

 to me, fully sufficient to justify the conclusion that the lateritic 

 formations were deposited along the shore of a moderately shallow 

 sea. 



The typical laterite f is a red ferruginous clay, more or less sandy, 

 and often containing nests of white, yellow, and pink lithomarge 

 and clay, but enclosing, as a rule, no other substances ; near Madras, 

 however, the laterite, though maintaining these characters to some 

 extent, often includes numerous pebbles of quartzite, with a few of 

 quartz and gneiss, and becomes a regular conglomerate, in which 

 occur the chipped implements. In some parts of the Madras district 

 the laterite loses its clayey character to a great extent, or even 

 altogether, and passes into coarse gravel and gravelly sands, con- 



* Vol. i. p. 280. 



t The name Laterite was given by Dr. Francis Buchanan, who described the 

 laterite of the Western Coast in his ' Journey from Madras through Mysore, 

 Canara, and Malabar,' London, 1807, 3 vols. 4to. Vide vol. ii. pp. 436 & 440. 



