APPENDIX. 



41 



O'Riley 1 (1850) considers that laterite is formed by alteration of granitic 

 rocks, but gives no evidence in favour of this view. 



The view that laterite is formed by decomposition in situ of trap is strongly up- 

 held by Capt. Wingate 2 (1852), whose observations were made in the Southern 

 Konkan. His chief arguments are that laterite is always a superficial rock; that 

 there are many cases of rocks of different kinds partly transformed into laterite ; 

 and that laterite presents distinctive peculiarities according to the nature of the 

 subjacent rock. Laterite is almost limited to regions where there are heavy and 

 long continued rains; but a similar rock is found in dry parts of the interior of the 

 country in localities exposed to the action of running water. He describes a 

 nodular trap with the outer concentric coats of the nodules converted into laterite 

 and the harder centres unchanged. 



In the Edinburgh New Philosophical Journal for 1852-53, there is a paper on the 

 geology of Ceylon by E. F. Kelaart. 3 He agrees with Clark in his classification of 

 lateritic rocks, and states that the lithomargic variety is the most abundant in 

 Ceylon. In Ceylon the laterite is never known to overlie or be interstratified with 

 sedimentary beds as it is on the coast of Travancore. The stratification of the 

 gneiss is often preserved in the laterite derived from it. He concludes that the 

 laterite of Ceylon is formed by decomposition in situ of gneiss, and thinks it 

 probable that detrital laterite is formed by disintegration and redeposition of the 

 other variety. 



The laterite of the Southern Konkan was re-examined by Lieut. Aytoun, 4 

 (1856), and he agrees with Captain Wingate that it is formed by decomposition of 

 the trap. He says that there is a great deal of iron in the Konkan rocks. In his 

 section of Vingorla headland he shows a hard detrital laterite forming a crust on 

 the top of the thicker mass of softer laterite that has been formed by decomposi- 

 tion in situ. 



Another observer on this part of the coast, F. Broughton, 5 also comes to the 

 conclusion that laterite is formed by the decomposition of trap. He says that 

 there is always a layer of homogeneous and intensely-red clay between the trap and 

 the laterite, and this layer is soft till exposed to the air, when it becomes hard 

 and like laterite. He considers that a plentiful supply cf rain is necessary for the 

 formation of laterite. On one point mentioned in his paper, very few modern 

 geologists will be found to agree with him. He believes that the elevation of 

 the Ghats took place after the formation of laterite. This was the view held by 

 Elie de Beaumont ; but it was successfully combated by Capt. Newbold. 6 



Carter, 7 in his Summary of the Geology of India, adopts Voysey's view 

 that laterite is a trappean rock, one of the latest outbursts of the Deccan trap. 

 Depending on the observations of Stirling, he thinks that the laterite of Cultack 

 or Orissa has been intruded through the granite. In this he appears to have 

 misunderstood Stirling who, though he mentions that the mixture of laterite and 



1 Journ. Ind. Archip., IV, 199. 



2 Trans. Bo. Geog. Soc, X, 287. 



3 Edin. New Phil. Journ. LIV, 28. 



4 Edin. New Phil. Journ. ser. 2, IV, 67. 



5 Journ. Bo. As. Soc, V, 639. 



6 Journ. Roy. As. Soc, XII, 80. 



1 Geol. Papers on Western India, 710. 



( 241 



