106 



On the Geological characters of the 



(July 



But let me proceed to mention the further notices of this rock which 

 are recorded — Mr. Calder, in the subsequent part of his memoir, relates 

 the occasional occurrence of the laterite, but nothing new is elicited re- 

 garding its position and association. From the Caveri to the Pennaar 

 he states, " the surface of the level country seems to consist of the 

 debris of granitic rocks, and plains of marine sand, probably left by 

 the retreat of the sea, with occasional alluvial deposits, and partial 

 beds of iron clay, and detached masses of other rocks of the overlaying 

 class. In approaching the Pennaar river the iron clay formation ex- 

 pands over a larger surface*. Passing on to Vizagapatam and Ganjam, 

 granitic rocks, chiefly sienite and gneiss, predominate, and are occasion- 

 ally covered by lateritef. We trace the laterite, as the overlaying rock, 

 through the district of Medinipur, and thence continuing northward 

 by Bishenpur and Bancora to Birbhum, reposing sometimes on sand- 

 stone, but more frequently on granite or gneiss.";}; 



1 think it will be admitted, on all hands, that there is very little evi- 

 dence, in the above testimony of Mr. Calder, to show any relation be- 

 tween the trap formations and laterite. But let me call in other wit- 

 nesses on the question. 



Captain Coulthard, in a paper on the trap formation of the Sagar 

 district,]! observes ; " The iron clay, so easy to be met with every 

 where, would hardly ever satisfy the mineralogist, for it is for the most 

 part amygdaloidal, and not a simple mineral." This is not a very lu- 

 minous passage ; but, it seems to indicate the author's opinion of the 

 conglomerate character of the laterite. 



I come now to advert to the description given by the lamented Dr. 

 Turnbull Christie, late of the Madras Medical Establishment : " a gen- 



from Dr. Voysey to his address, dated Hyderabad, 5th November 1820, 

 which contains a passage, couched in much more precise and unequi- 

 vocal terms than the quotation from the Journal of the Asiatic Societ?j 

 of Bengal, and most clearly elucidates his views on the subject. 



" The indurated clay you mention is very probably the result of 

 those muddy eruptions so common, and of such extensive occurrence, 

 in S. America. Indeed I am convinced that the green-stone, basalt, 

 wacke, iron clay or laterite, and the indurated clay, have all a common 

 .origin, from the insensible degrees by which they pass the one into the 

 other ; and that they only differ as to the degree of pressure to which 

 Ihey have been subjected when under fusion." 



* Ut supra, p. 9. + Ibid. p. 11. * Ibid. p. If, 

 ,|1 Asiatic Researches Vol. 18, part 1st p. 58, 



