Geological papers on western India, including Cutch, Sinde and the south-east coast of Arabia : to which is appended a summary of the geology of India generally / edited for the Government by Henry J. Carter.

Date:
1857
Catalogue details

Licence: Public Domain Mark

Credit: Geological papers on western India, including Cutch, Sinde and the south-east coast of Arabia : to which is appended a summary of the geology of India generally / edited for the Government by Henry J. Carter. Source: Wellcome Collection.

    167/834 (page 153)
    l.ATERITE. »ut towards the interior it becomes soft. In a well which was excavated nto it through the Trappite ridge nearly opposite Sewrec, it cut like ■heese, and so similar in consistence was the whole that, but for the resh smooth section, I could not have distinguished the angular frag- nents. In other parts, again, where it is exposed, it is loose and sandy, mt, from the presence of argil, always of sufficient consistence to keep ogether. From the protean nature of these effusions, then, it is not unlikely iihat some of them should resemble the rock called Laterite, which is so widely spread throughout the Trappean District of Western India, and such is the case. It may not be uninteresting, then, to compare the two ; but, before doing so, let us shortly review the opinions and de- scriptions that have been given respecting Laterite, and for this purpose 1 shall quote largely from Mr. Cole’s interesting paper on this rock, published in the Madras Journal of Literature and Science, vol. iv. 1836, p. 105. Characters of Laterite.—Dr. Buchanan (Gleanings of Science, May 1831), who first described and named this formation, says that “ it is full of cavities and pores, and contains a very large quantity of iron, in the form of red and yellow ochres. In the mass, while excluded from the air, it is so soft that any iron instrument readily cuts it,” but after ex- posure becomes “ as hard as brick.” He never observed any “animal or vegetable exuviae” in it, but had heard of such having “been found immersed in its substance” : it blackens externally on exposure, and is found universally overlying granite. Dr. Buchanan nowhere mentions its association with trappean rocks. But Dr. Christie (Mad. Jl. vol. iv. p. 468) states that “it is found resting in different situations, on granite, transition rocks, trap, and sandstone.” It maybe seen at Mahableshwur capping all the trappean mountains upwards of 100 feet thick, as well as I can remember, and giving them flat tops ; and I am informed by Mr. N. A. Dalzell that in the cliffs on the Malabar Coast about Rutna- gherry it may be seen even overlain by basalt. Mr. B. Babington considered Laterite to be composed of the detritus of syenitic rock, and to be alluvial, “ formed from the washings of the Ghat mountains.” He states that “ the hornblende uniformly decays into a red oxide [of iron ?], and the felspar into porcelain earth”; that it forms rounded hills below the Ghats ; and, between Tellichery and Madras, he accounts for its cellular structure by the rain washing away its white parts, and leaving the red. Dr. Voysey, who seems to have had the clearest conception on these matters of any Indian geologist with whose writings I am acquainted, made the following statement in a letter to General Cullen, dated 5th November 1820, copy of which appears in Mr. Cole’s paper :—“ The 20 y