538 Malcolm Maclaren — The Origin of cevtain Later ites. 



feet below it can be cut with a spade. Through the manganese 

 secretions there ramify veiiilets of gibbsite — Fig. 1 (1) — much of 

 it of metasomatic replacement. It is, consequently, the last 

 deposited product. In the immediate neighbourhood of the mangani- 

 ferous laterites the writer found small areas of higli-grade pisolitic 

 bauxites. There are, therefore, in this neighbourliood all the 

 ordinary forms of laterite — ferruginous, aluminous, and mangani- 

 ferous. The last has not generally been distinguished, but it 

 cannot be dissociated genetically from the other two.^ 



The low-lying country of Goa between the coast and the Deccan 

 plateau furnishes extensive deposits of • low-level ' laterite, partly 



Hard Laterite 

 crust. 



Soft Laterite. 



Redilisli buff 

 Sandy Clay. 



White Grit. 



Decomposed 

 Biotite- 

 Quartz -schist. 



Fig. 1. — Typical Section of Laterite, Talevadi, Belgaum. 

 (1) Psilomelane with gibbsite veinlets. 



detrital and partly secretionary in origin. Examination of this area 

 elicited no further data than were collected by Lake for a similar 

 coastal region further south in Malabar.- Two main forms, the 

 vesicular and the pellety, were distinguished. The latter is often 

 partly derived from the erosion of the former, but its final con- 

 solidation and cementation is due to the same agencies that gave rise 

 to the first or vesicular form. 



The rainfall of the edge of the Western Ghats and of the Goa 

 country ranges "from 120-180 inches in the year, but falls almost 



1 See, howeA'er, Mallet, Eec. Geol. Surv. Irnlia, vol. xvi (1833), p. 117; Bose, 

 ib., vol. xxii (1889), p. 225. 



- Mem. Geol. Surv. India, vol. xxiv (1890), pt. ill, p. 17. 



