Chap. XIX.] 
ORIGIN OP LATEEITE. 
376 
for the present the question of the source of the energy necessary to bring 
about the decomposition of the rocks from which laterite is either 
proximately or ultimately derived, it seems to me that the truth lies in a 
combination of the various theories mentioned. In the first place, judg- 
ing from my examination of the Yeruli plateau, in the Satara district, 
I do not think that Maclaren's replacement theory can be by any means 
generally applicable. This plateau is composed of a sheet of laterite, 
which happens to be very aluminous. At the north-eastern edge of the 
most easterly of the three caps into which the 
A bauxite-conglomerate. ■. ^ , , • i 
laterite has been cut, there is a conglomerate 
bed forming the topmost layer. It is composed of pebbles of pale 
bnfiish and pinkish bauxite set in a matrix of very ferruginous 
laterite, almost entirely pisolitic. This conglomeratic layer is 
about one foot thick, and rests on a layer of solid bauxite at 
least 2 feet thick, of precisely similar character to the pebbles 
contained in the topmost layer. This bauxite bed is not continuous 
for any great distance, but passes horizontally into ferruginous 
laterite. In other parts of the plateau some of the pebbles contained in 
this conglomerate are composed of the ferruginous laterite. From this 
occurrence there seems to be no doubt that before the end of the period 
during which the laterite of Yeruli was being formed, there was a break 
in which the already-formed laterite was subjected to denudation, with 
the production of the pebbles referred to above. It is difficult to imagine 
that these pebbles were cemented into the conglomerate by the process 
cf deposition of oxides of iron brought up from below by capillary forces 
stimulated by surface evaporation ; for, if so, how could the underlying 
bauxite have escaped being impregnated with, and partly replaced by, 
iron oxide, apart from the difficulty of imagining the actual way in which 
such cementaion could have taken place ? It seems to me that the only 
The cr.ncrlonierate possible way of explaining the cementation of the 
formnd beneath water, pebbles is to suppose that it took place beneath 
.isinaia e. water, such as at the bottom of a lake. After the 
pebbles of bauxite had been formed by the action of running water, such 
as in a river valley, it is easy to imagine the formation of a lake, with 
bauxite pebbles lying on its bottom. We can suppose that the waters 
entering the lake contained salts of iron in solution derived from the sur- 
rounding ferruginous basaltic rocks, and that hydrated ferric oxide was 
precipitated in the lake, where it formed a cement for the pebbles, the 
pisolitic structure of the cement being due, either to deposition in this 
way round a nucleus, or to concretionary action. If then this ferruginous 
