Chap. XIX.] 
ORIGIN OF LATERITE. 
Zl1 
The composition of the fresh rock is, of course, unknown ; but it can- 
not have been very different from that of a basalt (or andesite^). From 
the analyses of andesites and basalts given on pages 250, 251, 253, and 
259 of Cole's * Aids to Practical Geology ', 1898, I have extracted the 
following figures for the limits of composition of these rocks : — 
' 1 
Andesites. 
Basalts. 
Si02 . , 
56-2— 690 
44-2— 540 J 
Ti02 ....... 
0-8 
1-5— 31 M/l 
AI2O3 = . . , 
14-3_16-9 
90— 18-5 1 
Fe203 + FeO . ... 
3-7— 15-2 
11-6— 15-4 ■ 
MnO „ . , . . 
trace — 0"5 
0-3 
CaO 
3-2— 70 
8-6— 10-4 
MgO 
0-8— 4-8 
3-8— 101 
K2O 
0-9— 2-9 
0-7— 2-2 
Na20 
2-5— 50 
11— 2-5 
H2O 
0-3— 11 
1-3— 2-5 
Three specimens of the Yeruli bauxite, taken by the late Mr. L. C. H. 
Yoimg (by whom I was accompanied on my visit to this locality) as 
dupUcates of specirnens collected by me, were analysed by Messrs. J. 
1 I have considered the possibility of the rock being an atidesite, because there are 
some ash-like layers in the traps of this region. Theircomposition has not been investi- 
gated, but they may be as acid as andesites ; and if so, it is possible, though not verv 
probable, that some of the earthy amygdaloidal beds, also, were, when fresh, andesites 
rather than basalts. 
