290 NOTE ON THE LATERITE OF OEISSA. 



gravity, would have been separated from that richer in iron, and would 

 have been carried away to a greater distance; but the Lithomarge 

 beneath might be expected to be of nearly uniform constitution through- 

 out : or, at all events, its richness would be independent of its depth 

 below the surface. 



Assuming the third, we shall certainly find a much larger quantity 

 of iron in the laterite than in the lithomarge, and whilst, in the 

 first named rock, the quantity will be uniform throughout, or dim- 

 inished very slightly from the surface, in the latter it will decrease 

 in quantity rapidly and regularly with the depth, as far as the water 

 level of the country. Below that level it may probably remaiu uniform. 



It has unfortunately only in one instance been found possible to 



How it has been found "^^^'"^ specimens of these rocks, at regidar in- 

 to be distributed. tervals from the surface downwards to a consider- 

 able depth. The result therefore must be looked upon as imperfect 

 until confirmed by fresh experiments. So far as they go, however, they 

 completely coincide with the last proposed hypothesis, that of the 

 laterite being the source of the iron. 



The locality whence the specimens were obtained was a well and 

 boring near Daltola.* The section there exposed was — 



■WELL. 



Laterite, 6 feet. 



Lithomarge passing downwards into white and yellow clay, 20 „ 



Water level at 26 „ 



BORING. 



White clay' passing downwards into decomposed gneiss, ... 44i „ 



70i „ 



* See note, ante, p. 284. 



