8 KOTO : NOTES ON THE GEOLOGY 



thin superficial covering of ferruginous loam wliicli is in part 

 at least the product of decay of Recent epoch, thongh a certain 

 portion may have been defladed away and lost during dust-storms. 

 Along the shore free from escarpment, white sandy beaches 

 stretch from one point to another. Tliey are the Alluvial cleposiis, 

 into whose composition enters a special element which we are not 

 accustomed to see in our own coast. Xearly all round the island, 

 coral reefs grow npon the Basaltic shelf, and the detritns derived 

 from them is driven up to form low sand dunes, leaving behind 

 them, if the coast-line is deeply indented, as it is in many 

 places, muddy shallows filled with the residual clay of decomposed 

 Basalt. 



Such is the general outline of the geology of the Island, 

 and of the rest of the group as well. 



Looking more into the details, we find that at Bako'^ 

 Point, on which is situated the town of the same name, the second 

 flow extends in a great sheet, covering all but a few points of eleva- 

 tion which are capped with there lies of the young columnar lava, 

 being separated from it by a blue rock. The last is a fuller s 

 earth, which is a bluish-grey, dull, compact mass of greasy 

 lustre, splitting, when dry, into angular clods with sub-conchoidal 

 fracture. It adheres to the tongue, and falls readily to a muddy 

 state on placing in water, and is not plastic. Under the micro- 

 scope, the whole mass consists of brownish, double- refracting 

 particles, and seems to have been derived from the decomposition 

 of a Basaltic glass. It crops out for a short distance, and on shore 

 a poor bed of Tertiary lignite occurs associated with it. 



