506 O. A. Lehour, and W. Mundle — Coal in Chile. 



LOTA 





nothing further. In order to understand our argument rightly, it 



will be necessary 

 to examine briefly 

 the conditions un- 

 der which the de- 

 positions of the 

 present day take 

 place in the self- 

 same regions ; and 

 as we have already 

 taken the two lo- 

 calities of Coronel 

 and Lota as types 

 of the more ancient 

 sedimentary accui- 

 mulations, so shall 

 we make use of 

 them again in this 

 instance, as typical 

 of those at present 

 forming. The ac- 

 companying sketch 

 map will, it is hoped, 

 render our meaning 

 clearer. 



Fig. 4.— Sketch of part of the ChiKan Coast, 



The mouth of the Bio-Bio is, it will be seen, to the north of both 

 Coronel and Lota. The currents along the coast have a southerly 

 direction, and are of considerable strength. Now, the sediment held 

 in suspension by the Bio-Bio (of which it carries vast quantities into 

 the sea) is of a dark, almost black, colour, consisting in fact of sand 

 derived from the black volcanic rocks through which it flows, and 

 which are being continually worn down and transported by it, and 

 by the many tributaries to which it owes its size. This black sand 

 shall serve as an indicator. For observe that the shores of the two 

 bays immediately south of the Punta Coronel have different names 

 applied to them, viz., the northern one, that nearest the mouth of the 

 Bio-Bio, is called Playa-negra, and the southern one Playa-blanca : 

 that is, the black beach and the white beach. These two bays are 

 separated by a narrow ridge of rock — mica-schist — running into the 

 sea. The black beach receives the black sediment of the Bio-Bio, 

 brought to it by the current which exerts its power on that river and 

 its freight, from the moment it reaches the sea. The arrows on the 

 map show the direction of the current. After blackening the Playa- 

 negra, this current, which may be called the oceanic prolongation of 

 the Bio-Bio, is diverted from its southward course by the ridge of 

 metamorphic rock, and is driven out to sea, where it spends what is 

 left of its cargo of black sand ; and thus does it come to pass that 

 the Playa-blanca is white, and not in any degree tainter^ by the 

 black river. Here then we have two contiguous and contempo- 



