45 8 Chiloe and Conception. part ir. 



SE. strike seemed to be the most frequent one. In 

 certain spots large quartz veins were numerous, and 

 near them the cleavage, as was the case with the folia- 

 tion of the schists in the Chonos Archipelago, became 

 extreme! v tortuous. 



At the northern end of Quinquina Island, in the 

 Bay of Concepcion, at least eight rudely parallel dikes, 

 which have been guided to a certain extent by the 

 cleavage of the slate, occur within the space of a quarter 

 of a mile. They vary much in composition, resembling 

 in many respects the dikes at Low's Harbour: the 

 greater number consist of feldspathic porphyries, some- 

 times containing grains of quartz : one, however, was 

 black and brilliant, like an augitic rock, but really 

 formed of feldspar ; others of a feldspathic nature were 

 perfectly white, with either an earthly or crystalline 

 fracture, and including grains and regular octagons of 

 quartz ; these white varieties passed into ordinary green- 

 stones. Although, both here and at Low's Harbour, 

 the nature of the rock varied considerably in the same 

 dike, yet I cannot but think that at these two places 

 and in other parts of the Chonos group, where the dikes, 

 though close to each other and running parallel, are of 

 different composition, that they must have been formed 

 at different periods. In the case of Quiriquina this is a 

 rather interesting conclusion, for these eight parallel 

 dikes cut through the metamorphic schists in a NW. 

 and SE. line, and since their injection the overlying 

 cretaceous or tertiary strata have been tilted (whilst 

 still under the sea) from a NW. by N. and SE, by 



surface was inclined, pushed a little downwards during each strong 

 vibration. In North Wales I have seen a somewhat analogous but 

 less regular appearance, though on a greater scale (< London PhiL 

 Mag.' vol. xxi. p. 184), and produced by a quite different cause, 

 namely, by the stranding of great icebergs ; this latter appearance 

 has also been observed in North America. 



