GIG HA AND CARA. GEOLOGY. 279 



of their mineral characters. The general direction of 

 these edges is north-east somewhat northerly, and their 

 dip north-westerly ; the angle of inclination to the horizon 

 being generally about twenty degrees, but reaching in 

 some cases to forty and upwards. In these respects it 

 will be seen that the strata conform more or less accu- 

 rately in direction to those of all the schistose islands 

 which have already been described, though differing from 

 the whole of them in the dip. 



From the frequent alternations that here take place 

 among the different rocks, it is impossible to assign the 

 lowest place to any. This indeed is the general character 

 of the whole -series wherever it occurs. It may only be 

 remarked, that quartz rock alternating with micaceous 

 schist prevails on the eastern quarter, and chlorite schist 

 on the western ; and that, as far as the island alone is 

 concerned, the former is therefore the lowest, and the 

 latter the uppermost in place. But in the intermediate 

 space, these three rocks are also found alternating, with 

 the further addition of the various hornblende schists ; 

 the quartz rock however in a very minute degree only, the 

 chlorite schist in extensive beds. This latter rock indeed, 

 under various modifications, seems to form the principal part 

 of the island ; hornblende schist under different aspects 

 constituting the chief part of the remainder. In a manner 

 equally general it may be remarked, that the hornblende 

 rocks are inferior in position to the chloritic, and that 

 they follow the micaceous schist and quartz rock . but 

 they are also found alternating with the former, and even 

 constituting with them several ambiguous and unnamed 

 mixtures. It would be an useless task to describe the 

 order of these alternations further, since they seem abun- 

 dantly inconstant, and perhaps not even very continuous 

 according to the course of any given stratum. 



With respect to the mineral composition of these rocks, 

 it will be sufficient to enumerate the most conspicuous 

 strata, since these, however varied, are still necessarily 



