74 Cruise of the '''"Alert.'''* 



This then was the end of what is now known as the Picton 

 Channel, and bold would be the mariner who would attempt to 

 traverse it, and thread his way through such a maze of reefs and 

 breakers. Among the islets at this, its northern extremity, we 

 found an anchorage, where we decided on stopping for the night. 

 As we cast anchor, a native boat approached, carrying no less 

 than twenty-three inmates, most of whom were males, and of a 

 most savage and treacherous appearance. They had with them 

 several young fur seals, recently killed, which they were glad to 

 barter for tobacco or biscuit. After stopping alongside for about 

 half-an-hour, they paddled away and were seen no more. On the 

 following day we steamed back. 



The rocky shores and islets of the Trinidad Channel bear 

 abundant indications of old ice action. These marks are not 

 very apparent on the coarse-grained friable syenite which is the 

 common rock of the district, but on the dikes of hard green- 

 stone, with which the syenite is frequently intersected, scorings 

 and striations of typical character may be seen. Close to the 

 anchorage in Port Charrua, on the north side of the channel, 

 there is a broad band of greenstone on which I observed very 

 perfect examples of " crosshatchings," where the prevailing east 

 to west striae were intersected by those of another system at 

 an angle of about 40°. These rock erosions, coupled with 

 what we know from the sounding-lead as to the contour of 

 the sea-bottom, lead us to infer that the Trinidad Channel 

 was at some remote period the bed of a huge glacier, which 

 flowed westward from the Cordillera. That most, indeed, of 

 the other straits and channels of Western Patagonia were also 

 at one time occupied by glaciers is clearly testified by the 

 markings on the rocks. 



There is a peculiar form of syenite rock not uncommon in 

 exposed situations on the hilltops, which is composed of quartz, 

 felspar, and hornblende, the quartz occurring in crystals of 

 about the size of large peas. ' The felspar, being of a very 



