45<3 Chonos Archipelago. paet n, 



the headlands on the opposite coast.' It would appear, 

 from Captain King's observations, that over all this 

 area the cleavage extends in the same line. Deep-water 

 channels, however, in all parts of Tierra del Fuego 

 have burst through the trammels both of stratification 

 and cleavage ; most of them may have been formed during 

 the elevation of the land by long-continued erosion, 

 but others, for instance, the Beagle Channel, which 

 stretches like a narrow canal for 120 miles obliquely 

 through the mountains, can hardly have thus originated. 



Finally, we have seen that in the extreme eastern 

 point of Tierra del Fuego, the cleavage and coast-lines 

 extend W. and E. and even WSW. and ENE. : over a 

 large area westward, the cleavage, the main range of 

 mountains, and some subordinate ranges, but not the 

 outlines of the coast, strike WKW.. and ESE. ; in the 

 central and western parts of the Strait of Magellan, the 

 stratification, the mountain-ranges, the outlines of the 

 coast, and the cleavage all strike nearly NW. and SE. 

 North of the strait, the outline of the coast, and the 

 mountains on the mainland, run nearly north and 

 south. Hence we see, at this southern point of the 

 continent, how gradually the Cordillera bend, from 

 their north and south course of so many thousand miles 

 in length, into an E. and even ENE. direction. 



West Coast, from the Southern Chonos Islands to 

 Northern Chile. — The first place at which we landed 

 north of the St. of Magellan was near Cape Tres Montes, 

 in lat. 47° S. Between this point and the northern 

 Chonos Islands, a distance of 200 miles, the ' Beagle ' 

 visited several points, and specimens were collected for 

 me from the intermediate spaces by Lieut. Stokes. 

 The predominant rock is mica-slate, with thick folia 

 of quartz, very frequently alternating with and passing 

 into a chloritic, or into a black, glossy, often striated, 



