574 



GEOLOGICAL REMARKS. 



and nature of the ranges^ and the direction of the shores r the 

 hills are irregularly heaped together ; the sounds are intricate and 

 tortuous in their course, and the shores are formed by deep 

 sinuosities and prominently projecting headlands: the channels, 

 also, are studded with innumerable islands and rocks extremely 

 dangerous for navigation. In this portion the rock is^ for the 

 most part, granite and greenstone. 



Near the centre of the Strait, the rock being clay-slate, the 

 mountains are higher, and more precipitous and rugged in their 

 outline ; and consequently not easily to be ascended. They are in 

 general three thousand feet, but some are found to be four thou- 

 sand feet, in height ; and one, Mount Sarmiento, is upwards of 

 six thousand feet high, and is covered throughout the year with 

 snow. The line of perpetual snow in the Strait seems to be about 

 three thousand five hundred feet above the sea : the mountains> 

 Avhose height does not exceed three thousand, are, during the 

 summer, frequently free from any, excepting in holes, where a 

 large quantity is accumulated by drifting, and protected from the 

 sun. The Strait here is quite free from islands, and it is a remark- 

 able fact, that where the greenstone formation terminates, there 

 the islands cease to appear. 



The slate formation continues as far as Freshwater Bay, where 

 the stratified rocks leave the coast and extend in a north-west 

 direction. The soil then becomes apparently a mixture of decom- 

 posed slate and clay ; the slate gradually disappearing on approach- 

 ing to Cape Negro, where the rock partakes of the character of 

 the east coast. Here again we observe, along with the change of 

 geological character, the re-appearance of islands, the soil of 

 which is clayey, but with masses of granite, hornblende rock 

 and clay slate protruding in many places through the superfi- 

 cial soil, which, although it yields a poor grass, is entirely desti- 

 tute of trees. 



In that portion of the Strait to the eastward of Cape Negro the 

 hills are remarkable for the regularity and parallelism of their 

 direction, and their general resemblance to each other. On the 

 north shore, near Cape Gregory, a range of high land commences 

 suddenly, with rather a precipitous ascent, and extends for forty 

 miles to the north-east, where it terminates in detached rocky 

 hills. The south-western end of the range is a ridge of flat- topped 



