1834.] GEOLOGICAL STRUCTURES. 199 



is on account of the swampy ground, must be very hard 

 work. The Gauchos say they often pass at full speed over 

 ground which would be impassable at a slower pace ; in the 

 same manner as a man is able to skate over thin ice. When 

 hunting, the party endeavours to get as close as possible 

 to the herd without being discovered. Each man carries 

 four or five pair of the bolas ; these he throws one after the 

 other at as many cattle, which, when once entangled, are 

 left for some days, till they become a little exhausted by 

 hunger and struggling. They are then let free, and driven 

 towards a small herd of tame animals, which have been 

 brought to the spot on purpose. From their previous treat- 

 ment, being too much terrified to leave the herd, they are 

 easily driven, if their strength last out, to the settlement. 



The weather continued so very bad that we determined to 

 make a push, and try to reach the vessel before night. 

 From the quantity of rain which had fallen, the surface of 

 the whole country was swampy. I suppose my horse fell 

 at least a dozen times, and sometimes the whole six horses 

 were floundering in the mud together. All the little streams 

 are bordered by soft peat, which makes it very difficult for 

 the horses to leap them without falling. To complete our 

 discomforts we were obliged to cross the head of a creek of 

 the sea, in which the water was as high as our horses' 

 backs ; and the little waves, owing to the violence of the 

 wind, broke over us, and made us very wet and cold. Even 

 the iron-framed Gauchos professed themselves glad when 

 they reached the settlement, after our little excursion. 



The geological structure of these islands is in most respects 

 simple. The lower country consists of clay-slate and sand- 

 stone, containing fossils, very closely related to, but not 

 identical with, those found in Silurian formations of 

 Europe ; the hills are formed of white granular quartz 

 rock. The strata of the latter are frequently arched with 

 perfect symmetry, and the appearance of some of the 

 masses is in consequence most singular. Pernety* has 

 devoted several pages to the description of a Hill of Ruins, 

 the successive strata of which he has justly compared to the 

 s(;ats of an amphitheatre. The quartz rock must have been 

 quite pasty when it underwent such remarkable flexures 

 without being shattered into fragments. As the quartz 

 insensibly passes into the sandstone, it seems probable that 



• Fcrntty, Voyage aux hits Malouintt, p. 536, 



