THE VOYAGE OF THE BEAGLE 211 



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 sandstone, containing fossils, Very closely related to, but 

 not identical with, those found in the 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 8 has devoted 

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

 successive strata of which he has justly compared to the 

 seats 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 

 the former owes its origin to the sandstone having been 

 heated to such a degree that it became viscid, and upon cool- 

 ing crystallized. While in the soft state it must have been 

 pushed up through the overlying beds. 



In many parts of the island the bottoms of the valleys are 

 covered in an extraordinary manner by myriads of great 

 loose angular fragments of the quartz rock, forming " streams 

 Of stones." These have been mentioned with surprise by 

 every voyager since the time of Pernety. The blocks are 

 not waterworn, their angles being only a little blunted ; they 

 vary in size from one or two feet in diameter to ten, or even 

 more than twenty times as much. They are not thrown 

 together into irregular piles, but are spread out into level 

 sheets or great streams. It is not possible to ascertain their 

 thickness, but the water of small streamlets can be heard 

 trickling through the stones many feet below the surface. 

 The actual depth is probably great, because the creviees 

 between the lower fragments must long ago have been filled 



8 Pernety, Voyage aux Isles Malouines, p. 526. 



