196 FALKLAND ISLANDS. [chap. ix. 



treatment, 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 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* 

 has devoted several pages to the description of a Hill of Euins, 

 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 havino: been heated to such a deo-ree that it 

 became viscid, and upon cooling 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 an- 

 gular 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 



* Peruety, Voyage aux Isles Malouines, p. 526. 



