196 FALKLAND ISLANDS. [cHae. 1X. 
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 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 cooling crystallized. While in the soft 
Ae it must have been pushed up through the overlying 
eds. 
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 
* Pernety, Voyage aux Isles Malouines, p. 526. 
