392 Charles Davison—Stone-Rivers, Falkland Islands. 
and Dr. Coppinger with, I believe, conclusive force. With regard 
to the sixth, though slight movements of this nature must undouht- 
edly be taking place, they must in this case be unusually small, 
for the climate of the Falkland Islands is dull and the sky almost 
continually overcast. 
Now, in all of the above-mentioned theories, the transport of the 
quartzite blocks over considerable distances is taken for granted, and 
the object of the theories is really to account for this transport over 
a rough and irregular surface, inclined generally at a very small 
angle to the horizon. But is it not possible that this assumption is 
unnecessary ; that the blocks, though they have doubtless undergone 
some movement, still remain in the immediate neighbourhood of the 
places they occupied before the valleys were formed; that the stone- 
rivers are, in fact, but an extreme case of the inability of a stream 
to remove the debris in its course ? 
On the summits of many of our mountains, we have a phenomenon 
not unlike the stone-rivers in appearance, and perhaps similar to 
them in origin. The so-called “blocky structure,” so conspicuous, 
for example, on Scawfell Pike, occurs in many, if not in most, cases 
where alternate bands of hard and soft rock crop out at the summit. 
The softer layers, being more easily weathered, are gradually 
removed by wind and rain; and, in course of time, the joint-formed 
blocks of the harder projecting bands fall over in various directions, 
giving rise to that confused, tumultuous appearance, which seems at 
first sight to suggest the action of an overwhelming force. The 
blocks remain almost as they fall, for the forces in action on the 
mountain-summits are insufficient to displace them greatly. 
Now, in the Falkland Islands, we have, as we have seen, some- 
what similar conditions; bands of hard quartzite separated by seams 
of soft and crumbling sandstone. When streams began to flow over 
the primitive surface of the country, they bore away, I imagine, the 
loosened debris of the softer bands, but the resulting blocks of 
quartzite were too heavy to be moved by them and hard enough to 
resist atmospheric disintegration. The streams then flowed between 
and below the blocks, and continued to remove the softer bands 
beneath, working their way from side to side of the valleys. The 
quartzite blocks thus gradually subsided vertically all over the 
valleys, most along the axis and in the lower regions, least at the 
sides and in the upper parts, forming on the whole a gently sloping 
surface,” but rough and irregular in its details owing to the different 
1 «The temperature is very equable, the average of the two midsummer months 
being about 47° Fahr., and that of the two winter months 37° Fahr. ‘The sky is 
almost constantly overcast, and rain falls, mostly in a drizzle and in frequent showers, 
on about 250 days in the year. The rainfall is not great, only about 20 inches.” 
Enc. Brit., art. on the Falkland Islands. 
* It should be noted that the quartzite bands are often much crumpled and 
distorted, but the surface of the stone-rivers would be fairly smooth in any part, 
if the total thickness of the quartzite bands formerly above that part were approximately 
the same all over it. Sir Wyville Thomson states, however, that ‘the general 
colouring [of the islands] is dark brownish-green, relieved along the strike of the 
hills by veins of white quartzite denuded by the wearing away of softer rocks on both 
sides, and left projecting on the mountain-slopes like dilapidated stone dykes” 
(Ene. Brit.). 
