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raised beaches the sea (when the beaches were deposited) 
covered and protected the glaciated rocks. ‘The sea was then 
twenty to thirty feet higherthan now. Around the sea-lochs of 
the western Highlands and Sutherland, and likewise on the east 
coast, glaciers came down to the sea-level (when it was twenty 
to thirty feet higher than now) in Neolithic times. ‘The epoch 
of the latest glaciers in Scotland was separated from the last 
great glacial period by the oldest submarine forests, and the 
buried trees at the bottom of peat-bogs. Then the land went 
partially down, and the latest (now) raised beach was depo- 
sited. Glaciers again appeared in the mountain valleys and 
came down to the sea-level. Neolithic man was then living, 
since we find his canoes lying at the bottom of the Carse 
clays, associated with the trees of the submarine forests. To 
this statement of Professor James Geikie’s discoveries, I may 
add that Mr. Kinahan has found traces of the continuance of 
local glaciers in Ireland as late as the time when the 300 feet 
and 100 feet raised beaches were formed. 
3. Limited Depth of Post-glacial Stream-channels. — In 
many parts of Wales, Cumberland, and elsewhere, on the 
sides of valleys (such as Nant Francon), gorges, from a few 
feet to at least nine or ten fect in depth, have been ploughed 
out, by what is locally called the “bursting of a thunder- 
cloud,” in less than an hour, while pre-existing channels of 
streams have, to a great extent, been enlarged. But in many 
places, where post-glacial channels have been excavated by 
the ordinary action of streams, they have not reached a depth 
of more than a few feet, and that even in loose drift, or in 
soft and incoherent rocks. I could mention numerous in- 
stances in many parts of North Wales and Cumberland, but a 
few may suffice, namely, stream-channels around Llyn Ogwen; 
in Llanberis Pass; on some of the slopes of Snowdon; above 
the Penrhyn slate quarries; some of the brooks around 
Llangollen; on the east side of Minera mountain (west of 
Rhosllanerchrugog), where several rapidly-flowing streams 
have excavated channels in glacio-marine drift only a few feet 
in depth ; in Cwm Llafar (under Carnedd Dafydd), where a 
foaming brook has made wonderfully little impression on the 
bottom of a narrow valley which, according to Ramsay, was 
scooped out by one of the later glaciers; in many of the © 
Cumberland valleys, &c. The very fact that many of the 
post-glacial stream-channels of Wales and Cumberland are 
sufficiently shallow to admit of being crossed by cart and 
carriage roads, without bridges, is a striking proof of the 
trifling extent to which post-glacial streams have deepened their 
