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or courses of the rivers, and, were the connecting gorges 
through which the rivers escape to be blocked up, as they 
apparently once were, the valleys would be occupied by lakes. 
The rivers, in order to find their way to the sea, have 
repeatedly to change their course, and, were it not for the 
existence of outlet gorges, they would be unable to reach the 
eea at all. The rivers in pre-glacial times, as they flowed 
over the barriers of lakes, may have excavated some of these 
connecting gorges in hard rocks, as rivers in post-glacial 
times have forced their way out of lake-basins in drift by 
scooping out channels; but there are many instances in 
which the outlet gorges could not have been excavated by 
rivers, especially those where the levels of the lakes could 
not have reached, or nearly reached, the height of the barrier. 
This remark applies to the Don and the Went, which, after 
flowing along valley- expansions, make their escape through 
narrow gorges in the Permian Escarpment. There is reason 
to believe that the gorge at Went Bridge was first opened 
by one or more fractures or faults. This may have occurred 
under the sea, in which case currents may have cleared out 
and enlarged the gorge. But in whichever way the gorge 
of the Went was formed, it presents clear indications of 
having been subjected to the action of the sea during the 
last submergence of the land. These indications consist 
principally of a peculiar style of honeycombing which shows 
that the cavities must have been regularly ground out by a 
forcible agency, such as that of sea waves charged with sand 
or other solid abrading matter. We may see the difierence 
between these pits and cavities and those now eaten out by 
atmospheric agency in an old quarry near the lower end of 
the gorge. The latter are invariably rough, and conform 
precisely to the unequal composition of the rock. 
