438 
the prosecution of further observations. I shall therefore 
briefly sum up those leading features which have reference to 
a practical result, and which are founded upon the phenomena 
which I have had an opportunity of observing. 
Among the appearances which most strongly attest the 
former existence of glacial action, are — 
The rounded form of j'ocks. — This I have seen in various 
parts of Wales to an extent of which I had no previous con- 
ception. In the vicinity of Llyn Ogwin, on the south side 
of the lakes of Llanberris, and near the mountain of Drws y 
Coed, the most prominent examples occur of rocks rounded 
into forms precisely similar to those delineated in the plates 
of Agassiz's work. AYhen once the eye has become familiar- 
ised with these forms, it is difficult to resist the conclusion, 
that they are of similar origin, and the form of many of them 
is such as one can with difficulty comprehend to have been 
caused by water, especially ^one of which I made a drawing 
on the margin of Llyn y Gader, near Drws y Coed, but 
which it is easy to comprehend might be ground into this 
form by the pressure of enormous masses of ice. 
The polished condition of rocks. — This occurs both on 
rounded rocks and on nearly level beds ; it is evidenced in 
exposed rocks, where the surface is weather-worn, by the 
smoothness of projecting veins of quartz, and the carboni- 
ferous limestone at Langley presents a highly polished 
surface. This condition is exactly similar to the polish on 
specimens of Swiss rocks worn by glaciers. 
jVIany of the rocks in North Wales present a furrowed or 
undulating surface, the curves of which are alternately con- 
cave and convex, and several feet in length. This feature is 
one which might possibly be caused by diluvial torrents, in 
which large quantities of gravel were contained ; and it must 
be borne in mind, that it is of importance not too hastily to 
ascribe to srlaciers what may in reality be due to the power 
