26 
GLACIAL PERIOD. 
some of our own ponds and lakes. Strange as 
it may seem to the traveller who sails under 
an Italian sky over the lovely waters of Como, 
Maggiore, and Lugano, it is, nevertheless, true, 
that these depressions were once filled by solid 
masses of ice, and that the walls built by the 
old glaciers still block their southern outlets. 
Indeed, were it not for these moraines, there 
would be comparatively few lakes either in 
Northern Italy or in Switzerland. The greater 
part of them have such a wall built across one 
end, and, hut for this masonry of the glacier, 
there would have been nothing to prevent their 
waters from flowing out into the plain at the 
breaking up of the ice-period. We should then 
have had open valleys in place of all these 
sheets of water which give such diversity and 
beauty to the scenery of Northern Italy and 
Switzerland, or, at least, the lakes would be 
much fewer and would occupy only the deeper 
depressions in the hard rocks. 
Such being the evidences of the former ex¬ 
tent of the glaciers in the plains, what do the 
mountain-summits tell us of their height and 
depth ? for here, also, they have left their 
handwriting on the wall. Every mountain- 
