of the Scratched Rock Surfaces. 15 
different sets of scratches, lying across one another, might 
sometimes be produced. 
In our larger valleys we find masses of debris, stones, 
and sand, lying like long terraces along the one or the 
other side, sometimes along both. These are side moraines. 
Further down, nearer the mouth of the valleys, and also 
higher up, more among the mountains themselves, the same 
masses—banks of boulder-clay—te right across the valleys. 
These are terminal moraines, left where the glaciers pushed 
out in the lower districts towards the coast, or higher up 
among the mountains, as the last glaciers shrunk and re- 
treated. 
The glaciation ceased by a gradual melting and disap- 
pearance of the ice. During this perhaps protracted period, 
the mud-laden glacier rivers were bearing down with them 
the detritus with which they were charged, depositing it in 
the sea or in inland lakes, wherever the water was suffi- 
ciently still to allow it to sink. Hence our marine and lake 
clays. Running water, too, acted on the moraines, washing 
out the sand from these masses of debris, and spreading it 
around and over them. MHence the stratified upper part of 
the banks and the sand spread far out over the clay around 
the old banks. 
On the coast, where the sea received the matter thus 
brought down, shell-fish made their appearance, partly 
buried in the clay, partly in the form of entire beds. These 
beds are found up to a height of 500 feet. To this extent, 
therefore, the land must have stood at a lower elevation. 
Let us now see in what order this glacial matter has been 
sorted and heaped up by the sea :— 
At the bottom of all we find, except where they have 
been afterwards swept away, sand and rolled stones. These 
were the scratching agents. It was they which were 
dragged by the ice across the rock faces ; and if we are to de- 
duce from the blocks the direction of the friction, it is these 
blocks we must examine; but as they are most frequently 
broken, reduced in size, and often rounded, they are gene- 
rally called not blocks but rolled stones, though the name is 
not strictly correct, and they should rather be called ‘‘ scour- 
ing stones.” They have not been rolled, but have mutually 
