of the Scratched Rock Surfaces. 5 
The boulders which we usually call erratic—great, generally 
sharp-cornered blocks which easily catch the eye—have 
doubtless been moved, but not always by the same “stream” 
which seratched. There is here a confounding of quite dif- 
ferent things. These blocks in the lower districts lie on 
the top of the boulder-clay banks. How could it, then, be 
they that scratched the rocks. But it is precisely the erra- 
tic rocks which most catch the eye, lying as they do on the 
surface, large in size, sharp at their edges, and easily re- 
cognised. On the other hand who has ever broken his 
hammer on the true ‘scratchers,—the stones great and 
small—crushed, rubbed, rounded, and broken—that lie at the 
bottom of the boulder-clay banks,—these heaps of debris 
which rest immediately on the rock ? 
Things are somewhat different in the higher districts. 
There one may, indeed, more safely draw inferences from 
the erratic blocks; but there, what with the vastness of the 
field and the fewness of the observers, we know too little of 
the minute lithology to entitle us to assert that any particular 
foreign block we may meet can only have proceeded from 
one special bed. If we could do this, we could indeed 
determine the direction of the moving power; but this we 
cannot do. Further, the blocks have been moved in various 
ways, and they cannot therefore be depended on for indi- 
cating how the arrows showing direction of motion should 
be laid down in the maps. 
2. There has been too much of rash talking about lee and 
weather sides. In some cases such phenomena really exist ; 
but such cases are rare; and generally the gentle slope on one 
side, and the steep break on the other, which have been de- 
scribed as stances of lee and weather sides, arise simply from 
the constitution and position of the rock itself. The moun- 
tains of Eggedal, for instance, all seem to show fine examples 
of a weather side towards the north, and a lee side towards the 
south, but this arises merely from the he of the schist strata 
which dip tothe north. Similarly, the porphyry hillocks in 
Asker and Barum seem to have weather sides to the north 
and lee sides to the south; but the cause of this is, that the 
porphyry beds dip north conformably with the underlying 
sandstone. When we are told, therefore, that the observer 
