GLEN ROY, IN SCOTLAND. 
37 
it must have been held in the moving mass. 
No currents or sudden freshets carrying hard 
materials with them, even moving along straight 
paths down hillsides or mountain-slopes, have 
ever been known to draw any such lines. 
They could be made only by some instrument 
held fast as in a vice by the moving power. 
Something of the kind is occasionally produced 
by the drag of a wheel grating over rocks 
covered with loose materials. 
It has been said that grounded ice or ice¬ 
bergs floating along a rocky shore might pro¬ 
duce similar marks; but they will chiefly 
be at the level of high-water mark, and, if 
grounded, they will trend in various direc¬ 
tions, owing to the rocking or rotating move¬ 
ment of the iceberg. It has also been urged, 
that, without admitting any general glacier- 
period, icebergs and floating ice from more 
northern latitudes might account for the ex¬ 
tensive transportation of the loose materials 
scattered in a continuous sheet over a large 
portion of the globe. There can he no doubt 
that debris of all sorts are carried to great 
distances by floating ice ; where their presence 
is due to this cause, however, they are every- 
