412 GEOLOGY OF THE SECOND DISTRICT. 
We liave, both here and elsewhere, three phenomena related in kind to each other; but 
whether they are related as to cause, cannot at this stage of our inquiries be determined. I 
refer to the scorings or scratches upon rocks, the distribution of boulders, and the wearing of 
rocks in the mode represented by the cut at the head of this section. As some of my readers 
may be unacquainted with the appearance of a rock which is scratched or scored, I have in¬ 
troduced a cut which exhibits, as well as possible, these peculiar markings. I have borrowed 
it from my colleague Mr. Vanuxem, who procured it for the purpose of showing the tremulous 
motion of boulders when passing over the surface, which is indicated by the regular inter¬ 
rupted lines. 
] 16 . 
In all the effects specified above, water is concerned, but in each case the circumstances 
are modified. In the first, water bears along rocks and stones, gravel and sand, frozen into 
cakes of ice; in the second, boulders are frozen probably in large masses of ice, termed ice- 
jloes or icebergs, which, floating out to sea, melt gradually away, and drop them as it may 
happen, or as they are thawed out. Now these icebergs float in directions quite constant, and 
hence may ground regularly upon the sounding of certain shbres, where the greater part of 
their burden of rocks is dropped. By this hypothesis, I would explain the collection of 
boulders in certain zones or belts. The third or last phenomenon has nothing to do with ice : 
