AND TRANSPORTING AGENT—PREST. 339 
To one class belong the scratches caused by the expansion of 
harbor ice holding large stones which are pushed up from shoal 
water. These are most prominent in the best protected positions, 
where it appears impossible for glaciers or drift ice to act. 
The other class of marine striz is formed by large boulders 
lying usually at high watermark, and which have been rolled 
down from frost-shattered cliffs near by. They are pushed back 
by ice jams or by ice hurled against them in a scorm, and move 
a foot or a few inches at atime. These striv are partly pro- 
tected from obliteration by the boulder itself. 
In regard to the question of erosion by icebergs, the first 
point to be considered is whether bergs carry stones in positions 
suitable for eroding. 
Observers in the far north, as well as those who have exam- 
ined glaciers in more temperate latitudes, maintain that debris 
falls into cracks, or is lodged on the surface of those ice masses 
and are then carried to sea when the bergs are detached. But 
it is plain that stones attached to the sides and bottoms would 
melt off during their long voyage, and this contention is sup- 
ported by much negative evidence. Although I saw many 
overturned bergs F saw no stones attached. I therefore feel 
compelled to fall back on the theory that bergs striate the sea 
bottom only by bringing their great weight to bear on loose 
rocks, Should such strizw have been formed before the old shore 
lines were raised to their present positions, they could not 
possibly have emerged above the polishing influence of the field 
ice. Being formed only in the positions afterward exposed to 
the wear of pan ice, I am thoroughly convinced that such a 
phenomenon asstriz by ice-bergs does not exist above the sea level, 
A rising coast as in Labrador, exposes a well worn rock 
bottom, smoothed by ice action during the preceding subsidence ; 
and in an exposed position all protecting debris is speedily 
washed into deep water, and all signs of berg erosion obliterated. 
A sinking coast carries its strize with it, if such striz can be 
retained long enough to get below the intense ice action seen in 
Labrador. 
Proc. & TRANS. N. S. Instr. Sci., Vou. XI. TRANS. X. 
