AND TRANSPORTING AGENT—PREST, Son 
Drift Ice as an Eroding Agent. 
A great part of the erosion now acknowledged as due to 
other causes has often been ascribed to drift ice. Formerly 
great stress was placed on erosion by drift ice, particularly by 
icebergs as in opposition to drift ice. No doubt some erosion 
was actually effected, but that its traces in the form of striations 
are still retained above the sea level is very doubtful. 
In the official reports of some of the Canadian Geological 
Survey staff, and also in the writings of other geologists, we can 
trace a gradual conversion from the old theory to the new, in 
which ice-action is confined almost solely to the polishing out of 
former inequalities and striz In some of the latest reports, 
erosion by drift ice is considered possible only under exceptional 
circumstances. The cause is often proved by circumstantial 
evidence, or entered with a mark of interogation. It is also 
admitted that only where a low point or ridge is exposed to an 
ice jam forced over it by a storm, is striation possible, and then 
only when the ridge can also be reached by stones to act as 
graving tools. 
Some of the results of my observations on ice action are as 
follows: Ice action on a steeply sloping shore occurs with an 
onward rush of water carrying immense masses of ice 5 to 15 
feet in thickness. When reflex action begins the ice is poised 
for a few seconds On the rocks until the water drains partly 
away. Then, being deprived of support, it slides back with a 
tremendous plunge into the next advancing wave, dragging with 
it into deep water such rock fragments as it may have been able 
to reach. And what is very important, these rock fragments 
are never carried forward again ; for the next wave lifts the ice 
pans forward, high over every obstruction. The scoring, if any, 
in this case is done while the ice mass is sliding into the water 
with stones beneath it, as 1t exerts little downward pressure 
when rising with the rush of water. Where exposed to the 
Atlantic swell, ice pans 15 feet thick and 50 feet in diameter 
are often carried forward through a perpendicular distance of 
