186 E. M. KINDLE 
probably gives rise to a slight backset or eddy current to the southwest 
on the north shore of Point Hope, which may be an element in giving 
the spit its cuspate form. 
In addition to the familiar marine agents, waves, tides, and cur- 
rents, which are involved in shaping the shore-line features of all 
coasts, we have on the Arctic coasts a fourth agency which at times 
acts with far greater power and rapidity than either of the above- 
named influences. This is the Arctic ice-pack. The shallow character 
of all the navigable portion of the Arctic Ocean, north of Bering 
Strait which seldom exceeds 30 fathoms, affords peculiarly favorable 
conditions for the excavating and plowing activities of the ice-pack 
when grounded and under pressure. ‘The nature of the difference 
between ordinary sea ice and the ice of the ice-pack is indicated in 
the following extract from Captain Hooper’s ‘‘Ice Notes’’: 
The greatest thickness attained by direct freezing is about eighteen feet, at 
which thickness the increase by freezing at the bottom does not exceed the waste 
at the top by evaporation, which goes on slowly but surely at all times. The 
maximum thickness by direct freezing is generally reached the third winter. It 
is seldom that more than nine feet forms during one winter. The extraordinary 
thickness attained by the pack is due to accumulations of these naturally formed 
layers as they are forced one over the other by pressure due to currents of air and 
water. On account of the difficulties of ascertaining the thickness of the ice by 
measurement, the most reliable way appears to be by noting the depth of water 
at which it touches the bottom. This we found at Herald Island, Wrangle 
Island, and on the coast of Asia near Cape North to be about ten fathoms. In 
Bering Sea we made fast to ice grounded in six fathoms, and passed a number of 
detached pieces ground in eight fathoms.?. 
Osborn thus describes the ice encountered by McClure off the 
north coast of Alaska: 
Ice of stupendous thickness and in extensive floes, some seven or eight miles 
in extent, was seen on either hand; the surface of it is not flat, such as we see in 
Baffins Strait and the adjacent seas, but rugged with the accumulated snow, 
frost, and thaws of centuries.? 
Captain McClintock, in passing around the north coast of Alaska, 
generally found the heavy ice aground in six or eight fathoms of water, 
t Capt. C. L. Hooper, “‘ Rept. of the Cruise of the U.S. Revenue Steamer “Thos. 
Corwin’ in the Arctic Ocean, 1881,” 43th Cong. Ex. Doc., No. 204, p. 128, 1884. 
2 McClure, The Discovery of the Northwest Passage, edited by Osborn, p. 83, 
1857. 
