Most persons imagine that the ice of the arctic regions has been formed by direct freezing of the sea water; but in the summer time very little of the floating ice is of that character.

It is composed of huge sheets broken off from the glacial fringe of North Grant Land broken up by contact with other floes and with the land, and driven south under the impetus of the violent flood tides.

It is not unusual to see there ice between eighty and one hundred feet thick.

As seven-eighths of these heavy floes are under water, one does not realize how thick they are until one sees where a huge mass, by the pressure of the pack behind it, has been driven upon the shore, and stands there high and dry, eighty or a hundred feet above the water, like a silver castle guarding the shore of this exaggerated and ice-clogged Rhine.
The navigation of the narrow and ice-encumbered channels between Etah and Cape Sheridan was long considered an utter impossibility, and only four ships besides the _Roosevelt_ have succeeded in accomplishing any considerable portion of it.

Of these four ships, one, the _Polaris_, was lost.