When there was a lead we sounded from the edge of it; when there was no open water we made a hole in the ice if we could find any that was thin enough for the purpose.
Two men could readily make these deep-sea soundings by reason of the lightness of the equipment.
The distance which we traveled day by day was at first determined by dead reckoning, to be verified later by observations for latitude.

Dead reckoning was simply the compass course for direction, and for distance the mean estimate of Bartlett, Marvin, and myself as to the length of the day's march.

On board ship dead reckoning is the compass course for direction and the reading of the log for distance.

On the inland ice of Greenland my dead reckoning was the compass course, and the reading of my odometer, a wheel with a cyclometer registering apparatus.

This could not possibly be used on the ice of the polar sea, as it would be smashed to pieces in the rough going.