TYPICAL CAMP ON THE ICE
One sounding apparatus was carried by the main division and the other by the pioneer party, in the early stages of our progress. 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. One might say in general that dead reckoning on the polar ice is the personal estimate of approximate distance, always checked and corrected from time to time by astronomical observations.
Three members of the expedition had had sufficient experience in traveling over arctic ice to enable them to estimate a day's journey very closely. These three were Bartlett, Marvin, and myself. When we checked up our dead reckoning by astronomical observations, the mean of our three estimates was found to be a satisfactory approximation to the results of the observations.
It goes without saying that mere dead reckoning, entirely unchecked by astronomical observations, would be insufficient for scientific purposes. During the earlier stages of our journey there was no sun by which to take observations. Later, when we had sunlight, we took what observations were necessary to check our dead reckonings—but no more, since I did not wish to waste the energies or strain the eyes of Marvin, Bartlett, or myself.
As a matter of fact observations were taken every five marches, as soon as it was possible to take them at all.