The compass by this time was very sluggish, in fact the theodolite compass would scarcely work at all. This pleased us all a good deal, and at first we all wished more power to it; and then, recognising our mistake, we amended the sentiment and cordially wished less power to it.
On the evening of the 12th, Mawson, after carefully analysing the results set forth in the advance copy of the Discovery Expedition Magnetic Report, decided that, although the matter was not expressly so stated, the Magnetic Pole instead of moving easterly, as it had done in the interval between Sabine's observation in 1841 and the time of the Discovery expedition in 1902, was likely now to be travelling somewhat to the north-west.
The results of dip readings taken earlier in the journey also agreed with this decision. It would, therefore, be necessary to travel farther in that direction than we had expected, if we were to reach our goal. Most extremely disquieting news was this for us, as we had come almost to the end of our provisions, after making allowance for enough to take us back on short rations to the coast. Still, in spite of anxiety, our overwhelming weariness enabled us to get some sleep.
At breakfast on the following morning we fully discussed our future movements, and Mawson, having carefully reviewed his observations as to the position of the Magnetic Pole, decided that we must travel four more days if we were to reach it, and we resolved to go on sledging for that time.
On that day we advanced thirteen miles, and on the next the snow surface over which we were sledging sparkled with large reconstructed ice crystals, about half an inch in width and one sixteenth of an inch in thickness, which it seemed a sacrilege to break.
On the 15th about twenty minutes before true noon Mawson took magnetic observations with the dip circle and found the angle only fifteen minutes off the vertical, the dip being 89° 45'. Naturally we were very much rejoiced to find that we were close to the Magnetic Pole. The observations made by Bernacchi, during the two years of the Discovery expedition sojourn at winter quarters on Ross Island, showed that the extent of daily swing of the magnet was sometimes considerable. The compass at a distance from the Pole pointing in a slightly varying direction at different times of the day, indicates that the polar centre executes a daily round of wanderings about its mean position.
Mawson considered that we were already practically at the Magnetic Pole; and that if we waited for twenty-four hours taking constant observations at the spot we had reached, the Pole would, probably, during that time, come vertically beneath us. We decided, however, to go on to the spot where Mawson concluded the approximate mean position of the Magnetic Pole would lie. That evening the dip was 89° 48'.
From the rapid rate at which the dip had been increasing, as well as from a comparison of Bernacchi's magnetic observations, Mawson estimated that we were about 13 miles distant from the probable mean position of the South Magnetic Pole. To locate, he said, the mean position accurately it was possible that a month of continuous observation would be necessary, but that the position he indicated was as close as we could locate it.
Consequently we decided to make a forced march of 13 miles on the following day to the approximate mean position of the Pole.
On Saturday, January 16, we were up at 6 A.M. and soon started, pulling our sledge for two miles. We then depoted a lot of our heavy gear and equipment, and having gone on for another two miles we fixed up the legs of the dip circle, the compass moving in a horizontal plane being useless for keeping us on our course.