Our polar flight

by Roald Amundsen; Lincoln Ellsworth

Looking at the map, it will be discovered that the magnetic pole lies about an equal length from the geographical North Pole as from Spitzbergen. Therefore it stands to reason that the compass which can be used in Spitzbergen can therefore be used in the fairway from there to the Pole. The one thing which might cause us moments of misgiving was the magnitude of the compass’s variations in the district we wished to reach. (There is little data resulting from exact observation to give us the reason of these variations.)

During a visit to Bedford, Dietrichson and I discussed this part of the enterprise with one of my English airman friends, Captain Johnstone, and we are most grateful for the assistance he gave us. The result of the discussion was that we chose a steering compass as well as a standard compass of an up-to-date type made by the firm of Hughes & Son, London. These compasses are made to repel movement, and to bring the needle slowly back to its correct position without the slightest oscillation either to the right or left. In the Arctic Sea, where the horizontal component of the earth’s magnetism is proportionately weak, it must always take time for the needle to swing back into position as it is so strongly repelled by existing conditions. But we preferred this to one with a lengthy oscillation and a big swing backwards and forwards. Steering compasses of the above kind are eminently suitable on account of a special construction which it will take too long to describe here. The standard compass was excellent. The magnetic condition in the navigation compartment was also ideal. The deviation’s coefficiency was shown by the readings we took to be so trifling that we could consider our compasses free from deviation. Just before leaving Spitzbergen we had one of the German Ludoph-compasses sent to us, with a request for us to give it a trial. I placed it in the pilot’s compartment of N 25, where it proved itself to be an excellent compass. If the machine heeled over the dial also took a certain tilt and the vertical component of the earth’s magnetism caused considerable oscillation as the natural result of its great attraction. Whilst the Ludoph-compass oscillated somewhat, the other took some time to swing back, making it impossible for me to say which I preferred. I steered with both of them, controlling the one by the other. During the homeward flight I continually steered by the magnetic compasses, and had no difficulty so long as I could have a “Landmark” ahead. During the fog it was not such an easy matter.

A/G Gyrorector, Berlin, kindly placed at our disposal a gyroscopic apparatus for each machine—as a loan. This instrument commended itself to me and is the best I have seen hitherto for flying in fog or darkness. The rising and tilting indicator was of use to me during the whole flight. The conditions, however, were such that I did not have to make great use of the direction indicator, beyond the fact that on the northward flight I experimented with it in case we should find it necessary at some time to make a forced landing in the fog. The arrangement between the two planes was that at all costs, if we should pass through fog, not to get separated from each other. At the close of the homeward journey, as mentioned elsewhere, we flew into such thick fog that I could have made use of the direction indicator. We flew, however, so low there that the whole time I had to keep my eye glued to the ice beneath and in front of us.

We had ordered a wireless installation for N 24, but went without it as it was not ready in time. It was the only thing we went off without. We never missed it. I might mention here that we had laid down a principle not to wait at all for any belated goods.

After seeing that many different suppliers, at home as well as abroad, should despatch the goods in time to reach Tromsö, to be loaded by a certain date, I got endless notices to say the goods would be belated and that we must put off our flight some days. The answer was always the same: “We shall go without goods if they have not arrived.” The result was, except in the case of the wireless, that everything was delivered in good time. Had we once started to put off our departure we should have had constant delays.

Navigation

It will perhaps interest those readers who have a knowledge of navigation to hear a little more about Sverdrup of the “Maud’s” cleverly calculated but simple methods of navigation in the Arctic Sea. I repeat word by word Sverdrup’s own well-known description:

“One single measuring of the sun’s altitude shows that one stands on one particular spot, in a small circle whose center is the point, where at that moment the sun has reached its zenith, the radius of which is 90° h. (h. indicates the measured height of the sun). This circle shall be called a local circle.”

In order to find the meridian the sun would be in at the exact moment of observation one must read a clock, the agreement of which with Greenwich mean time (G.M.T.) is known. An almanac gives the time level to be added to, or subtracted from, G.M.T.—giving Greenwich true time (G.T.T.). The sun would then be over that meridian, the latitudinal difference of which from Greenwich is equal to the time taken for a clock to strike, according to G.T.T., and would be in its zenith over the point, the breadth of which is equal to the sun’s declination.

Taking an observation of the sun’s altitude, with a simultaneous noting of the clock’s striking, can be done most rationally by describing a tangent from a local circle in the neighborhood of the place where one believes oneself to be. Such a tangent should be called a local line. In the neighborhood of the Pole it is easy to find local lines without scientific calculations. The meridian the sun is in can be found directly one has calculated the clock’s stroke by G.T.T. The local circle cuts the meridian in the distance h—d from the Pole, where d signifies the sun’s declination. This cutting-point we will call the local circle’s Pole point. If the difference h—d is positive, this point will be on the same side of the Pole as the sun, should it be negative it will be on the opposite side. A line dropped on the meridian which the sun is in, through the local circle’s Pole point, describes a tangent from the local circle. We will call this tangent the “Pole tangent.” At a distance from the Pole point equal to 5° of latitude, the Pole point will represent the local circle with sufficient exactitude, and can be considered as a local line. But if the distance increases, the tangent’s divergence from the circle will be noticeable. Sverdrup explains how, by an easy method, one can calculate the corrections which have to be made, should one find oneself within the above-mentioned limits from the Pole. During our observations in the ice region we were always within the limit, and had therefore no need for corrections. The method is of course particularly simple and sufficiently exact because there is so little difference between the hour-angle and azimuth. I here give a table of our observations on the night of the 22nd immediately after landing: