The principle was simply as follows. A watertight microphone was sunk about four meters down in the water of a crack in the ice. The microphone was attached by a line to an ordinary head-microphone, which the observer wore. At a distance of twenty-five to fifty meters from the observer a little charge was sunk under the surface which contained ten grams of trinol and was provided with a detonator. The charge was exploded by an electric spark. The observer set a stop-clock going when he heard the explosion, stopping it as soon as he heard the echo from the sea bottom.
On May 28th we took two soundings immediately after each other, and in both cases the stop-clock’s time proved to be five seconds. As sound travels in sea-water at the rate of 1,500 meters per second, the distance from the surface down to the bottom and up to the surface again is equal to 7,500 meters, and thus the sea’s depth is at this place half the amount, namely, 3,750 meters. The echo was quite sharp and not to be misunderstood. Therefore during a later drift, as we did not move far from the place where we had taken the first sounding, we took no more. We wished to reserve the spare charges for a possible march.
Variations
For the exact “taking of the sun” the standard compass was equipped with a special finder, in the same way, as there were water-levels on the compasses. The compass was placed in the best position, where it would be as far away as possible from every object likely to influence it. Observations were taken on the 23rd and 29th of May, with the results respectively, 39° 5′ and 30° westerly variation. This is about 5° more variation than the chart allows. These observations proved to be of great use to us when we started the homeward flight. By calculating with these variations in arranging our starting course we found we had achieved an important measure.
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I will now briefly give particulars of our further equipment.
Photographic materials and binoculars, etc., were given to us by Goerz, the cinematograph appartus was a gift from the “Hahn Aktiengesellschaft für Optik & Mechanik,” Berlin. The films and plates for the camera, also the cinema films, were given to us in generous numbers by the “Goerz Photochemische Werke,” Berlin. It is quite unnecessary to mention that all the things given to us by these firms were of first class material and everything functioned to our greatest satisfaction, giving excellent results in spite of the difficult conditions. Our snow glasses were a present from the firm, Optikus, Oslo, and were specially made for us. They could not have been better. When I count them as amongst the most important part of our outfit, I have good grounds for doing so. Any one wishing to choose glasses, and looking through the different types, will find that there is a tremendous difference between them both as regards suitability of color and other things.
There is a small detail which I should like to mention in this connection. Many flying-men will have gone through the same experience as I and realized how unpleasant it is to fly towards the sun when it is at a low altitude, for, blinded by the sharp light, it is difficult to see the instruments, and in many ways it causes a continuous strain. As a deterrent we had small aluminium screens, made in the same shape as the wind screen. These could be fixed as desired. At 10 P.M. on the northward journey the sun was so dazzling that I placed the screen in position, leaving it there until at 1 A.M. I began to look out for a landing place, when I pushed the screen back, feeling satisfied with its utility.
From the ski-factory, “Johansen and Nilsen A/S., Fin Schiander,” we received the present of the most beautiful skiing equipment that any one could wish for—skis with staves, and ski-sledges. On the old ice the snow lay so deep that without the skis we should have sunk in well over the knees. Had we to cross the water-lane to fetch provisions and petrol from N 24, we were forced in many places to cross new ice, which was in such bad condition that it would not have borne us unless we had worn skis. For transport we made use of the ski-sledges. The transport of the 200 kg. heavy petrol cans over the ice was, for the sledges, a hard test which they successfully passed. (It was with intention that we did not spare the sledges from the greatest strain during these transportations. We learned, therefore, by experience what we could safely expose them to, in the event of a possible march towards land, during which we would have to avoid all possible loss of time, caused by having suddenly to unstrap the sledges if we had to cross over icebergs.) Had the sledges been affected adversely by these tests, we had the means at hand for repairing them. It would have been much worse if they had failed us during the march. The sledges, moreover, were made with a wide surface so that the canvas boats could stand in an unfolded position, “all clear” to be put into the water-lane in the shortest possible time that necessity might demand. As the boats in this position had to be protected against jagged ice on the icebergs, we would have had to cut aluminium plates away from the flying boats’ bottoms before we left—using them as a protecting screen for the canvas boats.
The reins and harness were made by Rönne, designed in such a way that they could be placed both on the hips and on the shoulders.