Page:The Worst Journey in the World volume 2.djvu/210

Rh fact that these runners were fitted at home. The effect of this is that the wood shrinks and the German silver is not quite flat: the fitting should be done on the spot. Nansen did this himself on the Fram, and the result was excellent. [I believe that these Discovery runners were not a continuous strip of metal but were built up in strips, which tore at the points of junction.] Before it is fitted, German silver should be heated red hot and allowed to cool. This makes it more ductile, like lead, and therefore less springy: the metal should be as thin as possible.

As runners melt the crystals and so run on water, metal is unsuitable for cold snow. For low temperatures, therefore, Nansen would have wooden runners under the metal, the metal being taken off when cold conditions obtained. He would choose such wood as is the best conductor of heat. He tried birch wood in the first crossing of Greenland, but would not recommend it as being too easily broken. In the use of oak, ash, maple, and doubtless also hickory, for runners, the rings of growth of the tree should be as far apart as possible: that is to say, they should be fast growing. Ash with narrow rings breaks. There is ash and ash: American ash is no good for this purpose; some Norwegian ash is useful, and some not. Our own sledges with ash runners varied enormously. The runners of a sledge should curve slightly, the centre being nearest to the snow. The runners of ski should curve also slightly, in this case upwards in the centre, i.e. from the snow. This is done by the way the wood is cut. Wood always dries with the curve from the heart towards the outside of the tree.

During our last year we had six new Norwegian sledges twelve feet long, brought down by the ship, with tapered runners of hickory which were 3¾ inches broad in the fore part and 2¼ inches only at the stern. I believe that this was an idea of Scott, who considered that the broad runner in front would press down a path for the tapered part which followed, the total area of friction being much less. We took one of them into South Bay one morning and tried it against an ordinary sledge, putting 490 lbs. on each of them. The surface included fairly soft as well as harder and more