456 WORST JOURNEY IN THE WORLD 



during summer temperatures on the Barrier the surface is 

 fairly good, that between + 5 and + 1 5 less good, and 

 between + I5°and + 25 best. The worst is from + 2 5 up- 

 wards, the worst of all being round about freezing point. 



As the temperature became high the amount of ice 

 melted by this sliding friction was excessive. It was then 

 that we found ice forming upon the runners, often in 

 almost microscopic amounts, but nevertheless causing the 

 sledges to drag seriously. Thus on the Beardmore we took 

 enormous care to keep our runners free from ice, by scrap- 

 ing them at every halt with the back of our knives. This 

 ice is perhaps formed when the runners sink into the snow 

 to an unusual depth, at which the temperature of the snow 

 is sufficiently low to freeze the water previously formed by 

 friction or radiation from the sun on to a dark runner. 



In very low temperatures the snow crystals become 

 very small and very hard, so hard that they will scratch the 

 runners. The friction set up by runners in such tempera- 

 tures may be known as rolling friction, and the effect, as 

 experienced by us during the Winter Journey and else- 

 where, is much like pulling a sledge over sand. This roll- 

 ing friction is that of snow crystal against snow crystal. 



If the barometer is rising you get flat crystals on the ice, 

 if it is falling you get mirage and a blizzard. When you 

 get mirage the air is actually coming out of the Barrier. 

 Thus far Wright's lecture. 



Since we returned I have had a talk with Nansen about 

 the sledge-runners which he recommends to the future ex- 

 plorer. The ideal sledge-runner combines lightness and 

 strength. He tells me that he would always have metal 

 runners in high temperatures in which they will run better 

 than wood. In cold temperatures wood is necessary. Metal 

 is stronger than wood with same weight. He has never 

 used, but he suggests the possible use of, aluminium or 

 magnesium for the metal. And he would also have wooden 

 runners with metal runners attached, to be used alternately, 

 if needed. 



The Discovery Expedition used German silver, and 

 it failed : Nansen suggests that the failure was due to the 



