Waves of sand and snow and the eddies which make them . to leeward of an open forms of fence might ultimately collectthe same maximum quantity of snow, but the bestform would be that which collected it most quickly,and this would be ojie with, so to speak, a fine mesh. In the late autumn I have watched thedrifting of the large leaves of plane-trees inLondoji. As the leaf drifts some part of it isgenerally in contact with the ground, and althoughit is occasionally in the air its flight resemblesa jump or skip, the course of the leaf being, inthe language of golf, almost all run
Waves of sand and snow and the eddies which make them . to leeward of an open forms of fence might ultimately collectthe same maximum quantity of snow, but the bestform would be that which collected it most quickly,and this would be ojie with, so to speak, a fine mesh. In the late autumn I have watched thedrifting of the large leaves of plane-trees inLondoji. As the leaf drifts some part of it isgenerally in contact with the ground, and althoughit is occasionally in the air its flight resemblesa jump or skip, the course of the leaf being, inthe language of golf, almost all run and hardlyany flight. One day, with a southerly wind, Isaw these leaves banking up against a stone stepat one of the entrances on the south side ofKensington Gardens. The obstruction quitestopped their progress until a sufficient quantityhad collected to provide an inclined plane reach-ing the level of the top of the step. Then, as otherleaves arrived, they glided up the slope, and, slidingalong the upper surface of the stone step, invadedthe Plate 36.—Bosses of snow, in a valley of the Selkirk Range, 193 SNOW-WAVES AND SNOW-RIPPLES 195 The next observation relates to the action ofthe eddy with a vertical axis upon the driftingleaves of the plane-tree. The place was the broadpavement in front of the Imperial Institute. Thebuilding projects at the principal entrance, on thewest side of which there are two high walls facingsouth and west respectively. For some time inthe autumn I noticed every day a large circularheap of leaves of the plane-tree within this angle,the outer edge of the heap being several feet fromboth walls. As other leaves arrived, gliding overthe pavement, they circled round nearer to thewalls, but, after a time, approaching the heap, theywere either deposited against its side or were liftedand dropped more centrally upon it. The courseof events was clear. The leaves continued to traveluntil they approached the centre of the eddy, wherethe air,
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