Abstract
By a simple experiment the author noticed that air current has tendency to flow round any object, i. e. the greater part of the current passes the object going round on its right and left side horizontally, only a small part goes over the object. He thinks therefore that winds must blow round any solitary mountain, so that föhn action in Hann's sence can not occur with such a mountain but it may take place only when the wind blows over a mountain range. He then tried to find an actual example, by comparing the wind observed at the mountain observatory of Tukubasan with the air current at the same height in the free air observed at the Aerological Observatory at Tateno, 19km distant from the mountain. He then find a regular deviation of wind direction at Tukubasan from that in the free air above Tateno. It seems as if to prove his idea, but he cannot draw any definite conclusion owing to the want of observation round the foot of the mountain.
