9. Studies on Lake-Ice

First, the change in length with temperature of ice frozen on Lake Suwa was measured with an apparatus, which consisted of a tube of fused silica and a recording drum. The end of the tube, 1m long, was fixed to a stand that rested on the ice surface, and the displacement of the other end owing to expansion or contraction of the ice recorded. Comparing the daily change in the length of ice with that of the air temperature recorded simultaneously, the linear expansion coefficient of the lake-ice was found to be 0.51.10^. Availing ourselves of the data regarding ice and air temperature thus obtained, the mechanism of growth of the ice-ramparts that formed on Lake Haruna in 1942 was discussed. Next, the velocity of elastic waves caused in lake-ice at Lake Haruna by setting off detonators was recorded with the aid of geophones. The velocities of longitudinal and transverse waves obtained were 2・8 and 1・5km/s respectively, and dispersion curves of waves of long period which succeeded the foregoing waves were drawn