A study of slope development was undertaken on the cliffs of datable gravel river terraces in part of the Tokachi Plain of Hokkaido Island. The ages of the river terraces were estimated mainly by C-14 dating of overlying tephras with pumice-fall marker beds, and also by the sequence of terrace development relative to eustatic sea-level change. All the sampled slopes in unconsolidated gravels faced South but they differed in height and in the period of time since they had been abandoned by lateral river erosion. Twenty-nine slopes were measured, representing six different periods of time:<1, 2, 4, 6, and 10±10⁴ years. They all show smoothed profiles consisting of three segments : an upper convexity, a straight segment and a basal concavity. Several indices of the slope characteristics of each profile were calculated and relations among them were shown graghically with the following results:
1. The percentage of the upper convex segment increases only slightly with time. The percentage of the straight segment varies inversely as that of the basal cocave segment.
2. The maximum slope of the straight segment of higher cliff's is independent of cliff height. It decreases with time rapidly at first, slowing down progressively. The maximum slope of lower cliffs varies with the height of the cliff, and also decreases with time. In the latter case, the upper covexity joins directly to the basal concavity formed mainly by deposition. Even in the former case, lateral river erosion would be indispensable to maintain a constant slope of the straight segment through time. In numerical terms, the maximum slope of cliffs higher than 30 metres is about 45° in the period shorter than 1±10⁴ years and decreases to 30° by 6±10⁴ years. The maximum slope of cliffs 20 meteres high diminishes from 40° to 27°, 22°, and 18° for ages of<1, 2, 4, and 6±10⁴ years respectively whilst, for the same ages, the maximum slope of cliffs 10 metres high diminishes from 35° to 20°, 11°, and 10°.
3. The upper convexity is independent of cliff height, but is dependent on the maximum slope of the straight segment. The upper convexity of slopes younger than 1±10⁴ years is very strong and sharp, but that of all slopes older than 2±10⁴ years is weak and smooth. Since the upper convex segment is covered with undisturbed Holocene tephra layers, it is inferred that it is a fossil feature, probably formed under the periglacial climate of the last glacial period, and due to soil creep rather than slope wash.
4. Process on the straight segment is not so affected by climatic change as is on the convex segment. The slope of the straight segment has decreased continuously in recent 10±10⁴ years.

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The author analysed the results of previous studies and her own investigations on the prevailing wind direction estimated by wind-shaped trees (Abies Mariesii, A. Veitchii) in the 16 mountainous regions in the subalpine zone in Central and Northern Honshu, Japan. She studied, at first, the relationship between local wind directions and the running directions of mountain ridges which are classified into N-S, NW-SE, NE-SW and W-E. She also compared the wind directions estimated by wind-shaped trees with the data obtained from the instrumental observations at the climatological station near by.
The results obtained are summarized as follows:
(1) The prevailing wind directions are different regionally in accordance with the directions of mountain ridges. (2) According to the cluster analysis on the combination of wind directions by each direction of mountain ridges in the 16 regions, we can recognize some difinite wind systems with similar characteristics. (3) The regional division was made by these results as shown in Pig. 4. (4) On the basis of the results mentioned above, three climatological regions can be recognized in Central and Northeastern Japan, i.e., (i) The region where the mountain climate of Japan Sea side type prevails (Mt. HachimantaiIwate, Mt. Zao, Mt. Azuma-Adatara-Pandai, Happo-one, Mt. Renge-Eboshi-Mitsudake, Mt. Hakusan, Mt. Kusatsu-shirane). (ii) The region where the mountain climate belonging to the Pacific side type prevails (Ozegahara-nanryo, Mt. tsumata-KumonodairaTaro, Mt. Norikura, Mt. Neko-Azuma, Mt. Kisokoma). (iii) The region where the mountain climates of both types are mixed (Mts. Oku-nikko, Mt. Shiomi-Arakawa, Mts. Okuchichibu. Mt. Yatsu, Mt. Oomine). (5) Roughly speaking, the wind direction distribution estimated by wind-shaped trees on the Japan Sea side of Honshu is similar to the NW flow type of the surface wind system over lowlands. On the other hand, the wind direction distribution estimated by wind-shaped trees on the Pacific side of Honshu is similar to the SW flow type. (6) In addition, the author discussed the results with a few related phenomena: The regional division by climates presented here coincides well with that of the Suzuki's (1962), which was based on the distribution of precipitation in winter. It is, therefore, clear that the wind conditions over the mountainous regions have close relations to precipitation under the influence of winter monsoon.
(7) Shimagare phenomena (stripes of needle trees standing dead on the mountain slopes in the subalpine zone) are distributed on the slopes facing south, southwest and southeast in the subalpine zone in Chubu, . Kanto and Kinki Districts of Honshu. It is noteworthy that all of these areas belong to the mountain climate type on the Pacific side of Japan.

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