Abstract
In the first part of this paper, some geodesic reductions were made upon the deflections of the vertical which were observed in Japan, and then, in the second part, the. corrections due to the topography were applied, assuming that the mountain or the sea exert as an excess or defect of mass respectively.
The result of this calculation show that the plumb lines are generally attracted toward the Pacific Ocean (the arows in Fig. 3 are drawn in the opposite sence of the attraction). This fact show that the theory of Isostasy holds for Japan also, because the Pacific Ocean is relatively deeper compared with that of Japan sea. Lastly, the depth of isostatic compensation was calculated by the method of, trial and error assuming the various depth of compensation, and it was determined to be about 120km. below the mean sea level (see Fig. 5).
