抄録
Analysing latitude observations made with the Danjon impersonal astrolabe at Paris during the period from 1956.6 to 1962.7, B. Guinot has recently obtained +0".007 as the rate of the progressive variation in latitude per year at Paris. We have tried to examine whether the progressive change in latitude at the independent station Paris can be explained by the secular motion of the pole derived from the I.L.S. results or not. The rate of the progressive variation in latitude per year at Paris deduced from the resultant secular motion of the pole which has been derived from the rates of the progressive variations in latitude per yearr at Mizusawa and Ukiah during the same period is +0″.008. This coincidence indicates that the secular change in latitude at Paris will be mostly explained by the secular motion of the pole derived from the secular variations in latitude at the two I.L.S. stations, Mizusawa and Ukiah. Then, in order to examine a possibility of the local displacement at lviizusawa, we have compared running Orlov mean latitudes at both Mizusawa and Tientsin for the period from 1959 to 1961. They appear to be very similar with each other, and so no relative horizontal displacement between the Asiatic continent and Japan islands can be detected at least during the three years from 1959 to 1961. Summarizing the above-mentioned examinations and the hitherto obtained results by several investigators, we may conclude that a major part of the secular variation of latitude at any station would be caused by the secular movement of the pole, but for some period the remaining part might be attributed to the station displacement. It is very desirable to carry out the simultaneous, geophysical measurements such as with the gravimeters, the extensometers and the horizontal pendulums at the stations observing polar motion for the direct solution of this complicated problem.
