Hisashi Kimura "The International Latitude Service," Vierteljahrschrift der Astronomische Gesellshaft 63 359–361 1928 Kimura
12: An Interim Report on an International Research Project: The Wandering of the North Pole
1
By H. Kimura
The present state of the work on latitude variation:
(1) International Latitude Service on the north parallel +39° 8′.—The number of international stations was six in the beginning of their cooperation (namely, 1900.0), which number was reduced to four because of several unavoidable circumstances about the years 1914–1915, and then again one was lost about the year 1919. Thus now only three stations in America, Italy, and Japan have remained. These three independent stations are satisfactory for the finding of the two coordinates of the polar motion (x and y) and the unknown declination error, together with the non-polar variation (z) common to all stations. But certainly the observations at these stations must contain local systematic errors and also accidental errors. As a consequence, the final results are not accurate enough.
Fortunately, through the great effort of Professor Subbotin, the Director of Taschkent Observatory, the establishment of a new station at Kitab near Samarkand in Uzbekistan was decided upon, and the observations will probably be commenced in the autumn of this year.
(2) Free cooperations.—The following observatories have been making observations of latitude variation for many years: Washington, Greenwich, Pulkowa, and only one in the southern hemisphere, Rio de Janeiro, Besides these observatories, a new station at the Lembang Observatory, Java, will be established by the kindness of its Director, Dr. Voûte. This may also be commenced within this year. All persons who are interested in the work would welcome the results from this observatory as having a particular advantage, lying near the Equator.
(3) A new enterprise of the international cooperation in the southern hemisphere, namely two latitude stations in the observatories of La Plata and Adelaide, will probably be realized within a few years. Those observatories lie fortunately on nearly the same parallel, within
Fig. 1. A sample record of the wandering of the North Pole.
one minute of latitude, and on nearly the same but opposite meridians, like the old stations at Oncativo and Bayswater.
Next I have to add a few words about the results of the recent observations made at the international stations, Greenwich, and Washington. Generally speaking, those of the two observatories agree very well with that of the international service, provided that the former two are corrected by their own z. It is of importance that the instruments used at Greenwich and Washington are not only different from each other but also different from the visual Zenith telescope used in all international stations. However, in the results of the last years at both observatories some abrupt decreases in their mean latitudes of a pretty considerable amount, say 0″.07, have occurred, while the same phenomena did not appear in the international result for the corresponding epochs. But it must be understood that such phenomena have happened in almost all observations of the latitude variation.
Now we pass to the z-phenomenon (Non-polar variation).
(a) International service. In my annual reports for the latitude variation the part of the non-polar variation was given in another form than z. However, if we calculate it in the same manner as that made usually for the chain method, nearly the same curve of z as that in the previous years can be obtained.
(b) Greenwich. At this observatory z consists principally of a semiannual form, the annual one being very small. It is noteworthy that the observations during the period 1890–1900, which were carried out in the latitude of about +52° for instance, at Prague and Potsdam, gave also z of such double period annually. But there is one exception, with the observations made at Leiden. which contain an annual period of a considerable amount.
(c) Washington. In this observatory z is very similar to that of the international service. And the old observations made at New York gave also nearly the same z. . . .
Since a few years ago, the 14-month motion contained in the polar motion has become considerably smaller and its period has shortened. As Chandler had noticed already, the similar status had once occurred in the year about 1840. And I think the same state of smallness of the 14-month motion will continue a few more years.
1 [The Editor has made a number of verbal changes in Dr. Kimura’s translation.]