Wrinkles in practical navigation - Tapa blanda

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 Excerpt: ... the Permanent International Geodetic Commission, which was held at Salzburg, determined to undertake an investigation of this important question by means of simultaneous observations at the Observatories of Berlin, Potsdam, Prague, and Strasburg, which were commenced in January 1889, and continued until April, 1890. The result of these ob servations was to show that in fact the latitudes of the places named were subject to periodical changes, the maxima of which occurred during the autumn, and the minima during the springtime. The greatest variation amounted to about one-half of a second (0'5), or in linear measure about 50 feet. 378 EXPEDITION TO HONOLULU. Variations of this extent could not be neglected in accurate geodetical measurements, where the calculations are often worked out to a few hundredths of a second. inconstancy of Theoretically, there are three possible reasons for variations in latitudes, viz., changes of gravity or of the plumb-line, the still unknown vibratory movements of the Earth's axis; and lastly, variations in the position of the Earth's rotation axis in the masa of the Earth itself. For the determination of this question it 13 necessary to have corresponding observations for latitude at two stations, as nearly as possible 180 distant from each other. In case it should be, as in fact did happen, that the variation of latitude takes place simultaneously, but in an opposite sense, the third explanation is the only one possible. The Permanent Commission for Earth-Measurement determined, therefore, in January, 1891, to despatch an astronomical expedition to Honolulu for the purpose of taking observations for latitude as accurately as possible, simultaneously with observations at the observatories of Berlin, Prague, and Strasburg. The...