Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/141

Rh page 240, in his section on the Survey of North-east Greenland in the chapter, 16 pages long, headed “The Drift of North Greenland in a Westerly Direction,” the longitude determinations of Sabine (1823), Börgen and Copeland (1870) and Koch (1907). He thereby obtained a difference which increased in the course of time, and which corresponds to an enlargement of the distance between North-east Greenland and Europe amounting to:—

The determinations of longitude were not carried out on exactly the same spots. Sabine observed it on the southern margin of the island named after him. Unfortunately, there still exists in this matter some degree of uncertainty, to be sure not very important, about the exact spot, which would probably be removed by another examination of the locality. Börgen and Copeland made observations on the same area but some 100 metres to the east. Koch’s observations, on the other hand, were made much farther north on Danmarkshafen in Germania Land, but are connected by triangulation with Sabine Island. The inexactitudes arising from this carrying-over were exhaustively studied by Koch, with the result they can be disregarded when compared with the much greater inaccuracies of the longitude determinations themselves. Since these were obtained in all three cases by observations on the moon, the accuracy is of necessity much less than the determinations of longitude by means of wireless telegraphy. The mean error deduced from a comparison of the figures of