Survey of Northeast Greenland. 255 
occultations of stars. The error in the determination of longitude 
arises — apart from the general uncertainty of the co-ordinates of 
the moon — almost exclusively from the error of the determination 
of time, and here one may, with great certainty, take it for granted 
that the two astronomers have arranged their determinations in such 
a manner that an error in refraction could not come to play any 
part worth mentioning. However, as the determinations of time of 
the Germaniaexpedition have not been published, it is no longer 
possible to verify this circumstance. 
If one absolutely wants to maintain that CLAvERING cannot have 
marked off the site of Sasıne’s Observatory in a wrong place — and 
as often mentioned this seems to me the most natural conclusion to 
adopt — one arrives by means of РаАуЕв’$ map, whether starting 
from the one or the other hypothesis as to the difference of latitude 
between the two observatories, at the result that the drift in a 
westerly direction in the period 1823—1870 was about 420 metres or 
about 9 metres a year. For the entire period 1833—1907 the average 
yearly movement towards west will be 19 metres. 
Have we now, by means of the two determinations of longitude 
on Sabine Island, found the support for the supposition concerning 
the drifting of Greenland which we sought? 
The question may, I suppose, be answered in the affirmative. 
It cannot be denied that the whole of the research is encumbered 
with a very serious uncertainty, and that the two mean values of 
the yearly drift, 9m within the period 1823—1870 and 32m within 
the period 1870—1907, do not harmonize very well. It must, how- 
ever, not be overlooked that we have no knowledge of the forces 
that cause the presumed drift. It would, I suppose, in reality seem 
more natural if the drift did not show itself an even movement, but 
subject to considerable variations at different periods’). 
The uncertainty of the mutual position of the two observatories 
on Sabine Island might in the main be got rid of by a short visit 
to the place itself. If the visit were extended over a fortnight, it 
1) According to the hypothesis of WEGENER the rift in the Atlantic Ocean has 
opened from the south, and only during the glacial age has it caused Green- 
land to break away from Norway, which theory corresponds with a series of 
well-known geological as well as phyto- and zoogeographical circumstances. 
WEGENER consequently thinks that the drift in more southern parts cannot 
be supposed to proceed with the same rapidity as in the case of Greenland. 
To support his theories he quotes the result of the three telegraphic deter- 
minations of longitude between Greenwich and Cambridge (North America) 
that is 
1866 difference of longitude 4h44m30s.89 
1870 — - — 4h 44m31s .065 
1892 — - — 4h 44m31s,12. 
XLVI. 17 
