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WORK OF ‘‘ MAUD’’ EXPEDITION—SVERDRUP 231 
and recorded the direction relative to the orientation of this frame. 
The latter type was kept in operation during the major part of 14 
months. By lowering it to various depths we could obtain a full 
knowledge of the tidal currents from the ice to the bottom. The 
tidal motion of the ice itself was determined directly by a simpler 
method. 
Our main results, representing the conditions at spring tide, have 
been entered on the map reproduced in Figure 5. The character of 
the tidal currents is indicated by the ellipses. They signify that the 
currents are rotating, the arrow-heads on the ellipses indicating the 
direction of rotation, which is clockwise within the entire region. 
The ratio between the axes of the ellipses corresponds to the ratio 
between the maximum and minimum current. The direction of 
maximum current is indicated by an arrow, and the Greenwich 
lunar time of maximum current is entered. Furthermore, the Green- 
wich lunar time of high water and the range of the spring tide are 
entered at all stations where data were available. Previous observa- 
tions have been utilized from Point Barrow, Pitlekai, and Bennett 
Island, but all others represent results obtained during the six years 
the Maud has spent in the Arctic. 
By means of the data entered on this map it is possible to draw 
lines showing the crest of the tidal wave for certain hours of Green- 
wich lunar time. The heavy lines show these crests, and the corre- 
sponding hours have been entered. The wave appears to reach the 
shelf from the north and seems to come directly across the Polar Sea 
from the Atlantic side without meeting any obstruction formed by 
masses of land. The late Prof. R. A. Harris, of the United States 
Coast and Geodetic Survey, compiled and discussed in 1911 all avail- 
able tidal observations from the Arctic region. He arrived at the 
conclusion that the tidal wave within the region here dealt with 
travels practically parallel to the coast, and assumed, therefore, that 
a great area of land or very shallow water existed within the unknown 
area north of Alaska and Siberia. His conception of the direction in 
which the wave proceeds seems, however, to be erroneous, as the tidal 
phenomena seem to indicate no existence of extensive land masscs 
between Alaska and the pole. 
The tidal wave on the shelf shows a number of interesting features. 
The currents are rotating clockwise at all stations and vary with the 
distance from the bottom; the rate of progress does not bear a simple 
relation to the depth; the range of the spring tide decreases from 
right to left along the wave crest, referred to an observer looking in 
the direction of progress, namely, from 215 centimeters close to the 
New Siberian Islands to 14 centimeters at Point Barrow; and the 
range also decreases in the direction of progress, from 18 centimeters 
at the middle of the shelf to 3 centimeters at Bear Islands. These 
