260 
DR. HAROLD JEFFREYS ON TIDAL FRICTION IN SHALLOW SEAS. 
2. The North-west Passage. 
The channel from the Atlantic to the Arctic between Canada and Greenland is 
blocked by a large number of islands of varying sizes, between which are narrow and 
shallow straits. The dissipation in several of these can be estimated from data in the 
‘ Arctic Pilot,’ vol. 3. 
The chief of these channels is Davis Strait, with Baffin Bay to the north of it, 
which lies between Baffin Land and Greenland. It is about 1600 km. in length. 
The only tidal velocities recorded in it, except in fjords, are near Holstenborg, in 
Greenland, where the currents in the offing are said to reach a speed of two knots. 
This cannot, however, be general, for there is a shallow region off Holstenborg, some 
150 km. long and 60 km. wide, with a depth of about 23 fathoms. Most of the 
strait is about 100 fathoms deep. This region is therefore a place where the main 
current of the strait is magnified by the form of the bottom, and there is no reason to 
believe that the current in the deep water is greater than half a knot, which is the 
observed velocity off the coast of Labrador. The dissipation in Davis Strait is 
therefore not great. 
At the northern extremity of the strait there are several narrow passages into the 
Arctic. The dissipation in these must be important. In Smith Sound and Kennedy 
Channel, for instance, which separate the north-west coast of Greenland from 
Ellesmere Land, the current is said to be “nearer two figures than one.” These 
straits are small in area, but if such currents exist over much of their extent we must 
take them into account. The data available at present are unfortunately too meagre. 
The south end of Davis Strait is connected to Hudson Bay by Hudson Strait. 
The currents in this are described as “ great enough to be dangerous,” especially at 
the east end; but the recorded currents, even in the middle of the strait, are only 
about three-quarters of a knot. This makes the average dissipation about 
5 x 10 16 ergs per second. The danger arises mostly from drifting ice. 
In the entrance to Hudson Bay the velocity increases to one and a half knots. 
The area over which this is true is about 3‘8 x 10 14 sq. cm., making the average 
dissipation 1‘5 x 10 17 ergs per second. 
In Hudson Bay itself the currents are probably very small. Considerable 
velocities are recorded at Port Churchill, but there are no records in the middle of 
the bay. The depth in the middle is about 50 fathoms, which is about the same as 
at the entrance. The entering current must therefore spread out in the bay and 
undergo great diminution in strength. Near Port Churchill the depth is only 19 
fathoms or less, so that the current there must be a local current magnified. The 
dissipation in Hudson Bay must therefore be small. 
In Fox Strait, which runs northwards from the entrance to Hudson Bay, the 
depth is less, about 20 fathoms, and the current reaches one and a half knots. The 
area of this channel is 2xl0 15 sq. cm., and the appropriate average dissipation is 
