1898 - 99 .] Dr Buchan on Tidal Currents of the North Sea. 481 
strongest outflowing tidal currents keep near the coasts of Denmark 
and Norway. The cause of this striking peculiarity admits of a 
simple explanation. Since, as the tidal currents from the north 
flow southwards, they advance over regions where the velocity of 
the earth’s rotation constantly increases, and consequently lagging 
behind, they press in toward the east coast of Great Britain ; and 
on the other hand, as the outflowing tidal currents proceed north- 
wards, they advance over regions where the velocity of the earth’s 
rotation constantly diminishes, and consequently press close on the 
coasts of Denmark and Norway. 
It is a singular circumstance that the North Sea is the only sea 
in the Northern Hemisphere quite open to large tidal currents 
from a contiguous ocean, which flow southwards with flowing 
tides and northwards with ebbing tides ; and it is probably owing 
to this circumstance that hitherto, so far as I am aware, the rota- 
tion of the earth has not been adduced in explanation of the most 
striking peculiarity of these tidal currents. 
