PROGRESS OF OUR KNOWLEDGE OF THE TIDES. 
127 
stances, there seems to be good authority for extreme ranges 
of even 70 feet having occurred. 
Throughout the Gulf of Maine the time of high water is 
nearly simultaneous, but in the arms of the Bay of Fundy 
the tide is largely progressive. On the seaward edge of the 
Gulf of Maine, at Georges Bank, the tide is quite small, but 
the tidal currents are strong enough to produce heavy tide 
rips in many places, much of which is quite similar to, but 
more complex than, the tidal movements of the Gulf of 
Suez. 
There have appeared from time to time quite a number of 
valuable papers upon the theory of tides; but I shall not 
attempt to refer to them at present because, with some few 
exceptions, they may be regarded as solutions of special prob¬ 
lems in hydrodynamics rather than as contributions to our 
practical knowledge of the tides, for they generally assume 
conditions which are not found in nature. 
