TOWARDS THE NORTH POLE. 169 



of the North Atlantic channel, the tidal wave would burst 

 the barrier as easily as a rivulet rising but a few inches bursts 

 the thin coating which has formed over it on the first cold 

 night of autumn. But no such massive barriers have to be 

 broken through, for the tidal wave never gives the ice an 

 hour's rest Maury reasons that " the tidal wave from the 

 Atlantic can no more pass under the icy barrier to be pro- 

 pagated in the seas beyond, than the vibrations of a musical 

 string can pass with its notes a fret on which the musician 

 has placed his finger." But the circumstances are totally 

 different. The ice shares the motion of the tidal wave, 

 which has not to pass under the ice, but to lift it This, 

 of course, it does quite as readily as though there were 

 no ice, but only the same weight of water. The mere 

 weight of the ice counts simply for nothing. The tidal wave 

 would rise as easily in the British Channel if a million Great 

 Easterns were floating there as if there was not even a 

 cock-boat ; and the weight of ice, no matter how thick or 

 extensive, would be similarly ineffective to restrain the great 

 wave which the sun and moon send coursing twice a day 

 athwart our oceans. Maury's other mistake was even more 

 important so far as this question of an open sea is con- 

 cerned. "No one," as I wrote in 1867, "who is familiar 

 with the astronomical doctrine of the tides, can believe for 

 a moment that tides could be generated in a land-locked 

 ocean, so limited in extent as the North Polar sea (assuming 

 its existence) must necessarily be." To raise a tidal wave 

 the sun and moon require not merely an ocean of wide 

 extent to act upon, but an ocean so placed that there is 

 a great diversity in their pull on various parts of it ; for it 

 is the difference between the pull exerted on various parts, 

 and not the pull itself, which creates the tidal wave. Now 

 the Polar sea has not the required extent, and is not in 

 the proper position, for this diversity of pull to exist in 

 sufficient degree to produce a tidal wave which could be 

 recognized. It is certain, in fact, that, whether there is 

 open water or not near the Pole, the tides observed by 



