The observations of Kane and Hayes afford no reason, however, for supposing that there is open water around the North Pole. They have been rendered somewhat doubtful, be it remarked in passing, by the results of Captain Nares’s expedition; and it has been proved beyond all question that there is not an open sea directly communicating with the place where Kane and Hayes observed tidal changes. But, apart from direct evidence of this kind, two serious errors affect Maury’s reasoning, as I pointed out eleven years since. In the first place, a tidal wave would be propagated quite freely along an ice-covered sea, no matter how thick the ice might be, so long as the sea was not absolutely icebound. Even if the latter condition could exist for a time, the tidal wave would burst the icy fetters that bound the sea, unless the sea were frozen to the very bottom; which, of course, can never happen with any sea properly so called. It must be remembered that, even in the coldest winter of the coldest Polar regions, ice of only a moderate thickness can form in open sea in a single day; but the tidal wave does not allow ice to form for a single hour in such sort as to bind the great ice-fields and the shore-ice into one mighty mass. At low tide, for a very short time, ice may form in the spaces between the shore-ice and the floating ice, and again between the various masses of floating ice, small or large (up to many square miles in extent); but as the tidal wave returns it breaks through these bonds as easily as the Jewish Hercules burst the withes with which the Philistines had bound his mighty limbs. It is probable that if solid ice as thick as the thickest which Nares’s party found floating in the Palæocrystic Sea—ice 200 feet thick—reached from shore to shore 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 propagated 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.