It is chiefly to the expeditions of Drs. Kane and Hayes that we owe the important knowledge we have respecting the northerly portions of the straits which lie to the west of Greenland. Each of these explorers succeeded in reaching the shores of an open sea lying to the north-east of Kennedy Channel, the extreme northerly limit of those straits. Hayes, who had accompanied Kane in the voyage of 1854-5, succeeded in reaching a somewhat higher latitude in sledges drawn by Esquimaux dogs. But both expeditions agree in showing that the shores of Greenland trend off suddenly towards the east at a point within some nine degrees of the North Pole. On the other hand, the prolongation of the opposite shore of Kennedy Channel was found to extend northwards as far as the eye could reach. Within the angle thus formed there was an open sea ‘rolling,’ says Captain Maury, ‘with the swell of a boundless ocean.’ But a circumstance was noticed respecting this sea which was very significant. The tides ebbed and flowed in it. Only one fact we know of—a fact to be presently discussed—throws so much light on the question we are considering as this circumstance does. Let us consider a little whence these tidal waves can have come. The narrow straits between Greenland on the one side, and Ellesmere Land and Grinnell Land on the other, are completely ice-bound. We cannot suppose that the tidal wave could have found its way beneath such a barrier as this. ‘I apprehend,’ says Captain Maury, ‘that the tidal wave from the Atlantic can no more pass under this 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.’ Are we to suppose, then, that the tidal waves were formed in the very sea in which they were seen by Kane and Hayes? This is Captain Maury’s opinion:—‘These tides,’ says he, ‘must have been born in that cold sea, having their cradle about the North Pole.’