1 68 PLEASANT WA YS IN SCIENCE. 



however, that he really intended to signify that the waves 

 were formed in seas around the North Pole, and thence 

 reached the place where they were seen ; so that, as birth 

 usually precedes cradling, Maury would more correctly have 

 said that these tides are cradled in that cold sea, having their 

 birth about the North Pole. 



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 doubt- 

 ful, 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 com- 

 municating 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 con- 

 dition 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 Palaeo- 

 crystic Sea ice 200 feet thick reached from shore to shore 



