

CLOUDS AND RIVERS, ICE AND GLACIERS. 175 



they freeze, a bridge is formed and melted ; and thus 

 the rhythmic action continues until the ice disappears. 



448. According to Professor James Thomson's 

 theory, pressure is necessary to liquefy the ice. The 

 heat necessary for liquefaction must be drawn from the 

 ice itself, and the cold water must escape from the 

 pressure to be re-frozen. Now in the foregoing experi- 

 ments the cold water, instead of being allowed to freeze, 

 issues into the warm water, still the floating fragments 

 regelate in a moment. The touching surfaces may, 

 moreover, be convex ; they may be reduced practically 

 to points, clasped all round by the warm water, which 

 indeed rapidly dissolves them as they approach each 

 other ; still they freeze immediately when they touch. 



444. Tou may learn from this discussion that in 

 scientific matters, as in all others, there is room for 

 differences of opinion. The frame of mind to be culti- 

 vated here is a suspension of judgment as long as the 

 meaning remains in doubt. It may be that Faraday's 

 action and Thomson's action come both into play. I 

 cannot do better than finish these remarks by quotin a 

 Faraday's own concluding words, which show how in 

 his mind scientific conviction dwelt apart from doo*ma- 

 tism : — ' No doubt,' he says, < nice experiments will 

 enable us hereafter to criticise such results as these, 

 aud separating the true from the untrue will establish 

 the correct theory of regelation.' 



