THE GLACIERS OF NORWAY. 461 



melting and freezing which go on through all but the coldest weather 

 of the year. Whether it is the pressure of the n'ev'e, or the irresistible 

 expansion caused by the action of cold upon the water pervadino- its 

 great mass, that drives off" the glacier, is a question respecting which 

 the most intelligent observers are by no means unanimous. Against 

 the theory of weight as the motive power is urged the fact that occa- 

 sionally the glaciers are not strictly adjacent to the superior snow- 

 field, but separated from it by an intervening space of bare rock. 

 When once it has emerged from the 7ieve, the glacier becomes a stream 

 of ice chiefly distinguished from a fluid river by the greater sluo-o-ish- 

 ness of its current. How, it may be asked, can a mass of solid ice 

 move in a fixed channel ? The question was long unanswered. In- 

 deed, it was only slowly that the truth forced itself upon the scientific 

 world that it does actually move at all. And, the fact being conceded, 

 the explanation is still not altogether easy. Prof. Sexe imagines that 

 the plastic character of the glacier, as he has observed it in the neigh- 

 borhood of Justedal, resides in the ease with which the ice fractures 

 and the equal facility witli which it reunites when fragments are 

 brought together. Thus it is that, under the immense weight of the 

 glacier, the glassy material of which it is composed is rent when 

 brought into contact with some solid rock standing in its bed, and 

 that the parted streams become one again as soon as the obstacle in 

 their way is passed. So also it is that longitudinal fissures regularly 

 form in the lower part of the glacier of Boium, when tlie glacier 

 reaches a point where it can expand in the less contracted valley, 

 while transverse fissures open in the glacier of Suphelle at a place 

 where the inclination suddenly becomes more considerable than it 

 was at first, and close up as soon as the slope is again a gentle one. 

 M. de Seue, on the other hand", emphasizes the peculiar constitution 

 of the ice of glaciers, that is, the ice which is formed by the compres- 

 sion and metamorphosis of snow " The ice of the glacier," he says, 

 " is, as already remarked, composed of distinct particles. From a 

 piece of this ice you can, as a general thing, easily remove the parti- 

 cles, one after the other, without injuring the surrounding ones ; and, 

 if you should find a particle which cannot be taken out without afflict- 

 ing the rest, you will still notice that you can move it a little rela- 

 tively to the others without harming them. Take a piece of the ice 

 of the glaciers of a convenient size, and, in trying (so gently that it 

 does not break) to twist or bend it, you will notice at once that there 

 is a little changeableness in the minute portions of which it is com- 

 posed." 



Both M. de Seue and Prof. Sexe reject tlie theory of expansion as 

 failing to account for the phenomenon of the glacier's progression, 

 and both virtually agree in ascribing that progression to the combined 

 influence of the enormous pressure exerted by the glacier's Aveight 

 and the melting produced by the air. Unfortunately for tlie former 



