EXPEDITION TOWARD THE NOKTII POLE. 385 



GLACIERS. 



The progress of our knowledge of glaciers has disclosed two sides of 

 the subject entirely discouuected with one another, and requiring dif- 

 ferent means of investigation. The study of the structure of glaciers as 

 they exist now, and the phenomena connected with their formation, 

 maintenance, and movement, constitute now an extensive chapter in the 

 physics of the globe. On the other hand, it has been ascertained that 

 glaciers had a much wider range during an earlier but nevertheless 

 comparatively recent geological period, and have produced during that 

 period phenomena which, for a long time, were ascribed to other agencies. 

 In any investigation of glaciers now-a-days, the student should keep in 

 mind distinctly these two sides of the subject. He ought also to remem- 

 ber at the outset what is now no longer a mooted point — that, at differ- 

 ent times during the glacial x>ei'iod, the accumulations of ice covering 

 larger or smaller areas of the earth's surface have had an ever-varying 

 extension, and that whatever facts are observed, their value will be 

 increased in i)roportiou as the chronological element is kept in view. 



From the x>hysical point of view, the Arctic expedition, under the 

 command of Captain Hall, may render science great service should Dr. 

 Bessels have an opportunity of comparing the present accumulations of 

 ice in the Arctic regions with what is known of the glaciers of the Alps 

 and other mountainous regions. In the Alps the glaciers are fed from 

 troughs in the higher regions, in which snow accumulates during the 

 whole year, but more largely during winter, and by a succession of 

 changes is gradually transformed into harder and harder ice, moving 

 down to lower regions where glaciers never could have been formed. 

 The snow-like accumulations of the upper regions are the materials out 

 of which the compact transparent brittle ice of the lower glaciers is 

 made. Whatever snow falls uj^on the glaciers in their lower range 

 during winter, melts away during summer, and the glacier is chieily fed 

 from above and wastes away below. The water arising from the melt- 

 ing of the snovf at the surface contributes only indirectly to the internal 

 ecouomj" of the glacier. It Avould be superfluous here to rehearse what 

 is known of the internal structure of glaciers and of their movement ; it 

 may be found in any treatise on glaciers. Nor would it be of any avail to 

 discuss the value of conflicting views concerning their motion. Suffice 

 it to say that an Arctic exj^lorer maj^ add greatly to our knowledge by 

 stating distinctly to what extent the winter snow, falling uj)on the sur- 

 face of the great glacial fields of the Arctic, melts away during summer 

 and leaves bare an old icy surface, covered with fragments of rock, sand, 

 dust, &c. Such an inquiry will teach us in what way the great masses 

 of ice which pour into the Arctic Ocean are formed, and how the supply 

 that empties annuallj' into the Atlantic is replenished. If the winter 

 snows do not melt entirely in the lower part of the Arctic glaciers during 

 summer, these glaciers must exhibit a much more regular stratification 

 than the Alpine glaciers, and the successive falls of snow must in them 

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