364 Mr. J. Ball on a doubtful point in Climatology. 



chain, and elsewhere in the Alps; as, for instance, the plateau, 

 about 13,000 English feet above the sea, which lies between the 

 highest ridge of the Monte Rosa, the Zumstein Spitz, and the 

 eastern end of the Lys Kamm, or the extensive and slightly 

 inclined slopes which lie to the east of the Pass of St. Theodule. 

 It would seem as if the existence of such centres of accumulation 

 would alone serve to explain the fact established by the unani- 

 mous current of history and tradition, which affirm the gradual 

 extension and advance of the great glaciers throughout the entire 

 chain of the Alps, simultaneously with a general constancy in 

 the cliinatal conditions of the surrounding countries. A few 

 unimportant exceptions may be pointed out, such as that of the 

 glacier of Findelen near Zermatt, which has retrograded for the 

 last forty or fifty years, while the Gorner glacier originating in 

 the same ice-fields has advanced to more than a proportionate 

 extent. These cases may probably be explained by landslips 

 altering the direction of the upper portion of certain glacier 

 streams, but they cannot invalidate the universal consent of all 

 available evidence as to the general extension of the glaciers. 

 For this we rely, not merely upon concurrent tradition and do- 

 cumentary evidence, but on the unimpeachable declarations of 

 those ancient tracks and paved footways which we now find in- 

 vaded by ice and neve. 



But if I do not mistake, there is evidence of a similar pheno- 

 menon on a much larger scale in the polar regions. Some of 

 this evidence afforded by vegetable and animal remains in regions 

 now chiefly covered with snow and ice may be open to question 

 as to its true date, but it appears to me that the remarkable 

 and well-known facts proving a local diminution of temperature 

 in the plains of Iceland and Greenland, extending over the last 

 700 or 800 years, may far more easily be explained by the con- 

 tinuous accumulation of ice in the upper portions of those and 

 the adjoining countries, than by any other hypothesis with which 

 I am acquainted. It is true that, in regard to Iceland, the 

 change of climate which has gradually driven out the cultivation 

 of grain and reduced the tree vegetation to the dwarf birch scrub 

 which alone now remains, may be in some degree connected with 

 the enormous outburst of lava in the eruption of the Skaptar 

 Yokul, substituting in the interior of the island a vast tract of 

 surface of much greater radiating power ; but it is questionable 

 whether, under skies so charged with clouds as those of Iceland 

 are in summer, this explanation can serve much, while the arbi- 

 trary assumption of a change in the force and direction of the 

 Gull-stream is scarcely reconcileable with the absence of any 

 sensible change in the coast climate of north-western Europe. 

 This latter explanation, again, can still less easily be applied to 



