METEOROLOGICAL OBSERVATIONS AND GLACIER CHANGES. 341 



with that of any preceding period of time, so that the data cannot be con- 

 sidered as complete ; but since the recession of the glaciers did not begin 

 over a considerable part of the region in question until perhaps half of the 

 period embraced in the observations had elapsed, it would be reasonable to 

 expect that the two halves of the fifty j^ears would, when compared with 

 each other, show some difterences which might correspond with the changing 

 condition of the ice masses : this does not appear to be the case. 



It is by no means the intention of the writer to assert that such changes 

 have not taken place : on the contrary, he thinks it hardly possible to con- 

 ceive of any increase or decrease of the ice masses or snow fields, even of an 

 area of moderate size — and much less of one which embraces the Alps, 

 Pyrenees, and Caucnsus — without a corresponding climatic change. All that 

 is wished here to make prominent is the fact that verv slight disturbances of 

 the meteorological conditions produce great effects as manifested in the accu- 

 mulation of snow, its transformation into ice, and the distance to which that 

 ice is able to move from the region where it originated before being con- 

 verted back to water. There can be little doubt that, in time, observations 

 will be of assistance to us, in this as in other problems of climatological 

 science. 



The majority of geologists and Alpine explorers consider the recession 

 of the past half-century as of the nature of an oscillation. They confidently 

 expect that, after a time, the glaciers will advance and reoccupy the ground 

 which they have been losing of late years. In this idea they are, to a cer- 

 tain extent, justified, because it is known that there have been periods of 

 advance and retreat in the Alps — the only glaciated region in regard to 

 which we have historical data in reference to the subject before us. It is 

 not possible, however, to prove that the Swiss glaciers are not shorter now 

 than they have been at any previous time since the period of their greatest 

 extension. There are traditions of the Alps having been once, "during the 

 Middle Ages," very much more denuded of snow and ice than they now are ; 

 but those who have studied the subject most carefully do not put confidence 

 in these stories. 



The present writer looks on the recession of the glaciers which has been 

 taking place of late years as part and parcel of a general phenomenon of 

 desiccation, as indicated in the preceding chapter. From his own extensive 

 observations along the whole line of the Alps, he believes that the ice and 

 snow do at the present moment cover less surface than they have ever done 



