

Mr. J. Ball on a doubtful point in Climatology. 363 



tended to the scapolites), that I became aware that Th. Scheerer 

 had recently proposed to regard all felspars as combinations of 

 anorthite with labradorite, anorthite with albite (orthoclase), or 

 labradorite with albite*. It was gratifying to find that this 

 distinguished chemist had already arrived at a solution of the 

 problem of the felspars not unlike my own, but I must object 

 to admitting labradorite as a distinct species, or as having any 

 higher value than oligoclase, andesine, or the felspars X. and 

 XV. in the present paper. 



Montreal, Canada, 

 March 1855. 



LI. Note on a doubtful point in Climatology. 

 By John Ball, Esq., M.P. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



IN common with many persons who have paid attention to 

 glacier phenomena, I have often found it difficult to recon- 

 cile the mass of testimony which seems to indicate the continued 

 increase and accumulation of ice and snow in certain regions of 

 the earth, with the equally strong evidence which goes to prove 

 that the general climate of the inhabited portions has not sen- 

 sibly varied throughout the historic period. Having lately had 

 occasion to discuss the subject with somewhat stricter accuracy, 

 I think that I am enabled to offer an explanation of the diffi- 

 culty which I am desirous of submitting to the judgement of 

 your readers. 



I may commence by observing, that in the course of firequent 

 visits to the higher regions of the European Alps, I had been 

 struck by appearances which indicate that, even at the present 

 time, there are certain spots of limited extent in which this pro- 

 cess of accumulation still proceeds, and where, if we only admit 

 that at some period since the glacial epoch the mean tempera- 

 ture of this portion of the earth was slightly greater than it now 

 is, simple physical considerations show that such accumulation 

 must have ensued. This, in fact, merely amounts to the asser- 

 tion, that there are natural reservoirs or plateaux in the upper 

 regions of the Alps where the annual increase of neve or conso- 

 lidated snow is greater than the annual loss by melting, evapo- 

 ration, and outflow of glacier towards the lower regions. Several 

 such instances might, I think, be pointed out in the central 



* Poggendorff*! Annalen, vol. lxxxix. p. 19, cited in Licbig and Kopp's 

 Jahresbericlit, 18S3> p. 805. 



