234 FRAGMENTS OF SCIENCE 



at Fort William is 86 inches, while at Laggan it is only 

 46 inches, annually. The difference between west and east 

 is forcibly brought out by observations at the two ends of 

 the Caledonian Canal. Fort William at the southwestern 

 end has, as just stated, 86 inches, while Culloden, at its 

 northeastern end, has only 24. To the researches of that 

 able and accomplished meteorologist, Mr. Buchan, we are 

 indebted for these and other data of the most interesting 

 and valuable kind. 



Adhering to the facts now presented to us, it is not 

 difficult to restore in idea the process by which the gla- 

 ciers of Lochaber were produced and the glens dammed 

 by ice. When the cold of the glacial epoch began to in- 

 vade the Scottish hills, the sun at the same time acting 

 with sufficient power upon the tropical ocean, the vapors 

 raised and drifted on to these northern mountains were 

 more and more converted into snow. This slid down the 

 slopes, and from every valley, strath, and corry, south of 

 Glen Spean, glaciers were poured into that glen. The two 

 great factors here brought into play are the nutrition of the 

 glaciers by the frozen material above, and their consump- 

 tion in the milder air below. For a period supply ex- 

 ceeded consumption, and the ice extended, filling Glen 

 Spean to an ever-increasing height, and abutting against 

 the mountains to the north of that glen. But why, it may 

 be asked, should the valleys south of Glen Spean be re- 

 ceptacles of ice at a time when those north of it were 

 receptacles of water? The answer is to be found in the 

 position and the greater elevation of the mountains south 

 of Glen Spean. They first received the loads of moisture 

 carried by the Atlantic winds, and not until they had been 

 in part dried, and also warmed by the liberation of their 



