220 FKAGMENTS OF SCIENCE. 



Reeks, moved through the Black Valley, took posses- 

 sion of the lake-basins, and left its traces on every rock 

 and island emergent from the waters of the upper lake. 

 They are all conspicuously glaciated. Not in Switzer- 

 land itself do we find clearer traces of ancient glacier 

 action. 



What the Macgillicuddy Reeks did in Ireland, Ben 

 Nevis and the adjacent mountains did, and continue to 

 do, in Scotland. We had an example of this on the 

 morning we quitted Roy Bridge. From the bridge 

 westward rain fell copiously, and the roads were wet ; 

 but the precipitation ceased near Loch Laggan, whence 

 eastward the roads were dry. Measured by the gauge, 

 the rainfall 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 obser- 

 vations at the two ends of the Caledonian Canal. Fort 

 William at the south-western end has, as just stated, 

 86 inches, while Culloden, at its north-eastern end, has 

 only 24. To the researches of that able and accom- 

 plished 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 

 glaciers of Lochaber were produced and the glens 

 dammed by ice. When the cold of the glacial epoch 

 began to invade the Scottish hills, the sun at the same 

 time acting with sufficient power upon the tropical 

 ocean, the vapours 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 bro?aght into play are the nutrition of the glaciers 



