CLOUDS AND RIVERS, ICE AND GLACIERS. 27 



precipitated, some of them yielding clouds of intense 

 brilliancy, and displaying iridescences, such as are some- 

 limes, but not frequently, seen in the clouds floating 

 ever the Alps. 



80. In science what is true for the small is true for 

 the large. Thus by combining the conditions observed 

 on a large scale in nature we obtain on a small scale the 

 phenomena of atmospheric clouds. 



§ 8. Mountain Condensers. 



81. To complete our view of the process of atmo- 

 spheric precipitation we must take into account the 

 action of mountains. Imagine a south-west wind 

 blowing across the Atlantic towards Ireland. In its 

 passage it charges itself with aqueous vapour. In the 

 south of Ireland it encounters the mountains of Kerry : 

 the highest of these is Magillicuddy's Reeks, near 

 Killarney. Now the lowest stratum of this Atlantic 

 wind is that which is most fully charged with vapour. 

 When it encounters the base of the Kerry mountains 

 it is tilted up and flows bodily over them. Its load of 

 vapour is therefore carried to a height, it expands on 

 reaching the height, it is chilled in consequence of the 

 expansion, and comes down in copious showers of rain. 

 From this, in fact, arises the luxuriant vegetation of 

 Killarney; to this, indeed, the lakes owe their water 

 supply. The cold crests of the mountains also aid in 

 the work of condensation. 



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