METEOROLOGY 



cloud) trailing off to the south, while the great bank hangs 

 on the north. Generally this great cloud rests on the north 

 slope, but occasionally the position is reversed. 



Spieal Cloud. — modification of the great cloud- 

 bank, produced by the meeting of very gentle currents, 

 resulted in the rolling up of the cloud into a spiral form. 



On July 23 a spiral was formed from a bank on the 

 south side of the mountain, as figured below. The upper 



Whale-backb, September 16 



current on this occasion was from the south. A similar 

 spiral cloud is figured, right over the mountain, in the 

 picture of saw-edged stratus, October 1. 



The most remarkable spiral cloud observed was that 

 of September 25, 1908. The bank of cloud lay on the 

 north flank. The upper current was from the south, as 

 on July 23. Its action was so regular that the spiral could 

 be traced for more than a complete turn. 



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