ATMOSPHERE 285 



When we had fogs they were rarely so opaque as those 

 we are familiar with at home, and very much less dense 

 than the fogs off the coast of Nova Scotia and New- 

 foundland. It is probable that there is not dust enough 

 in the air to form sufficient nuclei for the quick con- 

 densation of such thick fog as is common off the east- 

 ern coast below Labrador. The fogs were, however, 

 wet enough to make up for their lack of opacity, although 

 not so wet as occur on Baffin Bay and along the coast of 

 Greenland. 



It is the dust and the particles of ice or half condensed 

 watery vapor suspended in the air that scatter the light 

 and make the atmosphere seem luminous. Much dust 

 in the air diminishes sensibly the actual amount of light 

 that reaches the surface of the earth and also changes its 

 character. Therefore, we often had an abundance of light 

 on cloudy days, in fact more than one would suppose. 

 The wonderful clearness of some of the photographs 

 which were taken by the party on cloudy days is one evi- 

 dence of this. This quality of the light in Alaska was a 

 factor in the production of so many successful photographs 

 by the party and gave many of them exceptional beauty 

 and excellence. 



As to the clouds, we saw none with rounded heads 

 (' cumuli' as meteorologists call them) north of the 

 Alaska Peninsula and but very few anywhere along the 

 Alaska coast. Over Bering Sea and northern coasts the 

 clouds had ragged edges, shreddy, never sharp in out- 

 line none with rounded heads such as form a factor 

 in the summer sky-scenery of warmer lands. Both as 

 we went out and on our return, a few cumulus clouds 

 curled over the peaks on the Peninsula, but the clouds that 

 adorned most of the mountains were not sharply out- 

 lined; they sometimes stretched away from the summits 

 like frayed banners. 



