1889-90.] 
Mr J. Aitken on Dust Particles. 
227 
this dust owing to the high temperature has much moisture attached 
to it, even though the air is what is called dry. The conclusion we 
have come to is, that though there may be other causes of haze, yet 
dust is generally the cause of it. 
Notes from the Rigi Kulm. 
While at the Eigi Kulm, I observed a few meteorological pheno- 
mena which may be briefly referred to here, as they have some 
bearing on our subject. On my arrival at midday on the 21st of 
May, the hill top was covered with clouds, and we remained all 
day in a thick fog. However, as the afternoon advanced, an 
occasional glimpse was obtained of some of the higher Alps of the 
south, standing clear above the mass of cloud which filled in the 
valleys, and from time to time enveloped the place of observation. 
These unfortunately were but limited and passing glimpses, and all 
to the west was blocked with clouds. At last, however, shortly 
before the sun dipped below the horizon, the clouds began to clear 
overhead, and at last they rolled away, and the top of the Eigi 
stood clear above a billowy mass of clouds, and the western sun 
suddenly burst out brilliantly, dissipating in a moment the dull 
chill oppression of the fog. So sudden and welcome was the change, 
that the few who were waiting on the mountain top, in the almost 
forlorn hope of seeing the setting sun, raised a cheer of welcome ; 
a cheer which rose simultaneously from every one, and could not 
have been more real, spontaneous, and stirring had we been a body 
of sun-worshippers welcoming our divinity. 
The change, however, was momentary, for soon another mass of 
cloud passed across the hill top and obscured the view, but not for 
long, and it, in turn, was followed by another, each succeeding mass 
being less than the previous one, while each glimpse showed the 
west to be clearing, and at last no clouds rose above the mountain, 
and a magnificent view was obtained all round. Occasional openings 
in the clouds below gave passing views of the lakes and valleys low 
down near the base of the mountain, but on this occasion the great 
attraction was the cloud scenery. In most directions there extended 
a vast sea of clouds, the upper surface of which was slightly lower 
than the point of view. This wide area of clouds extended nearly 
level as far as the eye could see, its upper surface brilliantly 
