abstracts: meteorology 111 



explained. The second part treats of the vortex movements of the atmos- 

 phere, and is by no means such easy reading as the first part. 



The author made the observations upon which his article is based 

 during the winter and in the mountains of Sweden, and hence under ex- 

 ceptionally favorable opportunities for the study of air movements. A 

 comparatively warm ocean was on one side of him and a cold continental 

 area on the other, so that he himself was on the inside, as it were, of a 

 gigantic heat engine where he could see and experience all that was 

 taking place. 



Among other things, an account is given of the movements of the wind 

 as it blows across regions covered by fine loose snow. In this case the 

 lower air, to the depth of 20 to 50 meters, becomes filled with the snow 

 in the same manner that it becomes filled with dust when blowing over 

 a desert. Now the snow obviously increases the density of the stratum 

 of air it is in, and hence this particular stratum moves up the windward 

 side of a mountain or other slope comparatively slowly and then, as 

 soon as it has passed the crest, flows down the leeward side with great 

 violence. In one observed case, this rapidly falling loaded air set up 

 great surging billows in the atmosphere at the foot of the mountain that 

 lasted. for hours, with only 10 to 15 minute intervals between perfect 

 calm and hurricane violence, and that were felt to a distance of 140 kilo- 

 meters from their place of origin. 



The second part of the paper begins with a general account of vortex 

 motion which the author makes clear by the aid of drawings and numeri- 

 cal calculations applicable to simple cases. The principles thus estab- 

 lished are then applied to the vortices of the atmosphere of which there 

 are two distinct tyiDes : Those which are roughly circular and symmetri- 

 cal, with their vortex filaments nearly vertical, and those which are very 

 unsj^mmetrical with horizontal filaments. The first obviously applies 

 to whirl-winds, tornadoes and the like, and is relatively simple, while 

 the second concerns approximately^ horizontal circulation with an upper 

 and a lower current flowing in opposite directions. This is called a 

 "gliding" vortex and the plane separating the oppositely directed cur- 

 rents a ''glide" plane. It is further explained that in general the "glide" 

 plane is more or less inclined, and suitable equations are developed for 

 the computation of the rate at which energy is being transformed in 

 such a vortex. 



A remarkable example of the "gliding" vortex commonly occurs 

 during the winter along the coast of Norway. Here a cold east wind 

 flows down the mountains and onto the ocean with great violence, while 



