PAPER BY PKOF. HELMHOLTZ. 93 



and the great and gradually increasing cyclone of the upper stratum 

 (that should otherwise be expected at the pole) break up into a large 

 number of irregular, wandering cyclones and anti-cyclones, with a 

 preponderance of the former. 



From these considerations, I draw the conclusion that the principal 

 obstacle to the circulation of our atmosphere, which prevents the 

 development of far more violent winds than are actually experienced, 

 is to be found not so much in the friction on the earth's surface as in 

 the mixing of differently moving strata of air by means of whirls that 

 origiuate in the unrolling of surfaces of discontinuity. In the interior 

 of such whirls the strata of air originally separate are wound in contin- 

 ually more numerous, and therefore also thinner layers spirally about 

 each other, and therefore by means of the enormously extended surfaces 

 of contact there thus becomes possible a more rapid interchange of 

 temperature and equalization of their movemeut by friction. 



The present memoir is intended only to show how by means of con- 

 tinually effective forces, there arises in the atmosphere ihe formation of 

 surfaces of discontinuity. I propose, at a future time, to present fur- 

 ther analytical investigations as to the phenomena of such disturbances 

 of continuity. 



