26 Mr. W. Stevenson on the Aurora, and the connexion which 



Comparing proportionally the directions of the cirrous bands 

 and fibres, 1841 to 1847 inclusive, we have the following result : — 



N.E. N.N.E. N. N.N.W. N.W. W.N.W. W. W.S.W. 



to to to to to to to to Sum. 



S.W. S.S.W. S. S.S.E. S.E. E.S.E. E. E.N.E. 



Bands 31 75 80 82 98 72 21 7 466 



Fibres 27 74 109 69 79 64 35 7 466 



The connexion of the direction of the cirrous bands with the 

 weather appears to have been long observed. I have heard 

 the following couplet popularly applied to the phenomena in 

 question : — 



" North and south, the sign of drouth (drought), 

 East and west, the sign of a blast " (storm). 



Some years ago, in a communication to the Philosophical 

 Society of St. Andrews, I stated my opinion that the direction 

 of the progressive motion of revolving storms or u cyclones " was 

 the same as that of the upper currents for the time being, as 

 indicated by the motions of cirri. My observations since have 

 tended to confirm me in this opinion. It must, however, be 

 taken only as approximately true, since the upper regions of the 

 atmosphere are also affected by cyclonic movements, but appa- 

 rently of longer period and of greater extent than those which 

 prevail upon the surface of the earth. The proper ascertainment 

 of this point would be of great interest as well as of much prac- 

 tical utility. 



III. Cirrostrati. 



These clouds resemble cirri in their tendency to an arrange- 

 ment in long parallel bands ; they differ, however, from them in 

 not being composed of ice-crystals. They appear very frequently 

 as concomitants of the aurora, so much so as to leave no doubt 

 of a connecting influence between them and that phsenomenon. 

 They also prevail in dry, windy weather, occupying a stratum in 

 the atmosphere above that in motion. I have frequently ob- 

 served during a gale from S.W., cirrostratus bands extending in 

 a N.W. to S.E. direction, and moving from S.W. so slowly that 

 it required some time to determine whether they moved at all, 

 whilst immediately under them light cumuli were flying at a 

 tremendous rate. The cirrostratus condition of cloud appears 

 to be induced upon masses of vapour, by the influence of the 

 electricity developed by the friction of currents of dry air. On 

 one occasion, a few years ago, upon a gusty, showery day, I ob- 

 served that when the wind fell, the cirrostratus clouds overhead 

 immediately became hazy and ill-defined, passing into the nimbus 

 type, and rain followed. This continued until the wind again 



