Mr. W. R. Birt on Atmospheric Waves. 

 tlestdts of the Discussion of Mr. Brown's Observations. 



495 



In collecting the results of this discussion, I have arranged In Tables 

 II. and III. the principal lines of diminution of pressure ; the suc- 

 cession of waves as well as the distinct systems become very apparent 

 from these tables. The succeedingTablesIV.and V.exhibit the prin- 

 cipal features of the respective waves of each system. The most pro- 

 minent result appears to be the confirmation of Prof. Dove's sug- 

 gestion of parallel and oppositely directed currents. The diagrams 

 of the wind in connection with the barometric observations clearly 

 exhibit such currents, and we see by a glance at Tables IV. and 

 V. that the beds of these currents varied considerably in breadth. At 

 the opening of the observations they were very much broader than 

 at the closC; and the N.W. system (waves No. 2, 4, 6) were alto- 

 gether larger than the S.W. We have in fact two systems of waves 

 or currents crossing each other at right angles, the individuals in 

 both gradually decreasing in size. In the speculation which has been 

 ventured relative to the S.W. system, the mass of terrestrial surface 

 forming the N.W. boundary of the great eastern continent has been 

 assumed as the rarefying surface, producing the set of pai'allel and 

 oppositely directed S.E. and N.W. winds, the currents gradually 

 shifting towards the N.E. The gradual contraction of the beds of 

 each system as the observations proceed is a highly interesting fea- 

 ture, which requires a more extensive discussion for its elucidation. 



Tabi-e II. — Exhibiting the principal lines of the greatest diminu- 

 tion of pressure of the N.W. system of waves, Nos. 2, 4, and 6. 



