Mr. W. R. Birt on Atmospheric Waves. 137 



Fifth zone above trough, posterior slope. S.W. wave. 



Barom. Direction. Force, 



Brussels . . 29-G8 + 0-18 S.W. -3 



Yarmouth . . 29-54 + 0-16 S.S.E. -3 



Scarborough . 29-45 + 0-.13 S.W. 3 



Shields . . 29-42 + 0-10 S.S.W. 3 



Leith . . . 29-40 + 0-09 E. -3 



Sixth zone above trough, posterior slope. S.W. ivave. 



Helder . . 29-61+0-18 S.W. +5 



Aberdeen . . 29-44 + 005 S.E. 3 



Nairn . . . 29-43 + 0-04 E.S.E. 2 



Wick . . . 29-50 + 0-04 S.E. 4 



Thurso. . . 29-47 + 001 E.S.E. 2 



Seventh zone above trough, posterior slope. S.W. wave. 



Cuxhaven . . 29-67 + 0-13 S. 3 



0x0 . . . 29'67 + 0-ll E.N.E. 4 



Skudesnaes . 29-62 + 0-10 S.E. +4 



Christiansund . 29-61 + 0-09 Calm 



This Table is one of the most interesting of the series; it ex- 

 hibits a general rise of the barometer over the entire area^ and 

 the establishment of the posterior slope of the N.W. wave^ the 

 direction of the trough of which has been specified in Tables 

 111., IV., and V. It would appear at first sight that the wave 

 had progressed towards the N.W.; but it is likely that this ap- 

 pearance arose from the irregularity of increase of elasticity 

 being greatest along the English Channel. It is, however, 

 noteworthy that with the extension of the trough towards the 

 N.W., or in other words, of zones of decreasing pressure from 

 the crest towards the N.W., the winds in the N.W. should be 

 those of the S.W. w^ave, the zones of which are given in the 

 Table. Space prevents the further discussion of the barometric 

 curves and sections, which are capable of yielding a valuable har- 

 vest of results ; but as the Tables contain the heights of the ba- 

 rometer and their differences for each day, the reader can easily 

 construct them for himself; indeed this course is recommended 

 for the elucidation of the preceding Tables. 



In the year 1843 the late Sir John Herschel, writing on the 

 subject of barometric fluctuations, said "it would be no*small 

 meteorological discovery if by the study of the characters and 

 progress of barometrical fluctuations we could either make out 

 any law of the greater ones which would enable us even roughly 

 to predict them, or any peculiarity in their physiognomy by which 

 we could recognize them in their earlier stages, as by this we 



