Ml*. W. R. Birt on Atmospheric Waves. 



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



Barom. Direction. Force. 



Ardrossan . . 29-66 -0-42 E.S.E. +5 



Liverpool . . 29-69-0-3i S.E. -2 



Portsmouth . 2971 -0-21 N.E. 3 



129 



Fifth zone above trough. S.W. ivave, posterior 



' slope 



Thurso . . . 



29/9-0-24 



E.N.E. 



-2 



Wick . . . 



29-81 -0-22 



E.S.E. 



3 



Nairn . . . 



29-76-0-31 



E. 



+ 2 



Aberdeen . 



29-77-0-20 



N.N.W. 



--2 



Leith . . . 



29-73 -0-32 



S.E. 



3 



Shields . . . 



29-73-0-25 



S. 



-2 



Scarborough . 



29-74-0-19 



S.S.E. 



-1 



Yarmouth . . 



29-75-0-12 



N.E. 



4 



London . . 



29-73-0'18 



E.N.E. 



3 



Dover . 



29-71-0-12 



E.N.E. 



4 



Cape Gris Nez. 



29-72-0-10 



E. 



-4 



Brussels . . 



29-72-0-07 



N.E. 



3 



Paris . . . 



29-65-0-17 



N.N.E. 



2 



Charleville 



29-66-0-14 



N.E. 



3 



Lyons . . . 



29-55-0-14 



N. 



+ 3 



Toulon . . . 



29-44-019 



E.N.E. 



+ 7 



The column of barometric differences shows the rise or fall of 

 the mercury since the preceding day, while the + and — signs 

 in the column of force indicate an increase or decrease of strength 

 as compared with that of the preceding day. 



While a general fall of the barometer was recorded at every 

 station, it was greatest in Ireland and least in Belgium — a result 

 obtained in my former researches. This fall could not have re- 

 sulted from the progression of the waves ; for we find the pro- 

 gression of both well marked, the crest of the N.W. wave extend- 

 ing along the English Channel and that of the S.W. wave along 

 the eastern shores of Great Britain; yet along each crest the 

 barometer had fallen. The fall must have resulted from an 

 irregular change in the elasticity of the air, which commenced 

 most probably near the western shores of Ireland, where the di- 

 minution was greatest. In this locality it assumed the form of 

 a cyclone, not of very great force, but still well marked so far as 

 the circulation of the wind was concerned. The cyclonic winds 

 are distinguished in the Table by an asterisk (*). There are 

 one or two note-worthy features in the Table, particularly the 

 approach to an equality of pressure in that part of the fifth zone 

 extending from Thurso to Brussels, in which portion we have 

 tlie highest pressure (29'81) at Wick with a fall of 0*22 since the 



Phii. Mag. S. 4. Vol. 44. No. 291. Avg. 1872. K 



