Mr. W. R. Birt on Atmospheric Waves, 4;99 



of a large wave from S.W. to N.E., its amplitude being about double 

 the distance between the stations : they were of a precisely opposite 

 character, as indicated in the following table : — 



Table VI. 



M maximum. 



The line joining Belfast and Paris, the direction of crest, No. 1 on 

 the 1st, when produced, will pass near Geneva, the anterior slope 

 extending to or beyond St. Petersburgh. The numbers in the above 

 table clearly show, that when the barometer was falling at Geneva 

 from the posterior slope, it was risiiig at St. Petersburgh from the 

 anterior. On the 5th the crest passed the latter station, when tlie 

 posterior trough passed Geneva. This gives for tiie semi-amplitude, 

 or half breadth of the wave, 1365 miles; the velocity of the crest, 

 from its passing Geneva to its arrival at St. Petersburgh, being 14--22 

 miles per hour. The altitude, as measured by the mercurial column, 

 equal to -46 inch. The fall at St. Petersburgh, from the posterior 

 slope of this wave, and the rise at Geneva, from the anterior slope 

 of wave crest No. 3, is also clearly seen in the above table. 



Wave crest No. 2. — Table IV. shows that on the 5th this crest 

 extended from Cork to the Orkneys. The anterior trough of this 

 wave was also in the neighbourhood of Geneva on this day. This 

 gives for the semi-amplitude 792 miles. The altitude of the wave 

 appears to have been '76 inch, and the velocity of the crest about 

 8-25 miles per houi-. 



This wave, with its front towards the south-east, was very di- 

 stinctly developed during the early part of November. The altitude 

 of the crest appears to have subsided as the wave progressed ; the 

 highest reading at Belfast w<is 30"55 on the 5th, at London 30-16 

 on the 6th, and at Paris '29-90 on the 8th. The following tables 

 exhibit the features of the anterior slope. Table VII. shows the 

 barometric rise and fall at stations arrangetl more or less with re- 

 gard to a line cutting the crest of the wave transversely. The de- 

 pres.sing influence of tlie wave, crest No. 1, is clearly seen at London 

 and Paris on the 5th. Tables VIII., JX. and X. exhibit the depres- 

 sion of the south-easterly stations below those to the north-west of 

 them while the anterior slope passed. 



2 L 2 



