ON ATMOSPHERIC WAVES. 271 



appears to have passed through Geneva and Brussels, and a continuation of 

 this line would pass to the north-east of Longstone ; the highest blue curve a 

 in fig. 2, Plate XLIV., will give the approximate form of the slope of this part 

 of the wave, Nov, 8.21 hours. At 8.15, six hours earlier, a line joining Scilly 

 and St. Catherine's Point appeared to be somewhat parallel to the crest of 

 the wave ; the slope could not have extended much further than Dublin, 

 the slope from Dublin to Longstone being only "093. 



(3.) Wave B 1 appears to have flowed from Scilly towards Longstone ; the 

 highest blue curve a, in fig. 1 , Plate XLIV., will give an approximate form of 

 the slope of this part of the wave (or rather the form of the atmosphere on this 

 line, arising from a combination of the two waves, A 1 and B 1), for at 8.15 

 the remarkable bulge in the neighbourhood of South Bishop appears to have 

 been a portion of wave A 1, which at that time was passing South Bishop 

 from the N.W.* 



(4.) Nov. 8.21. — Wave A 1. The highest blue curve a, in fig. 2, Plate 

 XLIV., gives the approximate form of the slope of this wave from Geneva to 

 Brussels. The highest blue curve a, in fig. 3, gives an approximate section of 

 this wave from Brussels to Dublin, crossing the section of wave B I, in fig. 1, at 

 01 in fig. 3. Dublin is now at a minimumf. The bulge which characterized 

 the line from Scilly to Longstone in fig. 1, curve a, appears very conspicuously 

 in this curve between Birmingham and Dublin. The three curves in fig. 3 

 exhibit the variations in the pressure at the stations Brussels, Birmingham 

 and Dublin ; during the twelve hours from Nov. 8.21 to 9.9, the bulge appears 

 to be peculiar to Birmingham ; and the minimum, as it advances, appears to 

 run up the slope, and not to pass onwards at the same level. 



(5.) Wave B 1. — The progression of the bulge towards the S.E. left the 

 gradual and gentle slope as exhibited in fig. 1, curve b, Plate XLIV., and this 

 either formed a portion of the slope of wave A 1, or of a normal wave, or 

 resulted from the permanent depression before alluded to. It is worthy of 

 remark, that the fall of the slope accompanies the progression of Avave A 1 J. 



(6.) Model for this term gives a general idea of the slope of wave A 1, 

 from a line joining Brussels and Heligoland to a line joining Dublin and 

 Longstone. 



(6*.) Nov. 9.2. — Dublin and Bardsey at the same level, the atmosphere 

 rising to South Bishop and Scilly, and dipping to Longstone ; this equality 

 of level is occasioned by the passage of the trough of A 1 . See coloured 

 diagrams, fig. 2, Plate XLIII., intersection of Dublin and Bardsey curves, 

 near m. 



(7.) Nov. 9.3. — The minimum has now passed Dublin, and a trough exists 

 between Dublin and St. Catherine's Point ; minima now exist at Longstone, 

 Bardsey Island, South Bishop, and Scilly, so that the trough of the advancing 

 wave A 1 extends in the line from Scilly to Longstone, with a dip of "369 to 

 Longstone. The minima at Longstone, Bardsey, and South Bishop, appear 

 to be produced by the posterior trough of A 1, and the minima at Scilly and 

 Geneva by the anterior trough of B 1, see Plate XLII. ; if so, the curve c, 

 fig. 1, Plate XLIV., must exhibit, not the anterior slope of B 1, but a slope 



* From the consideration that the minimum at Scilly at 9.3 was occasioned by the 

 anterior trough of B 1, the curve a, fig. 1, could not have represented any portion of the an- 

 terior slope of this wave. It is most probable that the curve resulted from a combination 

 of the slope of A 1 with the bulge, and the slope arising from the permanent depression. 

 See (5) and (7). 



t The observed minimum occurred at Dublin Nov. 9.1.0. 



X At this time wave B 1 had not entered on the area. 



