ON ATMOSPHERIC WAVES. 273 



that the trough had made no progress since Nov. 9.3*. I am however in- 

 clined to consider that, as it passed Bardsey at this epoch (Nov. 9.3.), it 

 would have passed the intersection of the line from Birmingham to South 

 Bishop at 9. It is probable that the altitude at the point of intersection should 

 be less than given in the model ; if so, the two troughs, posterior A 1 and 

 anterior B 1, would nearly coincide, and Bardsey being the nearest station of 

 observation, would give the lowest reading. Upon this view we shall have the 

 flowing on of the two waves ; the rise at Scilly from 3 to 9, being produced 

 by the joint action of waves A 2 and B 1, and that at South Bishop also, while 

 at Bardsey the rise from 3 to 9 is due only to the anterior slope of A % and 

 B 1 does not occasion any rise at this station until after 9 hours. The supe- 

 riority of the Dublin to the Bardsey curve, Plate XLIII., fig. 2, indicates that 

 the two stations are situated under the anterior slope of A 2. Upon com- 

 paring this model with the two former, the approach of the area to a level is 

 very apparent, although the slope is generally in the same direction as in 

 the former models. 



(17.) Nov. 9.9. — St. Catherine's Point and Scilly approach nearly to a 

 level, as the trough of B 1 passes St. Catherine's while the maximum is pass- 

 ing Scilly. See (15.) The curve at St. Catherine's Point, fig. 2, Plate XLIII., 

 exhibits a very small rise ; probably the trough of A 1 has tended to depress 

 the maximum of B 1. 



(18.) Nov. 9.13.30 (about). — Scilly, South Bishop and Dublin at the same 

 level with South Bishop near its maximum. 



(19.) Nov. 9.15. — Wave A 1. The trough of this wave appears to be still 

 between St. Catherine's Point and Dublin. 



(20.) Wave B 1. — The apex of this wave now passes over St. Catherine's 

 Point and Bardsey. Curve e (redf ), fig. 1, Plate XLIV. exhibits this apex, also 

 the anterior trough between Bardsey and Longstone noticed in (15.). 



The annexed figure represents an approximate transverse section of wave 

 B 1 as it passed South Bishop and Bardsey. 



Bardsey. South Bishop. Scilly. 



Altitude of wave -090 measured from the slope from Scilly to Longstone. 

 (21.) Nov. 9.15.30. — Scilly and Bardsey on a level, with South Bishop 

 rising between them. Dublin is still rising, most probably from the anterior 

 slope of wave A 2. 



* The progression of the anterior trough of wave A 2 is cleariy seen in the annexed 

 section from Dublin to St. Catherine's Point at 9.15. 



72 miles. 



Dublin. Bardsey. St. Catherine's Point. 



Section of anterior trough of A 2 at 9.15. The transverse section of B 1 for the same epoch 

 cuts tills line, and indicates that that wave was moving along this trough. See (20.) 



t Figs. 2 and 3, Plate XLIII., have not been coloured, the tinting of the spaces under each 

 curve answering the same purpose. The term "coloured" is retained in the Report as indi- 

 cating that the original diagrams which accompanied it were coloured, and also for the pur- 

 pose of more readily referring the reader to these particular diagrams. 



In the explanation of Plate XLIV. the colours of the curves have been retained for the 

 same reasons. In the original of this plate blue curves represent the barometer descendiny, 

 and red curves the barometer ascending. 



184.4.. T 



