ON ATMOSPHERIC WAVES. 43 
ometer in that part of Europe; its presence is very distinctly marked, 
ten, Christiania and St. Petersburgh being nearly on a level: the order of 
altitudes i is as follows :— 
CCHPISHATAIAM res SMe lelb dle Res. BOB 7 
PRTECTIby tie Cae AER: Seen es CRM a ee 30°29 
Bhs (PPRUSES DURE. feieihis) wi9/0's on s6aje de ape, Sf MRO 
We have consequently the area of greatest pressure approaching the central 
aan of Europe from the north-west ; the Scandinavian wave, which raises 
i e barometer in the north-east, being considerably in advance of that of 
Central Europe, crest No. 2, which contributes to the rise in the south-west. 
__ Noy. 5. On this day we have the turning-points of the opposite curves, 
Geneva and St. Petersburgh (see fig. 10, pl. 27, Report, 1847) ; they clearly in- 
dicate the half-span or semi-amplitude of the wave-crest No. I, the crest being 
vertically over St. Petersburgh (max. ) while the trough transits Geneva (min). 
The semi-amplitude is consequently 1365 miles, ‘and the velocity of the 
_ crest, as determined from the epochs of its passing Geneva and St. Peters- 
burgh, 14-22 miles per hour. ‘This wave appears to have been rather larger 
than its successor, wave-crest No. 3 or B®, the elements and phases of which 
"are given on p. 124, Report, 1845. 
__ The rise at Alten on this day, on the steep posterior slope of the Scan- 
-dinavian wave, enables us to extend the line of crest No. 2 from ks the 
Biiituced reading at Alten, 30° 14, clearly itdivales that the greatest swell 
eeurred in Central Europe: the readings along the crest are as follows :— 
Cork, 30°32; Belfast, 30:55; Orkneys, 30°52; Alten, 30°14. 
From these numbers we learn that the greatest swell occurred in the north- 
east of Ireland, and that the wave thinned off very considerably towards 
Alten, being perceptible as a subordinate maximum only. Had not wave- 
-erest No. 2 extended to Alten, the barometric differences between Alten 
d St. Petersburgh would have been much greater. The crests Nos. 1 and 
intersected to the north-west of Norway. See Report, 1846, p. 167. 
_ The area of greatest pressure has much the same direction as on the 4th, 
‘extending from ¢ the south-west of Ireland across Scotland and the Seauiiie 
avian peninsula to St. Petersburgh. ‘The greater swell of the wave-crest 
. 2 in the neighbourhood of Ireland and Scotland contributes to the high 
ometric readings in those localities ; the intersections of crests Nos. 1 and 
the high readings in the southern parts of Norway ; and the intersection 
the Gendinavian crest a with No. 1 to the altitude, as observed at St. 
etersburgh. The distribution of the crests is as follows :— 
indinavian crest a..To the west of and approaching St. Petersburgh. 
Crest No.2 ........Extending from Ireland to Alten. 
C 1 ........Crossing each of these on a line to the north-east of 
that terminating the Scandinavian wave longitu- 
dinally. 
ndinavia and Russia are now covered partly by the anterior and partly 
the posterior slopes of the Scandinavian wave ; Northern Central Europe 
the posterior slope of crest No. 1, and Western Europe by the anterior 
pe of crest No. 2 
‘he lowest en: on this day, with the exception of Lougan, is Geneva, 
79, the posterior trough of crest No. 1. It is probable that the troughs 
