4 
ON ATMOSPHERIC WAVES. 147 
November 9, 1842. 
Crest No. 2. 
S.W. N.E. 
Posterior slope, Crest No. 2. 
Max. Paris...... 29°76 Belfast .... 29°41 
Plymouth .. 29°72 Christiania... 29°37 
London..,. 29°70 Shields .... 29°28 
Bristol .... 29°60 Orkneys.... 28°80 
orks: S18 a 29°42 
Slope.—Line of the greatest diminution of pressure. Paris to Orkneys, ‘96 
Current.—Wind on N.W. side of crest, S.W., fully established. 
The posterior slope of crest No. 2 now comes into full view, stretching 
from Paris to the north-west coasts of Ireland and Scotland, with its proper 
wind S.W. The altitude of this slope from the Orkneys to Paris is *96. 
The greatest altitude of the anterior slope, from Paris to Belfast, was °80. 
It will be seen that the greatest oscillation has been in the north-west, Paris 
exhibiting but a very slight oscillation, 17, while that at the Orkneys has 
amounted to 1°72. 
The following table exhibits the fall of the barometer on the 8th and 9th: 
TasLE X.—Fall of Barometer, November 8 and 9, 1842. 
Station. November 8. | November 9. 
| Orkneys........00. “52 83 
Christiania........ 35 30 
39 63 
30 69 
32 59 
‘ll AZ 
‘ll Al 
05 38 
+01 14 
From these numbers we learn that the greatest barometric fall, as well as 
_ the greatest oscillation, occurred in the N.W. The fall gradually decreases 
as we approach the S.E. 
It appears to me that the difference of oscillation at two stations, as the 
Orkneys and Paris, may be thus explained. The curves in the north-west 
_ of Ireland, as determined by the discussion of Sir John Herschel’s hourly- 
_ Observations, are remarkable for boldness and freedom of contour and great 
range of fluctuation. The late Professor Daniell found, from an examina- 
_ tion of the Manheim observations, that the range increased towards the north- 
_ west, and that the greatest oscillation occurred in the neighbourhood of water. 
_ Now a wave generated in any way and approaching the continent of Europe 
_ from the north-west, would most probably impinge on it with a high and in 
i some cases acuminated crest 5 Veale but as it passed onward 
the crest would gradually subside Cee et ea tis) gy BO Ga eae eae 
ae considerably to the south-east the fluctuations would be very much 
less than at or near its point of genesis. Again, a negative wave, with a 
deep trough also approaching from the north-west , would 
present large fluctuations as it impinged on the land; but after passing on- 
L2 
