ON ATMOSPHERIC WAVES. 195 
TasBLe XI. Wave B°. 
Barometric Differences arising from the Anterior and Posterior Slopes of B®. 
Epochs. |Longstone.| Scilly. Scilly +. Phases. 
1842, ewe 
d h | in. in. in, 
Noy. 6 _ 30°316 | 30°276 |— -040 | Anterior trough. 
306 |m *324 | + -018 
7 3 266 283 | + -017 
9 “215 270 | + -055 
15 | 30054 |m -241 |+ -187] . 
21 | 29-983 |m -273 |+ -290| 2 
8 3] -889 170 |4 -281 | 3 
9} °-747 | 30-066 |+ -319| x 
15 470 | 29849 | 4 °379 | “E 
21 +296 702 |-+ -406} = Greatest curve of 
9 2 m ern m oe £ a <i; _ anterior slope. 
te : 
5 426 553 ;-+ -127 | Crest. 
21 570 491 | — -079 |x 
10 : M a ae 7 oo § g. Greatest curve of 
15 | 286 |). 081 | — .-205. |. ra, Posterior slope. 
21 | 29:164 |m -061 | — -103 Pasteniet h 
11 3 | 28-990 | 29-081 | + -og1 | * OSetor trough. 
This Table exhibits the barometric differences arising from the passage of 
that section of B° which passed the extreme stations of the line given on page 
277, Report, 1844. In order to investigate the entire transit of this wave, it 
will be requisite to commence the examination of the distribution of pressure 
over the area at least two days earlier than the epoch chosen last year, namely, 
Noy. 6:15 instead of Nov. 8:15; and this is the more desirable, as during eight 
days previous to this epoch (Nov. 6:15) the barometer had maintained an 
altitude (with only one exception) above 30 inches. See Plate I. illustrating 
Sir John Herschel’s ‘ Report on Meteorological Reductions’ (Report, 1843). 
The table shows a very considerable fall during the transit of the anterior 
slope of B®. Now should there be no counteracting influence in operation, 
or in other words, should only one wave be passing, the barometer must rise 
during the transit of as anterior slope. We are therefore prepared, in accord- 
ance with the views advanced relative to the intersection of curves, to find 
another large wave moving in a different direction; and a comparison of the 
reducedaltitudes at Glasgow, Bardsey, South Bishop, Birmingham, Greenwich 
and St. Catherine’s Point, indicates that such a wave traversed the area, its 
erest passing the line joining Scilly and Bardsey Nov. 7:21, and its trough 
Nov. 9:3: this trough has already been noticed. .The details of this wave 
will be presented to the Association on a future occasion. By commencing 
the examination at this earlier period, we shall include the whole of the 
barometric movements immediately succeeding the state of comparative re- 
pose during the eight days already alluded to: the first great disturbance is 
evidently of a negative character, producing a great depression of the barome- 
ter, this was followed by those undulations which gave rise to the symmetrical 
wave exhibited in the diagram, and shown in Plate II. (Report, 1843). An- 
other advantage resulting from the earlier commencement of the investiga- 
tion, is that the complete transit of the wave producing the bulge noticed in 
the last report, (3.) (4.) (5.), page 271, is traced completely across the area. 
The principal phases of B° are given at the foot of p. 124. 
Wave Al. 
“A careful comparison of the reduced altitudes at Glasgow, Bardsey, Bir- 
