ON ATMOSPHERIC WAVES. 157 
London .... 29°59 
Boyan ne saad Under posterior slope, Crest No. 6. 
Shields .... 29-97 ) 
oe Bist snl Under posterior slope, Crest No. 6, 
Orkneys.... 29°33 J at a lower level. 
Slopes.——Lines of greatest diminution of pressure. 
Posterior slope of Crest No. 13. Christiania to Cork.... °52 
Posterior slope of Crest, No.6. London to Cork ...... *49 
A trough between crests No. 13 and 15 extends in the direction of Cork 
and Bristol*. 
Currents —Wind on S.W. side of this trough, N.W. 
i N.W. ,, Crest No. 6, S.W. 
Crest No. 6, the third of the N.W. system, now passes London five days 
after the transit of crest No. 4, the second of this system. Christiania at this 
time exhibits the greatest pressure; most probably the crest No. 13 is ap- 
proaching this station, and this, combined with crest No. 6, produces the in- 
creased pressure. At the transit of crest No. 4 Christiania exhibited the 
least pressure ; the difference may probably be explained by the transits of the 
cross waves. 
Symmetrical Wave.—London is situated under the crest of No. 6, not far 
removed from the trough, between crests 13 and 15. 
November 24, 1842. 
Crest No. 13. 
1[ 3) 2 EE eg eS 
Crest No. 6. 
S.W N.E. 
Max. Christiania.. 29°66) 
Paris: 2.0.08 29-02 
London .... 28-92 
. Plymouth .. 28°91 | 
Bristol .... 28°79 p 
Shields .... 28°78 
Cork 2. . 5S. 28°5k 
Belfast .... 28°79 
Orkneys.... 29:10) 
Max. Christiania.. 29°66) 
Orkneys.... 29°10 | 
Belfast .... 28°79 > Under posterior slope, No. 13. 
Shields .... 28°78 | 
Cork ...... 28°54) 
London .... 28°92 
* The barometric fall between the 21st and 23rd, that occurred at all the stations except 
one, appears to have given rise to an apparent regression of the trough observed in the neigh- 
bourhood of Belfast and Shields on the 22nd. It was shown that on the 22nd the anterior 
slope of crest No. 6 was coming up from the N.W., so that the fall of the 21st resulted from 
the posterior slope of crest No.9. On the 23rd the crest No. 6 passes London, and we have 
at some stations a much more sudden fall than resulted from the passage of the posterior slope 
of crest No.9. We may therefore regard the trough in the direction of Cork and Bristol as 
an indication of the approaching trough of crest No. 6, rather than a new trough between 13 
and 15. Should this view be correct, the line of greatest diminution of pressure, Christiania 
All except Christiania under posterior 
slope of Crest No. 6. 
_ to Cork, will be on the posterior slope of crest No. 9, 
