168 REPORT—1846. 
Orkneys. This will give some idea of the extent of country covered by this 
wave and the vast amount of its amplitude. The direction of the trough is 
indicated on plate 42, Report, 1844. i 
November 11. Posterior troughs, crests Nos. 2 and 3.—On Nov. 5 we 
distinctly traced the directions of the crests Nos. 1 and 2, and the observa- 
tions at St. Petersburgh assisted us in indicating the locality of their inter- 
section. The observations of this day, Nov. 11, indicate the contemporane- 
ous existence of the posterior troughs of crests Nos. 2 and 3. 
It appears probable, from a consideration of the observations of November 
12, that the depression which occurred at Plymouth (sce page 150) was oc- 
casioned by the crossing of the posterior troughs of crests Nos.2 and 3. If 
so, we are enabled to form a correct estimate of the direction of these contem- 
poraneous troughs. The posterior trough of crest No. 2 now passes St. 
Petersburgh. Table IX. (Report, 1845, page 125) clearly indicates that the 
depression of this day, in the south of England, was due to the posterior 
trough of crest No.3. We find Paris under the posterior slope of crest No. 2, 
so that the intersections of the troughs must have been situated in the neigh- 
bourhood of Plymouth, or between Cork and Plymouth: the direction of the 
trough of crest No. 3 appears to have extended from Paris towards Cork 
while the crest was passing Christiania. It appears the velocity of crest No. 
3 was greater than that of crest No. 1, which may, to a certain extent, explain 
the discrepancy noticed in page 150. 
November 12. Crest No. 3.—This crest now passes St. Petersburgh, while 
its posterior trough passes Belfast and Shields. 
November 15. Anterior trough, crest No. 5.—This trough now transits 
St. Petersburgh. The fact of the succeeding crest (No. 5) passing the Ork- 
neys at the same time, clearly indicates the wave to be much smaller than the 
preceding two. 
November 17. Crest No.’7.—It appears from a comparison of the Chris- 
tiania and St. Petersburgh observations that the wave, crest No.7, was very 
small. 
November 18. Crest No. 4.—This wave, which forms the crown of the 
great symmetrical wave, has been very distinctly developed by the discussion 
of Mr. Brown’s observations. The altitude it attained, especially in the 
south-east of England, has contributed to bring it prominently into view. 
The observations at St. Petersburgh make us acquainted with the great ex- 
tent of its longitudinal direction. Its crest passed Dublin on the 17th, Lon- 
don on the 18th, and Munich on the 19th (see plate 2, appended to Sir John 
Herschel’s Report on Meteorological Reductions, Report, 1843). In the fol- 
lowing table the transit of its crest at the three northern stations, the Orkneys, 
Christiania and St. Petersburgh, is readily seen. The direction in which the 
wave progressed being N.W. to S.E., the section which passed over St. Peters- 
burgh was more northerly than the others. The maximum occurred at St. 
Petersburgh at least twelve hours later than at Munich, and about two days 
later than at Dublin. 
Taste XVI. 
Epoch. Orkneys. Christiania. | St. Petersburgh.| 
Nov.17 |  30:35° 29:94 | 29-68 
18 30:18 30-11° 29-85 
19 29:91 29°91 30:16¢ 
© Crest. 
[For Addenda to this Report see end of the Reports. |- 
