116 REPORT—1845. 
The barometric curve accompanying the Greenwich observations for 1840 
and 1841, exhibits a considerable interval between the minima of January and 
February in the latter year; this interval is 36 days, and may be advantage- 
ously compared with a long interval between the maxima of September 19 
and October 21, of 31 days 16 hours. This long interval is remarkable for a 
considerable and symmetrical depression of the barometer, nearly midway 
between the two maxima, namely from October 5,22 hours 57 minutes to 23 
hours 55 minutes ; the reading uncorrected for sea level was 28°697. If we 
consider the point equally distant from the January and February minima to 
be the summit of a normal wave, we shall have the epoch of its transit January 
28:18: now the period from this apex to the depression in October will equal 
250 days. The middle point of this period falls on the 2nd of June; on the 
3rd of June, 22 hours, the barometer passed a maximum. On each side of 
this maximum are 6 maxima with a mean interval of 14 days 1 hour. It is 
interesting to observe, that the minimum of the 16th of February, and that 
of the 5th of October, are the boundaries of the period of least range; mean 
range for the seven months 1:029. Upon the hypothesis that the maxima were 
the crests of waves, it appears that during the period of least range sixteen 
waves traversed England, having a mean interval between their crests of 14: 
days 5 hours. The column of intervals clearly exhibits a considerable regu- 
larity in the succession of these waves, as well as their symmetrical position 
relative to the axis, and their altitudes support the same idea. Taking the 
middle wave June 3 : 22, we find corresponding altitudes on either side; thus 
the highest wave passed Greenwich on March 10: 22, altitude 30°572. Six 
waves on the other side of the axis, we also have the highest reading, namely 
August 26 : 10, altitude 30°353. The following Table places this regularity 
both as respects altitudes and intervals in a clearer light. 
Taste IV. 
Altitudes of Waves equally distant from the Axis, June 3:22. 
; Mean Mean 
Wave. Epoch. Altitnde. Altitude. | Interval. 
th. |March ...... 2 : : 
August...... 26 10)  -353 ¢| 20°62 | 14 1 
5th. |March ...... 24 0 329 
August...... 12101 -olos| 30169 | 14 8 
ve Titty co, 34 10) aap f] 80217 | 12 18, 
SN ffaiywccce, 8 13] up {| 80009 | 12 8 
mjunes 87 14] 79 f| 80810 | 
eT, 18 22] aay f] 80874 | 1118 
Axis, [June......... 3 22| 30-426 
On pursuing the investigation beyond the period of least range and ex- 
tending it into that of the great winter oscillations, the same regularity of 
perturbation is still apparent; there appears to be a symmetrical movement 
