ON ATMOSPHERIC WAVES. 129 
Taste III. 
Distinct, well-marked transits. Doubtful transits. 
Year. Epoch of crest. Value. Year. Epoch of crest. Value. 
1837 Noy. 6 30:20 1833 Noy. 13 30:03 
1831 12 30°32 1830 23 ' 30:12 
1835 12 30°40 1839 23 30:13 
1838 12 30°36 1840 26 30:23 
1845 13 29°87 
1834 14 30°48 
1843 14 30°27 
1829 16 30°47 
1832 16 30:21 
1842 17 30°35 
1841 25 | * 29-79 
From the above table it appears that with two exceptions in eleven years 
ot distinct and well-marked transits of the great wave, the epochs of the maxima 
were confined to five days near the middle of the month, namely from the 
12th tothe 17th. The greater proportion, twelve years out of seventeen, in- 
cluding 1844, in which the wave has distinctly returned, greatly confirms the 
results noticed in sec. XJ., namely that we have obtained the type of the 
barometric movements during fourteen days in November, more or less equally 
disposed about the middle of the month. 
I cannot here avoid noticing another feature of a most interesting character 
which isvery strikingly developed in these curves of November; itisapparently 
unconnected with the great wave. I allude toa general tendency to depres- 
sion in the mercurial column about the last four or five days in the month: 
the following are the years in which this depression occurred :— 
TaBLeE IV, 
och of 
Year. | Bal ren Value. 
1829 Barometer falling. 
1830 Nov. 27 29°40 
1832 28 29:19 
1833 28 28:31 ‘ 
1834 28 28-97 r 
1835 30 28°86 
1836 27 28°81 
1837 28 29-26 
1838 28 27°77 
1839 29 29-08 
184] 29 28°47 
1842 24* | 28-38 
; 1843 26 | 29-15 
BA 1844 28 29-74 
ei 1845 29 29-08 
ee. * A minimum occurred on Nov. 27, value 28°56. 
__ This depression has occurred so regularly, only two exceptions having been 
“observed in seventeen years, that it appears highly probable that its return 
may be expected with as much if not more regularity than that of the great 
wave itself, on or near the 28th of the month. 
(1846. kK 
