128 REPORT—1846, 
replacing the great wave, they are characterized by the most remarkable 
absence of the central undulation forming its crest; two of the subordinate 
undulations, equally posited with regard to the anterior and posterior troughs, 
are strongly and strikingly developed; and where the central undulation 
should have occurred, raising the apex above thirty inches, a great depression 
is seen. 
1837. The great wave well-developed ; the last posterior subordinate wave 
strongly developed. 
Transit of anterior trough, Noy. 1 or Oct. 31. 
Transit of apex ........ yee) 
Transit of posterior trough ,, 14 
Amplitude in time, fourteen days. 
1838. The similarity between the curve of this year during the transit of 
the great wave and that of 1842 during the same period is very striking ; the 
anterior slopes in each case are almost representatives of each other ; the two 
subordinate waves on the anterior slopes are so nearly identical as to leave no 
doubt of the movements of 1842 being a most decided return of those of 1838 ; 
the similarity of the subordinate waves on the posterior slopes is not so distinct, 
the two are however well-marked. One striking difference between the 
curves must nevertheless be noticed ; in 1838 the anterior trough was lowest, 
in 1842 the posterior was lowest. 
' Transit of anterior trough, Nov. 7. 
Transit of apex ........ lee 
Transit of posterior trough ,, 21. 
Amplitude in time, fourteen days. 
1839. The great wave in this year is very difficult to recognize. A maxi- 
mum was passed on the 23rd, subordinate waves were developed on each 
side this maximum. There appears to be some similarity in the movements 
of this year to those of 1830, the subordinate waves are however not so 
distinct. Transit of apex, Nov. 23. 
1840. In this year also the great wave is difficult to detect unless the broad 
maximum of the 26th forms its crest, in which case the posterior slope runs into 
December ; this is borne out by the Greenwich observations, they however ex- 
hibit a large development of one of the subordinate waves on the posteriorslope. 
In the following table all the above features are collected. The amplitudes 
(in all cases except two being of the same extent, namely fourteen days) 
strongly confirm the views advanced. These views receive still greater con- 
firmation from the epochs of the transits of the crests, which are arranged 
according to the days of the month on which they occurred in Table III. 
Taste II. 
Posterior |Amplitude Remarks, 
trough. in time, 
Anterior 
trough. 
1829 Noy. 23 14 Very distinct. 
1830 NKeeshsaed ailtssnasees Symmetry not so apparent. 
1831 15 9 Symmetry clearly observable. 
1832 23 14 Symmetry very distinct. 
1833 21 14 Wave very difficult to recognize. 
1834 21 14 Very distinct, 
1835 21 18 Very distinct. 
1836 sevesecest) llibansdats vecote ff oesovcwoge Extremely difficult to recognize. 
1837 14 14 Well-developed. 
1838 21 14 Similarity between 1838 & 1842 ; 
very great. 
VESD 4) vecsscossasee liste pereiwi|\seku ene sasneli| teascocens Wave very difficult to recognize.) 
BOAUle\Vovercnsececs (teiuseenatncee | lessueoncater ecoreesan Difficult to detect. 
