158 



REPORT — 1839. 



present, merely to register the fact, and to collect in the fol- 

 lowing table a few examples of the diiferences observed in the 

 semi-diurnal and nocturnal tides at a few places where they 

 appear to have been most accurately determined, and which I 

 have derived principally from Lieut.-Col. Sykes's valuable paper 

 on the Meteorology of Dukhun*. 



Table XII. 



18. Showing the Differences in the Morning and Evening Tides 



at various places, with the Difference from the Mean. 



Place. 





Morning Tides. 



Evening Tides. 



Ascending + 



Descending — 



Ascending -f 



Descending — 



4-5 to 

 9-10 A.M. 



Differ- 

 ence. 



9.10 A.M. 

 to 4-5 P.M. 



Differ- 

 ence. 



4-5 to 

 9-10-11 P.M. 



Differ, 

 ence. 



10-11 P.M. 

 to 4-5 A.M. 



Differ- 

 ence. 



Madras ... 

 London... 

 Poona. ... 

 Plymouth 



•0560 

 •0227 

 •0656 

 •0168 



•0470 

 •0185 

 •0445 

 •0133 



•009 - 

 •004 + 

 •021 - 

 •0035- 



•0790 

 •0289 

 •1116 

 •0166 



•023 + 

 •006 + 

 •046 + 

 •0002- 



•0630 

 •0272 

 •0884 

 •0204 



•007 + 

 •004 + 

 •022 + 

 •0036+ 



•0350 

 •0162 

 •0181 

 •0171 



•021 - 

 '•006 - 

 •047 - 

 •0003+ 







Ascending + 



Descending - 



1 



r Madras T 

 Difference of a.m. and p.m. J p°"^°" ■ 

 Plymouth 



•016 

 •008 

 •044 

 •007 



•0440 

 •0127 

 •0935 

 •0005 







We may perceive by this table that the differences in the 

 morning and evening semi-oscillations may be very consider- 

 able. At Poona, for example, the afternoon ascending tide 

 was nearly twice as great as the morning ascending tide ; in 

 order therefore to fix with precision the amount of the baro- 

 metric oscillation in different places, we require in the present 

 state of our knowledge of this question, at least an observation 

 at each of the critical hours, since the mean result in column 

 2. may differ considerably from the others, especially in a 

 limited series of observations. 



19. For perfect experimental deductions, nothing short of a 

 long series of continued hourly observations will in the present 

 state of this question suffice, since we are quite unacquainted 

 with the fluctuations which may possibly occur at different 

 periods and seasons, and in different states of the pressure ; 

 all the observations therefore hitherto made, although ex- 

 tremely valuable, must still be considered in this sense compa- 

 ratively deficient. 



* Transactions of the Royal Society for 1835. Part I. 



