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IX. On the Tides. By J. W. Lubbock, Esq. V. P. and Treas. R,S. 

 Received December 16, 1833, — Read February 20, 1834. 



X HAVE already presented to the Society some tables exhibiting results obtained by 

 the discussion of many observations of the tides made at the London Docks. I have 

 now to communicate other tables, also calculated, according to my instructions, by 

 Mr. Dessiou. In those already published in the Philosophical Transactions, which 

 have reference to the corrections due to the influence of the parallax and declination 

 of the moon, Mr. Dessiou employed only observations of the tides made between con- 

 junction and opposition ; but considering it of importance to establish these correc- 

 tions upon a greater number of observations, and also to ascertain whether any appre- 

 ciable difference existed, Mr. Dessiou undertook to obtain similar corrections from 

 observations made between opposition and conjunction. The difference, if there be 

 any, is very small. 



It formerly escaped my notice, that the correction due to the influence of the 

 moon's declination is mixed up with that for the calendar months : but the inclina- 

 tion of the moon's orbit to the ecliptic is small ; and when observations are considered 

 throughout an entire revolution of her node, she may be taken to move in the ecliptic ; 

 so that her time of transit being given on any day of the year, her declination is also 

 given. This suggestion was made to me by Mr. WheWell, and I have endeavoured 

 to remedy this difficulty, and have now calculated the correction for the calendar 

 months roughly, which may serve until there has been time to obtain it with greater 

 precision. 



My corrections for the influence of the moon's parallax and declination may, I 

 think, be safely adopted ; and I doubt if they be susceptible of much further improve- 

 ment. Their discrepancy from the theory of Bernoulli is worthy of remark, as may 

 be seen in the following Table, which gives Bernoulli's correction for the influence 

 of the moon's parallax, and that which Mr. Dessiou has calculated. 



