DISCUSSIONS OF OBSKRVATIONS OF THE TIDES. 285 



Account of the recent Discussiotis of Observations of the Tides 

 which have been obtained by means of the grant of Money 

 which was placed at the disposal of the Author for that jnir- 

 pose at the last Meeting of the Association. By J. W. 

 Lubbock, Esq. 



I WISH to lay before the Section tlie points to which I have 

 chiefly directed my attention on the subject of the tides since 

 the last meeting of the Association, aided by the grant of money 

 which was placed at my disposal, and for which I beg to offer 

 my warmest acknowledgements. 



In the first place I requested Mr. Dessiou to separate into 

 different categories his discussion of the Liverpool tides for the 

 calendar months, so as to ascertain the difference between the 

 morning and evening tides on the same day, or the diurnal ine- 

 quality. This inequality is extremely sensible at Liverpool in 

 the height, as may be seen in the diagram and tables which I 

 prepared, with Mr.Dessiou's assistance, and which are published 

 in the Phil. Trans. 



Mr. Dessiou also, at my request, classified the errors of pre- 

 diction for a year at Liverpool, and also of a year at London, in 

 order to deduce the influence upon the tide of variations in the 

 atmospheric pressure. I have thus succeeded in confirming the 

 result first obtained by M. Daussy from the observations at Brest, 

 namely, that the height of high water is less when the barometer 

 is high, and vice versa. In the Report which I had the honour 

 formerly to present to the Association, I expressed the opinion 

 that the tides in the river Thames did not warrant this infer- 

 ence ; this opinion was founded upon the rough examination of 

 a year's observations, and it is now completely disproved. 



I have also been enabled to procure the assistance of Mr. Jones 

 and Mr. Russell, two excellent computers. These gentlemen, 

 vmder my guidance, have discussed the observations of 19 years 

 at the London Docks. These observations were formerly dis- 

 cussed by Mr. Dessiou with reference to the moon's transit im- 

 mediately preceding. But upon examining the results thus ob- 

 tained I saw that for the interval no satisfactory comparison with 

 theory could be obtained for the moon's parallax and declination 

 corrections in this manner, and that it was indispensible to re- 

 fer the phsenomena to the tide-producing forces at a period more 

 remote. The law of the intervals, when the discussion is insti- 

 tuted with reference to the transit immediately preceding the 

 time of high water, whether at London, Liverpool, or Brest, de- 



