334 Proceedings of the British Association. 



explain this popularly, Mr. Lubbock stated, that, however paradoxi- 

 cal it might appear to persons not acquainted with the subject, yet 

 true it was, that, although the tide depended essentially upon the 

 moon, yet, any particular tide, as it reaches London, would not be 

 in any way sensibly affected, were the moon at that instant, or even 

 at its last transit, to have been annihilated ; for it was the moon as 

 it existed fifty or sixty hours before which caused the disturbance of 

 the ocean, which ultimately resulted in that tide reaching the port 

 of London. The author then exhibited several diagrams, in which 

 the variations of the heights of the tide, as resulting from calculations 

 founded upon the theory, were compared with the results of ob- 

 servations. The general forms of the two curves which represented 

 these two results, corresponded very remarkably ; but the curve 

 corresponding to the actual observations, appeared the more angular 

 or broken in its form, for which Mr. Lubbock satisfactorily account- 

 ed, by stating, that the observations were neither sufficiently numer- 

 ous, nor sufficiently precise, from the very manner in which they 

 were taken and recorded, to warrant an expectation of a closer con- 

 formity, or a more regular curvature. When it is recollected that 

 the observations are at first written on a slate, and then transferred 

 to the written register, by men otherwise much employed, and 

 whose rank in life was not such as would lead us to expect scrupu- 

 lous care, it was not to be wondered at, if occasionally an error of 

 transcript should occur, or even if the observation of one transit was 

 set down as belonging to the next. When to these circupistances it 

 was added, that the tide at London was in all probability, if not cer- 

 tainly, made up of two tides, one having alrea'dy come round the 

 British Islands, meeting the other as it came up the British Chan- 

 nel, it was altogether surprising that the coincidence should be so 

 exact ; and it was one among many other valuable results of these 

 investigations, that it was now pretty certain, that tide tables con- 

 structed for the port of London by the theory of Bernouilli, would 

 give the height and interval with a precision quite sufficient for all 

 practical purposes, and which might be relied on as sufficiently ex- 

 act, when due caution was used in their construction, and the neces- 

 sary and known corrections applied. In conclusion, Mr. Lubbock 

 stated that the observations for the port of London had now been 

 continued from the commencement of this century, and those for 

 Liverpool, as we understood, about twenty-five years. 



