Proceedings of the British Association. 337 



of the sea at a given place ? Until something like this were accom- 

 plished, Mr. Whewell expressed his strong conviction of the hope- 

 lessness of expecting any thing like accuracy in many important and 

 even practical cases. As an example, he supposed the question trt 

 be the altitude of Dunbury Hill referred to the level of the sea : if 

 that level of the sea were taken at Bristol, where the tide rises, as 

 before stated, fifty feet, the level of low water would differ from the 

 same level on the sea coast at Devonshire, where the sea rises, say 

 eighteen feet ; and supposing, as is most probable, the place of mean 

 tide to be the true permanent level by no less a quantity than six- 

 teen feet, which would therefore make that hill to appear sixteen 

 feet higher, upon a hydrographical map constructed by a person 

 taking his level from the coast of Devonshire, than it would appear 

 upon the map of an engineer taking his level at Bristol. In the 

 method proposed, the lines of equal level would run, suppose from 

 Bristol to llfracombe in one direction, and from Bristol to Lyme 

 Regis in the other, and by these a common standard of level would 

 soon be obtained for the entire coast. — Prof. Sir William Hamilton 

 rose to express the sincere pleasure he felt at the masterly exposi- 

 tions of Mr. Lubbock and Prof. Whewell. One conclusion to which 

 Mr. Lubbock had arrived was to him peculiarly interesting, viz. that 

 by which it appeared that the influence of the moon upon the tidesi 

 was not manifest in its effects until some time after it had been ex- 

 erted, for a similar observation had recently been made by Prof. 

 Hansteen -respecting the mutual disturbances of the planets. — Mr. 

 Lubbock rose to say, that the agreement between the results calcu- 

 lated from the theory of Bernouilli and those obtained from actual 

 observation, was much more exact than Prof. Whewell seemed to 

 imagine ; in truth, so close was the agreement, that they might be 

 said absolutely to agree, since the difference was less than the errors 

 that might be expected to occur in making and recording the ob- 

 servations themselves. — Mr. Whewell explained that he wished to 

 confine his observations to the Bristol tides, as these were the ob- 

 servations to which he had particularly turned his attention ; and, 

 with respect to which, he should be able, at the present meeting, to 

 exhibit diagrams to the section, which he felt confident would amply 

 bear out his assertions respecting these tides. — ^Mr. Lubbock stated, 

 that so near, indeed so exact, had been the coincidence between tho 

 observations made at London and Liverpool, and the theory, that 

 he was strongly inclined to believe that that coincidence would be 

 Vol. XXXL— No. 2. 43 



