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 to 
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 truc 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 Ufracombe 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 tides 
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 the 
‘observations made at London and Liverpool, and the theory, that 
he was strongly inclined to believe that that coincidence would he 
Vor. XXXI.—No. 2. 43 
