Proceedings of the British Association. 335 



3. Mr. Whewell gave an account of the proceedings of the coni- 

 mittee appointed to fix hnes of the relative level of sea and land. 

 He commenced by saying, that as in the discussion of the relative 

 level of land and sea, the tides of the ocean were an important ele- 

 ment, he should preface the remarks upon that subject, which he 

 intended to submit, by making a (ew observations upon the very 

 valuable communication of his friend Mr. Lubbock. This commu- 

 nication he highly eulogized, and pointed out to the Section the im- 

 portance of many of the conclusions, should they prove hereafter 

 to be generally applicable ; but he expressed strongly his fears that 

 this would not be the case. Observation had, in the instance of 

 the tides, far outstript theory, for many reasons, which it would be 

 impossible to detail ; but among the most prominent were the com- 

 plexity of the problem itself involving the astronomical theories both 

 of the sun and moon ; the masses of these bodies ; the motions of 

 disturbed fluids, and local causes tending to alter or modify the gen- 

 eral geographical effect of the great tide-wave at any particular place. 

 It was upon a careful review of these considerations, that he was led 

 to fear that it would be still many years before theory would become 

 so guarded and supported by local observations, as to afford a suffi- 

 ciently correct guide to be implicitly relied on in these speculations. 

 He instanced the tides of the Bristol Channel, which in consequence 

 of their excessive magnitude, afforded magnified representations of 

 the phenomena by which the deviations become more remarkable. 

 At the port of Bristol, the tide rose to a height of fifty feet, while 

 towards the lower part of the channel it only rose twenty, and along 

 other parts of the coast not quite so high. The most striking of 

 Mr. Lubbock's conclusions was that by which it appeared that the 

 ocean assumed the form of the spheroid of equilibrium, according to 

 the theory of Bernouilli but at five transits of the moon preceding 

 the tide itself. By the calculations of Mr. Bent, however, it would 

 appear, that although the observed laws of the tides at Bristol might 

 be made to agree with Bernouilli's theory of equilibrium tides, by 

 referring them to a certain anterior transit, — so far as the changes 

 due to parallax were concerned, as also as far as those due to de- 

 clination were concerned, — yet it turned out that this anterior period 

 itself was not the same for parallax as for declination. The two 

 series of changes have not therefore a common origin or a common 

 epoch ; so that in fact there is no anterior period which would give 

 theoretical tides agreeing with observed tides ; and, therefore, at 



