S22 Proceedings of the British Association. 



the general geographical effect of the great tide- wave at any par- 

 ticulai* place. It was upon a careful review of these considera- 

 tions, that he was led to fear that it would be still many years be- 

 fore theory would l&ecome so guarded and supported by local ob- 

 servations, as to afford a sufficiently correct guide to be implicitly 

 relied on in these speculations. He instanced the tides of the 

 Bristol Channel, which, in consequence of their excessive magni- 

 tude, 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 Lub- 

 bock's conclusions was that by which it appeared that the ocean as- 

 sumed 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 ap- 

 pear, 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 pe- 

 riod 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 least the Bristol tides do not at present appear to con- 

 firm the result obtained by Mr Lubbock from the London tides. Mr 

 Whewell then illustrated these views by diagrams, by the aid of 

 which he explained to the Section the luni-tidal intervals, and the 

 curve of semi-menstrual inequality — (this latter term, and the doc- 

 trine connected with it, was introduced into the subject of the tides 

 by the Professor himself). Professor Whewell then proceeded to 

 the question more immediately before him — the proceedings of the 

 Committee appointed to fix the relative level of the land and sea, 

 with a view to ascertain its permanence, or the contrary. He observ* 

 ed, that the Committee had not taken any active practical steps for 

 the important purposes for which they were appointed, because they 

 had met with many unexpected difficulties requiring much considera- 

 tion. It was, however, intended to appoint a Committee for the 

 same purposes, who should be furnished with instructions founded 

 upon the views at which the former Committee had by their la- 



