338 Proceedings of the British Association. 



found at length to be universal. — Prof. Steyelly inquired, from Mr, 

 Lubbock, whether he did not think it quite possible that local causes 

 might exist, which would be fully capable of producing the devia- 

 tions from the theory of Bernouilli ; as, for instance, in the case of 

 Bristol, so ably insisted upon by Prof. Whewell, where the causes 

 of the extraordinary elevation are the land-locking of the tide-wave 

 as it ascends the narrowing channel, and the reflexions of other tide- 

 waves from several places. Now, particularly in the case of reflex, 

 tides, may it not so happen, and does it not, in fact, happen in sev- 

 eral places, that they bring the actual tide to a given port at a time 

 very different from that at which the influence of the moon and sun, 

 if unimpeded, would cause it to arrive, and thus separate, as Prof. 

 Whewell had stated, the origin or epoch of the variations due, sup- 

 pose to parallax and declension, and even cause other deviations 

 from Bernouilli's theory ? — Mr. Lubbock replied, that unquestiona- 

 bly it might so happen ; but in his opinion, the discussion of a few 

 observations, like those made at Bristol, could not be expected to 

 point out very exactly the origin or epoch of either of the variations 

 of parallax or declination, with sufficient exactness, to furnish se- 

 cure data for determining that they did not correspond to any one 

 common previous transit of the moon. — Prof. Whewell exhibited 

 some diagrams, which tended to illustrate his view of the question ; 

 and, in particular, he drew the attention of the section to the cir- 

 cumstance, that the diurnal inequality, which was now beginning to 

 be observed, decided the question, inasmuch as its epoch could not 

 by any means be attributed to the same previous transit of the moon 

 to which the others were referred. — Mr. Frend congratulated the 

 meeting upon the prospect now held out of determining precisely 

 that most important practical question, the true level of the sea. 



Mr. Lubbock next made a communication respecting the forma- 

 tion of an empirical lunar theory. 



Prof. Sir William Hamilton read his report on Mr. George B. 

 Jerrard's mathematical researches, connected with the general solu- 

 tion of algebraic equations. 



Prof. Phillips read his report of the experiments instituted with 

 a view to determine the temperature of the interior of the earth. 



Prof. Forbes gave an account of the experiments he had directed 

 to be made on subterranean temperature at the Lead Hills in Scot- 

 land. 



The Rev. Mr. Craig read a paper on polarized light. 



