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II. On the Empirical Laws of the Tides in the Port of London ; with some Rejieximis 

 on the Theory. By the Rev. William Whewell, A.M., F.R.S., Fellow and Tutor 

 of Trinity College, Cambridge. 



Received November 13, 1833, — Read January 9, 1834. 



A HE present state of our knowledge of the tides is remarkably at variance with 

 the complete and scientific character which Physical Astronomy is, in common 

 opinion, supposed to have attained. We may, perhaps, most easily figure to ourselves 

 the real condition of this subject, by imagining what the condition of other branches 

 of astronomy would be, if some great natural or moral convulsion should sweep away 

 our existing science, and replunge us in the ignorance of the dark ages, leaving extant 

 only a few general notions concerning the theories which are at present established. 

 In such a state of things, we may suppose that some tradition of the doctrine of uni- 

 versal gravitation would survive the change, and that learned men would still go on 

 asserting that the various astronomical phenomena of the universe were owing to that 

 cause ; but the resources of mathematical art being, for the time, lost, they would be 

 unable to prove the truth of such assertions : and, both the collected stores of obser- 

 vation, and the habit and apparatus of observing, being, in such a case, supposed to 

 be annihilated, it would be long before there would arise persons able and willing to 

 supply such deficiency ; the more so as those who might make such collections would 

 have still to seek for the mode of turning them to any use. If, in this state of things, 

 a few persons should, by their own sagacity and labour, or by the aid of some tradi- 

 tionary secret, attain to the power of predicting phenomena with tolerable correctness, 

 we may imagine that they would use their peculiar skill for purposes of gain, and 

 that they would not readily admit the world at large to the knowledge of the secret 

 which gave them a superiority over the rest of their countrymen. 



Our knowledge of the tides, at the present time, exactly realizes this imaginary 

 condition which we have supposed for astronomy in general. Our philosophers assert, 

 without hesitation, that this phenomenon is the result of the law of the universal gra- 

 vitation of matter ; yet no one has hitherto deduced, from this law, the laws by which 

 the phenomena are actually regulated with regard to time and place. Analysis has 

 been largely used ; but it has been employed only to deduce the consequences of cer- 

 tain assumed suppositions, which suppositions are acknowledged to be utterly different 

 from the real state of the case : and where is the immediate advantage, for the purposes 

 of sound philosophy, of analysis which does not solve the problem proposed, over no 

 analysis at all ? Some observations of the tides have no doubt been made, and more 

 are now making ; but it is not too much to say, that these are only a commencement 



