40 THE REV. W. WHEWELL ON THE EMPIRICAL LAWS 



Chap. IV. Reflexions on the Theory. 



It would be unsafe to attempt to deduce any general views concerning the laws of 

 the tides from the preceding investigations. It is very unlikely that the discussion 

 of observations at any one place, and those the very first set which have been syste- 

 matically discussed, should exhibit clearly the true principles of the theory: and 

 besides this, it so happens, that the phenomena of the tides at London are in some 

 measure masked by a curious combination of circumstances, namely, by the mouth 

 of its river being on the side of an island, turned away from the side on which the 

 tide comes, and so situated that the path of the tide round one end of the island is 

 just twelve hours longer than round the other. It will require the accumulation and 

 discussion of many large masses of observations, at various places, to put us in firm 

 possession of the laws of the phenomena as given by experience ; and this road, 

 whether or not it be the onli/ practicable way of arriving at the true theory, is at 

 least that to which, founding our expectations on the past history of science, we may 

 look with most hope. When we consider the enormous accumulation of observed 

 phenomena and empirical laws which preceded the discovery of the true principles 

 of the heavenly motions, we may easily suppose that we are only at the outset of what 

 we have to do, in order to obtain the same success with regard to the tides : and we 

 may, from the same consideration, find additional motives to desire that such obser- 

 vations may be made, and such existing observations may be discussed, as may most 

 speedily lead us to a complete and scientific knowledge of the subject. 



But though we cannot make our inferences from the preceding investigation with 

 confidence, there are some reflexions concerning the mode in which the forces of the 

 sun and moon manifest themselves in the tides, which are suggested by the compa- 

 rison made in the foregoing pages, and which I will venture to state. The confirma- 

 tion or refutation of these views must depend on future investigations of the same 

 nature as that contained in this memoir : in the mean time, the views seem fitted to 

 give some additional impulse to the curiosity with which all men of science must now 

 look upon the progress of this subject. 



Among the inequalities considered in this memoir, those in which the empirical 

 laws are the clearest and the anomalies the smallest (after the semimenstrual inequa- 

 lities,) are the inequalities of the time of high water, depending on the moon's parallax 

 and declination. In these the comparison of the law, from theory and from observa- 

 tion, may be stated as follows : 



Observation, Theory. 



F = (P - ;,) (B H- B sin 2 (?) - (3)) ; (P - j^) B sin 2 (p - a). 



Q' = (sin^ - sin' A) (C -h D sin 2 (9 - y)) ; (sin'J - sin' A) D sin 2 (^ - a). 



It will be observed, that in each of these cases observation gives, in P' and Q', a 

 term depending on the parallax and on the declination, (namely, the terms (P — p)B 



