Royal Society. 223 



a minute of the vertical position, a quantity which may be supposed 

 to come within the limits of the errors of observation ; hence the 

 author concludes that this spot may be considered as the true mag- 

 netic pole, or as a very near approximation to it, as far, at least, as 

 could be ascertained with the limited means of determination of which 

 he was then in possession. 



A table of the observations, including those on the intensity of the 

 magnetic force at various stations, is subjoined. 



Jan. 9, 1834. — "On the empirical Laws of the Tides in the Port 

 of London, with some Reflections on the Theorv." By the Rev. 

 William Whewell, M.A., F.R.S., Fellow and Tutor of Trini'ty College, 

 Cambridge. 



The present state of our knowledge of the tides is represented bv 

 the author as extremely imperfect, and at variance with the scientific 

 character which Physical Astronomy is supposed to have attained ; 

 for although it be the universally received opinion that they are the 

 direct results of the law of gravitation, the exact laws by which the 

 phenomena are actually regulated with regard to time and place 

 have never been strictly deduced from this general principle. The 

 tide tables that have been given to the world are calculated by em- 

 pirical methods, which are frequently kept secret by those who employ 

 them ; and the mathematical solutions of the problem hitherto at- 

 tempted have been confessedly founded on hypotheses which are in 

 reality very remote from the real facts; and accordingly it is doubtful 

 whether they give even an approximation to the true result. The 

 comparison of the results of theory with extensive series of observa- 

 tions had not been attempted previously to Mr. Lubbock's discussion 

 of the tides of the port of London, recorded in the Philosophical 

 Transactions for 1831. The establishment, on theoretical grounds, 

 of rules for the calculation of tide tables, has been attempted by Ber- 

 noulli and by Laplace : the methods recommended by the former are 

 probably the foundation of those at present used by the calculators 

 of such tables, that of Laplace being complicated, and too laborious 

 for practice. Original tide tables are very few ; none, with which 

 the author is acquainted, deserving that title, except those which are 

 published for Liverpool, and those for London. The former, which 

 are calculated according to rules obtained from Mr. Holden, from the 

 examination of five years of observations, made at the Liverpool docks 

 by Mr. Hutchinson, at that time harbour-master, are remarkably 

 correct. Several tide tables for London are annually published; but 

 they vary considerably from one another. The method generally 

 practised in England for the construction of tide tables for other 

 places, has been to add or subtract some constant quantity, according 

 to the place, assuming as a basis the tide tables either of London or 

 of Liverpool ; but this assumption of a constant difference is shown 

 by the author to be, in various instances, incorrect. Much, therefore, 

 remains to be done, before we can hope to arrive at a scientific solu- 

 tion of this problem. 



' The author then proceeds to examine the empirical laws of the 

 tides of the port of London, deducible from the records of the nine- 



