SEQUEL TO THE EPOCH OF KEWTOX. 459 



guardians of the established theory of the universe, to compare it in 

 the greatest possible detail with the facts. Mr. Lubbock was the first 

 mathematician who undertook the extensive labors which such a con- 

 viction suggested. Finding that regular tide-observations had been 

 made at the London Docks from 1795, he took nineteen years of these 

 (purposely selecting the length of a cycle of the motions of the lunar 

 orbit), and caused them (in 1831) to be analyzed by Mr. Dessiou, an 

 expert calculator. He thus obtained 13 Tables for the effect of the 

 Moon's Declination, Parallax, and hour of Transit, on the tides ; and 

 was enabled to produce Tide-tables founded upon the data thus ob- 

 tained. Some mistakes in these as first published (mistakes unimpor- 

 tant as to the theoretical value of the work), served to show the jeal- 

 ousy of the practical tide-table calculators, by the acrimony with which 

 the oversights were dwelt upon ; but in a very few years, the tables 

 thus produced by an open and scientific process were more exact than 

 those which resulted from any of the secrets ; and thus practice was 

 brought into its proper subordination to theory. 



The theory with which Mr. Lubbock was led to compare his results., 

 was the Equilibrium-theory of Daniel Bernoulli ; and it was found that 

 this theory, with certain modifications of its elements, represented the 

 facts to a remarkable degree of precision. Mr. Lubbock pointed out 

 this agreement especially in the semi-mensual inequality of the times 

 of high water. The like agreement was afterwards (in 1833) shown 

 by Mr. Whewell 41 to obtain still more accurately at Liverpool, both 

 for the Times and Heights ; for by this time, nineteen years of Hutch- 

 iuson's Liverpool Observations had also been discussed by Mr. Lubbock. 

 The other inequalities of the Times and Heights (depending upon the 

 Declination and Parallax of the Moon and Sun,) were variously com- 

 pared with the Equilibrium-theory by Mr. Lubbock and Mr. Whewell ; 

 and the general result was, that the facts agreed with the condition of 

 equilibrium at a certain anterior time, but that this anterior time was 

 different for different phenomena. In like manner it appeared to fol- 

 low from these researches, that in order to explain the facts, the mass of 

 Uie moon must be supposed different in the calculation at different places. 

 A result in effect the same was obtained by M. Daussy, 45 an active 

 French Hydrographer; for he found that ooservations at various sta- 

 tions could not be reconciled with the formulae of Laplace's Mecanique 



Phil. Trant. 1S31. British Almanac, 1332. " Phil. Trans. 1SS4. 



45 Connaissance des Tt/ns, 1 s 3S. 



