232 THE REV. W. WHEWELL ON THE DETERMINATION OF THE 



as well as theoretically better, by such a correction being employed. The same is 

 true, though in a less marked manner, of the correction for lunar declination. 



4. It is hardly necessary to remark, as an additional recommendation of the mode 

 of discussing tide observations which this memoir contains, that it leads us, quite as 

 well as any other method, to the results of longer series. When we have obtained 

 the table or the curve of the parallax correction for several single years in succession, 

 the more accurate table or curve which the whole group of years would give is the 

 mean of the single instances. We thus obtain all the accuracy which a longer series 

 of years can supply, while we have, at the same time, the advantage of seeing how 

 much each year contributes to this accuracy. 



6. In obtaining the laws of tide phenomena from the observations, different modes 

 of procedure may be adopted, and it still remains to be decided which of these modes 

 is the best. For instance, instead of referring each tide to the moon s transit imme- 

 diately preceding, we may refer it to the transit one day, or a day and a half, or two 

 days anterior ; and it is important to determine which of these modes of reference 

 represents most closely the laws of the phenomena. It is also desirable to ascertain 

 what is the nature and amount of the variations, which these alterations of the epoch 

 of the lunitidal interval introduce into the correction tables for declination and 

 parallax. To settle this point has been one object of the present Researches ; and for 

 that purpose I have calculated the correction tables for Bristol, referring the tide to 

 the lunar transit one day, one day and a half, and two days anterior to the transit 

 immediately preceding the tide. Of the results of these different hypotheses I shall 

 hereafter speak. 



7. I will add that the present memoir, by clearing up such points as I have noticed, 

 appears to be suited to wind up the series of general researches respecting the tides, 

 which I have, during some years, laid before the Royal Society from time to time. 

 For if methods of discussing tide observations at any place be given, so complete, 

 that the general laws of the corrections may be easily obtained from the observations 

 of a single year, and good tables from a few years, there remains nothing to be done 

 except to apply these methods to good observations, and thus to construct and im- 

 prove our tide tables for all the most important places ; an employment which can 

 easily be carried on by those persons who have performed the calculations on which 

 the present and preceding memoirs are founded. And thus the study of the tides 

 might be pursued, and, to do the subject justice, ought to be pursued, in the same 

 manner as the study of the other provinces of astronomy: that is, constant and 

 careful observations should be made of the phenomena; and, as fast as they are made, 

 should be reduced and discussed at the public expense ; so as to test the accuracy of 

 the tables already obtained, and to supply the means of making them still more ac- 

 curate. In this manner also, any new corrections, and any changes in the elements 

 of the old corrections, would be brought into view as soon as there was evidence pf 



