LAWS OF THE TIDES FROM SHORT SERIES OP 0BSERVATI0I«JS. 233 



their existence. Till the subject of the tides is thus treated in a manner worthy of 

 its scientific importance, and of the promise which it now holds forth, it must be 

 considered as offering a blot in that system of the national cultivation of astronomy, 

 of which our public observatories are, in other departments of science, such effective 

 and magnificent examples. 



8. The reference of the phenomena of the tides to mechanical principles by rigor- 

 ous reasoning has not yet been executed ; and we can see enough of the difficulties 

 of the subject to believe that it will probably be some time before this problem can 

 be fully solved. In the meanwhile, we have an intermediate type of comparison for 

 the facts, in the equilibrium theory of Bernoulli ; for that theory, by modifying the 

 epochs and other elements, may be made to represent in an approximate manner the 

 laws of the phenomena. Nor does it appear to be too much to expect, that it may 

 hereafter be rigorously shown from mechanical principles, that the form of an irre- 

 gular moving fluid mass, constantly dragged along by certain forces, shall at every 

 instant resemble the form of equilibrium which the forces would produce at some 

 anterior epoch, the anterior epoch being somewhat different for the different features 

 of the fluid form. If such a hydrodynamical proposition could be established, almost 

 all the facts hitherto discovered respecting the tides would be fully explained. 



9. The materials of the following researches are the tide observations made at 

 Plymouth in the years 1834, 1835, 1836, and 1837, under the direction of the Dock 

 Master and Assistant Dock Master; and the observations made at Bristol in 1834, 

 1835, 1836, 1837, by direction of the Dock Committee. 



The Plymouth observations were discussed by Mr. Dessiou and Mr. D. Ross of the 

 Hydrographer's Oflfice, whose valuable services were placed at my disposal by the 

 Hydrographer, Captain Beaufort. The Bristol observations were discussed by 

 Mr. Bunt, whom I was enabled to engage in this employment by means of grants 

 voted for that purpose at the Meetings of the British Association for the Advance- 

 ment of Science which took place in 1836 and 1837. 



10. The methods of discussing the observations which were employed were some- 

 what different for the two places. As that practised at my suggestion by Mr. Bunt 

 for the Bristol tides appears to be the better of the two, I will subjoin his description 

 of the process. 



I may previously observe that in all cases we employ the method already described 

 in previous papers : namely, upon a series of parallel ordinates* corresponding to 

 the times of moon*s transit, we lay down the successive tides, that is, the heights or 

 the lunitidal intervals, as the one or the other are the subject of examination. This 

 curve is more or less irregula?, but for most places the leading feature is the zigzag 

 form which arises from the diurnal inequality -J-. A curve is drawn by the eye so as 



* For the purpose of all these operations it is most convenient to have paper ruled into small squares of 

 inches and twelfths of inches. 



t Researches, Seventh Series, Philosophical Transactions, 1837. 

 Mdcccxxxviii. 2 H 



