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stations ; as also constant observation of tlie course which the ship 

 may be steering. 



December 16, 1847. 



Sir ROBERT HARRY INGLIS, Bart., V.P., in the Chair. 



" Thirteenth Series of Tide Researches." By the Rev. William 

 Whewell, B.D., F.R.S. 



The first part of this paper, " On the Tides of the Pacific," formes a 

 sequel to former papers by the same author, especially to his first 

 memoir on this subject, printed by the Royal Society in 1833 

 (' Essay towards a first approximation to a map of Cotidal Lines '), 

 and to the Sixth Series published in 1836 ('Results of an extended 

 series of Tide Observations made on the coasts of England and 

 America in June 1835 '). Among the results obtained in the latter 

 paper, it appeared that all the " cotidal lines " which have been most 

 exactly traced, meet the coast at a very acute angle ; and for that 

 and for other reasons stated in other memoirs, the drawing of cotidal 

 lines across wide oceans is a very precarious process. In addition 

 to this consideration, the scantiness of our materials has hitherto 

 made it impossible to trace the tides of the Pacific in a connected 

 form; and tbe absence of lunar tides in the central parts of that 

 ocean (as at Tahiti) makes it difficult to represent the course of the 

 tides by means of cotidal lines at all. We are thus led to consider 

 in what other way the course of the tides over wide spaces may be 

 represented : and it is stated by the author, that either a stationary 

 U7idulation, or a rotatory undulation, of the central parts of an ocean, 

 with a border of cotidal lines proceeding outwards from the central 

 undulation into bays and arms of the sea, would represent, in a great 

 measure, the tidal phenomena of the Atlantic and Pacific, as far as 

 thej^ are known. The rotatory undulation here spoken of need not 

 be understood to be a rotatory motion of the water, but a geometrical 

 rotation of the cotidal line, such as takes place in the German Ocean ; 

 the tide in the central part (that is, the rise and fall of the surface) 

 vanishing, as was shown by the observations of Capt, Hewett, though 

 the tidal currents at that point alternate regularly. Such a move- 

 ment of the cotidal line may perhaps represent the phenomena of the 

 North Pacific. 



The author has collected materials for a Tide Map of the Pacific 

 from various navigators ; — Cook, Flinders, King, Captains FitzRoy, 

 Sir E Belcher, Sir James Ross, Stokes, Killet, and others of our 

 own countrymen; Malaspiaa, Freycinet, Du Petit-Thouars, Wrangel 

 and Admiral Liitke, and other Spanish, French and Russian navi- 

 gators. The result of these appears to. be, that on the eastern coast 

 of the Pacific, the tide comes from the west ; arrives first at the coast 

 near Acapulco and Nicoya, and is later and later both to the north 

 and to the south of this point ; passing to the eastward round Cape 

 Horn, as observed by King, and to the northward along the Coast 



