729 



of North America, and then to the westward along the Aleutian 

 Isles, and so to Kamtschatka, as stated by Admiral Liitke. 



The tides in the centre of the Pacific are too small and anomalous 

 to allow us to trace the connection among them. At Tahiti, accord- 

 ing to the observations of Sir Edward Belcher, the solar and lunar 

 tides appear to be equal. 



The tides have been traced along the coasts of New Zealand and 

 Australia by Cook, Flinders, and other succeeding navigators. They 

 come from the east ; and the cotidal lines which mark their pro- 

 gress appear to have a north and south range, except when deflected 

 by passing round promontories and the like. When we pass west- 

 ward from the eastern coast of Australia, the cotidal lines are too 

 much broken and complicated by the intervention of islands, to be 

 traced with our present materials of knovviedge. 



The second part of the memoir, " Oji the Diurnal Inequality treats 

 of the diflTerence of the two tides of the same day, which has also 

 been discussed in former memoirs by the author, and its laws so 

 fully made out, that this inequality has been introduced into the 

 tide tables for Liverpool and for Plymouth. This inequality depends 

 mainly on the moon's declination. In England it is small : it is very 

 marked on the coasts of Spain, Portugal and North America, as was 

 shown by the observations of 1836 : but in the North Pacific and 

 in the Indian seas, it reaches an enormous amount, and shows itself 

 with curious differences. In many places in those seas, the diurnal 

 inequality is much larger than the differences of spring and neap 

 tides, and is so large as utterly to confound the usual modes of 

 estimating the " establishment " of a place. 



This inequality affects the tides of various parts on the coast of 

 Australia to a very great amount, and with very remarkable differ- 

 ences. It is seen at Adelaide on the south, and Port Es ington on 

 the north coast ; and at each ])lace it produces a difference of several 

 feet between every two successive tides, when it is at its maximum : 

 but this difference affects mainly the high waters at Adelaide and the 

 low waters at Port Essington*. Also on the west coast of Australia, 

 near Swan River, the diurnal inequality appears with another pecu- 

 liarity, affecting the times of high water rather than the heights. 

 These differences, the author remarks, show that the diurnal wave 

 travels separately from the semidiurnal wave ; but our mateiials do 

 not at present enable us to analyse the compound tide into these 

 two waves, and to trace the course of each. 



The author observes, in conclusion, that our knowledge of the tides 

 is not likely to be completed, nor even much advanced, by tide ob- 

 servations made by navigators and surveyors voyaging with other 

 main objects. The later observations of the Pacific, though made 

 with great industry, have added little to the knowledge derived from 

 Cook, Flinders and King, because they were not geographically con- 

 nected with each other : and the great discrepancies of the obser- 



* These results follow from a series of tide observations made at Adelaide by 

 Mr. Bealten, aud at Port Essington by Sir Gordon Bremer. 



