64 Mr. T. Carrick on the Tides and the Earth's Rotation. 



motion of the wave. The hypothesis of a wave always following 

 in the rear of the moon's motion, as assumed by Dr. Mayer, 

 obtains little confirmation from these recorded observations, 

 which, indeed, at first sight would seem rather to indicate a pro- 

 gression nearly everywhere at right angles to the direction of the 

 motion of the moon. 



To this anomalous progression we owe the hypothesis of free 

 ocean waves of translation, whose progress is illustrated by maps 

 of cotidal lines. This hypothesis, however, has been pronounced 

 untenable by its ablest expounder. 



Guided by speculation in cosmical dynamics, the nature of 

 which need not here be alluded to, I have arrived at the conclu- 

 sion that tidal phenomena ought to be grouped in relation to 

 land areas as causal centres. 



In a paper read before the Physical and Mathematical Section 

 of the Literary and Philosophical Society of Manchester on the 

 30th of April last *, I discussed from this point of view the hours 

 of high water at full and change for the principal places on the 

 globe as given in the Tide Tables for 1863 published by the 

 Admiralty (these hours being first reduced to Greenwich mean 

 time), and thereby arrived at the following law of the progres- 

 sion of the wave of high water : — 



' e In all land areas in the northern hemisphere the wave of high 

 water tends to revolve round the coast in the direction of the hands 

 of a watch, and in like areas in the southern hemisphere against the 

 hands of a watch. 33 



The term wave is not here used in the sense of a free wave of 

 translation. Theoretically, this law ought to hold good in pro- 

 portion as land areas approximate to the circular form, with wide 

 uninterrupted ocean spaces all round. 



The complicated nature of the data of tidal hours has always 

 constituted a serious obstacle in the way of any causal theory ; 

 but the above recited law, even if considered as a mere empirical 

 grouping of the facts, comprehends in harmonious relation a 

 much greater range of these facts than any hypothesis hitherto 

 propounded. 



Such being the case, it is obvious that the waves of different 

 hemispheres and of opposite shores will tend to neutralize each 

 other, without leaving even a residual easting in the tidal wave 

 from which any action on the rotation of the earth can be clearly 

 inferred. 



Heathfield, Manchester, THOMAS CarRICK. 



June 18, 1863. 



* The abstract of this paper appears at page 79 of the present Number. 



