DIURNAL INEQUALITY OF THE HEIGHT OF THE TIDE. 
79 
The amount of the inequality is nearly the same as at Plymouth, or rather greater, 
being, in the most regular parts of the series, one inch of height for every three degrees 
of declination. 
In these parts of the series (May, June, July, 1835,) the coincidence of the formula 
with observation is as close as at Plymouth. In other months (March, April, and 
August,) there are discrepancies; but we cannot consider these as throwing any 
doubt on the general correctness of the formulae, when we see how well it represents 
the observed diurnal inequality of low water, which is much more marked than that 
of high water. 
The diurnal inequality of low water at Singapore is of a magnitude which it would 
have been impossible to anticipate. It makes a difference' in many cases of not less 
than six feet between the height of the morning and evening tide ; the whole rise of 
the mean tide being only seven feet at spring tides, and the difference of mean spring 
and neap tides not more than two feet. 
This enormous diurnal inequality conforms, with deviations which are slight con- 
sidering its magnitude, to the same formula which we have already stated, the epoch 
being the same as that for high water ; that is, thirty-six lunar hours anterior to the 
last transit. The multiplier is different in different months, varying from f to 1 ; so 
that each degree of the moon’s declination produces an effect of nearly an inch in the 
height of low water, or two inches in the difference of two successive low waters. 
Sect. III. On the Diurnal Inequality at some other places , and on the General Laws of 
its Progress. 
I have not found any register of tide observations which exhibits the diurnal in- 
equality so clearly and regularly as Plymouth and Singapore, although I have tried 
many series observed in different parts of the world. It may however be detected in 
many, perhaps in most, places. The comparison of the circumstances of this inequa- 
lity in different places is curious and interesting, and especially the change which the 
epoch undergoes ; that is, the anterior period at which the moon’s declination corre- 
sponds to the amount and direction of the inequality. 
Bristol. — Mr. Bunt, who has bestowed very great labour upon the analysis of tide 
observations made at Bristol, has, among other inquiries, endeavoured to determine 
the diurnal inequality at that port. The results are not very regular, but they lead 
him to the conclusion that the inequality vanishes at nearly the distance of five days’ 
motion of the moon from her nodes ; that is, the epoch is Jive days. The amount of 
the inequality is five or six inches each way, at the greatest. 
Liverpool. — The diurnal inequality of the heights at Liverpool has been detected 
by Mr. Bywater from the observations, and introduced by him into his tide tables- 
I have already remarked in these Researches *, that the epoch of the diurnal inequa- 
lity at this port is about six days and a quarter ; but I do not conceive the determina- 
* Fifth Series. Philosophical Transactions, 1836, p. 133. 
