ME. T. G. BUNT’S DISCUSSION OF TIDE OBSERVATIONS AT BRISTOL. 
formed being completed were then cast up, averaged, and divided by 4 : the quotients 
were the terms out of which the fig 1, Plate I. was constructed. 
Fig. 2, the diurnal inequality of height, was obtained in a precisely similar manner, 
except that only about fourteen years’ observations were employed in its construction. 
The tide to which both these figures refer, c is _ that which follows the south transit 
at an interval of about forty-four hours. In each figure the twenty-four vertical lines 
represent the twenty-four hours of this south transit, apparent time. The twenty-four 
horizontal lines represent the half months, and are the axes from which the curves are 
measured, upwards and downwards, the scale being of an inch to a minute of time 
in fig. 1, and yg- of an inch to an inch of height in fig. 2. When the curve is above the 
axis, it indicates in fig. 1 that the time is later, in consequence of the inequality ; and 
in fig. 2 that the height is greater than it would have otherwise been, and vice versa. 
The distances between these horizontal lines, or axes, are arbitrary, being merely a 
matter of convenience. 
Both these sets of curves were laid down exactly according to the averages of the 
groups, without any arbitrary alteration whatever. In forming the groups, a very few 
enormous residues, evidently the effects of storms, or other accidental causes, were 
excluded. Their number was, I believe, much less than 1 per cent. Of a still less 
number of residues, one half of their amount only was taken, instead of the whole. 
My next attempt was to improve the solar inequality correction, or that which is due 
to the variations of the solar parallax and declination. This was a more laborious affair, 
requiring the recalculation of the 19,000 observed times of high water, in order that 
the same formulae, or curves of lunar correction might be employed throughout. The 
residues found after these new calculations were arranged, as those for the diurnal 
inequality had been, for each half month, and each of the twenty-four hours of transit ; 
as I wanted to see whether anything would be gained by keeping the observations taken 
during the first half lunation separate from those taken during the second. I have 
never made this separation in arrangements for finding or improving any of the lunar 
curves, nor ever until now in those for the solar inequality ; nor am I aware that it 
has ever been done by any other person. These results are contained in Plate II. fig. 3. 
For the purpose of more easily comparing together these two portions of the curves, 
I have dotted in a copy of the curves lying between the hours 12 h 54 m and 0 h 54 m upon 
those of the first twelve hours of transit. The difference in many places is considerable, 
and evidently systematic. 
The circumstance which caused the average of each group to fall on the fifty-fourth 
minute of the hour, was, that the residues were not posted singly, but in pairs, the error 
of the term computed from a south transit of the moon being in every case combined 
with the following one. 
In order to separate, at least approximately, the effects of the solar parallax and decli- 
nation from each other, the following method was adopted. The curves of June 8th 
and June 23rd were combined in one pair, and those of December the 8th and 23rd in 
b 2 
