[pawson] METHODS OF INVESTIGATION OF TIDES & CURRENTS 13 
for lower low water is an inverse function of the height to which low 
water falls. This would not justify a principal station at New West- 
minster; as the variation can be ascertained for calculation purposes, 
and the tidal differences for high water and the half tides are constant. 
A similar distinction is required in the case of lower low water, in cal- 
culating slack water in First Narrows from the reference station at 
Sand Heads. 
On the Lower St. Lawrence, between Father Point and Quebec, 
the variation is also very large in the difference of time for low water. 
It was not possible to bring the variation into any direct relation to 
the height of the tide. It was found to be chiefly in the period of the 
synodic month with the moon’s phases, but requiring a large outstand- 
ing correction in relation with the moon’s distance. The tides for 
Father Point were calculated by this double series of variables in the 
early years, before the harmonic constants were determined there. 
In comparing the Miramichi region with St. Paul island, on the 
opposite sides of the Gulf of St. Lawrence, there is apparently a rever- 
sal in the diurnal inequality. This is of such a character that if the 
tide is followed in its actual progress, the difference in time is not 
constant, but varies so widely as to be practically valueless. Never- 
theless, the tides at Miramichi can be deduced from St. Paul island 
by a constant difference, provided that it is taken as earlier, or for the 
preceding tide, as this reverses the alternation to which the diurnal 
inequality gives rise. 
After entering the Gulf of St. Lawrence through Cabot strait, the 
tide changes its character during its progress towards Northumberland 
strait; and on reaching that strait, the diurnal inequality has developed 
to such a degree that the tide is practically under the control of the 
moon’s declination. There are times when the difference in range 
between the two tides of the day is as great as the difference between 
springs and neaps. It is possible, however, to refer this strait to 
St. Paul island by means of two series of variable differences, for high 
and low water respectively; both series varying in accordance with the 
declination of the moon and alternating with its upper and lower 
transits. The tide tables for Pictou, in the middle of the strait, are 
calculated from St. Paul island by means of these differences, and the 
variation in the moon’s declination during the 19-year cycle is also 
allowed for. The tides for Charlottetown are then computed from 
Pictou by means of differences by which allowance is next made for 
a variation in the period of the synodic month. On account of this 
double variation, Charlottetown has now been equipped as a principal 
station. 
These will suffice as examples of variable tidal differences, as 
