JOURNAL AND PROCEEDINGS. 35 
3 Say 993 999 
= — = —— nearly = —— 
1g. 2197 2190 
33 ge 3 
= — nearly = — = — 
is © 7 
If lunar tide be 1. 
Then lunar tide + solar tide = spring tide 
3 10 
=i — = — 
7 i 
.. Proportion of spring tide to neap tide is as 10 to 4. 
A short explanation of what is meant by the priming and lag- 
zing of the tides should now be made: 
B 
Si es 
\ 2) 
A' A Moon > 
R Q 
Sey) S: 
B' 
Between new Moon and first quarter, the Sun is over a point S, 
behind A. Here the Moon tends to draw the water towards A, 4’, 
and the Sun tends to draw the water towards S, and the antipodal 
point S,. Therefore the combined action tends to draw the water 
towards two points Q, Q’ between 4 and S, and between 4 and S, 
respectively, whose longitudes are rather less than those of 4 and 4’ 
respectively. ‘The resulting position of high water is therefore dis- 
placed to the west, and the high water occurs carder than it would if 
due tothe Moon’s influence alone. ‘The tides are then said to prime. 
Between first quarter and full Moon the Sun is over a point S, 
between 4’ and 4’, and the combined action of the Sun and Moon 
tends to draw the water towards two points, &, 7’, whose longitudes 
are slightly greater than those of A, 4’. The resulting high tides 
