33 
passing the upper meridian. This point lends additional weight to 
the equilibrium theory under which, as I have stated before, the cone 
of water attempts to place itself under the sun and moon and accord- 
ing to which that tide would be greatest which is directly under and 
not opposite to the two bodies — notice how the tides of the 6th con- 
form to this argument. And if these tides are compared with those 
of the 19th additional weight is given to the theory from the fact 
that on the 6th when the sun and moon are both north of the 
equator, the tide is higher than on the later date when the sun is 
north but the moon south. 
Another feature of the tides, familiar to everyone, namely its 
daily retardation, is also clearly brought out. Just as the moon, 
owing to its movement eastwards along its orbit, rises later every 
day, so the tidal cone, since its progress is governed in great part 
by the moon, suffers retardation. The mean retardation of the moon 
for these 28 days in June amounts to 50 minutes and for the same 
period the tidal retardation works out at 49 minutes. This agree- 
ment is very striking and proves how closely the progress of the 
tidal wave depends upon the moon. Turning to the tide curves for 
June once more and noting the times at which the alternate high 
tides occur, it will be observed that on June 1st the high tide took 
place at 8.15 a.m. ; on June 2nd at 8.44 a.m. ; on June 3rd at 9.48 
a.m. ; on June 4th at 10.16 a.m., and so on — the crest of the morning 
wave gradually becoming later every day, until by June 15th the 
retardation amounts to over 12 hours, and naturally the high tide 
which occurred in the morning on June 1st has now become on the 
15th the evening tide. It will also be noted that the times of high 
and low waters on the 15th are very nearly the same as on the 1st. 
If the cruve could be followed to the end of the month, it would 
be found that this evening tide became in turn the morning tide of 
the 29th. 
From all this it will be seen at once that so far as the times 
of high and low r water are concerned the tides repeat themselves very 
closely every fortnight, or, more exactly, every half of a lunation. 
Other interesting features come to light on inspecting the curve. 
Thus, during the first fortnight, the range of tide w r as greatest on 
the 6th and 7th — the largest variation in level between consecutive 
high and low waters being 18 feet, namely between the mid-day 
high tide and the afternoon low tide; while the smallest variation 
occurred between the evening high tide of the 14th and the morning- 
low tide of the 15th, when the difference amounted to l 1 /^ feet. 
From this time on the range increases until the 19th and 20th, when 
it w r as approximately 17 feet and then it begins again to diminish, 
reaching a minimum of 5% feet on the 28th. 
A glance at the moon’s phases shows that it w T as “New” on the 
5th and “Full” on the 19th, w r hile “First and Last Quarters” fell 
on the 12th and 26th respectively. The tides which occur about the 
time of new or full moon are termed “spring” tides, while those 
