The records for the year 1913 have been tabulated and analysed; 
the tidal constants thus evolved appear at the end of this paper. 
Before leaving' the Port Hedland tides it will be interesting 
and instructive to examine in detail the tidal trace for the month 
of June, 1913, of which a copy is reproduced (vide Plate XL). 
It should be explained that this is not an absolute copy but is 
plotted from the actual times and heights obtained from the original 
sheets. This procedure was adopted in order that the confusion 
resulting from the high water appearing at the bottom might be 
obviated, for in plotting it was quite a simple matter to arrange this 
without in any way altering the curve. 
It will be noticed that the curve is divided into four parts, each 
part representing the record for one week. Thus the first line 
commences at 6 a.m. on the first (Sunday) and finishes at 6 a.m. on 
the following Sunday, while the second line commences where the 
first line terminated, namely at 6 a.m. on Sunday (8th) and so on 
with lines three and four. The curves for the corresponding days 
of the week are thus found in the same vertical line. The height 
scale is shown at either end and runs from 5ft. to 25ft. Only the 
even hours of the day and night are marked along the top — “Day 
12” being noon, while “Night 12” stands for midnight and the com- 
mencement of the day. Along the 25ft. line the approximate times 
of transit of the moon for the meridian of Port Hedland are noted 
with short black lines, the lower transits being distinguished from 
the upper by small extensions at the bottom of the line. Along this 
line the phases of the moon are also shown, the black spot standing 
for “New Moon,” the spot darkened on the right-hand side being the 
“First Quarter,” the white spot “Full Moon,” and the spot darkened 
on the left-hand side representing “Last Quarter.” Along the 5ft. 
line the day on which the moon was furthest north, on the equator, 
and furthest south is marked, as also the times of “Perigee” and 
“Apogee,” namely when the moon was nearest and farthest away 
from the earth. 
The first striking peculiarity noticeable in connection with these 
tidal curves is the difference between the two high tides or the two 
low tides of each day. In nearly every instance the night tide is 
from six inches to almost two feet lower than the day tide. Refer- 
ence to the diagram “Diurnal Irregularity,” Plate VIII., Fig. 1, will 
explain how this comes about. 
Continuing the investigation and bearing in mind the changes 
in position of the ellipsoidal shell of water resulting from alterations 
in the moon’s position, it will be found, as would be expected, that 
when the moon is at its greatest distance north or south of the equator 
the maximum difference between alternate high waters occurs, 
amounting to 1ft. lOin. and 1ft. Gin. on June 6th and 19tli respec- 
tively and more than that, the highest of the two falls on the 6th 
when the moon was between one and two days old and consequently 
the two bodies, the sun and moon, would be close together when 
