SIR G. B. AIRY ON THE TIDES AT MALTA. 
125 
through the tidal day (as the mean height of the water for the day) or are assumed to 
be periodical in the course of the tidal day (as the semidiurnal and diurnal tides in 
height), it is evident that we shall obtain all that is necessary for determination of 
the several coefficients of those quantities, by dividing the 48 measures made on each 
tidal day into 8 groups, each of 6 measures, and taking the mean for each group. 
The further treatment of these will be the subject of the next section. 
The tables below exhibit the means for each of the 8 groups on each day, and 
these numbers are the base of all the subsequent calculations. It is to be remarked 
that the “ Zero of Tidal Time” is 16 m earlier than the time of London high water, 
for the following reason : — The first measure of height on the tidal day was taken at 
the time of London high water, and the last was taken 30 tidal minutes before the 
following London high water. The means for the several groups therefore correspond 
to times 15 tidal minutes or 16 solar minutes earlier than the tidal hours (at intervals 
of 3 h ), beginning with London high water. By fixing the “ Zero of Tidal Time ” 
16 minutes earlier than London high water, the proper relation is established between 
the means of the groups and the subdivisions of the tidal day. 
Means, for every group of three tidal hours, of the six half-hourly elevations of the 
tidal water in each of these groups, recorded at Malta, 1871 and 1872. 
Commencement 
of the Tidal Day, or 
Zero of Tidal Time, 
in Malta Mean 
Solar Time. 
No. of Group. 
Mean of 
Six 
Elevations. 
Commencement 
of the Tidal Day, or 
Zero of Tidal Time, 
in Malta Mean 
Solar Time. 
No. of Group. 
Mean of 
Six 
| Elevations. 
Commencement 
1 of the Tidal Day, or 
| Zero of Tidal Time, 
in Malta Mean 
Solar Time. 
No. of Group. 
Mean of 
Six 
Elevations. 
1871 h. m. 
in. 
1871 h. m. 
in. 
1871 h. m. 
in. 
Mar. 31 . . 22 22 
1 
10-88 
April 4 . . 119 
1 
11-93 
April 7 . . 3 13 
1 
1223 
2 
11T5 
2 
11-83 
2 
9-87 
3 
9-07 
3 
7-15 
3 
5-62 
4 
8-83 
4 
8T2 
4 
7-05 
5 
12-62 
5 
12-53 
5 
9-18 
6 
12-68 
6 
9-68 
6 
6-75 
7 
9-72 
7 
5-85 
7 
4-12 
8 
9-10 
8 
8-97 
8 
6"62 
April 1 . . 23 42 
1 
12-55 
April 5 . . 1 56 
1 
13-07 
April 8 . . 3 53 
1 
9-70 
2 
12-55 
2 
10-53 
2 
8-00 
3 
8-73 
3 
6-32 
3 
5-33 
4 
8-40 
4 
8-60 
4 
6-63 
5 
12-62 
5 
12-55 
5 
8-57 
6 
11-90 
6 
9-38 
6 
6-85 
7 
7-52 
7 
5-93 
7 
5-28 
8 
8-33 
8 
9-45 
8 
7-07 
April 3 . . 0 34 
1 
12-17 
April 6 . . 2 34 
1 
13-32 
April 9 . . 4 34 
1 
9-68 
2 
12-22 
2 
10-12 
2 
8-85 
3 
8-18 
3 
6-37 
3 
6-30 
4 
8-08 
4 
9-18 
4 
7-07 
5 
12-52 
5 
12-03 
5 
8-55 
6 
12-05 
6 
9-05 
6 
7-90 
7 
7-02 
7 
6-02 
7 
6-22 
8 
7-57 
8 
9-02 
8 
7-23 
