TIDAL DATUM PLANES 119 
S888 
Los Angeles La Jolla Factors for correction La Jolla 
ae Lae bed ala MLW MLLW 
elow DL LW below DL Lw DL bel Mean 1 
HTL Q HTL Q Q ae DLQ ee ee 
1946 Feet Feet Feet Feet ; Feet Feet Feet 
dull 1 5 ees 74, BY) 1. 70 74, PHS) Il, 05 0. 810 0. 559 1. 82 0. 98 2. 80 
Jub; G2 2255 Il, BY 0. 25 I, 2 0. 30 1. 424 3. 800 ly 74 1. 14 2. 88 
Jiwlie 1) 1 7 1. 20 1. 65 120 1. 093 0. 792 1. 80 0. 95 2. YH 
aleyeG= 1. 98 1. 45 1. 88 1. 45 0. 949 0. 655 1. 78 0. 95 2, ‘Ta 
Julie 2 ee Il, GY 0. 20 1. 40 0. 20 IL, BB 4. 750 1. 73 0. 95 2. 68 
why 2G LE ae 2. 45 1. 65 2, BY) 1. 60 0. 767 0. 576 1. 80 0. 92 2, UP 
uly Sls eee ee Pa, 2 1. 20 2. 05 it, 15) 0. 887 0. 792 1. 82 0. 91 PA, 1133 
The primary values for Los Angeles used for determining the correction factors 
are 1.88 feet for mean low water below half-tide level and 0.95 for mean DLQ. The 
primary value for mean lower low water below half-tide level at La Jolla is 2.73 feet 
and for mean DLQ 0.92 foot. In the last column of the table above, the greatest 
difference between the primary value of mean lower low water below half-tide level 
and that determined from one day of observations is 0.15 foot. 
If now we derive mean lower low water from one day of observations at Neah 
Bay, by comparison with Seattle, we find greater differences than in the preceding ex- 
ample. Every fifth day of July 1946 will again be used. 
Seattle Neah Bay Factors for correction Neah Bay 
oe LW LW MLW a MLLW 
below DLQ below DLQ LW DLQ below DLQ, below 
HTL HTL HTL HTL 
1946 Feet Feet Feet Feet Feet Feet Feet 
Awiky Ws See 82 5. 25 3. 70 05 0. 793 0. 541 2. 93 1. 65 4, 58 
(3. oon 2. 95 0. 40 2. 02 0. 50 1. 295 7. 100 2. 62 3. 55 6. 17 
1A, Cee 3. 38 4.10 2. 42 2. 00 ik; 11830) 0. 693 Ph, Te 1. 39 4,12 
Gee 2 3595 4. 40 2. 95 2. 50 0. 967 0. 645 2. 85 1. 61 4. 46 
74)| Sea 2; OD 0. 05 2. 38 0. 55 1. 140 | 56. 800 MY, TAL 51. 24 53. 95 
TX G5 oes eles 4.45 5. 10 3. 35 2. 70 0. 858 0. 557 2. 87 1. 50 4. 37 
7B) haa ea 4. 50 3. 30 3. 45 1. 90 0. 849 0. 861 2. 93 1. 64 4. 57 
The best determined value for mean lower low water below half-tide level at 
Neah Bay for epoch 1930-1948 is 4.40 feet. Of the seven values in the last column of 
the table above, two differ by more than a foot from this best determined value, and 
one of these differs by more than 40 feet. It is seen that in both of these cases the 
difficulty comes from the determination of the mean DLQ, the best determined value 
of which at Neah Bay is 1.58 feet. 
If for the day of observations the diurnal inequality departs widely from its mean 
value at the primary station, the derived value at the secondary station may vary 
considerably from its mean value, unless the type of tide at both stations is closely 
similar. Oa the 6th and 21st, DLQ at Seattle varied widely from its mean value, 
evidenced by the magnitude of the factors in 7th column for those days. In table 4, 
