TIDAL DATUM PLANES 121 
Taking now Neah Bay for every other year from 1938 to 1948, the data follow: 
LW below Factor fr 
Year pogo =| Becton tome ey pay PE ces a RAC eae ee 
Feet Fee Feet Feet Feet 
ICS. === 2. 89 0. 988 1. 44 1. 082 2. 86 il, Sf 4, 42 
1040) 2 See Se es 2..93 0. 979 Il, S35 Il, eye 2. 87 1. 58 4, 45 
QA. See 2. 87 0. 980 1. 40 1. 161 2. 81 1. 63 4, 44 
Ql ee DU 0. 990 1. 50 1. 065 2. 74 1. 60 4, 34 
OA Geer Se Dh, 5) 1. 004 iL. GS 0. 962 2, UG il, 5y8) 4, 35 
Qk Se eens a rel 1. 016 il, 7H 0. 899 PTB Il, Bz 4, 32 
For Neah Bay the best determined value of mean lower low water below half- 
tide level was found to be 4.40 feet. The yearly values derived in the last column 
table above are thus within 0.06 foot of this best determined value on the average, 
with 0.08 foot the greatest difference. The best determined value of DLQ at Neah 
Bay is 1.58 feet and from column 7 of the table above it is seen that the greatest 
difference from this best determined value is 0.05 foot. From a year of observations, 
therefore, mean lower low water below half-tide level can be determined correct to 
within 0.1 foot. 
Month.—The determination of mean lower low water from a month of observa- 
tions is carried out in exactly the same way as for a year. It is exemplified below for 
La Jolla and Neah Bay, taking every other month of the year 1946. The data for 
La Jolla follow: 
Date Me Below. Factor trom DLQ Bator ten ESN DLO NEE Wibelow 
1946 2 Feet Feet Feet Feet Feet 
Vamuanye a= == 1. 76 1. 000 1. 08 0. 87 i, 7/@ 0. 94 70 
Mignon eS 1. 85 1. 001 0. 79 1. 16 1. 85 0. 92 2 TE 
BMVitiyieeeere ess 1. 87 1. 002 1. 00 0. 90 1. 87 0. 90 D7 
iu gy pee I a = 1.-79 1. 003 1.13 0. 84 1. 80 0. 95 24. WE, 
September _ ----- iL 2 1. 004 0. 76 1,14 1. 78 0. 87 2. 65 
November - - ---- 1. 83 1. 005 1. 09 0. 88 1, 84 0. 96 2. 80 
The primary value of MLLW below HTL for La Jolla is 2.73 feet. The greatest 
difference from this value of the derived monthly values in the last column of the 
table above is 0.08 foot. The primary value of DLQ at La Jolla is 0.92 foot and the 
ereatest difference from this value of the derived monthly values in the 7th column is 
0.05 foot. . 
Comparing the results in the last column derived by the use of tabular values 
with those derived by means of simultaneous observations (page 118), the values for 
individual months are seen to differ sometimes hy as much as 0.1 foot. Comparing 
with the primary value of 2.73 feet, the results derived from tabular values give some- 
what less concordant results. 
949995—51—_—9 
