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comparisons was to test the accuracy of the predictions. The results compare favourably with the comparisons between actuals and predictions at Indian ports, published by the Tidal Branch of the Survey of India ; these comparisons being derived from predictions based upon harmonic constants evaluated by the same method of reducing tidal observations, by harmonic, analysis, as that adopted in Now Zealand. The actual heights of high and low water as obtained from the self-registering tide-gauge, records have been corrected for barometric pressure at Auckland, Wellington, and Bluff. Barograph records were not available for the Port of Westport. The errors of the predictions thus determined are tabulated in the three tables herewith appended.

No. 1. — Percentages and Amounts of the Errors in the Predicted Times of High Water and Low Water at Four Standard Ports for the Year 1921.

No. 2. — Percentages and Amounts of the Errors in the Predicted Heights of High Water and Low Water at Four Standard Ports for the Year 1921.

No. 3. — Table of Average Errors in the Predicted Times and Heights of High and Low Water at Four Standard Ports for the Year 1921.

Port. , i ,, Errors over Errors over Comparisons Errors 30 Minutes Errors over between Aotual not exceeding , , , , . r „,. , ., ,. . , , ki,: ». and under and under 45 Minutes, and Predated 15 Mmutes. 30 Minutes . 45 Minutes. V alues. HIGH WATER. Auckland .. Wellington Bluff Westport .. 705 705 695 683 % 80 89 90 80 % 17 9 10 15 % 3 2 0 4 /o 0 o 0 1 L< LOW WATER. 0 0 0 i) Auckland .. Wellington Bluff Westport .. 705 705 694 684 87 84 82 86 12 13 17 13 1 3 1 1

Port. Number of -,. t, „ . Mean Range Comparisons . b between Actual „ . rr ., and Predicted &pnn | L l if * Values. mlect - Errors not exceeding 0 in. Errors over „ 0 in. and Errors over underlain. Uln ' HL GH WATER. Auckland .. Wellington Bluff Westport .. 705 705 695 682 8-8 3-4 8-0 9-5 % 82 95 86 72 % 18 5 14 24 /o 0 0 0 4 LO )W WATER. Auckland .. Wellington Bluff Westport .. 705 705 694 685 8-8 3-4 8-0 9-5 80 96 70 71 19 4 27 23 1 0 3 (i

Averago Errors. Port. Mean Range of .Spring Tides in Feet. Of Ti Min ime in utes. Of .11 eight: the 11 in Terms of Of Hei Inci ight in hes. ange. nckland ■ .. Wellington Huff Westport 8-8 3-4 8-0 9-5 H.W. 11 9 8 10 L.W. 9 9 9 9 H.W. 0-037 0-066 0-043 0-049 L.W. 0-039 0-068 0-058 0-051 H.W. 4 3 4 6 L.W. 4 3 6 6 Genera] mean 10 0-049 0-054