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BY UPPER TRANSIT.

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Moon's upper transit 15th N. A.
Cor. for long. gh E.
Moon's upper transit Fowler Point
High water interval
High water (civil time)
14 lunar day
Low water (civil time)
1/2 lunar day
Low water (ast. time)
Add 1 day and sub. 12 hours
Low water (civil time)
14 lunar day
High water (civil time)

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i High water, 16th
2 Low water, 16th
3 High water, 16th
4 Low water, 16th

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Comparing these answers with those found by the preceding method shows that the use of half and quarter lunar day will not produce results satisfactory to the examiner.

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EXPLANATION OF EXAMPLE 16.

On page 118 of the Nautical Almanac, January 12th, the moon's upper transit is more than 12 hours, which shows at once that the moon passes the meridian of Greenwich in the morning and the astronomical date would be the 11th. Take the moon's upper transit for the 11th, ild 14h 48m, and from it subtract the correction 6m for longitude 3 hours east, which gives the moon's upper transit at Zanzibar, to which add the high water interval, 4h 05m, and the result will be the astronomical date and time of high water, ild 18h 47m. To this add 1 day and subtract 12 hours to convert the astronomical time into civil time the 12th, 6h 47m A.M.

To the moon's upper transit at Zanzibar, ild 14h 42m, add the low water interval, 10h 17m, and the result will be the astronomical date and time of low water, 120 00h 59m, and being less than 12 hours is also civil time P.M.

From the same page of the Almanac take the moon's lower transit for the 11th, ild 02h 28m, and subtract the correction 6m for longitude 3 hours east, which gives the moon's lower transit at Zanzibar, and to it add the low water interval, 10h 17m, and the result will be the astronomical date and time of low water, lid 12h 39m. To this add 1 day and subtract 12 hours to convert the astronomical time into civil time the 12th, Oh 39m A.M.

From the same page of the Almanac take the moon's lower transit for the 12th, 120 03h 08m, and subtract the correction 6m for longitude 3 hours east, which gives the moon's lower transit at Zanzibar, and to it add the high water interval, 4h 05m, and the result will be the astronomical date and time of high water, 12d 07h 07m, and being less than 12 hours is also civil time P.M. 16. Example: January 12, 1917. Find the times of high waters and low waters at Zanzibar, East Africa.

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Moon's lower transit 11th N. A.
Cor. for long. 3h E.
Moon's lower transit Zanzibar
Low water interval
Low water (ast. time)
Add 1 day and sub. 12 hours
Low water (civil time)
Moon's lower transit 12th N. A.
Cor. for long. 3h E.
Moon's lower transit Zanzibar
High water interval
High water (civil time)

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i Low water, 12th 2 High water, 12th 3 Low water, 12th 4 High water, 12th

oh 39m A. M. 6 47 A. M. o 59 P. M. 7 07 P. M.

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High water (ast. time) 14 lunar day Low water (civil time)

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13 13 P.M.

12

07

lunar day
High water (civil time)

i Low water, 12th
2 High water, 12th
3 Low water, 12th
4 High water, 12th

oh 34m A. M.
6 47 A. M.
I 00 P. M.
7 13 P. M.

EXPLANATION OF EXAMPLE 17.

On page 118 of the Nautical Almanac, January 8th, the moon's upper transit is more than 12 hours, and for that reason the upper transit for the 7th should be used, 7d 11h 51m, to which is added the correction 8m for longitude 4 hours west, which gives the moon's upper transit at Burntcoat Head, and to it add the high water interval, Oh 27m, and the result will be the astronomical date and time of high water, 7d 12h 26m. To this add 1 day and subtract 12 hours to convert the astronomical time into civil time the 8th, 0h 26m A.M.

To the moon's upper transit at Burntcoat Head, 7d 11h 59m, add the low water interval, 7h 27m, which gives thastronomical date and time of low water, 7d 19h 26m. To this add 1 day and subtract 12 hours to convert the astronomical time into civil time the 8th, 7h 26m A.M.

From the same page of the Almanac take the moon's lower transit for the 8th, 8d 00h 16m, and to it add the correction 8m for longitude 4 hours west, which gives the moon's lower transit at Burntcoat Head, to which add the high water interval, 0h 27m, and the result will be the astronomical date and time of high water, 8d 00h 51m, and being less than 12 hours is also civil time P.M.

To the moon's lower transit at Burntcoat Head, 8d 00h 24m, add the low water interval, 7h 27m, and the result will be the astronomical date and time of low water, 8d 07h 51m, and being less than 12 hours is also civil time P.M.

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