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Moon's mer. pass. 20th N. A.
Cor. for long. 5h W.
Moon's upper transit Boston
High water interval
High water (civil time)
1/4 lunar day
Low water (civil time)
1/4 lunar day
High water (ast. time)
Add i day and sub. 12 hours
High water (civil time)
14 lunar day
Low water (civil time)

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i Low water, 21st 2 High water, 21st 3 Low water, 21st 4 High water, 21st

oh 46m A. M. 6

59 A. M. I 12 P. M. 7 25 P. M.

EXPLANATION OF EXAMPLE 4.

On page IV of the Nautical Almanac, January 25th, it is found that the moon does not pass the meridian that astronomical date. On the 24th the moon's meridian passage is 23h 31m, which shows that the moon passes the meridian of Greenwich on the 25th (civil time) at 11h 37m A.M. Then of course the astronomical date and time would be 24d 23h 37m. To this add the correction 10m for longitude 5 hours west, which gives the moon's upper transit at the meridian of Charleston, to which is added the high water interval 7h 20m, and the result will be the astronomical date and time of high water, which is 25d 7h 7m, and being less than 12 hours is also civil time P.M.

To the moon's upper transit at the meridian of Charleston, 24d 23h 47m, add the low water interval, lh 10m, and the result will be the astronomical date and time of low water, which is 25d 00h 57m, and being less than 12 hours is also civil time P.M.

The lower transit is found by adding together the moon's meridian passages for the 23rd and the 24th, taking care to include the days and dividing by 2, which gives the moon's lower transit at Greenwich, to which is added the correction 10m for longitude 5 hours west, and the result will be the moon's lower transit at Charleston. To this add the high water interval, 7h 20m, which gives the astronomical date and time of high water, which is 24d 18h 39m. To this add 1 day and subtract 12 hours to convert the astronomical time into civil time the 25th, 6h 39m A.M.

To the moon's lower transit at Charleston, 24d llh 19m, add the low water interval, lh 10m, which gives the astronomical date and time of low water, 24d 12h 29m. To this add 1 day and subtract 12 hour to convert the astronomical time into civil time the 25th, Oh 29m A.M.

4. Example: January 25, 1914. Find the times of high waters and low waters at Charleston, S. C.

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I Low water, 25th
2 High water, 25th
3 Low water, 25th
4 High water, 25th

oh 29m A. M. 6

39 A. M. O

57 P. M. 7

07 P. M.

BY UPPER TRANSIT.

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Moon's mer. pass. 24th N. A.
Cor. for long. 5h W.
Moon's upper transit Charleston
High water interval
High water (civil time)
1/4 lunar day
Low water (civil time)
14 lunar day
High water (ast. time)
Add 1 day and sub. 12 hours
High water (civil time)
14 lunar day
Low water (civil time)

07 P.M. 13 54 P.M. 13

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1 Low water, 25th 2 High water, 25th 3 Low water, 25th 4 High water, 25th

oh 28m A. M. 6

41 A. M.

54 P. M. 7

07 P. M.

EXPLANATION OF EXAMPLE 5.

On page IV of the Nautical Almanac, January 9th, the moon's meridian passage at Greenwich is 10h 00m. If either the high or low water intervals are added to it, it is clear that the resulting times of tides will be on the 10th, but they are not wanted for that date. On the 8th the moon's meridian passage is 9h 4m, which would be expressed as 8d 09h 04m, to which is added the correction 10m for longitude 5 hours west, which gives the moon's upper transit at Savannah. To this add the high water interval, 8h 13m, and the result will be the astronomical date and time of high water, 8d 17h 27m. To this add 1 day and subtract 12 hours to convert the astronomical time into civil time the 9th, 5h 27m A.M.

To the moon's upper transit at Savannah, 8d 21h 42m, add the low water interval, 3h 7m, and the result will be the astronomical date and time of low water, 8d 12h 21m. To this add 1 day and subtract 12 hours to convert the astronomical time into civil time the 9th, Oh 21m A.M.

The lower transit is found by adding together the moon's meridian passages for the 8th and the 9th, taking care to include the days dividing by 2, which gives the moon's lower transit at Greenwich, to which is added the correction 10m for longitude 5 hours west, which gives the moon's lower transit at Savannah. To this add the high water interval, 8h 13m, and the result will be the astronomical date and time of high water, 9d 05h 55m, and being less than 12 hours is also civil time P.M.

To the moon's lower transit at Savannah, 8d 21h 42m, add the low water interval, 3h 07m, which gives the astronomical date and time of low water, 9d 00h 49m, and being less than 12 hours is also civil time P.M.

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