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EXPLANATION OF EXAMPLE 2.

On page IV of the Nautical Almanac, January 11th, the moon's meridian passage is Ilh 59m, which is very near the end of the civil day. 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 12th; but they are not wanted for that date. On the 10th the moon's meridian passage is 10h 59m and including the day it is 10d 10h 59m, to which the correction 10m for longitude 5 hours west is added, giving the moon's upper transit at Philadelphia. To this add the high water interval 1h 28m, and the result will be the astronomical date and time of high water, 10d 12h 37m. To this add 1 day and subtract 12 hours to convert the astronomical time into civil time the 11th, Oh 37m A.M.

To the moon's upper transit at Philadelphia add the low water interval 8h 58m, which gives the astronomical date and time of low water, 10d 20h 07m. Add 1 day and subtract 12 hours to convert the astronomical time into civil time the 11th, 8h 07m A.M.

The lower transit is found by adding together the moon's meridian passages for the 10th and the 11th, taking care to include the days and dividing by 2, to which is added the correction 10m for longitude 5 hours west, and the result will be the moon's lower transit at Philadelphia. To this add the high water interval, lh 28m, and the result will be the astronomical date and time of high water, which is 1ld 01h 07m, and being less than 12 hours is also civil time P.M.

To the moon's lower transit at Philadelphia add the low water interval, 8h 58m, and the result will be the astronomical date and time of low water, ild 08h 37m, and being less than 12 hours is also civil time P.M.

2. Example: January 11, 1914. Find the times of high waters and low waters at Philadelphia, Pa.

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EXPLANATION OF EXAMPLE 3.

On page IV of the Nautical Almanac, January 20th, the moon's meridian passage is 19h 48m, which shows that the moon passes the meridian of Greenwich on the 21st at 7h 48m A.M. Then of course the astronomical date and time would be 20d 19h 48m. To this add the correction 10m for longitude 5 hours west, which gives the moon's upper transit at the meridian of Boston, to which is added the high water interval, 1lh 27m, and the result will be the astronomical date and time of high water, which is 210 07h 25m, and being less than 12 hours is also civil time P.M.

To the moon's upper transit at the meridian of Boston, 20d 19h 58m, add the low water interval, 5h 17m, which gives the astronomical date and time of low water, 21d 01h 15m, 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 19th and the 20th, 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 to this add the high water interval, llh 27m, and the result will be the astronomical date and time of high water, which is 20d 18h 57m. Add 1 day and subtract 12 hours to convert the astr mical time into civil time the 21st, 6h 57m A.M.

To the moon's lower transit at the meridian of Boston, 200 7h 30m, add the low water interval, 5h 17m, which gives the astronomical date and time of low water, which is 20d 12h 47m. To this add 1 day and subtract 12 hours to convert the astronomical time into civil time the 21st, Oh 47m A.M.

3. Example: January 21, 1914. Find the times of high waters and low waters at Boston, Mass. (Navy Yard).

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