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the afternoon of the same day. The tide thus found is the first after the Moon's culmination. The second tide occurs 12 hours and 26 minutes later than the first.

The Establishment of the Port," in the above table is the mean interval between the time of the Moon's meridian passage and the time of high-water succeeding that transit. The true interval caries with the Moon's age, being least when the moon culminates about 4h. 30m. and greatest when culminating about 10 o'clock, and at the mean, generally when the moon is two days old. It sometimes happens that the tide comes in several hours later or earlier than the most learned calculation would determine, in consequence of the strength and direction of the wind, which the calculator cannot reckon upon.

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To ascertain when any Star found in the preceding Table will be on the upper meridian, add the numbers opposite in the left-hand column of figures to the time of "Sidereal Noon" found in the calendar pages. For the RISING of a star, subtract the number opposite in the right-hand column of figures from its meridian passage. For the setting of a star, add the same number to its meridian passage. Those marked (.........) revolve in a circle of perpetual apparition, and do not rise nor set north of the latitude of New York (40° 42′ 40′′), for which latitude the semidiurnal arcs are calculated. The civil day begins at midnight, and consequently 24 hours after midnight, or 12 hours from noon, is morning of the succeeding day; and more than 24 hours from noon, is evening of the next day. From 12h. to 24h. from midnight, or from Oh. to 12h. from noon, will be in the afternoon of the same day. This table is arranged in the order of culmination.

SURVEYORS AND CIVIL ENGINEERS may obtain the declination of the magnetic needle by observations on the Pole Star when upon the meridian, or when at its greatest elongation east or west. POLARIS and other stars pass the lower meridian 11h. 58m. after their upper transit. To the time of upper transit of Polaris, add 5h. 54m. and it gives the time of greatest estern elongation. If the 5h. 54m. be subtracted from the time of upper transit, it will give the time of greatest eastern elongation. Observations made at the time of greatest elongation are less liable to error than those made at the time of transit. The mean distance of Polaris frota the pole this year is 1° 23′ 20". To find its azimuth for any latitude, take from 18.384502 the garithmic cosine of the latitude, and the remainder is the logarithmic sine of the azimuth

PLACES.

TABLE OF LATITUDE AND LONGITUDE.

[A star indicates that the position of such places has been only approximately determined.]

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