The sign is prefixed to the latitude, or declination, of the Sun, or other heavenly body, when north, and the sign — when south; but the former prefixed to the hourly motion of the Moon in latitude, indicates that she is approaching, and the latter that she is receding from, the north pole of the ecliptic, The letters M. A., m. a., denote Morning and Afternoon. CHRONOLOGICAL CYCLES. Dominical Letter, Epact 22 Roman Indiction, Lunar Cycle, or Golden Number, 3 Julian Period, "north of Equator, (Spring and Summer) 186 11 10 9 "south of 66 (Winter and Autumn) 178 18 45 49 Length of the tropical year, commencing at the winter solstice, 1843, and termi- 365 5 55 58 nating at the winter solstice, 1844, Mean or average length of the tropical year, 365 5 48 49 JEWISH CALENDAR. [The anniversaries marked with an asterisk (*) are to be strictly observed.] Year. Names of the Months. The Jewish year generally contains 354 days, or 12 lunations of the Moon, but, in a cycle of 19 years, an intercalary month (Veadar) is 7 times introduced, for the purpose of rendering the average duration of the year quite or nearly correct. The Mahometan Era dates from the flight of Mahomet to Medina, July 16th, A. D. 662. The Mahometan year is purely lunar; it consists of 12 synodical periods of the Moon, or of 354 days, 19 times in a cycle of 30 years, and 11 times of 355 days. The average length of this year is therefore 354 days, which differs only thirty-three seconds from the truth; a degree of exactness that only could have been attained by a long series of observations. But as no allowance is made for the excess of 11 days in the length of a tropical year over the time of 12 revolutions of the Moon, it is obvious that in about 33 years, the above months will correspond to every season and every part of the Gregorian year. HEIGHT OF THE GREATEST OR SPRING TIDES IN 1845. Computed by the formula of Laplace (M'canique Celeste, Vol. II. pp. 289 Paris ed., and [2858] Bowd. ed.) The unit of altitude at any place, is the height at that place of that tide which arrives about a day and a half after the time of New or Full Moon, when the Sun and Moon at the moment of conjunction or opposi tion are at their mean distance from the Earth, and in the plane of the celestial equator. This unit of altitude, which must be derived from observation for each place, multiplied by the quantities in the above table, gives the height of the spring tides at that place during the present year. By the above table it appears, that the highest tides of 1845 will be those of February S, August 19, and September 17. The actual rise of the tide, however, depends so much upon the strength and direction of the wind, that it not unfrequently happens that a tide, which would, independently of these, have been small, is higher than another, otherwise much greater. But when a tide, which arrives when the Sun and Moon are in a favorable position for producing a great elevation, is still further increased by a very strong wind, the rise of the water will be uncommonly great, sufficient perhaps to cause damage. The formula, from which these tides were computed, is, however, strictly true only for Brest and its vicinity, and must be regarded as a very uncertain approximation for the coast of the United States. The following table contains the Unit of Altitude of several ports and places on the coast of America, according to the best authorities. The unit of altitude of the several places in the Bay of Fundy was ascertained by recent observations. The following Table contains the difference between the time of high water at Boston, and at a large number of places on the American coast, by which the time at any of them may be easily ascertained, by subtracting the difference at the place in question from the time at Boston, when the sign is prefixed to it; and by adding it, when the sign is +. The time of high water, in the calendar pages, is of that tide which immediately precedes the southing of the Moon. Albany Andrews, St. h. m. +4 12 Bay, Casco h. m. -045 0 0 66 Chebucto -40 Annapolis, (N. S.) Aunapolis, (Md) Augustine, St. -4 0 Narraganset Bay, Bristed Pistolet 0 0 - 3 50 353 4 45 66 Broad St. Mary's |