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Year. Names of the Months.

5608 Tisri, 16th, *Second Feast of the Huts, Sept. 26, 1847.

""21st, Feast of Palms or Branches, Oct. 1,"

""22d, *End of the Hut or Congregation Feast,- •• Oct. 2," ""23d, *Rejoicing for the Discovery of the Law, • • Oct. 3,"

"Marchcsvan begins, Oct. 11,

"Ohisleu begins, Nov. 9,'

"" 25th, Consecration of the Temple, Dec. 3,"

"Thebet begins, Dec. 8,

"" loth, Fast for the Siege of Jerusalem, Dec. 17,"

The Jewish year generally contains 354 days, or 12 lunations of the Moon, but in a cycle of 19 years, an intercalary month, (Veader) is 7 times introduced, for the purpose of rendering the average duration of the year nearly or quite correct.

MAHOMETAN CALENDAR.

Year. Names of the Months.

1263 Muharrem begins, Dec. 20, 1846.

"Saphar" Jan. 19,1847.

"Rabial." Feb. 17,"

"Rabiall." Mar. 19,"

"Jomadhi I. -" April 17,"

"Jomadhi II." May 17,"

"Redjeb" June 15,"

"Chaban" July 15,"

"Ramadan "(Month of Fasting) Aug. 13,"

"Schewall "(Bairam) Sept. 12,"

"Dsu'l-kadah" Oct. 11,"

"Dsu'l-hejjah" Nov. 10,"

1264 Muharrem" Dec. 9,"

The Mahometan Era dates from the flight of Mahomet to Medina, July 16th, A. D. 622.

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 354J^ 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.

Year. Names of the Months. 5608 Tisri, 16th, *Second Feast of the Huts,. . . . . . . . . . . . . Sept. 26, 1847. to “ 21st, Feast of Palms or Branches," . . . . . . . . . . . . Oct. 1, “ 4. “ 22d, *End of the Hut or Congregation Feast,--- Oct. 2, it. * 23d, *Rejoicing for the Discovery of the Law, ... Oct. 3, “

“ Marchesvan begins, - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - • Oct. 11, “ “ Chisleu begins,” ------- ----------------- - - - - - - - - - - Nov. 9, “ o: 4. 25th, Consecration of the Temple,' . . . . . . . . . . Dec. 3, “ * Thebet begins,” - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Dec. 8, “ 4. 4. 10th, Fast for the Siege of Jerusalem,' . . . . . . . Dec. 17, “

The Jewish year generally contains 354 days, or 12 lunations of the Moon, but in a cycle of 19 years, an intercalary month, (Weader) is 7 times introduced, for the purpose of rendering the average duration of the year nearly or quite correct.

MAHOMETAN CALENDAR.

Year. Names of the Months.

1263 Muharrem begins, - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Dec. 20, 1846. 4. Saphar “. . . . . . . . . - - - - - - - - - - - - - - - - - - - - - - Jan. 19, 1847. “ Rabia I. “. . . . . . . . . . . . . . . . . - - - - - - - - - - - - - - Feb. 17, “ “ Rabia II. “. . . . . . . . . . . . . - - - - - - - - - - - - - - - - - Mar. 19, “ “ Jomadhi I. - “ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . April 17, “ “ Jomadhi II. “. . . . . . . . - - - - - - - - - - - - - - - - - - - - - - - May 17, a “ Redjeb “. . . . . . . . . - - - - - - - - - - - - - - - - - - - - - - June 15, “ “ Chaban “. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . July 15, “ “ Ramadan “ (Month of Fasting) . . . . . . . . . . . . Aug. 13, “ “ Schewall “ (Bairam) . . . . . . . . . . . - - - - - - - - - • Sept. 12, “ “ Dsu'l-kadah “. . . . . . . . . . . . . . . . . . . . . . . - - - - - - - - Oct. 11, “ ... Dsu'l-heijah “. . . . . . . . . . . . . . - - - - - - - - - - - - - - - - - Nov. 10, “

1264 Muharrem “. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dec. 9, “

The Mahometan Era dates from the flight of Mahomet to Medina, July 16th, A. D. 622.

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 1847.

Computed by the Formula of Laplace, (Mécanique Céleste, Vol. II. pp. 289, Paris ed., and [2858] Bowd. ed.)

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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 opposition, 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 1847 will be those of January 18, February 16, March 18, April 17, August 27, September 25, and October 25. The actual rise of the tide, however, depends so much on 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.

HEIGHT OF THE GREATEST OR SPRING TIDES IN 1847.

Computed by the Formula of Laplace, (IfccanitIue Celeste, Vol. II. pp. 289, Paris erf., and [2858] Bated, ed.)

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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 opposition, 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 1847 will be those of January 18, February 16, March 18, April 17, August 27, September 25, and October 25.

The actual rise of the tide, however, depends so much on 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 farther 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.

DARKNESS OF THE NIGHTS DURING THE YEAR 1847.

Far Boston, New Ybrfc, Philadelphia, Washington, $c.

The number of hours*at the top of the page denotes the average time for the month from w end of the evening twilight to the beginning of the morning twilight. The dots in the table denote the hours of entire darkness, when there is neither sun, ioon, nor twilight: and then* disposition denotes the hours before or after midnight.

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