The effect of a moon-light evening is exquifitely grand and majeftic; it is the world's great picture," not indeed in the lively colours of day, but more delicately fhaded, and arrayed in fofter charms. Now reigns Full orb'd the moon, and with more pleafing light Shadowy fets off the face of things. MILTON. Homer, according to Pope, has exhibited, in the following lines, the finest night piece in poetry; and, as Hervey juftly remarks, if they are fo beautiful in the original, who can fufpect their fuffering any difadvantage from the pen of his admirable translator? As when the moon, refulgent lamp of night, ILIAD VIII. PROBLEM LXXXVIII. To prepare the Globe for folving fome of the fubJequent Lunar Problems. Faften a filken line over the furface of the globe, exactly on the ecliptic. This may be afterwards removed moved towards the North or South, juft equal the latitude of the moon's orbit or path in the avens; and the points of interfection with the liptic, called the Nodes, will be fuch as the ble in the ephemeris affigns for every fixth y in the year. That point of interfection, or node, of the nar orbit, in which the afcends from the Southern the Northern part, is called the Afcending ode, or fometimes the Dragon's-Head, and is iftinguished by this character ; and the other ode, or Dragon's-Tail, is reprefented by the me character inverted thus . This laft node not noticed in the ephemeris, because the place f one being given, the fituation of the other is mmediately known, being diametrically oppofite o it. Thus, for inftance, if on any particular day the place of the afcending node were found to be in a certain degree of Taurus, the defcending mode would be in the fame degree of the oppofite ign, Scorpio. See page 39.. By infpecting the ephemeris it will appear, that the motion of the lunar nodes through the figns of the ecliptic is fo extremely flow, as to alter but very little in the fpace of a month. They move only about 19 degrees in a year, and of courfe take almoft 19 years to make an entire revolution through the ecliptic. This motion is retrograde, or, as it is fometimes termed, in antecedentia, i. e. contrary to the order of the figns: thus the afcending node for January the firft of the year 1797, was 1° 12′ of Cancer; and for December the 25th, 12° 14' of Gemini. See White's Ephemeris. PROBLEM. LXXXIX. PROBLEM To find the Nodes of the Moon's Orbit for any given Time, by the Ephemeris and Globe. Seek the moon's afcending node in the table of geocentric motions of the planets in the ephe meris, where there is a column which thews the fign, degree, and minutes of the place of this node for every fixth day. Bring the correfponding part of the ecliptic upon the globe to the brazen meridian; turn the globe precifely half a revolu tion, reckoned by the hour circle, and the degree of the ecliptic then in contact with the meridian is the moon's defcending node. EXAMPLES. The moon's afcending node on the 19th of October of the year 1797 was 15° 47′ of Gemini, what was her defcending node? Anf. 15° 47′ of Sagittarius. Required the moon's afcending nodes for the following days, and the correfponding defcending nodes: January 1-February 7-March 8-April 1May 3-June 3-July 1-Auguft 1-September 9 -October 17-November 1-December 1. PROBLEM XC. To affign the Orbit of the Moon its proper Pofition in the Heavens for any Time. Having found the moon's nodes by the preceding Problem, confine the filk line mentioned in the 88th ith Problem, at thefe Points; and at 90 degrees ɔm them, reckoned upon the ecliptic, elevate d deprefs the line to the moon's greateft latide, namely, about 5 degrees on either fide of e ecliptic. Thefe distances are eafily determined by the rcles of latitude which pafs through every degree om the ecliptic to the extent of the zodiac; and e filk line in this pofition will represent the inar orbit, or path, in the heavens for the proofed day. "o find the Moon's diurnal Motion in the Ecliptic for any given Day. The quantity of the moon's diurnal motion for any day is obtained by taking the difference between it and that of the preceding day, thus: find her place, i. e. her longitude for the noon of the given day in the ephemeris, and fubtract from it her place on the foregoing day at noon; the difference of these longitudes will be the space that fhe has described for that day, and is the quantity of the diurnal motion required. For example, let her diurnal motion be required for the 11th of May 1797. On the 11th of May her place was .... The diurnal motion fought ·m 28° 5° m 15 18 12 47 N. B. The moon's diurnal motion varies from about 11 deg. 46 min. the leaft, to 15 deg. 16 min, when greatest. EXAMPLES. EXAMPLES. Required the moon's diurnal motion for the following days: January February 7-March 8-April 1May 3-June 3-July 1-Auguft 1-September 9 -October 17-November 1-December 1. PROBLEM XCII. To find the Moon's Place in the Ecliptic for any given Hour of the Day. Find, by the ephemeris, the moon's place in the ecliptic for the given day at noon; and, by the laft Problem, the space fhe has defcribed fince noon, to the given time: this, added to the former, will be her place in the ecliptic, at the hour required. Thus, on the 10th of May her place at noon was 15 deg. 18 min. of m, and as her diurnal motion for that day was 12 deg. 47 min. in nine hours fhe will have paffed over 4 deg. 47 min. which, added to her place at noon, will give 20 deg. 5 min. of m for her place on the 10th of May, at 9 o'clock at night. EXAMPLES. Required the moon's place in the ecliptic at the following hours on the annexed days: January 20, five in the evening-February 14, fix-March 9, feven-April 22, eight-May 19, nine-June 8, ten-July 18, eleven-Auguft 27, * Found thus by the rule of proportion: As 24 hours: 12 deg. 47 min. :: 9 hours : 4 deg. 47 min. midnight |