vn VRN.U.MOTFOX OTTHK MOO.V. 



The Moon .revolving round the Earth and accompanying it in; 

 1 its annual revolution round the Sun, describes ~a peculiar' 

 curve in the heavens termed an Epicycloid -This cun-e is 

 formed of 22 arcs and one third nearly &&.3..\.l.etthe 

 \Earth .^.advance an 8* part of 30 dyrees to t.theMoon. 

 whidi was at first at L. will hai'e described round the 

 Earth the arc n . S. or. an H^part of a htnation. at the 

 same time accompanying the Earth in its progress, will 

 hat-e traced in the heavens the portion of 'the Epicycloid 

 L-S. It is by a combination of the movements previous 

 ly noticed that the Moons phases or the various aspects 

 under which she is seen from the Earth, are caused. The 

 central figure illustrates these changes oftheMooris 

 appearance - thus, when in conjunction Le. between the 

 Sun and the Earth . she is not visible because her dark 

 side is turned towards us and she reaches the merid: 

 ion at noon, it is then New Moon rather less than four 

 days after, the Moon which has reached the meridian 

 ^ or an hour later each daj',is perceivedasa slender 

 crescent with its points towards the east.sheis thtn.4 '?. 

 distant from the point of coryunction, at her first Oc 

 tant when only a fourth part of her illuminated surface 

 is seen from the Earth as marked at TSL.O she then reach 

 es the meridian at 3 o dock in the afternoon . Arrived 

 at ,9fff me point of conjunction .half of her disk is visible, 

 she is then said to be in her first quarter reaches the 

 meridian at 6 in p\e evening.. It 235? is her second Octant 

 when $" of her disk are visible, she then reaches the mer- 

 'dian at 9 in the evenina. .It 1809 from the first point in 

 er orbit, she will be of am on the same line, in opposition 

 with the Sun.f wiS present te the Earth the whole of her HI 

 -uminated disk.reachina the meridian at midniaht it is then 

 fill Moon . Passina from this point in her orbit ike Moon bea- 

 'ins to wane & three or tour days after at 225 is in her third Oc- \ 

 r -tant. reachina the meridian at 3 in the morning X turning towards 

 the Earth "5? of her disk as in her second Octant thus rrfdbiting in 

 'er decline appearances analogous to those in the earlier part of 

 revolution . The two pointful the Moons orbit where she is in 

 ippofition or in con/unction with me Sun are named Svzvgies.and 

 'here she is in her first and last quarters Quadratures . 



Prawn * Engrvi brlDow 



