Hie central fioiire represents the Moons phases .around the Earth 

 frimrd in the' centre the elliptical lute. AAAA. indicates the path 

 of the Moon revolving, from west to east, at eight points L ' 

 her orbit. The Moon 'is shown or' her exact reiata-e site to to, 

 Earfh her distance is however about ten ame.t greater in pro 

 portion within the lunar orbit the Moons phases, are repres 

 ented on an enlarged disk, in order to show the principal spoti 

 The Moon is the '.rateltitr or' me Earth, that is whil.tr the 

 Earth pert/inns its annual revoudion round the Su/i . the 

 Moon accompanies the Earth revolving also around it. The 

 Moons orbit is an ellipse the Earth occupying one of the 

 foci its ejrcmtricih' is about 47.1O leagues' the nirundis 

 tancf being aboitf 86OOO leagues. From the figure of her 

 orbit the 'Moon is sometimes'' nearer than ai others: the 

 point at which she is nearest is called Peritfee fiirl.P. 

 that at which she is farthest Apogee fip.T.A. Thi I'eri 

 fer and *4pogee advance e\er\- vear about 4<JT41'.46" 

 'from west tb atst . The plane 'of the lunar orbit makes 

 tin angle of 5? o. 49. with the ediptic. fig.4. The planes 

 of the two urbits <ire mt h\ n liiie passing through the 

 centre of we. forth . the two points where'this line meets 

 the Moons orbit are me Nodes one. the ascending node, 

 alien (he ittoon ri.te.t above the ediptic towards the north 

 the omer the descending node when she .links below it to 

 wards the south, see Stg.ft . The nodes advance evert' year 

 about 19? 2(>. 29 in an opposite direction toherorhiciiliir 

 [motion . Let the Moon. L.&g.G.beata point of her orbit 

 L-n.befow the ecliptic. advancing towards MTOMMMM 

 node the Suns attraction will be in the direction J..S. tKe 

 intensift' of this force being represented bv the line L.a.it 

 may he decomposed into two forces one.L.T towards the 

 centre of the Earth, the other. LJD. towards the plane of the 

 ecliptic . the action of these two forces would give the Moon 

 an intermediate direction . L.x.o. and cause her to cross soot 

 er the plane 01 the ecliptic . The arc described above theh 

 raon oy the Moon in su/nmer appears much smaller the,, 

 that described by her in winter: it is thus ejcplainfd on the 

 night of the waiter solstice 21? or 22'tliecember the Earth 

 ' T fir 2 sees the Sun, <it S on the tropic of Capricorn Jl tneJfcw. 

 at Lon the tropic of Conor, the line of our horuon, TAR shows 

 that the air described above it or the Sun is very snuill bilst 

 thiit described by the Moon is very ejctended. One complete ret-ol , 

 utinii of the Moon round the Earth that is. from one point of her 

 orbit to the same point again, is called a Periodical revolution and 

 is performed in 2/dars fhours 43 minutes. 4t seconds. 3'ow suppos 

 ing the Moon L.&g.T.at tne bey inning of her revolution, tobem con 

 junction i.e between the Sun and tKe Earth .& that these three bodiet 

 'and a star E. are on the same line R..- at the end of her rn-nlntin 



the Knrth having tuhimceil in its orbit, she will bt at n in the plane , 



parallel to K. E. to be again in conjunction she must, therefore describe , 

 on the arc n. L.a number of degrees equal to the arc T. t . or TA.1A.des , 

 eribed bv the Earth. The Svnodiral revolution or Lnnar month is the in - , 

 ' tervni from one conjunction to anottier a period of 29 davs 22 hours 

 \44 minutes 3 seconds. 



EPICYCLOJu 



F, s -. : 



