fflF' ( 



Fig-. 3. 



IF^- 



Apsides 





Evemnff 



Apparent position of the Sunat 

 iliffeivnt hours of the day at the, 

 time ot the Etjuinoaces '., 



3? 



Fig. 3. 



For some tuiu- aAa-Simrset the rays 

 still illiinimr ih# Atmosphere diffw 

 'nil AanfettW flirouyh spojce.and 

 Nu/htmmeon almost insensibly, this 

 is rail <!. twilight and the rlawii is 

 a, similar Phenomenon whichpreces 

 -des Sun~rJ.se. The Solar ray S-O. 

 which enters the Atmosphere at 0. 

 instead^ ofcomino, out atMLwilL be 

 turnedasidc retrojctedorbcnt more 

 andrnare,asitpenetratesthevari' 

 -our Strata ofAir,andwillat last 

 reafh the Earth describing the Curve 

 O.G. The Observer atG.wouldthus 

 see the Sunmuch longeratE, thanhe 



The- effect o fthe dawn is the reverse 

 o fthis -let the Earth be represented 

 by AB.CD.andG.wheretheSufi-rises. 

 thehorizonatJLGRre^cen-esaghtrrom 

 all parts oftheHeavens either directly 

 orby reflection.. thepointA at which the 

 Sunhasrwtactualfy' risen, has above its 



mospherc KLR. indirectly illuminated 



e feeble until it reaches R. 

 ts utmost limit abm-e the horizon atB.it 

 , . where the Sun, is Rising 



thewh^leofthehonzonifiJJiirninatedwhile at 

 the lenticular portions oftheHeavens T.lf.X. 

 only rweiveligTit. The eoctent of 'twilight issheww 



/9O West Long. 



46 West Long.; 9 o 'dock by the effect of Atmospheric at- 

 lnniu>n thfSun.wouldappeartobeat3.atQ '45 East Long, 

 ' 



e leinyatY. turns oniisAjcistroTnJVesttoEast,as inr 

 dicaletlbythcArmws, the Sun will appear to occupy theoppesitepoinis 

 F. J. S.E.U. This fiffureis drawn at the time whenthe Sun appears to . 

 -.* y ///< the Equator . 



Inclination of the Orliit to the Echptic 

 ^feaii distance Iroiu tlie Sun in lea^nies 

 Sidereal revolution round the Sun 

 Diameter, in leap-lies 



Velocity per inuinte. in leagni.es 



Tune of rotation upon its axis 



MERCURY \-ENFS 



70 ' 3 23 



13. 367 . OOO 24. f>G(>. OOO 

 87 Jin-s f)7 224davs 70 



1.130 '.2.787 



653 485 



er , Peiitonville . I nuctoa. 



