OF Ttf 



VISIBLE HEMISPHERE 



OF THE 



/// order to understand the phenomena exhibited by the Moon, 

 tliemost earend ami accurate obsen-atian of every part' of the 

 batardiftc is required, at all the various periods of her libm 

 lion .Thcposilii'ii of remain-able spots must be determined 

 witli the most nuourous exactitude 1 , as it is found , rn>, 

 the chanac of situation relative to surroundini/ af>pear 

 iince.v. consequent upon tfie Moons phases, tiuit.a. spot 

 clearly ilistiiu/idshablc by the naked eve upon hers or 

 nice, when at the ndl.will be witJi difficulty discerned 

 even lv the a lass towaJ-ds t/ie hist quarter . 

 Tfie tippearanees ohsen'txL on theModn's swr'aee are 

 caused.either bv ditTerencc of level, or bv differ 

 -ence of the intensity of the liqht . The liaht ref- 

 lected from the suirlnce of the Moon is plain Iv 

 sec// to be of different shades; although die liaht 

 -er parts aiv tjencraUv the mountains, < the dark 

 cr flics the low plains , still .airctnl ebtert&Umt 

 have shown that this is not alwavs the cnse. 

 but that, the streaks of light, whiefi at the full 

 surftassin bril/ia/uv all the adjacent parts. some 

 times e.rist entirely independent of mountains, 

 and extend alike over heiahts and valleys with 

 out being affected bv them . Besides difference 

 in intensity- of the h'aht. colows spedru-ally differ 

 ent may be observed. partindarly green .sometimes 

 a colour of a reddish tint .at others a vellcwish brown. 

 The clwatioJis oftiicMoon are in general of a much 

 more precipitous natju-e than those of the earth. In the 

 plate, the edaes of the steeper craters, more especially 

 tiiose of small e.rtent .are generally sluwn by a plain line .. 

 the namnv defts ornu-ines b\ pamlel fines without a cross 

 \ tint . The middle edfje of the Noon, i.e.thearmt circle which 

 in the mean libration seperates the hemisplierc wMdi is visible 

 from that which is invisible: is necessarily deluieated in profile. 

 Chains of mountains . or mountainous regions of am' importance.are 

 named after tfic mountains of the carth.and the various spots after 

 distinguished men. as annexed . To avoid confusuuj the objects in th 

 plate bv a pronision of figures, the Moon's sufrace is divided into four 

 parts, the 7iumbering of the spots m each commmcinq witfi unit. 



SCALE 



ZOO 22O 



