An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

C iJ Arl PTEl, fR V.
OF Til: MYOON LUNAR GEOOAPIYy'............iE ASES OF TILE MOON0 -—.IEUI:tEVOLUTIONS.
201. INxE:T to tflc Sun, the Mloon naturally claims our atten
tion.
ThIe AMoon is an attendant or satellitoe o t te ctarth, aroundl
wllich sle retvolves at tle distance of niearly 2-40,000 miles.
If [cl mean horizontal parallax being 57' 09",'{' consequently,
sin 57' 09": se ni- diamnete of thc e arth (3956.2):: rad: 238,5a5.
(Art. 87.)
the mrioonl's avpparnt diamneter is 31' 7", and her real db a i eter
2:160 mliles. 11r
Rttad: 238,545 sil 331' < O19.6. -nioon's scin0i-d ialeter. (See Figv. 26, ). 71..)
And, since spheres are as the cubes of the diameters, the
votruime of the moon is: %- that of the earth. Xier dtcnS.tity is
nearly ]- (.611.5) the density of the ea rth, and her mnass ( -:,x.01.5) is about'.o
202. ITl.} moon shines by reflect3d l/g/it borrowed fr'om thl
su11l, and, wheln fill, oxhtibits at disk of' silverty brig l tltess, divrclsifield b extensive portions partially stltmed. A Ivy thl aid
of the telescope, we see undoulbte( sicgns of a varied surfaitc,
composed of extenlsirve tracts of level country, and muncrolus
mountainsl and valleys.
20:3. Ti' line which separates the enlilghtened friom tthe
dark iportiolns of the moonoh's disk, is called thi e Tcrm;inator.
(See Fig. 2, 15'o;ntiapice.) As the terminator traverscs the
disk from noew to full ml{oon, it app)ears" throtgll thel telCescopC
exceedingly brollen iln some part s, t)ut sooth il otthers, dicating' that so-ne portions of the lunar surfaee are lneve l n whilo
* ele..,yrfaplhy is a worVd more apnpropriate to a desciiption of the moon, but is
mat lcrhaps sutiicieltlv fitmitilarizct by use.
F IMly's Astroion-ical tahes.