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

MI ANI) AND TRUE: PfLACES 01;,' tE SUbN. 1t
I 9. Since the points of the annuat l orblit, lwhere thte sttll is
at thie greatest and least distantces firon the eart', change thoirt
poSition witl respiect to thtl solstices, a slow etallst is occasi(oned ill the duration of the respective setsol. For, let tlhe
peirihelion correslpond to the place of theC winter solstice,'tS
was the case in thie year 1 I8; thenlt as thle su ti movcs more
rtipitlliy in that pirt of his' orbtit, the winter seasoll will be
slhorter tllan the sutimmer. But, again, let tlte )erilltlion lbe at
tlte sllller solstice, eas it will be itt thi'year I 1740jx then teto
Slun will move lmnost rapi'dly thlrtougll the sunutler montltlsi, thlsatd
the \winte-rs wAill lbe longer than tle snlumers. At pre sent. thte
perilleliotl is so nearli tho winter solstice, thtat, the year being
dividled into sumlmer and winter by the ctuinoxcs, tlte six
wintr montlhsl are )assed over between seven atd eighlt days
sooner tihan the smnmnter m1onthls.
MtESAN ANt) TRUEl PLtACES8 OiF TJUEJ S UN.
$99. I/t.7.it, /tofion of a.ny2 body rl voi'ovig zint (.t rbit,
is tfhat wlic/ wou ha, it vooldv lave,, in tie sfet time, it'CUolvted
vtw'br-m'~t'lqy i2,t ia circle.
In surveySing an irregular field, it is colmon first to strike
out sotie r.egular figure, as a square or' a ptarallelogramt, by runnill' lonig les, anld disrecgartdin any sall irregularities ill
the boundaries of the fieldl. IBy thlis process, -we obtain anll approximation to tle eCoitents of the fiel1d, althlough} we lhave perIlatps thlrown out sweveral small portions whtich. b)elong to it, and
iltclcl d at number of otlelmrs which (lo nlot belolng to it. Itliest
tbeing separaty titImatetd tand a(lle to or subtracted fitom
our' first conlllutation, twe obtain tlhe true area of the field. -In1
a similar manner, we )proceed in fin(ling tle ) pltce of at heavenly blody, whicht moves in aln orbit more or less irre}gular. Th11tus
we esti mate the suin's distance fi'ont the vernal equtiox for every
davy of tile ycar at noon, on thie supposition that lie moves mlifomnlly in a circular orbit: This is thle sun's mean2fl t dlfith..
We then apply)) to this result Nvarious corrections for thle irregulality of tile sunll's lmotions) atd tthus obtain thie true longyitud'le.
200. The corrections applied to tlhe mean motions of a licav3 t.....................
a: Blot.