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

1 (-3'ri MOON.
(eoll)ar:ed with that of the m1oon0, we might SlPpl)Ose that his
a:ttionl ill raising' the tiles would be greater t than the moon's;
but the nearness of the moon to thle earth more than compensate's toir the suln's greater quantity of matter. et us, lhotwever,
foiitl a just conception of tile advantage which tile mooll derives ftroml her proximity. It is not tllat her actual amount of
attraction is thus rendered greater than tlhat of tle stun; but it
is thlatt her attraction for the dI7}'jIvrent..)ar-ts of the earthll is very
unequal, while thlat of tle sun is nearly uniform. it is tlle itneq;(ual-ity of tis actionl, and not the absolute force, that pro(luces the tiides.'The diameter of tile earth is.7o- of the distance
of thle mloon, while it is less than y-ij0-6 of thi distance of the
st11l.
28.3. tlaving now learned the gineral cause of the tides,
we will next attend to tile explanation of pdarticularyy h lrelomenc,
Twice aSri tides, or those which rise to an unusual height
twi ce 1, 1mo0th, arle produced by the sun and moon's acting in
a linle; and tmhe Nte/ap tides, olr those whlich are unusually low
twice a monltll, are prodlccd by tile silun and mIoon's acting 90
ttdegrees fron eacht other. the7tc Springl- tides occur at the syzytgics;
thile Neap tides at tile quadratures..At the time of new moonl
t le sun anul moon both beinlg oil tflhe same side of t;he earth,
~nl1d acting' upon it in the same line, their actions1 cospire, and
tile sun mlay be considered as adding so miluch to the force of
thie moon.'We have already expclained how the moolt collntri)lbutes to raise a title on the opplosite side of t}he eartlh. But
thle sunll as well as the nmIoon rtaises its own tilde-wave, v1which, at
new 1moon1, coincides with the lunar tide-wave. At full moon
also, the two lulninaries conspire ill tile samXe way to raise the
tide; for we must recollect that. each bo1dy contributes to raise
the tide on the opposite side of the earth as well as onl tlhe side
learest to it. At botll thle conjunctionss ald opl)positions, therefire, that is, at tlie sfyz)ygis, w) \ ave unusually hligll tides.
lBut Iere also tile maximunl eflect is not at the moment of tihe
syzygies, b1ut 36 ]holr s afterward.
A.t tile qua.:dratures, the solar wave is lowest wherTe the llunar
watve, is highest; hencl the low tfide producedtil by the stun is
tmlltractetl fiomnl highlt waterl and prodluce tle -Nea) titldes.
MlNolreover, at tile qlurltalttures the solar wave is higyhest whllerle