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

196 THIE CPLJANETS.
covered, and for its symbol the character A was chosen — an
altar surmounoited with a censeri holding the sacred fire.' It is
one of tlhe largest of the asteroids, and has sometimes been seen
lby the naked eye.
327. Jfrom 1t807 to 1845, a period of nearly forty years, no
more of these small planets were discovered, and, Iup to this
time, by the asteroids were meant the four little planets already
enumerated........ Cores, allas, J11uno10 and Vesta. lMeanwhile
very accurate maps of the stars, including all up to the tcleth
magnitude, had been published, especially in the region of the
zod(iac, and astronomers scrutinizedl these with such extreme
closeness, that any wanderer appearing among them was likely
to I)e immediately dctcctcd. Since 11845, new ones have been
added to the list nearly cvcery year. At the beginning of 1850,
tihe whole numbcer known was 10; of 1855, 23; of 8G60, 57.'lThougih feminine mythological names have bCeen applieCl to
nearly all of them, yet thcy ar l better dcsignatcd by a small
circle inclosing a numbellcr which expresses the order of their
discovery' thus Ceres is,i;'lhetis,,; Paindora,, Q&c.
Tlhcy vary somewhat in theilr mean distanccs, and of course
in tlheir periods. Some of thcem have orbits more eccentric,
and otheris more inclined to the ecliptic, than any of the larger
planets. They are too small to be measured with any certainty;
the largest, Ceres, is not estimated to be more than 160 miles in
diaimeter. It is probable that all of them united would form
but all inconsiderable planet. Some of them are attended by at
nebulosity, which ilndicatcs that tlhey have an extensive atmosplcire. Thec different planetoids have been first discovered by
observers of )many countries.n........ngland, Francc, Qermany, Italy,
and America.
3128. JUPri:cE is distinguistched firom all the other planets by
Ihis great magl-nitude. I[is (diameter is 89,000 miles, being more
than 1I1 times, and his volume more tlhanl 1400 times that of the
earthl. lis fligure is strikingly splheroidal, the equatorial cxcecdlig thle lpolar dinnetot in the ratio of 107 to 100,'' wllich
is 21 timecs as great as the earth'-s ellipticity. Thl'is flattening. kv.....chl....