Bristol news. [volume] (Bristol, Va. & Tenn.) 1867-189?, 1870-02-04
Scientific.
CONSTITUTION OF THE SUN.
DIR. b. A. GOULD ON ,fHE CON.
STITUTION OF THE SIN.

A large audience assembled in the ball Of
tho Cooper Pm, ute Last evening, to listen
10 Dir. X. A. Gould Of Cambridge, Mass !,
who lectured before the American Institute,
ON the "Consttution of the Sum- The
lecture was prJfusely illustrated by photo.
graphs OF the sun, reflected with the aid of
lantern upon n background Of white cloth.
On" Of the photographs, showing spots and
facul@ was taken yesterday afternoon by
Mr.. Lewis NJ Rutherford, at his observa-
tory. and was pronounced by DR.. Gould an
excellent one. The lecturer was introduced
by Prot. Tilman, who Announced that the
last lecture of th> course will no delivered
on Friday evening next, by FIof. J. S New.
berry OF Columbia C llNge. Subjects "Ths
Colorado Plateau-lts Canons and Ruined
Cities"
DR.. Goull. upon coming forward, was
greeted wi h applause. lie said:
L,Dfrs AND GtsrLtNEN: IL would be
vain task to atierspt any invest cation Of
the history of our early astronomical
knowledge Of the sun. l'erodotus relates
that Thales 81 Miletus predicted the total
eclipse. which occurred ia the year 5s4 y.
G, during the 'irth day Of battle between
the Medes and Lydisns. aud which by its
nwe-irspiriug influence b-ougl tIisir Eve
With Hi s proSsBp R $hfsa h
Egypt, where he hsd studied, that the sun
10 tho center Of the universe, aud that the
earth revolves around him once n year
Three and half centuries later. Archime-
des correctly determined the suns apparent
diameter rs between 81 and 80.
The determination of lhs eartL's distance
from the sun is problem Of peculiar i'm
portance, inasmuch az il is the nfit in which,
by means of keppler's laws. NIL the plane
tary distances arc nea-uted. Consequently
all our knowledge If celestial distances Tex
cept ng only that of the moon) is closely
connected with the value OF thi. funda men
| tai standard of measures: aud any addition
to our knowledge, which shows any one
| adopted distance 10 he too large OF too
small, demonstrates the sams for oil the
| rest. This determination 10 mnds by the
same means used by surveyors for detect
ing terrestrial nights and distances, by
measuring the perullaI--i. e.. the difference
Of direction ia which the same object sp-
| pear, from different points Of view. Mars
aud Venus, as being the nearest to the
sarth, offer the greatest advantages for de-
| termining parallax, and many observations
| have therefore been made Of these Ilanets
at two well-dstermined points, distant from
each other on the earth's surface The base
line between them being well known aud
the direction in which the planet appears to
| the observers being carefully noted, II has
been possible to compute the length OF the
other sides of the triangle, which gives us
| the distance OF the planet, and thence can
be deducted the distance Of the sun, rs We
know the ratios of their mean distances to
that Of the earth. The actual mean distaI CO
Of the sun CORE ponding TO the most proba-
BILE value Of tho para lax II 92,390,0Oc
miles and since his apparent diameter Al
this di lance is 32'." somewhat more thar
half degree) We readily hnd the CORES
pontiing true diameter TO be Of the colossal
size represented by eel, 2S2 statute nj les
This ia nearly 100 times that Of the earth
| so that the earth, If seen from the sun
" ould appear but little more than l2.00C
part aS large as the sun appears to us Th'
velocity Of light IN stellF space, correspou
ding to this value Of the suns parallax. il
at the rate Of 1855, 900 miles in second a
mean time.
To form so,re idea Of the stupeLdous dis
tances. magnitudos, aud velocites will
which We thus become acquainted, let u
compare them with some OF those will
which we are familiar. IL We represent thu
earth by an ordinary rifle bullet, the SUI
would be Represented on the shme scaie b,
globe Of a feet in diameter ut ditane
OF 80 rods but IL we denote the earth b.
an orange Of average size, the snn woul'
appe ar as q sphere rs feet in diameter hal
mile of. We have seen that light, evel
with us inconceiyablo velocity, REQ hires
min. 3 sec. to traverse this enormous dis
tauce. An electrical signal, travelling wit
the speed upon eur telegraph wires, woul
put a girdle round {, o earth In abost ]
seconds, YET II would require hour 90 mid
to reach the sua. A locomotive engine
moving 40 miles an hour, would consum
1s3 y years In traversing the distance, aud
could We suppose an iron bar 70 exten
from the earth 10 the sun, blow or pu
given OF either end. no matter how yioienl
| ~, could not reach the other extremity 10
more than 345 days, although vibration
are transmitted through iron IT the rate
about 8 lilo miles 4,9ss metsrs) In ever
second. The relative siIe Of the sun Is reE
resented on the diagram, which represent
10 cus proportions the disks Of the larsa
) planets and the srbit Of the moon, trace
, On circle representing tho face Of the sur
THE = q WEIGHT.
Tho Guns distance aud sl;s thu, beiu
known, our question has regard to i
} weight, or mass, as Il is called, when yer
large bodies are spoken Of. Here. too, "
. have abundant aud uu,ty information, Al
1 | II has proved easier 10 weigh the sun tha
10 measure his distance. Tue weight
sny terrestrial object 10 simply tho attra'
tiun subsisting between Il aud tho cart
: being measured by the force necessary
e hft Il. Now, by means Of large Masses
/ metal or other heavy material, IL has bee
found DO siblo TO exert . meAsuTurAb
erasitative attraction upon small object
snd compArison between the amount % .
traction which q body Of kaown weisl
thus exefts and that exerted by the cart
as shown BY tho weight Of the object itsel