New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1850-11-20
,,7rr MooN-THE SUN;
,ste,cbed for The Tdbune.l
A LECTURE.
:. p.o,. o. NJ. MICHEL. OF clsclsNAT'.

.a;yd lecture III the COURSE az VIZ ~ I
~ &c was given on Monday eyehing- AS on
Ihs'. lesion of the previous lectures the Ohapei
ine o.' Academy was completely filed. The Pro
o. w ao,n,enced by saying that in his last lee
10 had directed the attention OF ms heaFe's
.ul ~ ,benornena of the Moon, and ne had de'
- "a n complete what he intended to say ON
hicct with that lecture, but IN answer 10
'"'' o,esfions which had since been put 10
S;r. he would give little attention to that n'ef,
", - nlsnet before opening the subject assigned
e''i aa;. Iectnre In iewing the beautiful appear
lOi ond IN investigating the motions OF that
sody the inquiring observer would naturally DC
.sn,;nea to ask whether its physical constitution
- lilo that of our earth Is 1t occupied oy
'.-.;a,t beings Has it an atmosphere IKE our
q 10 Il nossessed of rivers and oceans ana
!. ;,s surface roamcd by animals these ques
.;ony could not be answered directly Inc teles
onne has not yet brought the Moon nearer 10 ..i'
~..o 4hon o4o miles; distance too great TO as
eover with distinctness any positive proof OF ln-
hob;tants and we could not hope ever to ofih8 II
% ear as to view its inhabitants ii any there DE-
But in another way we might arrive az q Sa'iS'
factory conclusion. First, has the Moon al az
nosnbere2 By calculating the retractloh Oh n5"1
il ia ascertained that it has, but so highly fafieu
that that Of the most perfect vacuum we can pio'
anca ;s dense compared with it. Next, are Snerc
w. -. asraoa r;vers oceans or other bodies Of
weter1 Formerly it was supposed that poi'ion7
ne tho Moons disc were oceans, but the improve
rnent Of the telescope had shown the surfaces
which had before appeared plane 10 De oroheu +
into ridges and ravlnes. The dlurnal reyoluClon U,
tha Noon being the same as It's revolution round
~ Earth every portion Of it's surface endures
AZ nnromittipg heat of the Suns rays for fourteen
Jays in succession and must become so heated
that any water would be evaporated: Neither Is
there evidence OF the existence OF hre or INC
elements of its support, an atmosphere containing
oxygen being wanting The appearances former
u, s69nnosed 10 be volcanoes, are now shown to be
the reflection Of the Earth's light. Three OF tae
essentials of man existence, air, water and lre
being wanting it could not be supposed that sen
tient beings were to be found there. stu no GER
tainty could be had on the question, for who would
dispute the power of Him who had constituted
sphere so different from our own to adapt beings
for its habltatons
The sneaker then took up his subject for the
evening-the Sun-and glanced rapidly at The
probable train Of discovery by which It's apparen
motions had become definitely known THIS wa
more difficult than i'll the case oil the Moon, sine
the Sun at once obscured all those landmarks D.
which the Moons course was traced buC ny ou
securing the cluster OF stars which appeared neates
behind him after his setting 1t was lound thaC
was night after night fastening toward hni
and that in q period of SIX months an entlret
different portion of the heavens occupied Tn
zenith at given hour of the night. BY process
similar to that detailed in the last lecture n
track and time is calculated, and 1t IS now loui
that his course is not parallel WIN thaV Oh "a
&c fl,ay onr
the North and then recedes seuth"ardly a3ah
The fact of this obliquity OF the Suns path
the Equator being established, how Shall II
amount be determined? In perfectly simple mar
ner 1t had been done by the children OF the let
turer when they were but ten years old, D
marking the extreme of the shadow thrown on
level surface by his house top when the Sun wa
on the meredian. Each day the shadow wa
more extended till it reached limit when 1t be
gan to crawl back again and shortened daily til
Il reached a limit in the other direction lint
from each of these limits to the point whence tn,
shadow fell formed angle, one-half OF whlci
was the angle of obliquity sought From the an
cient records of this inclination is found that th
angle is changingand that the two circles are rock
ing to and fro, occupying tens OF thousands OF year,
in each vibration.
The discovery Of epler's laws wrought com
plete revolution in astronomical research. The
planets, which had been considered as isolated
bodies, were then brought into netamily, and were
10 be investigated together. The periodic time OF
all the planets was easily calculated, but how
should they learn the distance? Kepers law
taught them that the squares of their periodic
time were in proportion to the cube OF their mean
distance The distance Of the Earth from the
Sun being known that of the other planets could
be easily calculated. This involved the problem
of the paralaG, or the apparent change OF posltol
ofan object viewed, caused by real change III The
place of the observer The lecturer most clearl.
explained the method of determining this engl
from simultaneous observations from distant part
of the Earth's surface and also by observation
mon the transit of Menus across the Suns disc
$4,000 900 of miles is found to be the mean dl;
tance of the earth from the Sun.
But the discovery by Newton that all matte
Influences all other matter by its attractive pc &c
rendered it necessary to learn with precision tn
amount of matter in the Sun and Moon. The
must all be weighed in the same scales. For tn
purpose the Earth was taken Tor unit OF wei5h
The number of feet which falling body passe
through in a second is the measure OF the attrac
ing force This, by Newton's law, decreases a
the square of the distance increases. The amour
of detection Of the earth from tangental, stra
line in a second is the distance it falls toward tn
Sun in second. This is two and a half time
greater than that of the Moon toward the Eartt
But the Earth is four hundred times further ror
the Sun than the Moon is from the Earth, so tina
the Suns influence is one hundred and sixty thou
sand times less in proportion to amount OF matter
This would make the Sun about four hundre
thousand or in exact figures, 54,s $50 times heavie
than our globe. The circumference of the Sun
so great that the whole orbit of the Moon Nigh
be included within it aud still leave room for AT
other Moon, at double the distance, within it
limits
The specific gravity of the Sun is about one
fourth that of the Earth.
In considering the question of the physical cor
stitution of the Sun, the lecturer examined tn
theories which have been advanced, especial
that of Heyschell. who supposed ito be an opaQu
body surrounded by luminous atmosphere, an
gave some reasons which led him to ditter trol
that astronomer. He alluded to the fact OF a We
defined true edge always being seen to its dis
the periodic return aud changing nature of tn
spots, some of them 10000 miles across, to tn
permanency of the notified appearance OF its su
face. and other phenomena which furnish all th