TRANSACTIONS OF THE SECTIONS. 
2 7 
tion of velocity inversely proportional to their densities and their diameters; and the 
orbits which they might describe around the sun, in such circumstances, should 
change in a corresponding degree. If an eight-inch iron ball moved in the path the 
earth now describes, there should be a greater reduction in the magnitude of its 
orbit after two years, thau the earth’s orbit could experience in one million centuries. 
Very unall meteors or shooting stars are, therefore, extremely sensitive to effects of 
» resitting medium j and they seem well calculated to serve as a test of the per¬ 
fection of the vacuum in the celestial spaces. 
This delicate tost would be unavailable were it not for the translatory motion of 
• ur system, and the great eccentricity of the orbits which meteors describe. When- 
nrr the size or density of these bodies is so email that they are much more sensitive 
in the resistance of the medium than they arc to planetary attraction, the planes of 
their orbits must be gradually brought into u coincidence with the track which the 
mu describes through space. The transverse axes of their orbits will nlso tend to 
*»'uhh' a determinate position. If their velocity be impeded by the medium while 
tW nnproaeli tire sun, the lines of apsides will advance in the direction of their 
wbital motions; but this apsidal change will be reversed by any similar impediment 
Much they may receive while retiring from the central luminary. These opposite 
nt«ti neutralize one another when the transverse axes of the meteoric orbits are per¬ 
pendicular to the line of the sun’s translatory motion. By this arrangement also 
• C u , “ Ce "f the medium in diminishing gravity on one side of transverse axes 
| "uld become just adequate to counterbalance the effects arising from its augraen- 
thl'nd' > P* Tit t ou opposite side. The orbits of the smallest meteors must, 
Mworc, have their transverse u\es, in most cases, located near a plane perpendi- 
>uhT i .j sun ' 3 * rac k- In their perihelia these bodies must necessarily move, 
. s “f K ‘ direction as the sun, or take an opposite course. In the former 
iadiff or “ lta should continually diminish in eccentricity, and finally become 
^bin S t lhe wmtro1 l ^ e Medium on their position : in the latter case, their 
, coine n ‘°te eccentric, and have their transverse axes confined to a 
'““‘led range. 
«ribcY\lT'| Ce ° f planotar y attr action ou orbits of this character is much circum- 
• |j n ’ , j can °aly change the position of their planes by turning them about 
‘Iwubl ..u- e . ® 0 ‘ ar rn°tion. If the planets all moved in the ecliptic, their action 
lil 'psia whirb 16 ► nn ® ia !-° this pl auG the transverse axes of most of the 
ul, Immp m(jteorfl describe j and this change would be permanent, not periodi- 
t vjjt jjQ- D8e 8 ' varTn8 i °f these small bodies should, therefore, be congregated into 
ecliptic aboufcm”r ® * n the direction of the sun’s motion, and intersecting the 
mav nccoi nTfv . in space to which he is advancing. In this manner 
<*n the' loth of a if * 1e or 'B! n of the meteoric zone, through which the earth passes 
•iTangement i# f USU8t ‘ I s evident that the action of the planets in causing this 
w b«ti h i„ retro ar " 10re effective when the motion of the meteors is direct than 
r ‘ 'narknble unne ® rat e ’ an d> for this and another reason previously noticed, no 
^ ipti , p auce °f shooting stars could be expected in the opposite part of 
'-Tibfr, ftceuY to ® tara which sometimes occur on the 12th and 13th of 
' one ins* iinti-lfi Cft j° * 1c c * istpn ™ of another meteoric zone perpendicular 
**^1 influence of etJ> , an, ‘ ,CJ the ecliptic; and its origin may be ascribed to the 
i n vvliicii la nets m deflecting meteors occupying this region from the 
'August, secnis hi „^* lc 7 - OUG which the earth crosses on the 8th and 10th 
IL ’ the earth nu..° n ft { n ^ ar ^ lc l ar S cr collection of these small and light bodies ; 
'hfil U1 passes thrnmvl. 4-1,.. ...... a .... i • • . • , • ’ 
— «, belii-vp tl.o *1 ‘ meteors encircling tne sun. l here is also 
Potion of t** 10 lullumeral,le host of meteors in this zone reflect a 
»u? ' l°t 1 can reeard , t ’ riIar r ay». and thus cause the phenomenon of the Zodiacal 
.Wee. l u... . *B*rd these bodies ns eternally self-luminous while wandering in 
place that the light which they emit on visiting 
»Wn 
Bote’S from the E lacH U ‘ at the >‘ght which they emit on visiting 
u °d that ^hr. t o PrCS3UIC - ,mpart to t,U! ,uci,proiJb atmosphere 
^‘^cUouca!^ atmosphere by the sun's 
