1872.] Meteoric Astronomy. 143 
It does not follow, however, be it noted, that any one of 
these systems centrally crosses the earth’s path, whether we 
regard that path as the elliptic line traversed by the earth’s 
centre or as the elliptic ring traversed by the earth’s globe. 
On the contrary, the chances are that the earth does not 
pass quite or even nearly through the cove of any meteor 
system belonging to the solar domain. 
Now when Schiaparelli commenced his inquiries, abso- 
lutely nothing was known about the extent of any one 
of the meteor systems traversed by the earth. To take the 
August and the November systems, it was known that one 
part of each lies near the earth’s orbit. It was known also 
that the August system crosses the earth’s track at a 
considerable angle, since even though the earth’s motion 
brings the radiant point down (as it were) nearer to the 
point towards which the earth is making on August 1oth (a 
point close by the star é Arietis), the radiant is still some 
37° from the ecliptic. It was known further that the 
November system travels much nearer to the plane of 
the ecliptic, and in a retrogratle course (that is, meeting 
the earth), because the radiant lies within Io of the 
ecliptic, and almost in the latitude of the point towards 
which the earth is travelling on November 13th (a 
point close by ¥ Leonis). But nothing whatever was known 
as to the orbit range of either system—the major axis of the 
mean path of these meteoric families. For anything that 
had been shown to the contrary (setting aside as too 
unsatisfactory to be trusted the estimates of the velocities 
of the meteors while traversing our atmosphere), the part of 
the systems traversed by the earth might be the portion 
farthest from the sun, and the perihelion portion might 
be quite close to his orb; or the part traversed might be the 
perihelion portion, and the aphelion portion might have 
any distance whatever,—from a range little exceeding the 
earth’s mean distance to one exceeding many times even 
the distance of Uranus or Neptune. ‘This ignorance as to 
the meteoric orbit-ranges was necessarily accompanied 
by ignorance as to the real velocity with which they cross 
the earth’s track, and this in its turn involved ignorance as 
to the true inclination of either system. Given the major 
axis of either meteor orbit, the real velocity of the meteors 
at the earth’s distance would be known; and since the 
earth’s motion is known in velocity and direction, the 
apparent direction of the meteor’s motion being also 
known, the real direction of the meteoric motions follows 
at once. That this is so can readily be demonstrated. 
