é 
144 Metcoric Astronomy. (April, 
Thus, let EE’ be taken to represent the earth’s velocity in 
magnitude and direction, and let mm’ represent in magni- 
tude the real velocity of any meteors which seem to 
come in the direction s’ E; then we have only to describe 
the circular arc, KLM, around BE’, with mm’ as a radius, 
to obtain E’M the real direction of the meteor’s motion. 
(Compare the note illustrated by Fig. 1). But this very 
construction shows us that so long as the real meteoric 
velocity, mm’, is unknown, we cannot tell the real direction, 
s'E, of the meteor’s motion. The apparent velocity, ME, 
would indeed give us what we want (the point M in fact); 
but a meteor appears too suddenly and vanishes too quickly 
for exact reliance on any estimates of the velocity with 
which they traverse our atmosphere.* 
Meteoric astronomy had reached this stage when Schia- 
parelli, who had already directed much attention to the 
subject, and had speculated somewhat boldly upon it, was 
led to compare the motion of the great comet of 1862 
(No. III.) with that of the August meteors. Observing 
that this comet passed close to the earth’s orbit on a course 
somewhat resembling that of the August meteors (on the 
assumption that they are moving with a velocity exceeding 
the earth’s), he inquired whether the agreement would be 
found yet closer if the actual velocity of the comet where it 
passes close to the earth’s orbit were assumed to be that 
with which the meteors are travelling when they enter 
the earth’s atmosphere. 
As this was the sole assumption made by Schiaparelli, it 
will be well to consider how far it affects the probability 
of inferences based on the coincidence actually recognised 
when this assumption has been made. 
The real velocity of the August meteors. cannot possibly 
exceed twenty-seven miles per second; since any greater, 
where they cross the earth’s track, would give them a 
hyperbolic orbit, whereas it has been shown that they form 
a closed ring. Again, the real velocity cannot greatly fall 
short of the earth’s, since otherwise the meteors of the 
system would appear to come from a point lying much 
nearer to that part of the heavens towards which the earth 
is travelling on August 11th than is actually the case. 
Thus, let EE’ be a part of the earth’s course on August 
* In any exact investigation of meteoric motions the influence of our earth’s 
attraction, as well as the effects of the earth’s rotation,—the former producing 
a real, the latter an apparent, change in the paths of meteors—must be taken 
into account. These circumstances do not, however, affect the general reasoning 
given above, and their effets are unimportant compared with those due to the 
circumsolar motions of the meteors and of the earth. 
