154 Meteoric Astronomy. [April, 
by chance that such and such rain drops fall upon our 
illustrative traveller. 
Hence, we have no choice but to suppose that the whole 
plane space within the circle 2,E,E,E,, aS well as an 
immense plane extent of space outside that circle, is as 
richly bespread by meteor systems as we have seen to be 
the case with the circular track E,E,E,E,—that is, much 
more richly than as pictured in Fig. 4. And here, too, we 
recognise the small importance of the extent we have given 
to the meteor cross sections in Fig. 4. Since, if the extent 
of each were smaller, we should have to cover the space 
within and without with greater numbers of these smaller 
cross sections, in order to account fairly for the fact that the 
earth’s track lies across so many of them. 
But when we remember, further, the connection which 
Schiaparelli has shown to exist between meteor systems and 
comets, we find a reason for believing that not merely 
a uniform degree of meteoric richness continues inwards 
from the earth’s orbit up to or near the very place of the 
sun, but that a great increase of richness takes place as the 
sun’s place is approached. Mr. Dunkin, in his valuable 
Appendix to Lardner’s ‘‘ Astronomy,” presents the actual 
densities with which the perihelion points of observed 
comets are distributed throughout sun-surrounding space. 
He gives the following table :— 
Distance from Sun Number of Relative Cubical Density of 
in Millions of Miles. Perihelia. Space. Perihelia. 
0 to 20 8°65 re 8°65 
20 to 40 1170 7 1°67 
40 to 60 20°50 1g 1°06 
60 to 80 TV Z10) 27 0°47 
80 to 100 20°80 61 0°34 
100 to 120 8°65 gI (obs de) 
Here it will be observed that the increase of density with 
approach towards the sun is very rapid indeed in the sun’s 
immediate neighbourhood. It is represented by the ordi- 
nates of the curve cc’ in Fig. 5, the dotted part of the 
curve being that inferred from the shape of the part which 
has been determined by observation. Moreover, it should 
be noticed that comets having their perihelia between 40 
and 100 millions of miles from the sun are, on the whole, 
more likely to be recognised than those whose perihelia lie 
nearer to the sun. 
We may fairly infer that the law indicated here for 
comets is that which holds also for meteor systems. Now 
