ASTRONOMY: C. D. PERRINE 
375 
is closely a sine curve with the maximum at 195° and the minimum 
at 15°. There are indications of variations of a shorter period superposed 
on this curve which can be explained by more or less harmonic gaps at 
certain longitudes. 
4. The apheha of the 45 short-period comets show a preference for 
essentially the same longitude as do the minor planets, viz., 195°, the 
minimum occurring also at 15°. Considerable irregularities exist in 
this curve, due largely to the small amount of data. Some of the 
irregularities, however, appear to exist in the curves of parabolic comets 
also. The general form of the curve is none the less well marked. 
5. The aphelia of the parabolic (and very long-period) comets show 
a preference for a region near the intersection of the ecliptic with the 
galaxy which is nearest to the longitude of the antapex of solar motion 
(90°). A more widely scattered and less pronounced preference is 
shown for the region of the longitude of the apex of solar motion 
(270°). There appears to be a tendency to avoid the intermediate 
galactic regions, between these two regions of preference and also the 
galactic polar regions. 
6. Although the aphelia of the parabolic comets are widely dis- 
tributed over the sphere, there is a small preference for the ecliptic 
plane. The deficiency of aphelia is most marked in the region of the 
northern pole of the ecKptic {a = 18^, 5 = -f 67°). 
7. There is a deficiency of small incHnations (to the ecliptic) among 
the paraboHc comets which is nearly normalized if the short-period 
comets are included. This indicates that these short-period comets 
have been captured out of the general herd and that their inclinations 
have not been radically changed since capture. 
The distribution of the aphelia of the parabolic comets is what might 
be expected if they have been captured from bodies which are more 
plentiful in the galactic regions than elsewhere. 
On the theory of probabiHty only a very small proportion out of a 
mass moving with all directions and speeds would come close enough 
to be observable from the earth, except such as were moving with 
nearly the same speed as the Sun when they came within the distance 
of effective gravitational action. All of such, except those changed 
into small elHpses by planetary perturbation, will have sensibly para- 
bolic motion. Preponderance of aphelia in the southern ecliptic hemi- 
sphere as well as the southerly ecliptic deviation of the maxima near 
the longitudes of the solar apex and antapex, indicate some sort of 
preferential motion of these bodies with respect to the Sun before 
