170 H, A. Newton— Origin of Comets. 
challenge? On the other hand, if the comets, or any of them, 
originate within the solar system, and not at a great distance 
from the sun, their orbits would be short ellipses, and their 
motions might be expected: to be somewhat like those of the 
lanets. The fact that most of the periodic comets move in 
orbits of small inclinations to the ecliptic, it must be admitted, 
is, till otherwise explained, a very strong —— that they, 
at least, always formed part of the solar n 
19. The original distributions of the abhelia and of the inclin- 
ations were stated above. But the comet becomes subject to 
perturbations, and, if it was, or, if it becomes a permanent 
member of the system then the perturbations may accumulate 
so as to destroy or conceal the original la t is not easy to 
give useful expressions for the mesic: Bartubbadions for an 
orbit of large excentricity and inclination. But the general 
tendency of the forces would seem to resemble somewhat that 
of their action upon the moon are: the planets. Here the line 
of apsides has a progressive secular motion, while the inclina- 
tion remains quite constant. The effect of a resisting medium, 
if one exists, would be to shorten the periodic time and to leave 
the plane of the orbit er The effect upon the line of 
apsides sae? not be larg 
20. The present diaribation of the aphelia is not critical 
between the two hypotheses. FoR rogression of the line of 
latitude for known orbits is very nearly as the cosine of the 
latitude. The principal exception is a slight excess of num- 
bers in the small latitudes. One conclusion may be safely 
inferred from this thorough distribution over the heavens; 
that is, that if Kant’s hypothesis be true, the period of past 
= since the comets were aggregated and made to descri 
these long orbits has been a very great one, and the process of 
disintegration of comets is a very slow one. ee rooms r 
as abey have pea favor the foreign origin of co 
21. The general effect of small pertu Feattgtions “of a planet 
upon the ota of comets would be to increase the inclination 
of some and diminish that of others. 
If a comet 2s Jupiter on one side the inclination may be 
increased. This, however, is balanced by the diminution of 
the inclination of another comet moving in a parallel path on 
the opposite side of the planet, or, if you please, by one com- 
ing on the same side of Jupiter but from the opposite direc- 
tion. The total effect would at on sight seem to be neither 
to increase nor diminish the average inclinatio 
22. The present actual distribution of the "Fuclinations is 
