176 Prof. D. Kirkwood on the Nebular Hypothesis. 
the former, is ¢hird also in the latter. Mars, it is true, has a 
gre sphere of attraction than the earth; it may be remarked, 
owever, that owing to the small size of the planet, and its 
proximity to Jupiter, a satellite would not be stable unless very 
near the primary. a, 
13. Recapitulation—Simplicity of the Nebular Hypothesis.— 
When the number and variety of the phenomena explained by 
the nebular hypothesis are duly considered, the weight of evi: 
dence in its favor must be admitted, we think, by every unbiass: 
ed mind. The rotation of the sun; the unity of direction of the 
planetary motions; the approximate coincidence of the planes 12 
which the planets move, with the plane of the solar equator, the 
general agreement between the direction of the axial and orbital 
revolutions; the small eccentricities of the planetary orbils; 
the rings of Saturn; the central heat of the earth; the oblate 
form and primitive fluidity of the planets; the origin of comets ; 
telescopic revelations in regard to the physical constitution of 
the sun, moon, and some of the planets; the phenomena of 
variable stars; the equality between the periods of rotation and 
orbital revolution of the satellites; the extraordinary phenomena 
presented by the first three satellites of Jupiter ; the zone © as: 
teroids between Mars and Jupiter; the zodiacal light; the anal- 
ogy between the periods of rotation of the primary planets ; the 
distribution of the satellites ;—all, as we have seen, are account: 
ed for by the nebular cosmogony, while for many of them r 
least, no other explanation has ever been offered. ‘Adopting this 
hypothesis, all the motions of the solar system are derived from 
a single impulse communicated by the Creator to the primiuve 
nebula: rejecting it, each motion of every member de ands the 
separate operation of his power. Now, “if there be two mga 
of explaining any phenomenon of nature, then, ceteris part's 
that.is the most probable which is the most simple. 
what we observe in the creation around, we are forced 
conviction that the Almighty acts in this respect with that ee 
my of creative energy, which, although infinitely more perfec 
in its degree, has nevertheless its visible type in that husbandry 
of our resources, that disposition to economy in our efforts, whi 
impels us always to avail ourselves of the simplest possible means 
of effecting all that we wish to do. 
upon the 
