a 
178 Prof. D. Kirkwood on the Nebular Hypothesis. 
round the sun, an opposite direction is not, as some have suppo- 
sed, incompatible with it. Perhaps, indeed, it is not more imprub- 
able than a permanent ring, like that of Saturn, or a zone of 
small planets like the asteroids. We have supposed that on the 
breaking up of a nebulous ring its matter collected into several 
masses, the orbits of which were not greatly different, and that 
they revolved separately during an indefinite period, but ulti- 
mately united, except in the case of the asteroids, in one planet 
ary body. Those primitive masses, owing to perturbations, &., 
would meet in different directions, and it is by no means impos- 
sible that the circumstances of the collision and coalescence of 
the nebulous fragments may have been such as to overcome 
the natural tendency to rotate in the direction of the orbital 
motion. 
Again: the form of the primary ring may have influenced the 
original direction of the planet’s rotation, and hence that of its 
secondary rings and the resulting satellites. If the thickness of 
a ring was greatest in the direction at right angles to the plane 
of its motion, or if the diameter of its mass when it first assumed 
the form of a gaseous planet, was greatest in that direction, 
the plane of rotation would probably, for obvious reasons, be in- 
clined to that of the orbit; the amount of inclination depending 
upon the ratio of the diameters.* 
. The Revelations of Lord Rosse’s Telescope.—The opponents of 
the nebular hypothesis affirm that it derived its chief support 
from the supposed existence of irresolvable nebulz ; that is, of 
widely diffused vaporiform matter not yet aggregated into stars, 
but slowly undergoing the process of condensation. Such, until 
1846, was believed to be the constitution of a large proportion 
of those mysterious objects. The great nebula in Orion, for m= 
stance, was thonght to present decided indications of irresolva 
bility. Lord Rosse’s telescope, however, has shown it to consist 
at least in some portions, of minute stellar points, in extremely 
close proximity; in the language of Dr. Nichol, “every W'S? 
every wrinkle, is verily a sand-heap of stars.” This discovely 
has been considered by some as satisfactory evidence that all neb- 
ule are resolvable. “The sublime conception of Laplace, it has 
been dogmatically affirmed, can hereafter be regarded as but 4 
“splendid vision.” We reply that the principal evidence 
ted should every nebula within the reach of the telescope me nv 
y . 
conclusion that all nebulze are composed of stars. A large PIX 
portion remain still unresolved, even under the highest powe! ° 
Bivie ties hawalvo besa suggested by an anonymous writer in the Westminster 
pe 
