898 THE BEAUTIES OF NATURE CHAP, 
ORIGIN OF THE PLANETARY SYSTEM 
The theory of the origin of the Planetary 
System known as the “ Nebular Hypothesis,” 
which was first suggested by Kant, and de- 
veloped by Herschel and Laplace, may be 
fairly said to have attained a high degree of 
probability. The space now occupied by the 
solar system is supposed to have been filled 
by a rotating spheroid of extreme tenuity 
and enormous heat, due perhaps to the col- 
lision of two originally separate bodies. The 
heat, however, having by degrees radiated 
into space, the gas cooled and contracted 
towards a centre, destined to become the Sun. 
Through the action of centrifugal force the 
gaseous matter also flattened itself at the 
two poles, taking somewhat the form of a 
disc. For a certain time the tendency to 
contract, and the centrifugal force, counter- 
balanced one another, but at length a time 
_ came when the latter prevailed and the outer 
zone detached itself from the rest of the 
sphere. One after another similar rings were 
thrown off, and then breaking up, formed the 
planets and their satellites. 
