Analysis continued. Excessive heat of nebula involved
condensation only at the surface. Proof that this
was Laplace's idea 108
Noteworthy that some astronomers still believe in
excessive heat 109
Interdependence of temperature and pressure in gases
and vapours. Collisions of atoms the source of heat 110
Conditions on which a nebula can be incandescent.
Sir Robert Ball 110
No proper explanation yet given of incandescent
or glowing gas 112
How matter was thrown off, or abandoned by the Jovian nebula 115
Division into rings of matter thrown off determined
during contraction 116
How direct rotary motion was determined by friction and
collisions of particles 117
Saturn's rings going through the same process.
Left to show process 118
Form gradually assumed by nebulæ. Cause of Saturn's
square-shouldered appearance 120
A lens-shaped nebula could not be formed by
surface condensation 120
Retrograde rotary motion of Neptune and Uranus, and
revolution of their satellites recognised by
Laplace as possible 121
Satellites of Mars. Rapid revolution of inner one may
be accounted for 123
Laplace's proportion of 4000 millions not reduced but
enormously increased by discoveries of this century 124