144 Pleading for a Geological Idea. [March, 
densities of the two bodies. Several observers think that 
the volume of Saturn to both sides of its rings or its equator 
differs considerably. Similar observations were long ago 
made by Schubert with regard to Jupiter. 
Displacement of Axes. 
A displacement of weights external to the planet must 
produce a reciprocal displacement of density and weight 
within the planet, and a displacement of its axes in space. 
Take a planet covered by liquid, and assume solid and liquid 
to have at starting the axis of revolution in common : any 
disturbance of the distribution of the liquid by an outside 
mass will break the continuity of this common axis, because 
the densities and compressibilities of solid and liquid differ. 
These changes must occur when a shell is divided from a 
nucleus by one or more strata of more elastic nature than 
either, and when the shell experiences from the outside or 
inside perpendicular and tangential pressures which produce 
friction, heat, chemical action, alternations of solidity, 
liquidity, and gaseity, and metamorphism through a con- 
densation of the interior below a contracting outside. A 
mass condensed at the outside in its aphelion period may 
produce moons and rings in its perihelion when the interior 
is compressed and the outside expanded. 
Condition of Rings. 
The rings are composed of solids, liquids, and gases : they 
are closed zones, separated from the central mass by vacuum. 
After separation the tendency to reunion commences. The 
rings condense by molecular changes ; they cool ; they inter- 
cept the rays of the sun, but are compressed by its centrifu- 
gal reaction and by its co-attraCtion with the planet ; they 
congeal ; the solids gain in proportion to liquids and gases. 
The central mass also cools. It gains less in velocity of 
rotation than it gains in density. It gains in velocity of 
motion round the sun ; the orbit contracts, and with the sun 
in space. Centrifugality at its surface becomes a less per- 
centage of attraction, the volume within which gravity 
exceeds centrifugality gets extended, and finally overreaches 
the contracting ring. The ring gradually descends and falls, 
starting for the planet at aphelion time ; it becomes conti- 
guous to the planet as a catastrophic rain, as a cataclysm 
with liquids, solids, and gases. It brings on a period of 
