512 The Velocity of Light. [September, 
heat, which are propagated by the mass struck as waves, as 
vibrations. When light stops remedied or absorbed, as all 
become radiant heat, this heat turns, gradually advancing, 
into conducted heat. 
Further, supposing that planets and moons project out of 
their comparative darkness by corresponding causes, under 
the far more powerful attraction of the sun, a return current 
of particles with velocities far exceeding that of the particles 
moving against them, they maintain the lighting and heating 
process and power of that centre. 
I shall not detain the reader with the proof that the hypo- 
thesis is not admissible. 
Light and heat arise from changes of frictional and che- 
mical character in masses and molecules,* the resulting 
motions inducing, by way of gravity, corresponding motions 
not only in adjoining bodies, but also through vacuum, at a 
distance, in molecules and masses. 
The increase of heat and the following generation of light 
will always consist in an increase of molecular centrifugality 
somewhere, compensated by contraries elsewhere. All 
changes of temperature and production of light are therefore 
inter- and en-molecular motion. 
The sun overrules all light and heat processes within its 
system. It yields light to its own and other systems ; it 
induces in its planetary following a harmonic motion and 
life. It generates heat and light by alternate composition 
and decomposition of atoms and molecules embraced in a 
progressive combination, metamorphosis, and condensation 
from constitution to re-dissolution, from birth to death ; 
this process in its generality being induced by planetary 
motion round the sun, and with the sun in its orbit, not 
without reciprocity with other systems. 
When stellar, solar, or terrestrian molecules experience 
by any cause an elevation of centrifugality, wholly or in 
portions of them, we feel the propagation of such motion as 
heat, and when the increase is of a certain amount, and re- 
sults in a trajectory, we see it as light. Not only the light 
spending portion of such molecule gets more or less removed 
from its centre of force, but the whole molecule is moved 
from the centre of the portion of mass, or of the mass to 
which it belongs ; it tends instantaneously to absolute 
centrifugality, to be in the next instant repelled by a distant 
mass and by its neighbour molecules, whose centrifugality 
* My views on adhesion, cohesion, and chemistry are chiefly contained in 
“ Heat and the Atom,” “ The Origin of Organisms ” (1859), See » 
