64. The Birth and Evolution [February, 
individual sun with an atmospheric limitation and the inter- 
action of the various bodies of the whole solar system. 
The exaggerating way of putting the theory Dr. Spottis- 
woode may find in “ On some Properties of the Earth ” 
(1880) : — “ We cannot consider the heat emitted, whatso- 
ever may be the manner and kind of its development and 
nature, as merely the product of the sun, and as being an 
arbitrary quantity independent of the solar system ; we 
might rather compare the sun to a furnace, consuming the 
smoke and gases its heat sets free, to feed its own fire and 
luminary, and to assist in the process of reduction — a meta- 
phor which I do not intend to introduce here as a hypo- 
thesis.” 
The “ aCtive mind ’’which enters into the spirit of my 
“ development theory ” may learn that there is a difference 
between a system forming and formed, and that the process 
of maintenance of what we may call the seasonal energy of 
either planet or sun is to be distinguished from the more 
permanent life process of the system. 
Translation. 
Although in the important distribution of planets general 
qualities of absolute magnitude, density, depression, velocity 
of rotation, and absence of moons show themselves as de- 
pendent from their solar distances, half the great axes of 
their orbits, yet this dependency in each of these groups is 
not to be maintained. We know for the present, as I had 
occasion to remark, of no inward necessity, of no mechanical 
law of Nature, which, like the beautiful law that connects 
the squares of the times of revolution and the cubes of the 
great axes, might represent the elements named in each 
group of planetary bodies as dependent from their solar 
distances. 
If Mercury, the planet nearest the sun, is the most dense, 
six or eight times so as some of the farther ones, Jupiter, 
Saturn, Uranus, Neptune, the series proves very irregular in 
Venus, Earth, Mars, or in Jupiter, Saturn, and Uranus. 
The absolute magnitude increases, as Kepler already pointed 
out, with the distances in general, not in particular. Mars 
is smaller than the Earth, Uranus smaller than Saturn, 
Saturn smaller than Jupiter, and they are succeeded by a 
host of planets too small for exaCt measurement. The velo- 
city of rotation generally increases with distance, but it is 
with Mars slower again than with the Earth, with Saturn 
slower than with Jupiter, 
