366 The American Geologist. December, i9rM. 
nebula, the orbital excentricity oi the latter would have been 
the same and the Earth would have been just as much in its 
way, and it could not in any way have escaped to become the_ 
Earth's satellite, provided it crossed or reached up to its orbit. 
If the reader has paid careful attention to our arg-umenta- 
tion against the nebular theory, he will the more easily under- 
stand, that this is absolutely the only way in whjch the Moon 
can have come to the Earth. If we consider ]\Iars and his 
moons, it is equally clear, that wherever these exceedingly 
small planets had their orbits between ]\Iars and the Earth 
and so far outside of the latter that they did not reach its 
orbit at their perihelia, they would, on account of the great 
excentricity of their orbits, cross or reach the orbit of ^lars at 
their aphelia, and thus not escape being captured in the same 
manner that the Moon was captured by the Earth. 
We may, then, safely conclude that what is true about the 
satellite of the Earth and of Mars is true also of the satellites 
c>f other planets to the uttermost limit of the solar system. If 
a large nebula would arise between Mars and Jupiter, where 
a large number of small planets with great excentricity have 
their orbits, it is clear that it, with its more circular orbit, 
would get a great number of moons. 
It may be urged in opposition at this point, that there are 
no small planets beyond Jupiter; but since such an objection, 
if it were made, could not be based upon anything else than 
that we have, so far, not discovered any small planets beyond 
Jupiter, it would be of no avail. In reply, it would be sufi- 
cient to call attention to the fact, that before Piazzi discovered 
Ceres on January first, 1801, there was not a single small 
planet known in that region, where since that time about 500 
have been discovered. In view of this, we understand, that 
before the discovery of Ceres, a statement might have been 
made with as great, or still greater force, that there were no 
small planets beyond Jupiter or Saturn or farther out. Such 
an objection is, therefore, not worthy of serious attention. \\'e 
must, furthermore, be on our guard, both here and elsewhere, 
against limiting the scope of scientific development by barriers 
based only on ignorance and preconceived opinions. 
As the number of discovered minor planets has increased 
from time to time, these have also been discovered farther and 
