UNEXPLAINED ORIGINS. 33 
This ring again resolved itself into a rotating globe which, 
still in a fluid state, threw off other balls, which revolved 
around their mother, the first planet, even as the latter 
continued to follow an orbit around the central body, 
the sun. In this way the planets of the solar system, 
including the earth, (according to the theory), were 
evolved together with their satellites or moons. The 
difficulty attending this view of planetary evolution is 
found in the difference between the movements of a num- 
ber of satellites around the planets. While the satellites 
of the earth, of Jupiter and of Saturn revolve from west 
to east, the moons of Uranus and Neptune have an orbital 
movement from east to west. This is regarded also by 
the friends of the Nebular Hypothesis as one of the 
gravest difficulties, since no mechanical law will explain 
the reverse movement of the satellites of the remotest 
planets when they, as well'’as Jupiter, Saturn, and the 
rest are supposed to have been cast off by the same central 
body. 
5. According to the theory, the original atoms dur- 
ing the process of world-making united into molecules. 
The laws according to which atoms unite,—so that, for 
instance, the hydrogen atom each unites with two atoms of 
oxygen, and so down the list of all known existences,— 
these laws are among the assured results of scientific 
study. Now, the entire science of chemistry in all its 
branches is built upon the axiom that molecules are 
absolutely unalterable and that molecules of the same 
kind are always absolutely identical. A molecule of wa- 
ter is always and invariably composed of two atoms of hy- 
drogen and one of oxygen. A molecule of sulphuric 
acid invariably contains two atoms of hydrogen, one of 
sulphur, and four of oxygen. A molecule of potassium 
chlorate is always composed of just one atom of potassium, 
one atom of chlorine, and three atoms of oxygen, no 
