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chain of phenomena of motion, necessitating a continual 
change of form. Every form as a temporary result is perish- 
able, and of limited duration ; but in this change matter 
and the motion inseparable from it remain eternal and 
indestructible.” 
The Nebular Theory, then, as understood by Professor 
Haeckel, implies that matter is infinite both in quantity and 
in its past duration ; that it has been in motion from all eternity, 
and can never rest ; that the universe has no beginning and 
no end ; that this view is required by those grand discoveries 
of modern physics, the conservation of matter and of force ; 
that the nebula, vast ages ago, was intensely hot, and has 
since gradually grown cooler, while severing into distinct 
masses, and acquiring a rotatory motion. 
All these principles are exactly reversed by the authors 
of the Unseen Universe, who are first-class mathematicians. 
They hold, as the result of the dissipation of energy, that 
the universe had a beginning, and must have an end ; that 
it is like a candle which has some time been lighted, and 
cannot burn on for ever ; that this doctrine, instead of being 
opposed to the conservation of force and matter, is the natural 
sequel and complement of those theories; and finally, that 
all the heat of the sun and stars, instead of being due to the 
high temperature of the nebula, is wholly the creation and 
result of its latter condensation. So (p. 125) we read that “ as 
the particles condensed or came together, the potential energy 
was gradually transmuted into the energy of heat and of 
visible motion.'’'’ 
In Mr. Spencer we meet with a third form of the Nebular 
Theory, and Physical Evolution. The theism of the authors 
of the Unseen Universe, who affirm a beginning and an end, 
and the monism or atheism of Professor Haeckel, Avhich 
wholly denies both, is pronounced alike unphilosophical. That 
question belongs to the class of which nothing can be known, 
For the rest, he holds the indestructibility of force, and the 
continuity or eternity of motion, as a great a priori truth. 
But he holds, side by side with it, the Dissipation of Energy, 
or a process “ which must go on bringing things ever nearer 
to complete rest.” If equilibration, he asks, must end in 
complete rest, what is the fate towards which all things tend ? 
“ If the sun is losing its force at a rate which must tell in 
millions of years, and men and society are dependent on a 
supply that is gradually coming to an end, are we not 
manifestly progressing towards omnipresent death ? That 
such a state must be the outcome of the processes everywhere 
