100 
CHAPTER III. 
18. The testimony of science as to the Physical Univeise, 
and its Laws (p. 69), its beginning, and end, (as bearing, too, 
on the first hypothesis of Immortality), has now to engage us. 
Within the last generation “ there has gradually dawned 
on the minds of scientific men the conviction 
of^Mauer'and that there is something beyond Matter or stuff in 
Energy ‘ the physical Universe” (p. 70). They used indeed 
to talk of light, heat, and electricity as “imponderables,” 
but that was only an evasive term. Something that is 
not Matter “has objective, though not substantial exist- 
ence.” As to Matter, experience of the most varied kind 
shows us its real existence external to us (p. 71). We find 
it amenable to our control, except that we can neither 
conserva- increase nor diminish its quantity. This fact we 
tion of Matter, ma y ca ]i “ th e Conservation of Matter ” (p. 72). 
The same experience, however, which teaches us this Conserva- 
tion of Matter, teaches us also the Conservation of 
and of Energy. somet pi ng e i se which is not Matter, and which 
equally has objective reality (p. 73). 
This is explained by illustrations as to the “ Conservation oj 
Momentum ,” “ Conservation of Moment of Momentum, and 
Momentum, “ Conservation of Vis viva,” or “Energy.” Newton s 
Momentum third law of motion is, that action and reaction are 
and ns viva, equal and opposite (p. 74). It follows from Newton s 
first interpretation of this law, that the momentum of any system 
of bodies is not altered by their mutual action. The sum of the 
momenta generated by the mutual action of the system is zero. 
The same appears as to the Conservation of moment of momen- 
tum, when we deal with quantities of the order of the moments 
of forces about an axis. 
So again of Vis viva, or the Energy, or power of doing its 
work, which any body contains. It is independent of the direc- 
tion in which it is moving, and is proportional to the square of 
the velocity, so that a double velocity will give a fourfold energy 
^ ’ Experiments in dynamics further assure us that 
KinetLc gy and there are two forms of Energy, which change into 
potential. eac p other. These arc known as the Kinetic and 
the Potential. 
19. The Conservation of Energy being as real as the Con- 
servation of Matter (pp. 82 and 92), we have to regard it in 
