36 9 
iSSo.] The Origin of Falling Motion. 
solids. But these two modes of motion are differently 
related to masses. Electricity is an organising eneigy. It 
only manifests itself through change in the organisation, or 
in the relations of bodies. Its only ready transformation is 
into heat. . . 
Heat is a disrupting energy. It is the individual energy 
of the separate particles, and has nothing to do with the 
organisation of molecules into masses ; yet it is a generalised 
condition of motion only as it exists in gases. In liquids 
and solids it appears to be partly specialised ; most probably 
becoming some form of rotation in liquids and of vibration 
in solids. # 
Heat force is neither concerned in the organisation of the 
mass, nor is it closely related to the particle containing it. 
It is capable of ready transfer from particle to particle, and 
of ready change in diredtion. j 
We may look upon every separate molecule or distindt 
particle of a solid body as dwelling within a nest of attrac- 
tions. The fixed organisation of the body most probably 
causes these attradtions to become definite in diredtion, so 
that it is not improbable that the motion of each particle is 
confined to a fixed centre upon which these attradtions con- 
verge, through which centre it must vibrate, or around which 
it must rotate. 
But the forces adting upon the particle are not alone the 
attradtive energies and the repulsive impadts of contiguous 
particles. The attradtive or gravitative energy of the earth 
is also a powerful fadtor in the result. This energy must 
influence the diredtion in which the particle moves. It is 
therefore one of the various adtive forces to which this 
diredtion of motion must conform. 
And gravitative energy is constant in vigour and diredtion. 
It does not vary as the forces of the surrounding particles 
may do. Thus every vibration or other movement of the 
particle has a vertical component, in response to gravitation, 
which must exercise a constant and unvarying influence 
upon the result. 
Every particle, in fadt, is incessantly falling. What we 
call a position of rest is really a position of constantly- 
arrested fall. If the surrounding attradtions tend to force 
the particle towards a fixed point in space, the attradtion of 
gravity tends to force it below this point. Thus it never 
moves to the exadt point required by its contiguous attrac- 
tions, but to a point nearer the earth, which forms a centre 
of all its attradtions, that of gravitation included. 
The distance between these two points is the distance to 
2 D 2 
