[June, 
368 
The Origin of Falling Motion , 
Whence, then, arises this motion ? It is a form of ene ^gy» 
and must be derived from some diverse form of energy which 
it replaces. If, for instance, a body begins to tall to the 
earth from a position of rest, we can safely assert that the 
motion it displays pre-existed, either in the earth, in the 
body, or in surrounding space. It was certainly not created 
for the occasion. , 
The theory of gravitation declares that the earth moves 
towards the falling body with a momentum equal to its own. 
If the body be supported above the earth, the suppoit per- 
forms a double duty. It at once hinders the body from 
falling to the earth, and the earth from falling to the body. 
They compose parts of one rigid system. But if the sup- 
port be removed the earth and the body at once become 
separate individuals, and they fall together, with equal 
momentums, until they again enter into rigid relations with 
The falling motion manifested by the descending body 
cannot, then, have been in some mysterious manner trans- 
ferred to it from the earth ; for the earth’s own motion is 
equally to be accounted for, and in that case we would have 
to look to the body for its source. No active motion could 
appear in such an equal mutual transfer of motive vigour. 
We must therefore look elsewhere for the source ot the 
motive energy displayed. 
Nor can it well have been derived from contiguous space. 
It is too instantaneous in its appearance, and too regular in 
its increase, to arise from any such transfer of moving 
en it S must therefore have had its origin in the moving bodies 
themselves. Not, however, as an ideal potential energy 
converted into a real “ aftual energy but as a real motion, 
existing previously in some other form, and converted as 
needed into the form of mass motion. 
Such motive energies exist as constituent forces of all 
matter. They present various modifications, and are named 
electrical, magnetic, chemical, cohesive, _ and temperate 
energies. These are partly modes of motion, partly modes 
of attraction : they are specialised manifestations of the 
general attractions and motions native to matter. The 
generalised form of attraction we possess in gravitative 
energy. The specialised forms are the organising attractions 
of substances, such as cohesion, chemism,^ and possibly 
magnetism. It is the same with motions. The generalised 
form is the free movement of gas particles ; the specialised 
forms are electricity, and heat as it exists in liquids and 
