Origin of Force
19.
Force arises from dearth or abundance; it is the child of physical motion and the grandchild of spiritual motion, and the mother and origin of gravity. Gravity is confined to the elements of water and earth, and this force is infinite, because infinite worlds could be moved by it if instruments could be made by which the force could be generated. Force, with physical motion, and gravity, with resistance, are the four accidental powers by which all mortal things live and die. Force has its origin in spiritual motion, and this motion, flowing through the limbs of sentient animals, enlarges their muscles, and thus enlarged the muscles are shrunk in length and contract the tendons with which they are connected, and this is the cause of the strength in human limbs. The quality and quantity of the strength of a man can generate a further force, which will increase in proportion to the duration of the motions produced by them.
Aspects of Force
20.
Gravity, force and casual motion together with resistance are the four external powers by which all the visible actions of man live and die.
Of Inertia
21.
A motion tends to be continuous; a body set in motion continues to move as long as the impression of the motive power lasts in it.
Can Man imitate a Bird's Flight?