"[T]here cannot be loss of living force, or, which is the same thing, of motive power, if the bodies act upon each other without directly touching each other, without actual collision. ...[T]he molecules of bodies are always separated from each other by some space ...they are never actually in contact. If they touched each other, they would remain united, and consequently change form. If the molecules of bodies are never in close contact with each other, whatever... forces... separate or attract them, there can never be either production or loss of motive power... This power must be as unchangeable in quantity as matter."