Perpetual Motion is that which possesses within itself the principle of motion; and, consequently, since every body in nature, when in motion, would continue in that state, every motion once begun would be perpetual but for the operation of some external causes; such as those of friction, resistance, etc.; and since it is also a known principle in mechanics, that no absolute power can be gained by any combination of machinery, except there being, at the same time, an equal gain in an opposite direction; but that, on the contrary, there must necessarily be some lost from the above causes, it follows that a perpetual motion can never take place from any purely mechanical combination; yet this is a problem which has engaged the attention of many ingenious men, from the earliest period to the present time, though it has but seldom been attempted by men of science since the true laws of mechanics have been so well established.