From an equal distance above the surface of the earth, bodies released, or dropped, will reach the surface at exactly the same degree of speed, and in exactly the same time--this irrespective of weight or size. In other words, a cork or piece of lead, no matter what their sizes may be, will travel with equal rapidity. In case where the "lighter" substance travels more slowly (compare a feather and bullet, for instance) the difference is caused by the light object meeting with more resistance from the air. This apparent exception has been explained away by the experiment of dropping the bullet and the feather in a vacuum tube, in which there was no resistance from air, the consequence being that both descended precisely at the same instant. Another similar experiment is to place the feather upon a piece of iron whereby the resistance of the air is prevented, and the feather will maintain its position during the drop, and will reach the ground resting on top of the iron, just as it started. And, remember this please, that the small object attracted by the earth exerts an attraction on its own account. If the two were of the same size they would exert an equal attracting power, but as one is smaller its attracting power is very slight compared with that of the large mass. But it is true that the particle of dust attracts the earth precisely as the earth attracts the particle of dust--the difference being solely a matter of degree depending upon the "mass" of the body. The amount or degree of the _combined_ attracting power is determined by the combined total of the two masses. Distance lessens the degree of attraction--thus as bodies are lifted above the earth the weight decreases very gradually, and by very slight degrees, but constantly and invariably. The poles of the earth are flattened, and, consequently, the weight of an object slightly increases as it is carried from equator to pole. Concluding our consideration of Gravitation, it will be well to call your attention to the fact that Gravitation differs from the forms of Radiant Energy known as Heat, Light, Electricity and Magnetism in several very important particulars, which seems to go far in the direction of proof that the latter are by incidents or consequences of the former.