I cannot take a better illustration of this than that of gold leaf, because it brings before us the reason of this apparent difference in the time of the fall. Here is a piece of gold-leaf. Now, if I take a lump of gold and this gold-leaf, and let them fall through the air together, you see that the lump of gold--the sovereign, or coin--will fall much faster than the gold leaf. But why? They are both gold, whether sovereign or gold-leaf. Why should they not fall to the earth with the same quickness? _They would do so_, but that the air around our globe interferes very much where we have the piece of gold so extended and enlarged as to offer much obstruction on falling through it. I will, however, shew you that gold-leaf _does_ fall as fast when the resistance of the air is excluded--for if I take a piece of gold-leaf and hang it in the centre of a bottle, so that the gold, and the bottle, and the air within shall all have an equal chance of falling, then the gold-leaf will fall as fast as anything else. And if I suspend the bottle containing the gold-leaf to a string, and set it oscillating like a pendulum, I may make it vibrate as hard as I please, and the gold-leaf will not be disturbed, but will swing as steadily as a piece of iron would do; and I might even swing it round my head with any degree of force, and it would remain undisturbed. Or I can try another kind of experiment:--if I raise the gold-leaf in this way [pulling the bottle up to the ceiling of the theatre by means of a cord and pulley, and then suddenly letting it fall to within a few inches of the lecture-table], and allow it then to fall from the ceiling downwards (I will put something beneath to catch it, supposing I should be _maladroit_), you will perceive that the gold-leaf is not in the least disturbed. The resistance of the air having been avoided, the glass bottle and gold-leaf all fall exactly in the same time.