THE FORCE OF GRAVITATION 19 



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, how- 

 ever, show 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 con- 

 taining 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 re- 

 main 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 within a few inches of 

 the lecture table], and allow it then to fall from the ceiling 

 downward (I will put something beneath to catch it, sup- 

 posing 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. 



Here is another illustration: I have hung a piece of gold 

 leaf in the upper part of this long glass vessel, and I have 

 the means by a little arrangement at the top, of letting 

 the gold leaf loose. Before we let it loose we will remove 

 the air by means of an air-pump, and, while that is being 

 done, let me show you another experiment of the same 

 kind. Take a penny-piece, or a half crown, and a round 

 piece of paper a trifle smaller in diameter than the coin, 

 and try them side by side to see whether they fall at the 

 same time [dropping them]. You see they do not the 

 penny-piece goes down first. But, now place this paper 

 flat on the top of the coin, so that it shall not meet with 

 any resistance from the air, and upon then dropping them 

 you see they do both fall in the same time [exhibiting 1 the 

 effect]. I dare say, if I were to put this piece of gold 



