GRAVITATION IN MASSES. 27 



large one, they would also fall in the same time; 

 for if an avalanche fall from the mountains, the 

 rocks, snow and ice, together falling towards 

 the earth, fall with the same velocity, whatever 

 be their size. 



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 sove- 

 reign 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, 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 



