ATOMS AND MOLECULES 49 



heated, its progress is still more rapid and more 

 interrupted. Some of the lighter gases of the air 

 fly with such velocity that they succeed in escaping 

 from the atmosphere altogether. And the mole- 

 cules of gases not only constantly fly about, they 

 are also in a state of constant vibration ; and it has 

 been calculated that a molecule of hydrogen 

 vibrates four hundred and fifty million million 

 times a second, representing a distance in to-and-fro 

 movement of about one mile. 



We have instanced the molecules of air, which 

 is of course a gas, but the molecules of liquids 

 and solids are equally restless. The paper on 

 which I write is really seething like a sea. Carl 

 Synder says that " a drop of water would resemble 

 a thick swarm of bees pounding against each other 

 in their flight with tremendous force. Even the 

 crystalline diamond would seem like pyramids of 

 billiard-balls, hung wide apart by invisible springs, 

 and gyrating intensely." " We ought," says Le 

 Bon, " to picture to ourselves any body whatever, 

 such as a block of steel or a rigid fragment of rock, 

 as being composed of isolated elements in motion, 

 but never in contact." 



Cliffbrd gives a very picturesque and vivid 

 account of the varied behaviour of molecules in 

 gases, liquids, and solids. In the case of gases, he 

 says the molecules " do not fly far in one direction, 



4 



