Molecules and Atoms n 



architecture completely alters their character, 

 one being a harmless aromatic fluid, the other 

 an offensive poison. 



Atoms and molecules are far too small to be 

 seen under the highest powers of the micro- 

 scope ; nevertheless, their size and the velocity 

 of their movements are accurately known. We 

 may perhaps form some mental picture of their 

 movements, by watching the perpetual motion 

 of inorganic particles seen in a drop of turbid 

 water when placed under a good lens. Hour 

 after hour these particles may be seen to be in 

 a lively state of movement; each particle con- 

 tains millions of molecules and infinitely more 

 atoms, all of which are in constant motion 

 similar to that observed in the drop of 

 water. 



But we know that one of the fundamental 

 properties of matter is its inertia; that is, its 

 disinclination to move when at rest, and to stop 

 moving after it has once been started. What, 

 then, is the cause of the constant motion of 

 atoms and molecules ? In answer to this ques- 

 tion we reply " energy " is the cause of all these 

 and every other kind of movement ; as Professor 



