WHAT IS PHYSICAL LIFE 



the imagination also, because it is too weak 

 a faculty now, since it can make its pic- 

 tures only out of materials which the 

 bodily senses furnish. A surer and more 

 powerful agency than either the senses or 

 the imagination is henceforth to carry 

 him on, namely, his Understanding, that 

 oldest and best name for the human Rea- 

 son. The scientist walks by reason and 

 not by sight. If he be a chemist he busies 

 himself only with molecules, atoms, and 

 ions, each one of these things being much 

 larger than the other. I heard a pro- 

 fessor of organic chemistry enthusiasti- 

 cally remark that he had met with such a 

 huge molecule among the sugars, that if 

 only he could multiply it twenty-five times 

 he could then see it with a microscope! 

 But no one has yet seen, or detected by any 

 bodily sense whatever, a single molecule, 

 still less an atom, and far less an ion which 

 is a hundred thousand times smaller than 

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