SCIENTIFIC USE OF THE IMAGINATION. 153 



of its powers. Place tins distilled water in the field of an 

 electro-magnet, and bring a microscope to bear upon it. 

 Will any change be observed when the magnet is excited ? 

 Absolutely none ; and still profound and complex changes 

 have occurred. First of all, the particles of water are ren- 

 dered diamagnetically polar ; and secondly, in virtue of the 

 structure impressed upon it by the magnetic strain of its 

 molecules, the liquid twists a ray of light in a fashion per- 

 fectly determinate both as to quantity and direction. It 

 would be immensely interesting to both you and me if one 

 whom I hoped to see here present, 1 who has brought his 

 brilliant imagination to bear upon this subject, could make 

 us see as he sees the entangled molecular processes involved 

 in the rotation of the plane of polarization by magnetic 

 force. While dealing with this question, he lived in a world 

 of matter and of motion, to which the microscope has no 

 passport, and in which it can offer no aid. The cases in 

 which similar conditions hold are simply numberless. Have 

 the diamond, the amethyst, and the countless other crystals 

 formed in the laboratories of Nature and of man no struct- 

 ure ? Assured^ they have ; but what can the microscope 

 .make of it ? Nothing. It cannot be too distinctly borne 

 in mind that between the microscope limit and the true 

 molecular limit there is room for infinite permutations and 

 combinations. It is in this region that the poles of the 

 atoms are arranged, that tendency is given to their powers, 

 so that when these poles and powers have free action and 

 proper stimulus in a suitable environment, they determine 

 first the germ, and afterward the complete organism. This 

 first marshalling of the atoms on which all subsequent ac- 

 tion depends baffles a keener power than that of the micro- 

 scope. Through pure excess of complexity, and long be- 

 fore observation can have any voice in the matter, the most 

 highly-trained intellect, the most refined and disciplined 



1 Sir William Thomson 



