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changes have occurred. First of all, the particles of water 

 are rendered diamagnetically polar ; and secondly, in virtue 

 of the structure imjoressed upon it by the magnetic strain of 

 its molecules, the liquid twists a ray of light in a fashion 

 perfectly determinate both as to quantity and direction. It 

 Avould be immensely interesting to both you and me if one 

 here present, Avho has brought his brilliant imagination to 

 bear ixpon this subject, could make us see as he sees the en- 

 tangled molecular j^rocesses involved in the rotation of the 

 plane of polarisation 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 otlier crystals formed in the laboratories of 

 nature and of man no structure ? Assuredly 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 afterwards the complete 

 organism. This first marshalling of the atoms on which all 

 subsequent action depends baffles a keener power than that 

 of the microscope. Through pure excess of comjilexity, and 

 long before observation can have any voice in the matter, the 

 most highly trained intellect, the most refined and disci- 

 plined imagination, retires in bcAvilderment from the con- 

 templation of the problem. We are struck dumb by an 

 astonishment Avhich no microscope can relieve, doubting not 

 only the power of our instrument, but even whether we our- 

 selves possess the intellectual elements which will ever enable 

 us to grapple with the ultimate structural energies of nature. 

 But the speculative faculty, of which imagination forms 

 so large a part, will nevertheless wander into regions where 

 the hope of certainty would seem to be entirely shut out. 

 We think that though the detailed analysis may be, and may 

 ever remain, beyond us, general notions may be attainable. 

 At all events, it is plain that beyond the present outposts of 

 microscopic inquiry lies an immense field for the exercise of 

 the imagination. It is only, however, the jDrivileged spirits 

 who know how to use their liberty without abusing it, who 

 are able to surround imagination by the firm frontiers of 

 reason, that are likely to work with any profit here. But 



