SCIENTIFIC USE OF THE IMAGINATION. 125 



the microscope and the chemist's balance to decide the 

 question. Such arguments, however, are founded on 

 a defective acquaintance with the powers and properties 

 of matter. Without committing myself in the least to 

 De la Rive's notion, to the doctrine of spontaneous 

 generation, or to the germ theory of disease, I would 

 simply draw attention to the demonstrable fact, that, 

 in the atmosphere, we have particles which defy both 

 the microscope and the balance, which do not darken 

 the air, and which exist, nevertheless, in multitudes 

 sufficient to reduce to insignificance the Israelitish 

 hyperbole regarding the sands upon the sea-shore. 



The varying judgments of men on these and other 

 questions may perhaps be, to some extent, accounted 

 for by that doctrine of Relativity which plays so impor- 

 tant a part in philosophy. This doctrine affirms that 

 the impressions made upon us by any circumstance, 

 or combination of circumstances, depend upon our 

 previous state. Two travellers upon the same height, 

 the one having ascended to it from the plain, the other 

 having descended to it from a higher elevation, will be 

 differently affected by the scene around them. To the 

 one nature is expanding, to the other it is contracting, 

 and impressions which have two such different antece- 

 dent states are sure to differ. In our scientific judg- 

 ments the law of relativity may also play an important 

 part. To two men, one educated in the school of the 

 senses, having mainly occupied himself with observa- 

 tion ; the other educated in the school of imagination 

 as well, and exercised in the conceptions of atoms and 

 molecules to which we have so frequently referred, a 

 bit of matter, say 5-5-0 -oo^ 1 ^ an ^ nc ^ ^ n diameter, will 

 present itself differently. The one descends to it from 

 his molar heights, the other climbs to it from his mole- 



