124 FKAGMENTS OF SCIENCE. 



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 6o ^ 00 th of an inch in diameter, will 

 present itself differently. The one descends to it from 

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

 cular lowlands. To the one it appears small, to the 

 other large. So, also, as regards the appreciation of 

 the most minute forms of life revealed by the micro- 

 scope. To one of the men these naturally appear con- 

 terminous with the ultimate particles .of matter; there 

 is but a step from the atom to the organism. The 

 other discerns numberless organic gradations between 

 both. Compared with his atoms, the smallest vibrios 

 and bacteria of the microscopic field are as behemoth 

 aid leviathan. The law of relativity may to some ex- 

 tent explain the different attitudes of two such persons 

 with regard to the question of spontaneous generation. 

 An amount of evidence which satisfies the one entirely 

 fails to satisfy the other ; and while to the one the last 

 bold defence and startling expansion of the doctrine by 

 Dr. Bastian will appear perfectly conclusive, to the 



