Sketch of an Organismal Thconj of Conscious luss 329 



one has literally as much of uniqueness about it as has an 

 elementary chemical substance. 



In order to bring out the trutli of this statement we must 

 exhibit, in the regular natural history manner, the resem- 

 blances and differences between cliemical elements on tlie one 

 hand and the resemblances and differences between human 

 beings on the other, and tlien pool the results of these com- 

 parisons. 



To the carrying out of this enterprise the so-called peri- 

 odic law in chemistry is of very great importance. The 

 essence of this law, stated from the natural history stand- 

 point, is that the chemical elements range themselves into 

 natural species and genera after much the fashion that plants 

 and animals do ; and that the classification is based mostly on 

 the chemical attributes of the substances, but partly on their 

 physical attributes also. Thus the "halogen group," that to 

 which lithium, sodium, and potassium belong, is a genus in 

 the sense of descriptive natural history, its species being the 

 substances mentioned with others not enumerated. Also the 

 group often spoken of in chemical laboratories as "the iron 

 group" — the genus containing the species iron, cobalt, nickel, 

 platinum, etc., illustrates the point. Two species of the last 

 genus, iron and nickel, will be used in our stud3\ Let us 

 compare some household utensil made of iron with a similar 

 one made of nickel. For the ordinary uses to which these 

 implements would be put the difference between the sub- 

 stances of which they are made would hardly Ix^ noticed. 

 The higher specific gravity of nickel (8.5 plus) is so sHght 

 as compared with that of iron (7.8) that the greater welglit 

 of the nickel im])lement would ])rol)ably not 1h^ noticed. Nor 

 would the slightly lower melting j)oint of nickel nor its much 

 lower magnetic capacity be recognized. The most avad- 

 able distinguishing difference is in color, the ordinary house- 

 keeper answering you, if you ask how she knows a nickel 

 from an iron implement, that the nickel piece is silvery bright 



