198 THE FITNESS OF THE ENVIRONMENT 



Uniting two carbon atoms by a single valence, 

 the formula 



H H 



I I 



H-C-C-H 



I I 



H H 



representing the compound ethane is ob- 

 tained ; but if the process be extended, great 

 complexity speedily ensues. For example, 

 the hexanes, compounds formed upon this 

 plan containing six carbon atoms, all of one 

 empirical formula, number five. Their con- 

 stitutions are represented by the accompany- 

 ing structures, every one of which corre- 

 sponds to a known substance : — 



H H H 



I I I 



H-C-H H-C-H H-C-H H-C-H 



H-C-H C-H 



I I 



H-C-H H-C-H 



I I 



H-C-H H-C-H 



I I 



H-C-H H-C-H 



I I 



H-C-H H 



I 

 H 



