352 Dynamic Theory. 



difference between them relating to the temperature at which the} r can 

 be melted ; one variety melting at 18, the other at 100. The first when 

 left to itself changes slowly into the second, while the second may 

 be converted into the first by distillation. Many such examples could 

 be cited. Again it is remarkable what changes in the constitutions of 

 compound bodies accompany small variations in the atomic structure. 

 The composition of the petroleums is as follows : 



Methylic Hydride C H 4 Gas. 



Ethylic .. C 3 H 6 " 



Prophylic " C s H g " 



Butylic " C 4 H 10 Boils at 32 



Amylic " Naptha C. H 12 " 86 



Hexylic " and Kerosene, C 6 H u " 142 



Heptylic Kerosene C 7 H 16 194 



Octylic " C 8 H i8 " 247 



Nonylic C 9 H 20 303 



The common difference of the progression is C H 2 . ( Eight essences 

 named above, each C 10 H 16 . ) 

 Composition of Alcohols : 



Methylic alcohol, Woodspirit C H 4 (X 



Ethylic Common C 2 H 6 O. 



Prophylic " C 3 H g 0. 



Butylic . . . . . C 4 H 10 0. 



Amylic Fusel oil C 5 H 12 O. 



Hexylic C 6 H u O. 



Heptylic C 7 H 16 O. 



Octylic M C 8 H 18 0. 



The common difference of the progression is C H 2 . 

 A glance at the foregoing shows how nearly alike a great many very 

 different things are. Add to kerosene one atom of oxygen and we have 

 a powerful alcohol. Simply rearrange the atoms of one essence and we 

 have another. What could we have antecedently suspected there is in 

 common between the acid of rancid butter and a*cetie ether ? Yet they 

 are composed of the same atoms in the same proportions. Eliot and 

 Storer say "that the widest diversity of properties may coexist with 

 absolute identity of ultimate chemical constitution. Two allotropic 

 states of the same element not infrequently present more striking dif- 

 ference than elements recognized as distinct ; and among the numerous 

 compounds of carbon with which organic chemistry deals, there are 

 many isomeric compounds which are so entirely dissimilar as to lead al- 

 most irresistibly to the belief that it is of as much consequence how the 

 atoms of a compound are arranged as to what kind of atoms they are. " 

 It is important to observe to how great an extent the allotropic and 



