GROUPS OF AGGREGATES. 109 



to do anything of this sort. Taken together, the abstract- 

 concrete sciences give an account of the various kinds of 

 properties which aggregates display ; and each abstract- 

 concrete science concerns itself with a certain order of these 

 properties. By this, the properties common to all aggregates 

 are studied and formulated; by that, the properties of ag 

 gregates having special forms, special states of aggregation, 

 etc. ; and by others, the properties of particular components 

 of aggregates when dissociated from other components. But 

 by all these sciences the aggregate, considered as an indi 

 vidual object, is tacitly ignored; and a property, or a con 

 nected set of properties, exclusively occupies attention. It 

 matters not to Mechanics whether the moving mass it con 

 siders is a planet or a molecule, a dead stick thrown into 

 the river or the living dog that leaps after it : in any 

 case the curve described by the moving mass conforms 

 to the same laws. Similarly when the physicist takes for 

 his subject the relation between the changing bulk of matter 

 and the changing quantity of molecular motion it contains. 

 Dealing with the subject generally, he leaves out of con 

 sideration the kind of matter; and dealing with the subject 

 specially in relation to this or that kind of matter, he 

 ignores the attributes of size and form : save in the still 

 more special cases where the effect on form is considered, 

 and even then size is ignored. So, too, is it with the 

 chemist. A substance he is investigating, never thought of 

 by him as distinguished in extension or amount, is not even 

 required to be perceptible. A portion of carbon on which 

 he is experimenting, may or may not have been visible under 

 its forms of diamond or graphite or charcoal this is in 

 different. He traces it through various disguises and various 

 combinations now as united with oxygen to form an in 

 visible gas; now as hidden with other elements in such 

 more complex compounds as ether, and sugar, and oil. By 

 sulphuric acid or other agent he precipitates it from these 



