ni REFORMED CONCEPT OF MATTER 45 



residual force to work externally; the atoms (in inert ele- 

 ments) and molecules (in others) therefore move freely 

 and unhampered. If the inner balance of charges is not 

 quite complete, there will be some external residual force as 

 between the molecules, and the liquid state will result. If 

 this inner satisfaction is lessened still further, the resultant 

 external strain among the molecules will increase, they will 

 attract each other still more strongly and tend to closer 

 aggregation, and thus the solid form will appear. The 

 negative or positive electrical condition of the gas, liquid or 

 solid will be an index of the still unsatisfied charges residing 

 in the substance in that state. The free and unhampered 

 movement of atoms in an inert gaseous element and of 

 molecules in other gases makes the question of the particular 

 forms of such elements or gases immaterial; they have as 

 gases no particular form. In the case of liquids, however, 

 the resultant residual forces of the atoms and molecules will, 

 as is the case in electrical bodies, act mostly at the surface, 

 where the resulting force between the molecules of the sur- 

 face layer, or the surface tension, as it is called, will give a 

 particular form or shape to the liquid (as in a drop of water). 

 The molecules inside a liquid appear to be stratified into 

 layers loosely superimposed on each other. And in the case 

 of solids the still larger residual force will result in arranging 

 the molecules in a definite crystal structure on the pattern 

 of a lattice, which is the special and specific form of solid 

 chemical substances. Crystal structure is to solid com- 

 pounds what the planetary structure is to the atom — not only 

 a specific ordering of inner units, but the index and source 

 of all external properties and activities. One of the most 

 interesting recent discoveries is that in crystals there is a unit 

 body or minute structure consisting of two or more molecules 

 which is of atomic or radicle character in that it always acts 

 as a unit in the upbuilding of the crystal. 



Besides the gaseous, liquid, and solid phases of matter just 

 discussed there is a fourth, to which in recent years an ever- 

 increasing amount of attention has been and is being devoted. 

 This is the colloid state, in which one substance is dispersed 



