672 KANSAS CITY REVIEW OF SCIENCE. 



Then follow definitions and divisions of these topics. 



1. Matter. — Matter is that which occupies space and prevents anything else 

 from occupying the same space at the same time. There are large bodies of mat- 

 ter, as the sun, moon, mountains, etc. These are known as Masses. Of course, 

 these masses can be divided and subdivided to an apparently unlimited extent. 

 Thus, by heat, water is changed into an invisible vapor; and, by electricity, it is 

 changed into invisible gases. But there is a difference between the invisible forms 

 obtained in the two cases. If the heat be taken away, the vapor produced by it 

 will cool down and again resume its original form ; but the gases produced by 

 electricity are permanent — they do not again become water when the electricity is 

 removed. We conclude, then, that the state of division reached by the heat was 

 the finest possible without altering the identity of the water. Such divisions are 

 called Molecules, from the Latin word moleculis, meaning a little mass. But the 

 state of division reached by electricity, by which the identity of the water was 

 altered, must have been finer than the molecules. And, since these particles finer 

 than the molecules cannot be subdivided any farther by the forces at man's 

 command, they are called Atoms, from a Greek word meaning uncut-able, or in- 

 divisible. 



Then we sum up, in reference to Matter, that we know it in three different 

 forms : 



a. Masses. 



b. Molecules. 



c. Atoms. 



II. Changes. — As we just now said, in changes identity may be affected or 

 it may not be. So we may classify changes under two heads : 



a. Chemical, or such as result in loss of identity. 



b. Physical, or such as do not result in loss of identity, but only affect posi- 

 tion, state of rest or motion, condition, as gaseous, liquid or solid, etc. 



III. Causes of Changes. — Whatever causes change of any kind is called 

 Force. We do not know anything about absolute Force ; but that is the name we 

 give to whatever causes change. Now Force receives many names, according as 

 it exhibits itself in one way or another ; and, without stopping to discuss these 

 "forces," as we call these various exhibitions of Force, we arrange the following 

 classification of them : 



i. Attraction, which, since it is seen acting between Atoms, and between 

 Molecules, and between Masses, may be divided into three heads : 



a. Atomic, usually called Chemical Affinity. 



b. Molecular, subdivided into Cohesion, Adhesion, and the Crystallic Force. 



c. Cosmical, usually called Gravitation. 



2. Phenomenal, or such as affect our senses, as Heat, Light, etc. 



3. Biologic, or Vital, or Life Force. 



Many of these forces can be changed from one kind into another and not one 

 jot of energy be lost; and it is possible, even probable, that most if not all of 

 them are only modes of motion — modes of that motion originally imparted to 



