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INTRODUCTION. 25 
Some preliminary propositions and definitions may be 
serviceable to the reader. 
Science deals with matter and force. 
Matter is that which has weight and bulk. 
Force is the cause of changes in matter—it is appre- 
¢ciable only by its effects upon matter. 
Force resides in and is inseparable from matter. 
Force manifests itself in motion. 
All matter is perpetually animated by force—is there- 
fore never at rest. What we call rest in matter is simply 
motion too fine for our perceptions. 
The different kinds of matter known to science have 
been resolved into not more than 62 elements or simple 
substances. 
Elements, or ultimate elements, are forms of matter 
which have thus far resisted all attempts at their simplifi- 
cation. 
In ordinary life we commonly encounter but 12 elements 
in their elementary state, viz. : 
Oxygen, Mercury, 
Nitrogen, Copper, 
Sulphur, Lead, 
Carbon, Tin, 
Tron, Silver, 
Zinc, Gold. 
The numberless other substances with which we are 
familiar, are mostly compounds of the above, or of 12 
other elements, viz. : 
Hydrogen, Calcium, 
Phosphorus, Magnesium, 
Chlorine, Aluminum, 
Silicon, Manganese, 
Potassium, Chromium, 
Sodium, Nickel. 
