VII. MATTER AND FORCE 



SOME PROPERTIES OF MATTER, AND CHANGES IN MATTER 

 DUE TO FORCE 



To spend time watching the flames of a bonfire, or the dis- 

 appearance of burning material in a stove or furnace, is a 

 common experience. Wherever matter disappears in flame 

 before our eyes, the thoughtful mind wonders at the evidence 

 of some mysterious agency actively at work. There is 

 something fascinating in watching even the burning of a 

 match stick, something awe-inspiring in witnessing a great 

 conflagration when a city is fire-swept. It is little wonder 

 that the ancients regarded fire as one of the natural elements, 

 and we sometimes speak now of destruction by fire and flood 

 as work of "the elements." 



Only an elementary knowledge of Chemistry is needed to 

 understand that the burning of substances, as we commonly 

 witness it, is but the process of their oxidation, or union with 

 oxygen. The products of this combustion are largely gases 

 and vapors which ordinarily pass off into the air unobserved. 

 To explain the changes that occur before our eyes, we rest 

 satisfied with the statement that they result from the action 

 of chemical force, but what this " force" is we do not under- 

 take to say. The most that can be taught of it has to do 

 with the conditions under which it manifests itself, and the 

 products of its action. With these the study of Chemistry 

 is largely concerned. 



Living matter has the distinguishing characteristics of 



