IN CHEMISTRY. 9 1 



21. Is .it probable that all the elements have been dis- 

 covered ? 



(See Key, page 49, Question i.) 



22. Is heat PRODUCED by oxidation ? 



(See Chemistry, pages 36 and 100.^ 



All forms of force electricity, heat, muscular energy, 

 chemical attraction, gravitation, etc., are now considered 

 as movements of molecules ; the particles being in con- 

 tinuous, undulatory motion, the swiftness and width of 

 the vibrations determining the character of the force. 

 These forces are interchangeable, but cannot be created 

 or annihilated, increased or diminished. 



23. What is the difference between dynamic and potential 

 force? 



A potential force is one that is latent ; a dynamic, one 

 that is sensible. The former is hidden ; the latter is in 

 full action. Potential force is a weight wound up, a loaded 

 gun, a river trembling on the brink of a precipice, a giant 

 waiting the word, an engine with the valve closed. 

 Dynamic force is the weight falling, the river tumbling, 

 the giant striking, the engine flying along the track. 



24. Why does running cause panting? 



As soon as we begin to perform any unusual exercise, 

 we commence breathing more rapidly showing that, in 

 order to do the work, we need more O to unite with the 

 food and muscles. In very violent labor, as in running, 

 we are compelled to open our mouths, and take in deep 

 inspirations of oxygen. 



25. How does O give us strength ? 



(See Chemistry, page 35.) 



