92 MODERN SCIENCE READER 



is thereby so agitated as to cause it to emit light. He 

 thought the light from glowworms and putrefying matter 

 was of the same kind as the above, and said that the light 

 seen at night in the eyes of certain animals, cats for in- 

 stance, is "due to vital motions." 



Regarding true luminous flames Newton's ideas were 

 nearer those of the present time. He wrote "Is not fire a 

 body heated so hot as to emit light copiously? For what 

 else is a red-hot iron than fire? And what else is a burn- 

 ing coal than red-hot wood ? " "Is not flame a vapor, fume 

 or exhalation heated red hot, that is, so hot as to shine? 

 For bodies do not flame without emitting a copious fume, 

 and this fume burns in the flame. Metals in fusion do not 

 flame for want of a copious fume." "All fuming bodies, 

 as oil, tallow, wax, wood, etc., by fuming waste and vanish 

 into burning smoke." "Put out the flame and the smoke 

 is visible, it often smells; and the nature of the smoke 

 determines the color of the flame." "Smoke passing 

 through flame cannot but grow red hot, and red-hot smoke 

 can have no other appearance than that of flame." 



During the hundred years, more or less, following the 

 publication of Newton's views there was little change in 

 the prevailing theories. Stahl said "flame is light" liber- 

 ated from bodies in the act of combustion, and that light 

 and heat are the constant attendants of fire ; fire combined 

 with combustible matter was "phlogiston." Scheele held, 

 however, that light, heat and fire are combinations of air 

 and "phlogiston." Lavoisier thought flame to be light 

 disengaged from air, with which it had been in combina- 

 tion, and this idea seems to have been adopted by most 

 of the French chemists. 



There might be mentioned in this connection the queer 

 ideas regarding our being able to see objects, and the emis- 

 sion of light by incombustible bodies, which were held 

 during the latter half of the eighteenth century. As ex- 

 pressed by Macquer, and quoted by Fourcroy, 1 ' ' The vibra- 

 to ureroy's Chemistry, press date 1796. 



