LIGHT AND VISION 95 



References : 



1. 1002:399-403. The Production of Light the Electron. 



2. 1304 : 234. Heat and Light. 



3. 1601 : 12-13. Heat Produces Light. 



4. 1710 : 46-47. Heat Produces Light. 



5. 1803 : 463-464. Radiation and Absorption. 



a, 1804 : 317. Molecular Motion Produces Light. 



6. 1805 : 215. Heat a Source of Light. 



c. 1807 : 257-258. Heat Produces Light. 



d. 1809 : 274. Heat Produces Light. 



e. 1811 : 220-222. Natural and Artificial Sources of Light. 



Experiment 33. Heat Produces Light. 



Review the heating and lighting effect of the electric cur- 

 rent. Regulate the amount of current which passes through 

 an incandescent lamp by means of a long piece of German 

 silver wire of small diameter. The same plan may be used in 

 connection with a small piece of iron wire and the dry cells. 



69. LIGHT AND VISION 



While existence requires heat and food and air, vision, as we 

 understand it, could not exist without light, and life would be 

 very empty. We must consider that light is due to electric 

 waves sent out by a body, which, by virtue of temperature, 

 or chemical change, can produce these wave motions. When 

 these waves strike the eye, we receive the sensation of light, 

 and while the waves would be there, just the same, whether 

 they struck the eye or not, they would not produce the same 

 result. It may practically be said that if there is not an eye 

 to see, there is no light. Those particular waves which pro- 

 duce the sensation of light in the eye do not produce other 

 effects to any extent, for the heat effect and the chemical 

 effects which we receive are due to waves of a different 



