The Sun 



221 



To observe solar eclipses and sun spots. Any of the 

 following devices may be used in observing eclipses and 

 sun spots : 



(1) Expose a photographic plate to the light and then 

 develop it, or hold a piece of window glass in a smoky 

 flame. Either the fogged plate or the smoked glass may 

 be used to protect your eyes. 



(2) With a nail make a hole through a piece of tin 

 which you can nail over a knot hole in a barn or other 

 building. The sun's rays passing through the nail hole 

 will form an image on a piece of white paper held in 

 their path. Sunlight shining through a small hole in a 

 curtain into a room that is rather dark may be similarly 

 used to form an image. 



(3) When the sun is partially eclipsed, punch a hole 

 through a cardboard and observe the image on paper 

 held in the path of the rays that come through the 

 hole. 



Questions about the sun. Why can we safely look 



FIG. 136. Diagram to show an eclipse of the sun. The smaller body repre- 

 sents the moon, which is between the earth and the sun. Where the dark central 

 shadow touches the earth the light is cut off from the entire disk of the sun, and 

 in this area the eclipse is total. The part of the earth's surface covered by the 

 wide lighter shadow is illuminated by light from a part of the sun, and in this 

 area the eclipse is partial. 



