Solar and Planetary Evolution. 



65 



formed originally from an invisible gas. The great nebula 

 in the sword of Orion (see Figure 8, page 63) shows many- 

 points of condensation. From it will be developed a little 

 universe within a greater universe, forming in time not a 

 single sun or star, but a cluster of stars. 



We have seen in the nebulae evidencies of rotation and 

 contraction. Now let us consider the condition of a body 

 after it has passed out of the nebulous into the solid state. 

 (A picture of a portion of the sun's surface is thrown upon 

 the screen, showing a dark back-ground, mottled with 

 shining spots. See illustration, Figure 9, on page 64,. 



Fig. 10. Section of the Sun's Surface, showing a belt of sun-spots, near the 



center of the disk. 



opposite.) The surface of the sun, of which we shall first 

 speak, is not uniformly clear and shining, but broken up into 

 bright parts interspersed with parts that are less luminous. 

 The shining portions are sometimes called "rice-grains," 

 from their appearance, and seem like clouds of luminous 

 matter. These are the parts of the sun which give light. 

 Sir John Herschel suggested that they might be "living or- 

 ganisms," but they are merely the hotter portions of the 

 solar surface. Among them sometimes appear great rifts or 

 spots (a picture of solar spots is thrown upon the screen) 

 which are never seen at the poles, but always within a cer- 



