The Evolution of the Sciences 



disc and supply the characteristic element in 

 the monotonous brightness of its surface. If 

 they did not exist, or if we were unable to study 

 them, our ideas of the nature of the sun would 

 be very uncertain. 



Nothing could be more irregular than these 

 spots; they are of all dimensions, positions and 

 forms. Some, called pores, look like mere black 

 spots under the highest magnification; others, 

 visible to the naked eye, are several times larger 

 than the surface of the earth. Their formation 

 and changes are sometimes slow, and sometimes 

 disconcertingly rapid. 



" On July the 28th, 1865," relates Secchi, 

 " nothing extraordinary was to be seen, neither 

 pores nor faculse; on the 2gth only three black 

 points; at 10.30 o'clock on the 3oth we were 

 surprised to find the centre of the disc occupied 

 by an enormous spot, the mean diameter of the 

 disturbed region being about 4^ times the dia- 

 meter of the earth. At the centre we noticed 

 a heap of luminous matter, apparently in 

 whirling motion and surrounded by many rents. 

 Within this chaos four centres of motion could 



be distinguished. On the left was visible a vast 



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