MARIA MITCHELL. 107 



spaces between the different rings. An inner dusky 

 ring, called the "gauzy ring" stretches toward the ball. 

 Although it is supposed that we see the background of 

 the sky between the rings and the ball, yet there is no 

 record of a star seen in this space. I have seen Saturn 

 in a strong warm twilight, yet the blackness of this 

 space has not been modified by the brilliant back- 

 ground. 



In certain positions of the ring, the gauzy,, dusky, 

 inner ring is projected upon the ball as a dark band ; at 

 times, on the other border of the ring is also a dark 

 band. What can this dark bordering of the outer ring 

 be? 



That the ring is of unequal thickness is obvious. 

 When it is seen as a line, this line is broken up into 

 small points, as the coast line is when you leave the 

 shore and go out into full sea. 



Spots are seen upon the surface of the ring. We call 

 them shadows. If there are shadows thrown by the ball, 

 the ball must be irregular in shaj>e. 



We are so liable to illusions, that an astronomical ob- 

 server is fortunate if he can call to his aid some novice 

 in astronomy to assist his judgment in regard to the 

 meaning of lights and shades — if possible, an artist. 

 Above all other combats, the old observer has that with 

 his own perceptions and with his favorite hyj)otheses. 



Minute objects, which will bear no illumination of the 

 field of view, but are seen only in intense darkness, can- 

 not be measured ; different eyes must do the work of 

 the micrometer ; relative size, color, brightness, and mo- 

 tion must be determined by the estimates of unbiased 

 observers. 



Saturn is known to have eight moons. 



Mimas, the nearest to the planet, is rarely seen. It 

 shoots out quickly from the edge of the ring, rushes 

 quickly back, and is lost in the brilliancy of Saturn. 



59 



