820 Professor Percival Lowell April 8, 



ments of shading traversing the belt from triangular spots at its 

 edges, for all the world like the lacings of a sail that hold the bolt- 

 rope to its spar. Though perfectly evident to the eye, we hardly 

 hoped to catch them on a plate. Nevertheless, Mr. E. C. Slipher 

 did, and innumerable other images of them have since been got by 

 us ; their pictures you will presently see for yourselves upon the 

 screen. Why such peculiar rents should be torn in the planet's great 

 cloud envelop we cannot yet explain, but further news about them 

 has still more lately come to us from the planet to which we now 

 pass, the great ringed planet Saturn. 



In some respects Saturn is the most difficult of the three planets to 

 photograph, certainly the most tiring. So faintly is it illuminated 

 that what takes but two seconds for Mars, takes twenty or more for 

 Saturn. To keep the image of the planet upon its guiding cross- 

 wires for that length of time, with the nervous knowledge that any 

 slip will be fatal, seems an eternity. Since sensations measure exist- 

 ence, it may be commended as a sure though not happy way to 

 prolong one's life. 



On the resultant images may be seen abundant detail. Cassini's 

 division is there as large as life and somewhat broader, due to the 

 difficulty of keeping it still ; so also is the shading of the inner side 

 of ring B, and the tones of the several portions of ring A. The ball 

 appears finely, its belts standing out even more than to the eye, and 

 the duskiness of its polar hoods being peculiarly pronounced. The 

 shadow of the ball upon the rings is, of course, salient, and so is the 

 shadow of the rings upon the ball. This much is evident at a glance, 

 but there is more to be made out by him who examines closely. 



If we consider the images of November 4, which happen to be 

 mine, we shall notice a dark band below the rings where they cross 

 the ball, and one which is l)ut dusky above them. Now at this date 

 both the sun and the earth were above the plane of the rings, as we 

 see the image, the sun the higher ; the sun's relative latitude being 



that of earth 



12 18' 

 ll*^ 4' 



We saw in consequence the shadow of the rings A and B under- 

 neath the rings themselves. This accounts for the dark band below. 

 What then was the dusky band above ? It could not be the shadow 

 of these rings, for the shadow could not fall on both sides of them at 

 once, nor could it be seen above. A little consideration will reveal 

 to us what this band was. Inside of ring B toward the planet lies 

 the crepe-ring C. It is a semi-transparent ring because its particles 

 are widely scattered, instead of seeming sohd like the outer rings 

 where the particles lie closer together. Their constitution we owe 



