The Planets of the Month. 233 



diameter of the satellite on the dark ground of the sky, and 

 diminishing that of the shadow on the luminous face of the 

 planet. We have at present no means of interpreting this mys- 

 tery. As the more obvious features of these curious and beau- 

 tiful phasnomena may be perceived with a very moderate 

 aperture — I have myself seen the " ink-spots " well with only 

 three inches — we shall give a list of all that are visible at con- 

 venient hours during the present month ; including May 1st, for 

 the sake of readers whom our information might not otherwise 

 reach in time. 



April 1st. I. is on the disc from 8h. 10m. to lOh. 27m. fol- 

 lowed (as always after the planet's opposition) by its shadow. 

 2nd, II. emerges at 7h. 41m. ; the shadow continuing in sight 

 an hour longer. 8th, I. is in transit from 9h. 57m. to 12h. 13m. 

 9th, shadow of II. enters at 8h. 27m., the satellite being already 

 on the disc; egress of II. 9h. 57m.; of shadow, llh. 15m. 

 IV. having crossed already, and being to the left of the planet 

 in an inverting eyepiece, its shadow comes on separately at 

 9h. 28m. and leaves at 12h. 34m. . 15th, I. enters at llh. 43m., 

 followed by the shadow at 12h. 28m. 16th, II. enters at 

 9h. 28m., its shadow at llh. lm. ; it goes off at 12h. 15m., the 

 shadow at 13h. 49m. 17th, I. leaves the disc at 8h. 26m. ; its 

 shadow at 9h. 14m. 22nd,. I. enters at 13h. 30m., the shadow 

 at 14h. 23m. 23rd, II. enters at llh. 45m., the shadow at 

 13h. 36m. 24th, I. egress at lOh. 14m., ditto of shadow at 

 llh. 9m. 27th, III. being already off the planet to the left, 

 the shadow enters at 8h. 13m., and departs at llh. 28m. 

 May 1st, I. is on the disc from 9h. 46m. till 12h. 3m.; the 

 shadow enters at lOh. 47m. 



It will be seen that there is no chance of a thoroughly dark 

 transit this month, as III. and IV. will not be on the disc; but, 

 weather permitting, we must not miss the interesting sight on 

 the 9th, when the shadows of II. and IV. will both be visible 

 at once for nearly two hours ; and we shall not fail to remark, if 

 we have a sufficiently powerful instrument, the contrast in the 

 size of the spots, as well as the difference in their velocities, and 

 distances from the bodies which cast them. 



The presentation of Saturn's ring as a slender but conspi- 

 cuous line, will be very beautiful this month. The Sun and 

 Earth are at present both on the same side of it ; were they 

 both at the same elevation above its plane, it would, of course, 

 exactly conceal its own shadow ; but as the the Earth is slightly 

 the more elevated, we see a very little under its inner edge, as 

 compared with the Sun (the south side being the one visible), 

 and it is possible that in fine telescopes a very narrow black 

 line, the edge of the shadow, may cross the centre of the ball. 

 The belts on each side of the equator seem to be faint this 



