Work for the Telescope. 265 



WORK FOE THE TELESCOPE— PLANETS OF THE 

 MONTH— DOUBLE STARS. 



BY THE EEV. T. W. WEBB, F.R.A.S. 



PLANETS OF THE MONTH. 



Mekcuey will be favourably situated towards the end of the 

 month., and may be looked for with the naked eye, between 

 sunset and 10 p.m. 



Venus continues very brilliant in the mornings. 



The transits of Jupiter's satellites and their shadows will 

 occur as follows : — 



May 1st was included in our last number. 4th, III. 

 emerges at llh. 14m.: its shadow enters at 12h. 12m. 8thy 

 I. enters at llh. 36m. : its shadow at 12h. 42m. 10th, shadow 

 of I. goes off, 9h. 27m. 11th, shadow of II. emerges at lOh. 

 49m. III. enters at llh. 34m. 12th, IV. enters at lOh. 40m. 

 1 7th, shadow of I. comes on, 9h. 6m., the satellite itself leaves 

 at lOh. 12m.: the shadow at llh. 22m. 18th, shadow of IL 

 enters at lOh. 37m. II. goes off, llh. 24th, I. enters at 9h. 

 47m., and departs at 12h. 4m. : the shadow's ingress is at llh. 

 lm. 25th, I. comes on, lOh. 40m. 31st, I. enters at llh. 40m. 



It will be observed how much the satellites and shadows 

 have widened their distance in proportion to the increasing 

 departure of the planet from opposition to the Sun. There 

 maybe some hope of dark transits on 4th, 11th, and 12th; 

 but we must look out carefully, for the planet is getting further 

 from the Earth, and by the end. of the month his diameter will 

 have diminished to 3 5" -4. 



The most interesting phenomenon in the heavens at the 

 present season is unquestionably the disappearance of the ring 

 of Saturn, which will take place May 18, from which time, till 

 August 12, the planet will appear destitute of this magnificent 

 ornament, if ornament that may be called, which is no doubt 

 so constructed by the All- wise Creator, as to subserve the most 

 important and beneficial purposes. The cause of the pheno- 

 menon is pretty generally understood ; but it may be well to 

 refer to it in this place on account of some curious details con- 

 nected with it. The position of this great plane (or rather 

 assemblage of planes — the only flat surface that we know of in 

 the universe) does not coincide with the plane of the orbit of 

 Saturn : if it did, it would always present its edge to the sun, 

 and neither of its sides would receive more than a horizontal 

 illumination. Nor does it lie in the plane of the orbit of the 

 Earth, which is inclined to that of Saturn, and, exceptiug in 



