432 Saturn's Ring. — Double Stars. — Occultations. 



my 3/o-ixiah. aperture the disc appeared yellow, surrounded by 

 flashes of deep crimson, mixed, or rather alternating, with a 

 smaller quantity of beautiful green rays. My attention was 

 called to this peculiarity by an old observation of Dr. Forster, 

 in which he stated that he had " observed a remarkable chang- 

 ing of colour in Antares : for a second or two of time it appeared 

 of a deep crimson colour, then of a whitish colour ; then the 

 crimson was resumed," the red colour being irregular both in 

 its alternations and continuance. He ascribes a similar pheno- 

 menon, in a less degree, to Betelgeuze, Aldebaran, and other 

 red stars. The attendant registered by Smyth is very distant, 

 and I have not entered it ; but a much more interesting dis- 

 covery has since been made by Professor Mitchell with a 

 12-inch Munich refractor at Cincinnati, U. S., of a very near 

 bluish-green companion; thus constituting it the only close 

 double star of the first magnitude hitherto known. Our astro- 

 nomer royal thought it would be impossible to see it in Eng- 

 land, but it was detected by Dawes several times with a Cl- 

 inch object-glass, and found to have a distance of about 3""5, 

 and an angle of 273 0, 17; and on March 27, 1856, he saw it 

 with 8-inches under most interesting circumstances, emerging 

 from behind the dark limb of the moon, about 7 s before the 

 principal star appeared; it was thus proved that its magnitude 

 was about the 7th, and its colour independent, and not, as 

 might have been supposed, the effect of contrast. The fol- 

 lowing remark by this great observer is worthy of attention : — 

 "If the angle of position were nearly coincident with the 

 meridian, it would be almost impossible to observe the small 

 star in these latitudes, as the bright star forms a strong pris- 

 matic spectrum in that direction. This atmospherical effect 

 may, however, be in a great measure counteracted by using 

 a single lens as an eye-glass, or by the ordinary double micro- 

 meter eye-piece. The star being placed towards the southern 

 (upper) side of the field of view, the eye-piece spectrum may 

 be made very nearly to neutralize the atmospheric spectrum, 

 and a very tolerable image obtained under favourable circum- 

 stances." Hippisley also has seen the comes twice with a 9j- 

 inch Newtonian, and his remark likewise is deserving of being 

 cited, as to " the great value of the half-hour at and after sun- 

 set, for the more delicate and difficult observations in all cases 

 where the object has light enough to be well visible telescopi- 

 cally by daylight, such as exists at that period. This may 

 probably arise from the short equilibrium between the heat of 

 day and the chill of evening ; during which atmospheric dis- 

 turbances, arising from the intermixture of beds of air of dif- 

 ferent temperatures and densities, may be expected to be at a 

 minimum." Secchi, after several failures, which led him to 



