196 THE POPULAR SCIENCE MONTHLY. 



situated rather more than 40" apart. A high power divides the 

 seventh-magnitude companion into two, each of magnitude six 

 and a half; distance l'S", p. -42. But (and this was another of 

 Burnham's discoveries) the fourth-magnitude star itself is double ; 

 distance OS", p. about 0. The companion in this case is of mag- 

 nitude five and a half. 



Next we shall need a rather low-power eyepiece and our largest 

 aperture in order to examine a star cluster, No. 4173, which was 

 especially admired by Sir William Herschel, who discovered that 

 it was not, as Messier had supposed, a circular nebula. Herschel 

 regarded it as the richest mass of stars in the firmament, but 

 with a small telesc }pe it appears merely as a filmy speck that has 

 sometimes been mistaken for a comet. In 18G0 a new star, be- 

 tween the sixth and seventh magnitude in brilliance, suddenly 

 appeared directly in or upon the cluster, and the feeble radiance 

 of the latter was almost extinguished by the superior light of the 

 stranger. The latter disappeared in less than a month, and has 

 not been seen again, although it is suspected to be a variable, and, 

 as such, has been designated with the letter T. Two other known 

 variables, both very faint, exist in the immediate neighborhood. 

 According to the opinion that has generally been looked upon with 

 favor, the variable T, if it is a variable, simply lies in the line of 

 sight between the earth and the star cluster, and has no actual 

 connection with the latter. But this opinion may not, after all, 

 be correct. The cluster 4183, just west of Antares, is also worth 

 a glance with the five-inch glass. It is dense, but its stars are 

 very small, so that to enjoy its beauty we should have to employ 

 a large telescope. Yet there is a certain attraction in those far- 

 away glimpses of starry swarms, for they give us some perception 

 of the awful profundity of space. When the mind is rightly 

 attuned for these revelations of the telescope, there are no words 

 that can express its impressions of the overwhelming perspective 

 of the universe. 



The southern part of the constellation Ophiuchus is almost in- 

 extricably mingled with Scorpio. We shall, therefore, look next 

 at its attractions, beginning with the remarkable array of star 

 clusters 4264, 4268, 4269, and 4270. All of these are small, 2' or 

 3' in diameter, and globular in shape. No. 4264 is the largest, and 

 we can see some of the stars composing it. But these clusters, 

 like those just described in Scorpio, are more interesting for what 

 they mean than for what they show ; and the interest is not 

 diminished by the fact that their meaning is more or less of a 

 mystery. Whether they are composed of pygmy suns or of great 

 solar globes like that one which makes daylight for the earth, 

 their association in spherical groups is equally suggestive. 



There are two other star clusters in Ophiuchus, and within the 



