PLEASURES OF THE TELESCOPE. 



205 



Sweeping northwestward to , we find a celebrated binary, to 

 separate which will require the higher powers of our five inch 

 glass. The magnitudes are three and six and a half, distance in 

 1894 1"28", p. 40 o . The period of revolution is thirty-five years, 

 and two complete revolutions have been observed. The apparent 

 distance changes from 0'6" to 1"G". They were at their extreme 

 distance in 1884 and are now closing. 



Two pleasing little doubles are % 2101, magnitudes six and nine, 

 distance 4", p. 57, and 2 2104, magnitudes six and eight, distance 

 6", p. 20. At the northern end of the constellation is 42, a double 

 that requires the light-grasping power of our largest glass. Its 

 magnitudes are six and twelve, distance 20", p. 94. In p we dis- 

 cover another distinctly colored double, both stars being greenish 

 or bluish, with a difference of tone. The magnitudes are four and 

 five and a half, distance 37", p. 309. But the double 95 is yet 

 more remarkable for the colors of its stars. Their magnitudes are 

 five and five and a half, distance 6", p. 262, colors, according to 

 Webb, " light apple-green and cherry-red." But other observers 

 have noted different hues, one calling them both golden yellow. 

 I think Webb's description is more nearly correct. 2 2215 is a 

 very close double, requiring larger telescopes than those we are 

 working with. Its magnitudes are six and a half and eight, dis- 

 tance 0'?", p. 300. It is probably a binary. 2 2289 is also close, 

 but our five-inch will separate it : magnitudes six and seven, dis- 

 tance 1'2", p. 230. 



Turning to /a, we have to deal with a triple, one of whose stars 

 is at present beyond the reach of our instruments. The magni- 

 tudes of the two that we see are four and ten, distance 31", p. 243. 

 The tenth-magnitude star is a binary of short period (probably 

 less than fifty years), the distance of whose components was 2" in 

 1859, 1" in 1880, 0*34" in 1889, and 0-54" in 1891, when the position 

 angle was 25, and rapidly increasing. The distance is still much 

 less than 1". 



For a glance at a planetary nebula we may turn with the five- 

 inch to No. 4234. It is very small and faint, only 8" in diameter, 

 and equal in brightness to an eighth-magnitude star. Only close 

 gazing shows that it is not sharply defined like a star, and that it 

 possesses a bluish tint. Its spectrum is gaseous. 



The chief attraction of Hercules we have left for the last, the 

 famous star cluster between 77 and , No. 4230, more commonly 

 known as M 13. On a still evening in the early summer, when 

 the moon is absent and the quiet that the earth enjoys seems an 

 influence descending from the brooding stars, the spectacle of 

 this sun cluster in Hercules, viewed with a telescope of not less 

 than five-inches aperture, captivates the mind of the most uncon- 

 templative observer. With the Lick telescope I have watched it 



