PLEASURES OF THE TELESCOPE. 747 



sun about 375,000 times in volume, and that its diameter is no less 

 than 62,350,000 miles ! Imagine the earth and the other planets 

 constituting the solar system removed to Arcturus and set re- 

 volving around it in orbits of the same forms and sizes as those 

 in which they circle about the sun. Poor Mercury ! For that lit- 

 tle planet it would indeed be a jump from the frying pan into the 

 fire, because, as it rushed to perihelion. Mercury would plunge 

 more than 2,500,000 miles beneath the surface of the giant star. 

 Venus and the earth would perhaps melt like snowflakes at the 

 mouth of a furnace. Even far-away Neptune, the remotest mem- 

 ber of the system, would be bathed in torrid heat. 



But stop ! Look at the sky. Observe how small and motion- 

 less the disks of the stars have become. Back to the telescopes at 

 once, for this is a token that the atmosphere is steady, and that 

 " good seeing " may be expected. It is fortunate, for we have 

 some delicate work before us. The very first double star we try 

 in Bootes, % 1772, requires the use of the four-inch, and the five- 

 inch shows it more satisfactorily. The magnitudes are sixth and 

 ninth, distance 5" ; p. 140. On the other side of Arcturus we 

 find ^, a star that we should have had no great difficulty in sepa- 

 rating thirty years ago, but which has now closed up beyond the 

 reach even of our five-inch. The magnitudes are both fourth, and 

 the distance about 0'5", p. 285. It is apparently a binary, and if 

 so will some time widen again, but its period is unknown. The 

 star 279, also known as 2 1910, near the southeastern edge of the 

 constellation, is a pretty double, each component being of the sev- 

 enth magnitude; distance 4"; p. 212. Just above ^ we come 

 upon TT, an easy double for the three-inch, magnitudes fourth and 

 sixth ; distance 6" ; p. 99. Next is ^, a yellow and purple pair, 

 whose magnitudes are respectively fifth and seventli ; distance . 

 less than 3" ; p. 231. This is undoubtedly a binary with a period 

 of revolution of about a hundred and thirty years. Its distance 

 decreased about 1" between 1881 and 1891. It was still decreasing 

 in 1894, when it had become 2-9". The orbital swing is also very 

 apparent in the change of the position angle. 



The telescopic gem of Bootes, and one of " the flowers of the 

 sky," is , also known as Mirac. When well seen, as we shall see 

 it to-night, e Bootis is superb. The magnitudes of its two compo- 

 nent stars are two and a half (according to Hall, three) and six. 

 The distance is about 2-8", p. 32(5. The contrast of colors-bright 

 orange yellow, matched with brilliant emerald green is magnifi. 

 cent. There are very few doubles that can be compared with it 

 in this respect. The' three-inch will separate it, but the five-inch 

 enables us best to enjoy its beauty. It appears to be a binary, but 

 the motion is very slow, and nothing certain is yet known of its 

 period. 



