JONE 9, 1882.] 



KNOWLEDGE ♦ 



21 



section of a fine crystal of nepheline, in Phonolite basalt, 

 from Solllifrg Eisel. The crystal in shape is a hexaj,'onal 

 prism, and has been cut almost at right angles to its base. 

 During its growth it has enclosed within it other small 

 crystals and part of the base of the rock. Round the 



outer edges this may particularly be noticed : it would 

 seem as though the power wh'.ch determines the crystalline 

 form, at the last, had just sufficient energy to complete the 

 shape of the crystal ; but, with the growing rigidity of the 

 cooling mass, lacked the strength to e.xpel these foreign 

 particles, and was perforce content to enclose them within 

 itself. 



By 



NIGHTS WITH A THREE-INCH 

 TELESCOPE. 



"A Fellow of the Royal Astronomical Society. 



TO the east of Bootes lie the constellations Corona 

 Borealis and Serpens, which we shall now proceed to 

 examine. Beginning with the former (which really does 

 present more than the ordinary resemblance to the object 

 wjiose name it bears), we shall find a very interesting double 

 star in ^ (map, Vol. I., p. 626), the components exhibiting 

 well-contrasted colours. Its aspect, as seen with a power 

 of 160, is shown in Fig. 33. a Coronas is a very pretty pair 

 indeed ; it is delineated in Fig. 34, as viewed with the same 

 power as the last star, a will be found in the sky as nearly 

 as may be 10° N.E. of « Corona?. This is sometimes ranked 

 as a triple star, as the pair shown in our sketch are fol- 

 lowed, at a distance of .'il" or .'jS", by a minute blue star. 

 a itself is one of what are known as binary stars — i.e., 

 physically connected pairs; and, in the description of 

 their orbits, about their common centre of gravity, its com- 



ticrpuiitia. 



ponents have separated from 1".3 in 1830, to something 

 like 3".r) now. One of the most interesting of these binary 

 systems, that of >; Corona', is uTifortunately (juite liopelessly 

 Vx^yond the power of our instrument, as the two stars are 

 now less than 0.5" apart, and are closing. Their distance 

 varies from about 1.4" to 0.3", and their orV)it is described 



in something over forty years. There arc several pairs of 

 telescopic stars in this constellation, all of them tolerably 

 easy to divide, but it is very difficult to give directions for 

 finding them in the absence of an equatorially-mounted 

 telescope with divided circles. An easy one (Struve, 1,964) 

 will be found a little to the south-west of I described above. 

 While going over Corona, the student should not omit to 

 glance at that most astonishing object, T Coronse ; the star 

 which blazed up suddenly as a second magnitude one in 

 the year 1866. Examined by our greatest English spectro- 

 .scopist, Dr. Ifuggins, on May 16 in that year, it was found 

 to exhibit a double .spectrum ; one analogous to that shown 

 by our own sun, the other one that of glowing gaseous 

 hydrogen ; this (possibly) indicating a conflagration on a 

 stupendous scale. Subsequently to this the star faded to 

 the 9th magnitude, revived again somewhat, and has since 

 been irregularly variable. At present it appears as a star 

 of about the OUh magnitude. It is situated on an imagi- 

 nary line drawn from t Corona; to tt Serpentis, at rather 

 less than one-third of the distance between the two from t. 

 Serpens, to which we shall next devote our attention 

 (Map, Vol. I., p. 626), is one of those straggling and sprawl- 

 ing constellations so difficult to follow in the sky. Never- 

 theless it is one containing many beautiful and interesting 

 objects. To Ijegin with, a is a very wide and unequal pair, 

 the smaller component requiring a good deal of looking for 

 with a small telescope. We insert it here for the prettj 

 contrast in colours which it presents. I Serpentis, shown 

 in Fig. 3.5, is a very neat and pretty binary star. The 

 components are at present separating, /i is, like o, a 

 widish and very unequal pair, the small star, as in the 

 former case, being bluish. S Serpentis is comparatively 

 wide and easy. It will well repay examination from the 

 richness of the region in which it lies. >- Serpentis, 4° 

 north-east of ?;, is also wide and easy. As befcre, we men- 

 tion it for the pleasingly- contrasted colours of its com- 

 ponents. 5 Serpentis (9° south-west of a) is much closer, 

 and very unequal. It will repay examination. 10J° to 

 the north-east of « Serpentis, on a line drawn from that 



st.ir to Vega, will be found 49 Serpentis- a line pairr 

 .^hown in Fig. 36. This is a binary s^ysteni, with a sup- 

 ].os.d period of 900 years! .'i9 (or (/) Serpentis is a 

 beautiful oV>ject, the colours of its close and unequal com- 

 jicments being strongly contrasted. It is represented iu. 

 Kig. 37. Smyth's directions for finding this star anv 

 p(rhap.s as good as any. " To identify ."i".* Serpei.tis," h»- 

 suvs, "let an east-south-ea.st ray be shot fn.m /> Herculis 

 through .1, which will l)C found two-fifths of tlie way " (i".<., 

 from /> Herculis to 59 Serjientis). 



Libra (Map, Vol. I., p. 626) is neither a striking oonst*-!!*- 

 tion to tho naked eye, nor does it contain many objects acces- 

 sible to the class of instrument we are employing. A small, 

 but easy, pair of stars will bo found in No. 62 of Piaizi, 

 XlVth hour. It lies 1.5" east by north of Spica Vircinis, 

 or 2 A° south-west of i in the same constollation. 9 due 

 west" of /3 Scorpii will bo found P. XV. 91, a not very 



