April U, 1882.] 



KNOWLEDGE • 



511 



NIGHTS WITH A THREE-INCH 

 TELESCOPE. 



Bv "A Fei-i.ow of tue Roval Astronomical Society." 



BEFORE beginning our examination of the Constella- 

 tion ^'irgo to-night, we will return to that of Hydra 

 for the purpose of looking at a very wonderful object, 

 omitted in our description on p. 376. The student will 

 find it by lishing with a power of 100 or so about 2'^' (four 

 diameters of the moon) to the south of fj Hydr;e (map p. 474). 

 It is No. 27 of Uerschel's IVth Catalogue, and is one of 

 the most remarkable planetary nebulae in the heavens. 

 ITnlike nebuhe generally, this will bear considerable 

 magnifying power. It will be seen as a pale-blue disc, 

 looking just like the ghost of Jupiter. As Huggins has 

 shown tiiat it is gaseous, the sharpness of its outline is 

 verv curious. 



Fig. Ii6. Fig. a. Fig. h. 



Turning now to Virgo, we will begin with that most 

 interesting star y, which is shown in Fig. 26, as seen with 

 a power of 160. When first observed by Herschel, in 

 1790, the components of this star were nearly 6" apart, but 

 were approaching each other ; and in 1836 were so practi- 

 cally superposed as to appear single under the very highest 

 power that Admiral Smyth could apply to them upon his 

 5 '9 inch achromatic. Since that time they have been 

 separating, and their distance at present amounts to about 

 o", so that they form an easy pair in the instrument we 

 are using. Virginis (map, p. 474) is a \ery pretty and 

 interesting triple ; the third star, which is nine times as 

 far from the large one as its more obvious companion, 

 will require a dark night and pretty sharp sight to see it 

 well. There are very many beautiful and interesting pairs 

 , of stars in Virgo ; but as they are mostly below the sixth 

 magnitude they are not marked in the monthly maps in 

 Knowledge, and no amount of description would enable 

 the reader to identify them. Fortunately, simple sweeping 

 in the marvellous region to which we are about to introduce 

 the reader, will suffice to enable him to pick up many of 

 the wonderful mass of nebuhe collected within the area 

 roughly bounded by e, c, y, jj, and /3 Virginis, and /3 Leonis. 

 If the student will arm his instrument with a power of 

 about 40, and sweep slowly over that part of the sky con- 

 tained within the curve drawn through the stars we have 

 ■named (map p. 4T4), he cannot fail to be astonished and 

 pleased at the wealth of nebulous objects, and the pretty 

 fields of stars that he will encounter. One of these curious 

 objects is shaped like a boy's kite. A few are resolvable 

 into stai's in some of the enormous telescopes now com- 

 paratively common. Others are unmistakably gaseous. 



Above Virgo is situated Coma Berenices, easily recognis- 

 able in the sky by the coarse cluster of stars in its north- 

 western portion. If the reader will draw an imaginary 

 line from a through 36 on the map (p. 474), then at about 

 three times as far to the right of 36 as 36 is to the right of 



fi, and a little above such line, will be found 24 Coma% a 

 wide double star, but interesting from the beautiful con- 

 trast of orange and pale-purple presented by its components. 

 Just above, and to the left of a Coraie (map p. 474), what 

 will appear like a nebula will be found. It is 53 of 

 Messier's Catalogue, and is really an immense mass of tiny 

 stars ; but it requires a much more powerful instrument 

 than ours to show this. Other nebula', mostly faint, will 

 be found among the cluster of stars to which we have 

 previously referred. 



Adjoining Coma Berenices above lies Canes Venatici, of 

 which the chief star o, 12, or Cor Caroli — for it has all 

 three designations — is a widish double. About one-third 

 of the way between Cor Caroli and c Leonis 2 Canum 

 will be found ; a close pair, with prettily contrasted 

 colours. There are numerous other pairs in this constella- 

 tion, but, for the so often reiterated reason, we can give 

 no intelligiljle directions for finding them. In the case of 

 more than one of the remarkable nebula?, however, con- 

 tained in it, we trust to be more successful in point- 

 ing out their whereabouts. 3° (6 diameters of the 

 moon) to the south-west of y Ursie Majoris, the star 

 at the end of the Great Bear's tail, will be found two 

 rather dim nebuL-e, nearly touching each other. This is 

 Messier .51, the astonishing Spiral nebula, which, as seen in 

 Lord Rosse's great telescope, has been pictured in so many 

 works on astronomy. About midway between Arcturus and 

 Cor Caroli, but rather nearer the former (map p. 474), will 

 be found a bright nebula, Messier 3, which large telescopes 

 resolve into a brilliant condensed cluster of minute stars. 

 Some 2i° to the north-west of Cor Caroli, is a nebiUa, 

 94 Messier, which, though small, is sufficiently conspicuous 

 in the class of instrument we are using. Other nebula; in 

 this constellation may be picked up by fishing, especially 

 in the region between a Canum Venaticorum and ^ Ursaj 

 Majoris. 



[As but one figure came from our esteemed contributor, 

 F.R.A.S., this week, we have ventured to add two 

 doubles, viz., £ Bootis, fig. a, and c Bootis, fig. b. Both 

 stars are shown in our monthly map, No. 22, for March 

 31.— Ed.] 



THE AMATEUR ELECTRICIAN. 



ELECTRICAL GENERATORS. 



THE task we have set ourselves in this series of papers 

 is not by any means an easy one. Our object is to 

 help, by practical and easily-followed-out instructions, those 

 who desire to become experimenters in this most interesting 

 department of physical science. There is no " Royal road " 

 to a thorough knowledge of the laws of electricity, any more 

 than of any other science, and our readers must, therefore, 

 please understand that while every eflbrt will be made to 

 render each branch of the subject dealt with as complete as 

 possible, a " text-book " on electricity is beyond our scope. 

 It is anticipated that we shall soon be at liberty to imtiate 

 a series of papers on the rudimentary demonstrations of 

 electrical properties, but here the assumption must be 

 allowed, that our readers know just a little of the science. 



The present production of large quantities of electricity 

 — larger than were ever conceived to be possible — necessi- 

 tates some agency other than the galvanic battery. Indeed, 

 the battery could never have yielded so bountiful a supply 

 of electric force as is now being utilised in very many 

 places — notably the Crystal Palace Electrical Exhibition. 

 Why this is we will not attempt to explain now, although 

 it may be found advisable to do so hereafter. It is not 

 difficult to conceive that one of the features in the 



