April 2, 1900.] 



KNOWLEDGE 



81 



Fig. 2. — CiiTus ia wisps. Same object glass. Strong 

 yellow sereeu. Stop = j'j- Exposure=l^ secoucl. 



Fiij. 3. — Uuilulatetl Cirro-t-umuli, seen iluriui,' a sjiell of 

 suushiue duriii;4 niiuy weather. Same objeet glass. Mean 

 coloured screen. Stop=/j. Eximsure 1± second. 



It is thus obvious that as far as cxposui-c is concerned, 

 continued practice will be the safest guide. The student 

 should also bear" in mind that with a long focus glass. 

 rapidly moviiig clouds, such as scud flying before 

 heavier masses dm'ing a gale, should be photographed 

 with very short exposures only, if he seek to avoid the 

 disagreeable effect of dimness due to the clouds' motion. 



(To bf continued.) 



MME. CERASKIS SECOND ALGOL VARIABLE. 



Another remai-kablo variable star of the AJgol class has 

 been discovered by Mme. Ceraski, and is announced in 

 the Astron. Nach. 151, 223. The position for 1900 is 

 E. A. = 19 h. 42m.7, Dec. = +32^ 28'. From an 

 examination of the Draper Memorial photographs of this 

 star, it appears that while the star has its full bright- 

 ness on 45 of them, on several of the early photographs 

 it is so faint that they must have been taken when the 

 star was near minimum. The Moscow photographs 

 furnish the means of detennining the period from an 

 interval of four years, the Harvard photographs increase 

 this interval to nine years. The period is 6d. Oh. 8m. 8. 

 The period diffei-s so little from exactly 6 days that for 

 a long time the minima cannot be observed in certain 

 longitudes. Accordingly, while valuable obsei-vations 

 may be obtained next autumn in Europe, or better still 

 in Asia, minima cannot be obsei-ved in Amei-ica until 

 the following year. 



Five stars of the Algol class, S Caucri, U Cephei, 

 AV Delphini, + 45^3062, and the present star are. es- 

 pecially interesting, owing to the lai'ge variation in their 

 light, which amounts to about two magnitudes in each 

 case. It is remarkable that two of these were found 

 by Mme. Ceraski, and one by her distinguished husband. 



Edwakd C. Pickering. 



Harvard College Observatorv, 

 February 12th, 1900. 



ASTRONOMY WITHOUT A TELESCOPE. 



By E. Walter Maunder, f.r.a.s. 



III.— THE NORTHERN STARS'. 



The stars wear a very different aspect to the astronomer 

 with a telescope and the astronomer without. The 

 former, deep in his observatory dome, sees but a narrow 

 slice of the sky through the open shutter, and the starry 

 groupings as such have little or no significaLce for him. 

 If he wishes to bring a star within the field of his 

 instrument, he does not as a rule seek it out first on the 

 sky, and thers aim his telescope at it like a rifle by its 

 sights. Instead he refers to his catalogue, reads therein 

 the right ascension and declination of the object, turns 

 his instrument iintil its circles are set to the readings 

 indicated by the catalogue, and then, last of all, moves 

 his dome round until the shutter opening is opposite 

 the object glass. The names of the stars, the constel- 

 lations in which they are found, have therefore very 

 little significance for him. The important things for 

 him to know are the hour, minut<i and second to which 



the 



ncc and luinule to 



the one circle must be set; 

 which the other. 



Not so with his brother worker, lie stands out under 

 the open heaven ; no graduated circles guide his gaze 

 to this s'ar or that, For him, if ho will know precisely 

 to what part of the heavens he is directing his attention, 

 it is necessary to be able to recognise the individual 

 stai-s. In this work differences of brightness and colour 

 are no small help, but by themselves would be perfectly 

 inadequate guides to the recognition of the great 

 majority of the stars. That by which one star can be 

 recognised from another is in most cases its grouping 

 with the rest. The knowledge of such grouping, a 

 perfect and quick recognition of the figures, I'ea' or 

 imaginary, which the stars make up amongst themselves, 

 in a word a knowledge of the constellations, is the first 

 essential for the direct observer. It was so from the 

 very beginning. The first astronomers necessarily ha<l 

 no telescopes, and equally of necessity the first £reat 

 astronomical enterprise was the dividing out of the 

 heavens into constellations, the ascribing certain 

 imaginary figures to particul.ir groups of stars, and the 

 bestowal of names upon individual stars themselves 



The same necessity makes itself felt in every branch 

 of science. Before any progress can be made the objects 

 recognised in that science must be named. Until they 

 are named they are undistinguished and undistinguish- 

 able. So far as we are concerned they remain without 

 properties, one might almost say without existence ; once 

 named, a knowledge of their properties and peculiari- 

 ties begins and a whole new field of research is opened 

 out. 



And even without this further knowledge, how great 

 an interest is given to any object by the fact that wo 

 know its name. Take some town children out into the 

 country, and set them to gather wild flowers, how in- 

 stantly they ask their names, and how much (heir 

 beauty is increased in their sight when those names are 

 taught them. And so to-day we are continually hearing 

 the complaint of Carlyle rejjeated : 



" Why did not somebody toacli me the constelhiUons, and make 



lue at home in the starry heavens, wliii.-h are always overhead and 



wliich I don't half know t<j this day-'" 



So the work of learning the stai-s, though it may in- 

 volve some self-denial, and brings no reward in the shape 

 of " magnificent spectacles," has a chanii of its own. 

 The silent watchers from heaven soon become each one 

 a familiar friend, and to any imaginative mind the sense 

 that he is treading the same path as that traversed by 

 the first students of Nature will have a strange charm. 

 With the " Poet of the Breakfast Table " he will feel 

 himself linked to the great minds of the deep uu 

 measured past. 



" I am as old as I'">;yiit to myself; 



" Krother to them tliat squared the I'yr.imids. 



" liy the same stars I wat<-li." 



However often, therefore, the work of teaching thi 

 constellations may have been undertaken, it forms an 

 inseparable portion of my present task. 



To us in England, with our high northern latitude, the 

 stars which never set arc the first the study of which 

 we should undertake. They are always present, they 

 cover more than one-third of the entire sky visible to 

 us at any moment. They include many conspicuous 

 stars, and form an admirable guide to the constellations 

 beyond the circumpolar region. Constantly revolving 

 round the pole they form, as it were, a magnificent 

 dial plate, marking at the same time the jsrogress both 

 of the night and of the year. 



