May 1, 1900.] 



KNOWLEDGE. 



106 



to run before this country will be favoured with the 

 next.* Yet the ease of modern travel brings the pheuo- 

 meuon within the reach of so many that it may be well 

 worth while to glance at the various kinds of work 

 which can be undertaken by " astronomers without 

 telescopes, ' especiallv as we are now within a monUi of 

 the time of an eclipse the track of which may be reat'iicd 

 bv a three davs' journev from our own shores. 



It should be borne in mind by all who ai'c favoured 

 with a good view of so rare a phenomenon as that of a 

 tot^al eclipse of the sun, that there is a kind of moral 

 obligation upon them not to let the opportunity pass 

 entirely without profit, " The giddy pleasure of the 

 eye " is no excuse for selfishness. Each one should do 

 something, make some record, which may hereafter be 

 of service to othei^s in the solution of some of the 

 problems which are eclipse presents. Wc owe an in- 

 estimable debt to those who preceded us who did leave 

 such records, and we can only repay that debt, by in 

 like manner, doing our best to leave material as useful 

 for the benefit of tliose who shall in their turn succeed 

 to us. 



First of all, the most obvious work for anyone to 

 undertake, who watches a total eclipse without a 

 t-elescope, is to draw the corona. This may seem a very 

 trivial matter, and when the strange discrepancies 

 between different sketches are noted, a very useless thing 

 to attempt, especiallv in view of the entrance of jihoto- 

 graphy into the field. But it is not so. The chief fact 

 that we have as yet established with regard to the corona 

 is that it varies in form and charactei- with the sun-spot 

 cycle, and this fact, though supported by the photo- 

 graphs, was demonstrated by the comparison of draw- 

 ings. Then again the careful examination of drawings 

 has shown them to be far more trustworthy than a 

 cvirsorv look would suggest. The wide differences be- 

 tween different sketches has often been due to the 

 sketchers choosing different sections of the corona; one 

 choosing the brightest inner corona, another the fainter 

 and more irregular contour, a third the faintest exten- 

 sions. The results have really not been contradictoi-y 

 but rather supplemental of each other. Xor has photo- 

 graphy entirely superseded the work of the .sketcher 

 even yet. The coronal streamers, often shown in draw- 

 ings, were photographed in the eclipse of 1898 for the 

 first time. The previous failure of photographs to 

 record them had occasioned their very existence to be 

 denied in some quarters, and had cast unmerited sus- 

 picion upon the drawings which delineated them. 



The work of drawing the corona is, however, not one 

 to be done off-hand. The intending artist should be one 

 who has already acquired skill and quickness in 

 draughtmanship. The time of an eclipse is terribly 

 short — it will scarcely exceed one minute at most stations 

 on ^lay 28th next — and the object is bizarre and un- 

 familiar. There should be frequent practices before- 

 hand, either upon drawings of the corona, held at a 

 distance of 107 times the diameter of the eclipsing 

 moon, or, perhaps better, upon little wisps of cirrus 

 cloud. But in any case the time from the first sight 

 of the object to the completion of the sketch must be 

 rigidly confined to the time of the expected duration of 

 totality. Quickness to see and record is the first essential 

 for coronal sketching. 



The next point to be noted is the need for fiducial 

 lines by which to orientate the drawing. This may be 



* See diagram at page 119 for Eclipse as visible in England. 



done by jDroviding a ]ihuiib-lino right across the line of 

 sight. If the weight at the end of the plumb-line 

 dips into water, it will serve to steady it against vibration 

 with the w'ind. Mercury, distant about '2\° from the 

 sun, in tha forthconiing eclij)se, will supply a further 

 and most excellent reference point l.tolli for direction 

 and distance. 



If sevei-al sketchers can combine they should portion 

 out the corona between them before the eclipse begins, 

 the vertical line being adopted as one of the dividing 

 lines, and if four workers arc present, a line parallel to 

 the horizon might be anothei", thus giving each observer 

 a quadrant. A fifth observer might make a i-apid out- 

 line of the entire corona as a basis for combining the 

 four quadrantal sketches. In so short an eclipse it 

 would be a di.stinct advantage to be able to confine tl.e 

 attention to a portion only of the phenomenon. 



The sketchers should be careful to indicate as precisely 

 as possible the positions of any red pi'oiiiinences, as 

 these can be verified either from photographs or from 

 observations with the spectroscoj)e. Distances from 

 the limb of the dark moon should be carefully estimated 

 in terms of its diameter. 



In some former eclipses, notably in 1873, the brightest 

 inner corona has been screened off by means of a black 

 disc, so as to leave the eye more sensitive for the de- 

 tection of faint coronal streamers. This is not recom- 

 mended as it is a troublesome and very doubtfully 

 useful device. But all intending sketchers should be 

 most careful to avoid dazzling their eyes during the 

 coming on of the partial phase, and should rest them as 

 much as possible shortly before totality. 



White chalk on purplish blue paper is an admirable 

 material for representing the corona. Notes as to any 

 colour or colours perceived in the corona should be 

 made. 



Quite another chuss of work may be taken up by those 

 who have keen eyesight, in the search for stars. The 

 sun is ill a specially ^ch pox-tion of the heavens, during 

 the eclipse of May 28th, near Aldebaran and the 

 Pleiades, and a great number of stars' should conse- 

 quently be seen. Orion, Sirius, Procyon, Castor and 

 Pollux are all well placed. Mercury is only 2^° distant 

 from the sun below it; Venus practically at her greatest 

 brilliancy will be nearly in the zenith. To note which 

 stars are seen, when they are first glimpsed, and when 

 lost, would be of some value as a register of the clearness 

 of the sky, and of the brightness of the eclipse, as well 

 as for comparison with the records of old eclipses wherein 

 the appearance of stars was observed. 



The zodiacal light should be looked for, for though 

 the chances against seeing it are very great, a single 

 clear record of its a])pearance during an eclipse would be 

 of the utmost value, and might decide at once whether 

 its axis coincided with the ecliptic or with the solar 

 equator. The ecliptic at the time of totality is only 

 inclined a few degrees to the vertical. 



The observations of the "shadow-bands" is one of 

 some interest, and as it only requires a white surface and 

 a few light rods, a large number of observers should bo 

 forthcoming. 



IC must be remembered that the bands are usually 

 very faint, and have to be definitely looked for. A white 

 surface must be prepared to receive them ; either a 

 white sheet, which may be fastened down to the ground, 

 or set up vertically on an upright frame, or a whitened 

 wall. The surface should be marked with two straight 

 black lines, one foot apart, that the intervals apart of 



