154 THE INDIAN ECLIPSE, 1898. 



materials, white chalk on purplish-blue paper, is an admirable 

 one. For practising, brown paper serves very well, if blue paper 

 is scarce. 



4. It is important always to practise on the same scale as the 

 final sketch is to be made. It has been found that a half-crown 

 (1J inch in diameter) is a very convenient size for the black 

 body of the moon, and this may be always at hand. A circle, 

 being drawn round the half-crown, is bisected vertically and 

 horizontally, and the diameters are produced across the paper. 

 The sketcher has a plumb-line (a bunch of keys at the end of 

 a string will do), with which he divides his model corona 

 vertically as he looks up at it ; and he guesses at the correspond- 

 ing horizontal division. His quadrant thus fixed, he proceeds 

 to sketch it. When the time is called the leader redraws all 

 four quadrants in one combined sketch ; and by comparison with 

 the original the habitual faults of the sketchers are detected, and 

 in the course of a few practices will disappear. 



5. The position of any planet or high-magnitude star very near 

 the sun at the time of eclipse should be accurately ascertained, 

 and its distance measured in terms of the moon's diameter 

 (taken as half a degree), as these facts when made familiar to 

 the whole party will check the supposed direction and extent 

 of any long streamers of the corona. 



6. On eclipse day the sketchers should avoid fatiguing their 

 eyes by too much observation of the preceding partial eclipse, 

 and should rest the eyes for the last five minutes, before 

 totality, absolutely. It would be well to close them for the last 

 minute, and open them by a signal at totality. Attention 

 should be paid to the extreme extent and to the colour of the 

 corona at the moment of beginning to draw, when the eye is 

 at its freshest, and consequently is better able to observe these 

 points than after gazing at the very bright inner parts of the 

 corona. 



H. KEATLEY MOORE. 



SPECTROSCOPIC EESEARCH AT FUTURE ECLIPSES.* 



AMONG the numerous questions which present themselves 

 for solution at future eclipses perhaps the most vital is that 

 relating to the distribution of the gases in the Flash spectrum 

 layer. Although the entire thickness of the stratum subtends 

 an angle of but one or two seconds of arc, and consequently 

 appears to -us at the moments of second and third contact as an 

 extremely fine thread of light, yet it will have to be examined 

 in much greater detail than heretofore if an advance is to be 

 made in our knowledge of the relation which its bright-line 

 spectrum bears to the dark-line Fraiinhofer spectrum. The 



* By J. Evershed, F.R.A.S, 



