118 



Lieut. J. HerschePs Account of the [Nov. 19, 



what I have still to state was rather the result of subsequent reflection than 

 of actual cognizance at the time. I said that the prominence was situated 

 close to the needle-point. I estimate its position as at the east point, a 

 few degrees to the left of the lowest, of the sun's limb. Its form was that 

 of a projecting finger slightly curved to the southward, and its height 

 nearly 2'. The slit was at right angles to the hour-circle, and therefore 

 perpendicular to the sun's limb at this point. A vertical section (so to 

 speak) of the prominence was therefore admitted through the slit. It ap- 

 pears, then, that the length of the lines corresponded with the height of the 

 prominence, being limited (as in the case of the spectrum of the section of 

 the crescent) on the one hand (the left) by the advancing moon's limb 

 at the centre of the field, and on the other by the natural summit of the 

 prominence, or flame, as we are now entitled to call it. 



Spectrum of Corona not seen. — Beyond this summit the light of the 

 corona was free to enter ; it was also free to enter with that of the flame ; 

 but I saw the spectrum of the latter only. I thence conclude that the 

 spectrum of the corona was a faint solar one, — -a conclusion quite in ac- 

 cordance with the other characteristics of this phenomenon, such as the 

 radiated appearance and the evidence from polarity, indicating a central 

 source of light. With regard to the latter, it is clear that the light of the 

 corona is polarized in planes passing through the sun's centre (as the gist 

 of Lieut. Campbell's Report), and therefore that the corona shines mainly 

 by reflected light. At the same time it is possible that the absence of a 

 spectrum of the corona at this particular spot may have been accidental. 

 I have since heard that the corona was particularly feeble at this point. 

 I had no opportunity of studying the corona myself. After first catching 

 sight of the eclipse in the finder, I never left the spectroscope but once, 

 when a long interval of cloudiness sent me to the finder to make sure. I 

 then caught a few seconds' glimpse again, and remarked a red blot (I 

 recognized no shape) of a prominence at about the north point, or rather 

 to the west of it. 



41. Remarks on the ease with which the lines might be measured, and 

 suggestions for future observations. 



I have now a few remarks to add which may be of use to future ob- 

 servers, if not of any present value. It is difficult to say what might or 

 might not have been done but for the clouds ; but I am pretty certain 

 that (even labouring, as I was, under the difficulty of bad illumination) not 

 only might all three lines have been satisfactorily measured, but time 

 would have sufficed for further examination. The course which that 

 examination should take is a question which it is of the highest importance 

 for an observer to decide on previously. I believe I was right in using a 

 narrow slit to begin with, not anticipating such a totally dark field ; but I 

 should not do so again ; or if I did, with the object of getting exact mea- 

 sures of the three principal lines, I should be prepared to widen the slit 



