116 



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



cannot say ; perhaps half a minute. Soon the cloud hurried over ; follow- 

 ing the moon's direction, and therefore revealing first the upper limb, with 

 its scintillating corona, and then the lower. 



A prominence seen and aimed at. — Instantly I marked a prominence 

 near the needle-point, an object so conspicuous that I felt there was no 

 need to take any precautions to secure identification. It was a long 

 finger-like projection from the (real) lower left-hand portion of the circum- 

 ference. A rapid turn of the declination-screw covered it with the needle- 

 point, and in another instant I was at the spectroscope. A single glance and 

 the problem was solved. 



Its Spectrum, — Three vivid lines, red, orange, blue ; no 



OTHERS, AND NO TRACE OF A CONTINUOUS SPECTRUM. 



35. Measurement of lines undertaken, with partial success. 

 When I say the problem was solved, I am of course using language 

 suited only to the excitement of the moment ! It was still very far from 

 solved, and I lost no time in applying myself to measurement. And here 

 I hesitate ; for the measurement was not effected with anything like the 

 ease and certainty which ought to have been exhibited. Much may be 

 attributed to haste and unsteadiness of hand, still more to the natural 

 difficulty of measuring intermittent glimpses ; but I am bound to confess 

 that these causes were supplemented by a failure less excusable. I have 

 no idea how those five minutes passed so quickly ! Clouds were evidently 

 passing continually ; for the lines were only visible at intervals — not for one- 

 half the time, certainly — and not always bright ; but still I ought to have 

 measured them all. My failure was in insufficient illuminating power ; 

 but why, I cannot tell. I never experienced any difficulty of the kind with 

 the nebulae, which required that I should flash in light suddenly over and 

 over again. I had found the hand-lamp the surest way ; but it failed me 

 here in great measure. The red line must have been less vivid than the 

 orange ; for after a short attempt to measure it, I passed on to secure the 

 latter. 



Two lines measured. — In this I succeeded to my satisfaction, and ac- 

 cordingly tried for the blue line. Here I was not so successful. The 

 glimpses of light were rarer and feebler, the line itself growing shorter and, 

 what remained of it, further from the cross. I did, however, place the 

 cross wires in a position certainly very near the true one, and got a reading 

 before the reillumination of the field told me that the sun had reappeared on 

 the other limb. These readings were called out, as those of the solar lines 

 had been, to my recorder ; and it was only afterwards that I compared them. 



I need not dwell on the feelings of distress and disappointment which 

 I experienced on realizing the fact that the long-anticipated opportunity was 

 gone, and, as it seemed to me then, wasted. I seemed to have failed 

 entirely. Almost mechanically I directed the telescope to the bright limb, 

 to verify the readings of the solar lines ; and in so doing my interest was 



