Mr. J. N. Lockyer on Recent Discoveries in Solar Physics. 149 



prominence-image coincident with the slit, we shall see it as we see 

 the slit, and the wider we open the slit the more of the j>roininence 

 shall we see. We may use either the red, or yellow, or green light 

 of hydrogen for the purpose of thus seeing the shape and details of 

 the prominences ; how far the slit may be opened depends upon the 

 purity of the sky at the time. I have been perfectly enchanted with 

 the sight which my spectroscope has revealed to me. The solar and 

 atmospheric spectra being hidden, and the image of the wide slit and 

 the part of the prominence under observation alone being visible, the 

 telescope or slit is moved slowly, and the strange shadow-forms flit 

 past and are seen as they are seen in eclipses. Here one is reminded, 

 by the fleecy, infinitely delicate cloud-films, of an English hedge-row 

 with luxuriant elms ; here of a densely intertwined tropical forest, 

 the intimately interwoven branches threading in all directions, the 

 prominences generally expanding as they mount upwards, and chan- 

 ging slowly, indeed almost imperceptibly. 



It does not at all follow that the largest prominences are those in 

 which theintensest action or the most rapid change is going on — the 

 action as visible to us being generally confined to the regions just in 

 or above the chromosphere, the changes arising from violent uprush 

 or rapid dissipation, the uprush and dissipation representing the birth 

 and death of a prominence. As a rule, the attachment to the chromo- 

 sphere is narrow and is not often single ; higher up, the stems, so to 

 speak, intertwine, and the prominence expands and soars upward 

 until it is lost in delicate filaments, which are carried away in float- 

 ing masses. 



Since last October, up to the time of trying the method of using 

 the open slit, I had obtained evidence of considerable changes in the 

 prominences from day to day. With the open slit it is at once evi- 

 dent that changes on the small scale are continually going on ; but 

 it was only on the 14th of March that I observed any change at all 

 comparable in magnitude and rapidity to those already recorded by 

 M. Janssen. 



About 9 h 45 m on that day, with the slit lying nearly along the 

 sun's edge instead of across it as usual, I observed a fine dense pro- 

 minence near the sun's equator, on the eastern limb, with signs of 

 intense action going on. At 10 h 50 m , when the action was slacken- 

 ing, I opened the slit and saw at once that the dense appearance had 

 all disappeared and cloud-like filaments had taken its place. The 

 first sketch, now exhibited, embracing an irregular prominence with 

 a long perfectly straight one, was finished at 1 l h 5 m , the height of 

 the prominence being 1' 5", or about 27,000 miles. I left the ob- 

 servatory for a few minutes, and on returning at ll h 15 m I was 

 astonished to find that the straight part of the prominence had en- 

 tirely disappeared ; not even the slightest rack appeared in its 

 place. Whether it was entirely dissipated, or whether parts of it had 

 been wafted towards the other part, I do not know, although I 

 think the latter explanation the more probable one, as the other part 

 had increased. 



So much, then, for the chromosphere and the prominences, which 



