418 Spectroscopic Observations of the Sun. [Apr. 29, 



On the following side of the spot, at about 10 a.m., I observed that the 

 F line had disappeared ; at the point of disappearance there appeared to 

 be an elongated brilliantly illuminated lozenge lying across it at right 

 angles, as if the spectroscope were analyzing the light proceeding from a 

 cyclone of hydrogen on the sun itself, but so near the limb that the 

 rotatory motion could be detected. 



The next observations I have to lay before the Royal Society were made 

 on the 27th inst. Careful observations on the 25th and 26th revealed 

 nothing remarkable except that the chromosphere was unusually uni- 

 form. 



On the 27th a fine spot with a long train of smaller ones and faculse was 

 well on the disk. The photosphere in advance of the spot, and the large 

 spot itself, showed no alteration from the usual appearance of the hydrogen- 

 lines ; but in the tails of the spot the case was widely different. 



The F line, at which I worked generally, as the changes of wave-length 

 are better seen, was as -irregular as on the former occasions. 



I. It often stopped short of one of the small spots, swelling out prior to 

 disappearance. 



II. It was invisible in a facula between two small spots. 



III. It was changed into a bright line, and widened out on both sides 

 two or three times in the very small spots. 



IV. Once I observed it to become bright near a spot, and to expand 

 over it on both sides. 



V. Very many times near a spot it widened out, sometimes consider- 

 ably, on the less refrangible side. 



VI. Once it extended as a bright line without any thickening over a 



small spot. 

 VII. Once it put on this appearance : 



VIII. I observed in it all gradations of darkness. 



IX. When the bright and dark lines were alongside, the latter was 

 always the less refrangible. 



The Society then adjourned over Ascension Day to Thursday, May 13. 



