132 Mr. J. N. Lockyer on Observations of the Sun. [Nov. 26, 



persive powers, gave an account of the delays which had impeded the 

 construction of a larger one (the funds for which were supplied by the 

 Government- Grant Committee early in 1867), in order that the coinci- 

 dence in time between his results and those obtained by the Indian ob- 

 servers might not be misinterpreted. 



Details are given of the observations made by the new instrument, which 

 was received incomplete on the 16th of October. These observations in- 

 clude the discovery, and exact determination of the lines, of the prominence- 

 spectrum on the 20th of October, and of the fact that the prominences are 

 merely local aggregations of a gaseous medium which entirely envelopes 

 the sun. The term Chromosphere is suggested for this envelope, in order 

 to distinguish it from the cool absorbing atmosphere on the one hand, and 

 from the white light-giving photosphere on the other. The possibility of 

 variations in the thickness of this envelope is suggested, and the pheno- 

 mena presented by the star in Corona are referred to. 



It is stated that, under proper instrumental and atmospheric conditions, 

 the spectrum of the chromosphere is always visible in every part of the 

 sun's periphery ; its height, and the dimensions and shapes of several pro- 

 minences, observed at different times, are given in the paper. One promi- 

 nence, 3' high, w 7 as observed on the 20th October. 



Two of the lines correspond with Fraunhofer's C and F ; another lies 

 8° or 9° (of KirchhofF's scale) from D towards E. There is another bright 

 line, which occasionally makes its appearance near C, but slightly less re- 

 frangible than that line. It is remarked that the line near D has no cor- 

 responding line ordinarily visible in the solar spectrum. The author has 

 been led by his observations to ascribe great variation of brilliancy to the 

 lines. On the 5th of November a prominence was observed in which the 

 action was evidently very intense ; and on this occasion the light and colour 

 of the line at F were most vivid. This was not observed all along the line 

 visible in the field of view of the instrument, but only at certain parts of 

 the line which appeared to widen out. 



The author points out that the line F invariably expands (that the band 

 of light gets wider and wider) as the sun is approached, and that the C 

 line and the D line do not ; and he enlarges upon the importance of this fact, 

 taken in connexion with the researches of Pliicker, Hittorf, and Frankland 

 on the spectrum of hydrogen — stating at the same time that he is engaged 

 in researches on gaseous spectra which, it is possible, will enable us to de- 

 termine the temperature and pressure at the surfaces of the chromosphere, 

 and to give a full explanation of the various colours of the prominences 

 which have been observed at different times. 



The paper also refers to certain bright regions in the solar spectrum 

 itself. 



Evidence is adduced to show that possibly a chromosphere is, under 

 certain conditions, a regular part of star-economy ; and the outburst of the 

 star in Corona is especially dwelt upon. 



