﻿144 Royal Society. 



Supplementary Note. Received Nov. 5, 1868. 



Sir, — I have the honour, in continuation of my letter of the 

 20th ultimo, to inform you that I have this morning obtained evi- 

 dence that the solar prominences are merely the expansion, in certain 

 regions, of an envelope which surrounds the sun on all sides. I 

 may add that other facts observed seem to point out that we may 

 shortly be in a position to determine the temperature of these cir- 

 cumsolar regions. 



J. Norman Lockyer. 



" Spectroscopic Observations of the Sun." — No. II. By J. Nor- 

 man Lockyer, F.R.A.S. (This paper was concluded on November 26). 



The author, after referring to his ineffectual attempts since 1866 

 to observe the spectrum of the prominences with an instrument of 

 small dispersive 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 coincidence in time between his results and those 

 obtained by the Indian observers 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 ob- 

 servations include 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 phenomena 

 presented by the star in Corona are referred to. 



It is stated that, under proper instrumental and atmospheric con- 

 ditions, 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 prominences, observed at different times, are given 

 in the paper. One prominence, 3' high, was 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 an- 

 other bright line, which occasionally makes its appearance near C, 

 but slightly less refrangible than that line. It is remarked that the 

 line near D has no corresponding 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 



