ME. J. N. LOCKYER ON SPECTROSCOPIC OBSERVATIONS OF THE SUN. 431 
also loses its thickness as it approaches the boundary of the spectrum. The amount of 
widening at the base is subject to variation. 
In the spectrum of the chromosphere this widening at the base is not generally ob- 
served either in the line at C or in that near D. 
None of the lines stop sharply ; they all fade out as the limit of the envelope is ap- 
proached. 
On certain Bright Regions in the Solar Spectrum. 
From the commencement of my observations with the new instrument my attention 
has been drawn to certain bright regions in the ordinary spectrum ; but it was not till 
the 8th of November, 1868, that I succeeded in observing a definite bright band ex- 
tending for a certain distance on the sun near the limb. 
I should state that I have observed this behaviour in the F band on either side of 
Fraunhofer’s dark lineF, and in the C line, when the prominence, as I have imagined, 
has extended from the limb over the earth’s side of the sun. 
The position of the bright band observed on the 8th of November is near C, but slightly 
less refrangible, not far from the place in the scale occupied by the last discovered red 
line, the position of which as yet has not been micrometrically determined. 
Other regions to which my attention has been particularly drawn from the first, 
although up to the present time I have obtained no results, lie, one between the b lines, 
another between b and F, another less refrangible than B, one near D, and another near G. 
It is quite possible that these bright regions, the light of which is variable, may be 
due to faculce ; this conclusion is strengthened by the fact that diligent sweeping within 
the limb has not revealed the bright lines of the chromosphere spectrum. If this be so, 
the faculse are not the prominences, although they may be possibly connected with them. 
On the nature of the Chromosphere and Prominences. 
It has already been concluded by M. Janssen, from the coincidence of two of the 
bright lines with C and F, that the prominences are composed of hydrogen. 
So far as our present knowledge goes, however, this does not dispose of the other two 
bright lines, the positions of which have been determined by myself : I allude to the 
lines near D and near C. 
At the present moment I am engaged on a series of experiments on gaseous spectra, 
which I hope will afford additional information on these points ; in the interim, on the 
assumption that the chromosphere and prominences are wholly, or in part, composed of 
hydrogen, several considerations which appear to me of great importance may be touched 
upon. 
These considerations are based upon the experiments of MM. Pluckek and Hittorf* 
on the one hand, and of Professor Frankland on the other f. In MM. Pluceer and 
Hittorf’s paper, entitled “On the Spectra of Ignited Gases and Vapours, with especial 
regard to the different Spectra of the same elementary gaseous substance,” these inv.es.ti- 
* Philosophical Transactions, vol. civ. (1865) Part I. pp. 1-29. f Proe. Roy. Ins. vol. v. p. 419. 
