850 



Mr. J. N. Lockyer on Sjjcctroscojyic 



[Mar. 18, 



red corpuscle of all vertebrata is, in its natural state, structureless. AVhen 

 living, no distinction of parts can be recognized ; and the existence of a 

 nucleus in the red corpuscles of ovipara is due to changes after death, or 

 removal from the vessels. 



I cannot conclude this paper without acknowledging the great help I 

 have received in this investigation from Mr. Howard Marsh, Demonstrator 

 of Microscopical Anatomy at St. Bartholomew's Hospital. 



V. "Spectroscopic Observations of the Sun. — No. III." By J. 

 Norman Lockyer, F.R.A.S. Communicated by Dr. Frank- 

 land, F.R.S. Received March 4, 1869. 



Since my second paper under the above title was communicated to the 

 Royal Society, the weather has been unfavourable to observatory work to 

 an almost unprecedented degree ; and, as a consequence, the number of 

 observations I have been enabled to make during the last four months is very 

 much smaller than I had hoped it would be. 



Fortunatety, however, the time has not been wholly lost in consequence 

 of the weather ; for, by the kindness of Dr. Frankland, I have been able in 

 the interim to familiarize myself at the Royal College of Chemistry with 

 the spectra of gases and vapours under previously untried conditions, and, 

 in addition to the results already communicated to the Royal Society by 

 Dr. Frankland and myself, the experience I have gained at the College of 

 Chemistry has guided me greatly in my observations at the telescope. 



In my former paper it was stated that a diligent search after the known 

 third line of hydrogen in the spectrum of the chromosphere had not met 

 with success. When, however, Dr. Frankland and myself had determined 

 that the pressure in the chromosphere even was small, and that the widening 

 out of the hydrogen lines was due in the main, if not entirely, to pressure, 

 I determined to seek for it again under better atmospheric conditions ; and 

 I succeeded after some failures. The position of this third line is at 2796 

 of Kirchhoff's scale. It is generally excessively faint, and much more care 

 is required to see it than is necessary in the case of the other lines ; the 

 least haze in the sky puts it out altogether. 



Hence, then, with the exception of the bright yellow line, the observed 

 spectra of the prominences and of the chromosphere correspond exactly 

 with the spectrum of hydrogen under different conditions of pressure — a 

 fact not only important in itself, but as pointing to what may be hoped for 

 in the future. 



"With regard to the yellow line which Dr. Frankland and myself have 

 stated may possibly be due to the radiation of a great thickness of hydrogen, 

 it became a matter of importance to determine whether, like the red and 

 green lines (C & F), it could be seen extending on to the limb. I have not 

 observed this : it has always in my instrument appeared as a very fine sharp 

 line resting absolutely on the solar spectrum, and never encroaching on it. 



