CHAPTER X. 



PRELIMINARY SEARCH AFTER EXPLANATIONS. 



1. The Widening of Lines. 



IN the preceding chapter I have attempted to give a rapid and 

 general sketch of the world of wonders in which we had been 

 landed by the new method of solar observation. It became 

 obviously of first importance to attempt to get some explanation 

 of those phenomena, at all events, which .were considered ab- 

 normal because they were new. It was also obvious that if 

 laboratory experiments could not throw light upon such ap- 

 pearances, for instance, as the widening of the lines in spots and 

 at the base of some of the chromospheric lines, we should be in 

 an impasse. 



With a view to get new facts, and among them some bearing 

 upon the widening of spectral lines, Dr. Frankland and I com- 

 menced, in 1869, a series of researches on gaseous spectra. 1 

 As the result of this inquiry, which extended over a period of 

 three years, we came to the conclusion that laboratory ex- 

 periments could help us in fact, Dr. Frankland had already 

 succeeded in giving great width to the hydrogen lines, 2 and that 



1 Proc. Roy. Soc. vol. xvii. p. 288. 



2 These observations were never published, but in a paper communicated to 

 the Royal Society in 1868, Dr. Frankland described a series of experiments on 

 the combustion of jets of hydrogen and carbonic oxide in oxygen under a pressure 

 gradually increasing to twenty atmospheres. In the case of hydrogen he found 

 that under a pressure of two atmospheres " the previously feeble luminosity is 



