THE 



AMER1CANJ0URNAL0FSCIENCE 



[FOURTH SERIES.] 



Art. XX Y. — On the Gaseous Constitution of the II. and K. 



lines of the Solar Spectrum, together with a discussion of 

 reversed gaseous lines ; by John Trowbridge. 



I described in this Journal of July, 1902 and of December, 

 1902 the discovery of reversed lines in the spectra of gases when 

 the latter are submitted to powerful disruptive discharges. In 

 the first article I spoke of the desirability of obtaining some 

 other material than glass for Geissler tubes in order to deter- 

 mine if any of the lines observed were due to the glass. In 

 this Journal, December, 1902, I described some preliminary 

 experiments with quartz tubes. 



In this paper 1 shall show that the continuous spectra 

 observed when glass tubes are employed are not due to incan- 

 descence of the glass walls : and also that the lines obtained by 

 me which coincide closely with the calcium lines at wave 

 lengths 3968 and 3933 — H.H. lines of the solar spectrum, are 

 not due to calcium, but are true gaseous lines. The great H. 

 H. lines therefore of the solar spectrum, although being a com- 

 posite spectrum of many lines, have a basis of gaseous lines. 

 This seems more than reasonable when we consider that the 

 solar protuberances are observed through the great H.H. lines, 

 and when we also take into consideration the rarified nature of 

 the gas and the improbability of a metallic vapor like that of 

 calcium being projected so far from the sun's limb. Moreover 

 I shall show that the reversed lines are due to a solarization 

 of which the Clayden effect is merely a special case. 



It was necessary in my work, to determine, in the first place, 

 to what degree metallic electrodes influence the spectra in 

 Geissler tubes of the length and bore which were employed by 

 me. When long and powerful sparks aiv produced in air, the 

 metallic lines due to the terminals disappear at a distance of 



Am. Jour. Sci. — Fourth Series, Vol. XV, No. 88. — April, 1908. 

 17 



