GENElvAL DISCUSSION OF SPECTROSCOPIC RESULTS. 
477 
majority of the bright lines of the flash spectrum, excluding hydrogen and helium 
lines, coincide with dark lines of intensity not less than 3. 
Most of the bright arcs of the flash spectrum- are well-defined narrow lines 
admitting of considerable accurac}^ in the measures, and the present determinations 
of wave-length indicate that the coincidence of the ])right lines with the dark lines 
is exact within '05 tenth-metre for all the well-defined lines. 
As regards the relative intensities of the lines of any one element in the flash and 
Fraunhofer spectra, my previous results require modification and extension as 
follows :— 
The relative intensities of isolated lines of an element in the flash spectrum are in 
general, hut not exact, agreement with those of the same element in the solar 
spectrum, and those lines which are exceptionally strong in the flash are in most 
cases lines which are enhanced in the spark specti’um of the element. 
All of the more j^rominent enhanced lines of iron and titanium are found to 
coincide with strong lines in the flash, hut owing to the comjjound nature of some of 
the lines, it is not certain that all of these have aljiiormal intensities in the flash. 
There is no evidence of differences in the relative intensities of the lines of an 
element in the higher or lower regions of the flash layer, and the enhanced lines 
appear to predominate throughout the entire depth of the radiating stratum. 
The enhanced lines are equally prominent in the })olar regions and in low latitudes, 
and the flash spectrum generally is now found to be the same in all latitudes and 
shows no essential change after an interval of five years. 
An explanation of the almormal intensities of the enhanced lines in the flash 
spectrum is now ofiered which depends on the assumption of a continuous circulation 
of the solar gases in a radial direction; the highly heated ascending gases giving 
the predominant features to the flash spectrum, wliilst the cooler more diffused gases, 
slowly subsiding, determine the character of the absorption spectrum. 
The final conclusion is that the flash spectrum represents the emission of both 
ascending and descending gases, whilst the Fraunhofer spectrum represents the 
absorption of the descending gases only. 
Tables of Wave-length and Intensity. 
In Table I. the wave-lengths and intensities of the biiglit lines in the three 
measured spectra (Nos. 9, 11, and 13) are entered in the first six columns; the 8th 
and 9th columns give the “adopted” wave-lengths and intensities, be., the most 
probable values deduced from all the measures, and these are compared in the two 
following columns with Rowland’s values of the neai'est absorption lines. The 
origins, mostly from Rowland, are given in the last column. A vertical line 
* The wave-lengths of the helium lines from Runge and Paschen are also given in the renth column. 
They are placed within Ijrackets to distinguish them from the absorption lines. 
