Report on the Solar Eclipse .Expedition to Viziadruq. 37 



THE CHIEF RESULTS BEARING ON SOLAR THEORY. 

 1. The Spectrum of the Chromosphere. 



Considerable time must elapse before tlie complete discussion of 

 the numerous photographs taken in the prismatic cameras can be 

 completed. I therefore give here only some general results which 

 can be gathered by a preliminary inspection of them. 



I first deal with the determination of the heights of the various 

 absorbing vapours so far as they can be gathered from the photo- 

 graphs, which, of course, only record for us the brightest lower 

 portions of the different arcs, and not their complete extension. 



The following table shows the results obtained in the case of 

 some of the most typical lines: 



A very noticeable feature of the chrornospheric spectra, which the 

 photographs enable us to investigate at different elevations, is the 

 difference in the behaviour of the gaseous and metallic lines. In the 

 spectrum taken very near the moment of second contact, representing 

 that of the lower strata with the spectra of higher ones superposed, 

 the metallic arcs are relatively short and very bright, while in later 

 photographs, representing the spectra of successively higher strata 

 free from admixture with lower ones, the metallic arcs are relatively 

 feeble. This is also indicated in another way by the varying effects 

 seen over the tops of lunar mountains and through indentations in 

 the moon's limb. 



Some of the Jines are seen to be relatively much brighter in the 



