ST ELL All E 1 'OL UTION. 



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the interposition of the moon at a total eclipse. But methods have been 

 devised by which they can be observed or photographed on any clear 

 day through the agency of a modified form of spectroscope. The prom- 

 inences are constantly changing in form, sometimes slowly, as in the 

 case of this group (Fig. 10), a photograph of which, taken at the eclipse 

 of May 28, 1900, by the Astronomer Eoyal of England in Spain, is 

 shown for comparison with the photograph taken about two hours 

 earlier by the Yerkes Observatory party in North Carolina. Here the 



Fig. 10. 

 Cloud-like Prominexces photographed at the Eclipse of May 28, 1900. a, by 

 Yerkes Observatory' Party' at Wadesboro, N. C. 6, by Astronomer Royal of England 

 AT Ovar, Portugal, two holtrs later. (The bright cross on the right of this picture 

 is due to a defect in the original photograph.) 



change in the form of the mass of gas which constitutes the prominence, 

 is comparatively small, but that violent forces are sometimes at work 

 may be illustrated by photographs of an eruptive prominence taken at 

 the Kenwood Observatory in 1895 (Fig. 11). At the moment 

 when the first photograph was made the prominence had at- 

 tained a height of 160,000 miles and was rising rapidly. Eighteen 

 minutes later another picture was taken; during the interval 

 the prominence had been going upward at the rate of six thousand miles 

 a minute, and when the exposure was made it had reached an elevation 

 of 280,000 miles. When looked for a few minutes later it had com- 

 pletely disappeared. 



The constitution of the chromosphere, the sea of flame some 10,000 

 miles deep from which the prominences arise, increases in complexity 

 as the surface of the solar disk is approached. In its upper part only 

 the vapor of calcium and the light gases, hydrogen and helium, are 

 found. But in proceeding downward the vapors of magnesium, sodium, 

 iron, chromium, and last of all, carbon, are successively encountered. 

 At this part of the solar atmosphere the dark lines of the solar spectrum 

 take their rise through the effect of absorption. 



Time does not permit a detailed description of the phenomena of 



