386 THE POPULAR SCIENCE MONTHLY. 



" color-sphere," in allusion to the vivid redness of the stratum caused 

 by the predominance of hydrogen in these flames and clouds. 



Here and there masses of this hydrogen mixed with other sub- 

 stances rise to a great height, ascending far above the general level 

 into the coronal regions, where they float like clouds, or are torn to 

 pieces by contending currents. These cloud-masses are known as 

 solar " prominences," or " protuberances," a non-committal sort of ap- 

 pellation applied in 1842, when they first attracted any considerable 

 attention, and while it was a warmly-disputed question whether they 

 were solar, lunar, phenomena of our own atmosphere, or even mere 

 optical illusions. It is unfortunate that no more appropriate and 

 graphic name has yet been found for objects of such wonderful beauty 

 and interest. 



Until recently, the solar atmosphere could be seen only when the 

 sun itself was hidden by the moon, a few minutes in a century. Now, 

 however, the spectroscope has brought the chromosphere and the 

 prominences within the range of daily observation, so that they can 

 be studied with nearly the same facility as the spots and faeulse, and a 

 fresh field of great interest and importance is thus opened to science. 

 But the corona as yet defies the new method, and can be seen only 

 during the fleeting moments of a solar eclipse. 



It seems hardly possible that the ancients should have failed to no- 

 tice, even with the naked eye, in some one of the many eclipses on 

 record, the presence of blazing star-like objects around the edge of the 

 moon, but we find no mention of any thing of the kind, although the 

 corona is described as we see it now. On this ground some have sur- 

 mised that the sun has really undergone a change in modern times, and 

 that the chromosphere and prominences are a new development in the 

 solar history. But such mere negative evidence is altogether insuffi- 

 cient as a foundation for so important a conclusion. 



The earliest recorded observation of the prominences is probably 

 that of Vassenius, a Swedish astronomer, who, during the total eclipse 

 of 1733, noticed three or four small pinkish clouds, entirely detached 

 from the limb of the moon, and, as he supposed, floating in the lunar 

 atmosphere. At that time this was the most natural interpretation of 

 the appearance, since the fact that the moon is without atmosphere was 

 not yet ascertained. 



The Spanish admiral, Don Ulloa, in his account of the eclipse of 

 1778, describes a point of red light which made its appearance on the 

 western limb of the moon about a minute and a quarter before the 

 emergence of the sun. At first small and faint, it grew brighter and 

 brighter until extinguished by the returning sunlight. He supposed 

 that the phenomenon was caused by a hole or fissure in the body of 

 the moon ; but, with our present knowledge there can be no doubt 

 that it was simply a prominence gradually uncovered by her motion. 



The chromosphere seems to have been seen even earlier than the 



