74 o THE POPULAR SCIENCE MONTHLY. 



in space. But science asks not only for a true cause, but a sufficient 

 cause. There must be enough of this matter to do the work assigned 

 to it. At present we have no evidence that the total existing quantity 

 of such fine material is very large. It is to be hoped that through the 

 collection and examination of meteoric dust we must soon learn some- 

 thing about the amount which our earth receives. Until that shall be 

 learned, we can reason only in general terms. So much matter coming 

 into our atmosphere as these several hypotheses require would without 

 doubt make its presence known to us in the appearance of our sunset 

 skies, and in a far greater deposit of meteoric dust than has ever yet 

 been proved. 



A meteoroid origin has been assigned to the light of the solar corona. 

 It is not unreasonable to suppose that the amount of the meteoroid 

 matter should increase toward the sun, and the illumination of such 

 matter would be much greater near the solar surface. But it is diffi- 

 cult to explain upon such an hypothesis the radical structure, the rifts, 

 and the shape of the curved lines that are marked features of the co- 

 rona. These seem to be inconsistent with any conceivable arrange- 

 ment of meteoroids in the vicinity of the sun. If the meteoroids are 

 arranged at random, there should be a uniform shading away of light 

 as we go from the sun. If the meteoroids are in streams along com- 

 etary orbits, all lines bounding the light and shade in the coronal light 

 should evidently be approximately projections of conic sections, of 

 which the sun's center is the focus. There are curved lines in abun- 

 dance in coronal light, but as figured by observers and in the photo- 

 graphs they seem to be entirely unlike any projections of conic sections. 

 Only by a violent treatment of the observations can the curves be made 

 to represent such projections. They look more as though they were 

 due to forces at the sun's surface than at its center. If those compli- 

 cated lines have any meteoroid origin (which seems very unlikely) they 

 suggest rather the phenomena of comets' tails than meteoroid streams 

 or sporadic meteors. The hypothesis that the long rays of light which 

 sometimes have been seen to extend several degrees from the sun at 

 the time of the solar eclipse are meteor-streams seen edgewise seems 

 possibly true but not at all probable. 



The observed life of the meteor is only a second, or at most a few 

 seconds, except when a large one sends down stones to remain with us. 

 What can we learn about its history and origin ? Near the beginning 

 of this century, when small meteors were looked on as some form of 

 electricity, the meteorites were very generally regarded as having 

 been thrown out from the lunar volcanoes. But as the conviction 

 gained place that the meteorites moved not about the earth but about 

 the sun, it was seen that the lunar volcanoes must have been very ac- 

 tive to have sent out such an enormous number of stones as are needed 

 in order that we should so frequently encounter them. When it was 

 further considered that there is no proof that lunar volcanoes are now 



