August 20, 1886.] 



SCIENCE. 



173 



evidently be projections of conic sections of which 

 the sun's centre is the focus. There are curved 

 lines in abundance in the coronal light, but, as 

 figured by observers and in the photographs, they 

 seem to be entirely unlike such projections of conic 

 sections. Only by a violent treatment of the obser- 

 vations can the curves be made to represent such 

 projections. They look as though they were due to 

 forces at the sun's surface ratlier than at his centre. 

 If those complicated lines have any meteoroid 

 origin (which seems very unlikely), they suggest 

 the phenomena of comets' tails rather than mete- 

 oroid 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 electrici- 

 ty, the meteorites were very generally regarded 

 as having been thrown out from the lunar volca- 

 noes. 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 active to have sent out such an 

 enormous number of stones as are needed in order 

 that v/e should so frequently encounter them. 

 When it was further considered that there is no 

 proof that lunar volcanoes are now active, and 

 that when they were active they were more likely 

 to have been open seas of lava, not well fitted to 

 shoot out such masses, the idea of the lunar origin 

 of the meteorites gradually lost ground. 



But the unity of meteorites with shooting-stars, 

 if true, increases a hundred fold the difficulty, 

 and would require that the comets have the same 

 origin with the meteorites. No one claims that 

 the comets came from the moon. 



That the meteorites came from the earth's vol- 

 canoes is still held by some men of science, par- 

 ticularly by the distinguished astronomer-royal for 

 Ii'eland. The difficulties of the hypothesis are, how- 

 ever, exceedingly great. In the first place, the mete- 

 orites are not like terrestrial rocks. Some minerals 

 in them are like minerals in the rocks. Some irons 

 are like the Greenland terrestrial irons. But no 

 rock in the earth has yet been found that would 

 be mistaken for a meteorite of any one of the two 

 or three hundred known stone-falls. The meteor- 

 ites resemble the deep terrestrial rocks in some 

 particulars, it is true, but the two are also thor- 

 oughly unlike. 



The terrestrial volcanoes must also have been 

 wonderfully active to have sent out such a multi- 

 tude of meteorites as will explain the number of 

 stone-falls which we know, and which we have 

 good reason to believe have occurred. The volca- 

 noes must also have been wonderfully potent. 

 The meteorites come to us with planetary veloci- 

 ties. In traversing the thin upper air, they are 

 burned and broken by the resisting medium. 

 Long before they have gone through the tenth 

 part of the atmosphei'e the meteorites usually are 

 arrested and fall to the ground. If these bodies 

 were sent out from the earth's volcanoes, they left 

 the upper air with the same velocity with which 

 they now return to it. What energy must have 

 been given to the meteorite before it left the vol- 

 cano, to make it traverse the whole of our atmos- 

 phere and go away from the earth with a planet- 

 ary velocity. Is it reasonable to believe that 

 volcanoes were ever so potent, or that the meteor- 

 ites would have survived such a journey ? 



No one claims that the meteors of the star- 

 showers, or their accompanying comets, came 

 from the earth's volcanoes. To ascribe a terres- 

 trial origin to meteorites is, then, to deny the 

 relationship of the shooting-star and the stone- 

 meteor. Every reason for their likeness is an 

 argument against the terrestrial origin of the 

 stones. To suppose that the meteors came from 

 any planets that have atmospheres, involves diffi.- 

 culties not unlike to, and equally serious with, 

 those involved in the theory of a terrestrial origin. 



The solar origin of meteorites has been seriously 

 urged, and deserves a serious answer. The first 

 difficulty which this hypothesis meets, is that solid 

 bodies should come from the hot sun. Besides 

 this, they must have passed without destruction 

 through an atmosphere of immense thickness. 

 Then there is a geometric difficulty. The meteor- 

 ite shot out from the sun would travel, under the 

 law of gravitation, nearly in a straight line out 

 and back again into the sun. If in its course it 

 enters the earth's atmosphere, its relative motion, 

 that which we see, should be in a line parallel to 

 the ecliptic, except as slightly modified by the 

 earth's attraction. A large number of these 

 meteors, that is, most if not all well-observed fire- 

 balls, have certainly not travelled in such paths. 

 These did not come from the sun. 



It has been a favorite hypothesis that the mete- 

 orites came from some planet broken in pieces by 

 an internal catastrophe. There is much which 

 mineralogists can say in favor of such a view. 

 The studies of M. Stanislas Meunier, and others, 

 into the structure of meteorites, have brought out 

 many facts which make this hypothesis plausible. 

 It requires, however, that the stone-meteor be not 



