August 30, 1886.] 



8CIUWCU. 



171 



4. The members of each class have apparent 

 motions which imply common relations to the 

 horizon, to the ecliptic, and to the line of the 

 earth's motion. 



5. A cloudy train is sometimes left along the 

 track, both of the stone-meteor, and of the shoot- 

 ing-star. 



6. They have like varieties of colors, though in 

 small meteors they are naturally less intense and 

 are not so variously combined as in large ones. 



In short, if the bodies that produce the various 

 kinds of fire-balls had just the differences in size 

 and material v^rhich we find in meteorites, all the 

 differences in the appearances would be explained ; 

 while, on the other hand, a part of the likenesses 

 that characterize the flights point to something 

 common in the astronomical relations of the bodies 

 that produce them. 



This likeness of the several grades of luminous 

 meteors has not been admitted by all scientific 

 men. Especially it was not accepted by your late 

 president, Prof. J. Lawrence Smith, who by Ms 

 studies added so much to our knowledge of the 

 meteorites. The only objection, however, so far 

 as I know, that has been urged against the rela- 

 tionship of the meteorites and the star-shower 

 meteors, and the only objection which I have been 

 able to conceive of that has apparent force, is the 

 fact that no meteorites have been secured that are 

 known to have come from the star-showers. This 

 objection is plausible, and has been urged, both by 

 mineralogists and astronomers, as a perfect reply 

 to the argument for a common nature to all the 

 meteors. 



But what is its real strength ? There have been 

 in the last himdred years five or six star-showers 

 of considerable intensity. The objection assumes 

 that if the bodies then seen were like other meteors, 

 we should have reason to expect that among so 

 many hundreds of millions of individual flights a 

 large number of stones would have come to the 

 ground and have been picked up. 



Let us see how many such stones we ought to 

 expect. A reasonable estimate of the total num- 

 ber of meteors in all of these flve or six star- 

 showers combined makes it about equal to the 

 number of ordinary meteors which come into 

 the an- in six or eight months. Inasmuch as we 

 can only estimate the numbers seen in some of the 

 showers, let us suppose that the total number for 

 all the star-showers was equal to one year's supply 

 of ordinary meteors. Now the average annual 

 number of stone-meteors of known date from 

 which we have secured specimens has, during this 

 hundred years, been about two and a half. 



Let us assume, then, that the luminous meteors 

 are all of like origin and astronomical nature ; and 



further assume that the proportion of large ones, 

 and of those fltted to come entirely through the 

 au' without destruction, is the same among the 

 star-shower meteors as among the other meteors. 

 With these two assumptions, a hundred years of 

 expei'ience would then lead us to expect two, or 

 perhaps three, stone-falls from which we secure 

 specimens during all the half-dozen star-showers 

 put together. To ask for more than two or three 

 is to demand of star-shower meteors more than 

 other meteors give us. The failure to get these 

 two or three may have resulted from chance, or 

 from some peculiarity in the nature of the rocks 

 of Biela's and Tempel's comets. It is very slender 

 ground upon which to rest a denial of the common 

 nature of objects that are so similar in appearance 

 and behavior as the lai-ge and small meteors. 



It may be assumed, then, as reasonable that the 

 shooting-stars and the stone-meteors, together with 

 all the intermediate forms of fire-balls, are like 

 phenomena. What we know about the one may 

 with due caution be used to teach facts about the 

 other. From the mineral and physical nature of 

 the different meteorites, we may reason to the 

 shooting-stars, and from facts established about 

 the shooting-stars we may infer something about 

 the origin and history of the meteorites. Thus it 

 is reasonable to suppose that the shooting-stars are 

 made up of such matter and such varieties of mat- 

 ter as are found in meteorites. On the other hand, 

 since star-showers are surely related to comets, it 

 is reasonable to look for some relation of the 

 meteorites to the astronomical bodies and systems 

 of which the comets form a part. 



This common nature of the- stone-meteor and the 

 shooting-stars enables us to get some idea, indefi- 

 nite but yet of great value, about the masses of 

 the shooting-stars. Few meteoric stones weigh 

 more than one hundred pounds. The most pro- 

 ductive stone-falls have furnished only a few hun- 

 di-ed pounds each, though the irons are larger. 

 Allowing for fragments not found, and for por- 

 tions scattered in the air, such meteors may be re- 

 garded as weighing a ton, or it may be several 

 tons, on entering the air. The explosion of such 

 a meteor is heard a hundred mfles around, shak- 

 ing the au- and the houses over the whole region 

 like an earthquake. The size and brflliancy of the 

 flame of the ordinary shooting-star is so much less 

 than that of the stone-meteor that it is reasonable 

 to regard the ordinary meteoroid as weighing 

 pounds, or even ounces, ratlier than tons. 



Determinations of mass have been made by 

 measuring the hght and computing the energy 

 needed to produce the light. These are to be re- 

 garded as lower limits of size, because a large part 

 of the energy of the meteors is changed into heat 



