318 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1916. 



retrogrades. From, the calculation of the time of the nodes of 

 intersection and comparison with observations Tschermak was 

 able years ago to predict the next falling of a eukrite for about the 

 end of October, which calculation was actually borne out by the 

 falling of the eukrite of Peramiho on the 20th of October, 1899. 



For the four undoubtedly similar eukrites of Stannern, Jonzac, 

 Juvinas, and Peramiho, the retardation of the intersection was 

 found proportional to the time by the formula (E=longitude of 

 node) E=230.64-|-1.6175t, in which t denotes the number of the 

 year minus 1800. 



The greatest difference between the observations and the calcu- 

 lation is not more than one and one-half days. From the deter- 

 mined return and the regular shifting of the lines of nodes, which 

 yearly corresponds to a change of 1° 36', there is therefore very 

 great probability for the astronomic connection of the eukrites. 



Although V. Niessl did not find the astronomic courses of the;^ 

 eukrites to be identical, which means that they did not indicate the 

 same point of origin, still one can always consider as open the pos^- 

 bility that the Stannern, Jonzac, and Juvinas stones came from the 

 same region in space, when one considers that the testimony of eye- 

 witnesses as to the course of fireballs is subject to great error because 

 of the suddenness of the occurrence. 



According to v. Niessl^ the meteorite falls move in hyperbolic 

 courses, which, however, does not shut out the possibility that 

 meteorites occur which move in elliptical courses like planets. Firm 

 support also for this meteoric hypothesis, deduced from indisputable 

 facts, comes from astronomic consideration. More recent observa- 

 tions have shown that there is a difference in Idnd between the mate- 

 rial of meteorites and shooting-stars. If one arranges the meteorites 

 according to their specific weight, a series results, which begins with 

 the carbonaceous forms, of the density 1.7 to 2.9. Then follow those 

 bearing feldspar with the density 3 to 3.4, those containing bronzite 

 and olivine (mostly chondrites) with the density 4 to 7, and finally 

 the irons of the density 7.5 to 7.8. 



Carbonaceous meteorites 1.7-2.9 



Feldspar-bearing meteorites 3.0-3.4 



Bronzite-olivine-bearing stones (mostly chondrites) 4.0-7.0 



Iron 7.5-7.8 



In the face of the lesser densities, which are found in the moon 

 (3.4) in comparison with the earth (5.6), and which decrease in the 



1 Determination of Meteor Orl>its : Smithsonian Miscellaneous Collectiona, Vol. 66, No. 

 16, 1917. — Translator. 



