524 FOOTE— FACTORS IN THE [April 25, 



always against the preservation of a fall in its entirety. For the 

 purpose of study, a broad slice or polished end piece is quite as 

 valuable as a large mass of iron. 



4. Group Weight. — Stony meteorites are classified in groups ac- 

 cording to their petrographic structure and composition ;, irons ac- 

 cording to their crystallization. Wiilfing gives this second position 

 among the factors of value. He calculates the total weight of each 

 group, giving to individual falls a value influenced by the group 

 weight. 



5. Observation of Fall. — This factor is placed eighth and last by 

 Wiilfing. His final exclusion of such a factor constitutes another 

 limitation of his formula, as may be seen by a comparison of actual 

 selling prices with his theoretical values. Of about 300 known 

 irons, only nine have been seen to fall. Comparing only these 

 siderites seen to fall and listed by Wiilfing, which have been re- 

 tailed: Agram, Charlotte, Braunau, Rowton, Mazapil, we find that 

 Wiilfing's theoretical value averages for these five falls 55 cents per 

 gram, whereas the last quoted selling prices averaged $4.71 per 

 gram, showing that sellers have rated irons seen to fall at more than 

 eight times the figures that Wiilfing accords them. 



Four siderolites seen to fall, Estherville, Lodran, Mincy and 

 Veramin, which are collated by Cohen at an average of $3.06, are 

 estimated by Wiilfing at an average of $4.42. This comparison is 

 quite inconclusive because of the uncertainty as to the location of a 

 large portion of the original weight of Lodran. As Wiilfing 

 estimates it by the present recorded weight, its value is enormously 

 inflated ($15.71), thus nullifying the results. Eliminating Lodran, 

 the remaining three are averaged by Wiilfing at $1.99 and by Cohen 

 at $6.61, showing that siderolites seen to fall are estimated by 

 Wiilfing at less than one third their market value. 



But when we examine the aerolites, we find that out of nearly 

 400 known stones, only about one twelfth have not been seen to fall. 

 The following ten aerolites not seen to fall, are the only ones quoted 

 by dealers and estimated by Wiilfing: Goalpara, Tomhannock Creek, 

 Waconda, Prairie Dog Creek, Long Island, Salt Lake City, Mc- 

 Kinney, Blufif, Pipe Creek and Alinas Geraes. The average of the 



