A VERAGE SPECIFIC GRA VI TV OF METEORITES 1 29 



be 25 to I, i. c, that 96 per cent, of all meteorites that fall con- 

 sist of stony matter. Hence it may be assumed that, for 

 34 iron masses, for example, found, 25 times as many or 850 

 stone falls have taken place.' The ratio deduced from the falls 

 of the last century would be somewhat higher than this, viz., 40 

 to I. There is, therefore, strong reason for belief that there is 

 normally a great excess of stone over iron falls. The alterna- 

 tive supposition, which has been urged by some, is that metallic 

 falls have been more abundant during earlier periods of the earth's 

 history than now, but there is no proof that these were not 

 accompanied b}' a similar proportion of stone falls to that which 

 now prevails. 



If it be granted that the desired average can best be obtained 

 from the observed falls of the past century, then again there 

 must be recoR-nized the fact that data for calculation on this basis 

 suffer serious limitations owing to the lack of records of the spe- 

 cific gravity and weight of many of the falls. The specific gravity, 

 so far as known, of most of the falls up to i860, can be found in 

 Buchner's catalogue,'' but since that time analysts have been 

 lamentably negligent in giving specific gravities in their published 

 descriptions of meteorites. In searching for weights of falls too, 

 one finds great scarcity of data, the records of earlier falls being 

 most at fault in this respect. But though the amount of data 

 obtainable is comparatively small, enough is at hand to permit 

 conclusions of value. 



Brezina's latest catalogue 3 gives 298 falls as having taken 

 place since the Wold Cottage fall of 1795. For 175, or more 

 than one-half of these, I have been able to find specific gravities 

 given in some one or more of the records. These range between 

 1.70 for Alais 10 7.84 for Cabin Creek, but by far the larger 

 number lie between 3 and 4 in specific gravity. The average 

 obtained from these 175 cases is 3.65. 



'There is evidently a clerical error in bis statement that 96 times as man)-, or 

 3624 stone falls may have taken place. 



^Die Meteoriten in Sammlungen, Dr. Otto Buchner, Leipzig, 1863. 



3Annalen der K. K. Naturhistorisches Hof Museum, Band X, Heft 3 und 4, 

 Vienna, 1896. 



