130 OLIVER C. FARRINGTON 



As noted by Hill, however, an accurate result can only be 

 obtained by taking into account the weights of the specimens, 

 since a number of small weights of high or low specific gravity 

 would considerably raise or lower an average obtained from 

 individual specific gravities, while their effect on the density of a 

 mass made up of large weights of nearly uniform specific gravity 

 would be insignificant. 



Unfortunately, a calculation on this basis reduces somewhat 

 the number of cases from which an average can be drawn, since 

 in many of the cases where specific gravity is given, no record of 

 the weight of the meteorites can be obtained. By considerable 

 searching, however, I have been able to obtain records of 142 

 falls, the specific gravity and weights of which are known. These 

 include, fortunately, all but one of the metallic meteorites and 

 most of the larger falls, such as Weston, Juvenas, New Concord, 

 Estherville, Mocs, Alfianello and Winnebago county. By reduc- 

 ing these weights to the unit of water, adding and dividing, an 

 average of 3.69 is obtained for the whole, a result nearly in accord 

 with that deduced from the specific gravities alone. 



It is possible that from records of a larger number of falls, a 

 slightly different average might result, but it seems fair to assume 

 that the difference would not be more than .2 or .3 from the 

 figures given. Until further data are at hand, therefore, the value 

 of 3.69 may be regarded a fair one for the average specific gravity 

 of the meteoric matter which has come to the earth within the 

 period of intelligent human observation. 



To determine the probable density of a body formed by the 

 aggregation of such matter is not a part of the purpose of this 

 article, for this involves elaborate considerations of the effects 

 of pressure. The present investigation has at least shown how 

 desirable it is that those who in the future publish descriptions 

 of meteorites should take pains to determine the specific gravity 

 and weight of each fall. The accurate statement of these will be 

 of great service in further investigation. 



Oliver C. Farrington. 



