THE AVERAGE SPECIFIC GRAVITY OF METEORITES. 



In order to determine for purposes of hypothesis the density 

 of a body formed by the aggregation of a multitude of meteorites, 

 it is desirable first to learn the average specific gravity of those 

 which have thus far fallen to the earth. 



The writer is aware of but one attempt, the results of 

 which have been published, to determine this quantity in a 

 general way. These results are given in a paper by Rev. E. Hill 

 in the Geological Magazine for 1885.^ From Flight's "Chap- 

 ters on Meteorites" this writer obtained the specific gravi- 

 ties of sixty-five different masses. The addition of these and 

 division by 65 gave 4.84 as an average specific gravity. As this 

 result took no account of the weights of the specimens, 

 however, a recalculation was made from those whose weights 

 and specific gravities were known, and an average of 5.71 obtained. 

 As this sum again, however, included the great Cranbourne 

 meteorite, whose weight of 31^ tons far exceeded that of all the 

 rest, all masses over 250 pounds in weight were excluded. From 

 the 52 cases thus averaged, a specific gravity of 4.58 was obtained. 



Another method of arriving at the desired result was based 

 on the ratio of metallic to stony meteorites, as they occur in the 

 British Museum collection. This ratio is 205 stony to 55 metallic 

 meteorites. Separating according to this ratio the 57 cases 

 referred to, an average specific gravity of 4.55 was obtained. 



R. P. Greg has also"" found the specific gravity of about 70 

 stony meteorites to be 3.4. He says, however, that " as those 

 possessing the smallest specific gravity are necessarily the most 

 destructible and fragile, and after meteoric explosion less likely 

 to arrive on the surface of the earth in an entire or tangible 

 :state, we may very fairly take their average density nearer the 



'New Series, Decade III, Vol. II, p. 516. 

 = London Phil. Mag., 4th Series, Vol. VIII, p. 337. 



126 



