THE TERRESTRIAL DISTRIBUTION OF RADIUM 35 



Silica and alkalis are given in percentages. Radium is stated in units of 

 billionths (io~~ 12 ) of a gram per gram of material. For a useful collection of 

 analyses of meteorites, see Farrington, Field Columbian Museum Publications, 

 Chicago, Geological Series, vol. iii. nos. 5 and 9. For details of the classification 

 of meteorites, see Brezina, Proc. Am. Phil. Soc, vol. xliii. p. 211, 1904. 



* The composites were made up of the following groups of meteorites : 



(8) Stone Meteorites : [Radium averages C25 x io — I2 grams per gram.] 

 (a) Achondrites : Stannern, Nagy-Borove, and Bluff. 



{&) Chondrites : LAigle, Charsonville, Dhurmsala, Pultusk, and Knya- 

 hinya. 

 (4) Iron-Stone Meteorites : [Radium averages o'iox 10— Vi grams per gram.] 



Lithosiderites and Siderolites : Estherville, Pallas Iron, Vaca Muerta 

 and Dona Inez. 

 (3) Iron Meteorites : [No radium detectable.] 



Holosiderites : Youndegin, Staunton, and Toluca. 



unable to detect a measurable quantity. Native iron from 

 Disco, Greenland, contained o'2i x io -12 grams per gram, this 

 being probably associated with the silicate minerals also present 

 in the specimen. 



In their natural occurrence there would thus appear to be 

 a strong chemical antipathy between uranium and iron, and 

 it will now be clear that if the meteoritic analogy is true, or 

 if for any other reason it is believed that metallic iron is the 

 chief constituent of the earth's internal core, then there is 

 considerable evidence that the latter is entirely devoid of 

 uranium. It may be objected that if the stony material of 

 the earth were charged throughout with the same amount 

 of uranium (or radium) as is the stony material of meteorites, 

 there would still be an embarras des richesses, as regards the 

 thermal output of the whole. The analogy, however, must 

 not be pushed too far, and quantitative equivalence is not sug- 

 gested. It is impossible, for example, that meteorites (or 



