242 Quirlte and FinheXstein — Radioactivity of Meteorites. 



that its activity may be due to local siliceous inclusions. How- 

 ever, Strutt found much greater activity in the native iron of 

 Greenland, and it may be that radioactivity is not foreign to 

 many of the so-called iron meteorites. It is clear, nevertheless, 

 that most of the iron meteorites are free of radioactivity, and 

 the siliceous meteorites are all radioactive, so far as known. 



Summary 



1. A method for the estimation of radium in rocks and 

 meteorites has been described. 



2. The radium content of twenty-two meteorites not here- 

 tofore analyzed has been determined. 



3. From the data it appears that the average stony meteor- 

 ite is considerably less radioactive than the average igneous 

 rock, p]'obably less than one-fourth as radioactive as an aver- 

 age granite, and that the metallic meteorites are almost free of 

 radioactivity. 



The authors are indebted to Professor Herbert N. McCoy, 

 under whose direction this work was carried out, and to Dr. 

 Farrington and the Field Museum autliorities for the use of 

 authentic meteoritic material. 



Kent Chemical Laboratory, University of Cliicago. 



