240 Quirke and Finkelstein — Badioactivity of Meteorites. 



drawn out to fragile tips were broken, and air allowed to bub- 

 ble through the solution, and pass into the electroscope. The 

 activity rapidly increases and reaches a maximum after three 

 hom's. This is due to the accumulation of RaA, RaB, and KaC. 

 The rate of discharge was measured w^hen the maximum 

 had been reached, that is after an interval of three hours. 

 During this time the leaf was kept charged. The leak was 

 measured in exactly the same way as in the case of the natural 

 leak. 



Estimation of Radium in the Sample 



The natural leak was determined before each measurement. 

 The tube containing the fused material which had been sealed 

 for a period of thirty days was inserted in the air line. The 

 tips at the ends of the tube were broken off, and the tube 

 heated. When the material had liquefied, air was allowed to 

 bubble through into the electroscope. 



After the electroscope was filled, the time of discharge after 

 an interval of three hours was measured in the same manner 

 as the standard. The amount of radium in the sample was 

 evaluated from : 



Anit. of Ra =. H^! X S. 



\vhere : f, = time of discharge of standard. (Eqnilib. amt. Ra) 

 tf = " " " " unknown. ( " " '' ) 



As = natural leak of standard. 

 Af zz: " " " unknown. 



S = amount of radium in standard. 



The results show that the radioactivity of stony meteorites 

 varies considerably. The meteorite, Juvinas, contains 2'17X 

 10"'" gm of radium element to a gram of meteorite, and the 

 meteorite, Farmington, contains only 7*34 X 10""'* gm of radium 

 element to a gram of meteorite. Including the determination 

 for the radioactivity of Dhurmsala made by Strutt, seventeen 

 stony meteorites have an average radioactivity of 7'61 X 10"'" gm 

 of radium to a gram of meteorite. Excluding Dhurmsala, six- 

 teen meteorites have an average radioactivity of 7'39xlO''' gm 

 of radium to a gram of meteorite. Two iron-stone meteorites, 

 Estherville and Liana del Inca, have an average radioactivity 

 equivalent to 6*88xl0"''gm of radium to a gram of meteoritic 

 material. Five of the seven iron meteorites examined are non- 

 radioactive, so far as can be determined, i.e., they do not ex- 

 ceed 10"^* grams of radium per gram of meteorite. The other 

 tw^o iron meteorites, Toluca, and Coahuila, seem to be radio- 

 active ; Toluca decidedly so, and Coahuila so feebly radioactive 



