454 



TABLE I. 



Radioactivity of Noted Springs, Etc. 



Kings well, Bath, Eng 173. X10- 12 Gm. Ra. per liter. 



Brembaeh (Saxe.) 36000. to 720000. X10-" Curies per liter. 



Schweizergang, Joachimsthal 98000. 



Lake Balaton, Hungary 10300. to 36000. 



Potable waters of Mulhause (Alsace) 2800. 



Evaux-Ies-Bains 1060. to 2340. 



Evaux-les-Bains gas 3440. to 80090. 



Japanese hot springs 237. to 13800. 



Colorado Springs, Manitou 120. to 4730. 



Colorado Springs, Manitou, gas 470. to 20500. 



West Canada, Fairmount, Sinclair 3500. to 4000. 



Yellowstone Park 2.26 to 10.4 Mache units. 



Yellowstone Park gas 6.25 to 118.3 Mache units 



Sixty Springs, Tyrol 06 to 89. Mache units. 



Saratoga, N. Y., springs 39. to 880. X10" 12 Curies per liter. 



Saratoga, N. Y., springs gas, Max 847. 



Williamstown, Mass 13. to 216. 



Williamstown, Mass., gas 759. to 7290. 



Caledonian Springs, near Ottawa, Can 15 . 



St. Lawrence River .25 to 1.1 



Sea water .9 



Air, Montreal, Cambridge, etc .1 



One Mache unit equals 364. X10 l - (Curies per liter). 



The radioactivity of water may be due to traces of radium salts dis- 

 solved in the water. It may be due to some other product of the uranium- 

 radium series, to radium emanation, usually, or to some product of the tho- 

 rium or actinium series. The greater amount is usually due to radium or 

 radium emanation dissolved in the water. 



In the uranium-radium series (Table No. 2), it will be noted that when 

 one substance changes into another a radiation of a, £, or v rays, in some 

 cases all three, are given off. This radiation ionizes the air and renders it 

 conducting. The conductivity of the air becomes a measure of the radio- 

 activity of the substance. This is proportional to the rate which a charged 

 body loses its charge. 



The ionization produced by the three sets of rays is about in the fol- 

 lowing proportions: a = 100%, p = 1.%, y = .01%. The penetrating powers 

 are in the inverse proportion. Electroscopes for radioactive measurements 

 are known as a ray electroscopes, $ ray electroscopes, y ray electroscopes 

 according to the amount of material that must be penetrated by the radia- 

 tion in order to get into the electroscope. Thus in an a ray electroscope 

 the substance tested is placed in the electroscope or very near to a window 

 covered with a very thin sheet of aluminum or paper. The rays pass in 



