No. 504] PHYSIOLOGICAL EFFECTS OF RADIUM RAYS 773 



I have elsewhere 13 noted this, and have presented 14 a 

 mass of evidence from the realm of physical science indi- 

 cating the general distribution of radioactivity. It exists 

 in air and soil, in spring-water, and in freshly fallen rain 

 and snow. Potassium, one of the essential elements of 







A 



Experiv 

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lent 87. 











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Time of day 



plant food, has been found by Campbell to give off p 

 rays, 15 and some evidence has also been found that 

 calcium possesses the same property. The researches 

 of many investigators have clearly demonstrated the gen- 

 eral occurrence in nature of free negative electrons. 

 These discoveries not only add to the interest and im- 

 portance of the study of the physiological role of radium 

 rays, but also point out the way for further investigation. 



An arrangement devised by Mr. Hugo Lieber facili- 

 tated the study of the effect of a radioactive atmosphere 

 on germination and growth. The apparatus is clearly 

 shown in Fig. 13, and needs little further explanation, 

 except to say that the hollow cylinder, E, has its inner 

 surface coated with a Lieber 's radium coating. The 

 bell-jars fit tightly on to the ground glass plates, and a 

 current of air is kept passing through the jars by attach- 

 ing the tubing from the lower tubulure to an exhaust 

 pump. The air passing through the radium-lined cyl- 

 inder carried with it the emanation given off by the 



"Science, N. 8., 25: 263. 1907. 



