EXPOSED WATER AND FRESHLY FALLEN RAIN 



173 



2. The Radioactive Influence of Freshly Fallen 

 Rain-Water 

 The fact that freshly fallen rain-water is radioactive suggested 

 the following experiments to ascertain its effect on growth. 



Experiment 52 

 May 28, 6 P. M. 



In a glass beaker, washed chemically clean, was caught rain- 

 water. The beaker was set in an open place to avoid drippings 

 from buildings and trees. It had been raining almost constantly dur- 

 ing the preceding day (2.26 in. precipitation), and slightly all the 

 morning of the twenty-eighth. Thus the atmosphere was thoroughly 

 washed, and the probability of traces of ammonia and COg and any 

 atmospheric dust in the rain-water was slight. No electrical disturb- 

 ance had accompanied the rain. 



20 

 Day of month 



Fig. 41. Effect on Growth of placing a sealed glass Tube of Radium of 10,000 

 activity into Water in which Roots of Luptnus albus are growing. 



Into the water thus collected were immersed, to a measured length 

 of 15 mm., the tap roots of four germinated seeds of Lufiniis albus. 

 Since rain-water is practically distilled, a control was similarly ar- 

 ranged with distilled water, also in a chemically clean beaker. 



The following observations were recorded of the amount of 

 elongation of the roots : 



