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XLVI. The Variation of the Radioactivity of the Hot Springs 

 at Tuwa. By A. Steichen, S.J., Ph.D., Professor of 

 Physics, St.Xaviers College, Bombay*. 



IN his interesting paper contributed to this Journal f , 

 Professor R. R. Ramsey gives two instances o£ the 

 variation of the emanation-content of springs. He finds 

 the greater radioactivity at the time when the springs are 

 yielding the greater amount of water. My experience 

 with a highly radioactive spring here in India is just the 

 opposite. 



Tuwa is a village in the Kaira District, Bombay Presi- 

 dency, 319 miles north of Bombay. The geographical 

 coordinates of the place are lat. 22° 43', long. 73° 30'. 

 Not far from the railway-station at Tuwa there is a small 

 area, about 20 by 17 metres, where numerous hot and cold 

 springs issue from the ground. The highest temperature 

 of the springs which I measured is 67° C, the lowest 28 °C. 



On the 13th December, 1910, the Rev. H. Sierp and myself 

 measured the radioactivity of the hottest and of the coldest 

 springs +. The method of measurement was the Schmidt 

 shaking method ; the instrument used was a Wulf quartz- 

 fibre electroscope with an ionization-chamber. We applied 

 Daane's correction for the absorption of rays by the walls of 

 the cylindrical condenser § . The radioactivities are calculated 

 by means of Laborde's empirical values ||. All the measure- 

 ments were made at the springs. 



We obtained the following results : — 



Hot spring : 



Saturation current 82'1 Mache units (M.U.). 



Radioactivity 33*00 x 10" 9 curie (C.) . 



Cold spring : 



Saturation current 84'25 M.U. 



Radioactivity 33'88xl0" 9 C. 



On the 11th April, 1911, we visited the springs once 

 more, in order to ascertain whether the radioactivity of the 



* Communicated by the Author. 



t Phil. Mag. vol. xxx. pp. 815-818 (1915). 



1 Indian Medical Gazette, December 1911. 



§ Kohlrausch, Lehrbuch der Prakt. Physik, 11th ed. p. 657. 



|| Laborde in Handbuch der Radium- Bioloc/ie und Therapie, p. 41: 



Phil. Mag. S. 6. Vol. 31. No. 184. April 1916. 2 E 



