328 Bumstead and Wheeler — Radio-active Gas. 



Art. XXXIII. — Note on a Radio-active Gas in Surface Water; 

 by H. A. Bumstead and L. P. Wheeler. 



During the visit of Prof. J. J. Tliomson to New Haven 

 last spring, he called the attention of the writers to the work 

 done in the Cavendish Laboratory on a radio-active gas found 

 in waters coming from deep levels. At his request we under- 

 took to ascertain if a similar gas existed in the deep level 

 waters of this locality. For this purpose water from a spring 

 near J^ew Milford, Conn, of an estimated depth of 1500 feet 

 was obtained, the gas driven off by boiling and tested in an 

 electroscope. The normal air leak was found to be increased 

 about three times. The gas was very much diluted owing to 

 air spaces in the boiling apparatus, so that the leak found does 

 not represent the real activity of the gas as it comes from the 

 water. In the meanwhile the water from one of the ISTew Haven 

 city reservoirs (an artificial lake fed entirely by surface drainage) 

 was tested and found, somewhat to our surprise, to contain a 

 strongly active gas. From 7' 5 liters of this water about 175^^^ 

 of gas were obtained and this introduced into a Wilson elec- 

 troscope of about 380^^ capacity increased the normal air leak 

 about twelve times. The result was the same whether the 

 water came through the city supply pipes or was obtained 

 directly from the lake. Water, from which the gas had been 

 expelled and which was aerated by droj)ping, had not recovered 

 the power of giving off a radio-active gas after sixteen days. 

 This would indicate that the gas is not an emanation from any 

 radio-active substance dissolved in the water ; and this is further 

 evidenced by the fact that the residue from tlie water is very 

 slightly, if at all, active. 



In casting about for an explanation of the presence of an 

 active gas in surface water, where none had been found in 

 England, we were led to test the gas drawn from the ground 

 (about five feet deep), which proved to be approximately three 

 times as radio-active as the gas from the surface water. The 

 rate of decay of the activity of both gases was measured by 

 enclosing a sample of each in a gas-tight electroscope and tak- 

 ing readings twice daily for two weeks. The curves obtained 

 are identical within the limits of accuracy of the measure- 

 ments, and show an initial rise of activity lasting four or five 

 hours and a subsequent falling off which follows fairly well 

 an exponential curve. The activity falls to half its value in a 

 time very close to four days. After the gas is blown out the 

 excited radio-activity on the walls of the electroscope can be 

 detected for about two hours. In these respects these gases 

 follow closely the behavior of the emanation from radium as 

 determined by Rutherford and Curie. Further investigation 

 of the properties of the gases is in progress. 



Sheffield Scientific School of Yale University, 

 New Haven, Conn,, Sept. IG, 1903. 



