128 Boltwood — Radio-active Waters, Hot Springs, Ark. 



Art. XYTI. — On the Radio-active Properties of the Waters 

 of the Springs on the Hot Springs Reservation, Hot Springs, 

 Ark. / by Bertram B. Boltwood." 



The Hot Springs Reservation is situated in Garland County, 

 Ark., on the western slope of the Hot Springs Mountain, a 

 spur of the Ozark Range. On the grounds of the Reservation 

 the thermal waters rise through over fifty separate sources, and 

 the total flow is estimated to be over 800,000 gallons in twenty- 

 four hours. 



Daring the summer of 1904, at the direction of the Secre- 

 tary of the Interior, a thorough examination of the waters 

 of these springs for radio-active properties was carried out by 

 the writer. Samples of the waters were collected at the 

 springs, some in July by Dr. Joseph H. Pratt, and the remain- 

 der in August by Mr. Martin A. Eisele, Superintendent of 

 the Reservation. The samples were taken directly from the 

 springs and were immediately introduced into large, glass 

 receptacles. These receptacles were tightly corked and the 

 corks were covered with a heavy coating of hot sealing-wax, 

 thus hermetically sealing up the sample contained within them. 

 The samples were shipped by express to New Haven, Conn., 

 where the tests described in this paper were conducted. The 

 samples were collected and shipped in separate lots of six each, 

 and the tests were carried out as soon after the receipt of the 

 samples as possible. The average time required for the trans- 

 portation of the samples by the express companies was about 

 seven days. 



The constituents tested for were radio-active gas (emanation) 

 and radio-active solids. An examination was also made of the 

 tufa deposited by certain of the springs in order to determine 

 whether this contained any radio-active substances. 



The methods employed in the determination of the radio- 

 active gas contained in the water, and in the determination of 

 the presence of radium salts in solution, have already been 

 describedf in an earlier paper. The plan there followed of 

 expressing the activity of the dissolved radium emanation in 

 terms of the uranium equivalent has been modified to the 

 extent of introducing a correction for the proportion of radium 

 emanation lost by the pulverized sample of uranium mineral 

 used for determining the standard.^ Since the quantity of 



* Published with the permission of the Secretary of the Interior. 



+ This Journal, xviii, 378, 1904. 



X A method for determining the proportion of emanation which spontane- 

 ously escapes from the cold, finely-ground mineral has been described in the 

 Phil. Mag. (6), ix, 599. 



