Ionization in Air enclosed in a vessel of Ice. 433 



cause, for it is known that although the water of Lake 

 Ontario contains very little radium, still traces of it in the 

 water have been detected. Li an attempt to see how much 

 of the final residual ionization was traceable to this cause, a 

 cylinder of ice was prepared from distilled water obtained 

 from the Chemical Laboratory of the University of Toronto, 

 through the kindness of the Director and those associated 

 with him. Bladings were made on the Bay upon the con- 

 ductivity of air enclosed in this receiver, and to our surprise, 

 the mean of the readings, as Table I. shows, was 5'5 ions 

 per c.c. per second. This it will be seen is larger, even, 

 than the value obtained with the tap-water ice cylinder on 

 the land, so that the high value must have been due to a 

 radioactive contamination of the distilled water from which 

 the cylinder was made. The still from which the water was 

 obtained is one of: large capacity, and it has been in use for 

 a number of years for furnishing the distilled water used in 

 the chemical laboratory. It is not surprising therefore that 

 the water contained radioactive impurities. It would have 

 been interesting to measure the conductivity of air contained 

 in a cylinder of ice made from water distilled with a newly 

 constructed still, but experiments such as those described in 

 this paper have to be done at Toronto within a period of two 

 or three weeks, commencing about the middle of February. 

 The experiments described in the paper represent all that it 

 was found possible to carry out during the past winter, and 

 though they may be extended at another time, enough has 

 been done to show that the residual conductivity of air con- 

 fined in a vessel of ice when measured on the surface of a 

 large body ot water such as Lake Ontario can probably be 

 entirely accounted for by radiations from traces of radio- 

 active material in the walls of the ice receiver and in the 

 ice and water of the Lake. 



IV. Summary of Results* 



3. The mean value found at land stations near Toronto for 

 the electrical conductivity of air confined in zinc vessels of 

 the highest available purity is represented by the generation 

 of 7*62 ions per c.c. per second. 



2. The mean value found for the conductivity of air 

 enclosed in the same zinc vessels has been shown to be 

 represented by the generation of about 4*5 ions per c.c. per 

 second when the experiments were made on the ice of 

 Toronto Bay, Lake Ontario. 



3. With air confined in a vessel of ice made from the 

 Phil Mag. S. 6. Vol. 30. No. 177. Sept. 1915. 2 F 



