110 THE ROYAL SOCIETY OF CANADA 



detected. In an attempt to see how much of the final residual ionisa- 

 tion was traceable to this cause a cylinder of ice was prepared from 

 distilled water obtained from the Chemical Laboratory of the Univer- 

 sity of Toronto, through the kindness of the Director and those as- 

 sociated with him. Readings 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 1 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 radio-active 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 radio-active impur- 

 ities. 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 de- 

 scribed 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 con- 

 ductivity of air confined in a vessel of ice when measured on the surface 

 of a large body of 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. 



1. 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 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 water of 

 Lake Ontario the conductivity of air when measured on the surface 

 of that lake has been found to be represented by 2 • 6 ions per c.c. 

 per second which is the lowest conductivity hitherto observed for air. 



4. Reasons have been adduced which support the view that air 

 has no electrical conductivity apart from that impressed upon it by 



