LXI\' THE ROYAL SOCIETY OF CANADA 



spectrograph it was found that, by the use of arcs in heHum under 

 30 cm. pressure, illumination could be maintained continuously for 

 hours, and with such arcs spectra could easily be obtained extending 

 to below 1,000 A.U. 



Although it is known that free electrons can exist in highly 

 purified helium to an amount easily measurable it was found that 

 pure helium, under a pressure of more than 80 atmospheres, did not 

 exhibit anything in the nature of metallic conduction. Moreover, 

 the mobilities of both positive and negative ions formed by a-rays 

 in helium under this high pressure were found to have about one-third 

 the value expected on the basis of an inverse pressure law. 



The Uses of Helium • 



The investigation into the problem of producing helium in large 

 quantities was originally undertaken with a view to the utilization 

 of the gas in aeronautical warfare. The investigation showed that 

 it could be produced at a cost which is not excessive, but it had also 

 been shown that from the sources in the Empire, which are known 

 and have been examined, the supply of helium cannot be greater than 

 about 12,000,000 cubic feet per year. This quantity clearly would 

 be sufficient to keep only a very few of our airships of the larger 

 type in commission, even if the gas were diluted to the extent of 

 15 per cent, with hydrogen. This amount would, however, suffice to 

 keep a number of the smaller aircraft supplied. Moreover, it might 

 be used to fill fireproof compartments adjacent to the engines if it 

 were ever decided to instal these within the envelopes of our larger 

 airships. 



Since it has been demonstrated that helium could be produced in 

 quantity, one was led naturally to consider in what directions one 

 could hope to use the gas other than that originally intended. In 

 industry it may be used as a filling for thermionic amplifying va'lves 

 of the ionization type. It may also be used for filling tungsten 

 incandescent filament lamps, especially for signalling purposes where 

 rapid dimming is an essential, and for producing gas arc lamps in 

 which tungsten terminals are used, as in the "Pointolite" type. 

 Both of these varieties of lamps possess the defect, however, of soon 

 becoming dull owing to the ease with which incandescent tungsten 

 volatilizes in helium, and deposits on the surface of the enclosing 

 glass bulbs. As regards illumination, helium arc lamps possess an 

 advantage over mercury arc lamps in that the radiation emitted has 

 strong intensities in the red and yellow portion of the spectrum. 



