76 THE ROYAL SOCIETY OF CANADA 



TABLE I. 



Nitrogen, Smaller Bulb. 



l']It>ctrometcr Needle: — 147 volts. Field: — 14-1 volts. P.D. over lamp: 3-5 volts. 



Note : — Readings of the deflection with no light were taken as follows : — 



2^52 P.M 599 -0168 



3-20 " 61^3 -0163 



4^10 " 656 -0152 



From this data the corrections given above, in Column 6, were calculated. 



Column 1 gives the time at which the reading was taken. 

 Column 2, the pressure of the gas in the bulb. Column 3, the 

 current in amperes through the wire. Column 4, the observed 

 time of deflection of the electrometer over a fixed interval on the scale. 

 Column 5, the reciprocal of this time. Column 6, the correction, as 

 explained above, and Column 7, the resultant net rate. The relation 

 between pressure and net rate of deflection is shown in the accompany- 

 ing graph in Fig. 5. In the same figure is also shown the correspond- 

 ing curve for total energ}^ expended, as ol:)tained from the current 

 readings recorded above. The difference of potential between the 

 ends of the wire was, it will be remembered, kept constant. The 

 scale is an arbitrary one. 



IV. Conclusions. 



It will be noticed that the general type of curve is the same for 

 all the gases used — air, nitrogen, and h\'drogen; and also that the 

 curves for air in the larger and smaller bulbs are of the same type. 

 This type is that to be expected from the considerations outlined in 

 a preceding paragraph. 



A comparison of the conductivities for heat of the gases, hydrogen 

 and air, for example, may readily be obtained by measuring the photo- 

 electric currents, at atmospheric pressure, under similar conditions 



