110 



sisted of a piece of platinum foil of several square c. m. area, coated with 

 lead peroxide. Thus the two areas were vastly different; and nearly the 

 whole of the polarization occurred at the point electrode, which was used 

 successively as anode and as kathode. 



When used as anode the current-potential curves showed the bend at 

 about 0.4 volt. But used as Ivathode, the several curves were not in as 

 good mutual agreement, and do not clearly indicate a particular voltage 

 at which action at that electrode begins. The general indications are 

 that the lead appears at a voltage considerably less than that required 

 to separate lead on a platinum liathode, and that the peroxide is reduced. 

 The irregularities that may masli the critical voltage seem to be due to 

 local concentration changes around the electrode. 



PbO, seemed to form at the anode at the voltage 0.4. 



Some Observations with Rayleigh's Alternate Current 



Phasemeter. 



By E. S. Johonnott, Jr. 



This instrument in tlie field of alternate current measurements takes 

 a place similar to that of the galvanometer in direct current measure- 

 ments; with some advantages, and also with some disadvantages. For 

 example, its indications may represent either current or electromotive 

 force, and the angle of lag and true watts in a circuit may be obtained 

 by a simple calculation. However, its indications, as in all other alternate 

 current meters, vary as the square of the current; hence its range of 

 sensibility is limited. 



The principal feature of the instrument is the ease witli which it 

 gives the angle of lag of the current in a circuit behind the electromotive 

 force impressed at its terminals. Also when once calibrated it gives all 

 the quantities needed to determine the energy absorbed in a conductor. 



Similar to the tangent galvanometer it consists of an iron magnet 

 suspended in the field of the current whose value is required. 



Fig. I is a horizontal sectional view of the form used by Lord Rayleigh. 

 M represents the current coil, and is connected in series with the con- 

 ductor on which the measurements are desired to be made. S represents 

 the E.M.F. coil and is shimted across the terminals of the conductor. 



