534 Dr. W. H. Eccles on the Energy Relations of 



Society in March last (Phil. Mag. June 1910). The present 

 experiments were for the most pnrt carried out at an earlier 

 date than those described in that paper. The properties of 

 the detectors are examined in three distinct ways. The first 

 way consists in applying to the detector an electromotive 

 force which is gradually increased, and measuring the con- 

 sequent current at each step. The second way is to fix the 

 electromotive force at some particular value, to send trains 

 of oscillations of various energy values through the instru- 

 ment, and to measure the intensity of sound produced in the 

 telephone on each occasion. The third way is to send trains 

 of constant energy value through the instrument while the 

 steady electromotive force applied to it is varied in steps, 

 and to measure at each step the intensity of the sound pro- 

 duced in the telephone. These modes of experimenting give 

 curves ihat may be called respectively the steady-current 

 curve, the power curve, and the sensitiveness curve. It will 

 be seen from the curves that the power supplied to the de- 

 tector in the form of electrical oscillations and the power 

 handed to the telephone in the form of intermittent current 

 are both recorded in fractions of a watt. For this purpose, 

 the circuit-calibrations described in the former paper were 

 used. It must be mentioned here that the calibration of the 

 telephone circuit is probably much less accurate than that of 

 the detector circuit. 



Results or the Measurements. 

 The Electrolytic Detector. 



This detector consisted of two platinum electrodes in dilute 

 sulphuric acid (one of acid to four of water). One electrode 

 was a platinum wire of 0*0006 cm. diameter drawn by the 

 Wollaston process, dipping a fraction of a millimetre into 

 the electrolyte ; the other was a piece of thick wire well 

 immersed. When a potential difference less than one volt is 

 established between the electrodes the current that passes 

 is very small ; but as the potential difference is increased the 

 counter electromotive force of polarization is overcome, till 

 finally a large current flows with evolution of gas. The 

 stage of the process which is useful for detecting feeble 

 electrical oscillations is that where the bubbles of gas do not 

 yet form on and break away from the point freely. The 

 steady current curves of fig. 1 (PI. X.) indicate the difference 

 between the two cases, point as anode and point as cathode. 

 The power curves for various cases are collected in fig. 2, all 

 from the same detector. Curve a shows the relation between 



