OF ARTS AND SCIENCES. 91 



The character of the results obtained will be seen by an inspection 

 of Figure 1, which gives the curve showing the relation between the 

 normal pressure and the resulting current, with electrodes of the ma- 

 terials employed in the Blake transmitter, viz. a platinum hammer 

 and a hard carbon anvil electrode. The abscissas represent the normal 

 pressures, i. e. the added weights, and the ordinates the currents pro- 

 duced in the secondary. The data from which this curve is constructed 

 will be found in the following table. The load is given in terms of 

 the arbitrary unit employed ; the currents are giveu in milliamperes. 



Table. 



The curve shows a rapid rise at first, as the mass of the anvil elec- 

 trode, and with it the pressure between the electrodes, is increased, 

 which rise soon reaches a maximum, the curve then falling off rapidly 

 at first, more slowly afterwards. 



The nature of the curve is interesting, and requires explanation. 

 In his article already referred to, Mr. G. W. Patterson, who obtained 

 similar results to my own, considers the curve to be composed of two 

 separate branches, the rising portion of the curve corresponding to a 

 motion of- the electrodes sufficient to break the circuit, and the falling 

 portion to the case Avhen the pressure is too great to allow this to 

 occur. The curve (these Proceedings, Vol. XXIII. p. 235, Fig. 4) 

 constructed upon this hypothesis greatly resembles one of the experi- 

 mental curves shown in Fig. 3 of the same paper. There is less 

 resemblance, however, to the lower curve in Fig. 3, and but little to 

 the curve shown in Ficr. 1 of this article, which was obtained under 

 exceptional conditions of quietness of the piers upon which the appa- 

 ratus was placed. The sound in a receiving telephone placed in the 

 secondary circuit 'is so harsh for this portion of the curve, that one 

 might well infer that actual breaks occurred ; but this is very doubtful, 

 and such breaking is certainly not essential to the production of the 



