Investigation of the Simple Coherer, 



267 



touches cb (the point of exact touching is seen when the 

 galvanometer spot of light comes to rest on the scale). If 

 any adherence exists between the wires, it will be seen by the 

 spot not moving at once when the current is, very gradually, 

 decreased. 



Fig. 1. — A Diagram of the Aphometer. 

 A G 



By observing the current strength required to separate the 

 wires* when so adhering, we can obtain a measure of the 

 forces of adherence, under varying conditions of material, 

 current, &c. 



We have in this apparatus a means of applying, by a 

 simple adjustment of resistances, any small required force 

 whether tending to push the contact wires together or the 

 reverse. Dial pattern resistance-boxes were used so that 

 forces could be applied gradationally by the most easy steps. 



To save circumlocution I propose to call the whole apparatus 

 containing the two circuits an Aphometer (touch-measurer). 



* The work in the first nine sections of this paper refers to a copper- 

 copper contact. In sections 10 & 11 other metals and combinations are 

 used. 



T 2 



