On the Suppression of Induction Clamour in Telephones. 285 
Telephone. Fig. 7. Line, 
LEarth. 
The next plan tried was to raise a portion of the line wire to a 
bright incandescence, whilst enclosed within a conducting tube T 
joined to earth (Fig. 8). It is well known that when a conductor 
is at a bright white-heat “it is unable to retain a charge of 
either + or — electricity ; on cooling down, but while still of a 
red-heat, it acquires the power of receiving a — but not a + 
charge, and this distinction is maintained through a considerable 
range of temperature; at a lower temperature yet, but still at a 
dull red-heat, the conductor begins to be able to receive + electri- 
city, and shortly after, as it coils, it accepts both kinds with 
nearly equal readiness.”* Hence, I hoped, by raising the conduc- 
Fig. 8. 
Line 
Earth. 
Earth. 
* Guthrie’s Electricity, p. 81. 
