Velocity of the Electric Current. 171 



Armature Time. 

 The armature time depends on the following conditions : 



1. Strength of Battery. 



2. Tension of Spring. 



3. Distance of Armature. 



4. Motion of Armature. 



5. Permanent Magnetism. 



In order to eliminate as much as possible the source of 

 error arising from variations of armature time, 2, 3, and 

 4, are reduced to a minimum. More especially is this 

 necessary for (4), the motion of the armature. In our 

 final experiments, the play of relay armature was reduced 

 to one or two-thousandths of an inch. 



When (5) is zero (which is the case with a local circuit 

 or short line), and (2), (3) and (4)' are reduced to a mini- 

 mum, the strength of the battery does not essentially 

 change the armature time. 



In working over a long line of telegraph wire, the 

 escape is always considerable ; consequently, in order to 

 work from both ends of the circuit without change of ad- 

 justment, 3 cannot be reduced to a minimum, but will 

 depend on the amount of escape, and the strength of the 

 battery. 



In our experiments, the armature time of relay, plus 

 recording pen No. 2, was determined for each separate 

 adjustment. 



Circuits. 



The circuits were made up by Mr. C. S. Jones manager 

 of the Albany office by looping together wires leading to 

 Buffalo, N. Y., Boston, etc., until a sufficient length of 

 circuit was secured. The connections at those points were 



