494 HARVARD LAW REVIEW, the operation of the weaker current, but the chief conflict is that which has arisen between the telephone lines and the single trolley- electric railway, and this article will be limited to the investiga- tion of the respective rights of these two classes of lines in the highways. The main features of the construction of telephone lines and electric railway lines are now familiar to every one, but there is one point which may not be wholly understood, and which is im- portant in the following discussion. The telephone line in its original form of construction — and the same form is in use at the present time in many places — does not contain a complete metallic circuit, by which the current can start from the speaking tele- phone or transmitter, travel to the hearing telephone or receiver, and then return to the speaking telephone, but the wire, after reaching the hearing telephone, is led to some adjacent gas or water pipe in the building, or other convenient conductor, over which the current can pass into the ground. It is evident that this connection with the ground through the gas pipe or other conductor forms an economical mode of construction, but it has an objection, — that it furnishes a suitable means for a stronger electric current to travel up the conductor into the hearing tele- phone, just as it does for the telephone current to travel down the conductor into the earth. Hence comes the difficulty with the electric railways, for the electric railway, built according to the single trolley system, uses in a similar way the ground for the return current; that is, the dynamo at the power station generates the electric current which flows out over the trolley wire, thence into the trolley on the car, and by a wire in the trolley pole down through the controllers into the motor in the car, and thence by the car axle and wheels and rails into the ground. The injury which the electric railway current does to the use of telephones is of two kinds: — I. Conduction, as it is technically called, or leakage. The com- paratively strong current of the trolley car, after escaping into the ground, finds an easy path along the gas or water pipes in the street, and into private premises, until it reaches the point at which the telephone wire is attached, thence up the wire into the tele- phone and through it, to the central exchange. This passage of the railway current into the telephones produces buzzing and crack- ing noises in the telephones, confuses the sound of the voices, and renders the conversation unintelligible. It also rings the call bells
