We now come to a consideration of conduit roads, their excellencies and their defects.

For years, electricians have worked to develop a practicable conduit system of electric railway, and many attempts have come near to success. The most extensive and, until recently, the most successful was the Bentley-Knight system. An immense amount of money was spent, the best talent was employed, and extensive lines were built at Cleveland and Allegheny City. Experiments were made in New York and Boston, and with the withdrawal from the field of the Bentley-Knight system, disappeared the last hope of our being able to place bare wires in a slotted conduit exposed to the severe conditions of our American climate. There is not a city in America to-day, where a bare conductor laid in a conduit can earn a dividend on the capital invested. No matter what the system may be, no matter how carefully the insulators may be protected, unless the conduit is made air-tight and water-tight (which, of course, no slotted conduit can be), mud and dirt will get into the conduit and settle on the conductors. Leakage takes place from a conductor in proportion to the length exposed, and glass, porcelain, ebonite or any other of the so-called insulators, when covered with dirt, conduct the current as well as a similar layer of dirt elsewhere would do. Over the path in this direction, Nature seems to have posted the warning, "No thoroughfare!"

Mr. F. L. Pope, in an article quoted by Carl Hering', says, in speaking of conduit experiments: "Hundreds of patents have "been taken out and more than a million dollars have been dis"bursed in paying for tuition in the costly school of experience. "More than once, and in more than one direction, success has at "times seemed almost certain; yet the truth compels me to say "that from the hard practical standpoint of dollars and cents, by "which every invention must first or last be tried, the net outcome "of all this vast expenditure of labor, time and money has, up to "the present moment, been almost insignificant. The reward "which awaits the fortunate person who succeeds in completely "solving this problem, may well be regarded as a potentiality of "wealth beyond the dreams of avarice. The problem of the un"derground circuit does not at first sight appear to be a very dif "ficult one. It renders necessary, in the first place, a construction "which will effectually resist the action of forces tending to dis"turb the condition of the wires, and with the heavy traffic on the "streets this involves a very strong structure. It is absolutely

1. Recent Progress in Electric Railways, pp. 168-170.

66 necessary that the conductors shall remain insulated from each "other and from the ground under all conditions of weather. The "exigencies of heavy rains and snows necessitate a construction "which shall permit of a thorough insulation of the conductors "and a drainage of the entire system. There are other minor "points which require to be taken into consideration. Without "going into details, it is sufficient to say that the conduit system. "has been tried on an extensive scale in Denver, Cleveland, and Boston, and to a lesser extent in several other places, but in "every case the continual interference consequent upon its use "has exhausted the patience of the traveling public and compelled "its abandonment."

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Mr. Mansfield, in the paper quoted above (also Hering, p. 170),

says:

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"In spite, however, of all this refinement and study, practically nothing has been accomplished; and I have no hesita"tion in saying that the continuous live conductor in an open "slotted conduit is to-day a failure, and that it cannot be made a success throughout our cities of to-day, its fatal weakness being "our inability to prevent the conduit from becoming filled with "water, mud, etc. The time may come when our sewerage sys"tems will be perfect enough to enable us to overcome this fatal "weakness. To-day, however, they are not, and even an opti"mistic view puts this time a long way distant.”

Mr. F. H. Monks, of Boston, says: "The conduit system has "been thoroughly tested, and has been shown to possess no com"mercial value for the propulsion of street cars to date." The standard work, "The Electric Railway in Theory and Practice, by Oscar T. Crosby and Louis Bell, Ph. D.," says, p. 255:

"The fundamental difficulty with all slotted-conduit electric "roads is the enormous difficulty of proper insulation. This "arises from the very nature of the case, for the conductors are "placed in a tube of limited diameter in free communication "with the open air through the slot. Water, dirt and mud in"evitably find their way in, and sooner or later the result has been "either a positive short-circuit at a single point, or general leak"age along the line in sufficient quantity to paralyze its oper"ation."

THE BENTLEY-KNIGHT SYSTEM.

We have already referred to this ill-fated method. They failed, but they made a noble fight. They had talent, experience and money, and they did thoroughly demonstrate that a conduit road using a bare wire cannot operate commercially in

our American cities. I do not say that it is impossible to find men who will still put their money into such systems, nor do I maintain that men cannot be found to spend shareholders' money in such experiments, but parties working in that direction can well learn from the sad experience of the investors in the BentleyKnight road. The laws of electricity have not changed since then; no great improvements have been made in insulating bare conductors; and, although I have examined a number of conduits with bare conductors, none of them have shown better construction, such expert technical skill, such regard for the laws of electricity, and none came nearer success. It is the same old story, too great expense and the impossibility of insulation.

In this system there is a conduit between the rails, provided with a slot, through which passes a brush for making contact with the bare wires laid in the conduit. They use a constant

FIG. 1.-Bentley-Knight, Truck Equipments, Conduit and Plow.

potential, about 500 volts being the normal voltage. The current strength is about 7.5 amperes, and the motor used will stand 60 amperes for half-an-hour. The electrical equipment is mounted on the truck, entirely independent of the car body, and the car is started and controlled precisely as the trolley car is. The cut Fig. 1 shows the essential features of their construction, and at the left is shown a diagram of the conduit and the "plow." The "contact plow" is shown in the next cut Fig. 2. "It consists "of a flat frame hung from the car by transverse guides, on "which it is free to slide the whole width of the car, and extend"ing thence down through the slot of the conduit. It is provided "with a swivel joint, so as to adjust itself to all inequalities of "road or conduit. The frame carries two flat insulated conduc"tor cores to the lower ends of which are attached, by a spring "hinge, smaly contact shoes of chilled cast-iron that slide along in "contact with the two main conductors. At the upper ends are

"attached flexible connections to prevent flashing at the contact." This road was worked in the winter time during the season of 1884-5.

The insulating support is "of vitreous material having support"ing pins sealed in it for connecting it to the conductor and to the "wall of the conduit inclosing the conductor, and having a flange "at its base for protecting the conductor from the moisture that "may accumulate upon it or the walls of the conduit. To pre"vent the water coming in through the slot from causing a leak "from the conductor to the metallic conduit, the insulator is pro"vided with a water-shed flange at its base, which is preferably "curved outward on the form of a saucer, though any suitably"shaped flange may be employed, and the insulator extends out

FIG. 2.-Contact Plow.

"horizontally from the conduit, so that the flange occupies an up"right position.' This is taken from U. S. Patent No. 455,339, of July 7, 1891, to Walter H. Knight, and further on in the same patent Mr. Knight sounds the key-note of the entire situation, and shows the rock upon which he and others using the same system have wrecked their barks. He says: "It has been found "that upon the insulators there is apt to be an excessive conden"sation of moisture, owing to the fact that the conduit is beneath "the surface of the street, and that at certain times an excessive "leakage is apt to occur at certain ones of the insulators," and he goes on to say: "This leakage has a tendency to correct itself, that is, the heat engendered by the passage of the leaking cur"rent dries up the moisture which has given rise to it."

True, but that is rather an expensive drying process. Electric energy costs money to produce, and it loses as its distance from the prime motor increases, and then to use it for keeping the streets of cities dry (for it really amounts to that) is hard on the coal pile and the anticipated dividends! The Bentley-Knight conduit system was the harbinger of better things. Splendidly constructed and well managed, but working on the wrong principle, it stands to the commercially practicable conduit road of the present and the future, in about the relation of the telephone of Philip Reis to the finished product of Professor Bell's genius.

Of the Love system, now working in Washington, I have not been able to get any accurate or reliable information, and I have heard no favorable reports thereon from impartial authorities. Their conduit is well built, their road is level, and their wires are protected in the same manner as failed to protect the BentleyKnight conductors. The details do not appear to have been worked out so completely as they were in the Bentley-Knight system. About Thanksgiving of last year I was in Chicago, and took occasion to visit and inspect the Love railway. It was not running at the time, had not been, I was informed, for a couple of months, and it was exceedingly doubtful when it would start