# Page:Popular Science Monthly Volume 90.djvu/722

706 Popular Science Monthly

of the air manifests itself more and more as speed is increased, so that each additional mile-an-hour of speed is purchased at additional waste of energy. Gravitation is constant. It pulls a moving object down to the earth, and sooner or later stops it.

### How You Can Travel for Nothing

It is apparent that if we are to attain and maintain anything like the speed of a bullet we must remove the air and we must neutralize the attraction of gravitation, since it cannot be destroyed. If this is attained you need not expend energy to maintain the value of the velocity of the car — the principal waste of energy in all usual systems of locomotion — and you could travel indefinitely for nothing.

A consideration of the subject led me to conduct laboratory experiments which show that it is possible to move a car at high speed in a tube from which the air has been partially exhausted — thus overcoming the obstacle opposed by air resistance — and to support that car, not on the usual rails but literally in space by means of electromagnets — thus neutralizing gravitation.

In these laboratory experiments I used a copper tube ten inches in diameter curved so that it returned into itself. The straight portion was wrapped with a long coil of insulated wire divided into sections to constitute as many solenoids — electromagnets without iron cores. By manipulating a system of switches I could send the current through these solenoids in rapid succession. The "car" was an iron cylinder running on wheels. It was magnetically sucked into the influence of the first solenoid, then into the next and in this way successively passed from one coil to the next. When the car had attained a velocity of four miles an hour in my experiments and was passing out of the influence of the last solenoid the current began to flow through the first. All the solenoids were placed on top of the copper tube and served to raise the car from the bottom of the tube. When this current was too weak the car would jump just slightly from the bottom of the tube; when it was too powerful the car would actually scrape the top of the tube and run touching, not the bottom but the "ceiling" of the tube; and when the current was of just the proper strength the car rose from the ground without touching the top wall and sped on to another electromagnet which, in the same way, kept it thus suspended in space. Every electromagnet was energized only during the time that the front of the car began to approach it and until the rear of the car had passed it. In this way the electromagnet merely lifted the car but did not change its velocity at all. The tube was connected with an air pump so that the air could be practically exhausted.

In his laboratory experiments, Prof. Weinberg used a copper tube ten inches in diameter, curved so that it returned into itself. The "car" is shown here — an iron cylinder running on wheels

### You Are the Only Passenger in the Car

In imagining this principle applied, I must ask my readers to divorce themselves from all current conceptions of railways. The car of the vacuum electric system would be a three hundred pound iron cylinder three feet in diameter, with conical ends hermetically sealed. You enter that car and lie prone in it, its solitary passenger. The sustaining electromagnets are much bigger than those used in my experiments shown in the photographs, and they are spaced thirty feet apart and are successively fed with a powerful current for a fraction of a second.

The direction of motion of such a highspeed car cannot be easily changed. Imagine the difficulty of swerving a fifteen-inch projectile as it leaves the mouth of a naval gun! Like any railway the vacuum tube would have its curves. How are they to be rounded? I again utilize electromagnets. The distance between these electro-