I. "We could even have an electric gun. Conceive a bobbin wound with insulated wire in lieu of thread, and having the usual hole through the axis of the frame. If a current of electricity be sent through the wire, the bobbin will become a hollow magnet or 'solenoid,' and a plug of soft iron placed at one end will be sucked into the hole. In this experiment we have the germ of a solenoid cannon. The bobbin stands for the gun-barrel, the plug for the bullet-car, and the magnetism for the ejecting force. We can arrange the wire and current so as to draw the plug or car right through the hole or barrel, and if we have a series of solenoids end to end in one straight line, we can switch the current through each in succession, and send the projectile with gathering velocity through the interior of them all. In practice the barrel would consist of a long straight tube, wide and strong enough to contain the bullet-car without flexure, and begirt with giant solenoids at intervals. Each of the solenoids would be excited by a powerful current, one after the other, so as to urge the projectile with accelerating speed along the tube, and launch it into the vast."