How a sail could pull a rail vehicle
A sail does not simply need to be pushed from behind: set at an angle, it catches moving air and turns some of its force into forward motion. On a rail vehicle, that pull reached the wheels through the frame, and the wheels rolled along the track instead of dragging over open ground. The rails supplied the part a sailboat’s water does not: a fixed route.
A fixed route was also a limitation
That guidance made steering simpler, but it did not make the vehicle independent of conditions. Its progress depended on having useful wind in relation to the track; a sail could not propel it straight into a headwind. Nor did rails eliminate the need to manage the sail or keep the vehicle stable. The wind supplied the power, while the track decided where that power could take the vehicle.
