Internal-combustion engine

Instead of using steam to move a piston, what if flammable vapor and air could explode within a cylinder to move the piston instead? Although still too inefficient to be practical, this engine powered small vehicles and represented a significant step in the evolution of modern transportation.
 Jean-Joseph-Étienne Lenoir France 1860 Internal-combustion engine

Instead of using steam to move a piston, what if flammable vapor and air could explode within a cylinder to move the piston instead? Although still too inefficient to be practical, this engine powered small vehicles and represented a significant step in the evolution of modern transportation.